JP2024083239A - Image forming apparatus and process cartridge - Google Patents

Abstract

To reduce an adhesion force of toner to a photoconductor drum to improve transfer efficiency and prevent adhesion of toner to the other members in contact with the photoconductor drum in an image forming apparatus of a cleaner-less system.SOLUTION: An image forming apparatus has image carriers and electrifying members, and can store a developer including toner particles and transfer promotion particles having an average particle diameter of 30 nm or more and 1000 nm or less. The particles in a surface layer of the image carrier has, in a number-based particle size distribution, a first peak where a peak top has the highest frequency and a second peak where the peak top has the second highest frequency. The peak top having a larger particle diameter has a particle diameter DA of 80 nm or more and 300 nm or less. Projections CA derived from particles PAA having a particle diameter of DA±20 nm and a height of 10 nm or more and 300 nm or less are arranged on the surface of the surface layer. The average value of the distance between the gravity centers of the projections CA is 150 nm or more and 500 nm or less, and the standard deviation of the distance between the gravity centers of the projections CA is 250 nm or less.SELECTED DRAWING: Figure 6

Description

The present invention relates to an image forming apparatus and a process cartridge.

Image forming devices that form images using an electrophotographic process, such as copiers and laser printers, have been known for some time. In a transfer process, this image forming device electrostatically transfers the toner image formed on the surface of the photosensitive drum onto an intermediate transfer body or recording material by applying a voltage from a voltage source to a transfer member arranged opposite a photosensitive drum as an image carrier. When forming a toner image of multiple colors, this transfer process is repeatedly performed for the toner images of multiple colors to form a toner image of multiple colors on the surface of the intermediate transfer body or recording material. Toner that has not been transferred from the photosensitive drum to the intermediate transfer body or recording material is removed from the photosensitive drum by a cleaning member and stored as waste toner in a waste toner storage section in a cleaning unit.

In recent years, cleanerless systems have been proposed that omit the cleaning system for the photosensitive drum surface in order to reduce the size of the device. To realize a cleanerless system, it is necessary to reduce the amount of residual toner remaining on the photosensitive drum surface after the toner image is transferred by the transfer member by improving the transfer efficiency of the toner image from the photosensitive drum to the intermediate transfer body.

Patent Document 1 proposes a configuration for realizing a cleanerless system in which the surface of the photosensitive drum is made to have a convex shape by incorporating particles into it, thereby reducing the adhesive force between the photosensitive drum and the toner, thereby improving transfer efficiency, in order to bring the toner and the surface of the photosensitive drum into point contact.

JP 2014-002364 A

However, when the adhesive force between the photosensitive drum and the toner is reduced, the adhesive force between other members and the toner becomes relatively large, which can cause problems. For example, in a configuration in which a charging roller that rotates in contact with the photosensitive drum is used as a charging means for charging the surface of the photosensitive drum to an arbitrary potential, the transfer residual toner is likely to adhere to the charging roller. As a result, the charging roller may be covered with toner, causing charging failure. Conventionally, the transfer residual toner is peeled off from the charging roller by an electrical force when it is nipped between the photosensitive drum and the charging roller, so most of the toner adheres to the photosensitive drum and toner adhesion to the charging roller is suppressed. However, when the adhesive force between the photosensitive drum and the transfer residual toner is reduced and the adhesive force between the charging roller and the transfer residual toner becomes relatively large, the transfer residual toner cannot be peeled off from the charging roller by electrical force alone, and the transfer residual toner adheres to the charging roller, causing charging failure.

The present invention was made in consideration of the above problems, and aims to reduce the adhesion force between the photosensitive drum and toner in a cleanerless image forming device, improving transfer efficiency while suppressing toner adhesion to other members that come into contact with the photosensitive drum.

The present invention employs the following configuration.
An image carrier;
a charging member that contacts the image carrier and charges the image carrier to a predetermined potential;
An image forming apparatus having a developer storage device,
the developer is composed of toner particles and transfer-promoting particles adhering to surfaces of the toner particles, the transfer-promoting particles having an average particle size of 30 nm or more and 1000 nm or less;
the image bearing member has a surface layer containing particles and a binder resin,
the particles contained in the surface layer have a plurality of peaks in a particle size distribution based on number,
Among the plurality of peaks, a peak having a peak top frequency of 20 nm or more in the particle size distribution is designated as a first peak, and a peak having a peak top frequency second highest after the first peak is designated as a second peak,
The particle size DA of the peak top of the first peak or the second peak, whichever has a larger particle size value at the peak top, is 80 nm or more and 300 nm or less;
Among the particles contained in the surface layer, particles having a particle size in the range of DA±20 nm are referred to as particles PAA, and convex portions derived from the particles PAA and having a height of 10 nm or more and 300 nm or less are referred to as convex portions CA. The convex portions CA are disposed on the surface of the surface layer,
When the surface layer is viewed from above, an average value of the distance between the centers of gravity of the convex portions CA is 150 nm or more and 500 nm or less, and a standard deviation of the distance between the centers of gravity of the convex portions CA is 250 nm or less.
The image forming apparatus is characterized in that:
The present invention also uses the following configuration:
An image carrier;
a charging member that contacts the image carrier and charges the image carrier to a predetermined potential;
A process cartridge capable of accommodating a developer,
the developer is composed of toner particles and transfer-promoting particles adhering to surfaces of the toner particles, the transfer-promoting particles having an average particle size of 30 nm or more and 1000 nm or less;
A process cartridge having
the image bearing member has a surface layer containing particles and a binder resin,
the particles contained in the surface layer have a plurality of peaks in a particle size distribution based on number,
Among the plurality of peaks, a peak having a peak top frequency of 20 nm or more in the particle size distribution is designated as a first peak, and a peak having a peak top frequency second highest after the first peak is designated as a second peak,
The particle size DA of the peak top of the first peak or the second peak, whichever has a larger particle size value at the peak top, is 80 nm or more and 300 nm or less;
Among the particles contained in the surface layer, particles having a particle size in the range of DA±20 nm are referred to as particles PAA, and convex portions derived from the particles PAA and having a height of 10 nm or more and 300 nm or less are referred to as convex portions CA. The convex portions CA are disposed on the surface of the surface layer,
When the surface layer is viewed from above, the average value of the distance between the centers of gravity of the convex portions CA is 150 nm or more and 500 nm or less, and the standard deviation of the distance between the centers of gravity of the convex portions is 250 nm or less.
The process cartridge is characterized in that

According to the present invention, in a cleanerless image forming device, it is possible to reduce the adhesion force between the photosensitive drum and the toner, improving transfer efficiency, while suppressing toner adhesion to other members that come into contact with the photosensitive drum.

1 is a cross-sectional view of an image forming apparatus according to a first embodiment of the present invention; Control block diagram in the first embodiment Example of Layer Structure of Electrophotographic Photoreceptor in Example 1 Example of Layer Structure of Electrophotographic Photoreceptor in Example 1 Schematic diagram of a surface layer of an electrophotographic photoreceptor in Example 1 Schematic diagram of toner and transfer-promoting particles in Example 1 Images used to verify the effectiveness in Example 1 Results of verifying the effect of concentration change in Example 1 FIG. 1 is a diagram showing the amount of developer adhered to the charging roller 2 in the first embodiment; FIG. 1 is a diagram for explaining the mechanism of the verification results in Example 1. Relationship between transfer-promoting particle size and intermolecular force in Example 1 Schematic diagram of toner surface in Example 2 Schematic diagram of the convex shape of the toner surface in Example 2 Schematic diagram of the convex shape of the toner surface in Example 2 Schematic diagram of the convex shape of the toner surface in Example 2 Schematic diagram of toner and transfer-promoting particles in Example 2 Results of verifying the effect of concentration change in Example 2 FIG. 13 shows transfer-promoting particles attached to the charging roller 2 in Example 2. FIG. 10 is a diagram for explaining the mechanism of the verification results in Example 2. A diagram explaining the particle size distribution of the surface layer particles.

The following describes in detail preferred embodiments of the present invention with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the following embodiments should be modified as appropriate depending on the configuration of the device to which the present invention is applied and various conditions. Therefore, unless otherwise specified, the scope of the present invention is not intended to be limited. Although the embodiments describe multiple features, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined in any desired manner.

[Example 1]
(Image forming apparatus)
The present invention is applicable to electrophotographic image forming apparatuses, and is particularly suitable for image forming apparatuses using a so-called drum cleanerless system that does not have a cleaning means for the image carrier.

Figure 1 is a schematic cross-sectional view showing an example of an image forming apparatus 100 of this embodiment, and Figure 2 is a block diagram showing the functional configuration of the image forming apparatus 100. The configuration and operation of the image forming apparatus 100 will be described below using each figure. The image forming apparatus of this embodiment is a so-called tandem type printer equipped with multiple image forming stations a to d. The first image forming station a forms images of yellow (Y), the second image forming station b forms images of magenta (M), the third image forming station c forms images of cyan (C), and the fourth image forming station d forms images of black (Bk). The configuration of each image forming station is the same except for the color of the toner they contain, and the following description will be given using the first image forming station a. In addition, hereinafter, unless a distinction is particularly required, a to d in Y, M, C, and K will be omitted and a general description will be given.

The first image forming station a comprises a drum-shaped electrophotographic photosensitive member (photosensitive drum) 1a, a charging roller 2a as a charging means, an exposure unit 3a, and a developing unit 4a. The photosensitive drum 1a is an image carrier that carries a toner image and is driven to rotate in the direction of the arrow at a peripheral speed (process speed) of 150 mm/sec by a photosensitive drum drive unit 110. The photosensitive drum 1a is an aluminum tube with a diameter of φ20 mm on which a photosensitive layer and a surface layer are provided, and the surface layer is a thin film layer with a thickness of 20 μm formed from polyarylate.

When the control unit 200 of the controller 202 receives an image signal, the image forming operation is started, and the photosensitive drum 1a is rotated. During the rotation process, the photosensitive drum 1a is uniformly charged to a predetermined potential with a predetermined polarity (in this embodiment, the normal polarity is negative) by the charging roller 2a, and is exposed to light by the exposure unit 3a according to the image signal. As a result, an electrostatic latent image corresponding to the yellow color component image of the target color image is formed. Next, the electrostatic latent image is developed by the developer (yellow developer) 4a at the development position, and visualized as a yellow toner image.

The charging roller 2a as a charging member is in contact with the surface of the photosensitive drum 1a with a predetermined pressure contact force, forming a charging section. The charging roller 2a rotates relative to the photosensitive drum 1a due to friction with the surface of the photosensitive drum 1a. A predetermined DC voltage is applied to the rotating shaft of the charging roller 2a from a charging voltage power source 120 in accordance with the image forming operation. In this embodiment, the charging roller 2a is a metal shaft with a diameter of φ5.5 mm, on which an elastic layer made of a conductive elastic body with a thickness of 1.5 mm and a volume specific resistivity of about 1×10 ⁶ Ωcm is provided. In accordance with the image forming operation, the control unit 200 applies a DC voltage of −1050 V as a charging voltage to the rotating shaft of the charging roller 2a, thereby charging the surface of the photosensitive drum 1a to a predetermined potential of −500 V. The surface potential of the photosensitive drum 1a was measured using a surface potential meter Model 344 manufactured by Trek. At this time, the surface potential of the photosensitive drum 1a is −500 V, which is the surface potential of the photosensitive drum 1 when no image is formed, and is a dark potential (Vd) where no toner image is developed.

The surface layer of the charging roller 2a is provided with many protrusions, with the average height of the protrusions being approximately 10 μm. The protrusions provided on the surface layer of the charging roller 2a act as spacers between the charging roller 2a and the photosensitive drum 1a in the charging section. When residual toner, which is toner that is not transferred in the primary transfer section described below and remains on the photosensitive drum 1a, enters the charging section, the protrusions serve to prevent the charging roller 2a from being soiled with the residual toner by contacting areas other than the protrusions.

The exposure unit 3a includes a laser driver, a laser diode, a polygon mirror, an optical lens system, etc. As shown in FIG. 2, the exposure unit 3 receives a time-series electric digital pixel signal of image information that has been image-processed and input from the controller 202 to the control unit 200 via the interface 201. In this embodiment, the exposure amount is adjusted so that the image formation potential Vl of the photosensitive drum 1 in the electrostatic latent image area after exposure by the exposure unit 3a is -100V. The image formation potential is also called the bright area potential.

The developing device 4a is equipped with a developing roller 41a as a developing member (developer carrier) and a non-magnetic one-component developer composed of toner and transfer-promoting particles described later. The developing device 4a is a developing means that performs a developing action on the photosensitive drum 1 in order to develop the electrostatic latent image into a toner image, and is a developer container that contains the developer. The developing device 4a and the main body of the image forming device 100 are equipped with a developing contact/separation mechanism 40 that controls the contact/separation (development separation) state of the developing roller 41a and the photosensitive drum 1a as shown in FIG. 2. The control unit 200 contacts and separates the developing roller 41a and the photosensitive drum 1a according to the image forming operation, etc. When the developing roller 41a and the photosensitive drum 1a are in contact with each other, the developing roller 41a is in contact with the photosensitive drum 1a with a pressing force of 200 gf. The width of the development nip portion, which is the contact portion between the development roller 41a and the photosensitive drum 1a, is 2 mm in the rotation direction of the photosensitive drum 1 and 220 mm in the longitudinal direction of the photosensitive drum. The development roller 41a is driven to rotate by the development roller drive unit 130 in the forward direction of the surface movement of the photosensitive drum 1a so that the surface movement speed (hereinafter, the circumferential speed) in the development nip portion is equal to the circumferential speed of the photosensitive drum 1a.

The pre-exposure unit 5a as a charge removing means removes electricity by exposing the surface of the photosensitive drum 1a to light before the surface of the photosensitive drum 1a is charged by the charging roller 2a. By removing electricity from the surface of the photosensitive drum 1a, the pre-exposure unit 5a has a role of leveling the surface potential formed on the photosensitive drum 1 and a role of controlling the amount of discharge caused by discharge occurring in the charging section.

The control unit 200 also controls the development voltage power supply 140 to apply a DC voltage of -300V as the development voltage Vdc to the core of the development roller 41a when the development roller 41a and the photosensitive drum 1a are in contact during image formation. During image formation, the toner carried on the development roller 41a is developed on the image formation potential Vl of the photosensitive drum 1a by the electrostatic force generated by the potential difference between the development voltage Vdc = -300V and the image formation potential Vl = -100V of the photosensitive drum 1a.

In the following explanation, a high potential and applied voltage refers to an absolute value that is larger on the negative polarity side (e.g., -1000V compared to -500V), and a low potential refers to an absolute value that is smaller on the negative polarity side (e.g., -300V compared to -500V). This is because the negatively charged toner in this embodiment is considered as the standard.

In addition, the voltage in this embodiment is expressed as a potential difference with respect to the earth potential (0 V). Therefore, the development voltage Vdc = -300 V is interpreted as having a potential difference of -300 V with respect to the earth potential due to the development voltage applied to the core metal of the development roller 41a. This is also true for the charging voltage, transfer voltage, etc.

Next, the control unit 200 will be described. As mentioned above, FIG. 2 is a control block diagram showing the outline of the control mode of the main parts of the image forming apparatus 100 in this embodiment. The controller 202 exchanges various electrical information with the host device, and controls the image forming operation of the image forming apparatus 100 in a central manner via the interface 201 by the control unit 200 in accordance with a predetermined control program and reference table. The control unit 200 is configured with a CPU 155, which is a central element that performs various calculation processes, and a memory 154 such as a ROM and a RAM, which are storage elements. The RAM stores the detection results of the sensor, the count results of the counter, the calculation results, etc., and the ROM stores the control program and data tables obtained in advance by experiments, etc.

The control unit 200 is connected to each control object, sensor, counter, etc. in the image forming apparatus 100. The control unit 200 controls the transmission and reception of various electrical information signals and the timing of driving each unit, and controls a predetermined image formation sequence. For example, the control unit 200 controls the voltage and exposure amount applied by the charging voltage power supply 120, the developing voltage power supply 140, the exposure unit 3, the primary transfer voltage power supply 160, and the secondary transfer voltage power supply 150. In addition, the control unit 200 also controls the photosensitive drum drive unit 110, the developing roller drive unit 130, and the developing contact and separation mechanism 40. The image forming apparatus 100 forms an image on the recording material P based on an electrical image signal input from a host device to the controller 202. Examples of the host device include an image reader, a personal computer, a facsimile, and a smartphone.

The toner in this embodiment is a negatively charged non-magnetic toner produced by suspension polymerization, has a volume average particle size of 5.5 μm, and is negatively charged when carried on the developing roller 41a. The volume average particle size of the toner was measured using a laser diffraction particle size distribution analyzer LS-230 manufactured by Beckman Coulter, Inc. Details of the toner will be described later.

The intermediate transfer belt 10 as an intermediate transfer body is stretched by a plurality of stretching members 11, 12, and 13, and is driven to rotate at the same peripheral speed as the photosensitive drum 1a in a direction moving in the circumferential direction at a portion facing the photosensitive drum 1a where the intermediate transfer belt 10 abuts against the photosensitive drum 1a. A DC voltage of 200 V is applied from a primary transfer voltage power source 160 to the primary transfer roller 14a as a primary transfer member at the time of primary transfer during the image forming operation. The yellow toner image formed on the photosensitive drum 1a is electrostatically transferred onto the intermediate transfer belt 10 in the process of passing through a primary transfer portion, which is the portion where the photosensitive drum 1a abuts against the primary transfer roller 14a via the intermediate transfer belt 10.

The primary transfer roller 14a is a cylindrical metal roller with a diameter of 6 mm, and is made of nickel-plated SUS. The primary transfer roller 14a is located at a position offset by 8 mm downstream in the direction of movement of the intermediate transfer belt 10 from the center position of the photosensitive drum 1a, and the intermediate transfer belt 10 is configured to wrap around the photosensitive drum 1a. The primary transfer roller 14a is located at a position raised by 1 mm from the horizontal plane formed by the photosensitive drum 1a and the intermediate transfer belt 10 so that the amount of winding of the intermediate transfer belt 10 around the photosensitive drum 1a can be secured. The primary transfer roller 14a presses the intermediate transfer belt 10 with a force of about 200 gf. The primary transfer roller 14a rotates in response to the rotation of the intermediate transfer belt 10. The primary transfer roller 14b located at the second image forming station b, the primary transfer roller 14c located at the third image forming station c, and the primary transfer roller 14d located at the fourth image forming station d are also configured in the same manner as the primary transfer roller 14a.

Similarly, the second, third and fourth image forming stations b, c and d form a magenta toner image (second color), a cyan toner image (third color) and a black toner image (fourth color), which are transferred in a superimposed manner onto the intermediate transfer belt 10. A composite color image corresponding to the desired color image is then obtained.

The four color toner images on the intermediate transfer belt 10 are transferred en bloc onto the surface of the recording material P fed by the paper feed means 50 during the secondary transfer process, which passes through a secondary transfer nip formed by the intermediate transfer belt 10 and the secondary transfer roller 15 as a secondary transfer member. The secondary transfer roller 15 contacts the intermediate transfer belt 10 with a pressure of 50 N to form the secondary transfer nip. The secondary transfer roller 15 rotates in response to the rotation of the intermediate transfer belt 10, and a voltage of 1500 V is applied from the secondary transfer voltage power supply 150 when the toner on the intermediate transfer belt 10 is secondarily transferred to the recording material P such as paper.

Then, the recording material P carrying the four-color toner image is introduced into the fixing device 30. The fixing device 30 applies heat and pressure to the four color toners, which melt, mix, and are fixed to the recording material P. Any toner remaining on the intermediate transfer belt 10 after the secondary transfer is cleaned and removed by the cleaning device 17.

The cleaning device 17 has a cleaning blade that contacts the outer peripheral surface of the intermediate transfer belt 10 to scrape off the toner remaining on the intermediate transfer belt 10 and collects it in the cleaning device 17 for the intermediate transfer belt 10. The cleaning device 17 for the intermediate transfer belt 10 is positioned downstream of the secondary transfer section of the intermediate transfer belt 10 in the rotation direction of the intermediate transfer belt 10 so as to collect the toner adhering to the intermediate transfer belt 10.

Through the above operations, a full-color print image is formed. The electrophotographic photosensitive member (photosensitive drum 1) can be provided in a process cartridge that integrally supports a member that performs at least one process selected from the group consisting of a charging process, a developing process, and a transfer process. The process cartridge is characterized by being detachably attached to the main body of the image forming apparatus.

(Electrophotographic Photoreceptor)
The electrophotographic photoreceptor (photoreceptor drum 1) of the present invention is characterized by having a surface layer. Here, the surface layer refers to the layer located on the outermost surface of the photoreceptor, and refers to the layer that comes into contact with a charging member and a toner.

3 and 4 are diagrams showing an example of a layer structure of the photosensitive drum 1. In FIG.
Reference numeral 101 denotes a support, 102 denotes an undercoat layer, 103 denotes a charge generation layer, and 104 denotes a charge transport layer. Reference numeral 105 denotes a surface layer according to the present invention, reference numeral 106 denotes particles PAA (first particles) according to the present invention, and reference numeral 107 denotes particles (second particles) other than particles PAA according to the present invention. Reference numeral 108 denotes a binder resin. The average film thickness of the surface layer 105 at the portion not containing particles is designated as T.

One method for manufacturing the photosensitive drum 1 of the present invention is to prepare the coating liquid for each layer described below, apply the layers in the desired order, and then dry them. In this case, the coating liquid can be applied by dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, ring coating, dispense coating, or the like. Among these, dip coating is preferred from the viewpoints of efficiency and productivity.

The surface layer 105 of the photosensitive drum 1 of the present invention will be described below.
(Surface layer 105 of photosensitive drum 1)
According to the investigations made by the present inventors, the photosensitive drum 1 of the present invention is an electrophotographic photosensitive member having a surface layer 105 containing particles and a binder resin, and a plurality of peaks are present in a particle size distribution based on the number of the particles. The peak having the highest frequency of the peak top is designated as a first peak, and the peak having the second highest frequency of the peak top after the first peak is designated as a second peak. The first peak and the second peak are compared, and the peak having the larger particle diameter value of the peak top is designated as a peak PEA, and the peak top particle diameter value of the peak PEA is designated as a peak PEA. When the particle diameter DA of the particle PAA is in the range of 80 nm to 300 nm, and when particles having a particle diameter in the range of DA ±20 nm among all particles contained in the surface layer 105 are defined as particles PAA, and convex portions derived from the particles PAA and having a height of 10 nm or more and 300 nm or less are defined as convex portions CA, the convex portions CA are present on the surface of the surface layer 105, and when the surface layer 105 is viewed from above, the average value of the distance between the centers of gravity of the convex portions CA is 150 nm or more and 500 nm or less, and the standard deviation of the distance between the centers of gravity of the convex portions CA is 250 nm or less.

According to the inventors' research, the above conditions can improve transferability.

On the other hand, in order to improve the transferability in an electrophotographic image forming apparatus, it is necessary to reduce the adhesion of the toner developed on the photoreceptor. The adhesion between the toner and the electrophotographic photoreceptor is roughly divided into electrostatic adhesion and non-electrostatic adhesion. The electrostatic adhesion is largely dependent on the charge amount of the toner, since the main factor is the image force. The magnitude of the image force is proportional to the charge amount of the toner, and inversely proportional to the square of the distance between the charge amount of the toner and the surface of the photoreceptor to which it is to be attached. Therefore, the higher the height of the convex part originating from the particles on the photoreceptor surface, the greater the distance between the photoreceptor and the toner can be, so the image force is smaller and the transferability of the toner to the transfer material is improved. Methods for increasing the height of the convex part include, for example, increasing the size of the particles introduced, or increasing the proportion of particles in the surface layer 105 to push the particles to the top of the surface layer 105.

As described above, the photosensitive drum 1 of the present invention is an electrophotographic photosensitive member having a surface layer 105 containing particles and a binder resin, and has multiple peaks in the particle size distribution based on the number of particles. The peak with the highest frequency of the peak tops of the multiple peaks is defined as the first peak. Furthermore, the peak with the second highest frequency of the peak tops after the first peak is defined as the second peak. Comparing the first peak and the second peak, the peak with the larger particle diameter value of the peak top is defined as the peak PEA. In the present invention, the particle diameter DA of the peak top of the peak PEA must be in the range of 80 nm to 300 nm. More preferably, it must be in the range of 90 nm to 250 nm. Even more preferably, it must be in the range of 100 nm to 250 nm. By being in this range, the above-mentioned effect is more easily obtained in the transfer process.

In this case, the particle diameter DA of the peak top of the PEA represents the particle diameter of the particle having the maximum frequency in the surface layer 105. When the particle diameter DA is less than 80 nm, the height of the convex portion that contributes to the point contact between the toner and the convex portion originating from the particles contained in the surface layer 105 of the photosensitive drum 1 decreases, and the number of contact points increases, deteriorating the adhesion of the toner, thereby deteriorating the transferability.

When the particle diameter DA exceeds 300 nm, the curvature of the protrusions resulting from the particles becomes smaller (the radius of curvature becomes larger), and the area of adhesion between the toner and the surface layer 105 increases. As a result, the adhesion force between the toner and the surface of the photosensitive drum 1 increases, and the transferability deteriorates.

In addition, the first peak and the second peak are preferably selected from a range in which the particle size corresponding to the peak top is 20 nm or more. That is, it is preferable that, among the multiple peaks whose peak tops are 20 nm or more, the peak with the highest frequency of the peak top is the first peak, and the peak with the second highest frequency of the peak top after the first peak is the second peak. Figure 20 (a) shows an example of a particle size distribution based on the number of particles, in which the first peak exists at a particle diameter of 50 nm and the second peak exists at a particle diameter of 170 nm. In this case, the second peak with a larger particle diameter becomes the peak PEA, and its particle diameter DA is 170 nm. Therefore, the condition of 80 nm ≦ DA is satisfied. Furthermore, since the particle diameter of the first peak is 50 nm, the condition of the particle diameter at the peak top being 20 nm or more is satisfied.

Figure 20(b) shows another example of particle size distribution. There is a peak at a particle diameter of 5 nm, but since the particle diameter at the peak top is less than 20 nm, this peak is not included in the first peak or the second peak. Therefore, as in the case of Figure 20(a), the peak at a particle diameter of 50 nm is the first peak, and the peak at a particle diameter of 170 nm is the second peak. The reason for selecting the peaks in this way will be explained. Here, even if the electrophotographic photoreceptor 1 contains a large number of very small particles in the surface layer 105, it is possible to obtain the effects of the present invention as described below. Therefore, by selecting the first peak and the second peak from the peaks with particle diameters of 20 nm or more as explained with reference to Figure 20, the effects of the present invention can be stably obtained.

Next, particles PAA are particles having a particle diameter in the range of DA±20 nm contained in the surface layer 105 of the photosensitive drum 1 of the present invention. In the present invention, when a convex portion derived from the particle PAA and having a height of 10 nm to 300 nm is called a convex portion CA, it is necessary that the convex portion CA exists on the surface of the surface layer 105. If the height of the convex portion CA is less than 10 nm, the height of the convex portion CA becomes too low, so that the rotation of the toner is not promoted when the photosensitive drum 1 contacts the toner, and the electrostatic adhesion force between the toner and the surface layer 105 of the photosensitive drum 1 does not decrease, resulting in poor transferability. If the height of the convex portion CA exceeds 300 nm, the concave portion becomes large in the surface layer 105 of the photosensitive drum 1, the accumulation of external additives of the toner progresses, the adhesion of the toner increases, and the developability deteriorates.

Next, when the surface layer 105 of the photosensitive drum 1 of the present invention is viewed from above, the average distance between the centers of gravity of the convex portions CA must be 150 nm or more and 500 nm or less.

When there are few convex portions CA originating from particles on the photosensitive body surface, the distance between the centers of gravity of the convex portions CA is large, and the toner base particles come into contact with the surface layer 105 of the photosensitive drum 1. As a result, the distance between the toner base particles and the surface layer 105 of the photosensitive drum 1 cannot be maintained, the Coulomb force cannot be reduced, and the transferability cannot be improved. When the average distance between the centers of gravity of the convex portions CA exceeds 500 nm, the spacing between the convex portions CA becomes too wide compared to the curvature of the toner base particles, so the toner base particles are more likely to come into contact with the concave portions of the surface layer 105, the electrostatic adhesion force increases, and the transferability deteriorates.

On the other hand, if the distance between the centers of gravity of the convex portions CA in the surface layer 105 is too small, the surface layer 105 is filled with the convex portions CA, resulting in an increase in the number of contact points between the toner base particles and the surface layer 105. When the average value of the distance between the centers of gravity of the convex portions CA is less than 150 nm, the spacing between the convex portions CA is too narrow compared to the curvature of the toner particles, so that the number of contact points increases, the reflective force increases, and transferability deteriorates.

The distance between the centers of gravity in the present invention is more preferably 150 nm or more and 450 nm or less, and even more preferably 150 nm or more and 400 nm or less.

Furthermore, in the photosensitive drum 1 of the present invention, the standard deviation of the distance between the centers of gravity of the convex portions CA must be 250 nm or less. If the standard deviation of the distance between the centers of gravity of the convex portions CA exceeds 250 nm, there will be variation in the distribution of the convex portions CA in the surface layer 105, causing uneven adhesion of the toner to the photosensitive drum 1. As a result, uneven transferability will occur, and roughness will be seen in the halftone image that is developed and transferred with the toner dispersed to a certain extent.

In addition, when the area occupied by the particles on the surface of the surface layer 105 of the electrophotographic photoreceptor of the present invention is S1 and the area occupied by the rest of the particles is S2, it is necessary that S1/(S1+S2) is 0.70 or more. If S1/(S1+S2) is less than 0.70, the part without particles will not be able to form a convex portion.

As a result of the inventors' investigations, it has been found that the height of the convex portion CA can be easily controlled by mixing multiple particles with different particle sizes in the surface layer. It is also believed that the tightness between the particles increases when the particles fill the gaps between the particles PAA in a form close to the closest packing state toward the surface of the drum. This is because when the particles are impacted in the tangential direction of the drum surface, the movement of the particles is suppressed by the binding resin between the particles and the other particles holding back the movement of the particles toward the drum surface, which is achieved by controlling the distance between the particles as described above. This has the effect of suppressing the detachment of particles from the surface layer 105 of the electrophotographic photosensitive member even when rubbed against the charging member, developing member, and transfer member that come into contact with the electrophotographic photosensitive member.

Theoretically, the upper limit of S1/(S1+S2) is 1.00. S1/(S1+S2) is more preferably 0.80 or more and 1.00 or less, and even more preferably 0.85 or more and 0.95 or less.

In the cross section of the surface layer 105 in the electrophotographic photoreceptor of the present invention, when the average film thickness of the surface layer 105 at the portion not including the convex portion CA is defined as T, it is preferable that the following formula (1) is satisfied.
D > T ... (1)

If DA is smaller than the average film thickness T, it becomes difficult to form the convex portion CA as described above, and the adhesion between the toner base particles and the electrophotographic photoreceptor is not sufficiently reduced, which increases the possibility of deterioration in transferability. If the particles are stacked as shown in Figures 3 and 4 in a manner that satisfies formula (1), the average film thickness T is preferably 50 nm to 500 nm. It is more preferably 70 nm to 450 nm, and even more preferably 80 nm to 400 nm.

In addition, in the cross section of the surface layer of the electrophotographic photoreceptor of the present invention, the peak with the highest frequency of the peak top is defined as the first peak, and the peak with the second highest frequency of the peak top after the first peak is defined as the second peak. Furthermore, when the first peak and the second peak are compared and the peak with the smaller value of the particle diameter of the peak top is defined as the peak PEB, it is preferable that the particle diameter DB of the peak PEB satisfies the following formula (2).
DB < T ... (2)

When the particles PAB are those with particle diameters in the range of DB±20 nm among all the particles contained in the surface layer 105, by making DB equal to or less than the average film thickness T, the particles PAA forming the convex portions CA and the particles PAB arranged between the convex portions CA become more closely packed, and clear recesses are formed in the surface layer 105, suppressing particle detachment. When DB is equal to or more than the average film thickness T, the particles PAB become more easily exposed to the surface layer 105, facilitating particle detachment.

Furthermore, in the cross section of the surface layer 105 in the electrophotographic photoreceptor of the present invention, it is preferable that the DA and the DB satisfy the following formula (3).
DB/DA > 1/10 ... (3)

The particles PAA form the convex portions CA, and the particles PAB are filled between the particles PAA, so that it becomes possible to control the average value and standard deviation of the distance between the centers of gravity between the convex portions CA. In addition, by making the particle diameters of the particles PAA and PAB satisfy the above formula (3), it becomes possible to suppress detachment of the particles against tangential rubbing in the surface layer 105 of the electrophotographic photosensitive member while maintaining a sufficient height of the convex portions CA. More preferably, the right side of formula (3) is 1/3. In other words, it is preferable to satisfy DB/DA>1/3. Furthermore, it is preferable that the right side is 1/2. In other words, DB/DA>1/2
It is preferable that the following is satisfied.

Next, it is preferable that the ratio of the number of the convex portions CA to the number of the convex portions present on the surface of the surface layer 105 in the electrophotographic photoreceptor of the present invention is 90% or more by number. Here, it is known that, during rubbing in the development section of the image forming apparatus, convex portions not derived from particles PAA have weak mechanical strength and are worn by rubbing in the tangential direction of the electrophotographic photoreceptor. Therefore, when the ratio of the number of the convex portions CA to the number of the convex portions is less than 90%, it becomes difficult to maintain good transferability over long-term use.

Furthermore, it is preferable that the half-width of the peak PAA in the surface layer 105 of the electrophotographic photoreceptor of the present invention is 20 nm or more and 50 nm or less. Since the height of the convex portion CA is controlled by the size of the particle diameter, it is preferable that the half-width of the peak PAA is within a certain range as much as possible. If the half-width of the PAA exceeds 50 nm, the height of the convex portion CA also varies greatly, and the state of point contact between the toner base particle and the surface of the surface layer 105 of the electrophotographic photoreceptor varies, which does not promote the rotation of the toner well and makes it difficult to reduce the electrostatic adhesion force between the surfaces. By promoting point contact between the toner and the photoreceptor, the adhesion force of the toner to the photoreceptor is reduced, making it possible to improve transferability.

It is preferable that the maximum height difference Rz of the surface of the surface layer 105 in the electrophotographic photoreceptor of the present invention is 100 nm or more and 400 nm or less. If the maximum height difference Rz of the surface of the surface layer 105 is less than 100 nm, the rotation of the toner is not promoted well and the transferability is not improved. If the maximum height difference Rz of the surface of the surface layer 105 exceeds 400 nm, the accumulation of external additives in the recesses progresses, and the developability deteriorates. In addition, discharge is likely to occur in the transfer process, and roughness due to uneven density may occur in the halftone image. More preferably, the maximum height difference Rz is 200 nm or more and 375 nm or less, and even more preferably 225 nm or more and 350 nm or less.

The circularity of the particles PAA contained in the surface layer 105 of the electrophotographic photoreceptor of the present invention is preferably 0.950 or more. If the circularity of the particles PAA is less than 0.950, the contact area between the toner base particles and the surface of the surface layer 105 of the electrophotographic photoreceptor becomes large. This results in an increase in non-electrostatic adhesion, and the transferability of the toner tends to deteriorate with long-term use.

The average circularity of the particles was determined using a scanning electron microscope as follows. The particles to be measured were observed using a scanning electron microscope ("JSM7800F", manufactured by JEOL Ltd.), and the particle size of each of 100 particles was measured from the image obtained by observation. For each particle, the longest side a and the shortest side b of the primary particle were measured, and the circularity was calculated as b/a. The circularities of the 100 particles were averaged to calculate the average circularity.

The surface layer 105 of the electrophotographic photoreceptor of the present invention contains at least the particles PAA and the particles PAB as described above. Examples of the particles PAA used in the present invention include organic resin particles such as acrylic resin particles, inorganic particles such as silica, and organic-inorganic hybrid particles. The particles PAA and the particles PAB may be made of the same material or different materials.

The acrylic particles contain a polymer of an acrylic acid ester or a methacrylic acid ester. Among them, styrene acrylic particles are more preferable. There are no particular limitations on the degree of polymerization of the acrylic resin or styrene acrylic resin, or whether the resin is thermoplastic or thermosetting. Examples of organic resin particles include cross-linked polystyrene, cross-linked acrylic resin, phenolic resin, melamine resin, polyethylene, polypropylene, acrylic particles, polytetrafluoroethylene particles, and silicone particles.

Examples of inorganic particles include silica particles, metal oxide particles, and metal particles. As the particles contained in the surface layer 105 of the electrophotographic photoreceptor of the present invention, it is preferable to use inorganic particles that have low elasticity and are advantageous in promoting point contact between the toner and the photoreceptor.

Among these, silica particles are preferred when inorganic particles are used. Compared to other insulating particles, silica particles have a lower elastic modulus and a higher average circularity, and are therefore expected to promote point contact between the toner and the photoreceptor, thereby reducing adhesion.

As the silica particles, known silica fine particles can be used, and either dry silica fine particles or wet silica fine particles can be used. Preferably, the silica fine particles are wet silica fine particles obtained by the sol-gel method (hereinafter, also referred to as sol-gel silica).

The sol-gel silica used for the particles contained in the surface layer 105 of the electrophotographic photoreceptor of the present invention may be hydrophilic or may have a hydrophobic surface. Examples of the hydrophobic treatment method include a sol-gel method in which the solvent is removed from the silica sol suspension, dried, and then treated with a hydrophobic treatment agent, and a method in which the hydrophobic treatment agent is directly added to the silica sol suspension and treated at the same time as drying. From the viewpoint of controlling the half-width of the particle size distribution and the saturated water adsorption amount, the method of directly adding the hydrophobic treatment agent to the silica sol suspension is preferred.

Examples of the hydrophobic treatment agent include the following.
Chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, t-butyldimethylchlorosilane, and vinyltrichlorosilane;
Tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltrimethoxysilane, i-butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, i-butyl Alkoxysilanes such as ethyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, and γ-(2-aminoethyl)aminopropylmethyldimethoxysilane;
silazanes such as hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexabutyldisilazane, hexapentyldisilazane, hexahexyldisilazane, hexacyclohexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, and dimethyltetravinyldisilazane;
Silicone oils such as dimethyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil, alkyl modified silicone oil, chloroalkyl modified silicone oil, chlorophenyl modified silicone oil, fatty acid modified silicone oil, polyether modified silicone oil, alkoxy modified silicone oil, carbinol modified silicone oil, amino modified silicone oil, fluorine modified silicone oil, and terminal reactive silicone oil;
Siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, and octamethyltrisiloxane;

Fatty acids and their metal salts include long-chain fatty acids such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid, and salts of the above fatty acids with metals such as zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.
Among these, alkoxysilanes, silazanes, and silicone oils are preferably used because they are easy to carry out hydrophobic treatment. These hydrophobic treatment agents may be used alone or in combination of two or more kinds.

The surface layer 105 in the present invention may contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slippage agents, and abrasion resistance improvers. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, and silicone oils.

The surface layer 105 of the present invention can be formed by preparing a coating liquid for the surface layer containing the above-mentioned materials and solvent, forming a coating film from this, and drying and/or curing it. Examples of solvents used in the coating liquid include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

In the surface layer 105 of the present invention, the ratio of the particle volume to the total volume of the surface layer 105 is preferably 40% by volume to 90% by volume. Furthermore, 45% by volume to 85% by volume is more preferable, and 50% by volume to 80% by volume is even more preferable. By being in this range, the formation of the convex portions of the surface layer 105 as described above can be reliably achieved. If it is 30% by volume or less, the height of the convex portions will be low, and the transferability will not improve. If it is 90% by volume or more, the particles will be severely detached, and the transferability will deteriorate and the image density will decrease when a durability test is performed.

A charge transport material may be added to the surface layer coating liquid in order to improve the charge transport ability of the surface layer 105. Additives may also be added to improve various functions. Examples of additives include conductive particles, antioxidants, ultraviolet absorbers, plasticizers, and leveling agents.

The binder resin according to the present invention may have the following forms. Here, it is preferable that the surface layer 105 contains a charge transport material.

Examples of binder resins include polyester resins, acrylic resins, phenoxy resins, polycarbonate resins, polystyrene resins, phenolic resins, melamine resins, and epoxy resins. Among these, polycarbonate resins, polyester resins, and acrylic resins are preferred. In addition,

The surface layer 105 of the present invention may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the reaction include a thermal polymerization reaction, a photopolymerization reaction, and a radiation polymerization reaction. Examples of the polymerizable functional group possessed by the monomer having a polymerizable functional group include an acrylic group and a methacrylic group. A material having a charge transport function may be used as the monomer having a polymerizable functional group.

The compound having a polymerizable functional group may have a charge transport structure in addition to the chain polymerizable functional group. As the charge transport structure, a triarylamine structure is preferable in terms of charge transport. As the chain polymerizable functional group, an acryloyl group or a methacryloyl group is preferable. The number of functional groups may be one or more. Among them, it is particularly preferable to form a cured film containing a compound having multiple functional groups and a compound having one functional group, since the distortion caused by the polymerization of the multiple functional groups is easily eliminated.

Examples of the compound having one functional group are shown in (2-1) to (2-6).

Examples of the compound having multiple functional groups are shown in (3-1) to (3-6).

<Support>
In the present invention, the electrophotographic photoreceptor preferably has a support. In the present invention, the support is preferably a conductive support having electrical conductivity. The shape of the support may be a cylinder, a belt, a sheet, or the like. Among them, a cylindrical support is preferable. The surface of the support may be subjected to electrochemical treatment such as anodization, blasting, cutting, or the like.

The material of the support is preferably a metal, a resin, a glass, etc. Examples of the metal include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among them, an aluminum support using aluminum is preferable.
Furthermore, the resin or glass may be made conductive by a process such as mixing with or coating with a conductive material.

<Conductive Layer>
In the present invention, a conductive layer may be provided on the support. By providing the conductive layer, scratches and irregularities on the support surface can be concealed and light reflection on the support surface can be controlled. The conductive layer preferably contains conductive particles and a resin.

Examples of materials for the conductive particles include metal oxides, metals, and carbon black.
Examples of metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, etc. Examples of metals include aluminum, nickel, iron, nichrome, copper, zinc, silver, etc.

Among these, it is preferable to use metal oxides as the conductive particles, and it is particularly preferable to use titanium oxide, tin oxide, or zinc oxide.
When a metal oxide is used as the conductive particles, the surface of the metal oxide may be treated with a silane coupling agent or the like, or the metal oxide may be doped with an element such as phosphorus or aluminum or an oxide thereof.

The conductive particles may have a laminated structure in which a pre-coated particle such as titanium oxide, barium sulfate, or zinc oxide is coated with a metal oxide having a different composition from that of the pre-coated particle. The coating may be a metal oxide such as tin oxide.
When a metal oxide is used as the conductive particles, the average primary particle size is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, and alkyd resin.

The conductive layer may further contain silicone oil, resin particles, titanium oxide, or other masking agents.

The average thickness of the conductive layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less.

The conductive layer can be formed by preparing a coating solution for the conductive layer containing the above-mentioned materials and solvent, forming a coating film from this, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Examples of dispersion methods for dispersing the conductive particles in the coating solution for the conductive layer include methods using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

<Undercoat layer>
In the present invention, an undercoat layer may be provided on the support or the conductive layer.

The average thickness of the undercoat layer is preferably 0.1 μm or more and 50 μm or less, more preferably 0.2 μm or more and 40 μm or less, and particularly preferably 0.3 μm or more and 30 μm or less.

Examples of the resin for the undercoat layer include polyacrylic acid resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyethylene oxide resins, polypropylene oxide resins, ethyl cellulose resins, methyl cellulose resins, polyamide resins, polyamic acid resins, polyurethane resins, polyimide resins, polyamideimide resins, polyvinyl phenol resins, melamine resins, phenolic resins, epoxy resins, and alkyd resins.

Alternatively, the resin may have a structure in which a resin having a polymerizable functional group is crosslinked with a monomer having a polymerizable functional group.
The undercoat layer may contain an inorganic compound or an organic compound in addition to the resin.

Inorganic compounds include, for example, metals, oxides, and salts.
Examples of metals include gold, silver, aluminum, etc. Examples of oxides include zinc oxide, white lead, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, indium oxide, tin oxide, zirconium oxide, etc. Examples of salts include barium sulfate and strontium titanate.
These inorganic compounds may be present in the film in the form of particles.

The number-average particle size of the particles is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

These inorganic compounds may have a laminated structure having core particles and a coating layer that coats the particles.
The surfaces of these inorganic compounds may be treated with silicone oil, silane compounds, silane coupling agents, other organosilicon compounds, organotitanium compounds, etc. Furthermore, they may be doped with elements such as tin, phosphorus, aluminum, and niobium.

The organic compounds include, for example, electron transport compounds and conductive polymers.
Examples of the conductive polymer include polythiophene, polyaniline, polyacetylene, polyphenylene, and polyethylenedioxythiophene.

Examples of the electron transport substance include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, aryl halide compounds, silole compounds, and boron-containing compounds.
The electron transport material may have polymerizable functional groups and may be crosslinked with a resin having functional groups capable of reacting with the polymerizable functional groups, such as hydroxyl, thiol, amino, carboxyl, vinyl, acryloyl, methacryloyl, and epoxy groups.

These organic compounds may be present in the film in particulate form, or may be surface-treated.

The undercoat layer may contain various additives such as leveling agents such as silicone oil, plasticizers, and thickeners.

The undercoat layer is obtained by preparing a coating solution for the undercoat layer containing the above-mentioned materials, applying it onto the support or conductive layer, and then drying or curing the coating.

Examples of the solvent used in preparing the coating liquid include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.
Examples of a method for dispersing the particles in the coating liquid include methods using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

<Photosensitive layer>
The photosensitive layer of an electrophotographic photoreceptor is mainly classified into (1) a laminated type photosensitive layer and (2) a single-layer type photosensitive layer. (1) The laminated type photosensitive layer is a photosensitive layer having a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. (2) The single-layer type photosensitive layer is a photosensitive layer containing both a charge generation material and a charge transport material.

(1) Multi-Layer Photosensitive Layer The multi-layer photosensitive layer has a charge generating layer and a charge transport layer.

(1-1) Charge Generation Layer The charge generation layer preferably contains a charge generation material and a resin.
Examples of the charge generating material include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferred. Among phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferred.

The content of the charge generating material in the charge generating layer is preferably 40% by weight or more and 85% by weight or less, and more preferably 60% by weight or more and 80% by weight or less, based on the total weight of the charge generating layer.

Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, polyvinyl chloride resin, etc. Among these, polyvinyl butyral resin is more preferable.

The charge generating layer may further contain additives such as antioxidants and ultraviolet absorbers. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

The charge generation layer can be formed by preparing a coating solution for the charge generation layer containing the above-mentioned materials and solvent, forming this coating film on the undercoat layer, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

The thickness of the charge generating layer is preferably 0.1 μm or more and 1.5 μm or less, and more preferably 0.15 μm or more and 1.0 μm or less.

(1-2) Charge Transport Layer The charge transport layer preferably contains a charge transport material and a resin.

Examples of charge transport substances include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Among these, triarylamine compounds and benzidine compounds are preferred.

The content of the charge transport material in the charge transport layer is preferably 25% by weight or more and 70% by weight or less, and more preferably 30% by weight or more and 55% by weight or less, based on the total weight of the charge transport layer.

Examples of resins include polyester resin, polycarbonate resin, acrylic resin, polystyrene resin, etc. Among these, polycarbonate resin and polyester resin are preferred. As the polyester resin, polyarylate resin is particularly preferred.

The content ratio (mass ratio) of the charge transport material to the resin is preferably 4:10 to 20:10, and more preferably 5:10 to 12:10.

The charge transport layer may also contain additives such as antioxidants, UV absorbers, plasticizers, leveling agents, slippage agents, and abrasion resistance improvers. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing the above-mentioned materials and solvent, forming this coating film on the charge generation layer, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents and aromatic hydrocarbon-based solvents are preferred.

The thickness of the charge transport layer is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

(2) Single-layer type photosensitive layer The single-layer type photosensitive layer can be formed by preparing a coating solution for the photosensitive layer containing a charge generating material, a charge transporting material, a resin and a solvent, forming this coating film on the undercoat layer, and drying it. The charge generating material, the charge transporting material and the resin are the same as the examples of materials in the above "(1) Multi-layer type photosensitive layer".

The thickness of the single-layer photosensitive layer is preferably 10 μm or more and 45 μm or less, and more preferably 25 μm or more and 35 μm or less.

<Measurement of physical properties of electrophotographic photoreceptor>
<Method of Observing the Lamination State of Particles Contained in the Surface Layer 105 of an Electrophotographic Photoreceptor and Measuring Particle Size Distribution>
The cross-section of the electrophotographic photoreceptor prepared in the examples was observed. It was determined whether the particles were laminated in a single layer in the surface layer as shown in FIG. 3, or in multiple layers as shown in FIG. 4. The samples for the cross-section observation were taken by dividing the photoreceptor into four equal parts in the longitudinal direction, and taking samples at positions of ¼, ½, and ¾ of the length from the end, and shifting them by 120° in the circumferential direction. Sample pieces of 5 mm square were cut out from each photoreceptor, and the surface layer 105 was three-dimensionalized to 2 μm × 2 μm × 2 μm using Slice & View of FIB-SEM.

The conditions for Slice & View were as follows:
Analytical sample processing: FIB method Processing and observation equipment: SII/Zeiss NVision 40
Slice interval: 10 nm
(Observation conditions)
Acceleration voltage: 1.0 kV
Sample tilt: 54°
WD: 5mm
Detector: BSE detector Aperture: 60 μm, high current
ABC:ON
Image resolution: 1.25 nm/pixel

The measurement environment is as follows: temperature: 23°C, pressure: 1×10-4 Pa. Note that the processing and observation device can also be an FEI Strata 400S (sample inclination: 52°).

The analysis area was 2 μm long x 2 μm wide, and the information for each cross section was accumulated to determine the volume V per 2 μm long x 2 μm wide x 2 μm thick (8 μm3) on the surface of the surface layer 105. Image analysis for each cross section was performed using image processing software: Image-Pro Plus manufactured by Media Cybernetics.

From the difference in contrast of FIB-SEM Slice & View, the particle content in the total volume of the surface layer 105 was calculated. Furthermore, based on the information obtained from image analysis, the volume V of the particles of the present invention in a volume of 2 μm x 2 μm x 2 μm (unit volume: 8 μm3) was determined for each of the four sample pieces, and the conductive particle content [volume %] (= V μm3 / 8 μm3 x 100) was calculated. The average value of the particle content value in each sample piece was taken as the content [volume %] of each particle of the present invention in the surface layer relative to the total volume of the surface layer 105. The particle composition was determined using the SEM-EDX function.

Check whether there are multiple peaks in the particle size distribution, with the particle diameter of the particles contained on the surface of the surface layer 105 on the horizontal axis and the number-based frequency of each particle diameter on the vertical axis. In that particle size distribution, the peak with the highest frequency of the peak top is designated as the first peak. Next, the peak with the second highest frequency of the peak top is designated as the second peak. Furthermore, the first peak and the second peak are compared, and the peak with the larger particle diameter value of the peak top is designated as the peak PEA.

The particle diameter of the peak top of peak PEA in the particle size distribution is defined as DA. Of all the particles contained in the surface layer 105, particles with a particle diameter in the range of DA ± 20 nm are defined as particles PAA, and convex portions derived from particles PAA are defined as convex portions CA. When particles with different compositions were present, they were identified using mapping images obtained by EDS. Furthermore, 100 convex portions were measured, and the proportion of convex portions CA derived from particles PAA was calculated.

Next, in the particle size distribution A, the first peak and the second peak are compared, and the peak with the smaller particle diameter value at the peak top is designated as peak PEB. The particle diameter DB at the peak top of peak PEB is calculated.

In addition, the average film thickness T of the surface layer 105 was measured in the cross-sectional image of the surface layer 105, as shown in Figures 3 and 4.

<Method of measuring the average value and standard deviation of the distance between the centers of gravity of particles in the surface layer of an electrophotographic photoreceptor>
In the electrophotographic photoreceptor of the present invention, when the surface layer 105 is viewed from above, the average value and standard deviation of the distance between the centers of gravity of the convex portions CA derived from the particles PAA can be calculated as follows.

The surface of the surface layer 105 of the electrophotographic photoreceptor was photographed at an acceleration voltage of 10 kV using a scanning electron microscope (SEM) ("S-4800", manufactured by JEOL Ltd.). Photographs of the surface layer 105 of the electrophotographic photoreceptor of the present invention at 30,000 times magnification were captured by a scanner at 12 locations in total, 50 mm from each end and three locations at the center in the longitudinal direction of the electrophotographic photoreceptor of the present invention, and four locations at 90 degrees each in the circumferential direction. The particles PAA in the photographic images were binarized using an image processing and analysis device ("LUZEX AP", manufactured by Nireco Corporation).

In the mode of measuring the distance between adjacent centers of gravity of particles PAA, the distance 201 between the centers of gravity of adjacent particles PAA is measured as shown in FIG. 5, and the average value of the distance between the centers of gravity is calculated. At this time, the distance between the centers of gravity is calculated by Voronoi division from each center of gravity of particles PAA. The distance between the centers of gravity and the standard deviation are calculated for a total of 10 fields of view, and the average value and standard deviation of the obtained distance between the centers of gravity are set as the average value and standard deviation of the distance between the centers of gravity of particles in the surface layer 105 of the photoconductor.

<Method of Measuring Coverage Ratio S1/(S1+S2) of Particles in the Surface Layer of an Electrophotographic Photoreceptor>
In the electrophotographic photoreceptor of the present invention, when the surface layer 105 is viewed from above, the area of the particles PAA is S1 and the total area other than the particles PAA is S2. The coverage ratio S1/(S1+S2) can be calculated as follows.

The surface of the surface layer 105 of the electrophotographic photoreceptor was photographed at an acceleration voltage of 10 kV using a scanning electron microscope (SEM) ("S-4800", manufactured by JEOL Ltd.). Photographs of the surface layer 105 of the electrophotographic photoreceptor of the present invention at 30,000 times magnification were captured by a scanner at 12 locations in total, 50 mm from each end and three locations at the center in the longitudinal direction of the electrophotographic photoreceptor of the present invention, and four locations at 90 degrees each in the circumferential direction. The particles PAA in the photographic images were binarized using an image processing and analysis device ("LUZEX AP", manufactured by Nireco Corporation).

The area of the particles PAA is S1, and the total area of the areas other than the particles PAA is S2, and the coverage rate S1/(S1+S2) (%) is calculated. The coverage rate is calculated for a total of 10 fields of view, and the average of the obtained coverage rates is regarded as the coverage rate of the particles in the surface layer 105 of the photoreceptor.

<Method for Measuring Circularity of PAA Particles in the Surface Layer of an Electrophotographic Photoreceptor>
The surface of the surface layer 105 of the electrophotographic photoreceptor was photographed at an acceleration voltage of 10 kV using a scanning electron microscope (SEM) ("S-4800", manufactured by JEOL Ltd.). Photographs of the surface layer 105 of the electrophotographic photoreceptor of the present invention, magnified 30,000 times, were captured by a scanner at 12 locations in total, 50 mm from each end and three locations at the center of the electrophotographic photoreceptor in the longitudinal direction, and four locations at 90 degrees each in the circumferential direction. Furthermore, the particles PAA in the photographic images were subjected to image processing using an image processing analyzer ("LUZEX AP", manufactured by Nireco Corporation), and the average value of the circularity for a total of 10 visual fields was calculated to obtain the circularity of the particles PAA.

<Measurement of film thickness of each layer>
The thickness of each layer of the electrophotographic photoreceptor in the examples and comparative examples was measured, except for the charge generating layer, by a method using an eddy current film thickness meter (Fischerscope, manufactured by Fisher Instruments) or a method of converting the specific gravity from the mass per unit area. The film thickness of the charge generating layer was measured by converting the Macbeth density value of the photoreceptor using a calibration curve previously obtained from the Macbeth density value measured by pressing a spectrodensitometer (product name: X-Rite 504/508, manufactured by X-Rite) against the surface of the photoreceptor and the film thickness measured by observing a cross-sectional SEM image.

<Production of Electrophotographic Photoreceptor>
A support, a conductive layer, an undercoat layer, a charge generating layer, a charge transport layer, and a surface layer 105 were prepared by the following methods.

<Preparation of Conductive Layer Coating Solution 1>
An anatase type titanium oxide having an average primary particle size of 200 nm was used as the substrate, _{and a titanium niobium sulfate solution containing 33.7 parts of titanium in terms of TiO2 and 2.9 parts of niobium in terms of Nb2O5 was prepared} . 100 parts of the substrate was dispersed in pure water to prepare a suspension of 1000 parts, which was then heated to 60°C. The titanium niobium sulfate solution and 10 mol/L sodium hydroxide were dropped over 3 hours so that the pH of the suspension was 2 to 3. After the entire amount was dropped, the pH was adjusted to near neutral, and a polyacrylamide-based flocculant was added to settle the solid content. The supernatant was removed, filtered and washed, and dried at 110°C to obtain an intermediate containing 0.1 wt% of organic matter derived from the flocculant in terms of C. This intermediate was calcined in nitrogen at 750°C for 1 hour, and then calcined in air at 450°C to produce titanium oxide particles. The particles thus obtained had an average primary particle size of 220 nm as measured by the above-mentioned particle size measurement method using a scanning electron microscope.

Next, 50 parts of a phenolic resin (phenolic resin monomer/oligomer) (product name: Plyofen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g/cm ² ) serving as a binder material was dissolved in 35 parts of 1-methoxy-2-propanol serving as a solvent to obtain a solution.

60 parts of titanium oxide particles 1 were added to this solution, which was then placed in a vertical sand mill using 120 parts of glass beads having a number-average primary particle size of 1.0 mm as a dispersion medium, and the resultant was subjected to a dispersion treatment for 4 hours under conditions of a dispersion temperature of 23±3° C. and a rotation speed of 1500 rpm (circumferential speed of 5.5 m/s) to obtain a dispersion. The glass beads were removed from this dispersion using a mesh. 0.01 parts of silicone oil (trade name: SH28 PAINT ADDITIVE, manufactured by Dow Corning Toray Co., Ltd.) as a leveling agent and 8 parts of silicone resin particles (trade name: KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., average primary particle size: 2 μm, density: 1.3 g/cm ³ ) as a surface roughness imparting agent were added to the dispersion after the glass beads were removed, and the mixture was stirred, followed by pressure filtration using PTFE filter paper (trade name: PF060, manufactured by Advantec Toyo Co., Ltd.) to prepare a coating solution 1 for a conductive layer.

<Preparation of Coating Solution 1 for Undercoat Layer>
100 parts of rutile-type titanium oxide particles (average primary particle size: 50 nm, manufactured by Teika) were mixed with 500 parts of toluene by stirring, 3.5 parts of vinyltrimethoxysilane (trade name: KBM-1003, manufactured by Shin-Etsu Chemical) were added, and the mixture was dispersed for 8 hours in a vertical sand mill using glass beads having a diameter of 1.0 mm. After removing the glass beads, the toluene was distilled off by vacuum distillation, and the mixture was dried at 120° C. for 3 hours to obtain rutile-type titanium oxide particles that had been surface-treated with an organosilicon compound. When the volume of the obtained titanium oxide particles was a and the average primary particle size of the titanium oxide particles was b [μm], a/b=15.6. The value of a was determined from a microscopic image of a cross section of the electrophotographic photoconductor after production, using a field emission scanning electron microscope (FE-SEM, trade name: S-4800, manufactured by Hitachi High-Technologies Corporation).

A dispersion was prepared by adding 18.0 parts of rutile-type titanium oxide particles that had been surface-treated with the organosilicon compound, 4.5 parts of N-methoxymethylated nylon (product name: Toresin EF-30T, manufactured by Nagase ChemteX), and 1.5 parts of copolymer nylon resin (product name: Amilan CM8000, manufactured by Toray) to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol.

This dispersion was dispersed in a vertical sand mill using glass beads with a diameter of 1.0 mm for 5 hours, and the glass beads were removed to prepare coating solution 1 for the undercoat layer.

<Synthesis of phthalocyanine pigment>
<Synthesis Example 1>
Under a nitrogen flow atmosphere, 100 g of gallium trichloride and 291 g of orthophthalonitrile were added to 1,000 mL of α-chloronaphthalene, and the mixture was reacted at 200° C. for 24 hours, and then the product was filtered. The obtained wet cake was heated and stirred at 150° C. for 30 minutes using N,N-dimethylformamide, and then filtered. The resulting filtrate was washed with methanol and dried, and a chlorogallium phthalocyanine pigment was obtained in a yield of 83%.

20 g of the chlorogallium phthalocyanine pigment obtained by the above method was dissolved in 500 mL of concentrated sulfuric acid and stirred for 2 hours, then added dropwise to a mixed solution of 1700 mL of ice-cooled distilled water and 660 mL of concentrated aqueous ammonia to reprecipitate. This was thoroughly washed with distilled water and dried to obtain a hydroxygallium phthalocyanine pigment.

<Preparation of Coating Solution 1 for Charge Generation Layer>
0.5 parts of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 1, 7.5 parts of N,N-dimethylformamide (product code: D0722, manufactured by Tokyo Chemical Industry Co., Ltd.), and 29 parts of glass beads having a diameter of 0.9 mm were milled at a temperature of 25° C. for 24 hours using a sand mill (BSG-20, manufactured by Imex). At this time, the milling was performed under the condition that the disk rotated 1500 times per minute. The liquid thus treated was filtered with a filter (product number: N-NO.125T, pore size: 133 μm, manufactured by NBC Meshtec) to remove the glass beads. 30 parts of N,N-dimethylformamide were added to this liquid, and then the mixture was filtered, and the filter cake on the filter was thoroughly washed with n-butyl acetate. The washed filter cake was then vacuum dried to obtain 0.45 parts of hydroxygallium phthalocyanine pigment. The obtained pigment contained N,N-dimethylformamide.

Next, 20 parts of the hydroxygallium phthalocyanine pigment obtained by the milling process, 10 parts of polyvinyl butyral (product name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.), 190 parts of cyclohexanone, and 482 parts of glass beads with a diameter of 0.9 mm were dispersed using a sand mill (K-800, manufactured by Igarashi Machine Manufacturing Co., Ltd. (now Imex), disk diameter 70 mm, number of disks 5) at a cooling water temperature of 18°C for 4 hours. This was done under conditions of 1800 rotations per minute of the disk. The glass beads were removed from this dispersion, and 444 parts of cyclohexanone and 634 parts of ethyl acetate were added to prepare coating solution 1 for the charge generating layer.

<Preparation of Coating Solution 1 for Charge Transport Layer>
(Example of Preparation of Charge Transport Layer 1)
Next, the following materials were prepared to prepare a mixed solvent.
Orthoxylene: 25 parts by weight Methyl benzoate: 25 parts by weight Dimethoxymethane: 25 parts by weight

Furthermore, the following materials were dissolved in the mixed solvent to prepare a coating solution 1 for a charge transport layer.
Charge transport material (hole transport material) represented by the following structural formula (C-1): 5 parts by mass Charge transport material (hole transport material) represented by the following structural formula (C-2): 5 parts by mass Polycarbonate (product name: Iupilon Z400, manufactured by Mitsubishi Engineering Plastics Corporation): 10 parts by mass This coating liquid 1 for charge transport layer was dip-coated on the charge generating layer 1 to form a coating film, and the coating film was dried at a drying temperature of 40° C. for 5 minutes to form a charge transport layer 1 having a thickness of 15 μm.

(Example 1 of Preparation of Surface Layer Containing Particles)
The materials shown in Table 1 for forming PAA particles and PAB particles were prepared.

<Preparation of Surface Layer Coating Solution 1>
PAA particles: silica particles ("QSG-170", manufactured by Shin-Etsu Chemical Co., Ltd.): 2.5 parts by mass PAB particles: silica particles ("QSG-80", manufactured by Shin-Etsu Chemical Co., Ltd.): 2.5 parts by mass Monomer 1 having a polymerizable functional group (above structural formula (2-1)): 0.75 parts by mass Monomer 2 having a polymerizable functional group (above structural formula (3-1)): 0.75 parts by mass Siloxane-modified acrylic compound (product name: Simac US270, manufactured by Toa Gosei Co., Ltd.): 0.1 parts by mass 1-propanol: 100.0 parts by mass Cyclohexane: 100.0 parts by mass The above ingredients were mixed and stirred for 6 hours with a stirrer to prepare coating solution 1 for surface layer.

<Preparation of Surface Layer Coating Solutions 2 to 25>
Surface layer coating solutions 2 to 25 were prepared in the same manner as in preparation of surface layer coating solution 1, except that the types and amounts of particles PAA, particles PAB, and other particles were changed as shown in Table 2.

<Example of Manufacturing Electrophotographic Photoreceptor 1>
<Support>
An aluminum cylinder having a diameter of 24 mm and a length of 257 mm was used as a support (cylindrical support).

<Conductive Layer>
The conductive layer coating solution 1 was dip-coated onto the above-mentioned support to form a coating film, and the coating film was heated at 150° C. for 30 minutes to be cured, thereby forming a conductive layer having a thickness of 22 μm.

<Undercoat layer>
The undercoat layer coating solution 1 was dip-coated onto the above-mentioned conductive layer to form a coating film, which was then heated at 100° C. for 10 minutes to be cured, thereby forming an undercoat layer with a thickness of 1.8 μm.

<Charge Generation Layer>
The undercoat layer was dip-coated with the charge generating layer coating solution 1 to form a coating film, and the coating film was dried by heating at a temperature of 100° C. for 10 minutes to form a charge generating layer having a thickness of 0.20 μm.

<Charge Transport Layer>
The charge transport layer coating solution 1 was dip-coated on the charge generating layer to form a coating film, and the coating film was dried by heating at a temperature of 120° C. for 30 minutes to form a charge transport layer having a thickness of 21 μm.

<Surface layer>
The coating solution 1 for surface layer was applied by dip coating on the charge transport layer to form a coating film, and the coating film was heated at a temperature of 50°C for 5 minutes. Then, under a nitrogen atmosphere, the coating film was irradiated with an electron beam for 2.0 seconds while rotating the support (irradiated body) at a speed of 300 rpm under the conditions of an acceleration voltage of 65 kV and a beam current of 5.0 mA. The dose was 15 kGy. Then, under a nitrogen atmosphere, the temperature of the coating film was raised to 120°C. The oxygen concentration from the electron beam irradiation to the subsequent heat treatment was 10 ppm.

Next, the coating was naturally cooled in the atmosphere until the temperature of the coating reached 25°C, after which it was heat-treated for 30 minutes under conditions that brought the temperature of the coating to 120°C, forming a surface layer 105 with a thickness of 1.0 μm. The physical properties of the resulting electrophotographic photoreceptor are shown in Table 3.

<Preparation Examples of Electrophotographic Photoreceptors 2 to 25>
Electrophotographic photoreceptors 2 to 25 were produced in the same manner as in the production of electrophotographic photoreceptor 1, except that the surface layer coating liquid 1 was changed as shown in Table 2. The physical properties of the obtained electrophotographic photoreceptors 2 to 25 are shown in Table 3.

Next, the developer, toner, and transfer promoting particles used in this embodiment will be described in detail.
(Developer)
In this embodiment, a mixture of toner and an external additive A, which is a transfer-promoting particle, is used as the developer. The transfer-promoting particle is a particle that has a role of reducing the adhesive force by being present between the toner and other members.

The number average particle diameter R of the primary particles of the external additive A is preferably 30 nm or more and 1000 nm or less. When R is 30 nm or more, it is easy to develop a spacer effect between other members. On the other hand, if R is too large, the transfer-promoting particles are easily affected by electrostatic forces generated by the potential difference between the developing roller 41 and the photosensitive drum 1. Therefore, when the transfer-promoting particles are negatively charged, the transfer-promoting particles are attracted to the developing roller 41 side by electrostatic forces, and it becomes difficult to supply the transfer-promoting particles from the toner on the developing roller 41 to the photosensitive drum 1. Therefore, it is preferable that the particle diameter of the transfer-promoting particles is 1000 nm or less, which is less susceptible to electrostatic forces. The particle diameter is more preferably 40 nm or more and 400 nm or less. The particle diameter is more preferably 50 nm or more and 200 nm or less.

There are no particular limitations on the external additive A, so long as the number-average particle diameter R of the primary particles is 30 nm or more and 1000 nm or less, and various organic or inorganic fine particles can be used. From the viewpoint of easily imparting fluidity and being easily negatively charged like the toner base particles, it is preferable that the external additive A contains silica fine particles. The content of silica fine particles in the external additive A is preferably 50 mass% or more, and it is more preferable that the external additive A is silica fine particles.

Examples of organic or inorganic fine particles other than silica fine particles include the following.
(1) Fluidity imparting agents: alumina fine particles, titanium oxide fine particles, carbon black and carbon fluoride.
(2) Abrasives: fine particles of metal oxides (fine particles of strontium titanate, cerium oxide, alumina, magnesium oxide, chromium oxide, etc.), fine particles of nitrides (fine particles of silicon nitride, etc.), fine particles of carbides (fine particles of silicon carbide, etc.), fine particles of metal salts (fine particles of calcium sulfate, barium sulfate, calcium carbonate, etc.).
(3) Lubricants: fine particles of fluororesin (fine particles of vinylidene fluoride, polytetrafluoroethylene, etc.), fine particles of fatty acid metal salts (fine particles of zinc stearate, calcium stearate, etc.).
(4) Charge-controlling fine particles: fine particles of metal oxides (fine particles of tin oxide, titanium oxide, zinc oxide, alumina, etc.), carbon black.

The silica fine particles and the organic or inorganic fine particles may be subjected to a hydrophobic treatment to improve the flowability of the toner and to uniformly charge the toner particles.

Examples of treatment agents for the hydrophobic treatment include unmodified silicone varnish, various modified silicone varnishes, unmodified silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organosilicon compounds, and organotitanium compounds. These treatment agents may be used alone or in combination.

The silica fine particles can be any known silica fine particles, and may be either dry silica fine particles or wet silica fine particles. Preferably, the silica fine particles are wet silica fine particles obtained by the sol-gel method (hereinafter, also referred to as sol-gel silica).

Figure 6 is an enlarged view of the developer used in this embodiment. As shown in Figure 6, the developer in this embodiment has external additive A, which is a transfer-promoting particle, disposed on the surface of the toner T.

A larger number of transfer-promoting particles that coat the toner is preferable from the viewpoint of reducing adhesion. However, adding too many transfer-promoting particles increases the risk of contaminating components inside the image forming device 100, so it is preferable to adjust the amount according to the configuration.

(Method of measuring number average particle size R of primary particles of external additive)
Using a scanning electron microscope "Hitachi Ultra High Resolution Field Emission Scanning Electron Microscope S-4800" (Hitachi High-Technologies Corporation), the toner is observed in a field of view magnified up to 50,000 times, and the external additive particles are photographed. From the photographed image, 100 external additive particles are randomly selected, and the major axis of the primary particles of the target external additive particles is measured, and the arithmetic average value thereof is taken as the number average particle size R. The observation magnification is appropriately adjusted depending on the size of the external additive particles.

(Production Example of Toner Particle 1)
<Preparation of aqueous medium 1>
Into a reaction vessel equipped with a stirrer, a thermometer, and a reflux tube, 650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (Rasa Kogyo Co., Ltd., 12-hydrate) were added, and the mixture was kept at 65° C. for 1.0 hour while purging with nitrogen.

A calcium chloride aqueous solution in which 9.2 parts of calcium chloride (dihydrate) was dissolved in 10.0 parts of ion-exchanged water was added all at once while stirring at 15,000 rpm using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare an aqueous medium containing a dispersion stabilizer. Furthermore, 10% by mass of hydrochloric acid was added to the aqueous medium to adjust the pH to 5.0, and aqueous medium 1 was obtained.

<Preparation of polymerizable monomer composition>
The above materials were put into an attritor (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.), and further dispersed at 220 rpm for 5.0 hours using zirconia particles having a diameter of 1.7 mm, and then the zirconia particles were removed to prepare a colorant dispersion.

on the other hand,
Styrene: 20.0 parts by mass; n-Butyl acrylate: 20.0 parts by mass; Crosslinking agent (divinylbenzene): 0.3 parts by mass; Saturated polyester resin: 5.0 parts by mass (polycondensate of propylene oxide modified bisphenol A (2 mole adduct) and terephthalic acid (molar ratio 10:12), glass transition temperature (Tg) 68°C, weight average molecular weight (Mw) 10,000, molecular weight distribution (Mw/Mn) 5.12)
Fischer-Tropsch wax (melting point 78° C.): 7.0 parts by mass This material was added to the colorant dispersion and heated to 65° C., and then uniformly dissolved and dispersed at 500 rpm using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a polymerizable monomer composition.

<Granulation process>
The temperature of the aqueous medium 1 was adjusted to 70° C., and the rotation speed of the T.K. homomixer was kept at 15,000 rpm, while the polymerizable monomer composition was charged into the aqueous medium 1, and 10.0 parts by mass of t-butyl peroxypivalate, a polymerization initiator, was added. Granulation was continued for 10 minutes while maintaining the stirring speed at 15,000 rpm.

<Polymerization process and distillation process>
After the granulation step, the agitator was replaced with a propeller agitator blade, and polymerization was carried out for 5.0 hours while stirring at 150 rpm and maintaining the temperature at 70° C., and then the temperature was raised to 85° C. and maintained at that temperature for 2.0 hours. Thereafter, the reflux tube of the reaction vessel was replaced with a cooling tube, and the obtained slurry was heated to 100° C. to carry out distillation for 6 hours, thereby distilling off the unreacted polymerizable monomer, and a resin particle dispersion was obtained.

(Washing process and drying process)
The resin particle dispersion was cooled, and hydrochloric acid was added to the resin particle dispersion to adjust the pH to 1.5 or less, and the mixture was left for 1.0 hour while stirring. Thereafter, the mixture was subjected to solid-liquid separation using a pressure filter to obtain a toner cake. The obtained toner cake was reslurried with ion-exchanged water to make a dispersion again, and then subjected to solid-liquid separation using the above-mentioned filter to obtain a toner cake. The obtained toner cake was transferred to a thermostatic chamber at 40°C, and was dried and classified for 72 hours to obtain toner particles.

(Production Example of External Additive A)
The external additive A was manufactured as follows. 150 parts of 5% ammonia water was added to a 1.5L glass reaction vessel equipped with a stirrer, a dropping nozzle, and a thermometer to prepare an alkaline catalyst solution. After adjusting the alkaline catalyst solution to 50°C, 100 parts of tetraethoxysilane and 50 parts of 5% ammonia water were dropped simultaneously while stirring, and reacted for 8 hours to obtain a silica microparticle dispersion. Thereafter, the obtained silica microparticle dispersion was dried by spray drying and crushed with a pin mill to obtain silica microparticles with a number average particle diameter of 100 nm as the external additive A. Here, by appropriately changing the above manufacturing conditions, external additive A (R = 100 nm) and external additive B (R = 10 nm) with different number average particle diameters R of the primary particles were obtained.

(Example of manufacturing developer)
100.00 parts of toner particles 1 and 1.00 parts of additive A and additive B were charged into a Henschel mixer (FM10C type manufactured by Nippon Coke & Engineering Co., Ltd.) with water at 7°C passing through the jacket. Next, after the water temperature in the jacket stabilized at 7°C ± 1°C, the mixture was mixed for 10 minutes with the peripheral speed of the rotating blade set to 38 m/sec. During the mixing, the amount of water passing through the jacket was appropriately adjusted so that the temperature inside the tank of the Henschel mixer did not exceed 25°C. The obtained mixture was sieved through a mesh with an opening of 75 μm to obtain a developer.

外添剤Ｂは現像剤の流動性を向上させる目的で外添されている。 The physical properties of the developer are shown in Table 4.

The external additive B is added to improve the fluidity of the developer.

When the manufactured developers were observed using an SEM, it was confirmed that the external additives were arranged on the toner particles as transfer-promoting particles. The average number of external additive particles coated on each toner particle was approximately 500 particles of external additive B in developer 1, and approximately 500 particles of external additive A and approximately 500 particles of external additive B in developer 2.

(Verification experiment)
Next, a comparison was made between the amount of developer adhering to the charging roller and the effect on the image in the present embodiment and a comparative example, which was carried out to verify the effect of the present embodiment. The results are described below. The configurations verified are shown in Table 5.

The difference between the comparative example and this embodiment is the particle size of the external additive. In the comparative example, an image is formed using developer 1 in which only external additive B (R=10 nm) is externally added to toner particles 1, while in this embodiment, an image is formed using developer 2 in which external additive A (R=100 nm) and external additive B (R=10 nm) are externally added to toner particles 1.

Image B to be passed through is shown in Figure 7. It is a combination of a cyan (C) vertical solid image (density 1.40) and a horizontal halftone image (density 0.20). An X-rite 504A (X-Rite, Inc.) is used as the density measuring device. The measurement color mode is All, and the density measurement status is A.

In the area where the vertical solid image is formed, the transfer residual toner adheres to the charging roller 2. As a result, the charging performance of the charging roller 2 changes step by step. In the first stage, when the transfer residual toner begins to adhere to the charging roller 2, the charge (discharge) is concentrated on the part of the charging roller 2 that is visible through the gap where the transfer residual toner adheres, so the potential of the photosensitive drum 1 becomes high. Subsequently, the amount of transfer residual toner adheres to the charging roller 2 increases, and in the second stage, when the charge roller 2 is covered with the transfer residual toner, the charging performance decreases, so the potential of the photosensitive drum 1 becomes low. In the case of a paper passing test of about 50 sheets as described later in this embodiment, the amount of transfer residual toner progresses in a state where it is low, so the photosensitive drum remains in a state where the potential is high as in the first stage, and does not reach the second stage. In this way, when the electrostatic latent image is formed by the exposure unit 3, if the potential of the photosensitive drum 1 is higher than normal, the potential of the electrostatic latent image also becomes higher than normal, so the amount of developer developed decreases and the density of the image becomes low. Of course, depending on the conditions, it may progress from the first stage to the second stage.

Halftone images are particularly susceptible to changes in image density due to changes in potential. In this example, a horizontal halftone image was formed after a vertical solid image. The density of the vertical solid portion (encircled by the dashed line) where residual toner had adhered to the charging roller 2, and the horizontal halftone portion where no residual toner had adhered, were then measured. The difference between these values was then taken to confirm the effect on density caused by the adhesion of residual toner to the charging roller 2.

This image B was printed on 50 sheets of A4 paper (GF-C081, manufactured by Canon) in succession, and the change in density difference was compared between the comparative example and this embodiment. After the printing, a photograph was taken of the vertical solid stripe-forming portion of the charging roller 2, and the state of developer adhesion was compared. In this embodiment, the amount of transfer residual toner was relatively small, for example, the fog density was about 5%. An example of a method for measuring the fog density is as follows: first, the image forming apparatus is stopped after the vertical solid stripe image in FIG. 7 has passed through the primary transfer section. Then, the vertical solid stripe image remaining on the photosensitive drum 1 is taped with polyester tape No. 5511 (NICHIBAN Co., Ltd.) and pasted on A4 paper (GF-C081, manufactured by Canon). Next, the vertical solid stripe image portion on the polyester tape No. 5511 pasted on the GF-C081 is measured with an amber filter of a reflection densitometer TC-6DS/A30 (TOKYO DENSHOKU Co., Ltd.), and a first reflection density value is obtained. Next, the new polyester tape No. 5511
is attached to GF-C081 and measured with a reflection densitometer TC-6DS/A30 to obtain the normal reflection density value (second reflection density value) of polyester tape No. 5511. Finally, the fog density is obtained by subtracting the first reflection density value from the second reflection density value.

FIG. 8 shows the result of measuring the density difference between the vertical solid portion and the portion other than the vertical solid portion when 50 sheets are passed continuously. The density difference is the result of subtracting the density of the portion other than the vertical solid portion from the density of the vertical solid portion. For example, if the density of the horizontal halftone band of the vertical solid portion where the developer adheres to the charging roller 2 is lighter than the horizontal halftone band of the portion other than the vertical solid portion, the density difference will be a negative result. The dotted line is the comparative example, and the solid line is the present embodiment. In the comparative example, it can be seen that the density difference increases in the negative direction as the sheets are passed continuously. In the present embodiment, it can be seen that the density difference does not become negative with the continuous passing of sheets, but becomes slightly positive. Here, according to the inventor's study, it has been found that if the density difference between the vertical solid portion and the portion other than the vertical solid portion is within ±0.02, almost no adverse effects are observed in the printed image. Therefore, unlike the comparative example, it can be seen that the configuration of the present embodiment can suppress image adverse effects.

Figure 9 shows a schematic diagram of the result of taking photographs of the vertical solid portion of the charging roller 2 in the comparative example (Figure 9(a)) and the embodiment (Figure 9(b)) after 50 sheets of paper were passed continuously. In the comparative example, the cyan (C) developer of the transfer residual toner adheres to the vertical solid portion of the charging roller 2, whereas in this embodiment, almost no developer of the transfer residual toner adheres.

The reason for the above results is presumed to be as follows.
In the comparative example, the adhesion between the photosensitive drum 1 and the developer 1 is reduced due to the effect of the particles of the surface layer 105 of the photosensitive drum 1. However, the particle diameter of the external additive B is as small as 10 nm, and it is hidden in the unevenness of the surface of the toner particle 1, so the contact area between the surface of the toner particle 1 and the surface of the charging roller 2 increases, and the adhesion between the charging roller 2 and the developer 1 is not reduced, and the developer 1 adheres to the charging roller 2 by the paper passing. Therefore, the concentration difference increases in the negative direction as the paper passes. On the other hand, in this embodiment, the particle diameter of the external additive A is 100 nm, so it is not hidden in the unevenness of the surface of the toner particle 1, and not only the adhesion between the photosensitive drum 1 and the developer 2 but also the adhesion between the charging roller 2 and the developer 2 is reduced. Since the external additive A is interposed between the developer 2 and the charging roller 2, the adhesion of the developer 2 to the charging roller 2 is suppressed. Therefore, the density difference does not become negative due to the paper passing. Instead, the transfer residual toner that could not be collected by the developing roller 41 is transferred to the horizontal band halftone, so it becomes slightly positive.

The results of the adhesive force calculations used as reference when arriving at the above inference are shown below.
Representative forces acting on the developer particles include electrostatic force, gravity, van der Waals (intermolecular) force, liquid bridge force, etc. Because it is very difficult to quantitatively measure and calculate these forces, here we will qualitatively calculate Coulomb force as an electrostatic force and van der Waals (intermolecular) force as a non-electrostatic force, and use them as a reference for inferring the mechanism.

The calculation is performed assuming a model in which the developer of the residual toner after transfer is nipped between the photosensitive drum 1 and the charging roller 2. The calculation results are shown in Fig. 10. The details of the calculation will be described below.
The Coulomb force Fe [N] is generally expressed by the following equation (7).
Fe = qE (7)
q is the amount of charge [C] and E is the electric field [V/m].

For example, if the charge amount of the residual toner developer is −10 μC/g, the particle size of the developer is 5.5 μm, and the specific gravity of the developer is 1, then the charge amount q of one developer is 8.7×10 ⁻¹⁶ C.

Next, if the potential difference between the photosensitive drum 1 and the charging roller 2 is 1050 [V] and the distance between the photosensitive drum 1 and the charging roller 2 is 5.5 [μm], which is the same as the particle size of the developer, the electric field E is 1.9×10 ⁸
V/m].

Therefore, the Coulomb force Fe acting on one developer is 170 nN. The Coulomb force Fe acts as a force to pull the developer away from the charging roller 2.

The van der Waals (intermolecular) force Fv is generally expressed by the following equation (8).
Fv = Ad / (12z ² ) (8)
A is the Hammerker constant (A=1×10 ⁻¹⁹ ), d is the equivalent particle diameter [m], and z is the separation distance between particles [m] (0.4 nm is used when the particle surfaces are smooth).
d = Dp1 × Dp2 / (Dp1 + Dp2) ... (9)
Dp1 is the diameter of particle 1, and Dp2 is the diameter of particle 2. If Dp2 is set to infinity, then
d = Dp1 ... (10)
and can be regarded as the force between particle 1 and the plate.

First, assuming a comparative example, we calculate the van der Waals (intermolecular) force Fv that occurs between the developer, the photosensitive drum 1, and the charging roller 2.

For example, if the particle size of the developer is 5.5 [μm] and the particle size of the surface layer of the photosensitive drum 1 is 170 [nm], then from equations (8) and (9), the van der Waals (intermolecular) force Fv generated between one particle of developer and the particles in the surface layer of the photosensitive drum 1 is 8.6 [nN].

If we consider the charging roller 2 to be a flat plate, then from equations (8) and (10), the van der Waals (intermolecular) force Fv generated between one developer particle and the charging roller 2 is 286 nN.

In the comparative example, the van der Waals (intermolecular) force (8.6 [nN]) generated between the developer and the surface particles of the photosensitive drum 1 is much larger than the van der Waals (intermolecular) force (286 [nN]) generated between the developer and the charging roller 2 (assuming that the toner particles 1 and the charging roller 2 are in contact because the particle size of the external additive B is small). In addition, even when the effect of the Coulomb force Fe (170 [nN]) is taken into account, the van der Waals (intermolecular) force generated between the developer and the charging roller 2 is large, so when the developer is nipped between the photosensitive drum 1 and the charging roller 2, most of the developer adheres to the charging roller 2.

Next, we calculate the van der Waals (intermolecular) force Fv assuming a developer with transfer-promoting particles on the surface of the toner particles, which is a feature of this embodiment.

If the particle size of the transfer-promoting particles on the surface of the developer is 100 [nm], the van der Waals (intermolecular) force Fv generated between the transfer-promoting particles on the surface of the developer and the particles in the surface layer of the photosensitive drum 1 is 3.3 [nN]. The van der Waals (intermolecular) force Fv generated between the transfer-promoting particles on the surface of the developer and the charging roller 2 is 5.2 [nN].

In this embodiment, the van der Waals (intermolecular) force Fv (5.2 [nN]) generated between the charging roller 2 due to the presence of transfer-promoting particles on the surface of the developer is very small compared to the comparative example. It is approximately the same as the van der Waals (intermolecular) force (3.3 [nN]) generated between the transfer-promoting particles on the surface of the developer and the particles on the surface layer of the photosensitive drum 1. Furthermore, the developer is pulled away from the charging roller 2 by the Coulomb force Fe (170 [nN]) and adheres to the photosensitive drum 1, so when the developer is nipped between the photosensitive drum 1 and the charging roller 2, most of the developer adheres to the photosensitive drum 1.

Figure 11 shows the van der Waals (intermolecular) force Fv that occurs between the charging roller 2 when the particle size of the transfer-promoting particles on the surface of the developer is varied from 30 to 1000 nm. The larger the particle size, the greater the van der Waals (intermolecular) force Fv, so it is thought that the larger the particle size of the transfer-promoting particles, the weaker the effect of suppressing adhesion of the developer to the charging roller 2. However, even if the particle size of the transfer-promoting particles is 1000 nm, the van der Waals (intermolecular) force Fv is 52 nN, which is not extremely large compared to the van der Waals (intermolecular) force Fv and Coulomb force Fe that occur between the developer and the particles on the surface of the photosensitive drum 1, so the effect of suppressing adhesion of the developer to the charging roller 2 is exerted.

Since the amount of developer adhering to the charging roller 2 can be controlled to some extent by the particle size of the transfer-promoting particles, it is preferable to determine the particle size of the transfer-promoting particles according to the configuration of the image forming apparatus. As shown in Fig. 8, if the transfer residue adheres to the charging roller 2, it will appear as a low density in the subsequent image, and if the transfer residue does not adhere to the charging roller 2, it will appear in the subsequent image if the developing roller 41 cannot collect all the developer. The developer adhering to the charging roller 2 can be peeled off by applying a positive potential to the charging roller 2 after the end of image formation or between sheets, so the particle size of the transfer-promoting particles may be determined according to which is to be prioritized.

The optimal particle size of developer A can also be determined from the particle diameter DA of the surface layer 105 of the photosensitive drum 1 and the average value of the distance between the centers of gravity of the convex portions resulting from particles in the range of DA ± 20 nm. As explained above, if the particle size of developer A is too small, the contact area between the surface of the toner particle 1 and the surface of the charging roller 2 increases, and the developer A cannot function as a spacer with the charging roller 2. Furthermore, if the particle size of developer A is too large compared to the particle diameter DA of the surface layer 105 of the photosensitive drum 1 and the average value of the distance between the centers of gravity of the convex portions resulting from particles in the range of DA ± 20 nm, the contact area with the photosensitive drum 1 increases, and developer A becomes more likely to detach from the toner surface. Therefore, it is better that the particle size of developer A is smaller than the average value of the distance between the centers of gravity of the convex portions resulting from particles in the range of the particle diameter DA ± 20 nm of the surface layer 105 of the photosensitive drum 1.

[Example 2]
A description will now be given of Example 2 of the present invention. In Example 2 of the present invention, the composition of the developer is different from that in Example 1, and the organosilicon polymer forms convex portions on the surfaces of the toner base particles.

In typical toners with externally added fine particles such as silica, as described in Example 1, the adhesive force between the toner and the fine particles is strong, so many of the fine particles remain on the toner surface. The effect of having fine particles on the toner surface to suppress toner adhesion to other members was described in Example 1. In Example 2, a method of suppressing toner adhesion by actively detaching fine particles attached to the toner from the toner and causing the fine particles to adhere to the other members themselves is described. Note that matters that are not specifically described in Example 2 are the same as those in Example 1, and explanations will be omitted.

(Developers, toners, transfer-promoting particles)
In this embodiment, a mixture of toner and transfer-promoting particles, that is, an external additive A, was used as the developer. The toner is made up of toner particles containing a release agent and an organosilicon polymer on the surface of the toner particles.

The organosilicon polymer has a T3 unit structure represented by R-Si(O1/2)3, where R represents an alkyl group or a phenyl group having 1 to 6 carbon atoms, and the organosilicon polymer forms convex portions on the surface of the toner base particle.

The protrusions are characterized by being in surface contact with the surface of the toner base particle, and this surface contact is expected to have a significant effect in inhibiting the movement, detachment, and embedding of the protrusions.

The degree of surface contact is explained using the schematic diagrams of the protrusions shown in Figures 12, 13, 14, and 15. Reference numeral 61 in Figure 12 is a cross-sectional image of a toner particle showing approximately 1/4 of the toner particle, reference numeral 62 is a toner particle, reference numeral 63 is the surface of the toner base particle, and reference numeral 64 is a protrusion. The cross-section of the toner particle can be observed using a scanning transmission electron microscope (hereinafter also referred to as STEM) described later.

A cross-sectional image of the toner is observed, and a line is drawn along the periphery of the surface of the toner base particle. A horizontal image is then created based on this line along the periphery. In the horizontal image, the length of the line along the periphery in the portion where the convex portion and the toner base particle form a continuous interface is defined as the convex width w. The maximum length of the convex portion in the normal direction of the convex width w is defined as the convex diameter D, and the length from the apex of the convex portion to the line along the periphery in the line segment that forms the convex diameter D is defined as the convex height H.

In Figures 13 and 15, the convex diameter D and the convex height H are the same, and in Figure 14, the convex diameter D is greater than the convex height H.

Figure 15 shows a schematic representation of the adhesion state of particles similar to bowl-shaped particles, which are hemispherical particles with a concave center, obtained by crushing or breaking hollow particles.

In Figure 15, the convex width W is the total length of the organosilicon polymer in contact with the toner base particle surface. In other words, the convex width W in Figure 15 is the sum of W1 and W2.

The number average value of the convex height H is 30 nm or more and 300 nm or less, and preferably 30 nm or more and 200 nm or less. When the number average value of the convex height H is 30 nm or more, a spacer effect occurs between the surface of the toner base particle and the transfer member, and the transferability is significantly improved. On the other hand, when the number average value of the convex height H is 300 nm or less, the effect of suppressing movement, detachment, and embedding is significant, and high transferability is maintained even during long-term use. A cumulative distribution of the convex height H is taken for the convex portion having a convex height H of 30 nm or more and 300 nm or less. When the convex height H that corresponds to 80% by number of the smallest convex heights H is H80, H80 is preferably 65 nm or more and 120 nm or less, and more preferably 75 nm or more and 100 nm or less. By setting H80 in the above range, the transferability can be further improved.

The number-average particle size R of the primary particles of the external additive A is preferably 30 nm or more and 1200 nm or less. When R is 30 nm or more, a spacer effect is exerted between the transfer member and the external additive A, and high transferability is exhibited. In addition, the larger R is, the more the transferability tends to improve. On the other hand, when R is more than 1200 nm, the fluidity of the toner decreases, and image unevenness is easily generated.

It is preferable that the ratio of the number average particle diameter R of the primary particles of the external additive A to the number average value of the convex height H is 1.00 or more and 4.00 or less. When the ratio [(number average particle diameter R of the primary particles of the external additive A)/(number average value of the convex height H)] is in the above range, it is possible to achieve both excellent transferability and low-temperature fixability that can withstand a long life.

When the number average value of the convex height H is 30 nm, which is the minimum value, if R is 30 nm or more, a spacer effect can be exerted between the transfer member and the convexity, improving transferability. This is thought to be because the external additive A is substituted in places where there are no convexities due to the effects of detachment, etc., exerting the spacer effect. In other words, if R is less than 30 nm, the spacer effect is difficult to exert.

The adhesion rate of external additive A to the toner particle surface is preferably 0% or more and 20% or less, and more preferably 0% or more and 10% or less. When the adhesion rate is in the above range, external additive A can move easily on the surface of the toner particles, and the transferability can be further improved by the protrusion substitution effect. In the fixing process in which the toner is fixed to the fixing member, an appropriate amount of release agent seeps out from the toner base particles, improving the separation performance between the fixing member and the paper.

The toner surface is observed by a scanning electron microscope to obtain a reflected electron image of 1.5 μm square of the toner surface. When the reflected electron image is binarized so that the organosilicon polymer part in the reflected electron image becomes a bright part, the area ratio of the bright part area of the image to the total area of the image (hereinafter also simply referred to as the area ratio of the bright part area) is 30.0% or more and 75.0% or less. The area ratio of the bright part area of the image is preferably 35.0% or more and 70.0% or less. The higher the area ratio of the bright part area, the higher the presence ratio of the organosilicon polymer on the toner base particle surface. When the area ratio of the bright part area is higher than 75.0%, the presence ratio of the component derived from the toner base particle on the toner base particle surface is low, the release agent is less likely to bleed out from the toner base particle, and the thin paper is likely to wrap around the fixing device during low-temperature fixing. On the other hand, when the area ratio of the bright part area of the image is less than 30.0%, the presence ratio of the component derived from the toner base particle on the toner base particle surface is high. In other words, the exposed area of the components derived from the toner base particles on the toner base particle surface is large, and the transferability is reduced in the initial stage of use. The area ratio of the bright area of the image is hereinafter also referred to as the coverage rate of the organosilicon polymer on the surface of the toner base particle.

External additive A is not particularly limited as long as the number average particle diameter R of the primary particles is 30 nm or more and 1000 nm or less, and various organic or inorganic fine particles can be used. From the viewpoint of easily imparting fluidity and being easily negatively charged like the toner mother particles, external additive A preferably contains silica fine particles. The content of silica fine particles in external additive A is preferably 50 mass% or more, and external additive A is more preferably silica fine particles. The content of external additive A in the toner is preferably 0.02 mass% or more and 5.00 mass% or less, and more preferably 0.05 mass% or more and 3.00 mass% or less.

Figure 16 is an enlarged view of the developer used in this embodiment. As shown in Figure 16, the developer in this embodiment has a toner surface on which numerous protrusions of an organosilicon polymer are formed, and external additive A, which is a transfer-promoting particle, is placed.

The convex spacing G and convex height H on the toner surface shown in Figure 16 can be measured using a scanning transmission electron microscope (hereinafter referred to as STEM), which will be described later. The convex spacing G and convex height H can also be measured with a scanning probe microscope (hereinafter referred to as SPM). The SPM is equipped with a probe, a cantilever that supports the probe, and a displacement measurement system that detects the bending of the cantilever, and detects the atomic force (attractive or repulsive force) between the probe and the sample to observe the shape of the sample surface.

If the convex spacing G is larger than the transfer-promoting particles, the transfer-promoting particles will come into contact with the toner matrix when placed between the convex portions, and the adhesive force Ft between the transfer-promoting particles and the toner will increase, making it difficult for the transfer-promoting particles to transfer from the toner to the charging roller 2. Therefore, it is preferable that the number-average convex spacing G is smaller than the number-average particle size of the transfer-promoting particles.

In addition, if the convex height H is greater than the particle size of the transfer-promoting particles, the convex portion will come into contact with the charging roller 2 before the transfer-promoting particles, making it difficult for the transfer-promoting particles to come into contact with the charging roller 2, and making it difficult for the transfer-promoting particles to transfer from the toner to the charging roller 2. For this reason, it is preferable that the number-average convex height H is smaller than the number-average particle size of the transfer-promoting particles.

However, as mentioned above, it is preferable that the adhesive force Ft between the transfer-promoting particles and the toner is smaller than the adhesive force Fc between the transfer-promoting particles and the charging roller 2. Therefore, it is preferable to select a material for the transfer-promoting particles that reduces the adhesive force Ft of the transfer-promoting particles to the toner. For example, as in this embodiment, when the convex portions on the toner surface are formed of a silica-based material such as an organic silica polymer, it is preferable to select a silica-based material with a similar material composition to the convex portions as the material for the transfer-promoting particles, in order to reduce the adhesive force between the convex portions and the transfer-promoting particles.

(Method of measuring physical properties of developer)
Various measurement methods will be described below.

<Method of observing a cross section of a toner using a scanning transmission electron microscope (STEM)>
The cross section of the toner observed by a scanning transmission electron microscope (STEM) is prepared as follows. The procedure for preparing the cross section of the toner is described below. When organic or inorganic fine particles are externally added to the toner, the organic or inorganic fine particles are removed by the following method or the like, and the toner is used as a sample.

160 g of sucrose (Kishida Chemical) is added to 100 mL of ion-exchanged water, and dissolved in a hot water bath to prepare a concentrated sucrose solution. 31 g of the concentrated sucrose solution and 6 mL of Contaminon N (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) are placed in a centrifuge tube (50 mL capacity). 1.0 g of toner is added to this, and the toner clumps are loosened with a spatula or the like. The centrifuge tube is shaken at 300 spm (strokes per minute) for 20 minutes in a shaker (AS-1N, sold by AS ONE Corporation). After shaking, the solution is transferred to a glass tube (50 mL) for a swing rotor, and separated in a centrifuge (H-9R, manufactured by Kokusan Co., Ltd.) at 3,500 rpm for 30 minutes. This operation separates the toner particles from the external additives. Visually check that the toner particles and the aqueous solution are sufficiently separated, and collect the toner particles that have separated to the top layer with a spatula or similar. After filtering the collected toner particles with a vacuum filter, dry them in a dryer for at least one hour to obtain a sample for measurement. This operation is carried out multiple times to ensure the required amount.

In addition, whether or not the convex portion contains an organosilicon polymer is confirmed by combining elemental analysis using energy dispersive X-ray analysis (EDS).

Toner is spread onto a cover glass (Matsunami Glass Co., Ltd., square cover glass; square No. 1) in a single layer, and an osmium (Os) plasma coater (Filgen, OPC80T) is used to apply an Os film (5 nm) and a naphthalene film (20 nm) to the toner as a protective film. Next, a PTFE tube (outer diameter 3 mm (inner diameter 1.5 mm) x 3 mm) is filled with photocurable resin D800 (JEOL Ltd.), and the cover glass is gently placed on top of the tube so that the toner is in contact with the photocurable resin D800. In this state, light is irradiated to harden the resin, and then the cover glass and tube are removed to form a cylindrical resin with the toner embedded in the outermost surface. Using an ultrasonic ultramicrotome (Leica, UC7), a cutting speed of 0.6 mm/s is used to cut from the outermost surface of the cylindrical resin to the length of the toner radius (for example, 4.0 μm when the weight average particle size (D4) is 8.0 μm) to expose the cross section of the center of the toner.

Next, the toner is cut to a thickness of 100 nm to produce a thin sample of the toner cross section. By cutting in this manner, a cross section of the center of the toner can be obtained.

A JEM-2800 manufactured by JEOL was used as the scanning transmission electron microscope (STEM). The probe size of the STEM was 1 nm, and images were acquired with an image size of 1024 x 1024 pixels. The bright field image was acquired by adjusting the contrast of the Detector Control panel to 1425, the brightness to 3750, and the contrast of the Image Control panel to 0.0, the brightness to 0.5, and the gamma to 1.00. The image magnification was 100,000 times, and the image was acquired so that it covered about one-quarter to one-half of the circumference of the cross section of one toner particle, as shown in Figure 12.

The obtained STEM image is subjected to image analysis using image processing software (ImageJ (available from https://imagej.nih.gov/ij/)) and the convex portions containing the organosilicon polymer are measured. The measurement is performed on 30 convex portions arbitrarily selected from the STEM image. Whether or not the convex portions contain the organosilicon polymer is confirmed by a combination of elemental analysis using a scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDS). First, a line is drawn along the periphery of the toner base particle using a line drawing tool (select Segmented line in the Strong tab). Parts where the organosilicon polymer convex portions are buried in the toner base particle are connected smoothly with a line, assuming that they are not buried.
The image is converted to a horizontal image based on this line (select Selection on the Edit tab, change line width to 500 pixels in properties, then select Selection on the Edit tab and perform Strengthener). In the horizontal image, the following measurements are made for one of the convex portions containing an organosilicon polymer. The length of the line along the periphery in the portion where the convex portion and the toner base particle form a continuous interface is taken as the convex width w. The maximum length of the convex portion in the normal direction to the convex width w is taken as the convex diameter D, and the length from the apex of the convex portion to a line along the periphery in the line segment forming the convex diameter D is taken as the convex height H. The measurements are made for 30 arbitrarily selected convex portions, and the arithmetic average of each measurement value is taken as the number-average convex height H.

<Calculation method of H80>
In the STEM image of the cross section of the toner obtained by the above-mentioned scanning transmission electron microscope (STEM), a cumulative distribution of the convex height H is taken for convex portions having a convex height H of 30 nm or more and 300 nm or less. The convex height H that is integrated from the smallest convex height H and accounts for 80% by number is defined as H80 (unit: nm).

<Method of calculating the area ratio of bright areas in a 1.5 μm square reflected electron image of a toner surface>
The bright area ratio is determined by observing the toner surface using a scanning electron microscope. A backscattered electron image of a 1.5 μm square area of the toner surface is obtained. An image is then obtained that is binarized so that the organosilicon polymer portion in the backscattered electron image becomes the bright area, and the ratio of the bright area of the image to the total area of the image is determined. When organic or inorganic fine particles are externally added to the toner, the organic or inorganic fine particles are removed by the following method or the like, and the sample is used.

160 g of sucrose (Kishida Chemical) is added to 100 mL of ion-exchanged water, and dissolved in a hot water bath to prepare a concentrated sucrose solution. 31 g of the concentrated sucrose solution and 6 mL of Contaminon N (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) are placed in a centrifuge tube (50 mL capacity). 1.0 g of toner is added to this, and the toner clumps are loosened with a spatula or the like. The centrifuge tube is shaken at 300 spm (strokes per minute) for 20 minutes in a shaker (AS-1N, sold by AS ONE Corporation). After shaking, the solution is transferred to a glass tube (50 mL) for a swing rotor, and separated in a centrifuge (H-9R, manufactured by Kokusan Co., Ltd.) at 3,500 rpm for 30 minutes. This operation separates the toner particles from the external additives. Visually check that the toner particles and the aqueous solution are sufficiently separated, and collect the toner particles that have separated to the top layer using a spatula or similar tool. After filtering the collected toner particles with a vacuum filter, dry them in a dryer for at least one hour to obtain a sample for measurement. This operation is carried out multiple times to ensure the required amount.

Whether or not the convex portions contain an organosilicon polymer will be confirmed by combining this with elemental analysis using energy dispersive X-ray analysis (EDS), which will be described later.

The SEM equipment and observation conditions are as follows.
Equipment used: ULTRA PLUS manufactured by Carl Zeiss Microscopy Co., Ltd.
Acceleration voltage: 1.0 kV
WD: 2.0 mm
Aperture Size: 30.0 μm
Detection signal: EsB (energy selective backscattered electrons)
EsB Grid: 800V
Observation magnification: 50,000 times Contrast: 63.0±5.0% (reference value)
Brightness: 38.0±5.0% (reference value)
Resolution: 1024 x 768
Pretreatment: Toner particles are scattered on carbon tape (no deposition is performed)

The accelerating voltage and EsB Grid are set to achieve the following: obtaining structural information on the outermost surface of the toner particles, preventing charging up of undeposited samples, and selectively detecting high-energy reflected electrons. The observation field is selected to be near the apex where the curvature of the toner particles is smallest. It was confirmed that the bright areas in the reflected electron image are derived from the organosilicon polymer by overlaying the reflected electron image with an element mapping image obtained by energy dispersive X-ray analysis (EDS) that can be obtained with a scanning electron microscope (SEM).

The SEM/EDS equipment and observation conditions are as follows.
Equipment used (SEM): ULTRA PLUS manufactured by Carl Zeiss Microscopy Co., Ltd.
Equipment used (EDS): NORAN manufactured by Thermo Fisher Scientific Co., Ltd.
System 7, Ultra Dry EDS Detector
Acceleration voltage: 5.0 kV
WD: 7.0 mm
Aperture Size: 30.0 μm
Detection signal: SE2 (secondary electrons)
Observation magnification: 50,000x Mode: Spectral Imaging
Pretreatment: Toner particles are scattered on carbon tape and platinum sputtered.

The mapping image of silicon element obtained by this method is superimposed on the backscattered electron image, and it is confirmed that the silicon atom part of the mapping image matches the bright part of the backscattered electron image.

The ratio of the bright area to the total area of the reflected electron image was calculated by analyzing the reflected electron image of the toner particle surface obtained by the above method using image processing software ImageJ (developed by Wayne Rashand). The procedure is as follows:

First, convert the backscattered electron image to 8-bit from Type in the Image menu. Next, set the Median diameter to 2.0 pixels from Filters in the Process menu to reduce image noise. Estimate the image center after excluding the observation condition display section displayed at the bottom of the backscattered electron image, and select a 1.5 μm square range from the center of the backscattered electron image using the Rectangle Tool on the toolbar. Next, select Threshold from Adjust in the Image menu. Select Default, click Auto, and then click Apply to obtain a binarized image. This operation displays the bright areas of the backscattered electron image in white. Again, estimate the image center after excluding the observation condition display section displayed at the bottom of the backscattered electron image, and select a 1.5 μm square range from the center of the backscattered electron image using the Rectangle Tool on the toolbar. Next, select Histogram from the Analyze menu. Read the Count value from the newly opened Histogram window (corresponding to the total area of the reflected electron image). Also, click List and read the Count value when the brightness is 0 (corresponding to the bright area of the reflected electron image). From this value, calculate the area ratio of the bright area to the total area of the reflected electron image. The above procedure is carried out for 10 fields of view for the toner particles to be evaluated, and the number average value is calculated to obtain the area ratio (%) of the bright area of the image to the total area of the image that has been binarized so that the organosilicon polymer portion in the reflected electron image becomes the bright area.

<Method of Identifying Organosilicon Polymer>
The organosilicon polymer is identified by a combination of observation with a scanning electron microscope (SEM) and elemental analysis by energy dispersive X-ray analysis (EDS).

Using a scanning electron microscope "Hitachi Ultra High Resolution Field Emission Scanning Electron Microscope S-4800" (Hitachi High-Technologies Corporation), the toner is observed in a field of view magnified up to 50,000 times. The surface is observed by focusing on the surface of the toner particle. EDS analysis is performed on the particles present on the surface, and the presence or absence of an Si element peak determines whether the analyzed particles are organosilicon polymers or not. If both organosilicon polymers and silica fine particles are present on the surface of the toner particle, the organosilicon polymer is identified by comparing the ratio of the elemental contents (atomic%) of Si and O (Si/O ratio) with a standard. EDS analysis is performed on the standard specimens of the organosilicon polymer and the silica fine particles under the same conditions to obtain the elemental contents (atomic%) of Si and O. The Si/O ratio of the organosilicon polymer is designated as A, and the Si/O ratio of the silica fine particles is designated as B. Measurement conditions are selected under which A is significantly larger than B. Specifically, 10 measurements are performed on the standard specimen under the same conditions, and the arithmetic mean values of A and B are obtained. Select the measurement conditions that result in an average value of A/B>1.1. If the Si/O ratio of the particle to be identified is on the A side of [(A+B)/2], the particle is determined to be an organosilicon polymer.

Tospearl 120A (Momentive Performance Materials Japan, LLC) is used as a sample of organosilicon polymer particles, and HDK V15 (Asahi Kasei) is used as a sample of silica microparticles.

<Method of measuring number average particle size R of primary particles of external additive>
This is performed in combination with a scanning electron microscope "Hitachi Ultra-High Resolution Field Emission Scanning Electron Microscope S-4800" (Hitachi High-Technologies Corporation) and elemental analysis using energy dispersive X-ray analysis (EDS).

In a field of view magnified up to 50,000 times, the external additive particles are randomly photographed using the EDS elemental analysis method described above. From the photographed image, 100 external additive particles are randomly selected, the major axis of the primary particles of the target external additive particles is measured, and the arithmetic average value is taken as the number-average particle size R. The observation magnification is adjusted appropriately depending on the size of the external additive particles.

<Method for identifying the composition and ratio of constituent compounds of organosilicon polymer>
The composition and ratio of the constituent compounds of the organosilicon polymer contained in the toner are identified using NMR. When the toner contains an external additive such as silica fine particles in addition to the organosilicon polymer, the following procedure is carried out.

1 g of the toner is placed in a vial, dissolved in 31 g of chloroform, and dispersed in the vial by treating with an ultrasonic homogenizer for 30 minutes to prepare a dispersion liquid.
Ultrasonic treatment device: Ultrasonic homogenizer VP-050 (manufactured by Taitec Co., Ltd.)
Microchip: Step type microchip, tip diameter φ2mm
Position of the tip of the microchip: Center of the glass vial, 5 mm above the bottom of the vial Ultrasonic conditions: Intensity 30%, 30 minutes

At this time, ultrasonic waves are applied while cooling the vial with ice water so that the temperature of the dispersion does not rise. The dispersion is transferred to a glass tube for a swing rotor (50 mL) and centrifuged in a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) at 58.33 S-1 for 30 minutes. After centrifugation, the lower layer of the glass tube contains particles with a high specific gravity, such as silica fine particles. The chloroform solution containing the upper layer of the organosilicon polymer is collected and the chloroform is removed by vacuum drying (40°C/24 hours) to prepare a sample. Using the above sample or the organosilicon polymer, the abundance ratio of the constituent compounds of the organosilicon polymer and the proportion of the T3 unit structure represented by R-Si(O1/2)3 in the organosilicon polymer are measured and calculated by solid-state 29Si-NMR.

First, the hydrocarbon group represented by R is confirmed by 13C-NMR.
<13C-NMR (solid) measurement conditions>
Equipment: JEOL RESONANCE JNM-ECX500II
Sample tube: 3.2 mm diameter
Sample: Sample or organosilicon polymer Measurement temperature: Room temperature Pulse mode: CP/MAS
Measurement nuclear frequency: 123.25MHz (13C)
Reference substance: Adamantane (external standard: 29.5 ppm)
Sample rotation speed: 20 kHz
Contact time: 2 ms
Delay time: 2s
Number of times of accumulation: 1024 times

In this method, the presence or absence of signals due to methyl groups (Si-CH3), ethyl groups (Si-C2H5), propyl groups (Si-C3H7), butyl groups (Si-C4H9), pentyl groups (Si-C5H11), hexyl groups (Si-C6H13), or phenyl groups (Si-C6H5-) bonded to silicon atoms is used to confirm the presence of the hydrocarbon group represented by R above. On the other hand, in solid-state 29Si-NMR, peaks are detected in different shift regions depending on the structure of the functional groups bonded to the silicon of the constituent compounds of the organosilicon polymer. The structure bonded to the silicon can be identified by identifying the position of each peak using a standard sample. In addition, the abundance ratio of each constituent compound can be calculated from the obtained peak area. The ratio of the peak area of the T3 unit structure to the total peak area can be calculated.

The specific measurement conditions for solid-state 29Si-NMR are as follows:
Apparatus: JNM-ECX5002 (JEOL RESONANCE)
Temperature: Room temperature Measurement method: DDMAS method 29Si 45°
Sample tube: Zirconia 3.2 mm diameter
Sample: Powdered sample filled in test tube Sample rotation speed: 10 kHz
Relaxation delay: 180s
Scan: 2000

After the measurement, the peaks of the multiple silane components of the sample or organosilicon polymer with different substituents and bonding groups are separated into the following X1, X2, X3, and X4 structures by curve fitting, and the peak areas of each are calculated.

The following X3 structure is a T3 unit structure.
X1 structure: (Ri) (Rj) (Rk) SiO1/2 (A1)
X2 structure: (Rg)(Rh)Si(O1/2)2 (A2)
X3 Structure: RmSi(O1/2)3 (A3)
X4 structure: Si(O1/2)4 (A4)

In the formulae (A1), (A2), and (A3), Ri, Rj, Rk, Rg, Rh, and Rm each represent an organic group such as a hydrocarbon group having 1 to 6 carbon atoms, a halogen atom, a hydroxyl group, an acetoxy group, or an alkoxy group, all of which are bonded to silicon. If it is necessary to confirm the structure in more detail, it may be identified by the results of 1H-NMR measurement in addition to the results of 13C-NMR and 29Si-NMR measurement.

<Method for quantifying organosilicon polymer or silica fine particles contained in toner>
The toner is dispersed in chloroform as described above, and then centrifugal separation is used to separate the external additives such as the organosilicon polymer and silica fine particles based on the difference in specific gravity to obtain samples, and the content of the external additives such as the organosilicon polymer or silica fine particles is determined.

The following is an example of an external additive that is silica microparticles. Other microparticles can also be quantified using the same method.

First, the pressed toner is measured with X-ray fluorescence, and the silicon content in the toner is determined by analytical processing such as the calibration curve method or FP method. Next, the structure of each of the constituent compounds that form the organosilicon polymer and silica microparticles is identified using solid-state 29Si-NMR and pyrolysis GC/MS, and the silicon content in the organosilicon polymer and silica microparticles is determined. The content of the organosilicon polymer and silica microparticles in the toner is calculated from the relationship between the silicon content in the toner determined with X-ray fluorescence and the silicon content in the organosilicon polymer and silica microparticles determined with solid-state 29Si-NMR and pyrolysis GC/MS.

<Method for measuring the adhesion rate of external additives such as organosilicon polymers or silica particles to toner base particles or toner particles using a water washing method>

(Water washing process)
20 g of a 30% by weight aqueous solution of "Contaminon N" (a neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, with a pH of 7) is weighed out and placed in a 50 mL vial, and mixed with 1 g of toner. The vial is then set in a "KM Shaker" (model: V.SX) manufactured by Iwaki Sangyo Co., Ltd., and shaken for 120 seconds at a speed of 50. Depending on the adhesion state of the organosilicon polymer or silica fine particles, the external additives such as the organosilicon polymer or silica fine particles will migrate from the toner base particles or toner particle surfaces to the dispersion liquid. Thereafter, the toner and the external additives such as the organosilicon polymer or silica fine particles that have migrated to the supernatant liquid are separated using a centrifuge (H-9R; manufactured by Kokusan Co., Ltd.) (16.67 S-1 for 5 minutes). The precipitated toner is dried by vacuum drying (40°C/24 hours) and is used as a toner after washing with water.

Next, a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation) was used to photograph the toner that was not subjected to the above-mentioned washing process (toner before washing) and the toner obtained through the above-mentioned washing process (toner after washing).

The measurement target is identified by elemental analysis using energy dispersive X-ray analysis (EDS).

The captured toner surface image is then analyzed using image analysis software Image-Pro Plusver. 5.0 (Nippon Roper Co., Ltd.) to calculate the coverage rate.

The image capturing conditions for the S-4800 are as follows.
(1) Sample preparation: Apply a thin layer of conductive paste to a sample stage (aluminum sample stage 15 mm x 6 mm), then spray toner onto the paste. Then, use air to remove excess toner from the sample stage and allow it to dry thoroughly. Set the sample stage in the sample holder, and adjust the sample stage height to 36 mm using the sample height gauge.

(2) Setting the S-4800 Observation Conditions When measuring the coverage, elemental analysis is performed in advance by the above-mentioned energy dispersive X-ray analysis (EDS) to distinguish between external additives such as organosilicon polymers or silica fine particles on the toner surface, and then measurement is performed. Liquid nitrogen is poured into the anti-contamination trap attached to the S-4800 housing until it overflows, and left for 30 minutes. S-4800 "PC-SEM"
Start the S-4800 and perform flashing (cleaning the FE chip, which is the electron source). Click the accelerating voltage display area on the control panel on the screen and press the [Flushing] button to open the flushing execution dialog. Check that the flushing intensity is 2 and execute. Check that the emission current due to flushing is 20-40 μA. Insert the sample holder into the sample chamber of the S-4800 case. Press [Origin] on the control panel to move the sample holder to the observation position.

Click the acceleration voltage display to open the HV setting dialog, and set the acceleration voltage to [1.1 kV] and the emission current to [20 μA]. In the [Basic] tab of the operation panel, set the signal selection to [SE], select the SE detector to [Upper (U)] and [+BSE], and select [L.A. 100] in the selection box to the right of [+BSE] to set the mode to observation with backscattered electron images. In the same [Basic] tab of the operation panel, set the probe current in the electron optical system condition block to [Normal], the focus mode to [UHR], and the WD to [4.5 mm]. Press the [ON] button on the acceleration voltage display of the control panel to apply the acceleration voltage.

(3) Calculation of toner number average particle diameter (D1) Drag within the magnification display area of the control panel to set the magnification to 5000 (5k). Rotate the focus knob [COARSE] on the operation panel to adjust the aperture alignment when the image is in focus to a certain extent. Click [Align] on the control panel to display the alignment dialog and select [Beam]. Rotate the STIGMA/ALIGNMENT knobs (X, Y) on the operation panel to move the displayed beam to the center of the concentric circle. Next, select [Aperture] and rotate the STIGMA/ALIGNMENT knobs (X, Y) one by one to stop the image movement or adjust it so that the movement is minimized. Close the aperture dialog and adjust the focus with autofocus. Repeat this operation two more times to adjust the focus.

Then, the particle size of 300 toner particles is measured to determine the number average particle size (D1). The particle size of each particle is the maximum diameter observed when the toner particles are observed.

(4) Focus Adjustment For the particles having a number average particle diameter (D1) of ±0.1 μm obtained in (3) above, with the midpoint of the maximum diameter aligned with the center of the measurement screen, drag within the magnification display section of the control panel to set the magnification to 10,000 (10k) times.

Rotate the focus knob [COARSE] on the operation panel, and adjust the aperture alignment when the image is in focus to a certain extent. Click [Align] on the control panel to display the alignment dialog and select [Beam]. Rotate the STIGMA/ALIGNMENT knobs (X, Y) on the operation panel to move the displayed beam to the center of the concentric circles. Next, select [Aperture] and rotate the STIGMA/ALIGNMENT knobs (X, Y) one by one to stop the image movement or to minimize its movement. Close the aperture dialog and use autofocus to adjust the focus. Then, set the magnification to 50,000 (50k) times, adjust the focus using the focus knob and STIGMA/ALIGNMENT knob as above, and use autofocus to adjust the focus again. Repeat this operation to adjust the focus. Here, if the inclination angle of the observation surface is large, the accuracy of the coverage measurement tends to be low, so when adjusting the focus, select an object that simultaneously brings the entire observation surface into focus, and select an object with as little surface inclination as possible for analysis.

(5) Image storage Adjust the brightness in ABC mode, take a photograph with a size of 640 x 480 pixels, and save it. Use this image file to perform the following analysis. Take one photograph for each toner particle to obtain an image of the toner particles.

(6) Image Analysis The image obtained by the above-mentioned method is binarized using the following analysis software to calculate the coverage. At this time, the above screen is divided into 12 squares and each is analyzed. The analysis conditions for the image analysis software Image-Pro Plus ver. 5.0 are as follows. However, if an external additive such as an organosilicon polymer with a particle size of less than 30 nm and more than 300 nm, or silica fine particles with a particle size of less than 30 nm and more than 1200 nm is included in a divided section, the coverage is not calculated for that section.

In the image analysis software Image-Pro Plus 5.0, select "Count/Size" from "Measurement" on the toolbar, then "Options" and set the binarization conditions. In the object extraction options, select 8 connectivity and set smoothing to 0. In addition, do not select pre-selection, fill holes, or inclusion lines, and set "Exclude borders" to "None." Select "Measurement item" from "Measurement" on the toolbar and enter 2 to 107 as the selection range for area.

The coverage rate is calculated by enclosing a square region. At this time, the area (C) of the region should be between 24,000 and 26,000 pixels. "Processing"-Binarization is used to automatically binarize, and the total area (D) of regions free of external additives such as organosilicon polymers or silica fine particles is calculated. The coverage rate can be calculated using the following formula from the area C of the square region and the total area D of regions free of external additives such as organosilicon polymers or silica fine particles.
Coverage rate (%) = 100 - (D / C x 100)

The arithmetic mean of all the data obtained is taken as the coverage rate.

Then, the coverage of the toner before and after washing is calculated,
[Toner coverage after washing]/[Toner coverage before washing]×100 is defined as the “adhesion rate” in the present invention.

(Methods for producing toner particles, additives, and developers)
Next, examples of the production of the toner particles, the external additive A, and the developer of this embodiment will be described.

(Production Example of Toner Particle 2)
<Preparation of aqueous medium 2>
Into a reaction vessel equipped with a stirrer, a thermometer, and a reflux tube, 650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (Rasa Kogyo Co., Ltd., 12-hydrate) were added, and the mixture was kept at 65° C. for 1.0 hour while purging with nitrogen.

A calcium chloride aqueous solution in which 9.2 parts of calcium chloride (dihydrate) was dissolved in 10.0 parts of ion-exchanged water was added all at once while stirring at 15,000 rpm using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare an aqueous medium containing a dispersion stabilizer. Furthermore, 10% by mass of hydrochloric acid was added to the aqueous medium to adjust the pH to 5.0, and aqueous medium 2 was obtained.

<Preparation of polymerizable monomer composition>
Styrene: 60.0 parts C.I. Pigment Blue 15:3: 6.5 parts by mass

The above material was placed in an attritor (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) and further dispersed using zirconia particles having a diameter of 1.7 mm at 220 rpm for 5.0 hours, after which the zirconia particles were removed to prepare a colorant dispersion.

on the other hand,
Styrene: 20.0 parts by mass; n-Butyl acrylate: 20.0 parts by mass; Crosslinking agent (divinylbenzene): 0.3 parts by mass; Saturated polyester resin: 5.0 parts by mass (polycondensate of propylene oxide modified bisphenol A (2 mole adduct) and terephthalic acid (molar ratio 10:12), glass transition temperature (Tg) 68°C, weight average molecular weight (Mw) 10,000, molecular weight distribution (Mw/Mn) 5.12)
Fischer-Tropsch wax (melting point 78°C): 7.0 parts by mass

The material was added to the colorant dispersion and heated to 65°C, after which it was uniformly dissolved and dispersed at 500 rpm using a T.K. homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a polymerizable monomer composition.

<Granulation process>
The temperature of the aqueous medium 2 was adjusted to 70° C., and the rotation speed of the T.K. homomixer was kept at 15,000 rpm, while the polymerizable monomer composition was charged into the aqueous medium 1, and 10.0 parts by mass of t-butyl peroxypivalate, a polymerization initiator, was added. Granulation was continued for 10 minutes while maintaining the stirring speed at 15,000 rpm.

<Polymerization process and distillation process>
After the granulation step, the agitator was replaced with a propeller agitator blade, and polymerization was carried out for 5.0 hours while stirring at 150 rpm and maintaining the temperature at 70° C., and then the temperature was raised to 85° C. and maintained at that temperature for 2.0 hours. Thereafter, the reflux tube of the reaction vessel was replaced with a cooling tube, and the obtained slurry was heated to 100° C. to carry out distillation for 6 hours, thereby distilling off the unreacted polymerizable monomer, and a resin particle dispersion was obtained.

<Organosilicon Polymer Formation Process>
In a reaction vessel equipped with a stirrer and a thermometer, 60.0 parts of ion-exchanged water was weighed, and the pH was adjusted to 4.0 using 10% by mass hydrochloric acid. This was heated while stirring, and the temperature was set to 40°C. Then, 40.0 parts of methyltriethoxysilane, an organosilicon compound, was added, and the mixture was stirred for 2 hours or more to carry out hydrolysis. The end point of hydrolysis was confirmed by visual observation that the oil and water were not separated and became one layer, and the mixture was cooled to obtain a hydrolyzed liquid of an organosilicon compound.

After adjusting the temperature of the resin particle dispersion obtained above to 55°C, 25.0 parts of the hydrolyzed liquid of the organosilicon compound (addition amount of organosilicon compound was 10.0 parts) was added to initiate polymerization of the organosilicon compound. After holding for 0.25 hours, the pH was adjusted to 5.5 with a 3.0% aqueous sodium bicarbonate solution. With continued stirring at 55°C, the mixture was held for 1.0 hour (condensation reaction 1), after which the pH was adjusted to 9.5 with a 3.0% aqueous sodium bicarbonate solution and held for a further 4.0 hours (condensation reaction 2) to obtain a toner particle dispersion.

(Washing process and drying process)
The resin particle dispersion was cooled, and hydrochloric acid was added to the resin particle dispersion to adjust the pH to 1.5 or less, and the mixture was left for 1.0 hour while stirring. Thereafter, the mixture was subjected to solid-liquid separation using a pressure filter to obtain a toner cake. The obtained toner cake was reslurried with ion-exchanged water to prepare a dispersion again, and then subjected to solid-liquid separation using the aforementioned filter to obtain a toner cake. The obtained toner cake was transferred to a thermostatic chamber at 40° C., and dried and classified for 72 hours to obtain toner particles 2.

(Production Example of External Additive A)
The external additive A was prepared as follows. 150 parts of 5% aqueous ammonia was added to a 1.5 L glass reaction vessel equipped with a stirrer, a dropping nozzle, and a thermometer to prepare an alkaline catalyst solution. After adjusting the alkaline catalyst solution to 50° C., 100 parts of tetraethoxysilane and 50 parts of 5% aqueous ammonia were dropped simultaneously while stirring, and the mixture was reacted for 8 hours to obtain a silica microparticle dispersion.

The resulting silica microparticle dispersion was then dried by spray drying and crushed in a pin mill to obtain silica microparticles with a number-average primary particle size of 100 nm as external additive A.

(Production Example of Developer 3)
100.00 parts of toner particles 2 and 0.50 parts of external additive A were charged into a Henschel mixer (FM10C type manufactured by Nippon Coke & Engineering Co., Ltd.) with water at 7°C passing through the jacket. Next, after the water temperature in the jacket stabilized at 7°C ± 1°C, the mixture was mixed for 10 minutes with the peripheral speed of the rotating blade set to 38 m/sec. During the mixing, the amount of water passing through the jacket was appropriately adjusted so that the temperature inside the tank of the Henschel mixer did not exceed 25°C. The obtained mixture was sieved through a mesh with an opening of 75 μm to obtain developer 3.

From the viewpoint of reducing adhesion, it is preferable to have a large number of transfer-promoting particles covering the toner. However, adding too many transfer-promoting particles increases the risk of contaminating components inside the image forming device 100, so it is preferable to adjust the amount according to the configuration. In this Example 2, the amount of external additive A relative to the toner particles was half that of Example 1.

In addition, in the developer 3 used in Example 2, the organosilicon polymer forms convex portions on the surface of the toner base particles, improving the fluidity of the developer, so external additive B (R = 10 nm) is not added.

The physical properties of Developer 3 are shown in Table 6.

In the table, "X" represents the ratio of the number-average particle size R of the primary particles of external additive A to the number-average height H of the protrusions. When the manufactured developer was observed using an SEM, it was confirmed that external additive A was arranged as transfer-promoting particles on the protrusions of the organosilicon polymer of the toner particles, and the average number of external additive A particles coated per toner particle was about 250.

(Verification experiment)
The effect of Example 2 was verified using the same procedure as in Example 1. The amount of developer adhering to the charging roller and its effect on an image were confirmed, and the results will be described.

The verified configuration is shown in Table 7.

The difference between Example 1 and Example 2 is the toner particles. In Example 2, the toner particles 2 have protrusions formed on the surface of the toner base particles by the organosilicon polymer, and the adhesion to the external additive A is small, so the external additive A is easily detached and easily adheres to the photosensitive drum 1 and the charging roller 2.

As in Example 1, 50 sheets of A4 paper (GF-C081, Canon) were printed with image B in succession, and the change in density difference was confirmed. After printing, the vertical solid band forming portion of charging roller 2 and the other portions were photographed to confirm the adhesion of developer and additive A.

Figure 17 shows the results of measuring the density difference between the vertical solid band and the other areas when 50 sheets were passed continuously. As with Example 1, it can be seen that in Example 2, the density difference is slightly positive.

Figure 18 shows a schematic diagram of the result of taking a photograph of the vertical solid band area of the charging roller 2 after 50 sheets of paper were passed continuously. It can be seen that almost no residual developer remains after transfer.

Furthermore, the surface of the charging roller 2 was observed under a microscope, and the coverage rate of the transfer-promoting particles on the surface of the charging roller 2 is shown in Table 8. Specifically, the coverage rate was calculated using the following procedure for an image of the surface of the charging roller 2 observed at a magnification of 3000 times using a laser microscope (VK-X200, Keyence). A binarization process was performed on the area containing the transfer-promoting particles and other areas, and the total area rate of the transfer-promoting particles on the surface of the charging roller 2 was calculated as the coverage rate of the transfer-promoting particles on the surface of the charging roller 2. For comparison, the coverage rate of Example 1 is also shown.

From Table 8, it can be seen that in Example 2, even though the amount of external additive A relative to the toner particles is half that of Example 1, the charging roller 2 is covered with transfer-promoting particles to the same extent as in Example 1. The reason for the above results is presumed to be as follows.

In this embodiment, since the external additive A is easily detached from the toner particles 2, when the developer 3 is nipped between the developing roller 41 and the photosensitive drum 1 in the developing section, the external additive A adheres to the photosensitive drum 1.
Even if a toner image is not being formed, as long as the developer 3 is in contact with the photosensitive drum 1, the external additive A is transferred from the toner particles 2 to the photosensitive drum 1. The external additive A that has adhered to the photosensitive drum 1 also adheres to the charging roller 2 that is in contact with the photosensitive drum 1, and the surface layer of the charging roller 2 is covered with the external additive A.

By covering the surface of the charging roller 2 with external additive A, not only the adhesive force between the photosensitive drum 1 and developer 3 but also the adhesive force between the charging roller 2 and developer 3 is reduced. Because external additive A is present between the developer 3 and the charging roller 2, adhesion of the developer 3 to the charging roller 2 is suppressed. On the other hand, the transfer residue that could not be collected by the developing roller 41 is transferred to the horizontal band halftone, so the density difference is slightly positive. The effect of external additive A adhering to the photosensitive drum 1 improves transferability, and the density difference is slightly smaller than in Example 1.

As in Example 1, the calculation results of the adhesion force that were used as a reference when arriving at the above speculation are shown below. The calculations are performed assuming a model in which the residual developer after transfer is nipped between the photosensitive drum 1 and the charging roller 2. The calculation results are shown in Figure 19. The details of the calculations are explained below.

The formula used for the calculation is the same as in Example 1. In this example, many transfer-promoting particles adhere not only to the surface of the toner particles, but also to the drum surface particles of the photosensitive drum 1. In addition, many transfer-promoting particles adhere to the surface layer of the charging roller 2. This increases the chance of the transfer-promoting particles coming into contact with each other. Figure 19 calculates the intermolecular force when the transfer-promoting particles come into contact with each other. If the particle size of the transfer-promoting particles on the surface of the developer is 100 [nm], the van der Waals (intermolecular) force Fv generated between the transfer-promoting particles is 2.6 [nN]. Since this is smaller than the Coulomb force Fe (170 [nN]), it is possible to suppress adhesion of the developer to the charging roller 2.

As described above, when the charging roller 2 is covered to a certain extent with the transfer-promoting particles, newly supplied transfer-promoting particles come into contact with the transfer-promoting particles on the surface of the charging roller 2, rather than with the surface of the charging roller 2 itself. Because the intermolecular forces between the transfer-promoting particles are small, the transfer-promoting particles are less likely to adhere to the charging roller 2, and are transported by the photosensitive drum 1 as is, and are consumed by being transferred onto the intermediate transfer belt 10, etc. If the transfer-promoting particles on the surface of the charging roller 2 are detached, newly supplied transfer-promoting particles come into contact with the surface of the charging roller 2 and adhere to the charging roller 2 again. Thus, the amount of transfer-promoting particles on the surface of the charging roller 2 is balanced to a certain extent.

In the configuration described in Example 1, in which external additive A is present on the toner surface to suppress toner adhesion to other components, if the developer deteriorates due to use of the image forming apparatus and external additive A becomes embedded in the toner particles, the expected adhesion suppression effect may not be achieved. In the configuration described in Example 2, in which external additive A is disposed on the protrusions on the toner surface, the protrusions suppress the embedding of external additive A in the toner particles, so external additive A can be supplied to the charging roller 2 stably for a long period of time. In addition, even if external additive A is detached from the protrusions on the toner surface, the adhesion force of the protrusions is smaller than the adhesion force of the toner surface, so the toner is less likely to adhere to the charging roller 2, and it is expected that the adhesion suppression effect will be achieved stably for a long period of time.

In the first and second embodiments, the operation using a color image forming device is described, but this is not particularly limited, and a monochrome image forming device may also be used.

[Configuration 1]
An image carrier;
a charging member that contacts the image carrier and charges the image carrier to a predetermined potential;
An image forming apparatus having a developer storage device,
the developer is composed of toner particles and transfer-promoting particles adhering to surfaces of the toner particles, the transfer-promoting particles having an average particle size of 30 nm or more and 1000 nm or less;
the image bearing member has a surface layer containing particles and a binder resin,
the particles contained in the surface layer have a plurality of peaks in a particle size distribution based on number,
Among the plurality of peaks, a peak having a peak top frequency of 20 nm or more in the particle size distribution is designated as a first peak, and a peak having a peak top frequency second highest after the first peak is designated as a second peak,
The particle size DA of the peak top of the first peak or the second peak, whichever has a larger particle size value at the peak top, is 80 nm or more and 300 nm or less;
Among the particles contained in the surface layer, particles having a particle size in the range of DA±20 nm are referred to as particles PAA, and convex portions derived from the particles PAA and having a height of 10 nm or more and 300 nm or less are referred to as convex portions CA. The convex portions CA are disposed on the surface of the surface layer,
When the surface layer is viewed from above, an average value of the distance between the centers of gravity of the convex portions CA is 150 nm or more and 500 nm or less, and a standard deviation of the distance between the centers of gravity of the convex portions CA is 250 nm or less.
1. An image forming apparatus comprising:
[Configuration 2]
The image forming apparatus according to configuration 1, characterized in that, when the area occupied by the particles on the surface of the surface layer of the image carrier is S1 and the area occupied by the parts other than the particles is S2, S1/(S1+S2) is 0.70 or more and 1.00 or less.
[Configuration 3]
When the average film thickness of the surface layer at a portion of the cross section of the surface layer that does not contain particles having a particle diameter DA in the range of DA ± 20 nm is T,
D A > T
3. The image forming apparatus according to claim 1, wherein
[Configuration 4]
The particle diameter DB of the peak top of the first peak and the second peak, which has a smaller particle diameter value at the peak top, is
D B < T
4. The image forming apparatus according to claim 3,
[Configuration 5]
In the surface layer,
DB/DA > 1/10
5. The image forming apparatus according to claim 4,
[Configuration 6]
The image forming apparatus according to any one of configurations 1 to 5, characterized in that the ratio of the number of protrusions originating from particles having a particle diameter DA in the range of DA ±20 nm to the number of protrusions present on the surface of the surface layer is 90 number % or more.
[Configuration 7]
The image forming apparatus according to any one of configurations 1 to 6, characterized in that, when the first peak and the second peak are compared, the half-value width of the peak having a larger particle diameter at the peak top is 20 nm or more and 50 nm or less.
[Configuration 8]
8. The image forming apparatus according to any one of claims 1 to 7, wherein the maximum height difference Rz of the surface of the surface layer of the image carrier is 100 nm or more and 400 nm or less.
[Configuration 9]
9. The image forming apparatus according to any one of configurations 1 to 8, wherein the circularity of the particles having a particle diameter DA in the range of DA±20 nm is 0.950 or more.
[Configuration 10]
The developer has convex portions formed of fine particles containing an organosilicon polymer having a structure represented by the following formula (1) present on the surface of the toner particles, and the transfer-promoting particles are disposed on the convex portions: R-Si(O1/2)3 (1)
(The above R represents a hydrocarbon group having 1 to 6 carbon atoms.)
10. The image forming apparatus according to any one of configurations 1 to 9.
[Configuration 11]
the average particle size of the transfer-promoting particles is smaller than the average value of the distance between the centers of gravity of the convex portions derived from particles having a particle size DA in the range of DA ± 20 nm;
11. The image forming apparatus according to any one of configurations 1 to 10.
[Configuration 12]
An image carrier;
a charging member that contacts the image carrier and charges the image carrier to a predetermined potential;
A process cartridge capable of accommodating a developer,
the developer is composed of toner particles and transfer-promoting particles adhering to surfaces of the toner particles, the transfer-promoting particles having an average particle size of 30 nm or more and 1000 nm or less;
A process cartridge having
the image bearing member has a surface layer containing particles and a binder resin,
the particles contained in the surface layer have a plurality of peaks in a particle size distribution based on number,
Among the plurality of peaks, a peak having a peak top frequency of 20 nm or more in the particle size distribution is designated as a first peak, and a peak having a peak top frequency second highest after the first peak is designated as a second peak,
The particle size DA of the peak top of the first peak or the second peak, whichever has a larger particle size value at the peak top, is 80 nm or more and 300 nm or less;
Among the particles contained in the surface layer, particles having a particle size in the range of DA±20 nm are referred to as particles PAA, and convex portions derived from the particles PAA and having a height of 10 nm or more and 300 nm or less are referred to as convex portions CA. The convex portions CA are disposed on the surface of the surface layer,
When the surface layer is viewed from above, the average value of the distance between the centers of gravity of the convex portions CA is 150 nm or more and 500 nm or less, and the standard deviation of the distance between the centers of gravity of the convex portions is 250 nm or less.
A process cartridge comprising:
[Configuration 13]
The process cartridge described in Configuration 12, characterized in that, when the area occupied by the particles on the surface of the surface layer of the image carrier is S1 and the area occupied by anything other than the particles is S2, S1/(S1+S2) is 0.70 or more and 1.00 or less.
[Configuration 14]
When the average film thickness of the surface layer at a portion of the cross section of the surface layer that does not contain particles having a particle diameter DA in the range of DA ± 20 nm is T,
D A > T
14. The process cartridge according to claim 12 or 13,
[Configuration 15]
The particle size DB of the peak top having a smaller particle size value at the peak top in comparing the first peak and the second peak is
D B < T
15. The process cartridge according to claim 14,
[Configuration 16]
In the surface layer,
DB/DA > 1/10
16. The process cartridge according to claim 15,
[Configuration 17]
The process cartridge described in any one of Configurations 12 to 16, characterized in that the ratio of the number of protrusions originating from particles having a particle diameter DA in the range of DA ±20 nm to the number of protrusions present on the surface of the surface layer is 90 number % or more.
[Configuration 18]
The process cartridge described in any one of Configurations 12 to 17, characterized in that, when the first peak and the second peak are compared, the half-value width of the peak with a larger particle diameter at the peak top is 20 nm or more and 50 nm or less.
[Configuration 19]
19. The process cartridge according to any one of Configurations 12 to 18, wherein the maximum height difference Rz of the surface of the surface layer of the image carrier is 100 nm or more and 400 nm or less.
[Configuration 20]
20. The process cartridge according to any one of Configurations 12 to 19, wherein the circularity of the particles having a particle diameter DA in the range of DA±20 nm is 0.950 or more.
[Configuration 21]
The developer has convex portions formed of fine particles containing an organosilicon polymer having a structure represented by the following formula (1) present on the surface of the toner particles, and the transfer-promoting particles are disposed on the convex portions: R-Si(O1/2)3 (1)
(The above R represents a hydrocarbon group having 1 to 6 carbon atoms.)
21. The process cartridge according to any one of configurations 12 to 20.
[Configuration 22]
the average particle size of the transfer-promoting particles is smaller than the average value of the distance between the centers of gravity of the convex portions derived from particles having a particle size DA in the range of DA ± 20 nm;
22. The process cartridge according to any one of items 12 to 21,

1: Photosensitive drum, 2: Charging roller, 100: Image forming device

Claims (22)

An image carrier;
a charging member that contacts the image carrier and charges the image carrier to a predetermined potential;
An image forming apparatus having a developer storage device,
the developer is composed of toner particles and transfer-promoting particles adhering to surfaces of the toner particles, the transfer-promoting particles having an average particle size of 30 nm or more and 1000 nm or less;
the image bearing member has a surface layer containing particles and a binder resin,
the particles contained in the surface layer have a plurality of peaks in a particle size distribution based on number,
Among the plurality of peaks, a peak having a peak top frequency of 20 nm or more in the particle size distribution is designated as a first peak, and a peak having a peak top frequency second highest after the first peak is designated as a second peak,
The particle size DA of the peak top of the first peak or the second peak, whichever has a larger particle size value at the peak top, is 80 nm or more and 300 nm or less;
Among the particles contained in the surface layer, particles having a particle size in the range of DA±20 nm are referred to as particles PAA, and convex portions derived from the particles PAA and having a height of 10 nm or more and 300 nm or less are referred to as convex portions CA. The convex portions CA are disposed on the surface of the surface layer,
When the surface layer is viewed from above, an average value of the distance between the centers of gravity of the convex portions CA is 150 nm or more and 500 nm or less, and a standard deviation of the distance between the centers of gravity of the convex portions CA is 250 nm or less.
1. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein, on the surface of the surface layer of the image carrier, an area occupied by the particles is S1 and an area occupied by anything other than the particles is S2, and S1/(S1+S2) is 0.70 or more and 1.00 or less. When the average film thickness of the surface layer at a portion of the cross section of the surface layer that does not contain particles having a particle diameter DA in the range of DA ± 20 nm is T,
D A > T
2. The image forming apparatus according to claim 1, The particle size DB of the peak top of the first peak and the second peak, which has a smaller particle size value at the peak top, is
D B < T
4. The image forming apparatus according to claim 3, In the surface layer,
DB/DA > 1/10
5. The image forming apparatus according to claim 4, The image forming apparatus according to any one of claims 1 to 5, characterized in that, among the number of protrusions present on the surface of the surface layer, the proportion of the number of protrusions originating from particles having a particle diameter DA in the range of DA ± 20 nm is 90 number % or more. 6. The image forming apparatus according to claim 1, wherein the half-value width of the peak having a larger particle diameter at its peak top is 20 nm or more and 50 nm or less, when the first peak and the second peak are compared. 6. The image forming apparatus according to claim 1, wherein a maximum height difference Rz on the surface of the surface layer of the image carrier is 100 nm or more and 400 nm or less. 6. The image forming apparatus according to claim 1, wherein the circularity of the particles having a particle diameter DA in the range of DA±20 nm is 0.950 or more. The developer has convex portions formed of fine particles containing an organosilicon polymer having a structure represented by the following formula (1) present on the surface of the toner particles, and the transfer-promoting particles are disposed on the convex portions: R-Si(O1/2)3 (1)
(The above R represents a hydrocarbon group having 1 to 6 carbon atoms.)
6. The image forming apparatus according to claim 1, wherein the image forming apparatus is a liquid crystal display. the average particle size of the transfer-promoting particles is smaller than the average value of the distance between the centers of gravity of the convex portions derived from particles having a particle size DA in the range of DA ± 20 nm;
6. The image forming apparatus according to claim 1, wherein the image forming apparatus is a liquid crystal display. An image carrier;
a charging member that contacts the image carrier and charges the image carrier to a predetermined potential;
A process cartridge capable of accommodating a developer,
the developer is composed of toner particles and transfer-promoting particles adhering to surfaces of the toner particles, the transfer-promoting particles having an average particle size of 30 nm or more and 1000 nm or less;
A process cartridge having
the image bearing member has a surface layer containing particles and a binder resin,
the particles contained in the surface layer have a plurality of peaks in a particle size distribution based on number,
Among the plurality of peaks, a peak having a peak top frequency of 20 nm or more in the particle size distribution is designated as a first peak, and a peak having a peak top frequency second highest after the first peak is designated as a second peak,
The particle size DA of the peak top of the first peak or the second peak, whichever has a larger particle size value at the peak top, is 80 nm or more and 300 nm or less;
Among the particles contained in the surface layer, particles having a particle size in the range of DA±20 nm are referred to as particles PAA, and convex portions derived from the particles PAA and having a height of 10 nm or more and 300 nm or less are referred to as convex portions CA. The convex portions CA are disposed on the surface of the surface layer,
When the surface layer is viewed from above, the average value of the distance between the centers of gravity of the convex portions CA is 150 nm or more and 500 nm or less, and the standard deviation of the distance between the centers of gravity of the convex portions is 250 nm or less.
A process cartridge comprising: 13. The process cartridge according to claim 12, wherein, when an area of the surface of the surface layer of the image carrier occupied by the particles is S1 and an area occupied by the particles other than the particles is S2, S1/(S1+S2) is 0.70 or more and 1.00 or less. When the average film thickness of the surface layer at a portion of the cross section of the surface layer that does not contain particles having a particle diameter DA in the range of DA ± 20 nm is T,
D A > T
13. The process cartridge according to claim 12, The particle size DB of the peak top having a smaller particle size value at the peak top in comparing the first peak and the second peak is
D B < T
15. The process cartridge according to claim 14, In the surface layer,
DB/DA > 1/10
16. The process cartridge according to claim 15, The process cartridge according to any one of claims 12 to 16, characterized in that the proportion of the number of convex portions originating from particles having a particle diameter DA in the range of DA ± 20 nm among the number of convex portions present on the surface of the surface layer is 90 number % or more. 17. The process cartridge according to claim 12, wherein a half width of the peak having a larger particle diameter at its top, when the first peak and the second peak are compared, is 20 nm or more and 50 nm or less. 17. The process cartridge according to claim 12, wherein a maximum height difference Rz of the surface of the surface layer of the image bearing member is 100 nm or more and 400 nm or less. 17. The process cartridge according to claim 12, wherein the circularity of the particles having a particle diameter DA in the range of DA±20 nm is 0.950 or more. The developer has convex portions formed of fine particles containing an organosilicon polymer having a structure represented by the following formula (1) present on the surface of the toner particles, and the transfer-promoting particles are disposed on the convex portions: R-Si(O1/2)3 (1)
(The above R represents a hydrocarbon group having 1 to 6 carbon atoms.)
17. The process cartridge according to claim 12, wherein the first and second electrodes are arranged in a first direction. the average particle size of the transfer-promoting particles is smaller than the average value of the distance between the centers of gravity of the convex portions derived from particles having a particle size DA in the range of DA ± 20 nm;
17. The process cartridge according to claim 12, wherein the first and second electrodes are arranged in a first direction.

Images