JP2001324857A - Electrophotographic image forming method, electrophotographic image forming device and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic image forming method, an electrophotographic image forming device and a process cartridge capable of maintaining high image quality over a long term by preventing the damage of a photoreceptor due to the attachment/detachment of a transfer means. SOLUTION: In an electrophotographic image forming system having a stage to electrify the electrophotographic photoreceptor by bringing an electrifying member consisting of magnetic particles into contact with the photoreceptor and applying voltage, a stage to form the latent image by exposing the photoreceptor, a developing stage to make the latent image visualizable with toner, a stage to transfer a toner image to a transfer member, and a mechanism for attaching/detaching the transfer member to/from the photoreceptor, universal hardness HU in the surface coating film material test of the photoreceptor is >=200 N/mm2 (provided that a curve showing relation between hardness H and the indentation depth (h) of an indenter does not have an inflection point), the volume average particle size of the magnetic particle is >=10 μm and <=40 μm, and the volume ratio of the magnetic particle whose particle size is >50 μm is <=2%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming method comprising an electrophotographic photosensitive member and a member for charging the photosensitive member in contact, and charging the photosensitive member by applying a voltage from the contact charging member. The present invention relates to an electrophotographic image forming apparatus and a process cartridge used in the apparatus.

[0002]

2. Description of the Related Art Conventionally, as a charging means of an electrophotographic apparatus,
Corona chargers have been widely used. The corona charger is a non-contact type charging device, and includes, for example, a discharge electrode such as a wire electrode, a shield electrode surrounding the discharge electrode, and an electrophotographic photosensitive member (hereinafter, referred to as a “photosensitive member”) having a discharge opening as a member to be charged. body"
(Which may be referred to as "contact") in a non-contact manner, and by applying a high voltage to the discharge electrode and the shield electrode, the photosensitive member surface is charged to a predetermined potential by exposing the photosensitive member to a generated discharge current. It is.

On the other hand, in recent years, there are advantages such as low ozone and low power as compared with a corona charger, and therefore, a contact type charging method in which a charging member to which a voltage is applied is brought into contact with a photoconductor to charge the photoconductor is used. Devices (contact charging devices) have been put to practical use.

In a contact charging device, a conductive charging member such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type is brought into contact with a photosensitive member, and a predetermined charging bias is applied to the charging member. Then, the surface of the photoconductor is charged to a predetermined potential.

[0005] In addition, two types of charging mechanisms, (1) discharge charging mechanism and (2) direct injection charging mechanism, are mixed in the charging mechanism of contact charging.

For example, a roller charging method using a conductive roller (charging roller) as a contact charging member is preferable in terms of charging stability, and is widely used. In this roller charging, a charging mechanism is a discharge charging mechanism. Dominant.

Since the discharge charging system has a fixed discharge threshold value for the contact charging member and the photosensitive member, it is necessary to apply a voltage higher than the charging potential to the contact charging member. In addition, although the amount of generation is much smaller than that of the corona charger, the generation of discharge products is inevitable, so that the harmful effects of active ions such as ozone are inevitable.

Therefore, a direct injection charging system for charging the surface of a photoreceptor by directly injecting charge from a contact charging member to a photoreceptor is disclosed in Japanese Patent Application No. 04-158128 and Japanese Patent Application Laid-Open No. 06-003921.
It is proposed in Japanese Patent Publication No.

According to this, a medium-resistance contact charging member comes into contact with the surface of the photoreceptor, and charges are directly injected into the surface of the photoreceptor without a discharge phenomenon, that is, basically without using a discharge mechanism. Therefore, even if the voltage applied to the contact charging member is equal to or lower than the discharge threshold, the photosensitive member can be charged to a potential corresponding to the applied voltage. Since this direct injection charging mechanism does not involve the generation of ions, there is no adverse effect due to discharge generation.

Specifically, a magnetic brush system in which magnetic particles are brought into contact with a photosensitive member as a contact member is known. The magnetic brush method includes, for example, a magnet roll as a magnetic force generating member, a non-magnetic electrode sleeve (aluminum, SUS, conductive resin, etc.) rotatably provided over the outer circumference of the magnet roll, and a magnet on the surface of the electrode sleeve. It has a layer of magnetic particles (magnetic brush) that is attracted and held by the magnetic force of the roll. The magnetic brush is provided so as to be in contact with the photoconductor, and the surface of the photoconductor can be charged to a desired potential by applying a voltage to the electrode sleeve. For example, JP-A-59-133569 discloses a method in which particles coated with iron powder are held on a magnet roll and a voltage is applied to charge the particles.

Other magnetic particles used for the magnetic brush include, for example, metals such as copper, nickel, aluminum, gold, and silver, iron oxide, and the like in JP-A-61-57958.
Conductive fine particles containing metal oxides such as ferrite, zinc oxide, tin oxide, antimony oxide, and titanium oxide;
No. 21873, iron powder, iron powder with oxidized surface, various ferrite powders, JP-A-4-116674, iron, chromium, nickel, metals such as cobalt, or compounds or alloys thereof, for example, Iron trioxide, γ-ferric oxide, chromium dioxide, manganese oxide, ferrite, and manganese-copper alloys are disclosed. Further, Japanese Patent Application Laid-Open No. 07-72667 discloses that magnetic particles coated with a styrene acrylic resin or the like are used to improve environmental dependency.

In Japanese Patent Application Laid-Open No. 11-212332, the volume average particle diameter of the magnetic particles is set to 10 μm or more from the viewpoint of leakage of the magnetic particles from the magnetic brush and transportability of the magnetic particles in the magnetic brush. It is disclosed that the thickness is preferably set to 40 μm or less.

Further, in the same publication, the ratio of the minor axis length to the major axis length (minor axis length / major axis length) of the 5 μm to 20 μm portion of the magnetic particles is considered from the viewpoint of the durability of the magnetic particles. ) Is preferably 0.85 or less. On the other hand, as a transfer unit of an electrophotographic apparatus, a corona discharge transfer or a contact type transfer body is known.

Since the latter can set the applied bias lower than the former, there is an advantage that scattering of toner and generation of ozone caused by excessive supply of electric charge to the back surface of the transfer material can be suppressed, and also from the viewpoint of ecology. Contact-type transfer members have been widely used.

As the contact-type charging member, a roller shape composed of a core metal and a columnar elastic body, a drum shape having an elastic layer formed on the surface of a drum-type base, and an endless elastic body on a plurality of supports are used. A suspended belt shape has been put to practical use.

These contact-type transfer members are generally detached from the photoconductor when the paper is clogged near the photoconductor. Further, in order to avoid abrasion and contamination of the photosensitive member due to unnecessary contact between the photosensitive member and the transfer member, a mechanism for separating the transfer member from the photosensitive member except during image formation may be provided.

[0017]

By the way, in the magnetic brush charging as described above, the magnetic particles constituting the magnetic brush are detached from the magnetic brush to a considerable extent and adhere to the photoreceptor. As described above, the base material of the magnetic particles is made of an inorganic material, and when the transfer member is brought into contact with the photosensitive member in a state where the magnetic particles are attached to the photosensitive member, the magnetic particles are embedded in the photosensitive member, Causes scratches.

This phenomenon has been remarkably caused in a so-called cleanerless image forming apparatus having a simultaneous developing and cleaning means without having an independent cleaning means.

Further, from the viewpoint of durability of the magnetic particles,
The minor axis length / major axis length of the particles in the range of μm to 20 μm is equal to 0.
When magnetic particles having a particle size of 85 or less were used, the occurrence was particularly remarkable.

The present invention has been made in view of the above-mentioned point of view, and an electrophotographic image forming method and an electrophotographic image forming method capable of preventing damage to a photoconductor caused by detachment of a transfer means and maintaining high image quality for a long period of time. An object of the present invention is to provide a forming apparatus and a process cartridge used in the forming apparatus.

[0021]

That is, the present invention provides an electrophotographic photosensitive member having a photosensitive layer on a conductive support and a charging member made of magnetic particles, and applies a voltage to apply a voltage to the photosensitive member. A charging step, a step of exposing the photoconductor to form a latent image, a developing step of visualizing the latent image with toner, a step of transferring the toner image to a transfer material, and a transfer member used in the transfer step. In an electrophotographic image forming method having a mechanism for attaching and detaching to and from the photoreceptor, under the condition that a curve indicating the relationship between the hardness H of the photoreceptor and the indentation depth h has no inflection point. The universal hardness HU in the surface film physical property test of the photoreceptor is 200 N / mm ² or more, and the volume average particle diameter of the magnetic particles is 10 μm or more,
40 μm or less, and the volume ratio of the magnetic particles having a particle size of more than 50 μm is 2% or less.

The present invention solves a particularly prominent technical problem in the above-described specific process, that is, a technical problem peculiar to a system having a contact charging made of magnetic particles and a mechanism capable of attaching and detaching a transfer member to and from a photosensitive member. The problem has been solved by using an electrophotographic photosensitive member having specific surface characteristics and magnetic particles having a specific particle size.

The universal hardness in the present invention can be obtained by the following surface film physical property test.
The surface film physical property test is a test for analyzing the hardness of a thin film, a cured film, an organic film, and the like. In the measurement, a tester shown in FIG. 5 (a hardness tester manufactured by Fischer Instruments, Germany) is used. Fisher scope H100V), square pyramid, facing angle 136 °
Using a diamond indenter 33 stipulated in (1), when the measured load is applied stepwise to the sample film on the sample 31, the indentation depth h under the applied load is electrically detected. And read it. In FIG. 5, reference numeral 34 denotes a movable table, and 32 denotes a sample table.

The hardness H is represented by a value obtained by dividing a test load by a surface area of an indentation generated by the test load. The universal hardness HU is represented by a hardness at a set maximum indentation depth hx (hx = 1 μm in the present invention). With respect to the hardness H and the universal hardness HU, the higher the numerical value, the higher the film hardness (see FIG. 6). However, as shown in FIG. 7, the curve indicating the relationship between the hardness H and the indentation depth h of the indenter in the surface film property test has an inflection point indicating a sharp change in the hardness H at the indentation depth h '. There are cases. This means that the film was broken and cracked at the indentation depth h '. Such a film whose surface is cracked is easily damaged by a deep wound, and is outside the scope of the present invention.

The measurement conditions of the surface film physical property test were as follows.
It shall be performed at 23 ° C. and 50%.

On the other hand, the particle size and distribution of the magnetic particles in the present invention can be obtained by the following particle size distribution measurement. That is, with a laser diffraction type particle size distribution analyzer HEROS (manufactured by JEOL Ltd.)
The range of 350 μm was measured by dividing 32 logarithms, and the volume was 50
The% median diameter was defined as the volume average particle diameter.

Further, in the present invention, the volume ratio occupied by the particle diameter of more than 50 μm is determined by dividing the channel divided as shown in Table 1 obtained by the above-mentioned laser diffraction type particle size distribution analyzer HEROS (manufactured by JEOL Ltd.). Among them, as shown in Table 1, channels having a channel upper limit value of more than 50 μm are added and expressed as a percentage of the whole.

[0028]

[Table 1] According to the present inventors, the universal hardness HU is 200N.
/ Mm ² or more, preferably 220 N / mm ² or more, and has a volume average particle diameter of 10 μm or more and 40 μm or more.
μm or less, preferably 15 μm or more and 35 μm or less, and further, the volume ratio of particles having a particle size of more than 50 μm is 2% or less,
It has been found that by using magnetic particles of preferably 1% or less, even in a so-called cleaner-less system, the photoreceptor does not suffer large scratches and the like, and image defects can be prevented. The upper limit of the universal hardness HU is not particularly limited, but may be about 350 N / mm ² as the upper limit.

The universal hardness HU is 200 N / mm ²
If less than, at the time of contact of the transfer body to the photoreceptor, the magnetic particles attached to the photoreceptor surface are embedded in the photoreceptor surface,
It is considered that an image defect occurs because a scratch is generated or abrasion occurs from the scratch.

The universal hardness HU is 200 N /
Even if the diameter is ² mm or more, if the ratio of the large particle size in the magnetic particles is large, the image defect still occurs, but this is due to the magnetic material sandwiched between the transfer body and the photosensitive body when the transfer body contacts the photosensitive body. It is considered that the area and the depth of the particles pressed into the surface of the photoreceptor are increased, thereby causing a flaw or abrasion starting from the flaw. That is, the particle size is 50μ.
When magnetic particles having a volume ratio of more than m and more than 2% are used, image defects occur.

The preferred range of the particle size of the magnetic particles is from 10 μm to 40 μm.
When it is smaller than 10 μm, the magnetic particles are liable to leak, and the magnetic particles are inferior in transportability when used as a magnetic brush. 40 μm
If the ratio exceeds, the charging uniformity of the injection charging method in the present invention tends to deteriorate. More preferably 15 μm or more, 3
5 μm or less.

Further, as a preferable range of the shape of the magnetic particles, a range in which the ratio of the minor axis length / major axis length of the magnetic particles of 5 μm to 20 μm is 0.85 or less is used. 0.
If it exceeds 85, the durability of the magnetic particles will be poor. Preferably it is 0.80 or less, more preferably 0.75 or less. On the other hand, when it is less than 0.5, the fluidity as a charging member is extremely deteriorated, and it is not practical. Further, the smaller the ratio of the short axis length / the long axis length, the more easily the photoreceptor is damaged. In this respect, it is preferably 0.6 or more.

[0033]

FIG. 1 is a block diagram showing an embodiment of the present invention.
3 will be specifically described, but the present invention is not limited to this embodiment.

FIG. 1 is a schematic diagram showing an example of an image forming apparatus according to the present invention. The electrophotographic image forming apparatus of this embodiment is a laser beam printer of an electrophotographic process of a magnetic brush contact charging system, a reversal developing system, a contact transfer system having a detachable mechanism, and a cleanerless system.

A is a printer main body, and B is an image reader (image reading device) mounted thereon.

(1) Image Reader B In the image reader B, the original G is placed on the upper surface of a fixed original table 10 (transparent plate such as glass) with the surface to be copied facing downward, and not shown thereon. Cover.

The image reading unit 9 includes a document illuminating lamp 9a, a short focus lens array 9b, a CCD sensor 9c, and the like. When a copy start signal is input, the unit 9 is driven forward from the home position on the left side of the document table to the right side along the lower surface of the document table under the document table 10 to a predetermined forward end point. Is reached, the actuator is driven backward and returned to the initial home position.

In the forward drive process of the unit 9, the downward image surface of the placed set document G on the document table 10 is sequentially illuminated and scanned by the document illuminating lamp 9a of the unit 9 from the left side to the right side. The original surface reflected light of the illumination scanning light is imaged and incident on the CCD sensor 9c by the short focus lens array 9b.

The CCD sensor 9c includes a light receiving section, a transfer section, and an output section. The light signal is converted into a charge signal in the CCD light receiving unit, and the transfer unit sequentially transfers the light signal to the output unit in synchronization with the clock pulse. The output unit converts the charge signal into a voltage signal, amplifies the signal, reduces the impedance, and outputs the voltage signal. The analog signal thus obtained is subjected to well-known image processing, converted into a digital signal, and sent to the printer main unit A.

That is, the image information of the document G is photoelectrically read by the image reader B as a time-series electric digital pixel signal (image signal).

(2) Printer Body A The rotating drum type electrophotographic photosensitive member 1 is driven to rotate in the direction of arrow a at a predetermined peripheral speed (process speed) about a central support shaft. The photosensitive member 1 of this example has a diameter of about 180 m.
m, and is driven to rotate at a peripheral speed of about 130 mm / sec. The photoreceptor 1 will be described in detail in section (3) below.

In the present embodiment, the photosensitive member 1 is uniformly charged to a predetermined polarity and potential by a magnetic brush contact charging device in the rotation process. In this example, almost -700v
The primary charging process is performed uniformly. The magnetic brush charger 3 as a contact charging member will be described later in detail in (4).

Then, with respect to the uniformly charged surface of the photosensitive member 1,
The laser exposure means (laser scanner) 2 performs scanning exposure with a laser beam L modulated in accordance with an image signal sent from the image reader B side to the printer main body A side, so that the surface of the photosensitive body 1 is exposed. , An electrostatic latent image corresponding to the image information of the document G photoelectrically read by the image reader B is sequentially formed.

The laser exposure means 2 comprises a solid-state laser element 2a, a rotating polygon mirror (polygon mirror) 2b, an f-θ lens group 2c, a deflecting mirror 2d and the like. On / off emission control of the solid-state laser element 2a is performed at a predetermined timing by a light emission signal generator (not shown) based on the input image signal. The laser light emitted from the solid-state laser element 2a is converted into a substantially parallel light beam by a collimator lens system, scanned by a rotating polygon mirror 2b rotating at high speed, and transmitted through a f-θ lens group 2c and a deflecting mirror 2d. An image is formed on the photoconductor 1 in a spot shape.

The photosensitive member 1 is scanned by such laser beam scanning.
The exposure distribution for one scanning of the image is formed on the surface, and the exposure distribution according to the image signal is obtained on the surface of the photosensitive member 1 by the sub-scanning caused by the rotation of the photosensitive member 1. That is,
ON / O corresponding to the image signal on the uniformly charged surface of the photosensitive member 1
An electrostatic latent image corresponding to a scanning exposure pattern is sequentially formed on the surface of the photoreceptor 1 by scanning the light of the solid-state laser element 2a whose FF light emission is controlled by a rotating polygon mirror 2b rotating at a high speed. . That is, on the surface of the photoreceptor 1, the potential of the exposed portion irradiated with the laser beam drops (bright portion potential), and the potential of the non-exposed portion not irradiated (dark portion potential).
, An electrostatic latent image corresponding to the exposure pattern is formed.

The electrostatic latent image formed on the surface of the photoreceptor 1 is successively developed as a toner image by the developing device 4 in the case of the present embodiment, and is reversely developed. The configuration of the developing device 4 will be described later in detail in section (5).

On the other hand, the transfer material P loaded and stored in the paper feed cassette 5 is fed out and fed one by one by the paper feed roller 5a, and is transferred to the photosensitive member 1 by the registration roller 5b at a predetermined control timing. Transfer device 7 as transfer means
The toner image on the surface of the photoconductor 1 is electrostatically transferred to the transfer material P on the transfer member 7e, which is a contact nip portion with the toner. The transfer device 7 in the present embodiment includes an endless transfer belt 7.
a is a belt transfer device which is suspended between the driving roller 7b and the driven roller 7c and has a detachable mechanism with respect to the photosensitive member 1.
Then, the photosensitive member 1 is rotated at a peripheral speed substantially equal to the rotational peripheral speed of the photosensitive member 1, and is detached from the photosensitive member 1 after the completion of image formation. A transfer charging blade 7d is provided inside the endless transfer belt 7a,
The transfer portion (transfer nip portion) 7e is formed by bringing the substantially middle portion of the belt portion of the belt 7a into contact with the drum surface of the photoreceptor 1 by the blade 7d.

The transfer material P is conveyed to the transfer section 7e on the upper surface of the belt 7a. When a predetermined transfer bias is supplied from the transfer bias application power supply S3 to the transfer charging blade 7d at the time when the leading end of the transport transfer material P enters the transfer portion 7e, charging of the opposite polarity to the toner from the back side of the transfer material P is performed. Then, the toner images on the photoconductor 1 are sequentially transferred to the upper surface of the transfer material P.

The transfer belt 7a also serves as a means for transporting the transfer material P from the transfer section 7e to the fixing device 6, and the transfer material P that has passed through the transfer section 7e is separated from the surface of the photoreceptor 1 and transferred to the transfer belt 7a. Then, the toner image is conveyed and introduced into the fixing device 6, and the toner image is thermally fixed, and is discharged to the paper discharge tray 8 as a copy or a print.

The printer body A of this embodiment does not include a dedicated cleaning device (cleaner) for removing the transfer residual toner remaining on the surface of the photosensitive member 1 after the transfer of the toner image to the transfer material P, and the developing device Reference numeral 4 denotes an apparatus of a cleanerless system which also serves as a cleaning unit for collecting transfer residual toner remaining on the surface of the photoconductor 1. This will be described in detail in (6) below.

Further, in the method and apparatus of the present invention, the process equipment such as the photoreceptor 1, the charging means 3, and the developing device 4 are detachably mounted on the main body of the image forming apparatus. It can also be of a device configuration.

(3) Photoreceptor 1 The electrophotographic photoreceptor used in the present invention has the above-mentioned surface characteristics,
That is, an electrophotographic photoreceptor having a universal hardness HU of 200 N / mm ² or more in the surface film physical property test (however, a curve showing the relationship between the hardness H and the indentation depth h does not have an inflection point) It is.

The electrophotographic photoreceptor having such surface characteristics may be prepared, for example, by using a specific resin as a binder resin for the surface layer of the electrophotographic photoreceptor having a normal configuration so that the universal hardness value falls within the above range. It is obtained by using.

The means for adjusting the universal hardness include a binder resin and a charge generating material or a charge transporting material dispersed and dissolved in the binder resin, or a conductive material such as a metal and its oxide, nitride, salt, alloy and carbon. And the ratio of these are changed. That is, although it depends on the material dispersed in the binder resin, in the case of the above-described materials, generally, the smaller the material dispersed, the greater the universal hardness. Another means is to change the molecular weight of the binder resin, the number of polymerized functional groups, and the like. That is, when the molecular weight of the binder resin is increased, or when the degree of crosslinking of the resin is increased by increasing the number of polymerized functional groups, the universal hardness is increased.

The structure of the electrophotographic photosensitive member used in the present invention is not particularly limited as long as it has the above-mentioned surface characteristics and functions as an electrophotographic photosensitive member. Generally, a photoconductor in which a photosensitive layer is provided on a conductive support is used. A protective layer is provided on the photosensitive layer, and an undercoat layer or a conductive layer is provided between the conductive support and the photosensitive layer. May be provided. Therefore,
The outermost surface layer of the photoreceptor is a photosensitive layer or a protective layer, and these layers are composed of a binder resin and a charge generating material contained in the binder resin in an appropriate amount, or a charge transport material or a conductive material, an additive, and the like. You.

The photosensitive layer of the electrophotographic photosensitive member used in the present invention has a single layer or a laminated structure. For a single-layer structure,
The photosensitive layer contains both a charge generating material for generating carriers and a charge transporting material for transporting carriers. In the case of a laminated structure, a charge generation layer containing a charge generation material for generating carriers and a charge transport layer containing a charge transport material for transporting carriers are laminated to form a photosensitive layer. The surface layer may be formed on either the charge generation layer or the charge transport layer.

The thickness of the single-layer photosensitive layer is preferably from 5 to 100 μm, more preferably from 10 to 60 μm. In addition, the charge generation material and the charge transport material are 2 to the total mass of the layer.
It is preferably contained in an amount of from 0 to 80% by mass, and particularly preferably from 30 to
It is preferably 70% by mass. The single-layer photosensitive layer contains a binder resin in addition to the charge generation material and the charge transport material, and may contain an ultraviolet absorber, an antioxidant, and other additives as necessary.

In the laminated photosensitive layer, the thickness of the charge generation layer is preferably 0.001 to 6 μm, and particularly preferably 0.001 to 6 μm.
It is preferably from 01 to 2 μm. The content of the charge generation material is preferably from 10 to 100% by mass, and particularly preferably from 40 to 100% by mass, based on the total mass of the layer. The charge generation layer may be composed of only a charge generation material, but in other cases, it may contain a binder resin or the like. The thickness of the charge transport layer is 5 to 100.
μm, particularly preferably 10 to 60 μm. The content of the charge transporting material is preferably from 20 to 80% by mass, and particularly preferably from 30 to 70% by mass, based on the total mass of the layer. The charge transport layer contains a binder resin in addition to the charge transport material, and may contain other optional components similar to those described above.

The charge generating material used in the present invention includes phthalocyanine pigments, polycyclic quinone pigments, azo pigments,
Perylene pigment, indigo pigment, quinacridone pigment, azulenium salt dye, squarylium dye, cyanine dye,
Examples include a pyrylium dye, a thiopyrylium dye, a xanthene dye, a quinone imine dye, a triphenylmethane dye, a styryl dye, selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide.

The charge transport materials used in the present invention include pyrene compounds, carbazole compounds, hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, pyrazoline compounds, styryl compounds, and the like. And stilbene compounds.

As the binder resin used for the photosensitive layer, polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide,
Polyamide imide, polysulfone, polyallyl ale,
Polyacetal, phenolic resin, acrylic resin, silicone resin, epoxy resin, urea resin, allyl resin,
Alkyd resins and butyral resins are exemplified.
Further, reactive epoxy and (meth) acrylic monomers and oligomers can be used after mixing and curing.

The electrophotographic photosensitive member used in the present invention may have a protective layer laminated on the photosensitive layer as described above. The thickness of the protective layer is preferably 0.01 to 20 μm,
In particular, the thickness is preferably 0.1 to 10 μm. The protective layer usually has a structure in which a charge generation material or a charge transport material, a metal and an oxide, a nitride, a salt, an alloy, and a conductive material such as carbon are dispersed in a binder resin. Examples of the binder resin, charge generation material, and charge transport material used for the protective layer include the same materials as those used for the photosensitive layer.

The conductive support used in the electrophotographic photoreceptor of the present invention may be made of a metal or alloy such as iron, copper, nickel, aluminum, titanium, tin, antimony, indium, lead, zinc, gold, silver, or the like. Oxide, carbon, conductive resin and the like can be used. The shapes include a cylindrical shape, a belt shape, and a sheet shape. The conductive material may be molded, but may be applied as a paint or may be deposited. The conductive support used in this example is a cylindrical support having a diameter of about 180 mm as described above.

As described above, an undercoat layer may be provided between the conductive support and the photosensitive layer. The undercoat layer is mainly made of a binder resin, but may contain the conductive material or the compound having an acceptor property. As the binder resin used for the undercoat layer, polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide, polyamide imide, polysulfone, polyallyl ether, polyacetal, phenol resin,
Examples include acrylic resin, silicone resin, epoxy resin, urea resin, allyl resin, alkyd resin, and butyral resin.

Further, as described above, a conductive layer may be provided between the conductive support and the photosensitive layer. When the photoreceptor has both an undercoat layer and a conductive layer, usually, a conductive support, a conductive layer, an undercoat layer, and a photosensitive layer are laminated in this order. The conductive layer generally has a structure in which the conductive material is dispersed in a binder resin similar to that used for the undercoat layer.

As a method for producing the electrophotographic photosensitive member used in the present invention, a method is usually used in which an undercoat layer, a photosensitive layer, a protective layer and the like are laminated on a conductive support by vapor deposition or coating. . As a coating method, a bar coater, a knife coater, a roll coater, an attritor, an application using a spray or the like, a dip application, an electrostatic application, a powder application and the like are used. Further, in order to form the undercoat layer, the photosensitive layer, the protective layer, and the like by a coating method, a solution in which the constituent components are dissolved and dispersed in an organic solvent or the like for each layer, a dispersion liquid, or the like is applied by the above method. After that, the solvent may be removed by drying or the like. Alternatively, when a reaction-curable binder resin is used, the components of each layer are dissolved and dispersed in a resin raw material component and an appropriate organic solvent added as necessary, and a solution or dispersion is prepared by the above-described method. After the application, for example, the resin material is reacted and cured by heat, light, or the like, and the solvent may be removed by drying or the like, if necessary.

[0067] can be achieved by the injection charging described in, for example, Japanese Patent 08-69155 discloses, it is possible to prevent the generation of ozone, in the present invention, the photosensitive member 1, 10 ⁹
It is preferable to have a surface layer having a volume resistance of 10 to 10 ¹⁴ Ω · cm. This is because, in the case of charging involving generation of ozone, if the photoreceptor has high mechanical durability as in the present invention, the photoreceptor is likely to be degraded by ozone products. Because there is no.

(4) Magnetic Brush Charger 3 The magnetic brush charger 3, which is a contact charging member, is of a sleeve rotating type in this embodiment. FIG. 2 is an enlarged schematic cross-sectional view of the magnetic brush charger 3. As shown in FIG. 2, the magnetic brush charger 3 is disposed in contact with the photoreceptor 1 and acts as a contact charging member. A fixed magnet roller 3a, a non-magnetic sleeve 3b made of aluminum or the like having an outer diameter of about 20 mm and rotatably fitted around the magnet roller 3a concentrically, and the magnetic force of the magnet roller 3a inside the outer surface of the sleeve Is a horizontally long member long in the generatrix direction of the photoreceptor 1, including a magnetic brush portion 3c of charging magnetic particles (magnetic carrier) adhered and held in a brush shape.

The magnetic brush portion 3c is brought into contact with the surface of the photosensitive member 1 with a predetermined contact width. The contact part n1 is a charged area (charged part). In this example, the width of the charged area n1 formed by bringing the magnetic brush portion 3c into contact with the photoreceptor 1 was adjusted to about 8 mm.

As described above, the non-magnetic sleeve 3b is moved by the driving system (not shown) in the direction of arrow b, that is, in the rotation direction a of the photosensitive member 1 in the charging portion n1, which is the contact portion of the magnetic brush portion 3c with the photosensitive member 1. On the other hand, it is driven to rotate at a predetermined peripheral speed in the counter direction. In this example, the photosensitive member 1
The non-magnetic sleeve 3b is driven to rotate at about 180 mm / sec for a rotational peripheral speed of about 130 mm / sec. With the rotation of the non-magnetic sleeve 3b, the magnetic brush portion 3c, which is magnetically restrained and held on the outer peripheral surface of the non-magnetic sleeve 3b, rotates together with the non-magnetic sleeve 3b in the same direction as the non-magnetic sleeve 3b and rotates in the charged area n1. The surface of the photoconductor 1 is rubbed.

A predetermined charging bias is applied to the non-magnetic sleeve 3b by a charging bias applying power source S1. In this example, an oscillating voltage on which a DC voltage: -700 V alternating voltage: V _PP 1.4 kV, Vf = 1.0 kHz is superimposed is applied to the non-magnetic sleeve 3 b as a charging bias (A
C bias application method), the surface of the photoconductor 1 is almost -700 V
To be contact-charged.

As for the relative rotational speed of the photosensitive member 1 and the magnetic brush charger 3, the higher the rotational speed, the better the charging uniformity.

As the magnetic particles for charging constituting the magnetic brush portion 3c, a resin carrier formed by dispersing magnetite as a magnetic material in a resin and dispersing carbon black for conductivity and resistance adjustment, or ferrite For example, a magnetite whose surface is oxidized and reduced to adjust its resistance or a magnetite such as ferrite whose surface is coated with a resin and whose resistance is adjusted is used.

As the magnetic particles used in the present invention, ferrite particles are preferably used. Ferrite containing a metal element such as copper, zinc, manganese, magnesium, iron, lithium, strontium, and barium is preferably used.

The preferred range of the magnetic particle diameter is 10
The range from μm to 40 μm is used. 10 μm
If the diameter is smaller than the above range, the magnetic particles tend to leak, and the magnetic particles have poor transportability when used as a magnetic brush. If it exceeds 40 μm, the charging uniformity of the injection charging method of the present invention tends to deteriorate. More preferably, 15 μm or more, 35 μm
It is as follows.

The volume ratio of the magnetic particles occupying 5 μm or more and 15 μm or less is 10% or more,
It is preferably 0% or less, and if it is less than 10%, the durability and the like are inferior. If it exceeds 70%, the movement of the particles becomes poor and the uniformity of charging tends to be lost. Preferably, it is 15% or more and 60% or less. More preferably, it is 50% or less.

When the volume ratio of the magnetic particles occupied by particles of 2 μm or less is 5% or less, leakage of the magnetic particles during use is small and the practicability is high. Further, the content is more preferably 2% or less.

If the volume ratio of the magnetic particles occupying more than 50 μm of the magnetic particles exceeds 2%, the magnetic particles sandwiched between the transfer member and the photoreceptor will adhere to the surface of the photoreceptor when the transfer member contacts the photoreceptor. The area and depth to be pushed in become large, and scratches occur, or the scratches are used as starting points to cause image defects. Therefore, it is preferably at most 2%, more preferably at most 1%.

Further, as disclosed in JP-A-08-69149, magnetic particles having two or more peaks in the particle size distribution can be used. As an effect of providing two or more peaks, there is an effect of securing a conduction path, and an effect of durability can be obtained.

The definition of the plurality of peaks or shoulders is as described above.
In the measuring method using EROS (manufactured by JEOL Ltd.), the average value of the channel having the largest volume ratio of each channel is defined as the position of the main peak. Further, for the second and subsequent peaks or shoulders, the volume ratio of the channel of the main peak is 1/1 to the volume ratio of the channel.
Those having a volume ratio of 0 or more are defined as peaks or shoulders. If the ratio is smaller than 1/10, the effect is weakened. Preferably, for the main peak and the second or subsequent peak or shoulder, 5 μm to 30 μm
m, or 20 μm to 60 μm.

Further, as a preferable range of the shape of the magnetic particles, those having a ratio of minor axis length / major axis length of 0.85 or less of the magnetic particles of 5 μm to 20 μm are used.

The cause of the deterioration of the charging property due to the durability of the magnetic particles is that the surface of the magnetic particles is contaminated by foreign substances such as toner components or paper powder mixed into the charging member, the resistance value of the charging member increases, and the surface of the photoreceptor is sufficiently cleaned. It is impossible to charge, but by adopting the deformed shape mentioned above, the contact property with the surface of the photoreceptor is improved in the first place, and the edge of the magnetic particles has the effect of cleaning the surface of the magnetic particles. It is possible to improve the durability as compared with the magnetic particles of the above.

As will be described in detail in section (6) below, in the cleanerless system, the magnetic particles cause the transfer residual toner to be temporarily disturbed on the surface of the photoreceptor 1 or temporarily collected into the magnetic brush charger by scraping. Although the function also serves as a means, the above effect can be obtained more effectively by deforming the shape of the magnetic particles.

In other words, if the particles in the range of 5 μm to 20 μm have a shape in which the ratio of the minor axis length / major axis length is 0.85 or less, the scraping force of the transfer residual toner on the photoreceptor is high, and High effect. Preferably it is 0.80 or less, and if it is 0.75 or less, the effect is very high. On the other hand, 0.5
When the value is below, the fluidity as the charging member is extremely deteriorated, and it is not practically used. Further, the smaller the ratio of the short axis length / the long axis length, the more easily the photoreceptor is damaged. In this regard, preferably
0.6 or more.

The minor axis length of the particles exceeding 20 μm /
It is more effective if the major axis length is 0.85 or less.

Here, a method of separating a portion of 5 μm to 20 μm will be described. Prepare sieves having openings of 5 μm and 20 μm. These sieves have a size of φ75 mm × H20 mm, and the method of forming openings of 5 μm or 20 μm is adjusted by thickening the wire diameter of the sieve by plating or the like. Open from above, 25μm, 20μm, 5μ
The sieves are stacked in the order of m, and 0.5 g of magnetic particles are placed on a sieve having an opening of 25 μm, sufficiently vibrated, and magnetic particles with a 20 μm pass and 5 μm on are collected. Further, what was left on the 5 μm sieve was subjected to a differential pressure of 200 mmAq to 5 μm.
Remove m-pass particles. This sample is used for measurement. As a sample having a size exceeding 20 μm, magnetic particles of 20 μm and 25 μm among the above sieves are mixed to obtain a sample. In the case of magnetic particles, the ratio of the minor axis length / major axis length is, for example, FE-SE manufactured by Hitachi, Ltd.
Using M (S-800), 100 magnetic particle images magnified 500 times are randomly extracted, and based on the image information, for example, an image analyzer (Image Anal) is used.
yzer) It is the arithmetic average value of the result of image analysis by V10 (manufactured by Toyobo Co., Ltd.).

The details of the analysis are as follows. First, from an electron micrograph, an image signal that has passed through a stereomicroscope is input to an analyzer, and the image information is binarized. Next, the following analysis is performed based on the binarized image information.

For details, refer to Image Analyzer
There is a description in V10 (Toyobo Co., Ltd.) manual,
In brief, the method is to take the ratio of the major axis to the minor axis of the ellipse through a procedure for replacing the shape of the object with the ellipse. The procedure is as follows. With respect to the binarized shape of the magnetic particles, coordinates (u,
Assuming that the specific gravity of the small area Δs = Δu · Δv in v) is 1, with respect to the origin (X, Y), it passes through the center of gravity of the binarized shape of the particle and is 2 with respect to the horizontal axis and vertical axis.
Second moment (second moment Mx about the horizontal axis,
The second moment My about the vertical axis is represented by Mx = ΣΣ (u−X) ² My = ΣΣ (v−Y) ² , and the inertia synergistic moment Mxy is given by Mxy = ΣΣ (u−X) · ( v−Y), and the angle θ that satisfies the following equation has two solutions.

[0089]

(Equation 1)

Further, the moment of inertia in the axial direction forming an angle θ with the horizontal axis is represented by Mθ = Mx · cos2θ + My · sin2θ−Mxy · sin2θ, and is calculated by substituting the two solutions of θ. M
The smaller one of θ is the main axis.

Further, on an arbitrary axis,

[0092]

(Equation 2) When plotting the points corresponding to, these create an ellipse,
Assuming that the principal axis coincides with the inertia principal axis, if the direction in which the value of Mθ takes a small value is A and the larger one is B, the following ellipse is obtained. A · x ² + B · y ² = 1

In the present invention, the ratio of the minor axis length / major axis length to the above ellipse is

[0094]

(Equation 3) It is represented by

A preferred method for producing magnetic particles in the present invention is a method of pulverizing magnetic particles of 20 μm to 80 μm.

After pulverization, classification is performed as appropriate,
It can be used as it is, and if necessary, it can be used by mixing with other magnetic particles.

In particular, when a structure having a plurality of peaks is used, a method in which the pulverizing step is adjusted so as to leave a peak having a large particle size and a peak having a small particle size is preferably formed. Used.

Further, a production method by pulverizing a mass of ferrite is also possible, but it is preferable to pulverize ferrite particles from the viewpoint of efficiency.

On the other hand, the magnetic particles for charging used in the present invention preferably have a volume resistance of 1 × 10 ² to 1 × 10 ¹⁰ Ω · cm, and the photosensitive member 1 has an insulating defect such as a pinhole. Is considered, the resistance is 1 × 10 ⁴ Ω · c
It is preferable to use those having m or more. In terms of magnetic particle leakage, a resistance of 1 × 10 ⁶ Ωcm or more is more preferably used.

Conversely, in order to improve the charging performance, it is better to use one having as small a resistance as possible. 1 × 10 ⁹ Ωcm
If the ratio exceeds, the charging of the photoconductor becomes insufficient.

The method of measuring the volume resistance of the magnetic particles is as follows. A cell A shown in FIG. 4 is filled with magnetic particles, electrodes 51 and 52 are arranged in contact with the magnetic particles, and a voltage is applied between the electrodes. It was obtained by measuring the flowing current. The measurement conditions were as follows: the contact area between the filled magnetic particles and the electrode was 2 cm ² , the thickness was 1 mm, the upper electrode was 10 kg, and the applied voltage was 100 V in an environment of 23 ° C. and 65%. 53 is a guide ring, 54 is an ammeter, 55 is a voltmeter, 56 is a constant voltage device, 57 is a measurement sample, and 58 is an insulator.

The charging magnetic particles used in the present invention have a saturation magnetization of 20 to 250 kA / m (20 to 250 em).
u / cm ³ ) is preferred.

In this embodiment, a rotary type charger is used as the magnetic brush charger 3 as the contact charging member, but the present invention is not limited to this configuration.

As a waveform of the primary charging alternating voltage component for the contact charging member, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. For example, the DC power supply is periodically turned ON / OF.
A rectangular wave voltage formed by performing F can also be used.

(5) Developing Device 4 In general, the developing method of an electrostatic latent image is roughly classified into the following four types. (A) Non-magnetic toner is coated on the sleeve with a blade or the like, and magnetic toner is coated on the sleeve by magnetic force, transported to the development area, and developed in a non-contact state with photoconductor 1 (1). Component non-contact development). (B) A method of developing the toner coated as described above in contact with the photoreceptor 1 (one-component contact development). (C) A method in which a mixture of a toner and a magnetic carrier is used as a developer, coated on a sleeve by magnetic force, transported to a development area, and developed in contact with the photoreceptor 1 (two-component contact). developing). (D) A method in which the two-component developer is developed in a non-contact state (two-component non-contact development).

In the present embodiment, which will be described in detail below, the two-component contact developing method (c) is used as a method for developing an electrostatic latent image, but other developing methods described above may be used. It is possible. Preferably, the one-component contact development (b) or the two-component contact development (c), in which the developer is developed in contact with the photoreceptor 1, is effective in further enhancing the simultaneous recovery effect during development. Actually, the two-component contact developing method (c) is often used from the viewpoint of high image quality and high stability of an image.

The developing device 4 in this embodiment is a two-component contact developing device (two-component magnetic brush developing device). FIG. 3 is an enlarged schematic cross-sectional view of the developing device 4. In FIG. 3, reference numeral 41 denotes a developing sleeve which is driven to rotate in the direction of arrow c; 42, a magnet roller fixedly arranged in the developing sleeve 41; 43, 44, a developer stirring screw;
Is a regulating blade arranged to form the developer T in a thin layer on the surface of the developing sleeve 41; 46 is a developing container;
Denotes a toner hopper for replenishment.

The developing sleeve 41 is arranged so that the area closest to the photosensitive member 1 is at least about 500 μm at least at the time of development, and a thin layer of the developer T formed on the surface of the developing sleeve 41 is exposed to light. It is set so that development can be performed in a state of contact with the body 1. n2 is a developer contact area (development area, development site) with respect to the photoconductor 1. The two-component developer T used in this example is a mixture of the toner particles t and the magnetic carrier c for development.

In the examples described later, the toner particles t were prepared by a suspension polymerization method and had a mass average particle diameter of 6 μm.
m, a negatively chargeable spherical toner (negative toner) was used.

The magnetic carrier c has a saturation magnetization of 2
05 kA / m (205 emu / cm ^Three 5) based on volume
A magnetic carrier having a 0% particle size of 35 μm was used.

A mixture of the toner particles t and the magnetic carrier c at a mass ratio of 6:94 was used as the developer T.

The developing sleeve 41 is driven to rotate at a predetermined peripheral speed in a direction indicated by an arrow c which is a forward direction to the rotating direction of the photosensitive member 1 in the developing area n2. With the rotation, the developer T in the developing container 46 is pumped by the S ₂ pole of the magnet roller 42 to the surface of the developing sleeve 41 and transported. In the process of being transported, the developer T is arranged perpendicular to the developing sleeve 41. The layer thickness is regulated by the regulating blade 45, and a thin layer of the developer T is formed on the developing sleeve 41. Napping is formed when the developer formed as a thin layer is conveyed to the developing area n2 corresponding to the developing pole S ₁ in transport pole N ₁ by a magnetic force. The electrostatic latent image on the photoconductor 1 is developed as a toner image in the development area n2 by the toner t in the developer T formed in the spike shape. In this example, the electrostatic latent image is reversely developed.

The developing sleeve 41 that has passed the developing area n2
The upper developer thin layer enters the developing container 46 with the subsequent rotation of the developing sleeve 41, is separated from the developing sleeve 41 by the repulsive magnetic field of the N ₃ and N ₂ poles, and
The developer T is returned to the pool of the developer T.

A DC voltage and an AC voltage are applied to the developing sleeve 41 from the power source S2. In this example, DC voltage: -480 V, alternating voltage: V _PP = 1.45 kV, Vf = 3.0 kHz are applied in a superimposed manner.

When an AC bias component is included in the developing bias applied to the developing device, the waveform of the AC bias may be a sine wave, a rectangular wave, a triangular wave, or the like. For example, a rectangular wave voltage formed by periodically turning on / off a DC power supply can be used.

In general, in the two-component developing method, when an alternating voltage is applied, the developing efficiency increases, and the quality of the image becomes high. On the contrary, there is a risk that fogging easily occurs. Therefore, normally, the DC voltage applied to the developing device 4 and the photoconductor 1
By providing a potential difference between the surface potentials, fogging can be prevented. More specifically, a bias voltage having a potential between the potential of the exposed portion of the photoconductor 1 and the potential of the non-exposed portion is applied.

The potential difference for preventing fogging is called a fog removing potential (Vback). Due to this potential difference, toner develops on the non-image area (non-exposed portion) of the surface of the photoreceptor 1 during development of the surface of the photoreceptor 1 In addition to preventing the toner from adhering, the cleaner-less system also collects the transfer residual toner on the surface of the photoconductor 1 (simultaneous cleaning with development). In the developing container 46, the toner concentration is monitored by a sensor (not shown) that detects the toner concentration of the developer T, and the toner t in the developer T is consumed for developing the latent image. Is lower than the predetermined density level, the replenishment toner hopper 47
Is replenished. By this toner replenishing operation, the toner concentration of the developer T is constantly maintained at a predetermined level.

(6) Cleanerless System The printer A of this example is provided with a dedicated cleaning device (cleaner) for removing the transfer residual toner remaining on the surface of the photoconductor 1 after the transfer of the toner image onto the transfer material P. This is a cleaner-less system device in which the developing device 4 also serves as a cleaning unit that collects the transfer residual toner remaining on the surface of the photosensitive member 1. . The transfer residual toner remaining on the surface of the photoconductor 1 after the transfer of the toner image to the transfer material P is transferred to the photoconductor 1 and the magnetic brush unit 3 c of the magnetic brush charger 3 by the subsequent rotation of the photoconductor 1.
Is carried to the charged area n1 which is a contact portion with the contact area. . In the charging area n1, the surface of the photoreceptor 1 is rubbed by the magnetic brush portion 3c of the magnetic brush charger 3, whereby
The transfer residual toner carried to the charging area n1 is disturbed and moved on the surface of the photoreceptor 1, and the pattern at the time of the transfer remaining is destroyed. Will be temporarily recovered. . The transfer residual toner adhering to and mixed with the magnetic brush portion 3c of the magnetic brush charger 3 is normal, including the toner whose polarity is reversed due to frictional charging with the charging magnetic particles constituting the magnetic brush portion 3c. It is recharged to the charging polarity (in this example, negative polarity). That is, the toner is converted into a normally charged toner. . Then, the magnetic brush unit 3 converted into the normally charged toner
The toner in c is discharged onto the photoreceptor 1 by an electric repulsion caused by the charging bias applied to the magnetic brush charger 3. . In this way, the toner that has been converted into the normally charged toner and discharged from the magnetic brush portion 3c of the magnetic brush charger 3 onto the photoconductor 1 is rotated by the subsequent rotation of the photoconductor 1.
To the developing region n2, which is a portion of the developing device 4 facing the developing sleeve 41, and the developing device 4
Collected at the back (simultaneous development cleaning).

Normally, the toner sequentially discharged from the magnetic brush charger 3 as a contact charging member onto the photosensitive member 1 is
It is a very thin layer in a small amount and in a uniformly dispersed state, and does not substantially adversely affect the next image exposure step. Further, generation of a ghost image due to the transfer residual toner pattern is also prevented.

(7) Photoreceptor surface characteristics, magnetic particle shape characteristics, and image life Normally, toner has a relatively high electric resistance. Increases the electrical resistance of the photosensitive member, thereby hindering the control of the surface potential of the photoconductor in the charging step, and causing factors such as poor charging, defective images due to the poor charging, and the like.

Among the contact charging members, the magnetic brush charger 3 is preferably used in a so-called cleaner-less system because the tolerance of toner mixing is relatively large.

However, when this magnetic brush contact charging member is used, not a small amount of magnetic particles are detached from the magnetic brush and adhere to the photoreceptor. Since the base material of the magnetic particles is made of an inorganic material, if the transfer member comes into contact with the photoconductor while the magnetic particles are adhered on the photoconductor, the magnetic particles are embedded in the photoconductor and scratches occur. As a result, an image defect or the like is caused.

This phenomenon was particularly remarkable when the shape of the magnetic particles was changed from the viewpoint of the durability of the magnetic particles.

Therefore, in the present invention, the universal hardness HU of the surface of the electrophotographic photosensitive member is 200 or more (however, the hardness H
And the indentation depth h of the indenter have no inflection point), the volume average particle diameter of the magnetic particles is 10 μm or more and 40 μm or less, and the particle diameter of the magnetic particles is 50 μm.
By setting the super-volume ratio to 2% or less, scratches on the photoreceptor are suppressed, and occurrence of image defects and the like is prevented.

[0125]

Embodiments of the present invention will be described below.

<Example 1> (1) Production of photoreceptor The following method was used to consist of an aluminum cylinder / conductive layer / subbing layer / charge generation layer / charge transport layer / surface protective layer. An OPC photosensitive member having a negatively charged polarity was prepared.

(I) Preparation of conductive layer In an aluminum cylinder having an outer diameter of 180 mm and a length of 360 mm, conductive titanium oxide ... 10 parts by mass (tin oxide coat, number average primary particle diameter 0.4 µm) Phenol resin precursor 10 parts by mass of methanol (butanol) ... 10 parts by mass of butanol ... 10 parts by mass of a dispersion obtained by sand mill dispersion dip coating.
By curing at 40 ° C, the volume resistance is 5 × 10 ⁹ Ω ·
A conductive layer having a thickness of 15 cm and a thickness of 15 μm was provided.

(Ii) Preparation of Undercoat Layer Next, the following methoxymethylated nylon (methoxymethylation degree: about 30%) 10 parts by mass

[0129]

Embedded image After mixing and dissolving 150 parts by mass of isopropanol, dip coating was performed on the conductive layer, and 1 μm
m undercoat layer was provided.

(Iii) Preparation of charge generation layer Next, diffraction angle 2θ ± 0.2 in X-ray diffraction of CuKα.
4 parts by mass of TiOPc (oxytitanium phthalocyanine) having strong peaks at 9.0 °, 14.2 °, 23.9 ° and 27.1 ° and polyvinyl butyral (trade name: Eslec BM2, manufactured by Sekisui Chemical) 2 After dispersing 4 parts by mass of 60 parts by mass of cyclohexanone and 60 parts by mass of cyclohexanone with a sand mill using a φ1 mm glass bead, 100 parts by mass of ethyl acetate was added to prepare a dispersion for a charge generation layer. This was dip-coated on the undercoat layer obtained above, and 0.3
A μm charge generation layer was provided.

(Iv) Preparation of Charge Transport Layer Next, the following triphenylamine: 10 parts by mass

[0132]

Embedded image Polycarbonate resin (Bisphenol Z type, viscosity average molecular weight 40000) ····· 10 parts by mass Monochlorobenzene ····· 50 parts by mass Dichloromethane ······ 15 parts by mass Dip coating on
An 8 μm charge transport layer was provided.

(V) Preparation of Surface Protective Layer Next, the following acrylic monomer: 18 parts by mass

[0134]

Embedded image Ultra fine particles of tin oxide having a number average particle diameter of 40 nm before dispersion: 50 parts by mass Polytetrafluoroethylene resin fine powder (number average particle size: 0.18 μm) 17 parts by mass Photopolymerization initiator , 4 parts by mass of ethanol 150 parts by mass of ethanol were dispersed in a sand mill for 66 hours. This prepared solution was applied onto the charge transport layer by dip coating, and 200 W
Light curing was carried out at a light intensity of / cm ² for 60 seconds, followed by hot air drying at 120 ° C. for 2 hours to obtain a surface layer. At this time,
The thickness of the obtained surface layer was 6 μm. This photoreceptor was used as a photoreceptor A for manufacturing the following electrophotographic image forming apparatus.

The universal hardness HU of the photoconductor A thus obtained in the surface film physical property test was 220 N /
mm ² .

(2) Production of Magnetic Particles The magnetic particles used in Example 1 were produced by the following method. Fe ₂ O ₃ 53 mol% CuO 23 mol% ZnO 24 mol% To these, phosphorus was added in an amount of 0.05 part by mass, pulverized and mixed by a ball mill, and a dispersant, a binder and water were added to form a slurry. Thereafter, a granulation operation was performed using a spray drier. After classification as appropriate, firing was performed at 1150 ° C. in the air, and the obtained ferrite was subjected to crushing treatment and then classified to obtain ferrite particles having a volume resistance of 5 × 10 ⁶ Ω · cm.

The magnetic particles were used as magnetic particles α in the production of the following electrophotographic image forming apparatus.

The magnetic particles α thus obtained have a volume average diameter of 25 μm, the ratio of the particles having a particle diameter of more than 50 μm is 1.4% by volume, and the minor axis length of the particles of 5 to 20 μm in the magnetic particles. / Long axis length was 0.80.

In Example 1, a digital full-color copying machine CLC-800 manufactured by Canon Inc. was used as an image evaluation device, in which the primary charger was modified to the above-described magnetic brush charger and the system was modified to a cleanerless system. Magnetic particles α
Was mounted on a charger so that the coating density became 180 mg / cm ^2, and photoreceptor A was mounted. This copier is
The transfer body is brought into contact with the photoconductor at the same time as the copy is started.
A mechanism is provided for detaching from the photoconductor at the end of copying.

When 30,000 copies of the image were repeatedly tested using this image evaluator, high-quality images could be maintained in all cases.

<Embodiment 2> In the present embodiment 2, the photosensitive member A used in the embodiment 1 was changed to the following, and the other device configuration was the same as the device of the embodiment 1.

(1) Production of Photoreceptor OPC of negative charge polarity comprising aluminum cylinder / conductive layer / subbing layer / charge generation layer / charge transport layer / surface protective layer used in Example 2 by the following method. A photoreceptor was made. (I) conductive layer / (ii) undercoat layer / (iii) charge generation layer / (i
v) Preparation of charge transport layer The preparation of the aluminum cylinder, the conductive layer, the undercoat layer, the charge generation layer, and the charge transport layer was the same as in Example 1, and the surface protective layer was formed in the following manner. (V) Preparation of surface protective layer The following acrylic monomer: 18 parts by mass

[0143]

Embedded image Ultra fine particles of tin oxide having a number average particle diameter of 40 nm before dispersion: 50 parts by mass Polytetrafluoroethylene resin fine powder (number average particle size: 0.18 μm) 17 parts by mass Photopolymerization initiator 4-methylthioxanthone 4 parts by mass ethanol 150 parts by mass was dispersed in a sand mill for 66 hours. This prepared solution was applied onto the charge transport layer by dip coating, and 200 W
Light curing was carried out at a light intensity of / cm ² for 60 seconds, followed by hot air drying at 120 ° C. for 2 hours to obtain a surface layer. At this time,
The thickness of the obtained surface layer was 6 μm. This photoconductor was used as a photoconductor B in the production of the following electrophotographic image forming apparatus.

The universal hardness HU of the photoconductor B thus obtained in the surface film physical property test was 270 N /
mm ² .

This photoreceptor B was mounted on a digital full-color copying machine CLC-800 modified by Canon Inc. as an image evaluation apparatus in the same manner as in Example 1.

When the image evaluator repeatedly tested 30,000 sheets, it was possible to maintain high quality images.

<Example 3> In Example 3, the magnetic particles α used in Example 1 were changed to the following.
The other device configuration was the same as the device of Example 1.

(2) Production of Magnetic Particles The magnetic particles used in Example 3 were produced by the following method. Fe ₂ O ₃ 54 mol% MnO 31 mol% MgO 15 mol%

These materials were pulverized and mixed by a ball mill, and a dispersant, a binder and water were added to form a slurry.
Granulation operation was performed with a spray dryer. After appropriately classifying, in an atmosphere in which the oxygen concentration is adjusted, 1200 ° C.
, And the obtained ferrite was subjected to crushing treatment and then classified to obtain ferrite particles having a volume resistance of 3 × 10 ⁷ Ω · cm.

The magnetic particles were used as magnetic particles β in the production of the following electrophotographic image forming apparatus.

The volume average diameter of the magnetic particles β thus obtained is 15 μm, the ratio of the particles having a particle diameter of more than 50 μm is 0.8% by volume, and the minor axis length of the particles of 5 μm to 20 μm of the magnetic particles. / Long axis length was 0.83.

The magnetic particles β were mounted on a digital full-color copying machine CLC-800 modified by Canon Inc., which is an image evaluation apparatus, in the same manner as in Example 1. When 30,000 copies were repeatedly tested with this image evaluator, high-quality images could be maintained in all cases.

<Embodiment 4> In Embodiment 4, the magnetic particles α used in Embodiment 1 were changed to the following.
The other device configuration was the same as the device of Example 1.

(2) Production of Magnetic Particles The magnetic particles used in Example 4 were produced by the following method. Fe ₂ O ₃ 53 mol% MnO 23 mol% ZnO 24 mol%

These materials were pulverized and mixed by a ball mill, and a dispersant, a binder and water were added to form a slurry.
Granulation operation was performed with a spray dryer. After being appropriately classified, fine powder is cut by an air classifier, and then calcined in a nitrogen atmosphere at 1200 ° C., and the obtained ferrite is subjected to crushing treatment and then classified to have a volume resistance of 2 × 10 ⁶ Ω.
・ Cm ferrite particles were obtained.

Further, 100 parts by mass of the above ferrite particles were added to a solution of 0.03 parts by mass of a titanium coupling agent, isopropoxytriisostearoyl titanate and 20 parts by mass of toluene, and the mixture was kept at 70 ° C. while stirring. After evaporating, put in a 200 ° C. oven,
Curing was performed.

The magnetic particles were used as magnetic particles γ in the following electrophotographic image forming apparatus.

The volume average diameter of the magnetic particles γ thus obtained is 35 μm, the ratio of the particles having a particle diameter of more than 50 μm is 1.8% by volume, and the minor axis length of the magnetic particles in the range of 5 μm to 20 μm. / Long axis length was 0.77.

As in Example 1, the magnetic particles γ were mounted on a digital full-color copying machine CLC-800 modified by Canon Inc., which is an image evaluation device. When 30,000 copies were repeatedly tested with this image evaluator, high-quality images could be maintained in all cases.

<Comparative Example 1> In Comparative Example 1, the photosensitive member A used in Example 1 was changed to the following, and the other device configuration was the same as that of Example 1.

(1) Production of Photoreceptor OPC of negative charge polarity comprising aluminum cylinder / conductive layer / subbing layer / charge generation layer / charge transport layer / surface protective layer used in Comparative Example 1 by the following method. A photoreceptor was made. (I) conductive layer / (ii) undercoat layer / (iii) charge generation layer / (i
v) Preparation of charge transport layer The preparation of the aluminum cylinder, the conductive layer, the undercoat layer, the charge generation layer, and the charge transport layer was the same as in Example 1, and the surface protective layer was formed in the following manner. (V) Preparation of surface protective layer The following acrylic monomer: 15 parts by mass

[0162]

Embedded image Ultrafine tin oxide particles having a number average particle size of 40 nm before dispersion .... 50 parts by mass Polytetrafluoroethylene resin fine powder (number average particle size 0.18 μm)... 20 parts by mass Photopolymerization initiator 20 parts by mass ethanol 150 parts by mass were dispersed in a sand mill for 66 hours. This prepared solution was applied onto the charge transport layer by dip coating, and 200 W
Photocuring was performed at a light intensity of / cm ² for 60 seconds, followed by drying with hot air at 120 ° C. for 2 hours to obtain a surface layer. At this time,
The thickness of the obtained surface layer was 6 μm. This photoreceptor was used as a photoreceptor C in the production of the following electrophotographic image forming apparatus.

The universal hardness HU of the photoconductor C thus obtained in the surface film physical property test was 185 N /
mm ² .

The photosensitive member C was mounted on a digital full-color copying machine CLC-800 manufactured by Canon Inc., which is an image evaluation apparatus, in the same manner as in Example 1.

Repeated tests were carried out with this image evaluator. As a result, spots on the image were found after 20,000 sheets.

<Comparative Example 2> In Comparative Example 2, the magnetic particles were changed to the magnetic particles γ used in Example 4 with coarser classification. The magnetic particles were used as magnetic particles δ in the production of the following electrophotographic image forming apparatus.

The magnetic particles δ thus obtained have a volume average diameter of 35 μm, a ratio of particles having a particle diameter of more than 50 μm is 2.5% by volume, and a minor axis length of the particles of 5 to 20 μm in the magnetic particles. / Long axis length was 0.75.

In the same manner as in Example 1, the magnetic particles δ were mounted on a digital full-color copying machine CLC-800 modified by Canon Inc., which is an image evaluation device.

Repeated tests were performed with this image evaluator. As a result, spot-like scratches were formed on the image after 15,000 sheets.

<Comparative Example 3> In Comparative Example 3, the magnetic particles were changed to the magnetic particles γ used in Example 4 with a further coarser classification. This magnetic particle was used as a magnetic particle ε in the production of the following electrophotographic image forming apparatus.

The magnetic particles ε thus obtained have a volume average diameter of 45 μm, a ratio of more than 50 μm is 5.2 volume%, and a minor axis length of the magnetic particles of 5 μm to 20 μm. / Long axis length was 0.77.

As in Example 1, the magnetic particles ε were mounted on a modified digital full-color copying machine CLC-800 manufactured by Canon Inc. as an image evaluation device. Repeated tests were performed with this image evaluator. After 3000 sheets, a streak-like image defect occurred on a white background portion of the image. This is presumably because charging uniformity was deteriorated. Also, 50
After 00 sheets, spot-like scratches occurred on the image.

[0173]

According to the present invention, as described above,
The charged member made of magnetic particles comes into contact with the photoconductor
Applying a voltage to charge the photoreceptor;
Exposing the latent image to form a latent image,
Visualization development process, process of transferring the toner image to a transfer material
And the transfer member used in the transfer step is the photosensitive member.
Image forming method having a mechanism for attaching and detaching to and from
And a universal film physical property test for the photoreceptor.
Hardness HU is 200N / mm ^Two(However, hardness H and indenter
(The curve showing the relationship with the indentation depth h has no inflection point.)
And the volume average particle diameter of the magnetic particles is 10 μm or more and 40 μm or more.
μm or less, and the volume of the magnetic particles exceeds 50 μm.
The ratio is set to 2% or less. As a result
To prevent damage to the photoreceptor caused by attaching and detaching the transfer means.
Electrophotographic image forming method and electrophotographic image forming
Equipment and a process cartridge can be provided.
You.

[Brief description of the drawings]

FIG. 1 is an example of an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is an enlarged cross-sectional model view of a magnetic brush charger 3 in the image forming apparatus shown in FIG.

FIG. 3 is an enlarged cross-sectional model diagram of a developing device 4 in the image forming apparatus shown in FIG. 1;

FIG. 4 is a view schematically showing an apparatus for measuring the volume resistance of magnetic particles.

FIG. 5 is a diagram schematically showing a measuring device for a surface film physical property test.

FIG. 6 is a diagram illustrating an example of a relationship curve between the hardness H and the indentation depth h of the indenter in the surface film physical property test for the surface layer, which does not generate an inflection point.

FIG. 7 is a diagram illustrating an example of a curve having an inflection point in a relationship curve between hardness H and indentation depth h in a surface film physical property test for a surface layer.

[Explanation of symbols]

Reference Signs List A Printer body B Image reader 1 Photoreceptor drum 2 Laser exposure means 3 Magnetic brush charger (contact charging member) 4 Developing device 5 Paper feed cassette 6 Fixing device 7 Transfer device 8 Discharge tray P Transfer material 9 Reading device, information processing Device, storage device, communication device, etc. 10 platen 31 sample 32 sample table 33 indenter 34 movable table

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Takagi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon F term (for reference) 2H003 AA00 AA18 BB11 CC04 2H032 AA05 BA18 BA23 2H068 AA03 AA08 AA13 AA34 AA35 FA03 2H077 AA37 AC16

Claims (12)

[Claims] 1. A step of contacting an electrophotographic photosensitive member having a photosensitive layer on a conductive support with a charging member made of magnetic particles, applying a voltage to charge the photosensitive member, and exposing the photosensitive member to light. Forming a latent image with a toner, developing the latent image with toner, transferring the toner image to a transfer material, and a mechanism for attaching and detaching a transfer member used in the transfer process to and from the photoconductor. The electrophotographic image forming method according to claim 1, wherein a curve showing the relationship between the hardness H of the photoreceptor and the indentation depth h does not have an inflection point. Hardness HU is 200N
/ Mm ² or more, and the volume average particle diameter of the magnetic particles is 10
μm or more and 40 μm or less, and the particle size of the magnetic particles is 5 μm or more.
An electrophotographic image forming method, wherein a volume ratio of more than 0 μm is 2% or less. 2. The electrophotographic image forming method according to claim 1, wherein said transferring step is a step of applying a voltage when said transferring member contacts said photosensitive member. 3. The electrophotographic image forming apparatus according to claim 1, wherein said developing step also serves as a cleaning step of recovering toner remaining on said photosensitive member after transfer. Method. 4. The magnetic particles have a particle size of 5 μm to 20 μm.
The electrophotographic image forming method according to any one of claims 1 to 3, wherein the ratio of the minor axis length to the major axis length of the particles in the portion is 0.85 or less. 5. A means for contacting an electrophotographic photosensitive member having a photosensitive layer on a conductive support with a charging member made of magnetic particles, applying a voltage to charge the photosensitive member, and exposing the photosensitive member to light. Means for forming a latent image by toner, developing means for visualizing the latent image with toner, means for transferring the toner image to a transfer material, and a mechanism for attaching and detaching a transfer member used for the transfer means to and from the photoconductor In the electrophotographic image forming apparatus having the above, under the condition that the curve indicating the relationship between the hardness H of the photoreceptor and the indentation depth h does not have an inflection point, the universal in the surface film physical property test of the photoreceptor Hardness HU is 200N
/ Mm ² or more, and the volume average particle diameter of the magnetic particles is 10
μm or more and 40 μm or less, and the particle size of the magnetic particles is 5 μm or more.
An electrophotographic image forming apparatus, wherein a volume ratio of more than 0 μm is 2% or less. 6. An electrophotographic image forming apparatus according to claim 5, wherein said transfer means is a means for applying a voltage when said transfer member contacts said photosensitive member. 7. The electrophotographic image forming apparatus according to claim 5, wherein said developing means also serves as a cleaning means for collecting toner remaining on said photosensitive member after transfer. apparatus. 8. The magnetic particles have a particle size of 5 μm to 20 μm.
The electrophotographic image forming apparatus according to any one of claims 5 to 7, wherein the ratio of the minor axis length to the major axis length of the particles in the portion is 0.85 or less. 9. A means for contacting an electrophotographic photosensitive member having a photosensitive layer on a conductive support with a charging member made of magnetic particles, applying a voltage to charge the photosensitive member, and exposing the photosensitive member to light. Means for forming a latent image by toner, developing means for visualizing the latent image with toner, means for transferring the toner image to a transfer material, and a mechanism for attaching and detaching a transfer member used for the transfer means to and from the photoconductor Wherein the photosensitive member and the contact charging means constituting the cartridge are integrally supported, are detachable from the image forming apparatus main body, and have a hardness of the photosensitive member. Under the condition that the curve showing the relationship between H and the indentation depth h does not have an inflection point, the universal hardness HU in the surface film physical property test of the photosensitive member is 200 N
/ Mm ² or more, and the volume average particle diameter of the magnetic particles is 10
μm or more and 40 μm or less, and the particle size of the magnetic particles is 5 μm or more.
A process cartridge wherein the volume ratio of more than 0 μm is 2% or less. 10. The process cartridge according to claim 9, wherein said transfer means is a means for applying a voltage when said transfer member comes into contact with said photosensitive member. 11. The process cartridge according to claim 9, wherein said developing means also serves as a cleaning means for collecting toner remaining on said photosensitive member after transfer. 12. The magnetic particles have a particle size of 5 μm to 20 μm.
The process cartridge according to any one of claims 9 to 11, wherein the ratio of the minor axis length / major axis length of the particles in the m portion is 0.85 or less.