Process cartridge and electrophotographic device

Abstract

To provide a process cartridge that can prevent a solid density from becoming thin during repeated use under a high-temperature / high-humidity environment, and can prevent an HT density from becoming thin under a low-temperature / low-humidity environment during the repeated use.SOLUTION: A process cartridge detachably attached to an electrophotographic device main body has: an electrophotographic photoreceptor; a developing roller that develops an electrostatic latent image formed on the electrophotographic photoreceptor; and a toner supply roller that is arranged in contact with the developing roller and supplies toner to the developing roller, in which the developing roller and the toner supply roller are configured to rotate under a specific condition. The electrophotographic photoreceptor has a surface layer that serves as a polymer film containing at least one (meth) acrylic compound, and the surface layer contains a metal oxide particle.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a process cartridge having an electrophotographic photoreceptor and an electrophotographic apparatus.

Background Art

[0002] In recent years, electrophotographic apparatuses have been enhanced in terms of extended lifespan. However, in the electrophotographic process, extended lifespan tends to cause various adverse effects. Therefore, various measures have been taken to address the various adverse effects associated with extended lifespan. Among the above adverse effects, there is a problem that the amount of toner supplied from the developing roller mounted on the electrophotographic apparatus to the electrophotographic photoreceptor (hereinafter, also simply referred to as "photoreceptor") decreases due to repeated use, resulting in a decrease in the printed image density. On the other hand, when the amount of toner coated on the developing roller is insufficient (hereinafter, also referred to as "insufficient coating amount"), the supply of toner to the photoreceptor when printing a solid image becomes insufficient, and a phenomenon occurs where the density of the solid image becomes thin (hereinafter, also referred to as "solid density thinning"). On the other hand, when the triboelectric charge amount of the toner coated on the developing roller becomes excessive (hereinafter, also referred to as "charge-up"), the supply of toner to the photoreceptor when printing a halftone image becomes insufficient. As a result, a phenomenon occurs where the density of the halftone image becomes thin (hereinafter, also referred to as "HT density thinning").

[0003] To solve these adverse effects, improvements have been made in the configuration of the developing roller and the toner supply roller that supplies toner to the developing roller, as well as in the toner configuration. Patent Document 1 describes a configuration (hereinafter, referred to as "counter configuration") in which the rotation direction of the developing roller (developer carrier) and the rotation direction of the toner supply roller (toner recovery supply member) are opposite in the rubbing portion. Under the above counter configuration, by setting the recovery rate of the residual toner on the developing roller by the toner supply roller and the value of the charge amount per unit mass of the toner within an appropriate range, fogging and developing ghost are suppressed. Patent Document 2 discloses that the peripheral speed V of the developing rollerD The peripheral speed V of the toner supply roller with respect to RS the ratio V RS / V D (hereinafter also referred to as "R") is configured to be 0.8 or more and 1.5 or less. Under the counter configuration, on the one hand, by setting R to 0.8 or more, the coating amount on the developing roller is ensured to suppress the occurrence of developing ghost, and on the other hand, by setting R to 1.5 or less, the stress on the toner is reduced to suppress the deterioration of the toner when using small particle size toner. Patent Document 3 describes particles containing a metal oxide having a metal atom with a valence of 2 or more as an external additive for toner. By using the metal oxide as a charge control agent, the charge-up of the toner is suppressed, and the decrease in image density after 5,000 repeated image formations is suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] According to the study by the present inventors, in the technologies described in Patent Documents 1 to 3, solid density thinning may occur during repeated use in a high temperature and high humidity environment, and HT density thinning may occur during repeated use in a low temperature and low humidity environment. Therefore, an object of the present invention is to provide a process cartridge capable of suppressing solid density thinning during repeated use in a high temperature and high humidity environment and HT density thinning during repeated use in a low temperature and low humidity environment, respectively.

Means for Solving the Problems

[0006] The above object is achieved by the following invention. That is, a process cartridge according to an aspect of the present invention is a process cartridge detachable from an electrophotographic apparatus main body, the process cartridge including an electrophotographic photoreceptor, a developing roller that develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor, and a toner supply roller that is disposed in contact with the developing roller and supplies toner to the developing roller, wherein the surface movement direction of the developing roller and the surface movement direction of the toner supply roller during operation are opposite to each other at the contact position between the developing roller and the toner supply roller, and R represented by the following formula (E1) rotates while satisfying 1.2 ≦ R ≦ 1.5, R = V RS / V D (E1) (In formula (E1), V RS represents the absolute value of the peripheral speed [m / s] of the toner supply roller, and V D represents the absolute value of the peripheral speed [m / s] of the developing roller.) The electrophotographic photoreceptor has a surface layer that is a polymerized film of a composition containing at least one (meth)acrylic compound selected from the group consisting of (meth)acrylic monomers and (meth)acrylic oligomers, and the surface layer contains metal oxide particles.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a process cartridge capable of suppressing a decrease in solid density during repeated use in a high-temperature and high-humidity environment and a decrease in HT density during repeated use in a low-temperature and low-humidity environment, respectively.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described in detail with reference to preferred embodiments. The present invention is a process cartridge that is detachable from an electrophotographic apparatus main body, and the process cartridge includes an electrophotographic photoreceptor, a developing roller that develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor, and a toner supply roller that is disposed in contact with the developing roller and supplies toner to the developing roller. The developing roller and the toner supply roller are configured such that the moving direction of the surface of the developing roller and the moving direction of the surface of the toner supply roller during operation are opposite to each other at the contact position between the developing roller and the toner supply roller, and R represented by the following formula (E1) rotates while satisfying 1.2 ≦ R ≦ 1.5. R = V RS / V D (E1) (In formula (E1), V RS represents the absolute value of the peripheral speed [m / s] of the toner supply roller, and V D represents the absolute value of the peripheral speed [m / s] of the developing roller.) The electrophotographic photoreceptor has a surface layer that is a polymerized film of a composition containing at least one (meth)acrylic compound selected from the group consisting of (meth)acrylic monomers and (meth)acrylic oligomers, and the surface layer contains metal oxide particles. The present invention relates to a process cartridge. In this specification, the description of “(meth)acrylic” means “acrylic or methacrylic”. That is, the (meth)acrylic monomer refers to an acrylic monomer or a methacrylic monomer, the (meth)acrylic oligomer refers to an acrylic oligomer or a methacrylic oligomer, and the (meth)acrylic compound refers to an acrylic compound or a methacrylic compound.

[0010] In recent years, there has been a demand for further extending the service life of electrophotographic apparatuses, and the number of repeated uses has been increasing more and more. In response to this, when the inventors studied, in the prior art, in the case of repeated use in a high-temperature and high-humidity environment, the solid density was thin due to a significant lack of coating amount, and in the case of repeated use in a low-temperature and low-humidity environment, the suppression of both the thin HT density due to significant charge-up was not sufficient. In particular, in a configuration in which a charge control agent is added as an external additive for toner, although the degree of charge-up is significantly different between the initial stage and after repeated use during repeated use in a low-temperature and low-humidity environment, the amount of the charge control agent does not change. Therefore, by adjusting the addition amount of the charge control agent, it is not possible to optimize both the initial triboelectric charge amount and the triboelectric charge amount after repeated use. Therefore, the inventors studied the combination of the configuration related to the combination of the developing roller and the toner supply roller and the combination of the material constituting the surface of the photoreceptor. As a result, it was found that the above problems can be solved by designing and combining the configuration of the developing roller and the toner supply roller and the photoreceptor surface material as follows.

[0011] <Configuration related to the combination of the developing roller and the toner supply roller> In the present invention, the developing roller and the toner supply roller rotate so as to satisfy 1.2 ≦ R ≦ 1.5, where R is represented by the following formula (E1). Further, the moving direction of the surface of the developing roller is configured to be opposite to the moving direction of the surface of the toner supply roller at the contact position with the toner supply roller. R = V RS / V D Formula (E1) (In formula (E1), V RS represents the absolute value of the peripheral speed [m / s] of the toner supply roller, and V D represents the absolute value of the peripheral speed [m / s] of the developing roller.)

[0012] On one hand, since the configuration is such that 1.2 ≦ R ≦ 1.5, a sufficient amount of toner can be stably supplied from the toner supply roller to the developing roller. As a result, the occurrence of insufficient coating amount on the developing roller can be suppressed, and the phenomenon of light solid density during repeated use in a high-temperature and high-humidity environment can be sufficiently suppressed. On the other hand, since the toner supply roller has a counter configuration with respect to the developing roller, the toner remaining on the developing roller after development from the developing roller to the photoreceptor is strongly scraped off by the toner supply roller. As a result, it is possible to suppress the toner remaining on the developing roller each time the developing process is performed and the triboelectric charge amount of the toner from increasing every time the developing roller rotates.

[0013] <Material constituting the surface of the photoreceptor> The photoreceptor used in the present invention has a surface layer that is a polymerized film of a composition containing at least one (meth)acrylic compound selected from the group consisting of (meth)acrylic monomers and (meth)acrylic oligomers. Further, the surface layer contains metal oxide particles. Hereinafter, the effects of the electrophotographic photoreceptor used in the present invention having a surface layer that is a polymerized film of a composition containing at least one (meth)acrylic compound selected from the group consisting of (meth)acrylic monomers and (meth)acrylic oligomers will be described. Also, the effects of the surface layer containing metal oxide particles will be described.

[0014] As described in <Configuration related to the combination of the developing roller and the toner supply roller>, by devising the configuration related to the combination of the developing roller and the toner supply roller, it is possible to suppress the occurrence of solid density thinning during repeated use in a high-temperature and high-humidity environment. Further, it is possible to suppress an increase in the triboelectric charge amount of the toner each time the developing roller rotates due to the continuous remaining of the toner. However, when the developing roller and the toner supply roller are configured as a counter structure and R is set to a value greater than 1, the rubbing at the contact portion between the developing roller and the toner supply roller becomes stronger. Therefore, toner charge-up is likely to occur during repeated use in a low-temperature and low-humidity environment, which has been the cause of the HT density thinning. On the other hand, in the present invention, an electrophotographic photoreceptor having a surface layer that is a polymer film of a specific composition and the surface layer contains metal oxide particles is used. Here, the specific composition is a composition containing at least one (meth)acrylic compound selected from the group consisting of (meth)acrylic monomers and (meth)acrylic oligomers. Thereby, the occurrence of HT density thinning during repeated use in a low-temperature and low-humidity environment is suppressed.

[0015] The inventors of the present invention speculate as follows on the mechanism by which the use of the electrophotographic photoreceptor having the characteristics described above suppresses the HT density thinning during repeated use in a low-temperature and low-humidity environment. In order to suppress the charge-up of the toner, it is common to use a charge control agent as an external additive for the toner. However, as already described, the amount of the charge control agent does not change despite the fact that the degree of charge-up significantly differs between the initial stage and after repeated use during repeated use in a low-temperature and low-humidity environment. Therefore, it is not possible to optimize both the initial triboelectric charge amount and the triboelectric charge amount after repeated use. The selection of the type and amount of the charge control agent needs to be determined in consideration of not making the initial triboelectric charge amount too small, and there were cases where a sufficient effect for suppressing charge-up after repeated use in a low-temperature and low-humidity environment could not be obtained. In addition, the charge control agent exhibits the effect of suppressing the low HT density by reducing the triboelectric charge amount on the developing roller. However, even when present on the toner supply roller, it has the effect of reducing the triboelectric charge amount. Therefore, the amount of toner supplied from the toner supply roller to the developing roller may decrease, which may accelerate the solid density reduction due to the above-mentioned insufficient coating amount.

[0016] Therefore, in the present invention, by using the metal oxide contained in the surface layer of the photoreceptor as a charge control agent, unlike the conventional case, the charge control agent is configured to be released from the surface layer of the photoreceptor as the surface of the photoreceptor is worn away. As a result, it is possible to realize a state where the amount of the charge control agent is small initially and the amount of the charge control agent on the developing roller increases as the number of repeated uses in a low-temperature and low-humidity environment increases. Therefore, it is possible to optimally control the triboelectric charge amount of the toner from the initial stage to after repeated use. In addition, the metal oxide contained in the surface layer of the photoreceptor preferentially migrates to the developing roller disposed at a position close to the photoreceptor as the surface layer is worn away. Therefore, it is also possible to avoid the adverse effects of a decrease in the triboelectric charge amount due to the presence of the charge control agent on the toner supply roller disposed at a relatively distant position from the photoreceptor and the acceleration of the solid density reduction due to the insufficient coating amount caused thereby.

[0017] Furthermore, in the present invention, a polymerized film of a composition containing at least one (meth)acrylic compound selected from the group consisting of (meth)acrylic monomers and (meth)acrylic oligomers is used as the surface layer of the photoreceptor. Thereby, a photoreceptor that can withstand long-life repeated use is supplied, the amount of wear of the surface layer per rotation of the developing roller is optimized, and the supply amount of the metal oxide acting as the charge control agent to the developing roller is prevented from becoming excessive.

[0018] The toner coating amount on the developing roller and the triboelectric charging amount of the toner are related to each other at the toner supply roller, the developing roller, and the contact portion between the two. Therefore, even if the triboelectric charging amount of the toner itself is simply increased as described above to increase the coating amount and suppress the solid density thinning, when the triboelectric charging amount is excessive, the toner development amount from the developing roller to the drum when forming an HT image decreases. And thereby, HT density thinning occurs (Reference: Masahiro Hosoya, Mitsunaga Saito, Contact-type one-component non-magnetic development method (I) - Theory and optimization -, Journal of the Institute of Image Electronics Engineers of Japan, Vol. 31, No. 4, 1992). The present invention can optimize the two relationships of the toner coating amount and the triboelectric charging amount of the toner on the developing roller from the initial stage to after repeated use by combining the <configuration related to the combination of the developing roller and the toner supply roller> and the <material constituting the surface of the photoreceptor>. And thereby, both the solid density thinning in repeated use in a high-temperature and high-humidity environment and the HT density thinning in repeated use in a low-temperature and low-humidity environment are suppressed.

[0019] As shown by the above mechanism, in the process cartridge according to the present invention, the configuration related to the combination of the developing roller and the toner supply roller and the material constituting the surface of the photoreceptor synergistically exert effects on each other. And thereby, it becomes possible to obtain the effects of the present invention.

[0020] Hereinafter, the configuration of the photoreceptor used in the present invention will be described in detail. [Electrophotographic photoreceptor] The photoreceptor used in the present invention is characterized by having a surface layer. As a method for manufacturing the photoreceptor used in the present invention, a method of preparing coating liquids for each layer described later, coating them in a desired layer order, and drying them can be mentioned. At this time, as the coating method of the coating liquid, dipping coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, ring coating, etc. can be mentioned. Among these, dipping coating is preferable from the viewpoints of efficiency and productivity. Hereinafter, the support and each layer will be described.

[0021] <Support> In the present invention, the photoreceptor has a support. In the present invention, the support is preferably a conductive support having conductivity. Further, examples of the shape of the support include a cylindrical shape, a belt shape, and a sheet shape. Among these, a cylindrical support is preferable. Further, an electrochemical treatment such as anodization, a blasting treatment, a cutting treatment, or the like may be performed on the surface of the support. As the material of the support, metal, resin, glass, or the like is preferable. Examples of the metal include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among these, an aluminum support using aluminum is preferable. Further, conductivity may be imparted to the resin or glass by a treatment such as mixing or coating with a conductive material.

[0022] <Conductive layer> In the photoreceptor used in the present invention, a conductive layer may be provided on the support. By providing the conductive layer, it is possible to conceal scratches and unevenness on the support surface and to control light reflection on the support surface. The conductive layer preferably contains conductive particles and a resin. Examples of the material of the conductive particles include metal oxides, metals, carbon black, and the like. Examples of the metal oxide include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, and the like. Examples of the metal include aluminum, nickel, iron, nichrome, copper, zinc, silver, and the like. Among these, it is preferable to use a metal oxide as the conductive particles, and more preferably, titanium oxide, tin oxide, or zinc oxide. When a metal oxide is used as the conductive particles, the surface of the metal oxide may be treated with a silane coupling agent or the like, or the metal oxide may be doped with an element such as phosphorus or aluminum or an oxide thereof. Examples of the element or oxide to be doped include phosphorus, aluminum, niobium, tantalum, and the like. Further, the conductive particles may have a laminated structure having core material particles and a coating layer covering the particles. Examples of the core material particles include titanium oxide, barium sulfate, and zinc oxide. Examples of the coating layer include metal oxides such as tin oxide and titanium oxide. When a metal oxide is used as the conductive particle, the volume average particle diameter thereof 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 the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, and alkyd resin. Further, the conductive layer may further contain a concealer such as silicone oil, resin particles, and titanium oxide. The film 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-described respective materials and a solvent, forming this coating film, and drying it. Examples of the solvent 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 the dispersion method for dispersing the conductive particles in the coating solution for the conductive layer include a method using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

[0023] <Undercoat layer> In the photoreceptor used in the present invention, an undercoat layer may be provided on the support or the conductive layer. By providing the undercoat layer, the interlayer adhesion function can be enhanced and a charge injection blocking function can be imparted. The undercoat layer preferably contains a resin. Further, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl phenol 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 group of the monomer having a polymerizable functional group include isocyanate group, blocked isocyanate group, methylol group, alkylated methylol group, epoxy group, metal alkoxide group, hydroxyl group, amino group, carboxyl group, thiol group, carboxylic anhydride group, and carbon-carbon double bond group.

[0024] Further, the undercoat layer may further contain an electron transport material, a metal oxide, a metal, a conductive polymer, etc. for the purpose of enhancing electrical properties. Among these, it is preferable to use an electron transport material and a metal oxide. Examples of the electron transport material include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, halogenated aryl compounds, silole compounds, boron-containing compounds, etc. As the electron transport material, an electron transport material having a polymerizable functional group may be used and copolymerized with the monomer having the above-described polymerizable functional group to form an undercoat layer as a cured film. Examples of the metal oxide include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, silicon dioxide, etc. Examples of the metal include gold, silver, aluminum, etc. Further, the undercoat layer may further contain an additive. The film 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 an undercoat layer coating solution containing each of the above materials and a solvent, forming this coating film, and drying and / or curing it. Examples of the solvent used in the coating solution include alcohol solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents, and the like.

[0025] <Photosensitive layer> The photosensitive layer of the photoreceptor according to the present invention is mainly classified into (1) a laminated photosensitive layer and (2) a single-layer photosensitive layer. (1) The laminated photosensitive layer has a charge generation layer containing a charge generating substance and a charge transport layer containing a charge transporting substance. (2) The single-layer photosensitive layer has a photosensitive layer containing both a charge generating substance and a charge transporting substance.

[0026] (1) Laminated photosensitive layer The laminated photosensitive layer has a charge generation layer and a charge transport layer.

[0027] (1-1) Charge generation layer The charge generation layer preferably contains a charge generating substance and a resin. Examples of the charge generating substance include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, phthalocyanine pigments, and the like. Among these, azo pigments and phthalocyanine pigments are preferred. Among the phthalocyanine pigments, oxytitanium phthalocyanine pigment, chlorogallium phthalocyanine pigment, and hydroxygallium phthalocyanine pigment are preferred. The content of the charge generating substance in the charge generation layer is preferably 40% by mass or more and 85% by mass or less, more preferably 60% by mass or more and 80% by mass or less, based on the total mass of the charge generation layer. Examples of the resin include polyester resins, polycarbonate resins, polyvinyl acetal resins, polyvinyl butyral resins, acrylic resins, silicone resins, epoxy resins, melamine resins, polyurethane resins, phenol resins, polyvinyl alcohol resins, cellulose resins, polystyrene resins, polyvinyl acetate resins, polyvinyl chloride resins, and the like. Among these, polyvinyl butyral resin is more preferred. Further, the charge generation layer may further contain additives such as an antioxidant and an ultraviolet absorber. Specifically, examples thereof include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, and the like. The film thickness of the charge generation 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 solution for the charge generation layer containing each of the above materials and a solvent, forming this coating film, and drying it. Examples of the solvent used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, and the like.

[0028] (1-2) Charge transport layer The charge transport layer preferably contains a charge transport material and a resin. Examples of the charge transport material 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 preferable. Examples of preferable charge transport materials are shown below with the structures of CTM1 to CTM10.

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0029] The content of the charge transport material in the charge transport layer is preferably 25% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 55% by mass or less, based on the total mass of the charge transport layer. Examples of the resin include polyester resin, polycarbonate resin, acrylic resin, polystyrene resin, etc. Among these, polycarbonate resin, polyester resin, and acrylic resin are preferred. As the polyester resin, polyarylate resin is particularly preferred. The content ratio (mass ratio) of the charge transport material to the resin is preferably 4:10 to 20:10, more preferably 5:10 to 12:10.

[0030] In addition, the charge transport layer may contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, lubricity imparting agents, and wear resistance improvers. Specifically, 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, boron nitride particles, etc. can be mentioned. The film thickness of the charge transport layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less. The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing each of the above materials and a solvent, forming this coating film, and drying it. Examples of the solvent used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents or aromatic hydrocarbon-based solvents are preferred.

[0031] (2) Single-layer photosensitive layer The single-layer photosensitive layer can be formed by preparing a coating solution for the photosensitive layer containing a charge generating substance, a charge transporting substance, a resin, and a solvent, forming this coating film, and drying it. Examples of the charge generating substance, the charge transporting substance, and the resin are the same as those exemplified in the above “(1) Laminated photosensitive layer”.

[0032] <Protective layer> In the photoreceptor according to the present invention, a protective layer may be provided on the photosensitive layer. By providing the protective layer, the durability can be improved. The protective layer may be, for example, a high-strength layer containing a resin for the purpose of imparting durability corresponding to a long life, and it is not necessarily necessary to include conductive particles or a charge transporting substance to enhance the charge transporting performance. However, from the viewpoint of enhancing the basic electrical characteristics of the photoreceptor, it is preferable to contain conductive particles and / or a charge transporting substance and a resin to achieve both durability and basic electrical characteristics. Examples of the conductive particles include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide. Examples of the charge transporting substance 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.

[0033] Examples of the resin include polyester resin, acrylic resin, phenoxy resin, polycarbonate resin, polystyrene resin, phenol resin, melamine resin, epoxy resin, etc. Among them, polycarbonate resin, polyester resin, and acrylic resin are preferred. Further, the protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the reaction in this case include thermal polymerization reaction, photopolymerization reaction, radiation polymerization reaction, etc. Examples of the polymerizable functional group of the monomer having a polymerizable functional group include acryloyl group, methacryloyl group, etc. As the monomer having a polymerizable functional group, a material having a charge transport ability may be used.

[0034] The protective layer may contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slipperiness imparting agents, wear resistance improving agents, etc. Specifically, examples of the additives 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, boron nitride particles, etc. The film thickness of the protective 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 protective layer can be formed by preparing a coating solution for the protective layer containing the above-mentioned various materials and a solvent, forming this coating film, and drying and / or curing it. Examples of the solvent used in the coating solution include alcohol solvents, ketone solvents, ether solvents, sulfoxide solvents, ester solvents, aromatic hydrocarbon solvents.

[0035] <Surface layer> In the photoreceptor used in the present invention, the surface layer is a polymerized film of a composition containing at least one (meth)acrylic compound selected from the group consisting of (meth)acrylic monomers and (meth)acrylic oligomers, and contains metal oxide particles. The surface layer mentioned here is the part where the photoreceptor contacts the toner and various members during the electrophotographic process. The protective layer, charge transport layer, and single-layer photoreceptive layer can serve as the surface layer. However, from the perspective of achieving both durability in long-term repeated use and basic electrical properties in the electrophotographic process, the surface layer is preferably the protective layer. The above metal oxide particles preferably have a low volume resistivity and are likely to exhibit an effect as a charge control agent for the toner. From this perspective, the above metal oxide particles preferably contain at least one kind of metal oxide particles selected from the group consisting of indium tin oxide particles, tin oxide particles, titanium oxide particles, zinc oxide particles, and aluminum oxide particles.

[0036] Let the n types (n is an integer of 1 or more) of the above metal oxide particles be metal oxide particles A i (i is an integer from 1 to n). Also, let the volume resistivity of the metal oxide particles A i be ρ i [Ω·cm]. Also, let the volume content ratio of the metal oxide particles A i in the above surface layer with respect to the entire surface layer be R i [%]. In this case, for the process cartridge according to the present invention, it is preferable that the sum from i = 1 to i = n of (R i / ρ i ) satisfies the following formula (E2).

Equation

[0037] Furthermore, it is more preferable that the process cartridge according to the present invention satisfies the following formula (E3). [Number] (R i / ρ i ) from i = 1 to i = n has a sum greater than 10 -2 By being larger, charge-up can be more effectively suppressed. Therefore, it becomes possible to further enhance the balance of charge control performance for optimizing the toner coat amount and toner triboelectric charge amount on the toner supply roller and the developing roller from the initial stage to after repeated use.

[0038] From the viewpoint of the balance of the above charging performance, the metal oxide particles preferably contain metal oxide particles having a volume resistivity of 10 3 [Ω·cm] or less, and specifically preferably contain indium tin oxide particles.

[0039] The above (meth)acrylic compound preferably provides durability in long-life repeated use and can appropriately control the release amount of the above metal oxide particles per rotation of the developing roller. From this viewpoint, the above (meth)acrylic compound preferably contains at least one trifunctional or higher (meth)acrylic compound selected from the group consisting of trifunctional or higher (meth)acrylic monomers and trifunctional or higher (meth)acrylic oligomers. Further, it is more preferable that the above (meth)acrylic compound contains at least one hexafunctional (meth)acrylic compound selected from the group consisting of hexafunctional or higher (meth)acrylic monomers and hexafunctional or higher (meth)acrylic oligomers.

[0040] From the viewpoint of cost, the surface layer of the photoreceptor used in the present invention preferably does not contain an organic compound having a charge transport function. The surface layer of the photoreceptor used in the present invention contains metal oxide particles, which undertake a certain degree of charge transport function. However, even so, when the surface layer does not contain an organic compound having a charge transport function, the film thickness of the surface layer is preferably 0.5 μm or more and 10 μm or less. On the one hand, if the film thickness of the surface layer is thinner than 0.5 μm, there is a high possibility that there are parts not covered by the surface layer, and in some cases, the surface layer may not be able to function. On the other hand, if the film thickness of the surface layer is thicker than 10 μm, when the electrophotographic photoreceptor is charged during the electrophotographic process, since there is no organic compound having a charge transport function, the surface layer will hold a large share voltage. As a result, the residual potential may become extremely large and the basic electrical characteristics may deteriorate. When the surface layer has a charge transport substance, the film thickness of the surface layer is preferably 0.5 μm or more and 20 μm or less, and preferably 1 μm or more and 14 μm or less.

[0041] The surface layer can be formed by preparing a coating liquid for the surface layer containing the above (meth)acrylic compound, the above metal oxide particles, each material described in the above <photosensitive layer> and / or <protective layer>, and a solvent, forming this coating film, and drying and / or curing it. Examples of the solvent used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, sulfoxide solvents, ester solvents, and aromatic hydrocarbon solvents. The surface layer is formed as a cured film by subjecting the composition containing the above (meth)acrylic compound to a polymerization reaction. Examples of the reaction at that time include thermal polymerization reaction, photopolymerization reaction, radiation polymerization reaction, etc.

[0042] Examples of preferred (meth)acrylic monomers are shown below with the structures of ACM1 to ACM54.

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

[0043] <Method for Identifying (Meth)Acrylic Compounds> That the electrophotographic photoreceptor used in the present invention has a surface layer formed by polymerizing the composition containing the above (meth)acrylic compound can be identified as follows. Also, the structural formulas of a plurality of types of (meth)acrylic monomers and / or (meth)acrylic oligomers, and their content ratios can be identified as follows. (1) Immerse the electrophotographic photoreceptor in chloroform. Since the surface layer formed by polymerizing the (meth)acrylic compound is insoluble in chloroform, the surface layer is separated from the electrophotographic photoreceptor in chloroform, and a chloroform solution in which the lower layer below the surface layer is dissolved is obtained. (2) Analyze the above solution using chromatography, high-resolution mass spectrometry, nuclear magnetic resonance spectroscopy, pyrolysis gas chromatography, etc. Thereby, a plurality of types of unreacted (meth)acrylic monomers and / or (meth)acrylic oligomers contained in the lower layer below the surface layer are identified. (3) Prepare a certain amount of the identified plurality of types of (meth)acrylic monomers and / or (meth)acrylic oligomers by synthesis or purchase, etc., and polymerize them alone. (4) Analyze each of the polymerized plurality of types of polymers by infrared absorption spectroscopy, and determine a calibration peak as a peak used to obtain a calibration curve in the obtained infrared absorption spectrum. At that time, the calibration peak of each (meth)acrylic monomer is selected so that the peak intensity is maximized under the condition that the calibration peaks of polymers other than itself do not enter the range three times the half-width of the calibration peak. (5) For each of the polymers, determine a calibration range defined in a range three times the half-width centered on the calibration peak. (6) Measure the infrared absorption spectrum when at least two or more unreacted (meth)acrylic monomers and / or (meth)acrylic oligomers are mixed and polymerized at at least two or more mixing ratios. Then, compare the integrated values of the above calibration ranges, and obtain a calibration curve for each (meth)acrylic monomer and / or (meth)acrylic oligomer. (7) Analyze the surface layer of the photoreceptor to be identified by infrared absorption spectroscopy. Calculate the mixing ratio of each (meth)acrylic monomer and / or (meth)acrylic oligomer contained in the surface layer from the obtained infrared absorption spectrum -1 and the calibration curves of the respective (meth)acrylic monomers and / or (meth)acrylic oligomers. (8) Measure the infrared absorption spectrum -2 of the polymer obtained by mixing and polymerizing each (meth)acrylic monomer and / or (meth)acrylic oligomer at the above mixing ratio. (9) Compare the above infrared absorption spectrum -1 with the above infrared absorption spectrum -2. At this time, confirm that the integral value of the difference spectrum in the calibration range of each (meth)acrylic monomer and / or (meth)acrylic oligomer is 10% or less of the integral value in the calibration range of the above infrared absorption spectrum -2. Note that the procedures (1) and (2) in the above identification method can be replaced by component identification using other methods including literature research. Also, finally, in the procedure (9) above, it is only necessary to confirm that the surface layer to be identified is indeed polymerized from a plurality of types of (meth)acrylic monomers and / or (meth)acrylic oligomers that are identification candidates. As long as this is the case, the procedures (3) to (8) can also be replaced by other methods in addition to (1) and (2).

[0044] <Method for Identifying Metal Oxide Particles> It can be identified as follows that the surface layer of the electrophotographic photoreceptor used in the present invention contains metal oxide particles, the composition of the metal oxide particles, and the content ratio of the metal oxide particles with respect to the surface layer. (Identification of Composition) (1) Cut out a cross-section of the surface layer of the photoreceptor and observe it with a scanning electron microscope. (2) Analyze the particles present in the observation range by energy-dispersive X-ray analysis and identify their composition. (Identification of Content Ratio) (1) Immerse the photoreceptor in chloroform. Since the surface layer formed by polymerizing the (meth)acrylic compound is insoluble in chloroform, the surface layer is separated from the photoreceptor in chloroform. (2) After washing the separated surface layer, dry it and perform thermogravimetric analysis. (3) Identify the content ratio by comparing the weight at low temperature with the weight after all the organic substances have burned at high temperature.

[0045] <Method for Measuring Volume Resistivity of Metal Oxide Particles> The volume resistivity of the metal oxide particles can be evaluated by measuring the capacitance and conductivity of air and powder by impedance measurement using the parallel plate capacitor method. The apparatus uses a powder measurement jig composed of a 4-terminal sample holder SH2-Z (manufactured by Toyo Technica Co., Ltd.) and a torque wrench adapter SH-TRQ-AD (manufactured by Toyo Technica Co., Ltd., optional), and a material test system ModuLabXMMTS (manufactured by Solartron). In addition, a noise cut transformer NCT-I31.4kVA (manufactured by Denken Seiki Kenkyujo Co., Ltd.) for suppressing commercial power supply noise and a shield box for suppressing electromagnetic wave noise are used. For the powder measurement jig, a 4-terminal sample holder and an optional torque wrench adapter SH-TRQ-AD are used. As the parallel plate electrodes, an upper electrode (Φ25mm solid electrode) SH-H25AU and a lower electrode for liquid / powder (center electrode Φ10mm; guard electrode Φ26mm) SH-2610AU are used. In this way, a configuration is adopted such that a resistance of 0.1Ω to 1TΩ can be measured for an electrical signal of up to 500Vp-p, DC~AC 1MHz. Also, in order to adjust the pressure of the powder sample, the torque wrench adapter SH-TRQ-AD is attached to the micrometer used for measuring the film thickness between the upper and lower electrodes provided in the 4-terminal sample holder. As the torque driver used for pressure management, torque drivers RTD15CN, RTD30CN (manufactured by Tokyo Sokki Kenkyujo Co., Ltd.) and a 6.35mm square bit are used, and a configuration is adopted such that the tightening torque of the metal oxide particles can be controlled to 20.0 cN / m. For the measurement of electrical AC characteristics, impedance measurement is carried out using a Material Test System ModuLab XM MTS (manufactured by Solartron). ModuLab XM MTS is composed of a control module XM MAT 1 MHz, a high-voltage module XM HV 100, a femto-current module XM FA, and a frequency response analysis module XM RA 1 MHz. Also, the control software uses the company's XM-studio MTS Ver. 3.4. The measurement conditions for metal oxide particles are set to the Normal Mode for only measurement. Also, the AC level is set within the range of 7×10 -3 Vrms or more and 7 Vrms or less so as to be within the measurable current range of the measuring instrument. Also, the DC bias is set to 0 V, and the sweep frequency is set to 1 MHz to 0.01 Hz (12 points / decade or 6 points / decade). Also, in the case of a highly conductive powder material such as an additive, the AC level is set within the range of 7×10 -3 Vrms or more and 7 Vrms or less so as to be within the measurable current range of the measuring instrument. Furthermore, in view of noise suppression and shortening of the measurement time, the following settings are added for each sweep frequency. Sweep frequency 1 MHz to 10 Hz: Measurement integration time 64 cycles Sweep frequency 10 Hz to 1 Hz: Measurement integration time 24 cycles Sweep frequency 1 Hz to 0.01 Hz: Measurement integration time 1 cycle

[0046] Based on the above measurement conditions, the impedance characteristics, which are electrical AC characteristics, are measured. By performing the measurement under the above conditions, using a powder measurement jig based on the parallel plate capacitor method, the impedance characteristics of air and the sample at a measurement electrode S of Φ10 mm and a film thickness d corresponding to the applied torque can be obtained. From the obtained impedance characteristics of air and the sample, data correction processing of the measurement system is performed to obtain a highly reliable capacitance C and conductance (conductivity) G. From the obtained capacitance C, conductance (conductivity) G, and the geometric shape (electrode size S of the parallel plate and sample film thickness) of the powder measurement jig, the relative permittivity and conductivity, which are electrical properties, are determined. When using the four-terminal sample holder SH2-Z for the first time, since there are individual differences in the four-terminal sample holder SH2-Z used for the powder measurement jig, it is necessary to perform the following two verifications to find the optimal measurement conditions. The first verification is the film thickness dependence characteristic of the four-terminal sample holder. Measure the dependence on the air thickness (distance between the upper and lower electrodes), confirm the error between the theoretical value and the measured value of the capacitance, and grasp the film thickness at which the measurement error is minimized or the optimal value. The second verification is the measurement of mechanical error. When measuring the powder sample, a load with torque control is applied to keep the bulk density constant. In contrast, the measurement of air is in a no-load state. At this time, due to the influence of dimensions such as mechanical processing accuracy, a film thickness error occurs. Therefore, confirm the offset value between the load state and the no-load state of the tightening torque control value (in this jig, 6.5 cN·m), and use this as the offset correction value.

[0047] The specific procedures for sample preparation and measurement are as follows. (1) Place the powder sample on the central electrode part of the lower electrode and mold it into a trapezoidal shape with a height of 5 mm. (2) Attach the lower electrode with the powder sample to the four-terminal sample holder SH2-Z and lower the upper electrode. (3) At this time, lower the upper electrode to the upper end of the powder sample while keeping it constant so that it does not rotate inadvertently. (4) While rotating the upper electrode left and right, perform a smoothing process so that the powder sample becomes smooth. (5) Using a micrometer, adjust to a predetermined film thickness while keeping the rotation direction of the upper electrode in a uniform and constant direction. (6) Apply pressure using a torque driver with the tightening torque controlled at 20.0 cN·m. (7) Measure the film thickness of the powder sample using a micrometer. (8) Perform impedance measurement under the above conditions. (9) After the measurement is completed, raise the upper electrode and remove the lower electrode. At this time, remove the lower electrode with great care so that the powder sample does not enter the contact terminal for the lower electrode of the four-terminal sample holder, and protect it with masking tape. (10) Clean the upper and lower electrodes. (11) Remove the masking tape and attach the lower electrode. (12) Adjust so that the thickness t of the air, taking into account the offset correction in the no-load state, corresponds to the sample film thickness d obtained in step (7), and keep the rotation direction of the upper electrode in a uniform fixed direction. (13) Perform an impedance measurement of the air. (14) If the measured data of the air (dielectric tangent; tanδ) measured in step (13) is greater than 0.001 in the frequency range of 100 Hz to 0.021 Hz, it is due to insufficient cleaning, so redo the work from the cleaning step in step (10). Note that the measurement is carried out at 25°C.

[0048] The specific data processing procedure is as follows. (15) Calculate the error in the phase characteristic with respect to the theoretical value from the measured impedance characteristics of the air, and obtain the phase correction data of the material test system ModuLabXMMTS (manufactured by Solartron). (16) Apply the phase correction data calculated in step (15) to the impedance characteristics of the air measured in step (13) to obtain the impedance characteristics of the air subjected to the phase correction process. (17) Calculate the capacitance Ca from the admittance Ya = Ga + jωCa of the impedance characteristics of the phase-corrected air, calculate the error from the theoretical value, and obtain the correction data α for the film thickness error. (18) Apply the phase correction process obtained in step (15) to the impedance characteristics of the powder sample measured in step (8). For the complex admittance Ym = Gm + jωCm of the characteristics subjected to the phase correction process of step (19), reliable relative permittivity and conductivity of the powder sample can be obtained by calculating using the capacitance Ca of air obtained in step (17) and its correction data α.

[0049] Hereinafter, a method for quantifying the volume resistivity, which is an electrical property, will be described. (Method for quantifying the conductivity index κ / ω) Generally, since the conductivity κ of a dielectric (insulator) has a characteristic proportional to the angular frequency, it is useful to use the conductivity index κ / ω obtained by dividing the conductivity κ by the angular frequency ω as the conductivity parameter value. The conductivity index κ / ω shows the same frequency characteristics as the dielectric loss tangent tanδ, and when the dielectric relaxation of the electrode interface component and the powder bulk component is different, a characteristic having a maximum value can be obtained. The maximum value of the conductivity index κ / ω is considered to indicate the conductivity with respect to the powder bulk including the inside of the particles, the particle surface, and the (particle-particle) interface. Therefore, the maximum value is defined as the conductivity parameter of the powder bulk component.

[0050] (Method for quantifying conductivity and volume resistivity) A powder sample having both capacitance and conductivity can be recognized as an RC parallel circuit model, and the conductivity κ shows a constant value in the low frequency range. The reciprocal of the conductivity κ is defined as the volume resistivity.

[0051] Next, the configuration of the developing roller used in the present invention will be described in detail. [Developing roller] As the developing roller used in the present invention, in an electrophotographic process, any developing roller usually used for developing an electrostatic latent image formed on the surface of a photoreceptor can be used without any particular limitation. As the developing roller, one having a conductive substrate and an elastic layer can be used. Specifically, for example, the developing roller may be an elastic roller configured by providing a conductive elastic rubber layer having a predetermined volume resistivity as an elastic layer around a metal core.

[0052] <Conductive substrate> As the conductive substrate, a columnar or hollow cylindrical conductive core can be used. The conductive core may be composed of the following conductive materials. That is, examples of the conductive material include metals or alloys such as aluminum, copper alloy, and stainless steel; iron plated with chromium or nickel; and synthetic resins having conductivity. For the purpose of improving the adhesion to an elastic layer or the like provided on the outer periphery, a known adhesive may be appropriately applied to the surface of the conductive substrate.

[0053] <Elastic layer> The elastic layer is preferably usually formed of a molded body of a rubber material. Examples of the rubber material include ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), fluororubber, silicone rubber, epichlorohydrin rubber, hydrogenated NBR, urethane rubber, and the like. These can be used alone or in combination of two or more. The elastic layer may be a single layer or may be composed of a plurality of layers. When the elastic layer is composed of a plurality of layers, the plurality of layers may include a plurality of layers formed of the same material among the rubber materials described above, or may include a plurality of layers formed of different materials from each other. From the viewpoint of suppressing the change in the dynamic friction coefficient between the developing roller and the photoreceptor, the MD-1 hardness measured at a temperature of 23 ° C on the outer surface of the developing roller may be, for example, 20 ° or more and 55 ° or less.

[0054] Conductivity can be imparted to the elastic layer by blending a conductivity-imparting agent such as an electron-conductive substance or an ion-conductive substance. Examples of the electronically conductive material include carbon blacks such as conductive carbon, for example, Ketjen black EC and acetylene black; carbon for rubber such as SAF (Super Abrasion Furnace), ISAF (Intermediate SAF), HAF (High Abrasion Furnace), FEF (Fast Extruding Furnace), GPF (General Purpose Furnace), SRF (Semi-Reinforcing Furnace), FT (Fine Thermal), and MT (Medium Thermal); carbon for colored (ink) materials subjected to oxidation treatment; metals such as copper, silver, and germanium, and metal oxides thereof. Among these, conductive carbon is preferred because it is easy to control conductivity even in small amounts. Examples of the ionically conductive material include inorganic ionically conductive materials such as sodium perchlorate, lithium perchlorate, calcium perchlorate, and lithium chloride; and organic ionically conductive materials such as modified aliphatic dimethylammonium ethosulfate and stearylammonium acetate. These conductivity-imparting agents are appropriately blended in necessary amounts according to the conductivity required for the elastic layer.

[0055] The elastic layer may further contain various additives such as particles, conductive agents, plasticizers, fillers, extenders, crosslinking agents, crosslinking accelerators, vulcanization aids, crosslinking aids, acid acceptors, curing inhibitors, antioxidants, and anti-aging agents, if necessary. These optional components can be blended in amounts that do not impair the features of the present disclosure. Examples of the crosslinking agent include sulfur-based crosslinking agents such as sulfur like powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur, and organic sulfur-containing compounds such as tetramethylthiuram disulfide and N,N-dithiobismorpholine. Considering imparting good properties as rubber, the blending ratio of sulfur is preferably 0.5 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the total amount of the rubber material. When using an organic sulfur-containing compound as the crosslinking agent, it is preferable to adjust the amount of the organic sulfur-containing compound used so that the sulfur content in the molecule is within the above range. Examples of the crosslinking accelerator for promoting crosslinking include thiuram-based accelerators, thiazole-based accelerators, thiourea-based accelerators, guanidine-based accelerators, sulfenamide-based accelerators, and dithiocarbamate-based accelerators. The crosslinking accelerator is blended in an appropriate amount according to the vulcanization rate required for the molding conditions and the shape of the molded product. Examples of the crosslinking aid include metal compounds such as zinc oxide and conventionally known crosslinking aids such as stearic acid, oleic acid, and fatty acids. When using a crosslinking aid, the content ratio of the crosslinking aid is preferably 0.1 parts by mass or more and preferably 7.0 parts by mass or less with respect to 100 parts by mass of the total amount of the rubber material. The acid acceptor is used to prevent chlorine-based gases generated from epichlorohydrin rubber or CR during crosslinking from remaining inside the electrophotographic member of the finished product, or from causing crosslinking inhibition or contamination of other members. As the acid acceptor, various substances that act as acid receptors can be used, but hydrotalcites with excellent dispersibility are preferably used. Examples of the filler include zinc oxide, silica, carbon black, talc, calcium carbonate, magnesium carbonate, and aluminum hydroxide. By blending these fillers, an improvement in the mechanical strength of the binder resin can be expected. Also, by using conductive carbon black that functions as an electron conductive agent as the filler, as described above, electron conductivity can be imparted to the electrophotographic member. The filler is blended in an appropriate required amount according to the properties required for the molded product.

[0056] Next, the configuration of the toner supply roller used in the present invention will be described in detail. [Toner Supply Roller] In the present invention, as the toner supply roller, one having a conductive shaft body and a resin layer on the shaft body can be used.

[0057] [Shaft Body] The shaft body functions as a support member of the toner supply roller and as an electrode. The shaft body is made of a conductive material such as a metal or alloy like aluminum, copper alloy, or stainless steel; iron plated with chromium or nickel; or a conductive synthetic resin. The shaft body is solid cylindrical or hollow cylindrical.

[0058] [Resin Layer] From the viewpoint of strength, the resin layer preferably contains a crosslinked urethane resin described later. Also, the resin layer is preferably a foamed layer having voids capable of storing toner particles therein in order to uniformly supply toner particles to the surface of the developing roller as a toner supply roller. Examples of the voids include a large number of through and non-through holes. Another example of the voids may be a porous state of interconnected bubbles (continuous foam). The foamed layer containing the crosslinked urethane resin is preferably in a continuous foam state with large voids. Physical property values such as the average cell diameter, cell number, air permeability, and density of the entire layer on the surface of the foamed layer having such voids are important for the function of the foamed layer. The physical property values of the foamed layer are not particularly limited, but preferably have values within the following numerical ranges, for example. Average cell diameter on the surface: 100 μm or more and 500 μm or less Cell number: 50 cells / inch or more and 300 cells / inch or less Air permeability: 0.5 L / min or more and 3.0 L / min or less Density: 0.05 g / cm 3 Above 0.20 g / cm 3 Below

[0059] [Crosslinked Urethane Resin] The crosslinked urethane resin is a reaction product of a polyol and a compound having an isocyanate group. Examples of the polyol used for synthesizing the crosslinked urethane resin include polyester polyol, polyether polyol, acrylic polyol, polycarbonate polyol, polycaprolactone polyol, etc. Among them, polyether polyol is preferable from the viewpoint of improving the flexibility of the crosslinked urethane resin. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, poly-1,4-butanediol, poly-1,5-pentanediol, polyneopentyl glycol, poly-3-methyl-1,5-pentanediol, poly-1,6-hexanediol, poly-1,8-octanediol, poly-1,9-nonanediol, etc. Among these, from the viewpoint of suppressing the increase in hardness, polypropylene glycol, poly-1,4-butanediol, poly-1,5-pentanediol, polyneopentyl glycol, poly-3-methyl-1,5-pentanediol, poly-1,6-hexanediol are preferable. Examples of the polyester polyol include polyester polyols obtained by the condensation reaction of a diol component such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, or a triol component such as trimethylolpropane, and a dicarboxylic acid such as adipic acid, suberic acid, sebacic acid, phthalic anhydride, terephthalic acid, hexahydroxyphthalic acid. Among these, from the viewpoint of suppressing the increase in the hardness of the resin layer, polyester polyols obtained by the condensation reaction of a diol component such as propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, and a dicarboxylic acid such as adipic acid, suberic acid, sebacic acid are preferable. Examples of the polycaprolactone polyol include poly-ε-caprolactone, poly-γ-caprolactone, etc. In addition, examples of the polycarbonate polyol include those obtained by a condensation reaction of a diol component such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, a dialkyl carbonate such as phosgene or dimethyl carbonate, or a cyclic carbonate such as ethylene carbonate. Among these, from the viewpoint of suppressing an increase in the hardness of the resin layer, a polycarbonate polyol obtained by a condensation reaction of a diol component such as neopentyl glycol, 3-methyl-1,5-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol and a dialkyl carbonate such as dimethyl carbonate is preferable. These polyol components may be prepolymers chain-extended in advance with an isocyanate compound such as 2,4-tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), or isophorone diisocyanate (IPDI), if necessary.

[0060] <Isocyanate compound> The isocyanate compound is not particularly limited, but examples include aliphatic polyisocyanates such as ethylene diisocyanate and 1,6 - hexamethylene diisocyanate (HDI); alicyclic polyisocyanates such as isophorone diisocyanate (IPDI), cyclohexane - 1,3 - diisocyanate, and cyclohexane - 1,4 - diisocyanate; aromatic isocyanates such as 2,4 - tolylene diisocyanate, 2,6 - tolylene diisocyanate (TDI), 4,4’ - diphenylmethane diisocyanate (MDI), polymeric diphenylmethane diisocyanate, xylylene diisocyanate, and naphthalene diisocyanate; and copolymers, isocyanurate forms, TMP adduct forms, biuret forms, and blocked forms thereof can be used. Among these, aromatic isocyanates such as tolylene diisocyanate and diphenylmethane diisocyanate are preferred. The polyol component and the isocyanate compound are preferably mixed so that the ratio (molar ratio) of the isocyanate groups in the isocyanate compound to 1.0 of the hydroxyl groups in the polyol component is in the range of 1.0 or more and 2.0 or less. If the mixing ratio is within the above range, it is possible to suppress the remaining of unreacted components.

[0061] <Crosslinking agent> The material for synthesizing the crosslinked urethane resin preferably contains a crosslinking agent. Examples of the crosslinking agent include trifunctional or higher - functional isocyanates and trifunctional or higher - functional polyols, and a crosslinked structure can be formed by using these. Separately from these, known crosslinking agents suitable for urethane resins may also be used. Examples of known crosslinking agents suitable for urethane resins include amine - based crosslinking agents such as ethylenediamine and imide - based crosslinking agents such as carbodiimide.

[0062] <Other components in the resin layer> The resin layer may contain a conductive filler as long as it does not interfere with the effects of the present invention. As the conductive filler, carbon black; conductive metals such as aluminum and copper can be used. Among these, carbon black is particularly preferably used because it is relatively easily available and has high conductivity-imparting and reinforcing properties. In the resin layer, a catalyst, a foaming agent, a foam stabilizer, and other auxiliary agents can be used as needed. There are no particular restrictions on the catalyst, and it can be appropriately selected and used from various conventionally known catalysts. For example, amine-based catalysts (triethylenediamine, bis(dimethylaminoethyl)ether, N,N,N',N'-tetramethylhexanediamine, 1,8-diazabicyclo(5.4.0)undecene-7, 1,5-diazabicyclo(4.3.0)nonene-5, 1,2-dimethylimidazole, N-ethylmorpholine, N-methylmorpholine, etc.), organometallic catalysts (tin octylate, tin oleate, dibutyltin dilaurate, dibutyltin diacetate, tetra-i-propoxytitanium, tetra-n-butoxytitanium, tetrakis(2-ethylhexyloxy)titanium, etc.), and acid salt catalysts (carboxylates, formates, octylates, borates, etc.) that reduce the initial activity of the above amine-based catalysts and organometallic catalysts are used. The catalyst may be used alone or in combination of two or more. There are no particular restrictions on the foaming agent, and it can be appropriately selected and used from various conventionally known foaming agents. In particular, water is preferably used as a foaming agent because it reacts with polyisocyanate to generate carbon dioxide gas. Also, using other foaming agents in combination with water does not impair the gist of the present invention. There are no particular restrictions on the foam stabilizer, and it can be appropriately selected and used from various conventionally known foam stabilizers. As other auxiliary agents, crosslinking aids, flame retardants, colorants, ultraviolet absorbers, antioxidants, etc. may be used as needed as long as they do not interfere with the effects of the present invention.

[0063] [Process Cartridge, Electrophotographic Apparatus] The process cartridge according to the present invention is a process cartridge that is detachable from the main body of an electrophotographic apparatus, and is characterized by having the electrophotographic photoreceptor, developing roller, and toner supply roller described above. Here, the developing roller is configured to develop an electrostatic latent image formed on the surface of the photoreceptor, and the toner supply roller is disposed in contact with the developing roller and is configured to supply toner to the developing roller. Further, the electrophotographic apparatus according to the present invention is characterized by having the above-described process cartridge.

[0064] FIG. 1 shows, as an example, a main cross-section of a process cartridge 70 including a photoreceptor, a developing roller, and a toner supply roller. The process cartridge 70 has a photoreceptor unit 26 and a developing unit 4. The photoreceptor unit 26 includes a photoreceptor drum 1, a charging roller 2, and a cleaning member 6. The developing unit 4 includes a developing roller 25 and a toner supply roller 34. Around the photoreceptor drum 1, the above-described charging roller 2 and cleaning member 6 are disposed. The cleaning member 6 is composed of an elastic member 7 formed of a rubber blade and a cleaning support member 8. The tip of the elastic member 7 is disposed in contact with the photoreceptor drum 1 in a counter direction to the rotation direction of the photoreceptor drum 1. The toner removed from the surface of the photoreceptor drum 1 by the cleaning member 6 falls into the removed toner chamber 27. The photoreceptor drum 1 is rotationally driven in accordance with an image forming operation by transmitting the driving force of a main body driving motor (not shown), which is a driving source, to the photoreceptor unit 26. The charging roller 2 is rotatably attached to the photoreceptor unit 26 via a charging roller bearing, and is pressed toward the photoreceptor drum 1 by a charging roller pressing member and abuts against the photoreceptor drum 1, thereby rotating following the rotation of the photoreceptor drum 1. The developing unit 4 includes a developing roller 25 that rotates in contact with the photoreceptor drum 1, and a developing frame 31 that supports the developing roller 25. Around the developing roller 25, a toner supply roller 34 that rotates in the direction of arrow C in contact with the developing roller 25 and a developing blade 35 for regulating the toner layer on the developing roller 25 are respectively arranged. The elastic layer of the developing roller may be composed of, for example, a base layer and a surface layer. At this time, silicone rubber may be used for the base layer, urethane rubber may be used for the surface layer, and particles of urethane beads may be dispersed in the urethane rubber of the surface layer to set a desired roughness. The developing roller 25 and the photoreceptor drum 1 rotate so that their surfaces move in the same direction at the opposing part (contact part). With respect to a predetermined DC bias applied to the developing roller 25, the toner negatively charged by triboelectrification transfers only to the bright part potential part from the potential difference at the developing part in contact with the photoreceptor drum 1 to visualize the electrostatic latent image.

[0065] The developing blade 35 is arranged below the developing roller 25 in the plane of FIG. 1 and abuts against the developing roller 25 in the counter direction, regulating the coat amount of the toner supplied by the toner supply roller 34 and imparting charge. The developing blade 35 may be composed of a flexible plate-like member and a developing blade support for fixing the plate-like member. Further, the developing blade 35 may be composed of an elastic plate formed using SUS (stainless steel) or the like. The toner is triboelectrically charged and charged with electricity while the layer thickness is regulated by the sliding contact between the developing blade 35 and the developing roller 25. Also, a predetermined voltage is applied to the developing blade 35 from a blade bias power source (not shown) to stabilize the toner coat. The toner supply roller 34 is in contact with the developing roller 25 with a nip portion N. In the present invention, during operation (rotation), the moving direction of the surface of the toner supply roller 34 in the nip portion N and the moving direction of the surface of the developing roller 25 in the nip portion N are configured to be in opposite directions (counter configuration). That is, the moving direction of the surface of the developing roller 25 is configured to be opposite to the moving direction of the surface of the toner supply roller 34 at the contact position with the toner supply roller 34. The toner supply roller 34 and the developing roller 25 are in contact with a predetermined penetration amount, that is, the amount ΔE of the recess formed by the developing roller 25 making the toner supply roller 34 concave. The toner supply roller 34 and the developing roller 25 need to rotate in opposite directions with the following peripheral speed difference in the nip portion N. That is, the developing roller 25 and the toner supply roller 34 are configured to rotate so that R represented by the following formula (E1) satisfies 1.2 ≦ R ≦ 1.5. R = V RS / V D (E1) (In formula (E1), V RS represents the absolute value of the peripheral speed [m / s] of the toner supply roller 34, and V D represents the absolute value of the peripheral speed [m / s] of the developing roller 25.)

[0066] By this operation, while recovering the residual toner on the developing roller 25, toner is supplied to the developing roller 25. At this time, by adjusting the potential difference between the toner supply roller 34 and the developing roller 25, the recovery amount of the residual toner on the developing roller 25 and the toner supply amount to the developing roller 25 can be adjusted. The toner supply roller 34 includes, for example, a conductive support as a shaft body and a foam layer supported by the conductive support. Specifically, a core metal electrode with an outer diameter φ5 (mm) as a conductive support and a urethane foam layer as a foam layer composed of a continuous foam body (continuous foam) in which bubbles are connected to each other around the core metal electrode may be provided, and it rotates in the direction C in the figure during operation. By making the surface layer urethane a continuous foam body, a large amount of toner can penetrate into the toner supply roller 34. The resistance of the toner supply roller is, for example, 1×10 9It may be in Ω. The amount of toner supplied from the toner supply roller 34 to the developing roller 25, that is, the amount of indentation ΔE of the toner supply roller 34 formed into a concave shape by the developing roller 25, can be set to, for example, 1.0 mm.

[0067] Here, a method for measuring the resistance of the toner supply roller 34 will be described. The toner supply roller 34 is brought into contact with an aluminum sleeve having a diameter of 30 mm so that the amount of intrusion described later becomes 1.5 mm. By rotating this aluminum sleeve, the toner supply roller is rotationally driven at 30 rpm with respect to the aluminum sleeve. Next, a DC voltage of -50 V is applied to the developing roller 25. At this time, a 10 kΩ resistor is provided on the ground side, and the current is calculated by measuring the voltage across both ends thereof, and the resistance of the toner supply roller 34 is calculated. The surface cell diameter of the toner supply roller 34 can be, for example, 50 μm to 1000 μm. Here, the cell diameter refers to the average diameter of the foam cells in an arbitrary cross section. First, the area of the largest foam cell is measured from the enlarged image of the arbitrary cross section, and the equivalent diameter of a perfect circle is converted from this area to obtain the maximum cell diameter. And after deleting the foam cells that are 1 / 2 or less of this maximum cell diameter as noise, it refers to the average value of the individual cell diameters similarly converted from the remaining individual cell areas.

[0068] The toner supplied from the toner supply roller 34 to the surface of the developing roller 25 is triboelectrically charged by the sliding contact between the developing blade 35 and the developing roller 25, and while being given an electric charge, its layer thickness is regulated. Then, it is conveyed to the contact portion (developing portion) between the photosensitive drum 1 and the developing roller 25, and is transferred only to the bright part potential portion. The residual toner remaining on the surface of the developing roller 25 returns to the developing container again, is recovered from the surface of the developing roller 25 by the toner supply roller 34, and is stored inside the toner supply roller 34. The configuration for driving the developing roller 25 and the toner supply roller 34 preferably includes a driving force receiving portion, a first driving force transmission portion, and a second driving force transmission portion. Here, the driving force receiving portion is configured to receive a driving force for driving the toner supply roller 34. And the first driving force transmission portion is configured to transmit the driving force received by the driving force receiving portion to the toner supply roller 34. Also, the second driving force transmission portion is configured to transmit the driving force generated by the driving of the toner supply roller 34 to the developing roller 25. Since the rotational driving of the developing roller 25 is indirectly performed via the second driving force transmission portion with respect to the input of an external driving force, the second driving force transmission portion absorbs sudden frictional force fluctuations. Thereby, destabilization of the toner coat amount on the developing roller 25 is suppressed (Reference Patent Document: Japanese Patent Application Laid-Open No. 2014-134787). Specifically, since the developing roller 25 is in contact with both the toner supply roller 34 and the photosensitive drum 1, sudden frictional force fluctuations generated between the developing roller 25 and the photosensitive drum 1 affect the rotation of the toner supply roller 34 in contact with the developing roller 25. And there may be a case where the coat amount of the toner supplied onto the developing roller 25 by the toner supply roller 34 becomes unstable. In the above-described preferred configuration, first, the toner supply roller 34 is driven by the input of an external driving force, and then the developing roller 25 is driven via the second driving force transmission portion. Therefore, even when sudden frictional force fluctuations occur between the developing roller 25 and the photosensitive drum 1, the toner supply roller 34 is driven by an external driving force that is not affected by the frictional force fluctuations, and the second driving force transmission portion absorbs the frictional force fluctuations. Thereby, the toner supply roller 34 can stably supply toner to the developing roller 25. The above configuration for suppressing the destabilization of the toner coat amount caused by sudden frictional force fluctuations is suitable for suppressing banding during repeated use in the present invention. The second driving force transmission portion may include a third driving force transmission portion, a fourth driving force transmission portion, and a fifth driving force transmission portion. Here, the third driving force transmission portion is provided at an end portion of the shaft body of the toner supply roller 34 and is configured to transmit the driving force generated by the driving of the toner supply roller 34 to the fourth driving force transmission portion.Further, the fourth driving force transmission unit is configured to transmit the driving force to the fifth driving force transmission unit by being driven by the driving force received from the third driving force transmission unit. Further, the fifth driving force transmission unit is provided at an end of the shaft core body of the developing roller 25 and is configured to drive the developing roller 25 by receiving the driving force from the fourth driving force transmission unit.

[0069] FIG. 2 shows a schematic diagram of a specific example of a preferable configuration for driving the developing roller and the toner supply roller described above. The driving force input to the coupling (driving force receiving part) 101 is transmitted to the driving transmission member 103 through the intermediate body 102, and rotates the toner supply roller 134. Here, the combination of the intermediate body 102 and the driving force transmission member 103 corresponds to the first driving force transmission part described above. The rotational driving force transmitted to the toner supply roller 134 is transmitted to the gear (third driving force transmission part) 104a, the gear (fourth driving force transmission part) 104b, and the gear (fifth driving force transmission part) 104c in this order, and rotates the developing roller 125. Here, the configuration consisting of the combination of the gears 104a, 104b, and 104c corresponds to the second driving force transmission part described above. That is, the gear 104a is provided at the end of the shaft body 105 of the toner supply roller 134, and transmits the driving force generated by the driving of the toner supply roller 134 to the gear 104b. Subsequently, the gear 104b is driven by the driving force received from the gear 104a, and transmits the driving force to the gear 104c. The gear 104c is provided at the end of the shaft core body 106 of the developing roller 125, and drives the developing roller 125 by receiving the driving force from the gear 104b. Thereby, the driving force generated by the driving of the toner supply roller 134 is transmitted to the developing roller 125. In the example shown in FIG. 2, since there is play in the meshing portion between the gears 104a, 104b, and 104c, it is possible to absorb sudden frictional force fluctuations generated between the developing roller 125 and the photosensitive drum. And, since the driving force transmitted from the outside to the toner supply roller 134 through the coupling 101, the intermediate body 102, and the driving transmission member 103 is not affected by the frictional force fluctuations, the toner supply roller 134 is stably driven. Thereby, it is possible to suppress fluctuations in the toner supply amount from the toner supply roller 134 to the developing roller 125. Note that the specific configuration of the second driving force transmission part is not limited to the configuration consisting of the combination of the gears 104a, 104b, and 104c illustrated in FIG. 2. As the specific configuration of the second driving force transmission part, any configuration using any mechanism may be used as long as it is a configuration capable of transmitting the driving force generated by the driving of the toner supply roller 134 to the developing roller 125.

[0070] In a preferred configuration for driving the developing roller 125 and the toner supply roller 134 described above, it is necessary that the above R satisfies 1.2 ≦ R ≦ 1.5. For this purpose, it is sufficient that the toner supply roller 134, the second driving force transmission unit, and the developing roller 125 are drivingly connected as follows. That is, the radius of the developing roller 125 is r D [mm], the radius of the toner supply roller 134 is r RS [mm], and when λ is a value represented by the following formula (E4), each of the above configurations may be drivingly connected so as to satisfy the following formula (E5). Here, for the radius r D of the developing roller 125 and the radius r RS of the toner supply roller 134, λ represented by the following formula (E4) represents the ratio of the rotational angular velocities. λ = ω RS / ω D (E4) (In formula (E4), ω RS represents the rotational angular velocity [rad / s] of the toner supply roller 134, and ω D represents the rotational angular velocity [rad / s] of the developing roller 125.) 1.2 ≦ λ × r RS / r D ≦ 1.5 (E5) As an example, in the specific means shown in FIG. 2, the gear ratios of the three gears 104a, 104b, and 104c may be set so that 1.2 ≦ λ × r RS / r D ≦ 1.5 is satisfied.

[0071] Also, FIG. 3 shows a schematic diagram of another example of the configuration for driving the developing roller and the toner supply roller. The driving force input to the coupling 201 is transmitted to the gear 204a through the intermediate body 202, and is transmitted to the gears 204b and 204c in this order to rotationally drive the developing roller 225. The rotational driving force is transmitted to the gears 204d, 204e, and 204f in this order to rotationally drive the toner supply roller 234. In the present invention, from the viewpoint of well-balanced suppression of the paste concentration thinning during repeated use in a high-temperature and high-humidity environment and the HT concentration thinning during repeated use in a low-temperature and low-humidity environment, it is preferable that the above R satisfies 1.2 ≤ R ≤ 1.3. The process cartridge according to the present invention can be used in a laser beam printer, an LED printer, a copying machine, and the like.

Examples

[0072] Hereinafter, the present invention will be described in more detail using examples and comparative examples. The present invention is not limited by the following examples in any way as long as the gist thereof is not exceeded. In the description of the following examples, "parts" means mass basis unless otherwise specified. The film thickness of each layer of the electrophotographic photoreceptor manufactured in the examples and comparative examples was determined by a method using an eddy current type film thickness meter (Fischerscope (registered trademark), manufactured by Fischer Instruments) except for the charge generation layer, or by a method of converting from the mass per unit area to specific gravity. The film thickness of the charge generation layer was determined as follows. That is, a spectrophotometer (trade name: X-Rite504 / 508, manufactured by X-Rite) was pressed against the surface of the photoreceptor to measure the Macbeth density value. The film thickness was calculated from the measured Macbeth density value using a calibration curve previously obtained from the Macbeth density value and the film thickness measurement value by cross-sectional SEM image observation.

[0073] <Preparation of coating liquid for charge generation layer> [Synthesis example] In 100 g of α-chloronaphthalene, 5.0 g of o-phthalodinitrile and 2.0 g of titanium tetrachloride were heated and stirred at 200 ° C for 3 hours, then cooled to 50 ° C, and the precipitated crystals were filtered off to obtain a paste of dichlorotitanium phthalocyanine. Next, this was stirred and washed with 100 mL of N,N-dimethylformamide heated to 100 ° C, and then washed twice with 100 mL of methanol at 60 ° C and repeatedly filtered off. Further, the obtained paste was stirred in 100 mL of deionized water at 80 ° C for 1 hour, filtered off to obtain 4.3 g of a blue titanyl phthalocyanine pigment. [Milling example] 0.5 part of the titanyl phthalocyanine pigment obtained in the synthesis example, 10 parts of tetrahydrofuran, and 15 parts of glass beads with a diameter of 0.9 mm were milled using a sand mill at a cooling water temperature of 18°C for 48 hours. The sand mill used here was a sand mill (K-800, manufactured by Igarashi Machinery Manufacturing Co., Ltd. (currently Imex), disk diameter 70 mm, number of disks 5). At this time, the operation was carried out under the condition that the disk rotated 500 times per minute. The liquid thus treated was filtered through a filter (product number: N-NO.125T, pore diameter: 133 μm, manufactured by NBC Mesh Tech) to remove the glass beads. After adding 30 parts of tetrahydrofuran to this liquid, it was filtered, and the filtrate on the filter was thoroughly washed with methanol and water. Then, the washed filtrate was vacuum dried to obtain 0.45 part of the titanyl phthalocyanine pigment. The obtained pigment had a strong peak at a Bragg angle 2θ of 27.2° ± 0.3° in the X-ray diffraction spectrum using CuKα radiation. The following materials were prepared. · 12 parts of the titanyl phthalocyanine pigment obtained in the milling example · 10 parts of polyvinyl butyral (trade name: Esrec BX-1, manufactured by Sekisui Chemical Co., Ltd.) · 158 parts of cyclohexanone · 402 parts of glass beads with a diameter of 0.9 mm These were dispersion-treated using a sand mill (K-800, manufactured by Igarashi Machinery Manufacturing Co., Ltd. (currently Imex), disk diameter 70 mm, number of disks 5) at a cooling water temperature of 18°C for 4 hours. At this time, the operation was carried out under the condition that the disk rotated 1,800 times per minute. After removing the glass beads, 369 parts of cyclohexanone and 527 parts of ethyl acetate were added to this dispersion to prepare a coating solution for the charge generation layer.

[0074] <Preparation of Coating Solution for Charge Transport Layer> [Preparation of Coating Solution 1 for Charge Transport Layer] The following materials were prepared. · 100 parts of CTM9 as a charge transport material · 183 parts of polycarbonate A resin having a structural unit represented by the following formula (A) [Chemical formula] · Polycarbonate Z resin having a structural unit represented by the following formula (Z): 183 parts [Chemical formula] · Siloxane resin (trade name: DC200, manufactured by Toray Dow Corning): 0.03 part These were dissolved in a mixed solvent of 1400 parts of tetrahydrofuran and 600 parts of 1,4 - dioxane to prepare a coating solution for the charge transport layer.

[0075] [Preparation of Coating Solution 2 for Charge Transport Layer] A coating solution 2 for the charge transport layer was prepared in the same manner as the coating solution 1 for the charge transport layer, except that 9 parts of a 30 wt% dispersion of indium tin oxide particles (ITO particles) as metal oxide particles (manufactured by Sigma - Aldrich) was added to the coating solution 1 for the charge transport layer.

[0076] [Preparation of Coating Solution for Protective Layer] [Preparation of Coating Solution 1 for Protective Layer] The following materials were prepared. · ACM2 (Ebecryl E8301, manufactured by Daicel Ornex) as a (meth)acrylic compound: 100 parts · 30 wt% dispersion of indium tin oxide (ITO) particles as metal oxide particles (manufactured by Sigma - Aldrich): 38 parts · Crosslinkable ether - modified polymethylsiloxane having an acryloyl group (UV3500, manufactured by BYK): 0.16 part These were dissolved in 420 parts of ethanol to prepare a coating solution 1 for the protective layer. The volume ratio of the solid content in the obtained coating solution 1 for the protective layer is shown in Table 1. When calculating the volume ratio of the solid content in the coating solution 1 for the protective layer, the following values were used. · Specific gravity of the (meth)acrylic compound ACM2: 1.2 [g / cm 3 · Specific gravity of ITO particles: 7.1 [g / cm 3 ​​· Specific gravity of crosslinkable ether-modified polymethylsiloxane having an acryloyl group: 1.0 [g / cm 3 In Table 1, MOx1 to MOx4 each represent different types of metal oxide particles. The ratios for the (meth)acrylic compounds described in Table 1 indicate the volume-based ratios of each (meth)acrylic compound with respect to the total of all (meth)acrylic compounds. Also, the ratios for the metal oxide particles described in Table 1 indicate the volume-based ratios of each metal oxide particle with respect to the entire surface layer.

[0077]

Table 1

[0078] [Preparation of Coating Liquids 2 to 43 for Protective Layer] In the preparation of the coating liquid 1 for the protective layer, coating liquids 2 to 43 for the protective layer were prepared in the same manner as the preparation of the coating liquid 1 for the protective layer, except that the types and ratios of the (meth)acrylic compounds and metal oxide particles were changed or added as shown in Table 1. Table 2 shows the results of measuring the volume resistivity of each metal oxide particle used in Table 1 according to <Measurement Method of Volume Resistivity of Metal Oxide Particles>. In Tables 1 and 2, "ITO" represents "indium tin oxide", "SnO" represents "tin(II) oxide", "TiO2" represents "titanium(IV) oxide (titania)", "ZnO" represents "zinc oxide", "Al2O3" represents "aluminum oxide (alumina)", "SrTiO3" represents "strontium titanate", and "ZrO2" represents "zirconium dioxide (zirconia)".

[0079]

Table 2

[0080] <Manufacture of Electrophotographic Photoreceptor> (Photoreceptor Production Example 1) ​An aluminum cylinder (JIS - A3003, aluminum alloy) with a length of 257 mm and a diameter of 24 mm, manufactured by a manufacturing method including an extrusion process and a drawing process, was prepared. Cutting was performed on this using a diamond sintered tool. As a cleaning process, this cylinder was degreased, etched for 1 minute with a 2 mass% sodium hydroxide solution, neutralized, and further rinsed with pure water in sequence. Next, anodic oxidation was carried out for 20 minutes at a current density of 1.0 A / dm 2 in a 10 mass% sulfuric acid solution to form an anodic oxide film on the cylinder surface. Next, after rinsing with water, it was immersed in a 1 mass% nickel acetate solution at 80 °C for 15 minutes for sealing treatment. Further, rinsing with pure water and drying were performed to obtain an anodized support.

[0081] A coating solution for a charge generation layer was dip - coated on this support to form a coating film, and the coating film was heated and dried at 100 °C for 15 minutes to form a charge generation layer with a film thickness of 0.24 μm. Next, a coating solution 1 for a charge transport layer was dip - coated on the above - mentioned charge generation layer to form a coating film, and the coating film was heated and dried at 120 °C for 1 hour to form a charge transport layer with a film thickness of 18 μm. Next, a coating solution 1 for a protective layer was dip - coated on the above - mentioned charge transport layer to form a coating film, and the coating film was irradiated with an electron beam of a dose of 86 kGy, and then naturally cooled in the atmosphere until the temperature of the coating film reached 25 °C. Thereafter, heat treatment was performed for 1 hour under the condition that the temperature of the coating film reached 120 °C to form a protective layer with a film thickness of 1.5 μm. The heat treatment of the coating film of each layer was performed using an oven set at each temperature. In this way, a cylindrical (drum - shaped) photoreceptor 1 was manufactured.

[0082] (Photoreceptor Manufacturing Examples 2 - 43) In Photoreceptor Manufacturing Example 1, Photoreceptors 2 - 43 were produced in the same manner as Photoreceptor Manufacturing Example 1, except that the type of the coating solution for the protective layer used was changed to Coating Solutions 2 - 43 for the protective layer.

[0083] (Photoreceptor Manufacturing Example 44) In Photoconductor Manufacturing Example 1, a photoconductor 44 was produced in the same manner as in Photoconductor Manufacturing Example 1, except that the coating liquid 1 for the charge transport layer was changed to the coating liquid 2 for the charge transport layer and no protective layer was formed.

[0084] <Manufacture of Development Roller 1> (Preparation of Substrate) A stainless steel (SUS304) shaft core with an outer diameter of 6 mm and a length of 270 mm was prepared. A conductive vulcanized adhesive (product name: Metalock U-20, manufactured by Toyo Chemical Laboratory) was applied to the circumferential surface of the shaft core and baked to prepare the shaft core as the substrate. (Formation of the First Elastic Layer) The material for the elastic layer shown in Table 3 was mixed using a 6-liter pressure kneader (product name: TD6-15MDX, manufactured by Toshing) at a filling rate of 70% by volume and a blade rotation speed of 30 rpm for 16 minutes to obtain a mixture A.

[0085]

Table 3

[0086] Next, the materials shown in Table 4 were processed on an open roll with a roll diameter of 12 inches (0.30 m) at a front roll rotation speed of 10 rpm, a rear roll rotation speed of 8 rpm, and a roll gap of 2 mm, with a total of 20 left and right reversals. Then, the roll gap was set to 0.5 mm and thin passing was performed 10 times to obtain a mixture B.

Table 4

[0087] Next, the above mixture B was formed into a cylindrical shape coaxially around the shaft core by extrusion molding using a crosshead while being extruded simultaneously with the shaft core to form a layer of mixture B on the outer peripheral surface of the shaft core. An extruder with a cylinder diameter of 45 mm (Φ45) and an L / D of 20 was used, and the temperature control during extrusion was set to 90 °C for the head, 90 °C for the cylinder, and 90 °C for the screw. Both ends of the layer of mixture B in the longitudinal direction of the shaft core were cut, and the length of the layer of mixture B in the longitudinal direction of the shaft core was set to 237 mm. Subsequently, the shaft core was heated in an electric furnace at a temperature of 160°C for 40 minutes to vulcanize the layer of Mixture B, thereby forming a vulcanized member. Subsequently, the surface of the vulcanized member was polished with a polishing machine using the plunge cut grinding method to obtain a roller having a first elastic layer with a thickness of 3.0 mm formed on the outer periphery of the mandrel.

[0088] (Formation of the second elastic layer) As the material for the second elastic layer, the materials other than the roughness-forming particles in Table 5 were stirred and mixed. Thereafter, it was dissolved in methyl ethyl ketone (manufactured by Kishida Chemical Co., Ltd.) so that the solid content concentration became 30% by mass, mixed, and then uniformly dispersed with a sand mill. Methyl ethyl ketone was added to this mixed solution to adjust the solid content concentration to 25% by mass, and the material shown in the column of the roughness-forming particles in Table 5 was added thereto, followed by stirring and dispersing with a ball mill to obtain a coating liquid for the second elastic layer. The roller having the first elastic layer formed thereon was immersed in this coating liquid and coated so that the film thickness of the second elastic layer became about 15 μm. Thereafter, it was heated at a temperature of 135°C for 60 minutes to dry and cure the coating film to form the second elastic layer. Thereby, the developing roller 1 was obtained.

[0089]

Table 5

[0090] (Analysis of the developing roller 1) The developing roller 1 was left standing in an environment at a temperature of 23°C and a relative humidity of 53% for 24 hours. Next, using a micro rubber hardness meter (product name: MD-1capa, manufactured by Kobunshi Keiki Co., Ltd.) with a pressing needle having a diameter of 0.16 mm, 12 points were measured at intervals of 90° in the circumferential direction at the center and at positions 20 mm inward from both ends of the developing roller, and the average value of these measured values was defined as the MD-1 hardness. The MD-1 hardness of the developing roller 1 was 50°.

[0091] (Manufacture of the toner supply roller 1) A mandrel made of stainless steel (SUS304) with a diameter of 5 mm, coated with a primer (product name: DY39-012, manufactured by Toray Dow Corning Co., Ltd.) and baked, was prepared as the shaft body. Further, a urethane rubber composition obtained by blending the following materials (A) to (F) and mixing the blend was foamed by the mechanical froth method to produce a polyurethane foam. This polyurethane foam was cut into a rectangular parallelepiped shape with sides of 19 mm square and a length of 220 mm, and a Φ5 mm shaft insertion hole was provided along the longitudinal direction at the center of the 19 mm square face. The shaft was press-fitted into the shaft insertion hole, and the shaft and the polyurethane foam were adhered by heat welding. Thereafter, the outer periphery of the polyurethane foam was polished by a traverse-type processing machine to produce a conductive roll with an outer diameter of 13 mm. (A) Carbon black (Ketjen black 600JD): 5.0 parts by mass (B) Polyol A (polyethylene propylene ether triol with a number average molecular weight of 2000, trade name: Actocol EP-550N, manufactured by Mitsui Chemicals, Inc.): 100.0 parts by mass (C) Polyisocyanate mixture (NCO% = 45, containing 20% MDI, trade name: Cosmonate TM20, manufactured by Mitsui Chemicals, Inc.): 24.4 parts by mass (D) Silicone foam stabilizer (trade name: SRX274C, manufactured by Toray Dow Corning Silicone Co., Ltd.): 1.0 part by mass (E) Tertiary amine catalyst A (mixture of bis(2-dimethylaminoethyl) ether and dipropylene glycol, trade name: TOYOCAT-ET, manufactured by Tosoh Corporation): 0.3 part by mass (F) Amine catalyst B (trade name: TOYOCAT-L33, manufactured by Tosoh Corporation): 0.2 part by mass

[0092] [Evaluation] <Process cartridge used for evaluation> The above photoreceptors 1 to 44, the developing roller 1 and the toner supply roller 1 were attached to a process cartridge schematically shown in FIG. 1. As the process cartridges for attaching the above photoreceptors, the following seven types were prepared. First, as shown in FIG. 2, the coupling 101, the intermediate body 102, the driving force transmission member 103, and the gears 104a to 104c were arranged. Thereby, the driving force is configured to be input to the end portion of the shaft body 105 of the toner supply roller 134. Further, the moving direction of the surface of the developing roller 125 and the moving direction of the surface of the toner supply roller 134 are made to be opposite to each other at the position where the developing roller 125 and the toner supply roller 134 are in contact with each other (counter configuration). Then, the peripheral speed V of the developing roller 125 D and the peripheral speed V of the toner supply roller RS The gear ratios of the respective gears 104a to 104c shown in FIG. 2 and the radius r of the developing roller 125 are set so that R determined by the ratio of D and the radius r of the toner supply roller 134 RS are appropriately set. Specifically, five types of process cartridges were prepared in which each value was set so that R would be five types of values of 1.15, 1.25, 1.40, 1.50, and 1.60. Next, as shown in FIG. 2, the driving force is configured to be input to the end portion of the shaft body 150 of the toner supply roller 134 in the same manner as described above. Further, in the configuration shown in FIG. 2, the number of gears used was changed. Thereby, the moving direction of the surface of the developing roller 125 and the moving direction of the surface of the toner supply roller 134 are made to be the same as each other at the position where the developing roller 125 and the toner supply roller 134 are in contact with each other (hereinafter referred to as "with configuration"). Then, the peripheral speed V of the developing roller D and the peripheral speed V of the toner supply roller RS The gear ratios of the respective gears (not shown) and the radius r of the developing roller are set so that R determined by the ratio of D and the radius r of the toner supply roller RS are set. Specifically, two types of process cartridges were prepared in which each value was set so that R would be two types of values of 1.15 / 1.25.

[0093] <Evaluation> Under the environment of temperature 32.5°C and relative humidity 80%, the charging potential was set to -550V and the exposure potential was set to -100V, and 100,000 continuous solid images printed with the toner were passed through the paper (printing) (HH-solid density thin durability). Separately from this, under the environment of temperature 15°C and relative humidity 10%, the charging potential was set to -550V and the exposure potential was set to -100V, and 100,000 continuous half-tone images of 1-dot cherry horse patterns printed with the toner were passed through the paper (printing) (LL-HT density thin durability). At this time, as the electrophotographic apparatus, a laser beam printer manufactured by Hewlett-Packard was modified and used. In addition, for the evaluation of this example, specifically, modified machines such as product name: Color Laser Jet Enterprise M653dn, product name: Color Laser Jet Enterprise M553dn, and product name: Color Laser Jet CP4525dn can be used. By evaluating the image density before and after the above two types of durability, the ranks of the solid density thin and HT density thin were determined.

[0094] (Solid density thin) In the 100,000 sheets of paper passed through for HH-solid density thin durability, the image density of 5 solid images from the 1st sheet to the 5th sheet, and the image density of 5 solid images from the 99,996th sheet to the 100,000th sheet were measured respectively using a Macbeth densitometer. Then, the difference in the average image density between the two was ranked according to the following criteria. A: The difference in average image density is less than 0.1 B: The difference in average image density is 0.1 or more and less than 0.2 C: The difference in average image density is 0.2 or more and less than 0.3 D: The difference in average image density is 0.3 or more and less than 0.5 E: The difference in average image density is 0.5 or more

[0095] (HT density thin) In the 100,000 sheets of paper passed through for LL-HT density thin durability, the image density of 5 solid images from the 1st sheet to the 5th sheet of the 100,000 sheets of paper passed through, and the image density of 5 solid images from the 99,996th sheet to the 100,000th sheet were measured respectively using a Macbeth densitometer. Then, the difference in the average image density between the two was ranked according to the following criteria. A: Average image density difference is less than 0.1 B: Average image density difference is 0.1 or more and less than 0.15 C: Average image density difference is 0.15 or more and less than 0.2 D: Average image density difference is 0.2 or more and less than 0.3 E: Average image density difference is 0.3 or more and less than 0.4 F: Average image density difference is 0.4 or more and less than 0.5

[0096] [Example 1] The photoreceptor 1 was attached to a process cartridge configured to have a counter structure and R = 1.25, and the above evaluation was performed. The obtained results are shown in Table 6 together with the sum value of (R i / ρ i ) from i = 1 to i = n. Note that the sum of (R i / ρ i ) from i = 1 to i = n was calculated from the relationship between the relative ratio of the (meth)acrylic compound in the surface layer of the photoreceptor 1 shown in Tables 1 and 2 and the volume resistivity ρ i [Ω·cm] and the volume ratio. In Table 6, Σ(R i / ρ i ) indicates the sum of (R i / ρ i ) from i = 1 to i = n. Also, the developing roller / toner supply roller configuration indicates the configuration regarding the directions of the moving direction of the surface of the developing roller and the moving direction of the surface of the toner supply roller at the position where the developing roller and the toner supply roller are in contact with each other.

[0097] [Examples 2 to 41, Comparative Examples 1 to 6] In Example 1, the evaluations of Examples 2 to 41 and Comparative Examples 1 to 6 were performed in the same manner as in Example 1, except that the photoreceptor used and the configuration of the process cartridge used were changed as shown in Table 6. The results are shown in Table 6.

[0098]

Table 6

[0099] The disclosure according to an embodiment of the present invention includes the following configuration. (Configuration 1) A process cartridge that is detachable from the electrophotographic apparatus main body, wherein the process cartridge has an electrophotographic photoreceptor, a developing roller that develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor, and a toner supply roller that is disposed in contact with the developing roller and supplies toner to the developing roller and the developing roller and the toner supply roller are configured such that the moving direction of the surface of the developing roller and the moving direction of the surface of the toner supply roller during operation are opposite to each other at the contact position between the developing roller and the toner supply roller, and R represented by the following formula (E1) rotates satisfying 1.2 ≦ R ≦ 1.5, and R = V RS / V D (E1) (In formula (E1), V RS represents the absolute value of the circumferential speed [m / s] of the toner supply roller, and V D represents the absolute value of the circumferential speed [m / s] of the developing roller.) The electrophotographic photoreceptor has a surface layer that is a polymerized film of a composition containing at least one (meth)acrylic compound selected from the group consisting of (meth)acrylic monomers and (meth)acrylic oligomers, and the surface layer contains metal oxide particles, characterized in that. (Configuration 2) The process cartridge according to Configuration 1, wherein the metal oxide particles include at least one kind of metal oxide particles selected from the group consisting of indium tin oxide particles, tin oxide particles, titanium oxide particles, zinc oxide particles, and aluminum oxide particles. (Configuration 3) n types (n is an integer of 1 or more) of the metal oxide particles are respectively metal oxide particles A i(where i is an integer from 1 to n), and the metal oxide particles A i has a volume resistivity of ρ i [Ω·cm], and the volume content of the metal oxide particles A in the entire surface layer in the surface layer i is R i [%], when The process cartridge according to Configuration 1 or 2, which satisfies the following formula (E2).

Number

Number

Explanation of Signs

[0100] 1 Photosensitive drum 2 Charging roller 4 Developing unit 6 Cleaning member 7 Rubber blade 8 Cleaning support member 20 Blowing prevention sheet 25 Developing roller 26 Photoconductor unit 27 Removed toner chamber 31 Developing frame 31a Toner storage chamber 31b Developing chamber 31c Opening 34 Toner supply roller 35 Developing blade 36 Toner conveying member 36a Stirring shaft 36b Sheet member 70 Process cartridge 101 Coupling 102 Intermediate body 103 Drive transmission member 104a Gear 104b Gear 104c Gear 125 Developing roller 135 Toner supply roller 201 Coupling 202 Intermediate body 204a Gear 204b Gear 204c Gear 204d Gear 204e Gear 204f Gear 225 Developing roller 234 Toner supply roller

Claims

1. A process cartridge that is detachable from an electrophotographic apparatus main body, wherein the process cartridge includes an electrophotographic photoreceptor, a developing roller that develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor, and a toner supply roller that is disposed in contact with the developing roller and supplies toner to the developing roller and the developing roller and the toner supply roller are configured such that the moving direction of the surface of the developing roller and the moving direction of the surface of the toner supply roller during operation are opposite to each other at the contact position between the developing roller and the toner supply roller, and R represented by the following formula (E1) rotates satisfying 1.2 ≦ R ≦ 1.5, and R = V ＲＳ / V Ｄ (E1) (In formula (E1), V ＲＳ represents the absolute value of the peripheral speed [m / s] of the toner supply roller, and V Ｄ represents the absolute value of the peripheral speed [m / s] of the developing roller.) the electrophotographic photoreceptor has a surface layer that is a polymerized film of a composition containing at least one (meth)acrylic compound selected from the group consisting of (meth)acrylic monomers and (meth)acrylic oligomers, and the surface layer contains metal oxide particles, characterized in that it is a process cartridge.

2. The process cartridge according to claim 1, wherein the metal oxide particles include at least one kind of metal oxide particles selected from the group consisting of indium tin oxide particles, tin oxide particles, titanium oxide particles, zinc oxide particles, and aluminum oxide particles.

3. The n types (n is an integer of 1 or more) of the metal oxide particles are respectively metal oxide particles A ｉ (i is an integer of 1 or more and n or less), and the volume resistivity of the metal oxide particles A ｉ is ρ ｉ [Ω·cm], and when the volume content of the metal oxide particles A ｉ in the entire surface layer with respect to the entire surface layer is R ｉ [%], then The process cartridge according to claim 1, satisfying the following formula (E2). 【Number 1】

4. The process cartridge according to claim 3, satisfying the following formula (E3). 【Number 2】

5. The metal oxide particles are 10 ３ The process cartridge according to claim 1, comprising metal oxide particles having a volume resistivity of 10 [[Ω·cm]] or less.

6. The process cartridge according to claim 1, wherein the metal oxide particles include indium tin oxide particles.

7. The process cartridge according to claim 1, wherein the (meth)acrylic compound includes at least one trifunctional or higher (meth)acrylic compound selected from the group consisting of trifunctional or higher (meth)acrylic monomers and trifunctional or higher (meth)acrylic oligomers.

8. The process cartridge according to claim 7, wherein the (meth)acrylic compound includes at least one hexafunctional (meth)acrylic compound selected from the group consisting of hexafunctional (meth)acrylic monomers and hexafunctional (meth)acrylic oligomers.

9. The process cartridge according to claim 1, wherein the surface layer does not contain an organic compound having a charge transport function.

10. a driving force receiving portion that receives a driving force for driving the toner supply roller, A first driving force transmission unit for transmitting the driving force received by the driving force receiving unit to the toner supply roller; A second driving force transmission unit for transmitting the driving force generated by the driving of the toner supply roller to the developing roller; The process cartridge according to claim 1, comprising:

11. The second driving force transmission unit includes a third driving force transmission unit, a fourth driving force transmission unit, and a fifth driving force transmission unit. The third driving force transmission unit is provided at an end of the shaft body of the toner supply roller, and transmits the driving force generated by the driving of the toner supply roller to the fourth driving force transmission unit. The fourth driving force transmission unit is driven by the driving force received from the third driving force transmission unit to transmit the driving force to the fifth driving force transmission unit. The fifth driving force transmission unit is provided at an end of the shaft core of the developing roller, and drives the developing roller by receiving the driving force from the fourth driving force transmission unit. The process cartridge according to claim 10.

12. Let the radius of the developing roller be r Ｄ [mm], and let the radius of the toner supply roller be r ＲＳ [mm]. When λ is a value represented by the following formula (E4), the toner supply roller, the second driving force transmission unit, and the developing roller are drivingly connected so as to satisfy the following formula (E5). The process cartridge according to claim 10. λ = ω ＲＳ / ω Ｄ (E4) (In formula (E4), ω ＲＳ represents the rotational angular velocity [rad / s] of the toner supply roller, and ω Ｄ represents the rotational angular velocity [rad / s] of the developing roller.) 1.2 ≤ λ × r ＲＳ / r Ｄ ≤ 1.5 (E5)

13. The process cartridge according to claim 1, wherein R satisfies 1.2 ≤ R ≤ 1.

3.

14. An electrophotographic apparatus, comprising the process cartridge according to any one of claims 1 to 13.

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