JP2024079542A - Electrophotographic photoreceptor, process cartridge and electrophotographic device - Google Patents

Abstract

[Problem] To provide an electrophotographic photoreceptor that maintains high transferability for a long period of time. [Solution] An electrophotographic photoreceptor having a surface layer containing inorganic particles and a binder resin, the binder resin is a polymer of a polymerizable monomer composition containing a polymerizable monomer having a polymerizable functional group, the polymerizable monomer composition contains a polymerizable monomer A represented by formula (1) as the polymerizable monomer, and the ratio of the volume of the inorganic particles to the volume of the binder resin in the surface layer is 0.5 or more and 3.0 or less. [Selected Figure] Figure 1

Description

The present invention relates to an electrophotographic photoreceptor, a process cartridge having the electrophotographic photoreceptor, and an electrophotographic apparatus.

Electrophotographic image forming methods include a transfer process in which an electrostatic latent image formed on an electrophotographic photoreceptor by image exposure is developed with toner to form a toner image, and the toner image is transferred from the electrophotographic photoreceptor to a transfer material (such as paper) with or without an intermediate transfer material. In the transfer process, it is required to efficiently transfer the toner image to the intermediate transfer material or transfer material with almost no residual toner image remaining on the surface of the electrophotographic photoreceptor. In other words, high transferability is required.

The adhesion between the toner and the surface of the electrophotographic photoreceptor during the transfer process is largely influenced by two factors: non-electrostatic adhesion and electrostatic adhesion. The former can be achieved by giving a shape to the surface of the electrophotographic photoreceptor to reduce the contact area with the toner and to make point contact with the toner as much as possible, thereby weakening the adhesion between the toner and the surface of the electrophotographic photoreceptor.

Patent Document 1 describes an electrophotographic photoreceptor having a surface layer formed using resin particles, a charge transport material having two or more polymerizable functional groups, and a polymerizable compound having 3 to 6 carbon atoms.

Patent document 2 describes an electrophotographic photoreceptor having a surface layer formed using organic resin particles, a hole transporting compound, and a polymerizable compound having 7 or more carbon atoms.

JP 2020-46575 A JP 2019-45862 A

According to the inventors' investigations, in the electrophotographic photoreceptors described in Patent Documents 1 and 2, it was difficult to reduce the contact area between the surface of the electrophotographic photoreceptor and the toner due to the protrusions resulting from the particles contained in the surface layer of the electrophotographic photoreceptor. In addition, the particles in the surface layer were difficult to retain after repeated use over a long period of time, making it difficult to maintain high transferability for a long period of time.

The object of the present invention is to provide an electrophotographic photoreceptor that maintains high transferability for a long period of time. It is also an object of the present invention to provide a process cartridge and an electrophotographic apparatus that have the electrophotographic photoreceptor.

The present invention provides an electrophotographic photoreceptor having a surface layer containing inorganic particles and a binder resin,
the binder resin is a polymer of a polymerizable monomer composition containing a polymerizable monomer having a polymerizable functional group,
The polymerizable monomer composition contains, as the polymerizable monomer, a polymerizable monomer A represented by the following formula (1):
a ratio of the volume of the inorganic particles to the volume of the binder resin in the surface layer is 0.5 or more and 3.0 or less;
The electrophotographic photoreceptor is characterized in that
(In formula (1), ^R1 represents a hydrogen atom or a methyl group, and ^R2 represents a linear alkyl group having 10 to 20 carbon atoms.)
The present invention also provides a process cartridge which integrally supports the electrophotographic photosensitive member and at least one means selected from the group consisting of a charging means, a developing means and a cleaning means, and is detachably mountable to the main body of an electrophotographic apparatus.
The present invention also relates to an electrophotographic apparatus having the above electrophotographic photoreceptor, a charging means, an exposing means, a developing means and a transferring means.

According to the present invention, it is possible to provide an electrophotographic photoreceptor that maintains high transferability for a long period of time. Furthermore, according to the present invention, it is possible to provide a process cartridge and an electrophotographic device that have the electrophotographic photoreceptor.

FIG. 2 is a diagram showing an example of a layer structure of an electrophotographic photoreceptor. 1 is a conceptual diagram of a surface layer of an electrophotographic photosensitive member observed from above (surface observation). FIG. 1 is a diagram illustrating an example of a configuration of an electrophotographic apparatus.

[Electrophotographic Photoreceptor]
The surface layer of the electrophotographic photoreceptor means the layer located on the outermost surface of the electrophotographic photoreceptor, and means the layer having the surface that comes into contact with the toner. The surface of the electrophotographic photoreceptor is the surface of the surface layer of the electrophotographic photoreceptor.

Figure 1 is a diagram showing an example of the layer structure of an electrophotographic photoreceptor. In Figure 1, 101 is a support, 102 is an undercoat layer, 103 is a charge generation layer, and 104 is a charge transport layer. 105 is a surface layer, and 106 and 107 are inorganic particles.

The method for producing the electrophotographic photoreceptor of the present invention includes a method of preparing the coating liquid for each layer described later, coating the layers in the desired order to form a coating film, and drying the coating film. Examples of the coating method for the coating liquid include dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, ring coating, and dispense coating. Among these, dip coating is preferred from the viewpoints of efficiency and productivity.
Each layer will be described below.

<Surface layer>
The electrophotographic photoreceptor of the present invention is
An electrophotographic photoreceptor having a surface layer containing inorganic particles and a binder resin,
the binder resin is a polymer of a polymerizable monomer composition containing a polymerizable monomer having a polymerizable functional group,
The polymerizable monomer composition contains, as the polymerizable monomer, a polymerizable monomer A represented by the following formula (1):
The ratio of the volume of the inorganic particles to the volume of the binder resin in the surface layer is 0.5 or more and 3.0 or less.
In the above formula (1), ^R1 represents a hydrogen atom or a methyl group, and ^R2 represents a linear alkyl group having 10 to 20 carbon atoms.

The inventors speculate as follows about the reason why the above-mentioned configuration provides the effects of the present invention.
The adhesion force between the toner and the surface of the electrophotographic photoreceptor in the transfer process is roughly divided into non-electrostatic adhesion force and electrostatic adhesion force. The main factor of electrostatic adhesion force is the image force. The magnitude of the image force is proportional to the charge amount of the toner and inversely proportional to the square of the distance between the toner and the surface of the electrophotographic photoreceptor. Therefore, the higher the height of the convex part originating from the inorganic particles on the surface of the electrophotographic photoreceptor, the greater the distance between the toner and the surface of the electrophotographic photoreceptor, so the smaller the image force and the lower the adhesion force of the toner to the surface of the electrophotographic photoreceptor.

Therefore, in order to improve transferability, it is effective to increase the volume ratio of inorganic particles in the surface layer and push the inorganic particles up to the surface of the surface layer so that the inorganic particles near the surface of the surface layer can form protrusions of sufficient height on the surface of the electrophotographic photoreceptor. The ratio of the volume of inorganic particles to the volume of the binder resin in the surface layer of the electrophotographic photoreceptor is preferably 0.5 or more and 3.0 or less.

At least a portion of the inorganic particles contained in the surface layer of the electrophotographic photoreceptor is preferably inorganic particles that are partially exposed from the surface of the surface layer. The total volume of the exposed portions of the partially exposed inorganic particles is preferably 30% by volume or more and 80% by volume or less with respect to the total volume of the inorganic particles contained in the surface layer of the electrophotographic photoreceptor. It is further preferably 45% by volume or more and 85% by volume or less, and more preferably 50% by volume or more and 80% by volume or less.

When at least a part of the inorganic particles contained in the surface layer of the electrophotographic photoreceptor are inorganic particles partially exposed from the surface of the surface layer, the number-based average primary particle diameter of the inorganic particles contained in the surface layer is preferably 60 nm or more and 350 nm or less. When the number-based average primary particle diameter is 60 nm or more, the height of the exposed part of the inorganic particles partially exposed from the surface of the surface layer is likely to be high, which promotes the rotation of the toner and improves the transferability. When the number-based average primary particle diameter is 350 nm or less, the radius of curvature of the exposed part of the inorganic particles partially exposed from the surface of the surface layer is small, which makes it easy to make the contact between the surface of the electrophotographic photoreceptor and the toner close to point contact, which reduces the non-electrostatic adhesion force between the surface of the electrophotographic photoreceptor and the toner, and improves the transferability. More preferably, it is 85 nm or more and 325 nm or less, and even more preferably, it is 90 nm or more and 300 nm or less.

When at least a part of the inorganic particles contained in the surface layer of the electrophotographic photoreceptor is inorganic particles partially exposed from the surface of the surface layer, the surface layer of the electrophotographic photoreceptor preferably contains inorganic particles A and inorganic particles B as the inorganic particles. Inorganic particles A and inorganic particles B are inorganic particles having different number-based average primary particle diameters, and the number-based average primary particle diameter of inorganic particles A is larger than the number-based average primary particle diameter of inorganic particles B. In addition, when the number-based average primary particle diameter of inorganic particles A is DA [nm] and the number-based average primary particle diameter of inorganic particles B is DB [nm], it is preferable that DA and DB satisfy the following formulas (i) and (ii).
1.2≦DA/DB≦4.0 (i)
80≦DA≦350... (ii)

The maximum height difference Rz of the surface of the surface layer of the electrophotographic photoreceptor is preferably 100 nm or more and 400 nm or less. If the maximum height difference Rz is 100 nm or more, the rotation of the toner is promoted and the transferability is improved. If the maximum height difference Rz is 400 nm or less, external additives are less likely to accumulate in the recesses of the surface of the electrophotographic photoreceptor, and the developability is maintained well. Furthermore, if the maximum height difference Rz is 400 nm or less, discharge is less likely to occur in the transfer process, and roughness due to uneven density is less likely to occur. Roughness is easily noticeable in halftone images. Furthermore, the maximum height difference Rz is preferably 125 nm or more and 375 nm or less, and more preferably 150 nm or more and 350 nm or less.

The average length Rsm of the elements on the surface of the surface layer of the electrophotographic photoreceptor is preferably 100 nm or more and 400 nm or less. If the average length Rsm of the elements is 400 nm or less, the toner is less likely to come into contact with the recesses on the surface of the electrophotographic photoreceptor, the electrostatic adhesion force is reduced, and the transferability is improved. If the average length Rsm of the elements is 100 nm or more, the number of contact points between the toner and the surface of the electrophotographic photoreceptor becomes more appropriate, and the transferability is improved. Furthermore, the average length Rsm of the elements is preferably 150 nm or more and 375 nm or less, and more preferably 200 nm or more and 350 nm or less.

The adhesion between the binder resin and inorganic particles in the surface layer of the electrophotographic photoreceptor greatly affects the retention of the inorganic particles. Through long-term use of the electrophotographic photoreceptor, the inorganic particles in the surface layer of the electrophotographic photoreceptor are exposed to impacts. In other words, inorganic particles that are rubbed against members that come into contact with the electrophotographic photoreceptor are more likely to detach from the surface layer.

The binder resin contained in the surface layer of the electrophotographic photoreceptor is a polymer of a polymerizable monomer composition containing a polymerizable monomer having a polymerizable functional group. The polymerizable monomer composition contains a polymerizable monomer A represented by the above formula (1) as the polymerizable monomer. By using the polymer of the above polymerizable monomer composition as the binder resin contained in the surface layer of the electrophotographic photoreceptor, it is presumed that the long-chain alkyl group ( ^R2 is a straight-chain alkyl group having 10 to 20 carbon atoms. The same applies below.) in the above formula (1) is present in the surface layer so as to surround (entangle) the surface of the inorganic particles. As a result, it is considered that the adhesion between the binder resin in the surface layer and the inorganic particles is strengthened. Therefore, even if the inorganic particles in the surface layer are exposed to impacts through long-term use of the electrophotographic photoreceptor, the inorganic particles are less likely to be detached from the surface layer.

The polymerization reaction of the polymerizable monomer composition may include, for example, a thermal polymerization reaction, a photopolymerization reaction, and a radiation polymerization reaction. The polymerizable monomer composition may contain a polymerizable monomer other than the polymerizable monomer A as a polymerizable monomer having a polymerizable functional group. As the polymerizable monomer other than the polymerizable monomer A, a polymerizable monomer having a polymerizable functional group copolymerizable with the polymerizable monomer A is preferable. As the polymerizable functional group copolymerizable with the polymerizable monomer A, for example, a chain polymerizable functional group such as an acryloyl group or a methacryloyl group can be mentioned.

The polymerizable monomer A is a (meth)acrylic acid ester having a linear alkyl group having 10 to 20 carbon atoms. Examples of the polymerizable monomer A represented by the above formula (1) include decyl (meth)acrylate, dodecyl (meth)acrylate (common name: lauryl (meth)acrylate), tetradecyl (meth)acrylate (common name: myristyl (meth)acrylate), hexadecyl (meth)acrylate (common name: cetyl (meth)acrylate), octadecyl (meth)acrylate (common name: stearyl (meth)acrylate), and eicosyl (meth)acrylate (common name: eicosyl acrylate).

By using the polymerizable monomer A, the terminal of the long-chain alkyl group becomes free in the polymer, which is the binder resin, and is suitable for surrounding the surface of the inorganic particles. In addition, the ester bond (-CO-C-) in the vicinity of the polymerizable functional group (CH ₂ ═CR ¹ -), which has an effect on the generation of discharge products, is isolated from the air layer in the vicinity of the surface layer of the electrophotographic photoreceptor by the long-chain alkyl group (-R ² ). Therefore, a secondary effect of suppressing the generation of discharge products due to the decomposition of the polymer, which is the binder resin, can be expected.

As described above, ^R2 in the above formula (1) is a linear alkyl group having 10 to 20 carbon atoms. With a carbon number of 10 or more, the linear alkyl group is more likely to contact the inorganic particles for a long period, and the effect of improving the adhesion between the binder resin and the inorganic particles, which is presumed to be due to the surrounding of the inorganic particles, is enhanced. With a carbon number of 20 or less, the linear alkyl group is more likely to move, and the opportunity for the linear alkyl group to contact the inorganic particles increases, and the effect of improving the adhesion between the binder resin and the inorganic particles, which is presumed to be due to the surrounding of the inorganic particles, is enhanced. It is preferable that ^R2 is a linear alkyl group having 12 to 18 carbon atoms.

The content of the polymerizable monomer A in the polymerizable monomer composition is preferably 25% by mass or more relative to the total mass of the polymerizable monomers contained in the polymerizable monomer composition. The total mass of the polymerizable monomers contained in the polymerizable monomer composition means the total mass of all the polymerizable monomers when the polymerizable monomer A and polymerizable monomers other than the polymerizable monomer A are contained in the polymerizable monomer composition. By being 25% by mass or more, the effect of improving the adhesion between the binder resin and the inorganic particles, which is presumed to be due to the surrounding of the inorganic particles by the long-chain alkyl group in the polymerizable monomer A, is enhanced. Furthermore, it is preferably 30% by mass or more, and more preferably 35% by mass or more. On the other hand, the upper limit is a maximum of 100% by mass, but is preferably 60% by mass or less, and more preferably 50% by mass or less.

The polymerizable monomer composition preferably further contains, as a polymerizable monomer, a polymerizable monomer B having 6 or more polymerizable functional groups in addition to the polymerizable monomer A. The polymerizable monomer B is preferably a (meth)acrylic monomer having 6 or more polymerizable functional groups. When the polymerizable monomer composition further contains the polymerizable monomer B, the polymer of the polymerizable monomer composition tends to have a high crosslink density. Since the distance between the points where the polymerizable monomers in the polymer react with each other, that is, the distance between the so-called crosslinking points, becomes close, the molecular chains of the polymer tend to surround the inorganic particles three-dimensionally, and it is considered that the adhesion between the binder resin (polymer) in the surface layer and the inorganic particles becomes stronger.

It is preferable that the polymerizable monomer B does not have a triphenylamine skeleton.
The polymer of the polymerizable monomer composition is preferably a (meth)acrylic polymer from the viewpoint of friction resistance and high hardness. As the monomer forming the (meth)acrylic polymer, it is preferable to use a polyfunctional (meth)acrylic monomer that is easy to form a three-dimensional structure from the viewpoint of increasing the effect of surrounding inorganic particles. Examples of the polyfunctional (meth)acrylic monomer include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene oxide (EO) modified trimethylolpropane tri(meth)acrylate, propylene oxide (PO) modified trimethylolpropane tri(meth)acrylate, dipentaerythritol penta, hexa(meth)acrylate, isocyanuric acid ethylene oxide (EO) modified di(meth)acrylate, isocyanuric acid ethylene oxide (EO) modified tri(meth)acrylate, etc.

As the (meth)acrylic monomer having 6 or more polymerizable functional groups, one having a molecular weight of 540 or more and 1300 or less is preferred. By using one having a molecular weight of 540 or more and 1300 or less, the tackiness and elasticity of the binder resin in the surface layer are likely to decrease, and transferability is likely to increase. As the (meth)acrylic monomer having 6 or more polymerizable functional groups, for example, polypentaerythritol polyacrylate (a compound represented by the following formula (2-1), in which n is preferably 1 or more and 2 or less), urethane acrylate (a compound represented by the following formulas (M-1) to (M-4)), etc. can be mentioned.
Examples of the other acrylates include compounds represented by the following formulas (2-2) and (2-3).
In structural formula (2-2), at least two of R ²⁰¹ , R ²⁰⁵ and R ²⁰⁹ are groups having a (meth)acryloyloxy group, and R ²⁰¹ , R ²⁰⁵ and R ²⁰⁹ that are not groups having a (meth)acryloyloxy group, as well as R ²⁰² to R ²⁰⁴ , R ²⁰⁶ to R ²⁰⁸ and R ²¹⁰ to R ²¹² each represent a hydrogen atom or a methyl group.
In the structural formula (2-3), R ²²¹ and R ²³⁴ are groups having a (meth)acryloyloxy group, and R ²²² to R ²³³ are each a hydrogen atom or a methyl group.
In the formulas (2-2) and (2-3), examples of the group having a (meth)acryloyloxy group include groups represented by (L-1) to (L-5).
In formulas (L-1) to (L-5), * represents a bonding site to other structures, ^A1 and ^A2 represent a hydrogen atom or any of the groups represented by (L-1) to (L-4), and B represents a hydrogen atom or a methyl group.
Examples of the compound represented by the structural formula (2-2) include the compounds represented by (M-1) to (M-2). Examples of the compound represented by the structural formula (2-3) include the compounds represented by (M-3) to (M-4).

It is preferable that the compound having a polymerizable functional group does not have a charge transport structure at the same time as the chain polymerizable functional group. It is preferable that the polymerizable monomer B does not have a triphenylamine skeleton. The presence of a triphenylamine skeleton causes a catalytic action, making the ester bond site in the binder resin more susceptible to attack by ozone generated during discharge, which is expected to increase the production of discharge products and cause image defects such as image deletion.

Examples of inorganic particles include silica particles, metal oxide particles, and metal particles. Inorganic particles have a relatively low elasticity and tend to bring the contact between the surface of the electrophotographic photoreceptor and the toner into a state close to point contact, which tends to reduce the non-electrostatic adhesive force between the surface of the electrophotographic photoreceptor and the toner.

Among the inorganic particles, silica particles are preferable because silica particles have a relatively low relative dielectric constant and tend to reduce the electrostatic adhesive force between the surface of the electrophotographic photoreceptor and the toner.
Examples of silica particles include dry silica particles (silica particles produced by a dry method) and wet silica particles (silica particles produced by a wet method), with wet silica particles being preferred. Among the wet silica particles, sol-gel silica particles (wet silica particles obtained by a sol-gel method) are preferred.

The sol-gel silica particles may be hydrophilic, or may be made hydrophobic by subjecting the surface to hydrophobic treatment.
As the method of hydrophobic treatment, for example, in the sol-gel method, the method of removing the solvent from the silica sol suspension, drying, and then treating with a hydrophobic treatment agent can be mentioned.In addition, in the sol-gel method, the method of directly adding the hydrophobic treatment agent to the silica sol suspension and treating at the same time as drying can also be mentioned.From the viewpoint of controlling the particle size distribution of the sol-gel silica particles and the saturated water adsorption amount, the latter method of directly adding the hydrophobic treatment agent to the silica sol suspension and treating at the same time as drying is preferred.

Examples of the hydrophobic treatment agent include the following.
Chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, t-butyldimethylchlorosilane, and vinyltrichlorosilane;
Tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltrimethoxysilane, i-butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, i-butyl Alkoxysilanes such as ethyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, and γ-(2-aminoethyl)aminopropylmethyldimethoxysilane;
silazanes such as hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexabutyldisilazane, hexapentyldisilazane, hexahexyldisilazane, hexacyclohexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, and dimethyltetravinyldisilazane;
Silicone oils such as dimethyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil, alkyl modified silicone oil, chloroalkyl modified silicone oil, chlorophenyl modified silicone oil, fatty acid modified silicone oil, polyether modified silicone oil, alkoxy modified silicone oil, carbinol modified silicone oil, amino modified silicone oil, fluorine modified silicone oil, and terminal reactive silicone oil;
Siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, and octamethyltrisiloxane;
Fatty acids and their metal salts include fatty acids (long-chain fatty acids) such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid, and salts of the above fatty acids with metals such as zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

Among these hydrophobic treatment agents, alkoxysilanes, silazanes, and silicone oils are preferred from the viewpoint of ease of hydrophobic treatment. These hydrophobic treatment agents may be used alone or in combination of two or more kinds.

The surface layer may contain additives such as charge transport materials, antioxidants, UV absorbers, plasticizers, leveling agents, slippage agents, and abrasion resistance improvers. Examples of additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, and silicone oils.

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

<Support>
The electrophotographic photoreceptor preferably has a support. The support is preferably one having electrical conductivity (conductive support). The shape of the support may be cylindrical, belt-like, sheet-like, or the like. Among these, a cylindrical one (cylindrical support) is preferred. The surface of the support may be subjected to electrochemical treatment such as anodization, blasting, cutting, or the like.

Examples of materials for the support include metals, resins, and glass. Examples of metals include aluminum, iron, nickel, copper, gold, and alloys thereof (aluminum alloys, stainless steel). Among these, aluminum supports using aluminum or aluminum alloys are preferred. Resins and glass may be made conductive by mixing or coating them with a conductive material.

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

Examples of conductive particles include metal oxide particles, metal particles, and carbon black. Examples of metal oxide particles include zinc oxide particles, aluminum oxide particles, indium oxide particles, silicon oxide particles, zirconium oxide particles, tin oxide particles, titanium oxide particles, magnesium oxide particles, antimony oxide particles, and bismuth oxide particles. Examples of metal particles include aluminum particles, nickel particles, iron particles, nichrome particles, copper particles, zinc particles, and silver particles. Among these, metal oxide particles are preferred, and titanium oxide particles, tin oxide particles, and zinc oxide particles are more preferred.

When metal oxide particles are used as conductive particles, the surfaces of the metal oxide particles may be treated with a silane coupling agent or the like, or the metal oxide particles may be doped with elements such as phosphorus or aluminum or their oxides.

The conductive particles may also have a laminated structure in which pre-coated particles, such as titanium oxide particles, barium sulfate particles, or zinc oxide particles, are coated with a metal oxide having a different composition from the pre-coated particles. Examples of the coating material include metal oxide particles such as tin oxide.

When metal oxide particles are used as the conductive particles, the average primary particle size by number is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

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

The conductive layer may further contain silicone oil, resin particles, a masking agent such as titanium oxide, and the like.
The thickness of the conductive layer is preferably from 1 μm to 50 μm, and particularly preferably from 3 μm to 40 μm.

The conductive layer can be formed by preparing a coating liquid for the conductive layer containing the above-mentioned materials and solvent, forming a coating film of the coating liquid for the conductive layer, and drying the coating film. Examples of the solvent 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 liquid for the conductive layer include methods using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

<Undercoat layer>
In the present invention, an undercoat layer may be provided on the support or the conductive layer. The undercoat layer preferably contains a resin. The 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 even more preferably 0.3 μm or more and 30 μm or less.

Examples of resins include polyacrylic acid resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyethylene oxide resins, polypropylene oxide resins, ethyl cellulose resins, methyl cellulose resins, polyamide resins, polyamic acid resins, polyurethane resins, polyimide resins, polyamideimide resins, polyvinyl phenol resins, melamine resins, phenolic resins, epoxy resins, and alkyd resins. In addition, the resin may have a structure in which a resin having a polymerizable functional group is crosslinked with a monomer having a polymerizable functional group.

The undercoat layer may contain inorganic compounds or organic compounds in addition to the resin.
Examples of inorganic compounds include metals, metal oxides, and salts.
Examples of metals include gold, silver, aluminum, etc. Examples of oxides include zinc oxide, white lead, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, indium oxide, tin oxide, zirconium oxide, etc. Examples of salts include barium sulfate and strontium titanate.

The inorganic compound may be contained in the undercoat layer in a particulate state. The number-based average primary particle size of the inorganic compound particles is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less. The inorganic compound particles may be particles having a layered structure having a core particle and a coating layer that covers the core particle. The inorganic compound may have a surface treated with silicone oil, a silane compound, a silane coupling agent, or other organic silicon compounds or organic titanium compounds. The inorganic compound may also be doped with elements such as tin, phosphorus, aluminum, and niobium.

Examples of the organic compound include an electron transport material and a conductive polymer.
Examples of the conductive polymer include polythiophene, polyaniline, polyacetylene, polyphenylene, and polyethylenedioxythiophene.

Examples of electron transport substances include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, aryl halide compounds, silole compounds, and boron-containing compounds.

The electron transport material may have a polymerizable functional group and may be crosslinked with a resin having a polymerizable functional group capable of reacting with the polymerizable functional group, such as a hydroxyl group, a thiol group, an amino group, a carboxyl group, a vinyl group, an acryloyl group, a methacryloyl group, or an epoxy group.
These organic compounds may be present in the film in the form of particles, or may have a surface that has been treated.

The undercoat layer may contain various additives such as a leveling agent such as silicone oil, a plasticizer, and a thickener.
The undercoat layer can be obtained by preparing a coating solution for the undercoat layer containing the above-mentioned materials, applying the solution onto the support or the conductive layer to form a coating film, and then drying and curing the coating film.

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

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

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

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

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

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

The charge generating layer can be formed by preparing a coating solution for the charge generating layer containing the above-mentioned materials and solvent, forming a coating film of this on the undercoat layer, 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.
The thickness of the charge generating layer is preferably from 0.1 μm to 1.5 μm, and more preferably from 0.15 μm to 1.0 μm.

(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, resins having groups derived from these materials, etc. Among these, triarylamine compounds and benzidine compounds are preferred.

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

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

The ratio of the mass of the charge transport material to the mass of the resin in the charge transport layer is preferably from 4/10 to 20/10, and more preferably from 5/10 to 12/10.
The charge transport layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slipping agents, and abrasion resistance improvers. Specific examples of such 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, and boron nitride particles.

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

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

(2) Single-layer type photosensitive layer The single-layer type photosensitive layer can be formed by preparing a coating solution for the photosensitive layer containing a charge generating material, a charge transporting material, a resin and a solvent, forming this coating film on the undercoat layer, and drying it. The charge generating material, the charge transporting material and the resin are the same as the examples of materials in the above "(1) Multi-layer type photosensitive layer".
The thickness of the single-layer photosensitive layer is preferably from 10 μm to 45 μm, and more preferably from 25 μm to 35 μm.

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

[Configuration of Electrophotographic Apparatus]
The electrophotographic apparatus of the present invention can have the above-mentioned electrophotographic photoreceptor, as well as a charging means, an exposing means, a developing means and a transferring means.
FIG. 3 shows a schematic example of the configuration of an electrophotographic apparatus having a process cartridge equipped with the electrophotographic photosensitive member of the present invention.
The electrophotographic apparatus of this embodiment is a so-called tandem type electrophotographic apparatus having a plurality of image forming units a to d. The first image forming unit a forms images using toner of each color, yellow (Y), the second image forming unit b forms images using toner of each color, magenta (M), the third image forming unit c forms images using toner of each color, cyan (C), and the fourth image forming unit d forms images using toner of each color, black (Bk). These four image forming units are arranged in a line at regular intervals, and most of the configurations of the image forming units are substantially the same except for the color of the toner they contain. Therefore, the electrophotographic apparatus of this embodiment will be described below using the first image forming unit a.

The first image forming unit a has a photosensitive drum 1a, which is a drum-shaped electrophotographic photosensitive member, a charging roller 2a, which is a charging member, a developing means 4a, and a discharging means 5a.

The photosensitive drum 1a is an image carrier that carries a toner image, and is driven to rotate at a predetermined peripheral speed (process speed) in the direction of the arrow in the figure. The developing means 4a contains yellow toner, and develops the yellow toner on the photosensitive drum 1a with the developing roller 41a.

When a control unit such as a controller (not shown) receives an image signal, an image forming operation is started, and the photosensitive drum 1a is rotated. During the rotation process, the photosensitive drum 1a is uniformly charged to a predetermined voltage (charging voltage) with a predetermined polarity (negative polarity in this embodiment) by the charging roller 2a, and is exposed by the exposure unit 3a according to the image signal. As a result, an electrostatic latent image corresponding to the yellow color component image of the target color image is formed on the photosensitive drum 1a. Next, the electrostatic latent image is developed by the developing unit 4a at the development position and visualized as a yellow toner image on the photosensitive drum 1a. Here, the normal charging polarity of the toner contained in the developing unit 4a is negative polarity, and the electrostatic latent image is reversely developed by the toner charged to the same polarity as the charging polarity of the photosensitive drum 1a by the charging roller 2a. However, the present invention is not limited to this, and the present invention can also be applied to an electrophotographic device in which an electrostatic latent image is normally developed by a toner charged to the opposite polarity to the charging polarity of the photosensitive drum 1a. In addition, a large number of protrusions due to particles can be provided on the surface layer of the charging roller 2a. The convex portions provided on the surface layer of the charging roller 2a serve as spacers between the charging roller 2a and the photosensitive drum 1a in the charging section, and serve to prevent the charging roller 2a from being contaminated with the transfer residual toner, which is the toner that remains on the photosensitive drum 1a without being transferred in the primary transfer section described later, from coming into the charging section at places other than the convex portions.
The pre-exposure unit 5a as a charge removing means removes electricity by exposing the surface of the photosensitive drum 1a to light before the surface of the photosensitive drum 1a is charged by the charging roller 2a. By removing electricity from the surface of the photosensitive drum 1a, the pre-exposure unit 5a has a role of leveling the surface potential formed on the photosensitive drum 1 and a role of controlling the amount of discharge caused by discharge occurring in the charging section.

The endless, movable intermediate transfer belt 10 is conductive, contacts the photosensitive drum 1a to form a primary transfer section, and rotates at approximately the same peripheral speed as the photosensitive drum 1a. The intermediate transfer belt 10 is stretched by an opposing roller 13 as an opposing member, and a driving roller 11, a tension roller 12, and a metal roller 14a as tension members, and is stretched by the tension roller 12 with a total tension of 60 N. The intermediate transfer belt 10 can be moved by driving the driving roller 11 to rotate in the direction of the arrow in the figure.

The yellow toner image formed on the photosensitive drum 1a is primarily transferred from the photosensitive drum 1a to the intermediate transfer belt 10 as it passes through the primary transfer section.

In the second, third and fourth image forming units in FIG. 2, the photosensitive drums are 1b, 1c and 1d, the charging rollers are 2b, 2c and 2d, the exposure means are 3b, 3c and 3d, the developing means are 4b, 4c and 4d, the discharging means are 5b, 5c and 5d, the metal rollers are 14b, 14c and 14d, and the developing rollers are 41b, 41c and 41d.

Similarly, a magenta toner image of the second color, a cyan toner image of the third color, and a black toner image of the fourth color are formed and transferred to the intermediate transfer belt 10 in a superimposed manner. As a result, a four-color toner image corresponding to a target color image is formed on the intermediate transfer belt 10. Thereafter, the four-color toner images carried on the intermediate transfer belt 10 are secondarily transferred all at once to the surface of a transfer material P such as paper or an OHP sheet fed by a paper feed means 50 in the process of passing through a secondary transfer section formed by contact between the secondary transfer roller 15 and the intermediate transfer belt 10. The transfer material P to which the four-color toner images have been transferred by the secondary transfer is then heated and pressed in the fixing means 30, whereby the four-color toners are melted and mixed and fixed to the transfer material P. The toner remaining on the intermediate transfer belt 10 after the secondary transfer is cleaned and removed by a belt cleaning means 17 provided opposite the opposing roller 13 via the intermediate transfer belt 10.
The electrophotographic photoreceptor of the present invention can be used in laser beam printers, LED printers, copiers, and the like.

Hereinafter, methods for measuring the various physical properties of the electrophotographic photoreceptor and conductive particles according to the present invention will be described.
<Measurement of physical properties of electrophotographic photoreceptor>
<Method of measuring number average particle size of particles of the present invention>
The number-average particle size is measured using a Zetasizer Nano-ZS (manufactured by MALVERN). This device can measure particle size by dynamic light scattering. First, the sample to be measured is diluted and prepared so that the solid-liquid ratio is 0.10% by mass (±0.02% by mass), and then collected in a quartz cell and placed in the measurement section. When the sample is inorganic fine particles, water or a methyl ethyl ketone/methanol mixed solvent is used as the dispersion medium, and when the sample is resin particles or toner additives, water is used. As measurement conditions, the refractive index of the sample, the refractive index of the dispersion solvent, the viscosity, and the temperature are inputted into the control software Zetasizer software 6.30 and the measurement is performed. Dn is adopted as the number-average particle size.

The refractive index of the particles is taken from "Refractive index of solids" described on page 517 of Volume II of the Basic Chemistry Handbook, 4th Revised Edition (edited by the Chemical Society of Japan, Maruzen Co., Ltd.). The refractive index of the resin particles is the refractive index of the resin used in the resin particles that is built into the control software. However, if there is no built-in refractive index, the value described in the Polymer Database of the National Institute for Materials Science is used. The refractive index of the external toner additive is calculated by taking the weight average of the refractive index of the inorganic fine particles and the refractive index of the resin used in the resin particles. The refractive index, viscosity, and temperature of the dispersion solvent are selected from the values built into the control software. In the case of a mixed solvent, the weight average of the dispersion media to be mixed is taken.

<Method of measuring maximum height difference Rz and average length Rsm of elements on the surface of the surface layer of an electrophotographic photoreceptor>
The surface of the electrophotographic photoreceptor prepared in the examples was observed. The samples for which the surface was observed were cut out from the electrophotographic photoreceptor at ¼, ½, and ¾ positions from the end, and 5 mm square sample pieces were cut out from the electrophotographic photoreceptor at 120° intervals in the circumferential direction. The sample pieces were fixed to a sample holder so that the surface layer of the electrophotographic photoreceptor could be observed. For the sample pieces fixed to the sample holder, a scanning probe microscope SPM was used to measure the surface shape of a 3 μm square on the surface of the surface layer of the electrophotographic photoreceptor at one location on each sample. This measurement was performed at nine points on the sample pieces, and the average value of the maximum height difference Rz at those nine points was taken as the maximum height difference Rz of the surface of the surface layer of the electrophotographic photoreceptor of the present invention. Similarly, the average value of the average length Rsm of the elements at those nine points was taken as the average element length Rsm of the surface of the surface layer of the electrophotographic photoreceptor of the present invention.
As the SPM, a scanning probe microscope "JSPM-5200" (manufactured by JEOL Ltd.), a scanning probe microscope "E-sweep" (manufactured by Hitachi High-Tech Corporation), or a medium-sized probe microscope system AFM5500M (manufactured by Hitachi High-Tech Corporation) can be used.
The measurement method using a scanning probe microscope "JSPM-5200" (manufactured by JEOL Ltd.) is as follows. The scanning operation was performed through WinSPM Scanning, and a data analysis image of the surface shape was output. The maximum height difference Rz and the average length Rsm of the elements on the surface of the surface layer of the electrophotographic photoreceptor of the present invention were measured under the observation conditions of "JSPM-5200".
Observation conditions for "JSPM-5200" Scanner: 4
SPM Scan: All SPM Mode
Cantilever: SI-DF3P2 (manufactured by Hitachi High-Tech Fielding Corporation)
Resonance Frequency Detection:
(START) 1.00kHz
(Stop) 100 kHz (when f = 67 kHz, depends on the type of cantilever)
Cantilever Autotune: Normal approach
Acquisition: 2 Inputs (512)
Scan Mode: Normal
STM/AFM: AC-AFM
Clock: 833.33 μs
Scan Size: 3000 nm
Offset: 0
Bias [V]: 0
Reference/V: Do not change (calibration value already entered)
Filter: 1.4Hz
Loop Gain: 16
The surface shape images and the surface height data attached to the images were analyzed using WinSPM Scanning, and for the flattened images, the difference between the maximum value Zmax and the minimum value Zmin of the height z was determined as the maximum height difference Rz, and the average length Rsm of the elements was calculated.
The measurement method using a scanning probe microscope "E-sweep" (manufactured by Hitachi High-Technologies Corporation) is as follows: The measurement is performed through a scanning operation, and a data analysis image of the surface shape of the electrophotographic photosensitive member can be output.
- Observation conditions for "E-sweep" Cantilever: SI-DF20 (with aluminum on the back) K-A102002771 (manufactured by Hitachi High-Tech Fielding Corporation)
Scanning probe microscope: Hitachi High-Tech Science Corporation Measurement unit: E-sweep
Measurement mode: DFM (resonance mode) Shape image resolution: X data number 512, Y data number 512
Measurement frequency: 127Hz
The Q-curve measurement magnification, excitation voltage, low-pass filter, high-pass filter, etc. were adjusted to optimize the resonance state of the cantilever.
The surface shape image and the surface height data attached to the image are analyzed using the attached software, and for the flattened image, the difference between the maximum value Zmax and the minimum value Zmin of the height z can be calculated as the maximum height difference (maximum height) Rz based on JIS B0601:2001, and the average length Rsm of the elements can be calculated.

<Derivation of the ratio of the volume of inorganic particles to the volume of binder resin in the surface layer>
The ratio of the volume of the inorganic particles to the volume of the binder resin in the surface layer was calculated from the amount and specific gravity of the polymerizable monomer having a polymerizable functional group and the particles used in the surface layer coating liquid. The specific gravity of the polymer and the particles after polymerization of the polymerizable monomer having a polymerizable functional group can be referenced from the published values of the manufacturers of each material and the database POLYINFO of the National Institute for Materials Science.

When it is determined from an electrophotographic photosensitive member, for example, the following method can be used.
Only the surface layer is peeled off into a plurality of slices using a cutting tool, and the slices are subjected to compositional analysis such as NMR, ESI-MS, and LC-CAD/MS/MSn to identify the polymerizable monomer having a polymerizable functional group that constitutes the polymerizable monomer composition before the binder resin contained in the surface layer becomes a polymer.

In addition, another piece is subjected to thermogravimetric analysis such as TGA to measure the mass of the binder resin and inorganic particles contained in the surface layer. Furthermore, the sintered inorganic particles are subjected to composition analysis such as SEM-EDS and XRF to identify the material of the inorganic particles and obtain the specific gravity.
From these, in an electrophotographic photoreceptor having a surface layer containing a binder resin and inorganic particles, the ratio of the volume of the inorganic particles to the volume of the binder resin in the surface layer is calculated.

<Calculation of Film Thickness T of Surface Layer of Electrophotographic Photoreceptor>
The cross-section of the electrophotographic photoreceptor prepared in the examples was observed. It was judged whether the particles were laminated in a single layer in the surface layer as shown in FIG. 1, or in multiple layers as shown in FIG. 2. The samples for the cross-section observation were taken by dividing the electrophotographic photoreceptor into four equal parts in the longitudinal direction, and taking samples at positions of ¼, ½, and ¾ of the length from the end, and shifting them by 120° in the circumferential direction. Sample pieces of 5 mm square were cut out from each electrophotographic photoreceptor, and the surface layer was three-dimensionalized to 2 μm × 2 μm × 2 μm using Slice & View of FIB-SEM.

The conditions for Slice & View were as follows:
Analytical sample processing: FIB method Processing and observation equipment: SII/Zeiss NVision 40
Slice interval: 10 nm
(Observation conditions)
Acceleration voltage: 1.0 kV
Sample tilt: 54°
WD: 5mm
Detector: BSE detector Aperture: 60 μm, high current
ABC:ON
Image resolution: 1.25 nm/pixel
The measurement environment is a temperature of 23° C. and a pressure of 1×10 ⁻⁴ Pa. As the processing and observation device, a Strata 400S (sample inclination: 52°) manufactured by FEI can also be used.

The analysis area was 2 μm long x 2 μm wide, and the information for each cross section was integrated to determine the volume V per 2 μm long x 2 μm wide x 2 μm thick (8 μm ³ ) on the surface of the surface layer. Image analysis for each cross section was performed using image processing software: Image-ProPlus manufactured by MediaCybernetics. In the cross section of the surface layer of the electrophotographic photoreceptor shown in FIG. 1, the length from the interface between the charge transport layer and the surface layer to the exposed surface of the binder resin of the surface layer was taken as the film thickness of the surface layer, and the average value of each sample was adopted as the film thickness of the surface layer.

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

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

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

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

60 parts of titanium oxide particles 1 were added to this solution, which was then placed in a vertical sand mill using 120 parts of glass beads with a number-average primary particle size of 1.0 mm as a dispersion medium, and the resultant was subjected to a dispersion treatment for 4 hours under conditions of a dispersion temperature of 23±3° C. and a rotation speed of 1500 rpm (circumferential speed of 5.5 m/s) to obtain a dispersion. The glass beads were removed from this dispersion using a mesh. 0.01 parts of silicone oil (trade name: SH28PAINTADDITIVE, manufactured by Dow Corning Toray Co., Ltd.) as a leveling agent and 8 parts of silicone resin particles (trade name: KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., average primary particle size: 2 μm, density: 1.3 g/cm ³ ) as a surface roughness imparting agent were added to the dispersion after the glass beads were removed, and the mixture was stirred, followed by pressure filtration using PTFE filter paper (trade name: PF060, manufactured by Advantec Toyo Co., Ltd.) to prepare a coating solution 1 for a conductive layer.

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

A dispersion was prepared by adding 18.0 parts of rutile-type titanium oxide particles that had been surface-treated with the organosilicon compound, 4.5 parts of N-methoxymethylated nylon (product name: Toresin (registered trademark) EF-30T, manufactured by Nagase ChemteX Corporation), and 1.5 parts of copolymer nylon resin (product name: Amilan (registered trademark) CM8000, manufactured by Toray Industries, Inc.) to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol.
This dispersion was subjected to a dispersion treatment for 5 hours in a vertical sand mill using glass beads having a diameter of 1.0 mm, and the glass beads were then removed to prepare coating solution 1 for undercoat layer.

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

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

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

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

Preparation of Coating Solution 1 for Charge Transport Layer
(Example of Preparation of Charge Transport Layer 1)
Next, the following materials were prepared to prepare a mixed solvent.
Orthoxylene 25 parts by weight Methyl benzoate 25 parts by weight Dimethoxymethane 25 parts by weight Furthermore, the following materials were dissolved in the above mixed solvent to prepare a coating solution 1 for a charge transport layer.
Charge transport material (hole transport material) represented by the following structural formula (C-1): 5 parts by weight Charge transport material (hole transport material) represented by the following structural formula (C-2): 5 parts by weight Polycarbonate (product name: Iupilon (registered trademark) Z400, manufactured by Mitsubishi Engineering Plastics Corporation): 10 parts by weight This charge transport layer coating liquid 1 was dip-coated onto the charge generation layer 1 to form a coating film, and the coating film was dried at a drying temperature of 40° C. for 5 minutes to form a charge transport layer 1 having a thickness of 15 μm.

(Example 1 of Preparation of Surface Layer Containing Particles)
As inorganic particles A and inorganic particles B contained in the surface of the surface layer of the electrophotographic photoreceptor of the present invention, the materials shown in Table 1 were prepared.

The materials in Table 2 were prepared as polymerizable monomer A.

The materials in Table 3 were prepared as polymerizable monomer B.

<Preparation of Surface Layer Coating Solution 1>
Inorganic particle A ("QSG-170", manufactured by Shin-Etsu Chemical Co., Ltd.) 3.0 parts by mass Inorganic particle B ("QSG-80", manufactured by Shin-Etsu Chemical Co., Ltd.) 3.0 parts by mass Dodecyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.9 parts by mass Dipentaerythritol hexaacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)
2.4 parts by weight of siloxane-modified acrylic compound (product name: Simac (registered trademark) US270, manufactured by Toa Gosei Co., Ltd.) 0.1 parts by weight of 1-propanol 100.0 parts by weight of cyclohexane 100.0 parts by weight were mixed and stirred for 6 hours with a stirring device to prepare coating solution 1 for surface layer.

<Preparation of Surface Layer Coating Solutions 2 to 24>
Surface layer coating solutions 2 to 24 were prepared in the same manner as in preparation of surface layer coating solution 1, except that the types and amounts of inorganic particles A, inorganic particles B, and other particles were changed as shown in Table 4.

*The specific gravity of the polymerizable monomer is the specific gravity of the polymerized product after polymerization.

<Preparation of Surface Layer Coating Solution 25>
The following components were placed in a glass flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a gas inlet.
Compound represented by the following formula (3): 70 parts by mass Product mainly composed of compound represented by the following formula (4): 30 parts by mass Trifluorotoluene: 270 parts by mass Azobisisobutyronitrile: 0.35 parts by mass
Nitrogen gas was introduced into the flask containing the above components, and the mixture was reacted for 14 hours under reflux (heated to about 100° C.) The reaction liquid was poured into a 10-fold amount of methanol to cause precipitation, and then filtered.

One part of the residue was stirred in a mixed solution of 43 parts of methanol and 17 parts of ion-exchanged water at 10°C for 15 minutes, and then centrifugal filtration was performed using a polypropylene filter. 40 parts of methanol was further added to the residue, and the mixture was stirred at 10°C for 40 minutes, and then centrifugal filtration was performed using a polypropylene filter. The residue was air-dried for 8 hours or more, and then vacuum-dried at 70°C and an internal pressure of 260 mmHg or less for 3 hours using a vacuum dryer equipped with a stirrer. In this way, a resin (P-1) having a repeating structural unit derived from a compound represented by formula (4) and a repeating structural unit derived from a compound represented by formula (3) was obtained.

next,
Resin (P-1): 2.0 parts by mass, 1,1,2,2,3,3,4-heptafluorocyclopentane (product name: Zeorora H (registered trademark), manufactured by Zeon Corporation): 42 parts by mass, and 1-propanol: 48 parts by mass were mixed and dissolved.

Then, 28 parts by mass of tetrafluoroethylene resin particles (product name: Lubron L-2, manufactured by Daikin Industries, Ltd.) were added to the liquid, which was then placed in a high-pressure disperser (product name: Microfluidizer M-110EH, manufactured by Microfluidics, Inc., USA). The liquid was then passed six times at a pressure of 40 MPa to obtain a dispersion of resin particles containing fluorine atoms. The average particle size of the resin particles containing fluorine atoms in the obtained dispersion was 0.20 μm. A dispersion of resin particles containing fluorine atoms was obtained.

continue,
The following was added to the dispersion: 57.9 parts by weight of a charge transport material represented by the following formula (5): 12.0 parts by weight of trimethylolpropane triacrylate (TMPTA, manufactured by Tokyo Chemical Industry Co., Ltd.): 0.10 parts by weight of a compound represented by the following formula (6): 52 parts by weight of 1,1,2,2,3,3,4-heptafluorocyclopentane: 52 parts by weight of 1-propanol: 70 parts by weight. The dispersion was then filtered using a Polyflon filter (product name: PF-040, manufactured by Advantec Toyo Co., Ltd.) to prepare surface layer coating solution 25.

<Preparation of Surface Layer Coating Solution 26>
The following ingredients were mixed and stirred:
Compound represented by the following formula (7): 95 parts by weight Dodecyl acrylate: 5.0 parts by weight Siloxane-modified acrylic compound (BYK-3550, manufactured by BYK Japan Co., Ltd.): 3.5 parts by weight Urea compound represented by the following formula (8): 2.0 parts by weight 1-propanol: 200 parts by weight 1,1,2,2,3,3,4-heptafluorocyclopentane (product name: Zeorola H, manufactured by Zeon Corporation): 100 parts by weight The solution was then filtered using a Polyflon filter (product name: PF-020, manufactured by Advantec Toyo Co., Ltd.) to prepare a surface layer coating solution 26.

<Preparation of Surface Layer Coating Solution 27>
Inorganic particles A ("QSG-170", manufactured by Shin-Etsu Chemical Co., Ltd.) 15.0 parts by mass Compound represented by the following formula (9) (manufactured by Tokyo Chemical Industry Co., Ltd.) 3.4 parts by mass Charge transport material (hole transport material) represented by the following formula (10) 81.6 parts by mass 1-propanol 100.0 parts by mass The above ingredients were mixed and stirred for 6 hours with a stirrer to prepare surface layer coating solution 27.

<Preparation of Surface Layer Coating Solution 28>
Polymerizable monomer represented by the following formula (11): 20.0 parts by weight Dipentaerythritol hexaacrylate (KAYARAD (registered trademark) DPHA, manufactured by Nippon Kayaku Co., Ltd.): 75 parts by weight Radical polymerizable compound having a charge transport structure represented by the following formula (12): 95 parts by weight 1-hydroxy-cyclohexyl-phenyl-ketone (photopolymerization initiator Irgacure 184, manufactured by Ciba Specialty Chemicals): 10.0 parts by weight Tetrahydrofuran: 1,200 parts by weight The above ingredients were mixed and stirred for 6 hours using a stirrer to prepare surface layer coating solution 28.

<Preparation of Surface Layer Coating Solution 29>
Polymerizable monomer represented by the above formula (11) 20.0 parts by mass Trimethylolpropane triacrylate (TMPTA, manufactured by Tokyo Chemical Industry Co., Ltd.)
75.0 parts by weight of charge transport material represented by the above formula (12): 95.0 parts by weight of 1-hydroxycyclohexylphenylketone (photopolymerization initiator Irgacure 184, manufactured by Ciba Specialty Chemicals): 10.0 parts by weight of tetrahydrofuran: 1,200 parts by weight of alumina particles (AA-03, manufactured by Sumitomo Chemical Co., Ltd.): 20.0 parts by weight. The above ingredients were mixed and stirred for 6 hours using a stirrer to prepare surface layer coating solution 29.

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

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

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

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

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

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

Next, the coating was naturally cooled in the atmosphere until the temperature of the coating reached 25°C, after which it was heat-treated for 30 minutes under conditions that brought the temperature of the coating to 120°C, forming a surface layer with a thickness of 1.0 μm. The physical properties of the resulting electrophotographic photoreceptor are shown in Table 5.

<Preparation Examples of Electrophotographic Photoreceptors 2 to 24>
Electrophotographic photoreceptors 2 to 24 were produced in the same manner as in the production of electrophotographic photoreceptor 1, except that the surface layer coating liquid 1 was changed as shown in Table 5. The physical properties of the obtained electrophotographic photoreceptors 2 to 24 are shown in Table 5.

<Example of Manufacturing Electrophotographic Photoreceptor 25>
An electrophotographic photoreceptor 25 was produced in the same manner as in the production of the electrophotographic photoreceptor 1, except that the surface layer coating liquid 1 in the production of the electrophotographic photoreceptor 1 was changed to the surface layer coating liquid 25. The physical properties of the obtained electrophotographic photoreceptor 25 are shown in Table 5.

<Example of Manufacturing Electrophotographic Photoreceptor 26>
An electrophotographic photoreceptor 26 was produced in the same manner as in the production of the electrophotographic photoreceptor 1, except that in the production of the electrophotographic photoreceptor 1, the surface layer coating liquid 1 was changed to the surface layer coating liquid 26. The physical properties of the obtained electrophotographic photoreceptor 26 are shown in Table 5.

<Example of Manufacturing Electrophotographic Photoreceptor 27>
Electrophotographic photoreceptor 27 was produced in the same manner as in the production of electrophotographic photoreceptor 1, except that in the production of electrophotographic photoreceptor 1, surface layer coating liquid 1 was changed to surface layer coating liquid 27. The physical properties of the obtained electrophotographic photoreceptor 27 are shown in Table 5. The specific gravity of the binder resin was 1.2.

<Example of Manufacturing Electrophotographic Photoreceptor 28>
The electrophotographic photoreceptor 1 was produced in the same manner up to the formation of the charge transport layer, and then the surface layer coating solution 28 was applied onto the charge transport layer, followed by light irradiation using a metal halide lamp at an irradiation intensity of 500 mW/ ^cm2 for an irradiation time of 20 seconds, and then drying at 130°C for 30 minutes to produce the electrophotographic photoreceptor 28. The physical properties of the obtained electrophotographic photoreceptor 28 are shown in Table 5.

<Example of Manufacturing Electrophotographic Photoreceptor 29>
In the preparation of electrophotographic photoreceptor 1, the process up to the formation of the charge transport layer was carried out in the same manner, and then the surface layer coating liquid 29 was applied onto the charge transport layer, followed by irradiating the layer with light from a metal halide lamp under conditions of an irradiation intensity of 500 mW/ ^cm2 and an irradiation time of 20 seconds, and then drying at 130°C for 30 minutes to prepare electrophotographic photoreceptor 29. The physical properties of the obtained electrophotographic photoreceptor 29 are shown in Table 5. The specific gravity of the binder resin was 1.2.

Evaluation Methodology
<Evaluation of transferability (evaluation method 1)>
A commercially available Canon laser beam printer i-SENSYS LBP673Cdw was used, which was modified by changing the evaluation machine body and software.

Toner 1 was loaded into the toner cartridge of the evaluation machine i-SENSYS LBP673Cdw, and the toner cartridge was left for 24 hours under normal temperature and humidity conditions (25°C, 50% RH; hereinafter also referred to as N/N). After being left for 24 hours under this environment, the toner cartridge was attached to the above, and an image with a print rate of 2.0% was output in the center of the N/N environment with a margin of 50 mm on each side, up to 30 sheets of A4 paper in landscape orientation. Plain paper CS-680 (68 g/ ^m2 ) (Canon Marketing Japan Inc.) was used.

Next, a 30 mm wide full solid image was output in the vertical direction of the paper on plain paper CS-680, and the residual toner remaining on the electrophotographic photosensitive member during the formation of the solid image was taped off and collected using a transparent polyester adhesive transparent tape (polyester tape 5511, Nichiban).
The density of the residual toner was measured by the following method. The transparent tape on which the residual toner peeled off from the surface of the electrophotographic photoreceptor was collected and a new transparent tape were each attached to a high whiteness paper (GFC081 Canon). Then, the density D1 of the transparent tape on the residual toner collecting portion and the density D0 of the new transparent tape portion were measured with a reflection densitometer (Reflectometer Model TC-6DS, manufactured by Tokyo Denshoku Co., Ltd.) by setting the filter to an amber filter, which is the complementary color of cyan. The difference "D0-D1" obtained by the measurement was taken as the density of the residual toner. The smaller the value of the residual toner density, the less the residual toner. It was judged as follows. The obtained residual toner density was ranked in four stages from A to D based on the following criteria. Among the rankings, A to C were deemed to show the effect of the present invention. The evaluation results are shown in Table 3.
(Evaluation criteria)
A: Transfer residual density is less than 2.0 B: Transfer residual density is 2.0 or more and less than 4.0 C: Transfer residual density is 4.0 or more and less than 8.0 D: Transfer residual density is 8.0 or more

<Evaluation of Transferability During Durability (Evaluation Method 2)>
In the above-mentioned <Evaluation of transferability>, after the taping evaluation of the residual toner, an image with a printing rate of 2.0% was output in the center of the paper with a margin of 50 mm on each side in an N/N environment up to 5,000 sheets in the landscape direction of A4 paper, and then the residual toner was evaluated by taping in the same manner as in the above-mentioned <Evaluation of transferability>. The same evaluation criteria were also used.

<Evaluation of durability concentration transition (Evaluation method 3)>
The modified machine was placed in an environment of 30°C and 80% RH and the density transition during the durability test was evaluated. An original image in which 5 solid black patches of 20 mm square were arranged within the development area was output, and the development bias was set so that the initial reflection density was 1.3. Next, 2000 sheets of a text image with a print ratio of 1% were output. Plain paper CS-680 (68 g/m ² ) (Canon Marketing Japan Inc.) was used. Durability was evaluated by comparing the difference in density between the 5-point average density of the solid black patches and the image density after the durability test relative to the density of the initial image.
The image density was measured using a Macbeth Reflection Densitometer RD918 (manufactured by Macbeth Co.) as a relative density to the white background of the original image.
(Evaluation criteria)
A: Density difference is less than 0.10 B: Density difference is 0.10 or more and less than 0.15 C: Density difference is 0.15 or more and less than 0.20 D: Density difference is 0.20 or more

[Examples 2 to 20]
The electrophotographic photoreceptors shown in Table 5 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 6.
Comparative Examples 1 to 9
The electrophotographic photoreceptors shown in Table 5 were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 6.

The disclosure of this embodiment includes the following configuration.
(Configuration 1)
An electrophotographic photoreceptor having a surface layer containing inorganic particles and a binder resin,
the binder resin is a polymer of a polymerizable monomer composition containing a polymerizable monomer having a polymerizable functional group,
The polymerizable monomer composition contains, as the polymerizable monomer, a polymerizable monomer A represented by the following formula (1):
a ratio of the volume of the inorganic particles to the volume of the binder resin in the surface layer is 0.5 or more and 3.0 or less;
1. An electrophotographic photoreceptor comprising:
( ^R1 represents a hydrogen atom or a methyl group, and ^R2 represents a linear alkyl group having 10 to 20 carbon atoms.)
(Configuration 2)
2. The electrophotographic photoreceptor according to claim 1, wherein the inorganic particles contained in the surface layer have an average primary particle size based on the number of particles of 60 nm or more and 350 nm or less.
(Configuration 3)
3. The electrophotographic photoreceptor according to claim 1, wherein the maximum height difference Rz of the surface of the surface layer is 100 nm or more and 400 nm or less.
(Configuration 4)
4. The electrophotographic photoreceptor according to any one of configurations 1 to 3, wherein the surface layer has a surface element average length Rsm of 100 nm or more and 400 nm or less.
(Configuration 5)
at least a part of the inorganic particles contained in the surface layer is inorganic particles partially exposed from the surface of the surface layer,
the total volume of the exposed portions of the partially exposed inorganic particles is 30 vol% or more and 80 vol% or less with respect to the total volume of the inorganic particles contained in the surface layer;
5. The electrophotographic photoreceptor according to any one of Constitutions 1 to 4.
(Configuration 6)
The electrophotographic photoreceptor according to any one of Configurations 1 to 5, wherein the content of the polymerizable monomer A in the polymerizable monomer composition is 25% by mass or more with respect to the total mass of the polymerizable monomer composition.
(Configuration 7)
The electrophotographic photoreceptor according to any one of Configurations 1 to 6, wherein the polymerizable monomer composition further contains, as the polymerizable monomer, a polymerizable monomer B having 6 or more polymerizable functional groups.
(Configuration 8)
8. The electrophotographic photoreceptor according to claim 7, wherein the polymerizable monomer B is a (meth)acrylic monomer having six or more polymerizable functional groups.
(Configuration 9)
The electrophotographic photoreceptor according to the above-mentioned constitution 7 or 8, wherein the polymerizable monomer B does not have a triphenylamine skeleton.
(Configuration 10)
the surface layer contains, as the inorganic particles, inorganic particles A and inorganic particles B having different number-based average primary particle sizes,
When the number-based average primary particle diameter of the inorganic particles A is DA [nm] and the number-based average primary particle diameter of the inorganic particles B is DB [nm], the DA and the DB satisfy the following formulas (i) and (ii):
1.2≦DA/DB≦4.0 (i)
80≦DA≦350... (ii)
10. The electrophotographic photoreceptor according to any one of Constitutions 1 to 9.
(Configuration 11)
A process cartridge which integrally supports the electrophotographic photosensitive member according to any one of configurations 1 to 10 and at least one means selected from the group consisting of a charging means, a developing means and a cleaning means, and is detachably mountable to a main body of an electrophotographic apparatus.
(Configuration 12)
11. An electrophotographic apparatus comprising the electrophotographic photoreceptor according to any one of configurations 1 to 10, a charging unit, an exposure unit, a developing unit, and a transfer unit.

100 Electrophotographic apparatus a, b, c, d Image forming section 1a, 1b, 1c, 1d Electrophotographic photoreceptor 2a, 2b, 2c, 2d Charging roller
Reference Signs List 3a, 3b, 3c, 3d Exposure means 4a, 4b, 4c, 4d Development means 5a, 5b, 5c, 5d Discharging means 41a, 41b, 41c, 41d Development means 10 Intermediate transfer belt 11 Drive roller 12 Suspension roller 13 Opposed roller 14a, 14b, 14c, 14d Metal roller 15 Secondary transfer roller 17 Belt cleaning means 30 Fixing means 30 Fixing means 50 Paper feeding means P Transfer material 101 Support 102 Undercoat layer 103 Charge generating layer 104 Charge transport layer 105 Surface layer 106 Inorganic particles A
107 Inorganic particles B

Claims (12)

An electrophotographic photoreceptor having a surface layer containing inorganic particles and a binder resin,
the binder resin is a polymer of a polymerizable monomer composition containing a polymerizable monomer having a polymerizable functional group,
The polymerizable monomer composition contains, as the polymerizable monomer, a polymerizable monomer A represented by the following formula (1):
a ratio of the volume of the inorganic particles to the volume of the binder resin in the surface layer is 0.5 or more and 3.0 or less;
1. An electrophotographic photoreceptor comprising:
(In formula (1), ^R1 represents a hydrogen atom or a methyl group, and ^R2 represents a linear alkyl group having 10 to 20 carbon atoms.) The electrophotographic photoreceptor according to claim 1, wherein the maximum height difference Rz of the surface of the surface layer is 100 nm or more and 400 nm or less. The electrophotographic photoreceptor according to claim 1, wherein the average length Rsm of the surface elements of the surface layer is 100 nm or more and 400 nm or less. The electrophotographic photoreceptor according to claim 1, wherein the content of the polymerizable monomer A in the polymerizable monomer composition is 25% by mass or more based on the total mass of the polymerizable monomers contained in the polymerizable monomer composition. The electrophotographic photoreceptor according to claim 1, wherein the polymerizable monomer composition further contains, as the polymerizable monomer, a polymerizable monomer B having 6 or more polymerizable functional groups. The electrophotographic photoreceptor according to claim 5, wherein the polymerizable monomer B is a (meth)acrylic monomer having 6 or more polymerizable functional groups. The electrophotographic photoreceptor according to claim 5, wherein the polymerizable monomer B does not have a triphenylamine skeleton. at least a part of the inorganic particles contained in the surface layer is inorganic particles partially exposed from the surface of the surface layer,
the total volume of the exposed portions of the partially exposed inorganic particles is 30 vol% or more and 80 vol% or less with respect to the total volume of the inorganic particles contained in the surface layer;
The electrophotographic photoreceptor according to claim 1 . The electrophotographic photoreceptor according to claim 8, wherein the inorganic particles contained in the surface layer have an average primary particle size based on the number of particles of 60 nm or more and 350 nm or less. the surface layer contains, as the inorganic particles, inorganic particles A and inorganic particles B having different number-based average primary particle sizes,
When the number-based average primary particle diameter of the inorganic particles A is DA [nm] and the number-based average primary particle diameter of the inorganic particles B is DB [nm], the DA and the DB satisfy the following formulas (i) and (ii):
1.2≦DA/DB≦4.0 (i)
80≦DA≦350... (ii)
The electrophotographic photoreceptor according to claim 8. A process cartridge that integrally supports the electrophotographic photoreceptor according to any one of claims 1 to 10 and at least one means selected from the group consisting of a charging means, a developing means, and a cleaning means, and is detachably mountable to the main body of an electrophotographic device. An electrophotographic device having the electrophotographic photoreceptor according to any one of claims 1 to 10, as well as a charging means, an exposure means, a developing means and a transfer means.