JP7471928B2 - Image forming method - Google Patents

Description

The present invention relates to an image forming method for forming a toner image on an electrophotographic photoreceptor on which an electrostatic latent image has been formed in electrophotography, electrostatic recording, or electrostatic printing.

In general, a cylindrical electrophotographic photoreceptor is used as the electrophotographic photoreceptor that is rotated in an electrophotographic device. The surface (peripheral surface) of the electrophotographic photoreceptor is subjected to electrical and mechanical external forces such as charging and cleaning, and therefore is required to have durability (such as wear resistance) against these external forces. In response to this requirement, improvement techniques such as using a highly wear-resistant resin (such as a curable resin) in the surface layer of the electrophotographic photoreceptor have been used. However, by increasing the wear resistance of the peripheral surface of the electrophotographic photoreceptor, a problem of reduced cleaning performance has been raised.
In particular, since toner with low fluidity after durability is difficult to move laterally in the longitudinal direction of the electrophotographic photoreceptor, unevenness in the blocking layer occurs in the longitudinal direction, resulting in differences in the amount of external additive that slips through at the cleaning section, which causes the problem of uneven ghost concentration. To address this problem, if the initial toner fluidity is improved, the toner will penetrate too quickly into the blocking layer at the cleaning section, causing the toner to slip through the cleaning section.
In order to solve the above problems, a technique for containing fluorine-containing particles in the surface layer has been disclosed as a technique for improving the wear resistance and lubricity of the surface layer of an electrophotographic photoreceptor. Patent Document 1 describes a technique for containing a charge transporting polymer and fluorine-containing particles in the photosensitive layer, which is the surface layer of an electrophotographic photoreceptor. Patent Document 2 describes a technique for effectively dissolving and spreading the fluorine-containing particles by contacting a magnetic brush of a developer with the outermost surface layer containing the fluorine-containing particles.
However, while the electrophotographic photoreceptors of the above-mentioned prior art exhibit excellent wear resistance and lubricity, the fluorine-containing fine particles dispersed in the surface layer of the photoreceptor partially aggregate, and there is room for further improvement in wear resistance and lubricity in order to suppress ghost density unevenness of toner with low fluidity after durability testing.

JP 2001-305773 A JP 2012-88398 A

There is still room for further study on an image forming method that can provide a stable, high-quality image without the occurrence of initial toner slip-through and without the occurrence of ghost density unevenness even after durability testing.
The present invention provides an image forming method that solves the above problems, specifically, an image forming method that uses an electrophotographic photoreceptor that contains fluorine-containing fine particles having a specific molecular weight and crystallinity, and a toner having a flowability within a specific range.

The present invention relates to
a charging step of charging the surface of the photoconductor;
an electrostatic latent image forming step of forming an electrostatic latent image on the charged surface of the photoreceptor;
a developing step of developing the electrostatic latent image with a toner to form a toner image;
a transfer step of transferring the toner image onto a transfer material;
a cleaning step of removing residual toner remaining on the surface of the photoreceptor after the transfer step using a cleaning blade;
a fixing step of fixing the toner image transferred onto the transfer material;
An image forming method comprising the steps of:
The photoreceptor has a support and a photosensitive layer on the support,
The layer constituting the outermost surface of the photoreceptor contains polytetrafluoroethylene particles,
The polytetrafluoroethylene particles are
(i) the number average particle size of the primary particles is 200 nm or more and 500 nm or less;
(ii) the number average molecular weight is 20,000 or more and 28,000 or less;
(iii) the crystallinity is 78.0% or more and less than 83.0%;
The toner has toner particles containing a binder resin and an external additive,
In a powder fluidity analysis of the toner, a propeller-type blade is rotated at a peripheral speed of the outermost edge of the propeller-type blade at 100 mm/sec and penetrated vertically into a toner powder layer in a measurement container, and measurement is started from a position 100 mm from the bottom of the powder layer. The total sum Et of the rotational torque and the vertical load obtained when the blade penetrates to a position 10 mm from the bottom is 100 mJ or more and 2000 mJ or less.
The present invention relates to an image forming method.

The present invention makes it possible to provide an image forming method that can stably provide high-quality images without initial toner slippage and without ghost density unevenness even after durability testing.

FIG. 1 is a diagram showing an example of a schematic configuration of a process cartridge in which an electrophotographic photosensitive member of the present invention is mounted, and an electrophotographic apparatus including the process cartridge. FIG. 1 is an explanatory diagram of a propeller-type blade used in measuring Et.

In the present invention, the expressions "xx or more and xx or less" and "xx to xx" that express a numerical range refer to a numerical range including the lower and upper limit endpoints, unless otherwise specified.

The image forming method of the present invention comprises the steps of:
a charging step of charging the surface of the photoconductor;
an electrostatic latent image forming step of forming an electrostatic latent image on the charged surface of the photoreceptor;
a developing step of developing the electrostatic latent image with a toner to form a toner image;
a transfer step of transferring the toner image onto a transfer material;
a cleaning step of removing residual toner remaining on the surface of the photoreceptor after the transfer step using a cleaning blade;
a fixing step of fixing the toner image transferred onto the transfer material;
An image forming method comprising the steps of:
The photoreceptor has a support and a photosensitive layer on the support,
The layer constituting the outermost surface of the photoreceptor contains polytetrafluoroethylene particles,
The polytetrafluoroethylene particles are
(i) the number average particle size of the primary particles is 200 nm or more and 500 nm or less;
(ii) the number average molecular weight is 20,000 or more and 28,000 or less;
(iii) the crystallinity is 78.0% or more and less than 83.0%;
The toner has toner particles containing a binder resin and an external additive,
In a powder fluidity analysis of the toner, a propeller-type blade is rotated at a peripheral speed of the outermost edge of the propeller-type blade at 100 mm/sec and penetrated vertically into a toner powder layer in a measurement container, and measurement is started from a position 100 mm from the bottom of the powder layer. The total sum Et of the rotational torque and the vertical load obtained when the blade penetrates to a position 10 mm from the bottom is 100 mJ or more and 2000 mJ or less.
It is characterized by:

By controlling it within this range, initial toner slippage does not occur, ghost density unevenness does not occur even after durability testing, and a stable, high-quality image can be provided.

The inventors have considered the following method for providing a stable, high-quality image without initial toner slippage and without ghost density unevenness even after durability. The inventors focused on controlling the number-average particle size, number-average molecular weight, and crystallinity of the polytetrafluoroethylene particles contained in the layer constituting the outermost surface of the photoreceptor, and the powder fluidity of the toner. By controlling the number-average particle size, number-average molecular weight, and crystallinity of the polytetrafluoroethylene particles within the above ranges, the dispersibility of the polytetrafluoroethylene particles on the outermost surface of the photoreceptor is increased, and the wear resistance and lubricity are further improved. By combining with a toner whose fluidity is controlled within the above ranges, the particles tend to run horizontally in the longitudinal direction during cleaning, even in the initial and endurance periods, and the blocking layer becomes uniform, and it is believed that it is possible to provide a stable, high-quality image without ghost density unevenness.

The following describes in detail how to implement the present invention.

[Electrophotographic Photoreceptor]
The electrophotographic photoreceptor of the present invention has a conductive support, a charge generating layer and a charge transporting layer on the outer side of the conductive support in this order. In addition, a conductive layer or an undercoat layer, or both of them, may be provided between the conductive support and the charge generating layer. Furthermore, a surface layer may be provided on the outer side of the charge transporting layer.

A method for manufacturing the electrophotographic photoreceptor of the present invention includes preparing a coating liquid for each layer described below, coating the layers in the desired order, and drying the liquid. In this case, methods for applying the coating liquid include dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, dip coating is preferred from the viewpoints of efficiency and productivity.

Below, we will explain each component, such as the conductive support, conductive layer, undercoat layer, photosensitive layer, and surface layer (protective layer). In the explanation of the photosensitive layer, we will also explain (1) a laminated type photosensitive layer and (2) a single-layer type photosensitive layer.

<Conductive Support>
In the present invention, the electrophotographic photoreceptor has a conductive support. The conductive support may be in the form of a cylinder, a belt, a sheet, or the like. Of these, a cylindrical shape is preferred. The surface of the conductive support may be subjected to electrochemical treatment such as anodization, blasting, cutting, or the like.

The conductive support is preferably made of a metal, resin, glass, etc.

Metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys of these. Among these, an aluminum support using aluminum is preferred.

In addition, it is preferable to use resin or glass that has been given electrical conductivity by processing such as mixing or coating with a conductive material.

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

The conductive layer preferably contains conductive particles and a resin.

Materials for conductive particles include metal oxides, metals, carbon black, etc.

Metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, strontium titanate, magnesium oxide, antimony oxide, bismuth oxide, etc. Metals include aluminum, nickel, iron, nichrome, copper, zinc, silver, etc.

Among these, it is preferable to use metal oxides as conductive particles, and it is particularly preferable to use titanium oxide, tin oxide, and zinc oxide.

When using metal oxides as 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 elements such as phosphorus or aluminum or their oxides.

The conductive particles may also have a laminated structure having a core particle and a coating layer that covers the particle. Examples of the core particle include titanium oxide, barium sulfate, and zinc oxide. Examples of the coating layer include metal oxides such as tin oxide.

In addition, when metal oxides are used as conductive particles, the volume average particle diameter 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 conductive support or the conductive layer. By providing an undercoat layer, the adhesion between layers can be improved and a charge injection blocking function can be imparted.

The undercoat layer preferably contains a resin. Alternatively, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.

Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinylphenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin, polyimide resin, polyamideimide resin, and cellulose resin.

Examples of the polymerizable functional groups possessed by monomers having polymerizable functional groups include isocyanate groups, blocked isocyanate groups, methylol groups, alkylated methylol groups, epoxy groups, metal alkoxide groups, hydroxyl groups, amino groups, carboxyl groups, thiol groups, carboxylic anhydride groups, and carbon-carbon double bond groups.

The undercoat layer may further contain an electron transport material, a metal oxide, a metal, a conductive polymer, etc., for the purpose of improving electrical properties. Among these, it is preferable to use an electron transport material and a metal oxide.

Examples of electron transport substances 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. An electron transport substance having a polymerizable functional group may be used as the electron transport substance, and the undercoat layer may be formed as a cured film by copolymerizing the electron transport substance with the monomer having the polymerizable functional group described above.

Metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, strontium titanate, zinc oxide, aluminum oxide, silicon dioxide, etc. Metals include gold, silver, aluminum, etc.

The undercoat layer may further contain additives.

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.

The undercoat layer can be formed by preparing a coating solution for the undercoat 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 solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

<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 has 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 has 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 charge generating substances include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Of these, azo pigments and phthalocyanine pigments are preferred. Of the 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 average thickness of the charge generating layer is preferably 0.1 μm or more and 1 μm or less, and more preferably 0.15 μm or more and 0.4 μm or less.

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

(1-2) Charge Transport Layer The charge transport layer 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. These may be used alone or in combination of two or more.

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 a 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.

When the charge transport layer is the outermost surface of the electrophotographic photoreceptor (i.e., when the surface layer described below is not provided), the charge transport layer contains polytetrafluoroethylene particles having an average primary particle diameter of 200 nm or more and 500 nm or less.

The number average molecular weight of the polytetrafluoroethylene particles is 20,000 or more and 28,000 or less, and the crystallinity is 78% or more and less than 83%. The number average molecular weight of the polytetrafluoroethylene particles is more preferably 20,000 or more and 26,000 or less. The crystallinity is more preferably 80% or more and less than 83%. In addition, the average circularity of the polytetrafluoroethylene particles measured from a secondary electron image obtained by a scanning electron microscope is preferably 0.80 or more.

The polytetrafluoroethylene particles may be used alone or in a mixture of two or more types.

The average primary particle size, number average molecular weight, crystallinity, and circularity of the polytetrafluoroethylene particles of the present invention can be measured and calculated by the following methods.

(Method of measuring average primary particle size and average circularity)
The circularity is measured from a secondary electron image taken by a scanning electron microscope. A specific description is given below.

The average particle size and average roundness of the PTFE particles were measured using a field emission scanning electron microscope (FE-SEM). The PTFE particles were attached to a commercially available carbon conductive tape, and the PTFE particles not attached to the conductive tape were removed with compressed air, followed by platinum deposition. The deposited PTFE particles were observed using an FE-SEM (S-4700) manufactured by Hitachi High-Technologies Corporation. The measurement conditions for the FE-SEM were as follows:
Acceleration voltage: 2 kV
WD: 5mm
Magnification: 20,000 times Number of pixels: 1280 pixels vertically, 960 pixels horizontally (size of one pixel: 5 nm)

The Feret's diameters of 100 particles were determined from the obtained images using ImageJ (open source software from the National Institutes of Health (NIH)), and the average value was calculated to obtain the average particle diameter.

Similarly, the area and circumference were calculated, and the circularity was calculated from the formula (2), and the average value was calculated to obtain the average circularity.
Circularity = 4 x π x (area) ÷ (perimeter squared) Formula (2)

(Method of measuring number average molecular weight)
The number average molecular weight is calculated from the results of measurement by differential scanning calorimetry (hereinafter abbreviated as DSC), which will be specifically described below.

Measurements were performed under a nitrogen atmosphere using a METTLER TOLEDO DSC822e as the DSC. Polytetrafluoroethylene particles were placed in a 40 μl aluminum sample pan and heated from 25°C to 350°C at a heating rate of 16°C/min. The sample was then held at 350°C for 10 minutes and cooled to 280°C at a cooling rate of 16°C/min. The heat of crystallization ΔHc was calculated from the peak during this temperature drop.

The number average molecular weight Mn was calculated from the heat of crystallization ΔHc using formula (3).
Mn=2.1× ¹⁰¹⁰ ×ΔHc ^−5.16 Equation (3)

(Method of measuring crystallinity)
The crystallinity is measured by wide-angle X-ray diffraction under the following conditions.
X-ray diffraction equipment: Bruker AXS D8 ADVANCE
X-ray source: Cu-Kα ray (wavelength 0.15418 nm)
Output: 40kV, 40mA
Slit system: Slit DS, SS = 1°, RS = 0.2 mm
Measurement range: 2θ = 5° to 60°
Step interval: 0.02°
Scan speed: 1°/min

The wide-angle X-ray diffraction profile obtained under the above measurement conditions was separated into a crystal peak and an amorphous scattering peak, and the degree of crystallinity was calculated from their areas according to formula (4).
Crystallinity (%)=Ic/(Ic+Ia)×100 Formula (4)
Ic: Total area of crystalline peaks detected in the range of 5≦2θ≦60 Ia: Total area of amorphous scattering detected in the range of 5≦2θ≦60

The charge transport layer may further 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.

When the electrolytic transport layer is the outermost surface of the electrophotographic photoreceptor (i.e., no surface layer is provided), the average thickness of the charge transport layer is preferably 5 μm to 50 μm, and more preferably 30 μm to 45 μm. When a surface layer is provided on the charge transport layer, the average thickness of the charge transport layer is preferably 5 μm to 50 μm, more preferably 8 μm to 40 μm, and particularly preferably 10 μm to 30 μm.

The charge transport layer can be formed by preparing a coating liquid for the charge transport layer containing the above-mentioned materials and solvent, forming a coating film from this, and drying it. Examples of solvents used in the coating liquid 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.

(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 a coating film of this, 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".

<Surface layer (protective layer)>
In the present invention, a surface layer may be provided on the photosensitive layer. By providing the surface layer, the photosensitive layer is covered, so that the photosensitive layer can be protected from abrasion, and the durability of the electrophotographic photoreceptor can be improved.

The surface layer contains an abrasion resistance improver, a charge transport material, and a resin.

An example of an abrasion resistance improver is polytetrafluoroethylene particles with an average primary particle diameter of 200 nm or more and 500 nm or less.

The number average molecular weight of the polytetrafluoroethylene particles is 20,000 or more and 28,000 or less, and the crystallinity is 78.0% or more and less than 83.0%. The number average molecular weight of the polytetrafluoroethylene particles is more preferably 20,000 or more and 26,000 or less. The crystallinity is more preferably 80.0% or more and less than 83.0%. In addition, the average circularity of the polytetrafluoroethylene particles measured from a secondary electron image obtained by a scanning electron microscope is preferably 0.80 or more.

The polytetrafluoroethylene particles may be used alone or in a mixture of two or more types.

The average primary particle size, number average molecular weight, crystallinity, and circularity of the polytetrafluoroethylene particles of the present invention can be measured and calculated using the methods described above.

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.

Examples of resins include polyester resins, acrylic resins, phenoxy resins, polycarbonate resins, polystyrene resins, phenolic resins, melamine resins, and epoxy resins. Of these, (meth)acrylic resins are preferred.

The surface layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. The reaction may be a thermal polymerization reaction, a photopolymerization reaction, or a radiation polymerization reaction. The polymerizable functional group of the monomer having a polymerizable functional group may be a (meth)acrylic group. A material having a charge transport function may be used as the monomer having a polymerizable functional group. The charge transport function is a function obtained by having a charge transport group.

Furthermore, the surface layer may contain conductive particles. Examples of conductive particles include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide.

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

The average thickness of the surface layer is preferably 0.5 μm or more and 10 μm or less, and more preferably 1 μm or more and 7 μm or less.

The surface layer can be formed by preparing a coating solution 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 solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[Process Cartridge, Electrophotographic Apparatus]
The process cartridge of the present invention integrally supports the electrophotographic photosensitive member described above and at least one means selected from the group consisting of charging means, developing means, transfer means and cleaning means, and is detachably mountable to the main body of the electrophotographic apparatus.

The electrophotographic apparatus of the present invention also has the electrophotographic photoreceptor, charging means, exposure means, developing means and transfer means described above.

Figure 1 shows an example of the schematic configuration of an electrophotographic device having a process cartridge equipped with an electrophotographic photosensitive member.

1 is a cylindrical electrophotographic photoreceptor, which is driven to rotate at a predetermined peripheral speed in the direction of the arrow around the axis 2. The surface of the electrophotographic photoreceptor 1 is charged to a predetermined positive or negative potential by the charging means 3. In the figure, a roller charging method using a roller-type charging member is shown, but charging methods such as a corona charging method, a proximity charging method, and an injection charging method may be adopted. Exposure light 4 is irradiated from an exposure means (not shown) to the charged surface of the electrophotographic photoreceptor 1, and an electrostatic latent image corresponding to the target image information is formed. The electrostatic latent image formed on the surface of the electrophotographic photoreceptor 1 is developed with toner contained in the developing means 5, and a toner image is formed on the surface of the electrophotographic photoreceptor 1. The toner image formed on the surface of the electrophotographic photoreceptor 1 is transferred to a transfer material 7 by a transfer means 6. The transfer material 7 to which the toner image has been transferred is transported to a fixing means 8, where the toner image is fixed and printed out outside the electrophotographic device. The electrophotographic device may have a cleaning means 9 for removing deposits such as toner remaining on the surface of the electrophotographic photoreceptor 1 after transfer. Also, a so-called cleanerless system may be used in which the above-mentioned deposits are removed by a developing means or the like without providing a separate cleaning means. The electrophotographic device may have a charge-removing mechanism that performs a charge-removing process on the surface of the electrophotographic photoreceptor 1 with pre-exposure light 10 from a pre-exposure means (not shown). Also, a guide means 12 such as a rail may be provided to mount and remove the process cartridge of the present invention to and from the main body of the electrophotographic device.

The electrophotographic photoreceptor of the present invention can be used in laser beam printers, LED printers, copiers, facsimiles, and combination machines thereof.

[toner]
The toner of the present invention comprises toner particles containing a binder resin and an external additive,
In the powder fluidity analysis of the toner, a propeller-type blade is rotated at a peripheral speed of 100 mm/sec at the outermost edge thereof while being inserted vertically into the toner powder layer in a measurement container, and measurement is started from a position 100 mm from the bottom of the powder layer. The total sum Et of the rotational torque and the vertical load obtained when the blade is inserted to a position 10 mm from the bottom is 100 mJ or more and 2000 mJ or less (preferably 200 mJ or more and 1000 mJ or less).

When the above toner is used in the electrophotographic photoreceptor of the present invention, the penetration speed into the blocking layer formed in the cleaning section is suppressed even in the initial state, and sufficient lateral movement occurs in the blocking layer even after durability testing, preventing ghost density unevenness, making it possible to provide an image forming method that can provide stable, high-quality images.

The fluidity of the toner can be adjusted as appropriate by the selection of the grinder, grinding conditions, selection of the classifier, classification conditions, selection of the spheronization processing device, spheronization processing conditions, median particle size, particle size distribution, selection of external additives, external addition conditions, and external addition recipe.

[External additives (inorganic fine particles)]
Examples of the inorganic fine particles of the present invention include alkaline earth metal titanate particles such as strontium titanate particles, calcium titanate particles, and magnesium titanate particles; and alkali metal titanate particles such as potassium titanate particles.

Among these, strontium titanate particles, calcium titanate particles, and magnesium titanate particles having a perovskite crystal structure are preferred, and strontium titanate particles are more preferred, in view of the ease of controlling the fluidity of the toner particles.

The number-average particle diameter of the inorganic fine particles is preferably 20 nm or more and 300 nm or less, and more preferably 30 nm or more and 100 nm or less. In addition, in their particle size distribution, it is preferable that the peak top of the number frequency is within the above particle size range.

It is preferable that the inorganic fine particles have their particle surfaces rendered hydrophobic by a surface treatment agent. Examples of surface treatment agents that are preferable are fatty acids or metal salts thereof, disilylamine compounds, halogenated silane compounds, silicone oils, silane coupling agents, and titanium coupling agents, because they make it easier to control the fluidity of the toner particles.

The toner particles and the inorganic fine particles can be mixed using a known mixer such as a Henschel mixer, Mechano Hybrid (manufactured by Nippon Coke Corporation), a Super Mixer, or a Nobilta (manufactured by Hosokawa Micron Corporation), and is not particularly limited.

Strontium titanate particles, an example of the inorganic fine particles of the present invention, can be obtained by a normal pressure heating reaction method. In this case, it is preferable to use a mineral acid peptized product of a hydrolyzate of a titanium compound as the titanium oxide source, and a water-soluble acidic strontium compound as the strontium oxide source. The particles can be produced by reacting a mixture of these with an aqueous alkaline solution at 60°C or higher, followed by acid treatment.

(Normal pressure heating reaction method)
As the titanium oxide source, a mineral acid peptized product of a hydrolyzate of a titanium compound can be used. Preferably, metatitanic acid obtained by a sulfuric acid method and having an _SO3 content of 1.0% by mass or less, preferably 0.5% by mass or less, is peptized by adjusting the pH to 0.8 to 1.5 with hydrochloric acid.

Metal nitrates, hydrochlorides, etc. can be used as a source of strontium oxide, for example, strontium nitrate and strontium chloride can be used.

As the alkaline aqueous solution, caustic alkali can be used, but among them, sodium hydroxide aqueous solution is preferable.

In the method for producing strontium titanate particles, factors that affect the particle size include the mixing ratio of the titanium oxide source and the strontium oxide source during the reaction, the concentration of the titanium oxide source at the beginning of the reaction, and the temperature and addition rate when the alkaline aqueous solution is added. These can be adjusted as appropriate to obtain the desired particle size and particle size distribution. Note that it is preferable to prevent the inclusion of carbon dioxide gas, such as by carrying out the reaction under a nitrogen gas atmosphere, in order to prevent the formation of carbonates during the reaction process.

In the manufacturing method of the obtained strontium titanate particles, factors that affect the dielectric constant include conditions/operations that disrupt the crystallinity of the particles. In order to obtain strontium titanate particles with a particularly low dielectric constant, it is preferable to carry out an operation that imparts energy that disrupts crystal growth while increasing the concentration of the reaction solution. A specific method is, for example, adding microbubbling with nitrogen to the crystal growth process. The content of cubic and rectangular shaped particles can also be controlled by the flow rate of this microbubbling of nitrogen.

The mixing ratio of the titanium oxide source and the strontium oxide source during the reaction is preferably 0.9 to 1.4, more preferably 1.05 to 1.20, in terms of the molar ratio of SrO/ _TiO2 . Within the above range, unreacted titanium oxide is unlikely to remain. The concentration of the titanium oxide source at the beginning of the reaction is preferably 0.05 to 1.3 mol/L, more preferably 0.08 to 1.0 mol/L, in terms of _TiO2 .

The temperature when adding the alkaline aqueous solution is preferably 60°C to 100°C. The slower the addition rate of the alkaline aqueous solution, the larger the particle size of the strontium titanate particles that is obtained, and the faster the addition rate, the smaller the particle size of the strontium titanate particles that is obtained. The addition rate of the alkaline aqueous solution is preferably 0.001 to 1.2 equivalents/h, more preferably 0.002 to 1.1 equivalents/h, relative to the charged raw material, and can be adjusted appropriately depending on the particle size to be obtained.

(Acid Treatment)
It is preferable to further treat the strontium titanate particles obtained by the normal pressure heating reaction with an acid. When the normal pressure heating reaction is performed to synthesize the strontium titanate particles, if the mixing ratio of the titanium oxide source and the strontium oxide source exceeds 1.0 in the molar ratio of SrO/ _TiO2 , the unreacted metal source other than titanium remaining after the reaction may react with carbon dioxide gas in the air to generate impurities such as metal carbonates. If impurities such as metal carbonates remain on the surface, the organic surface treatment agent cannot be uniformly coated due to the influence of the impurities when performing an organic surface treatment to impart hydrophobicity. Therefore, it is preferable to perform an acid treatment to remove the unreacted metal source after adding an alkaline aqueous solution.

In the acid treatment, it is preferable to adjust the pH to 2.5 to 7.0, more preferably 4.5 to 6.0, using hydrochloric acid. In addition to hydrochloric acid, other acids such as nitric acid and acetic acid can be used for the acid treatment.

[Other external additives]
In addition to the inorganic fine particles described above, the toner may contain other inorganic fine powders as necessary to adjust the charge amount and fluidity. The inorganic fine powders may be added internally or externally to the toner particles. As the external additive, inorganic fine powders such as silica, titanium oxide, aluminum oxide, magnesium oxide, and calcium carbonate are preferred. The inorganic fine powders are preferably hydrophobized with a hydrophobizing agent such as a silane compound, silicone oil, or a mixture thereof.

With regard to the specific surface area of the external additive used, inorganic fine particles having a specific surface area of 10 m ² /g or more and 50 m ² /g or less are preferred from the viewpoint of suppressing embedding of the external additive.

The external additive is preferably used in an amount of 0.1 parts by weight to 5.0 parts by weight per 100 parts by weight of toner particles.

To mix the toner particles and the external additives, a known mixer such as a Henschel mixer can be used, but as long as the mixer can be mixed, there are no particular limitations on the device.

The toner of the present invention is a toner containing toner particles including a binder resin, and strontium titanate particles A and silica particles B as the external additives,
The strontium titanate particles A have a rectangular parallelepiped particle shape,
the content of the strontium titanate particles A is 0.3 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the toner particles,
The number average particle diameter of the primary particles of the silica particles B is 80 nm or more and 200 nm or less,
the adhesion rate of the strontium titanate particles A to the toner particles is 25% or more and 70% or less;
When the sucrose solution in which the toner is dispersed is centrifuged, the amount of the strontium titanate particles A separated per 1 g of toner is defined as YA (mg) and the amount of the silica particles B separated per 1 g of toner is defined as YB (mg),
YA is 3.00 or more and 18.0 or less,
From the viewpoint of improving cleaning properties, it is preferable that YA and YB satisfy the relationship of the following formula (1).
Y/Y>0.75 (1)

The adhesion rate of strontium titanate particles A and silica fine particles B, as well as the amount of separated external additives, can be measured by the following method.

Add 160 g of sucrose (Kishida Chemical) to 100 mL of ion-exchanged water and dissolve in a hot water bath to prepare a concentrated sucrose aqueous solution. In a 20 mL glass bottle, add 31 g of the concentrated sucrose aqueous 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, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) to prepare a dispersion. Add 1.0 g of toner to this dispersion and break up any clumps of toner with a spatula or similar.

The glass bottle containing the sample is shaken at 200 rpm for 5 minutes in a Yayoi shaker. After shaking, the solution is transferred to a glass tube for a swing rotor (50 mL) and centrifuged at 3,500 rpm for 30 minutes. This operation separates the toner particles from the removed external additives. It is visually confirmed that the toner layer and the water layer are sufficiently separated, and the toner in the top layer of the toner layer (the interface with the water layer) is collected with a spatula or the like. The collected toner is filtered with a vacuum filter and then dried in a dryer for at least 1 hour to obtain toner particles from which the external additives have been separated.

The adhesion rate of strontium titanate particles A is measured as follows. First, the amount of strontium titanate particles A contained in the toner before the above separation process is quantified. This is done by measuring the Sr element strength: MB in the toner particles using an Axios advanced wavelength dispersive X-ray fluorescence analyzer (manufactured by PANalytical). Next, the Sr element strength: MA of the toner after the above separation process is measured in the same manner.

The adhesion rate is calculated as (MA/MB) x 100 (%).

The separation amounts YA and YB are measured using MA and MB measured when measuring the adhesion rate, and the amounts (NA and NB) of strontium titanate particles A and silica particles B added to 1 g of toner.

The separation amount YA is ((MB)-(MA)) x NA/(MB),
The amount of separation YB is calculated by ((MB)-(MA))×NB/(MB).

The adhesion rate of strontium titanate particles A to toner particles is 25% or more and 70% or less. When the adhesion rate of strontium titanate particles A is within the above range, the fluidity of the toner that forms the blocking layer in the cleaning section is easily controlled, improving cleaning performance.

The adhesion rate of strontium titanate particles A is preferably 40% or more and 60% or less. The adhesion rate of strontium titanate particles A can be controlled by changing the rotation speed and rotation time when strontium titanate particles A are coated on toner particles using a mixer or the like.

In addition, when the amount of strontium titanate particles A separated per 1 g of toner is YA (mg) and the amount of silica particles B separated per 1 g of toner is YB (mg), YA is 3.00 or more and 18.0 or less. If YA is more than 18.0, the content of strontium titanate particles A in the toner decreases, so the fluidity of the toner decreases and the ghost density unevenness after durability worsens. If YA is less than 3.00, the blocking layer is not sufficiently formed and toner slip-through occurs.

YA is preferably 5.00 or more and 15.0 or less. YA can be controlled by changing the rotation speed and rotation time when strontium titanate particles A are coated on toner particles using a mixer or the like.

YB is preferably 1.00 or more and 7.00 or less, and more preferably 2.00 or more and 6.00 or less.

Further, YA and YB satisfy the relationship of the following formula (1).
Y/Y>0.75 (1)

If YA/YB is 0.75 or less, more silica particles B will be released than strontium titanate particles A, making it easier for silica particles B to slip through and worsening ghost density unevenness.

The upper limit of YA/YB is not particularly limited, but is preferably 3.00 or less, and more preferably 2.50 or less. YA/YB can be controlled by changing the rotation speed and rotation time when coating the toner particles with silica particles B using a mixer or the like. In addition, when changing YA or YB, it can be controlled by coating strontium titanate particles A and silica particles B in stages and changing the order of external addition, the rotation speed and rotation time of each.

The content of strontium titanate particles A is 0.3 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of toner particles. Preferably, it is 0.8 parts by mass or more and 1.5 parts by mass or less. If it is less than 0.3 parts by mass, the effect is not exhibited, and if it is more than 3.0 parts by mass, the fluidity of the toner is improved too much, causing toner slippage.

[Binder resin]
The binder resin used in the toner of the present invention is not particularly limited, and the following polymers or resins can be used.

For example, homopolymers of styrene and its substitutes such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers, styrene-acrylic acid ester copolymers, styrene-methacrylic acid ester copolymers, styrene-α-chloromethyl methacrylate copolymers, styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-vinyl ethyl ether copolymers, styrene-vinyl methyl ketone copolymers, and styrene-acrylonitrile-indene copolymers; polyvinyl chloride, phenolic resins, naturally modified phenolic resins, naturally modified maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethanes, polyamide resins, furan resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resins, coumarone-indene resins, and petroleum-based resins can be used.

Of these, polyester resins are preferred for their improved cleaning properties.

The polyester resin used in the present invention is a resin having a "polyester unit" in the binder resin chain, and the components constituting the polyester unit specifically include divalent or higher alcohol monomer components and acid monomer components such as divalent or higher carboxylic acids, divalent or higher carboxylic acid anhydrides, and divalent or higher carboxylic acid esters.

For example, examples of the dihydric or higher alcohol monomer component include alkylene oxide adducts of bisphenol A such as polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene (3.3)-2,2-bis(4-hydroxyphenyl)propane, polyoxyethylene (2.0)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene (2.0)-polyoxyethylene (2.0)-2,2-bis(4-hydroxyphenyl)propane, and polyoxypropylene (6)-2,2-bis(4-hydroxyphenyl)propane; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1, 4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerin, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, etc.

Among these, the alcohol monomer component preferably used is an aromatic diol, and the alcohol monomer component constituting the polyester resin preferably contains aromatic diol at a ratio of 80 mol % or more.

On the other hand, examples of the acid monomer components such as the divalent or higher carboxylic acid, the divalent or higher carboxylic acid anhydride, and the divalent or higher carboxylic acid ester include aromatic dicarboxylic acids or their anhydrides such as phthalic acid, isophthalic acid, and terephthalic acid; alkyl dicarboxylic acids or their anhydrides such as succinic acid, adipic acid, sebacic acid, and azelaic acid; succinic acid or its anhydride substituted with an alkyl group or alkenyl group having 6 to 18 carbon atoms; and unsaturated dicarboxylic acids or their anhydrides such as fumaric acid, maleic acid, and citraconic acid.

Among these, the preferred acid monomer components are polycarboxylic acids such as terephthalic acid, succinic acid, adipic acid, fumaric acid, trimellitic acid, pyromellitic acid, benzophenonetetracarboxylic acid, and their anhydrides.

In addition, from the viewpoint of improving cleaning properties, it is preferable that the acid value of the polyester resin is 20 mgKOH/g or less. Furthermore, it is more preferable that it is 15 mgKOH/g or less. If the acid value exceeds 20 mgKOH/g, the toner's moisture absorption becomes uneven, which deteriorates the fluidity and affects the cleaning properties.

The acid value can be adjusted to the above range by adjusting the type and amount of monomers used in the resin. Specifically, it can be controlled by adjusting the alcohol monomer component ratio/acid monomer component ratio and molecular weight during resin production. It can also be controlled by reacting the terminal alcohol with a polyacid monomer (e.g., trimellitic acid) after ester condensation polymerization.

[Crystalline polyester resin]
The toner of the present invention may also contain a crystalline polyester resin.

From the viewpoint of improving cleaning properties, the content of the crystalline polyester resin is preferably 5.0 parts by mass or more and 30.0 parts by mass or less, and more preferably 10.0 parts by mass or more and 20.0 parts by mass or less, per 100.0 parts by mass of the binder resin.

In the present invention, a crystalline resin is a resin in which an endothermic peak is observed in differential scanning calorimetry (DSC).

The crystalline polyester resin can be obtained by the reaction of a divalent or higher polyvalent carboxylic acid with a diol. Among them, a resin obtained by condensation polymerization of an aliphatic diol with an aliphatic dicarboxylic acid is preferable. In the present invention, the crystalline polyester resin may be used alone or in combination with multiple types.

In the present invention, the crystalline polyester resin is preferably a resin obtained by condensation polymerization of an alcohol component containing at least one compound selected from the group consisting of aliphatic diols having 2 to 22 carbon atoms and their derivatives, and a carboxylic acid component containing at least one compound selected from the group consisting of aliphatic dicarboxylic acids having 2 to 22 carbon atoms and their derivatives.

Among them, from the viewpoint of improving cleaning properties, it is more preferable that the crystalline polyester resin is a crystalline polyester resin obtained by polycondensation of an alcohol component containing at least one compound selected from the group consisting of aliphatic diols having 6 to 12 carbon atoms and their derivatives, and a carboxylic acid component containing at least one compound selected from the group consisting of aliphatic dicarboxylic acids having 6 to 12 carbon atoms and their derivatives.

The aliphatic diol having 2 to 22 carbon atoms (preferably 6 to 12 carbon atoms) is not particularly limited, but a chain (preferably linear) aliphatic diol is optimal from the viewpoint of improving cleaning properties.

For example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-butadiene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol.

Among these, preferred examples include straight-chain aliphatic α,ω-diols such as 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol.

In the present invention, the derivative is not particularly limited as long as it can obtain a similar resin structure by the above-mentioned condensation polymerization. For example, a derivative obtained by esterifying the above-mentioned diol can be mentioned.

In the present invention, in the alcohol component constituting the crystalline polyester resin, at least one compound selected from the group consisting of the aliphatic diols having 2 to 22 carbon atoms (preferably 6 to 12 carbon atoms) and their derivatives is preferably 50% by mass or more, more preferably 70% by mass or more, based on the total alcohol component.

In the present invention, polyhydric alcohols other than the above aliphatic diols can also be used.

Among the polyhydric alcohols, examples of diols other than the above aliphatic diols include aromatic alcohols such as polyoxyethylenated bisphenol A and polyoxypropylenated bisphenol A; 1,4-cyclohexanedimethanol, etc.

Among the polyhydric alcohols, examples of trihydric or higher polyhydric alcohols include aromatic alcohols such as 1,3,5-trihydroxymethylbenzene; and aliphatic alcohols such as pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerin, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, and trimethylolpropane.

Furthermore, in the present invention, monohydric alcohols may be used to the extent that they do not impair the properties of the crystalline polyester resin. Examples of such monohydric alcohols include n-butanol, isobutanol, sec-butanol, n-hexanol, n-octanol, 2-ethylhexanol, cyclohexanol, and benzyl alcohol.

On the other hand, the aliphatic dicarboxylic acid having 2 to 22 carbon atoms (preferably 6 to 12 carbon atoms) is not particularly limited, but may be a chain (preferably linear) aliphatic dicarboxylic acid.

For example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, glutaconic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, and itaconic acid.

These also include hydrolyzed versions of acid anhydrides or lower alkyl esters.

In the present invention, the derivative is not particularly limited as long as it is one that can obtain a similar resin structure by the above-mentioned condensation polymerization. For example, there are acid anhydrides of the above-mentioned dicarboxylic acid components, and derivatives obtained by methyl esterification, ethyl esterification, or acid chloride of the dicarboxylic acid components.

In the present invention, in the carboxylic acid component constituting the crystalline polyester resin, at least one compound selected from the group consisting of the aliphatic dicarboxylic acids having 2 to 22 carbon atoms (preferably 6 to 12 carbon atoms) and their derivatives is preferably 50% by mass or more, more preferably 70% by mass or more, of the total carboxylic acid component.

In the present invention, polyvalent carboxylic acids other than the above-mentioned aliphatic dicarboxylic acids can also be used. Among the polyvalent carboxylic acids, examples of divalent carboxylic acids other than the above-mentioned aliphatic dicarboxylic acids include aromatic carboxylic acids such as isophthalic acid and terephthalic acid; aliphatic carboxylic acids such as n-dodecyl succinic acid and n-dodecenyl succinic acid; and alicyclic carboxylic acids such as cyclohexane dicarboxylic acid, and also include their acid anhydrides or lower alkyl esters.

In addition, among other polyvalent carboxylic acids, examples of trivalent or higher polyvalent carboxylic acids include aromatic carboxylic acids such as 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and pyromellitic acid, and aliphatic carboxylic acids such as 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, and 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, as well as derivatives such as their acid anhydrides or lower alkyl esters.

Furthermore, in the present invention, monovalent carboxylic acids may be used to the extent that they do not impair the properties of the crystalline polyester resin. Examples of such monovalent carboxylic acids include benzoic acid, naphthalene carboxylic acid, salicylic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, phenoxyacetic acid, biphenyl carboxylic acid, acetic acid, propionic acid, butyric acid, and octanoic acid.

In the present invention, the crystalline polyester resin can be produced according to a conventional polyester synthesis method. For example, the carboxylic acid component and the alcohol component are subjected to an esterification reaction or an ester exchange reaction, and then the crystalline polyester resin can be obtained by carrying out a condensation polymerization reaction according to a conventional method under reduced pressure or by introducing nitrogen gas.

The above esterification or transesterification reaction can be carried out, if necessary, using a conventional esterification catalyst or transesterification catalyst such as sulfuric acid, titanium butoxide, tin 2-ethylhexanoate, dibutyltin oxide, manganese acetate, and magnesium acetate.

The condensation polymerization reaction can be carried out using a conventional polymerization catalyst, such as titanium butoxide, tin 2-ethylhexanoate, dibutyltin oxide, tin acetate, zinc acetate, tin disulfide, antimony trioxide, and germanium dioxide. The polymerization temperature and the amount of catalyst are not particularly limited and may be determined appropriately.

In the esterification or transesterification reaction, or polycondensation reaction, in order to increase the strength of the resulting crystalline polyester resin, it is possible to use a method in which all monomers are charged at once, or in order to reduce the amount of low molecular weight components, a divalent monomer is reacted first, and then a trivalent or higher monomer is added and reacted.

[wax]
The toner of the present invention may contain wax as necessary. Hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymers, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; oxides of hydrocarbon waxes such as oxidized polyethylene wax or block copolymers thereof; waxes mainly composed of fatty acid esters such as carnauba wax; partially or completely deoxidized fatty acid esters such as deoxidized carnauba wax. In addition, the following may be mentioned. Saturated straight-chain fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brassidic acid, eleostearic acid, and valinaric acid; saturated alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; polyhydric alcohols such as sorbitol; esters of fatty acids such as palmitic acid, stearic acid, behenic acid, and montanic acid and alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; fatty acid amides such as linoleic acid amide, oleic acid amide, and lauric acid amide; methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, hexamethylene saturated fatty acid bisamides such as bisstearamide; unsaturated fatty acid amides such as ethylene bisoleamide, hexamethylene bisoleamide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacamide; aromatic bisamides such as m-xylene bisstearamide and N,N'-distearyl isophthalamide; aliphatic metal salts (commonly known as metal soaps) such as calcium stearate, calcium laurate, zinc stearate, and magnesium stearate; waxes obtained by grafting aliphatic hydrocarbon waxes with vinyl monomers such as styrene and acrylic acid; partial esters of fatty acids and polyhydric alcohols such as behenic acid monoglyceride; and methyl ester compounds having a hydroxyl group obtained by hydrogenating vegetable oils and fats.

Among these waxes, Fischer-Tropsch wax is preferred from the viewpoint of controlling fluidity and improving cleaning properties.

The wax is preferably used in an amount of 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the binder resin. More preferably, the wax is used in an amount of 3.0 parts by mass or more and 12 parts by mass or less. From the viewpoint of improving the cleaning properties of the toner, it is preferable that the peak temperature of the maximum endothermic peak present in the temperature range of 30°C to 200°C in the endothermic curve during temperature rise measured by a differential scanning calorimeter (DSC) is 50°C to 110°C. More preferably, the peak temperature is 70°C to 100°C.

[Coloring agent]
Colorants (coloring materials) that can be contained in the toner of the present invention include the following.

Black colorants include carbon black, and those toned to black using yellow, magenta, and cyan colorants. As a colorant, a pigment may be used alone, but it is more preferable to use a dye and a pigment in combination to improve the clarity in terms of the image quality of a full-color image.

Magenta color pigments include: C.I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48:2, 48:3, 48:4, 49, 50, 51, 52, 53, 54, 55, 57:1, 58, 60, 63, 64, 68, 81:1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269, 282; C.I. Pigment Violet 19; C.I. Bat Red 1, 2, 10, 13, 15, 23, 29, 35.

Magenta coloring dyes include the following: C.I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; C.I. Disperse Red 9; C.I. Solvent Violet 8, 13, 14, 21, 27; C.I. Disperse Violet 1; C.I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; C.I. Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

Cyan coloring pigments include the following: C.I. Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, 17; C.I. Bat Blue 6; C.I. Acid Blue 45, copper phthalocyanine pigments with 1 to 5 phthalimidomethyl groups substituted on the phthalocyanine skeleton.

An example of a cyan coloring dye is C.I. Solvent Blue 70.

Yellow coloring pigments include: C.I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185; C.I. Vat Yellow 1, 3, 20.

Yellow coloring dyes include C.I. Solvent Yellow 162.

The content of the colorant is preferably 0.1 parts by weight or more and 30.0 parts by weight or less per 100 parts by weight of the binder resin.

[Magnetic material]
The toner of the present invention may be a magnetic toner or a non-magnetic toner. When used as a magnetic toner, it is preferable to use magnetic iron oxide as the magnetic material. As the magnetic iron oxide, iron oxide such as magnetite, maghematite, and ferrite is used. The amount of magnetic iron oxide contained in the toner is preferably 25 parts by mass or more and 95 parts by mass or less, more preferably 30 parts by mass or more and 45 parts by mass or less, based on 100 parts by mass of the binder resin.

[Charge control agent]
The toner of the present invention may contain a charge control agent as required. Known charge control agents may be used as the charge control agent contained in the toner, but metal compounds of aromatic carboxylic acids are particularly preferred because they are colorless, can charge the toner quickly, and can stably maintain a constant charge amount.

Negative charge control agents include metal salicylate compounds, metal naphthoate compounds, metal dicarboxylate compounds, polymeric compounds having sulfonic acid or carboxylic acid on the side chain, polymeric compounds having sulfonate or sulfonate ester on the side chain, polymeric compounds having carboxylate or carboxylate ester on the side chain, boron compounds, urea compounds, silicon compounds, and calixarenes. The charge control agent may be added internally or externally to the toner particles. The amount of charge control agent added is preferably 0.2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the binder resin.

[Developer]
The toner of the present invention can be used as a one-component developer, but in order to further improve dot reproducibility, it is preferable to mix it with a magnetic carrier and use it as a two-component developer. It is also preferable in that stable images can be obtained over a long period of time.

As magnetic carriers, for example, commonly known magnetic carriers can be used, such as surface-oxidized or unoxidized iron powder, metal particles such as iron, lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium, and rare earth elements, alloy particles thereof, oxide particles, magnetic materials such as ferrite, and magnetic material-dispersed resin carriers (so-called resin carriers) that contain magnetic materials and binder resins that hold the magnetic materials in a dispersed state.

When the toner of the present invention is mixed with a magnetic carrier to be used as a two-component developer, the mixing ratio of the magnetic carrier is preferably 2% by mass or more and 15% by mass or less, more preferably 4% by mass or more and 13% by mass or less, in terms of the toner concentration in the two-component developer.

[Production method]
The toner particles can be produced by any known method. Hereinafter, a toner production procedure using a pulverization method will be described as an example.

In the raw material mixing process, the materials constituting the toner particles, such as polyester resin, fatty acid metal salt, colorant, and other components such as release agent and charge control agent as necessary, are weighed out in predetermined amounts, blended, and mixed. Examples of mixing devices include a double-con mixer, V-type mixer, drum-type mixer, super mixer, Henschel mixer, Nauta mixer, and Mechano Hybrid (manufactured by Nippon Coke and Engineering Co., Ltd.).

Next, the mixed materials are melt-kneaded. The melt-kneading temperature is preferably about 100 to 200°C. In the melt-kneading process, a batch-type kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used, and a single-screw or twin-screw extruder is preferred because of its advantage of allowing continuous production. Examples include a KTK twin-screw extruder (manufactured by Kobe Steel, Ltd.), a TEM twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), a PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.), a twin-screw extruder (manufactured by KCK Corporation), a Co-Kneader (manufactured by Buss Co., Ltd.), and a Kneadex (manufactured by Nippon Coke and Engineering Co., Ltd.). Furthermore, the resin composition obtained by melt-kneading is rolled with a two-roll mill or the like, and quenched with water or the like in a cooling process.

The cooled resin composition is then pulverized to the desired particle size in a pulverization process. In the pulverization process, the resin composition is coarsely pulverized using a pulverizer such as a crusher, hammer mill, or feather mill, and then further pulverized using a pulverizer such as a Cryptron System (manufactured by Kawasaki Heavy Industries, Ltd.), a Super Rotor (manufactured by Nisshin Engineering Co., Ltd.), a Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.), or an air jet type pulverizer.

Then, if necessary, the toner particles are classified using a classifier or sieve such as the inertial classification type Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.), the centrifugal classification type Turboplex (manufactured by Hosokawa Micron Corporation), the TSP Separator (manufactured by Hosokawa Micron Corporation), or the Faculty (manufactured by Hosokawa Micron Corporation) to obtain a classified product (toner particles).

The obtained toner particles may be used as a toner as is. If necessary, an external additive may be added to the surface of the toner particles to form a toner. Methods for adding an external additive include blending a predetermined amount of the toner particles with various known external additives, and stirring and mixing the mixture using a mixing device such as a double con mixer, a V-type mixer, a drum mixer, a super mixer, a Henschel mixer, a Nauta mixer, a Mechano Hybrid (manufactured by Nippon Coke & Engineering Co., Ltd.), or a Nobilta (manufactured by Hosokawa Micron Corporation) as an external additive machine.

The toner of the present invention preferably has a volume-based median diameter of 3.0 μm or more and 20.0 μm or less, and more preferably 5.0 μm or more and 12.0 μm or less.

In the present invention, the average circularity of the toner is preferably 0.960 or more and 1.000 or less, and more preferably 0.960 or more and 0.980 or less. When the average circularity of the toner is in the above range, the cleaning properties of the toner are improved.

<Measurement of Weight Average Particle Size (D4) of Toner>
The weight average particle diameter (D4) of the toner is measured with an effective measurement channel count of 25,000 channels using a precision particle size distribution measuring device using a capillary electrical resistance method equipped with a 100 μm aperture tube, “Coulter Counter Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.), and the accompanying dedicated software for setting measurement conditions and analyzing measurement data, “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter, Inc.), and the measurement data is analyzed and calculated.

The electrolyte solution used for the measurements is one in which special grade sodium chloride is dissolved in ion-exchanged water to give a concentration of approximately 1% by mass, for example "ISOTON II" (manufactured by Beckman Coulter).

Before performing measurements and analysis, configure the dedicated software as follows:

In the "Change Standard Measurement Method (SOM) Screen" of the dedicated software, set the total count number in control mode to 50,000 particles, the number of measurements to 1, and the Kd value to the value obtained using "Standard Particle 10.0 μm" (manufactured by Beckman Coulter). Press the threshold/noise level measurement button to automatically set the threshold and noise level. Also, set the current to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and check the aperture tube flush after measurement.

In the dedicated software's "Pulse to particle size conversion setting screen," set the bin interval to logarithmic particle size, the particle size bin to 256 particle size bins, and the particle size range to 2 μm to 60 μm.

The specific measurement method is as follows.
(1) Pour about 200 mL of the electrolyte solution into a 250 mL round-bottom glass beaker for use with the Multisizer 3, set it on the sample stand, and stir the stirrer rod counterclockwise at 24 rotations per second. Then, remove dirt and air bubbles from inside the aperture tube using the "aperture flush" function of the dedicated software.
(2) Approximately 30 mL of the aqueous electrolyte solution is placed in a 100-mL flat-bottom glass beaker, and approximately 0.3 mL of a solution prepared by diluting "Contaminon N" (a 10% by weight aqueous solution of a neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, having a pH of 7, manufactured by Wako Pure Chemical Industries, Ltd.) three times by weight with ion-exchanged water is added thereto as a dispersant.
(3) A predetermined amount of ion-exchanged water is placed in the water tank of an ultrasonic disperser "Ultrasonic Dispersion System Tetora 150" (manufactured by Nikkaki Bios Co., Ltd.) having two built-in oscillators with an oscillation frequency of 50 kHz and a phase shift of 180 degrees and an electrical output of 120 W, and about 2 mL of the Contaminon N is added to this water tank.
(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid surface of the electrolytic solution in the beaker is maximized.
(5) In a state where the electrolyte solution in the beaker in (4) is irradiated with ultrasonic waves, about 10 mg of toner is added little by little to the electrolyte solution and dispersed. Then, ultrasonic dispersion treatment is continued for another 60 seconds. During ultrasonic dispersion, the water temperature in the water tank is appropriately adjusted so as to be 10°C or higher and 40°C or lower.
(6) The electrolytic solution (5) in which the toner is dispersed is dropped using a pipette into the round-bottom beaker (1) placed in the sample stand, and the measurement concentration is adjusted to about 5%. Then, the measurement is continued until the number of particles measured reaches 50,000.
(7) The measurement data is analyzed using the dedicated software that comes with the device, and the weight-average particle size (D4) is calculated. Note that when the dedicated software is set to Graph/Volume %, the "Average diameter" on the Analysis/Volume Statistics (Arithmetic Mean) screen is the weight-average particle size (D4).

<Measurement of average circularity>
The average circularity of the toner is measured using a flow type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation) under the measurement and analysis conditions during the calibration process.

The specific measurement method is as follows:

First, about 20 mL of ion-exchanged water from which solid impurities have been removed is placed in a glass container. About 0.2 mL of a solution of "Contaminon N" (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments with a pH of 7, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) diluted about three times by mass with ion-exchanged water is added as a dispersant.

Add approximately 0.02 g of the measurement sample and disperse it for 2 minutes using an ultrasonic disperser to obtain a dispersion for measurement. At this time, the dispersion is appropriately cooled so that the temperature is between 10°C and 40°C. As the ultrasonic disperser, a tabletop ultrasonic cleaner disperser (VS-150 (Velvoclear)) with an oscillation frequency of 50 kHz and an electrical output of 150 W is used, and a specified amount of ion-exchanged water is placed in the water tank, and approximately 2 mL of the Contaminon N is added to this water tank.

For the measurements, the flow type particle image analyzer equipped with a standard objective lens (10x) was used, and the particle sheath "PSE-900A" (manufactured by Sysmex Corporation) was used as the sheath liquid. The dispersion liquid prepared according to the above procedure was introduced into the flow type particle image analyzer, and 3,000 toner particles were counted in HPF measurement mode and total count mode.

Then, the binarization threshold for particle analysis is set to 85%, the analyzed particle diameter is limited to a circle equivalent diameter of 1.985 μm or more and less than 39.69 μm, and the average circularity of the toner is calculated.

When performing the measurement, automatic focus adjustment is performed using standard latex particles (Duke Scientific's "RESEARCH AND TEST PARTICLES Latex Microsphere Suspensions 5200A" diluted with ion-exchanged water) before starting the measurement. After that, it is preferable to perform focus adjustment every two hours from the start of the measurement.

In the examples, a flow-type particle image analyzer was used that had been calibrated by Sysmex Corporation and had a calibration certificate issued by Sysmex Corporation. Measurements were performed under the same measurement and analysis conditions as when the calibration certificate was received, except that the particle diameters analyzed were limited to equivalent circle diameters of 1.985 μm or more and less than 39.69 μm.

<Method of measuring Et>
For the measurement of Et, a powder fluidity analyzer equipped with a rotary blade (Powder Rheometer FT-4, manufactured by Freeman Technology Co., Ltd.) (hereinafter also referred to as "FT-4") was used.

The principle of the above device is to move a rotating blade through a powder sample, causing a flow in a certain pattern. The particles in the powder sample flow as the blade approaches and then stop again as it passes. The energy required for the blade to move through the powder is measured, and from this value, various flowability indices are calculated. The blade is propeller-shaped, and as it rotates it also moves upwards and downwards, so its tip draws a spiral. The angle and speed of the blade's spiral path can be adjusted by changing the rotation speed and up and down movement. When the blade moves along a clockwise spiral path relative to the powder bed surface, it has the effect of mixing the powder uniformly. Conversely, when the blade moves along a counterclockwise spiral path relative to the powder bed surface, the blade encounters resistance from the powder.

Specifically, measurements were performed using the following procedure. In all operations, the propeller blade used was a 48 mm diameter blade designed specifically for FT-4 measurements, with the specifications shown in Figure 2 (48 mm x 10 mm blade plate with a rotation axis in the normal direction at the center, and the blade plate smoothly twisted counterclockwise such that both outermost edges (24 mm from the rotation axis) are twisted at 70°, and the part 12 mm from the rotation axis is twisted at 35°; made of SUS; model number: C210; hereafter sometimes abbreviated as "blade")

First, 100 g of toner that had been left in an environment of 23°C and 60% humidity for more than 3 days was placed in a 50 mm x 160 ml split container (model number: C203. Height from the bottom of the container to the split part is 82 mm. Material is glass. Hereinafter, it may be abbreviated as container) designed specifically for FT-4 measurement to prepare a toner powder layer.

(1) Conditioning operation (a) The rotation speed of the blade (the peripheral speed of the outermost edge of the blade) was set to 60 (mm/sec). The vertical intrusion speed into the powder layer was set to a speed at which the angle between the path drawn by the outermost edge of the moving blade and the powder layer surface (hereinafter, sometimes abbreviated as "angle") was 5 (deg). The blade was intruded from the powder layer surface to a position 10 mm from the bottom surface of the toner powder layer in a clockwise rotation direction (the direction in which the powder layer is loosened by the rotation of the blade) with respect to the powder layer surface. Thereafter, the blade was rotated at a speed of 60 (mm/sec), and the vertical intrusion speed into the powder layer was set to a speed at which the angle was 2 (deg), in a clockwise rotation direction with respect to the powder layer surface, to a position 1 mm from the bottom surface of the toner powder layer. Thereafter, the blade was rotated at a rotation speed of 60 (mm/sec) and the angle of the extraction speed from the powder layer was 5 (deg), and the blade was moved in a clockwise direction with respect to the surface of the powder layer to a position 100 mm from the bottom surface of the toner powder layer to perform extraction. After the extraction was completed, the blade was rotated alternately in small clockwise and counterclockwise directions to brush off the toner adhering to the blade.
(b) The above series of steps (1)-(a) was repeated five times to remove air trapped in the toner powder layer, thereby forming a stable toner powder layer.

(2) Splitting Operation The toner powder layer was leveled off at the split portion of the above-mentioned FT-4 measurement cell, and the toner at the top of the powder layer was removed to form a toner powder layer of the same volume.

(3) Measurement procedure (a) The same procedure as in (1)-(a) above was carried out once.
(b) Next, the blade was rotated at a speed of 100 (mm/sec), and the vertical intrusion speed into the powder layer was set to an angle of 5 (deg). The blade was rotated counterclockwise (the direction in which the powder layer is pushed in by the rotation of the blade) with respect to the powder layer surface to a position 10 mm from the bottom surface of the toner powder layer. Thereafter, the blade was rotated at a speed of 60 (mm/sec), and the vertical intrusion speed into the powder layer was set to an angle of 2 (deg), and the blade was rotated clockwise with respect to the powder layer surface to a position 1 mm from the bottom surface of the powder layer. Thereafter, the blade was rotated at a speed of 60 (mm/sec), and the vertical intrusion speed from the powder layer was set to an angle of 5 (deg), and the blade was removed from the powder layer to a position 100 mm from the bottom surface of the powder layer in a clockwise direction with respect to the powder layer surface. After the removal was completed, the blade was rotated alternately in small clockwise and counterclockwise directions to brush off the toner adhering to the blade.
(c) The above series of operations (b) was repeated seven times.

In the above operation (c), when the rotation speed of the blade for the seventh time is 100 (mm/sec), the sum Et of the rotation torque and the vertical load obtained when the blade is inserted from 100 mm to 10 mm from the bottom surface of the toner powder layer is Et (mJ).

The present invention will be explained in more detail below with reference to the following manufacturing examples and working examples, but these are not intended to limit the present invention in any way. Note that the number of parts in the following formulations is based on weight unless otherwise specified.

<Production Example of Electrophotographic Photoreceptor 1>
Support A cylindrical aluminum cylinder (JIS-A3003, aluminum alloy, diameter 30 mm, length 357.5 mm, thickness 1.0 mm) was used as the conductive support.

Formation of Undercoat Layer 60 parts of zinc oxide particles (average particle size: 70 nm, specific surface area: 15 ^m2 /g) were mixed with 500 parts of tetrahydrofuran by stirring, and 0.75 parts of a silane coupling agent (compound name: N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, product name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto and stirred for 2 hours. Thereafter, the tetrahydrofuran was distilled off under reduced pressure, and the mixture was dried by heating at 120°C for 3 hours to obtain surface-treated zinc oxide particles.

Next, 25 parts of butyral (product name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) as a polyol and 22.5 parts of blocked isocyanate (product name: Sumidur BL-3173, manufactured by Sumitomo Bayern Urethane Co., Ltd.) were dissolved in 142 parts of methyl ethyl ketone. To this solution, 100 parts of the surface-treated zinc oxide particles and 1 part of anthraquinone were added, and the mixture was dispersed in a sand mill using glass beads with a diameter of 1 mm for 5 hours.

After the dispersion process, 0.008 parts of dioctyltin dilaurate and 6.5 parts of silicone resin particles (Tospearl 145, manufactured by GE Toshiba Silicones) were added and stirred to prepare a coating solution for the undercoat layer.

The obtained coating solution for the undercoat layer was dip-coated onto the support to form a coating film, and the coating film was dried at 190°C for 24 minutes to form an undercoat layer with a thickness of 15 μm.

Formation of Charge Generation Layer Next, 15 parts of chlorogallium phthalocyanine crystals having strong diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.4°, 16.6°, 25.5°, and 28.3° for CuKα characteristic X-rays, 10 parts of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Union Carbide Co., Ltd.), and 300 parts of n-butyl alcohol were mixed and dispersed for 4 hours in a sand mill using glass beads with a diameter of 1 mm to prepare a coating liquid for a charge generation layer.

This charge generating layer coating liquid was dip coated onto the undercoat layer, and the resulting coating was dried at 150°C for 5 minutes to form a charge generating layer with a thickness of 0.2 μm.

Formation of Charge Transport Layer Next, 8 parts of polytetrafluoroethylene particles (average primary particle size, number average molecular weight, crystallinity, and circularity are shown in Table 1) that had been heat-treated at 150° C. for 3 hours, 0.015 parts of a resin having a structural unit represented by the following structural formula (A) (weight average molecular weight: 130,000), 4 parts of tetrahydrofuran, and 1 part of toluene were stirred and mixed for 48 hours while maintaining a liquid temperature of 20° C., to obtain Preparation A.

Next, 4 parts of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1']biphenyl-4,4'-diamine, 6 parts of bisphenol Z-type polycarbonate resin (viscosity average molecular weight: 40,000), and 0.1 parts of 2,6-di-t-butyl-4-methylphenol as an antioxidant were mixed, and 24 parts of tetrahydrofuran and 11 parts of toluene were mixed and dissolved to obtain preparation B.

Preparation A was added to preparation B and mixed with stirring, then passed through a high-pressure disperser (product name: Microfluidizer M-110EH, manufactured by Microfluidics, Inc., USA) to obtain a dispersion.

Then, fluorine-modified silicone oil (product name: FL-100, manufactured by Shin-Etsu Silicone Co., Ltd.) was added to the dispersion to a concentration of 5 ppm, and the mixture was filtered through a polyflon filter (product name: PF-040, manufactured by Advantec Toyo Co., Ltd.) to prepare the coating liquid for the charge transport layer.

This charge transport layer coating liquid was dip-coated onto the charge generating layer to form a coating film, and the resulting coating film was dried at 150°C for 25 minutes to form a charge transport layer with a thickness of 30 μm.

In this way, electrophotographic photoreceptor 1 was produced.

<Production Examples of Electrophotographic Photoreceptors 2 to 13>
In the same manner as in the production example of the electrophotographic photoreceptor 1, the polytetrafluoroethylene particles were changed to those shown in Table 1, and electrophotographic photoreceptors 2 to 13 were produced.

<Production Example of Electrophotographic Photoreceptor 14>
An aluminum cylinder having a diameter of 30 mm, a length of 357.5 mm and a wall thickness of 1 mm was used as the conductive support.

Next, 100 parts of zinc oxide particles (specific surface area: 19 ^m2 /g, powder resistivity: 4.7 x ¹⁰⁶ Ω·cm) as a metal oxide were stirred and mixed with 500 parts of toluene, to which 0.8 parts of a silane coupling agent (compound name: N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, product name: KBM602, manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred for 6 hours. Thereafter, the toluene was distilled off under reduced pressure, and the mixture was dried by heating at 130°C for 6 hours to obtain surface-treated zinc oxide particles.

Next, 15 parts of butyral resin (product name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) as a polyol resin and 15 parts of blocked isocyanate (product name: Sumidur 3175, manufactured by Sumitomo Bayer Urethane Co., Ltd.) were dissolved in a mixed solution of 73.5 parts of methyl ethyl ketone and 73.5 parts of 1-butanol. To this solution were added 80.64 parts of the surface-treated zinc oxide particles and 0.8 parts of a compound represented by structural formula (B) (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was dispersed in a sand mill using glass beads with a diameter of 0.8 mm in an atmosphere of 23±3°C for 3 hours. After dispersion, 0.01 parts of silicone oil (product name: SH28PA, manufactured by Toray Dow Corning Silicone Co., Ltd.) and 5.6 parts of cross-linked polymethyl methacrylate (PMMA) particles (product name: TECHPOLYMER SSX-103, manufactured by Sekisui Plastics Co., Ltd., average primary particle size 3.1 μm) were added and stirred to prepare a coating solution for the undercoat layer.

The coating solution for the undercoat layer was dip-coated onto the support to form a coating film, which was then dried by heating at 145°C for 40 minutes to form an undercoat layer with a thickness of 18 μm.

Next, 11 parts of hydroxygallium phthalocyanine crystals (charge generating material) with a crystal form having strong peaks at 7.4° and 28.2° of Bragg angles (2θ±0.2°) in CuKα characteristic X-ray diffraction, 5 parts of polyvinyl butyral (product name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.), and 130 parts of cyclohexanone were mixed, to which 500 parts of glass beads with a diameter of 1 mm were added, and the mixture was dispersed for 2 hours at 1800 rpm while cooling with cooling water at 18°C. After the dispersion process, the mixture was diluted with 300 parts of ethyl acetate and 160 parts of cyclohexanone to prepare a coating liquid for the charge generating layer. This coating liquid for the charge generating layer was applied by dip coating on the undercoat layer, and the resulting coating film was dried at 110°C for 10 minutes to form a charge generating layer with a film thickness of 0.16 μm. The average particle size (median) of the hydroxygallium phthalocyanine crystals in the prepared charge generating layer coating solution was measured using a centrifugal particle size measuring device (product name: CAPA700, manufactured by Horiba, Ltd.) based on the liquid phase sedimentation method, and was found to be 0.18 μm.

Next, 2 parts of the charge transport compound represented by structural formula (C), 7 parts of the charge transport compound represented by structural formula (D), 1 part of the charge transport compound represented by structural formula (E), 10 parts of polycarbonate (product name: Iupilon Z400, manufactured by Mitsubishi Gas Chemical Co., Ltd.), and 0.002 parts of polycarbonate having a structural unit represented by structural formula (F) (viscosity average molecular weight Mv: 20,000) were dissolved in a mixed solvent of 70 parts of monochlorobenzene and 30 parts of dimethoxymethane to prepare a coating liquid for the charge transport layer. This coating liquid for the charge transport layer was applied by dip coating onto the charge generating layer, and the resulting coating film was dried at 100°C for 30 minutes to form a charge transport layer having a thickness of 18 μm.

Next, 70 parts of the compound represented by structural formula (G) and 30 parts of 1-propanol were mixed and left overnight, and the mixture was filtered through a PTFE membrane filter with a pore size of 0.2 μm to obtain preparation A.

Next, 20 parts of polytetrafluoroethylene particles (average primary particle size, number average molecular weight, crystallinity, and circularity are shown in Table 1) that had been heat-treated at 150°C for 3 hours, 1.4 parts of fluoroacrylic graft resin (non-volatile component of GF400 manufactured by Toagosei Co., Ltd.), 30 parts of 1-propanol, and 30 parts of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether (product name: AE-3000 manufactured by AGC Co., Ltd.) were stirred at a liquid temperature of 20°C, and then dispersed using a high-pressure homogenizer to obtain preparation B.

The obtained mixture A and mixture B were mixed and stirred to obtain a coating solution for the surface layer.

This surface layer coating liquid was dip-coated onto the charge transport layer, and the resulting coating was heat-treated at 50°C for 5 minutes. The coating was then irradiated with an electron beam for 1.6 seconds under a nitrogen atmosphere at an acceleration voltage of 70 kV and an absorbed dose of 50 kGy. The coating was then heat-treated for 25 seconds under a nitrogen atmosphere at a temperature of 130°C. The oxygen concentration from the electron beam irradiation to the 25-second heat treatment was 20 ppm. Next, the coating was heat-treated in the atmosphere for 12 minutes at a temperature of 115°C to form a surface layer with a thickness of 5 μm.

In this manner, an electrophotographic photoreceptor 14 was produced having a support, a conductive layer, an undercoat layer, a charge generating layer, a charge transport layer and a surface layer.

<Production Examples of Electrophotographic Photoreceptors 15 to 17>
In the same manner as in the production example of the electrophotographic photoreceptor 14, the polytetrafluoroethylene particles were changed to those shown in Table 1 to prepare electrophotographic photoreceptors 15 to 17.

<Production Example of Toner 1>
Polyester resin 1: 100 parts [composition (mol%) [polyoxypropylene (2.2)-2,2-bis (4-hydroxyphenyl) propane: polyoxyethylene (2.2)-2,2-bis (4-hydroxyphenyl) propane: terephthalic acid: dodecyl succinic acid: trimellitic acid = 80: 20: 75: 10: 15], Mw = 152,000, Mw / Mn = 32, molecular weight of 100 to 5000 = 25 mass%, acid value = 12 mg KOH / g]
C.I. Pigment Blue 15:3 7 parts 3,5-di-t-butyl salicylic acid aluminum compound (Bontron E88, manufactured by Orient Chemical Industry Co., Ltd.) 0.3 parts Fischer-Tropsch wax (melting point 78°C) 5 parts The above materials were mixed using a Henschel mixer (FM-75, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 20 s ^- 1 and a rotation time of 5 min, and then kneaded using a twin-screw kneader (PCM-30, manufactured by Ikegai Co., Ltd.) set at a temperature of 130°C. The kneaded product obtained was cooled to 25°C and coarsely crushed to 1 mm or less using a hammer mill to obtain a coarsely crushed product. The obtained coarsely crushed product was finely crushed using a mechanical crusher (T-250, manufactured by Turbo Kogyo Co., Ltd.). Furthermore, classification was performed using Faculty F-300 (manufactured by Hosokawa Micron Corporation) to obtain toner particles 1.

Strontium titanate particles A (1.0 part) and hydrophobic silica fine particles B (1.0 part) having a number average particle size of 120 nm and surface-treated with 20.0% by mass of hexamethyldisilazane were added to the obtained toner particles 1 (100.0 parts). The obtained additives were mixed in a Henschel mixer (FM75J type, manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) at a rotation speed of 30 s ^-1 for a rotation time of 5 min, and passed through an ultrasonic vibration sieve with an opening of 54 μm to obtain toner 1.

The weight average particle size (D4) of toner 1 was 6.2 μm, and the average circularity was 0.970. The adhesion rate of strontium titanate particles A of toner 1, the amount of separation of strontium titanate particles A YA, and YA/YB are shown in Table 2.

<Production Examples of Toners 2 to 14>
Toners 2 to 14 were obtained by carrying out the same operations as in Production Example 1 of Toner 1, except that the amount of strontium titanate particles A added and the production conditions were changed according to Table 2.

<Production Example of Magnetic Core Particle 1>
Step 1 (weighing and mixing step):
The ferrite raw materials were weighed so as to obtain the above _composition ratio, and _then crushed _and mixed for 5 hours in _a dry vibration mill using stainless steel beads with a diameter of 1/8 _inch .

Step 2 (pre-firing step):
The obtained pulverized material was made into pellets of about 1 mm square using a roller compactor. The pellets were passed through a vibrating sieve with 3 mm openings to remove coarse powder, and then through a vibrating sieve with 0.5 mm openings to remove fine powder. The pellets were then fired in a burner-type firing furnace at 1000° C. for 4 hours in a nitrogen atmosphere (oxygen concentration 0.01% by volume) to produce calcined ferrite. The composition of the resulting calcined ferrite was as follows:
(MnO) _a (MgO) _b ( _SrO ) _c ( _Fe2O3 ) _d
In the above formula, a = 0.257, b = 0.117, c = 0.007, d = 0.393

Step 3 (grinding step):
The obtained calcined ferrite was crushed to about 0.3 mm with a crusher, and then 30 parts of water was added to 100 parts of the calcined ferrite and the mixture was crushed in a wet ball mill using zirconia beads with a diameter of 1/8 inch for 1 hour. The obtained slurry was crushed in a wet ball mill using alumina beads with a diameter of 1/16 inch for 4 hours to obtain a ferrite slurry (finely crushed calcined ferrite).

Step 4 (granulation step):
To the ferrite slurry, 1.0 part of ammonium polycarboxylate as a dispersant and 2.0 parts of polyvinyl alcohol as a binder were added per 100 parts of the calcined ferrite, and the mixture was granulated into spherical particles using a spray dryer (manufacturer: Okawara Kakoki Co., Ltd.). After adjusting the particle size of the resulting particles, the mixture was heated at 650°C for 2 hours using a rotary kiln to remove the organic components of the dispersant and binder.

Step 5 (firing step):
In order to control the firing atmosphere, the material was heated from room temperature to 1300° C. in a nitrogen atmosphere (oxygen concentration 1.00% by volume) in an electric furnace over a period of 2 hours, and then fired at a temperature of 1150° C. for 4 hours. The temperature was then lowered to 60° C. over a period of 4 hours, and the material was returned from the nitrogen atmosphere to the air and taken out at a temperature of 40° C. or less.

Step 6 (sorting step):
After crushing the agglomerated particles, low magnetic particles were removed by magnetic separation, and coarse particles were removed by sieving through a sieve with 250 μm openings to obtain magnetic core particles 1 having a volume distribution-based 50% particle size (D50) of 37.0 μm.

<Preparation of Coating Resin 1>
Cyclohexyl methacrylate monomer 26.8% by mass
Methyl methacrylate monomer 0.2% by weight
Methyl methacrylate macromonomer 8.4% by mass
(Macromonomer having a weight average molecular weight of 5000 and a methacryloyl group at one end)
Toluene 31.3% by mass
Methyl ethyl ketone 31.3% by mass
Azobisisobutyronitrile 2.0% by mass
Among the above materials, cyclohexyl methacrylate monomer, methyl methacrylate monomer, methyl methacrylate macromonomer, toluene, and methyl ethyl ketone were placed in a four-necked separable flask equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a stirrer, and nitrogen gas was introduced to replace the inside of the system with nitrogen gas. After that, the mixture was heated to 80°C, azobisisobutyronitrile was added, and the mixture was refluxed for 5 hours to polymerize. Hexane was poured into the resulting reaction product to precipitate a copolymer, and the precipitate was filtered and then dried in vacuum to obtain coating resin 1.

Next, 30 parts of coating resin 1 were dissolved in 40 parts of toluene and 30 parts of methyl ethyl ketone to obtain polymer solution 1 (solid content 30% by mass).

<Preparation of Coating Resin Solution 1>
Polymer solution 1 (resin solids concentration 30%) 33.3% by mass
Toluene 66.4% by mass
Carbon black (Regal 330; manufactured by Cabot Corporation) 0.3% by mass
(Primary particle size: 25 nm, nitrogen adsorption specific surface area: 94 m ² /g, DBP oil absorption: 75 mL/100 g)
The mixture was dispersed for 1 hour using a paint shaker with zirconia beads having a diameter of 0.5 mm. The resulting dispersion was filtered through a 5.0 μm membrane filter to obtain a coating resin solution 1.

<Production Example of Magnetic Carrier 1>
(Resin coating process):
Magnetic core particles 1 and coating resin solution 1 were put into a vacuum degassing kneader maintained at room temperature (the amount of coating resin solution 1 put in was 2.5 parts as resin component for 100 parts of magnetic core particles 1). After putting in, it was stirred at a rotation speed of 30 rpm for 15 minutes, and after the solvent was evaporated to a certain degree (80 mass%) or more, it was heated to 80 ° C. while mixing under reduced pressure, and toluene was distilled off over 2 hours and cooled. The obtained magnetic carrier was separated into low magnetic products by magnetic separation, passed through a sieve with an opening of 70 μm, and then classified with a wind classifier to obtain magnetic carrier 1 with a 50% particle size (D50) of 38.2 μm based on volume distribution.

<Production Example of Two-Component Developer 1>
To 92.0 parts of the magnetic carrier 1, 8.0 parts of the toner 1 were added and mixed in a V-type mixer (V-20, manufactured by Seishin Enterprise Co., Ltd.) to obtain a two-component developer 1.

<Production Examples of Two-Component Developers 2 to 14>
In the production example of two-component developer 1, the same operation as for two-component developer 1 was carried out except that the toner was changed as shown in Table 3, to obtain two-component developers 2 to 14.

Example 1
The electrophotographic photoreceptor 1 was attached to the cyan station of a modified copy machine iR-ADV-C5255 manufactured by Canon, which was an evaluation device, and the two-component developer 1 in Table 3 was set in the developing device, and the following tests and evaluations were carried out.

In a 30°C/80% RH environment, the conditions of the charging device and the exposure device were set so that the dark potential (Vd) of the electrophotographic photoreceptor was -500v and the light potential (Vl) was -180v, and the initial potential of the electrophotographic photoreceptor was adjusted. Next, a cleaning blade made of polyurethane rubber with a hardness of 77° was set so that the contact angle with the peripheral surface of the electrophotographic photoreceptor was 28° and the contact pressure was 30g/cm (29.4N/m), and the following evaluations were performed.

[Rating 1: Ghost Rating]
2000 sheets were printed in a low temperature and low humidity environment (temperature 15°C/relative humidity 10% RH; L/L). The image was printed in an intermittent mode with a horizontal line with a printing rate of 1%. A plurality of 10mm x 10mm solid images were formed on the front half of the transfer paper, and a 2-dot, 3-space halftone image was formed on the rear half. The extent to which the solid images left traces on the halftone images was judged visually. The criteria for judging the ghost of the solid black image at the beginning of the durability test and after durability test of 2000 sheets are as follows:

(Evaluation criteria)
A: No ghosting occurs B: Very slight ghosting occurs C: Slight ghosting occurs D: Significant ghosting occurs

[Evaluation 2: Toner slip-through (HH streaks)]
With the heater (drum heater) for the electrophotographic photoreceptor turned on, 200 sheets of evaluation charts with 1% printed images in landscape A4 size were output continuously in a 30°C/80% RH (H/H) environment. Then, a screen image with a density of 30% was output as a halftone image, and the H/H initial streaks on the image were evaluated according to the following evaluation criteria. Then, durability was performed up to 100,000 sheets, and the same evaluation was performed.

(Evaluation criteria)
A: No streaks are observed on the image (excellent)
B: Images are obtained that appear to have streaks, but they are at a level where it is not possible to determine whether they are clear streaks or not. (Slightly better)
C: Very slight streaks are observed on the image (acceptable level in the present invention).
D: Clear streaks are observed on the image (unacceptable level in the present invention)

[Examples 2 to 21, Comparative Examples 1 to 9]
The combinations of two-component developers 2 to 14 and electrophotographic photoreceptors 1 to 17 shown in Table 3 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3.

1 electrophotographic photoreceptor, 2 shaft, 3 charging means, 4 exposure light, 5 developing means, 6 transfer means, 7 transfer material, 8 fixing means, 9 cleaning means, 10 pre-exposure light, 11 process cartridge, 12 guide means

Claims (6)

a charging step of charging the surface of the photoconductor;
an electrostatic latent image forming step of forming an electrostatic latent image on the charged surface of the photoreceptor;
a developing step of developing the electrostatic latent image with a toner to form a toner image;
a transfer step of transferring the toner image onto a transfer material;
a cleaning step of removing residual toner remaining on the surface of the photoreceptor after the transfer step using a cleaning blade;
a fixing step of fixing the toner image transferred onto the transfer material;
An image forming method comprising the steps of:
The photoreceptor has a support and a photosensitive layer on the support,
The layer constituting the outermost surface of the photoreceptor contains polytetrafluoroethylene particles,
The polytetrafluoroethylene particles are
(i) the number average particle size of the primary particles is 200 nm or more and 500 nm or less;
(ii) the number average molecular weight is 20,000 or more and 28,000 or less;
(iii) the crystallinity is 78.0% or more and less than 83.0%;
The toner has toner particles containing a binder resin and an external additive,
In a powder fluidity analysis of the toner, a propeller-type blade is rotated at a peripheral speed of the outermost edge of the propeller-type blade at 100 mm/sec and penetrated vertically into a toner powder layer in a measurement container, and measurement is started from a position 100 mm from the bottom of the powder layer. The total sum Et of the rotational torque and the vertical load obtained when the blade penetrates to a position 10 mm from the bottom is 100 mJ or more and 2000 mJ or less.
1. An image forming method comprising: The image forming method according to claim 1, wherein the crystallinity of the polytetrafluoroethylene particles is 80.0% or more and less than 83.0%. The image forming method according to claim 1 or 2, wherein the total Et is 200 mJ or more and 1000 mJ or less. The image forming method according to any one of claims 1 to 3, wherein the average circularity of the polytetrafluoroethylene particles in an SEM image is 0.80 or more. The image forming method according to any one of claims 1 to 4, wherein the average circularity of the toner particles is 0.960 or more and 0.980 or less. A toner containing strontium titanate particles A and silica particles B as the external additive,
The strontium titanate particles A have a rectangular parallelepiped particle shape,
the content of the strontium titanate particles A is 0.3 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the toner particles,
The number average particle diameter of the primary particles of the silica particles B is 80 nm or more and 200 nm or less,
the adhesion rate of the strontium titanate particles A to the toner particles is 25% or more and 70% or less;
When the sucrose solution in which the toner is dispersed is centrifuged, the amount of the strontium titanate particles A separated per 1 g of toner is defined as YA (mg) and the amount of the silica particles B separated per 1 g of toner is defined as YB (mg),
YA is 3.00 or more and 18.0 or less,
The image forming method according to any one of claims 1 to 5, wherein YA and YB satisfy the relationship of the following formula (1):
Y/Y>0.75 (1)

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