JP2019179077A - Electrophotographic photoreceptor, process cartridge, and electrophotographic device - Google Patents

Abstract

To provide an electrophotographic photoreceptor capable of suppressing both black spots and fogging after prolonged use even at low contrast.SOLUTION: An electrophotographic photoreceptor is provided, comprising a support material, an intermediate layer formed on the support material, and a photosensitive layer formed on the intermediate layer, where the intermediate layer consists of a first intermediate layer formed on the support material and a second intermediate layer formed on the first intermediate layer, the first intermediate layer containing titanium oxide particles doped with niobium or tantalum.SELECTED DRAWING: None

Description

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

In recent years, research and development of electrophotographic photoreceptors (organic electrophotographic photoreceptors) using organic photoconductive materials have been actively conducted.
The electrophotographic photoreceptor is basically composed of a support and a photosensitive layer formed on the support. However, the present situation is that the support and photosensitive layer are exposed in order to conceal defects on the surface of the support, protect against electrical breakdown of the photosensitive layer, improve chargeability, and improve the charge injection prevention property from the support to the photosensitive layer. Various layers are often provided between the layers.

  Among the layers provided between the support and the photosensitive layer, a technique of providing an intermediate layer is known for the purpose of solving the problems of image defects such as stabilization of charging potential and black spots. In addition, a technique in which metal oxide particles such as titanium oxide are dispersed in a resin in an intermediate layer is also known, and Patent Document 1 discloses an electrophotographic photoreceptor using titanium oxide doped with niobium as an intermediate layer. Has been.

  In general, since the intermediate layer has higher conductivity than a layer that does not contain metal oxide particles, the residual potential during image formation is less likely to increase, and the dark portion potential and the light portion potential are less likely to vary. Further, by providing such an intermediate layer between the support and the photosensitive layer to conceal defects on the surface of the support, the tolerance for defects on the surface of the support is increased. As a result, since the allowable use range of the support is greatly expanded, there is an advantage that the productivity of the electrophotographic photosensitive member can be improved.

JP 2005-17470 A

According to the study by the present inventors, the electrophotographic photosensitive member described in Patent Document 1 is excellent in environmental stability, but if the latent image contrast is not increased with long-term use, the occurrence of fogging is suppressed. There is a problem that it is difficult to achieve both the suppression of black spots and the occurrence of black spots. The latent image contrast means a difference between the bright part potential and the dark part potential on the photosensitive drum.
Accordingly, an object of the present invention is to provide an electrophotographic process capable of suppressing the occurrence of black spots and the occurrence of fog even when used for a long period of time or at a low contrast (low latent image contrast). The object is to provide a photoreceptor.

The above object is achieved by the present invention described below. That is, according to one aspect of the present invention, there is provided an electrophotographic photosensitive member having a support, an intermediate layer formed on the support, and a photosensitive layer formed on the intermediate layer,
The intermediate layer comprises a first intermediate layer formed on the support and a second intermediate layer formed on the first intermediate layer,
An electrophotographic photoreceptor is provided in which the first intermediate layer contains titanium oxide particles doped with niobium or tantalum.

  According to the present invention, it is possible to provide an electrophotographic photosensitive member that can achieve both suppression of occurrence of black spots and suppression of occurrence of fog even with low contrast through long-term use.

1 is a diagram illustrating an example of a schematic configuration of an electrophotographic apparatus having a process cartridge including an electrophotographic photosensitive member.

Hereinafter, the present invention will be described in detail with reference to preferred embodiments.
Although the detailed mechanism has not been clarified by the present inventors, the intermediate layer has a two-layer structure, and the first intermediate layer immediately above the support contains titanium oxide doped with niobium. As a result, the present inventors have found that the above problems are greatly improved.

[Electrophotographic photoconductor]
In the electrophotographic photoreceptor according to the present invention, the first intermediate layer, the second intermediate layer, and the photosensitive layer are formed in this order on at least the support, and the first intermediate layer is doped with niobium. Titanium oxide is contained.
Examples of the method for producing the electrophotographic photoreceptor according to the present invention include a method in which a coating solution for each layer described later is prepared, applied in the order of desired layers, and dried. At this time, examples of the coating method of the coating liquid include dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, dip coating is preferable from the viewpoints of efficiency and productivity.
Hereinafter, each layer will be described.

<Support>
In the present invention, the electrophotographic photosensitive member has a support. In the present invention, the support is preferably a conductive support having conductivity. Moreover, examples of the shape of the support include a cylindrical shape, a belt shape, and a sheet shape. Among these, a cylindrical support is preferable. Further, the surface of the support may be subjected to electrochemical treatment such as anodic oxidation, blast treatment, centerless polishing treatment, cutting treatment or the like.

As the material for the support, metal, resin, glass and the like are preferable.
Examples of the metal include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among these, an aluminum support using aluminum is preferable.
In addition, the conductivity may be imparted to the resin or glass by a treatment such as mixing or covering with a conductive material.

<First intermediate layer>
In the present invention, a first intermediate layer is provided on the support. By providing the first intermediate layer, it is possible to conceal scratches and irregularities on the surface of the support, and to control the reflection of light on the surface of the support. The first intermediate layer includes titanium oxide particles, And a binder resin.
The titanium oxide particles contained in the first intermediate layer are doped with niobium or tantalum. By doping niobium or tantalum, high conductivity can be obtained, and a first intermediate layer having good conductivity can be obtained.

  As the titanium oxide particles according to the present invention, particles having various shapes such as a sphere, a polyhedron, an ellipsoid, a flake, and a needle can be used. Among these, spherical, polyhedral, and ellipsoidal ones are preferable from the viewpoint that there are few image defects such as black spots. More preferably, the titanium oxide particles according to the present invention have a spherical shape or a polyhedral shape close to a spherical shape. The titanium oxide particles according to the present invention are preferably made of anatase type or rutile type titanium oxide, and more preferably made of anatase type titanium oxide. By using anatase type titanium oxide, fluctuations in dark part potential and bright part potential are less likely to occur.

  The number average particle size (hereinafter also referred to as average primary particle size) of the primary particles of the titanium oxide particles is preferably 50 nm or more and 500 nm or less. If the average primary particle diameter of the titanium oxide particles is 50 nm or more, the titanium oxide particles are less likely to reaggregate after the first intermediate layer coating solution is prepared. If re-aggregation of the titanium oxide particles occurs, the stability of the first intermediate layer coating solution is lowered, and cracks are likely to occur on the surface of the formed first intermediate layer. When the average primary particle size of the titanium oxide particles is 500 nm or less, the surface of the first intermediate layer is hardly roughened. If the surface of the first intermediate layer is rough, local charge injection to the photosensitive layer is likely to occur, and black spots (black spots) on the white background of the output image are easily noticeable. The average primary particle size of the titanium oxide particles is more preferably 100 nm or more and 400 nm or less.

The doping amount of niobium or tantalum in titanium oxide is preferably 0.5% by mass or more and 10% by mass or less of the total mass of the titanium oxide. When the doping amount is 0.5% by mass or more, an effect of suppressing fluctuations in dark part potential and bright part potential is easily obtained. In addition, when the doping amount is 10% by mass or less, leakage is likely to occur in the electrophotographic photosensitive member. The dope amount is more preferably 1% by mass or more and 7% by mass or less of the total mass of the titanium oxide.
The surface of the titanium oxide particles may be treated with a silane coupling agent or the like.

  The first intermediate layer preferably contains 20% by volume or more and 50% by volume or less of titanium oxide particles with respect to the total volume of the first intermediate layer. If the content of titanium oxide particles in the first intermediate layer is 20% by volume or more with respect to the total volume of the first intermediate layer, the distance between the titanium oxide particles is unlikely to increase. If the distance between the titanium oxide particles is difficult to be increased, the volume resistivity of the first intermediate layer is difficult to increase. As a result, the flow of charges is less likely to be stagnated during image formation, the residual potential is less likely to rise, and there is a tendency that fluctuations in the dark part potential and the bright part potential are less likely to occur. If content of the titanium oxide particle in a 1st intermediate | middle layer is 50 volume% or less with respect to the whole volume of a 1st intermediate | middle layer, it will become difficult for titanium oxide particles to contact | connect. Titanium oxide particles are less likely to be in contact with each other, and a portion having a low volume resistivity of the first intermediate layer is less likely to occur locally, and leakage is less likely to occur in the electrophotographic photosensitive member. More preferably, the first intermediate layer contains 30% by volume or more and 45% by volume or less of titanium oxide particles with respect to the total volume of the first intermediate layer.

The first intermediate layer may further include another conductive particle. Examples of another conductive particle material include metal oxide, metal, and carbon black.
Examples of the metal oxide include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of the metal include aluminum, nickel, iron, nichrome, copper, zinc, silver and the like.

When using metal oxide particles as another conductive particle, the surface of the metal oxide particles may be treated with a silane coupling agent or the like, or an element such as phosphorus or aluminum or its oxide may be doped into the metal oxide particles. May be.
Moreover, another electroconductive particle is good also as a laminated structure which has core material particle | grains and the coating layer which coat | covers the particle | grains. Examples of the core material particles include titanium oxide, barium sulfate, and zinc oxide. Examples of the coating layer include metal oxides such as tin oxide.
When a metal oxide is used as the conductive particles other than titanium oxide, the volume average particle diameter is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

  Examples of the binder resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, alkyd resin, and the like. As the binder resin, a thermosetting phenol resin or a thermosetting polyurethane resin is preferable. When a curable resin is used as the first intermediate layer binder resin, the binder resin contained in the first intermediate layer coating solution is a monomer and / or oligomer of the curable resin.

The first intermediate layer may further contain a masking agent such as silicone oil, resin particles, and titanium oxide.
The average film thickness of the first intermediate layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less.
The first intermediate layer can be formed by preparing a coating solution for the first intermediate layer containing the above-described materials and solvent, forming a coating film of the coating solution, and drying it. Examples of the solvent used for the coating solution include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Examples of the dispersion method for dispersing the conductive particles in the first intermediate layer coating solution include a method using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

<Second intermediate layer>
In the present invention, a second intermediate layer is provided on the first intermediate layer. By providing the second intermediate layer, the adhesion function between the layers is enhanced, and a charge injection blocking function can be provided.
The second intermediate layer preferably contains a resin. Moreover, you may form a 2nd intermediate | middle layer as a cured film by superposing | polymerizing the composition containing the monomer which has a polymerizable functional group.
The following are mentioned as resin. Polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl phenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin , Polyimide resin, polyamideimide resin, cellulose resin, etc.

The following are mentioned as a polymerizable functional group which the monomer which has a polymerizable functional group has. Isocyanate groups, blocked isocyanate groups, methylol groups, alkylated methylol groups, epoxy groups, metal alkoxide groups, hydroxyl groups, amino groups, carboxyl groups, thiol groups, carboxylic acid anhydride groups, carbon-carbon double bond groups, and the like.
The second intermediate layer may further contain an electron transport material, metal oxide particles, metal particles, a conductive polymer, and the like for the purpose of improving electrical characteristics. Among these, it is preferable to use an electron transport material and metal oxide particles.

  Examples of the electron transport material include the following. Quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, halogenated aryl compounds, silole compounds, boron-containing compounds, and the like. A second intermediate layer may be formed as a cured film by using an electron transport material having a polymerizable functional group as the electron transport material and copolymerizing with the monomer having the polymerizable functional group described above.

Examples of the metal oxide particles include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide. Examples of the metal particles include gold, silver, and aluminum. When using a metal oxide or metal particles for the second intermediate layer, the surface may be treated with a silane coupling agent or the like.
The second intermediate layer may further contain an additive.

The average film thickness of the second intermediate layer is preferably from 0.1 μm to 50 μm, more preferably from 0.2 μm to 40 μm, and particularly preferably from 0.3 μm to 30 μm.
The second intermediate layer is formed by preparing a coating solution for the second intermediate layer containing each of the above materials and solvent, forming a coating film of the coating solution, and drying and / or curing the coating solution. Can do. Examples of the solvent used for the coating solution include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

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

(1) Laminated Photosensitive Layer The laminated photosensitive layer has a charge generation 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 generation material include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferable. Among the phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferable.

The content of the charge generation material in the charge generation layer is preferably 40% by mass to 85% by mass and more preferably 60% by mass to 80% by mass with respect to the total mass of the charge generation layer. preferable.
The following are mentioned as resin. 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 generation layer may further contain additives such as an antioxidant and an ultraviolet absorber. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.
The average film thickness of the charge generation layer is preferably from 0.1 μm to 1 μm, and more preferably from 0.15 μm to 0.4 μm.
The charge generation layer can be formed by preparing a coating solution for the charge generation layer containing the above-described materials and solvent, forming a coating film of the coating solution, and drying it. Examples of the solvent used for the coating solution include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

(1-2) Charge Transport Layer The charge transport layer preferably contains a charge transport material and a resin.
Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these materials. It is done.
Moreover, the charge transport material may contain a plurality of types. Specific examples of the charge transport material are shown below.

The content of the charge transport material in the charge transport layer is preferably 20% by mass to 60% by mass and more preferably 30% by mass to 50% by mass with respect to the total mass of the charge transport layer. preferable.
Examples of the resin include polyester resin, polycarbonate resin, acrylic resin, and polystyrene resin. Among these, polycarbonate resin and polyester resin are preferable. As the polyester resin, polyarylate resin is particularly preferable.

The content ratio (mass ratio) between the charge transport material and the resin is preferably 4:10 to 20:10, and more preferably 5:10 to 12:10.
Examples of the polycarbonate resin include resins having a structural unit represented by the general formula (PC-I).

(In General Formula (PC-I), X ¹⁰¹ represents a single bond or a divalent group. R ^{101 to} R ¹⁰⁴ each independently represents a hydrogen atom, an alkyl group, or an aryl group.)
Specific examples of the structural unit represented by the general formula (PC-I) are shown below.

  Examples of the polyester resin include resins having structural units represented by general formula (PE-II) and general formula (PE-III).

(In General Formula (PE-II), X ²⁰¹ represents a single bond or a divalent group. R ^{201 to} R ²⁰⁸ each independently represents a hydrogen atom, an alkyl group, or an aryl group.)
(In General Formula (PE-III), X ³⁰¹ represents a divalent group.)
Specific examples of the structural unit represented by the general formula (PE-II) are shown below.

  Specific examples of the structural unit represented by the general formula (PE-III) are shown below.

In the present invention, the copolymer form of the polycarbonate resin and the polyester resin may be any form such as block copolymerization, random copolymerization, and alternating copolymerization.
The charge transport layer may use other resins as the binder resin in addition to the polyester resin. Examples include polycarbonate resin, siloxane resin, polymethacrylate resin, polysulfone resin, polystyrene resin, and the like. Other resins may be blended or copolymerized.

  Further, the charge transport layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a slipperiness imparting agent, and an abrasion resistance improving agent. Specifically, hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oil, fluorine resin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles Etc.

The average film thickness of the charge transport layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.
The charge transport layer can be formed by preparing a coating solution for a charge transport layer containing the above-mentioned materials and solvent, forming this coating film, and drying it. As the solvent used in the coating solution, the solvent used in the coating solution for forming the charge transport layer is an alcohol solvent, a sulfoxide solvent, a ketone solvent, an ether solvent, an ester solvent, an aromatic hydrocarbon solvent, or the like. Is mentioned.
The average film thickness of the charge transport layer is preferably 5 μm or more and 50 μm or less, and more preferably 8 μm or more and 40 μm or less.

(2) Single-layer type photosensitive layer A single-layer type photosensitive layer is formed by preparing a coating solution for a photosensitive layer containing a charge generating substance, a charge transporting substance, a resin and a solvent, forming this coating film, and drying it. can do. Examples of the charge generating substance, the charge transporting substance, and the resin are the same as those exemplified in the above-mentioned “(1) Multilayer type photosensitive layer”.

<Protective layer>
In the present invention, a protective layer may be provided on the photosensitive layer. By providing the protective layer, durability can be improved.
The protective layer preferably contains conductive particles and / or a charge transport material and a resin.
Examples of the conductive particles include metal oxide particles such as titanium oxide, zinc oxide, tin oxide, and indium oxide.

Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these materials. Among these, a triarylamine compound and a benzidine compound are preferable.
Examples of the resin include polyester resin, acrylic resin, phenoxy resin, polycarbonate resin, polystyrene resin, phenol resin, melamine resin, and epoxy resin. Among these, polycarbonate resin, polyester resin, and acrylic resin are preferable.

  Further, the protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the reaction at that time include a thermal polymerization reaction, a photopolymerization reaction, and a radiation polymerization reaction. Examples of the polymerizable functional group possessed by the monomer having a polymerizable functional group include an acryl group and a methacryl group. As the monomer having a polymerizable functional group, a material having a charge transporting ability may be used.

  The protective layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a slipperiness imparting agent, and an abrasion resistance improver. Specifically, hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oil, fluorine resin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles Etc.

The average film thickness of the protective layer is preferably 0.5 μm or more and 10 μm or less, and preferably 1 μm or more and 7 μm or less.
The protective layer can be formed by preparing a coating liquid for the protective layer containing each of the above materials and solvent, forming this coating film, and drying and / or curing it. Examples of the solvent used for the coating solution include alcohol solvents, ketone solvents, ether solvents, sulfoxide solvents, ester solvents, and aromatic hydrocarbon solvents.

[Process cartridge, electrophotographic equipment]
The process cartridge according to the present invention integrally supports the electrophotographic photosensitive member described so far and at least one means selected from the group consisting of a charging means, a developing means, a transfer means, and a cleaning means. It is detachable from the main body.
The electrophotographic apparatus according to the present invention includes the electrophotographic photosensitive member, the charging unit, the exposing unit, the developing unit, and the transferring unit described so far.

FIG. 1 shows an example of a schematic configuration of an electrophotographic apparatus having a process cartridge provided with an electrophotographic photosensitive member.
The cylindrical electrophotographic photosensitive member 1 is rotationally driven at a predetermined peripheral speed in the direction of the arrow about the shaft 2. The surface of the electrophotographic photoreceptor 1 is charged to a positive or negative predetermined potential by the charging unit 3. In the drawing, a roller charging method using a roller-type charging member is shown, but a charging method such as a corona charging method, a proximity charging method, and an injection charging method may be adopted. The surface of the charged electrophotographic photosensitive member 1 is irradiated with exposure light 4 from an exposure means (not shown), and an electrostatic latent image corresponding to target image information is formed. The electrostatic latent image formed on the surface of the electrophotographic photosensitive member 1 is developed with toner accommodated in the developing means 5, and a toner image is formed on the surface of the electrophotographic photosensitive member 1.

The toner image formed on the surface of the electrophotographic photoreceptor 1 is transferred to the transfer material 7 by the transfer means 6. The transfer material 7 onto which the toner image has been transferred is conveyed to the fixing means 8, undergoes a toner image fixing process, and is printed out of the electrophotographic apparatus. The electrophotographic apparatus may have a cleaning unit 9 for removing deposits such as toner remaining on the surface of the electrophotographic photosensitive member 1 after transfer. Further, a so-called cleaner-less system may be used in which the above deposits are removed by a developing unit or the like without separately providing a cleaning unit. The electrophotographic apparatus may have a static elimination mechanism that neutralizes the surface of the electrophotographic photosensitive member 1 with pre-exposure light 10 from pre-exposure means (not shown). Further, in order to attach and detach the process cartridge according to the present invention to and from the electrophotographic apparatus main body, a guide means 12 such as a rail may be provided.
The electrophotographic photosensitive member according to the present invention can be used in a laser beam printer, an LED printer, a copying machine, a facsimile, a complex machine of these, and the like.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples as long as the gist thereof is not exceeded. In the description of the following examples, “part” is based on mass unless otherwise specified.

[Production example of titanium oxide particles]
Titanium oxide particles doped with niobium were produced by the following method.
(Production example of titanium oxide particles 1)
The titanium oxide particles according to the present invention can be produced by a known sulfuric acid method. This is specifically shown below. To the titanyl sulfate aqueous solution, niobium sulfate (water-soluble niobium compound) was added in an amount of 1.0% by mass as niobium ions with respect to the amount of titanium (in terms of titanium dioxide). A fine particle nucleus made of titanium hydroxide was added to this aqueous solution of titanyl sulfate, followed by hydrolysis by heating to obtain a hydrous titanium dioxide slurry.
The hydrous titanium dioxide slurry containing the niobium ions was filtered, washed and dried at 110 ° C. for 8 hours. This dried product was heat-treated at 800 ° C. for 1 hour in an air atmosphere to obtain a powder of titanium oxide particles 1 having an average primary particle size of 220 nm.

(Production example of titanium oxide particles 2 to 9)
As shown in Table 1, by adjusting the amount of niobium sulfate added to the titanyl sulfate aqueous solution, the size of the fine particle nucleus added during hydrolysis, the temperature during hydrolysis, and the hydrolysis rate in the production of titanium oxide particles 1 The powder of the titanium oxide particles 2-9 was obtained. The dope amounts in Table 1 were determined by measurement by elemental analysis (XRF) using fluorescent X-rays.

(Production example of titanium oxide particles 10)
Titanium oxide particles 10 were obtained in the same manner as the production method of titanium oxide particles 1 except that tantalum chloride was added as a tantalum ion instead of niobium sulfate to 1.0% by mass of titanyl sulfate aqueous solution.

(Production example of titanium oxide particles 11)
100 parts of the resulting powder of titanium oxide particles 1 was mixed with 500 parts of toluene with stirring, and N-2- (aminoethyl) -3-aminopropyltrimethoxysilane (trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.). Of 1.25 parts was added and stirred for 2 hours. Then, toluene was distilled off under reduced pressure and baked at a temperature of 120 ° C. for 3 hours to obtain titanium oxide particles 11 surface-treated with a silane coupling agent.

[Example of preparation of first intermediate layer coating solution]
(Example of preparation of first intermediate layer coating solution 1)
50 parts of the following phenol resin as a binder material was dissolved in 35 parts of 1-methoxy-2-propanol as a solvent to obtain a solution.
Phenol resin (monomer / oligomer of phenol resin) (trade name: Pryorphen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g / cm ² )
63 parts of titanium oxide particles 1 were added to this solution, and this was placed in a vertical sand mill using 120 parts of glass beads having a number average particle diameter of 1.0 mm as a dispersion medium, and the dispersion temperature was 23 ± 3 ° C. and the rotation speed was 1500 rpm ( A dispersion was obtained by carrying out a dispersion treatment for 4 hours under the condition of a peripheral speed of 5.5 m / s. The glass beads were removed from the dispersion with a mesh.

The following materials are added to the dispersion after the glass beads are removed, and the mixture is stirred and pressure filtered using PTFE filter paper (trade name: PF060, manufactured by Advantech Toyo Co., Ltd.). Layer coating solution 1 was prepared.
Silicone oil as a leveling agent (trade name: SH28 PAINT ADDITIVE, manufactured by Toray Dow Corning Co., Ltd.) 0.01 part Silicone resin particles as a surface roughness imparting material (trade name: Tospearl 120, manufactured by Momentive Performance Materials, Number average particle diameter: 2 μm, density: 1.3 g / cm ² ) 10 parts

(Preparation examples of first intermediate layer coating solutions 2 to 13)
Preparation example of first intermediate layer coating solution 1 except that the types and amounts (parts) of titanium oxide particles used in the preparation of the first intermediate layer coating solution are as shown in Table 2. First intermediate coating solutions 2 to 13 were prepared in the same manner as described above.

(Example of preparation of first intermediate layer coating solution 14)
The following materials were dissolved in a mixed solvent of 45 parts of methyl ethyl ketone / 1 85 parts of 1-butanol to obtain a solution.
Butyral resin as a binder (trade name: BM-1, manufactured by Sekisui Chemical Co., Ltd.) 15 parts Blocked isocyanate resin (trade name: TPA-B80E, 80% solution, manufactured by Asahi Kasei) 18.75 parts 63 parts of titanium oxide particles 1 were added to this solution, and this was placed in a vertical sand mill using 120 parts of glass beads having a number average particle diameter of 1.0 mm as a dispersion medium, and the dispersion temperature was 23 ± 3 ° C. and the rotation speed was 1500 rpm ( A dispersion was obtained by carrying out a dispersion treatment for 4 hours under the condition of a peripheral speed of 5.5 m / s. The glass beads were removed from the dispersion with a mesh.

The following materials are added to the dispersion after the glass beads are removed, and the mixture is stirred and pressure filtered using PTFE filter paper (trade name: PF060, manufactured by Advantech Toyo Co., Ltd.). A layer coating solution 14 was prepared.
Silicone oil as a leveling agent (trade name: SH28 PAINT ADDITIVE, manufactured by Toray Dow Corning Co., Ltd.) 0.01 part Cross-linked polymethyl methacrylate (PMMA) particles (trade name: Techpolymer SSX- as a surface roughness imparting material) 102, manufactured by Sekisui Plastics Co., Ltd., average primary particle size: 2.5 μm) 5 parts

[Production example of polycarbonate resin]
<Polycarbonate resin (1)>
53.0 g (0.196 mol) of 2,2-bis (4-hydroxyphenyl) -4-methylpentane (manufactured by Tokyo Chemical Industry Co., Ltd., product code D3267) was added to 1100 mL of a 5% by mass aqueous sodium hydroxide solution. Then, 0.1 g of hydrosulfite was dissolved. To this, 500 mL of methylene chloride was added and stirred. While maintaining the temperature at 15 ° C., 60 g of phosgene was blown in over 60 minutes.
After completion of phosgene blowing, 1 g of p-tert-butylphenol (manufactured by Tokyo Chemical Industry Co., Ltd., product code B0383) was added as a molecular weight regulator and stirred to emulsify the reaction solution. After emulsification, 0.3 mL of triethylamine was added, and the mixture was stirred at a temperature of 23 ° C. for 1 hour for polymerization.

  After completion of the polymerization, the reaction solution was separated into an aqueous phase and an organic phase, the organic phase was neutralized with phosphoric acid, and washing with water was repeated until the conductivity of the washing solution (aqueous phase) became 10 μS / cm or less. The obtained polymer solution was dropped into warm water maintained at a temperature of 45 ° C., and the solvent was removed by evaporation to obtain a white powdery precipitate. The obtained precipitate was filtered and dried at a temperature of 110 ° C. for 24 hours to obtain a polycarbonate resin (1) having a structural unit represented by the formula (PC-I-11).

<Polycarbonate resin (2), (3)>
In the production example of the polycarbonate resin (1), the polycarbonate resins (2) and (3) having the molar ratio of the structural unit represented by the general formula (I) as shown in Table 3 by changing the molar amount of the raw material to be used )

[Production example of polyester resin]
<Polyester resin (1)>
An acid halide solution was prepared by dissolving 59 g of a dicarboxylic acid halide represented by the following formula (C-1) in dichloromethane.

また、別途、下記式（Ｃ−２）で示されるジオール２４．２ｇ、

Separately, 24.2 g of a diol represented by the following formula (C-2),

下記式（Ｃ−３）で示されるジオール２７ｇ

27 g of diol represented by the following formula (C-3)

を１０％水酸化ナトリウム水溶液に溶解させ、重合触媒としてトリブチルベンジルアンモニウムクロライドを添加して攪拌し、ジオール化合物溶液を調製した。

Was dissolved in a 10% aqueous sodium hydroxide solution, and tributylbenzylammonium chloride was added as a polymerization catalyst and stirred to prepare a diol compound solution.

Next, the acid halide solution was added to the diol compound solution with stirring to initiate polymerization. The polymerization was carried out for 3 hours while maintaining the reaction temperature at 25 ° C. or lower and stirring.
P-tert-butylphenol was added as a polymerization regulator during the polymerization reaction. Thereafter, the polymerization reaction was terminated by the addition of acetic acid, and washing with water was repeated until the aqueous phase became neutral.
After washing, the dichloromethane solution was dropped into methanol with stirring to precipitate a polymer, and this polymer was dried under reduced pressure to obtain 72.3 g of a polyester resin (1).

The obtained polyester resin (1)
Among the structural units represented by the formula (PE-III), the structural unit represented by the formula (PE-III-3) is 100 mol%,
In the structural unit represented by the formula (PE-II), the structural unit represented by the formula (PE-II-12) is 50 mol%, and the structural unit represented by the formula (PE-II-16) is 50 mol%. It was a polyester resin. Moreover, the weight average molecular weight of the obtained polyester resin (1) was 100,000.

<Polyester resins (2), (3)>
In the production example of polyester resin (1), the types and molar amounts of raw materials used were changed to obtain polyester resins (2) and (3) having the molar ratio of structural units as shown in Table 4.

<Example of production of electrophotographic photoreceptor>
(Example of production of electrophotographic photoreceptor 1)
[Support]
An aluminum cylinder (JIS-A3003, aluminum alloy) having a length of 257 mm and a diameter of 24 mm manufactured by a manufacturing method including an extrusion process and a drawing process was used as a support.

[First intermediate layer]
Under normal temperature and normal humidity (temperature 23 ° C / relative humidity 50%) environment, the first intermediate layer coating solution 1 is dip-coated on the support, and the resulting coating film is dried for 30 minutes at a temperature of 170 ° C. And the 1st intermediate | middle layer whose film thickness is 30 micrometers was formed by making it thermoset.

[Second intermediate layer]
Next, a second intermediate layer coating solution was prepared by dissolving the following materials in a mixed solvent of 65 parts of methanol / 30 parts of n-butanol.
N-methoxymethylated nylon (trade name: Toresin EF-30T, manufactured by Nagase ChemteX Corp.) 4.5 parts Copolymer nylon resin (trade name: Amilan CM8000, manufactured by Toray) 1.5 parts This second intermediate The coating solution for layers was dip-coated on the first intermediate layer, and the obtained coating film was dried at a temperature of 70 ° C. for 6 minutes to form a second intermediate layer having a thickness of 0.85 μm. .

[Charge generation layer]
Next, the following materials are put in a sand mill using glass beads having a diameter of 0.8 mm, and dispersion treatment is performed under the condition of dispersion treatment time: 3 hours. Next, 250 parts of ethyl acetate is added to generate charges. A layer coating solution was prepared.
Strong peaks at 7.5 °, 9.9 °, 16.3 °, 18.6 °, 25.1 ° and 28.3 ° of the Bragg angle (2θ ± 0.2 °) in CuKα characteristic X-ray diffraction Crystal part of hydroxygallium phthalocyanine crystal (charge generation material) 10 parts Polyvinyl butyral (trade name: ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd.) 5 parts Cyclohexanone 250 parts A charge generation layer having a thickness of 0.15 μm was formed by dip-coating on the intermediate layer and drying the resulting coating film at a temperature of 100 ° C. for 10 minutes.

[Charge transport layer]
Next, the following materials were dissolved in a mixed solution of 15 parts of orthoxylene and 25 parts of methyl benzoate to obtain a dispersion.
Compound represented by formula (CTM-1) (charge transporting substance) 9 parts Compound represented by formula (CTM-2) (charge transporting substance) 1 part Next, the following materials were added to the dispersion, and a charge transporting layer was added. A coating solution was prepared.
Polyester resin (3) synthesized in production example of polyester resin 10 parts Resin having a structural unit represented by the following formula (S-1) (viscosity average molecular weight 23,500) 0.5 part Dimethoxymethane 33 parts For this charge transport layer The coating solution was dip-coated on the charge generation layer to form a coating film. The obtained coating film is dried at a temperature of 130 ° C. for 30 minutes to form a charge transport layer (surface layer) having a film thickness of 18.0 μm, and the electrophotographic photoreceptor 1 in which the charge transport layer is the surface layer is produced. did.

（式（Ｓ−１）中、ａ：ｂは［ ］内の構造単位のモル比率を示す。ｃは（ ）内の構造単位の繰り返し数の平均値を示し、ｃ＝２０である。）

(In formula (S-1), a: b represents the molar ratio of the structural units in []. C represents the average number of repeating structural units in (), and c = 20.)

(Production example of electrophotographic photosensitive member 2, 3, 30, 31)
Except for changing the film thickness of the first intermediate layer as shown in Table 5, electrophotographic photoconductors 2, 3, and 3 in which the charge transport layer is a surface layer are the same as in the production example of electrophotographic photoconductor 1. 30, 31 were produced.

(Examples of production of electrophotographic photoreceptors 4 to 29 and 32 to 34)
The first intermediate layer coating solution 1 used in the production of the electrophotographic photosensitive member is changed from the first intermediate layer coating solution 1 to the first intermediate layer coating solutions 2 to 14 as shown in Table 5. changed. Furthermore, except that the film thickness of the first intermediate layer was changed as shown in Table 5, in the same manner as in the production example of the electrophotographic photosensitive member 1, the electrophotographic photosensitive member 4 to 4 in which the charge transport layer is a surface layer. 29, 32-34 were produced.

(Electrophotographic photoreceptor 35)
An electrophotographic photoreceptor 35 was produced in the same manner as in the production example of the electrophotographic photoreceptor 1 except that the charge transport layer was formed as shown below.

[Formation of Charge Transport Layer of Electrophotographic Photoreceptor 35]
The following materials are dissolved in a mixed solution of 15 parts of orthoxylene and 25 parts of methyl benzoate, and 0.5 parts of silica (RX50, manufactured by Nippon Aerosil Co., Ltd.) surface-treated with hexamethyldisilazane is added and subjected to ultrasonic waves. Dispersion was performed for 1 hour with a disperser to obtain a dispersion.
9 parts of the compound represented by the formula (CTM-1) 1 part of the compound represented by the formula (CTM-2) Next, the following materials were added to the dispersion to prepare a coating solution for a charge transport layer.
Polyester resin (2) synthesized in the production example of polyester resin 10 parts Resin of the structural unit represented by the above formula (S-1) (viscosity average molecular weight 23,500) 0.5 part Dimethoxymethane 33 parts For this charge transport layer A coating liquid is formed by dip-coating the coating solution on the charge generation layer, and the resulting coating film is dried at a temperature of 130 ° C. for 30 minutes, whereby a charge transport layer (surface layer) having a thickness of 18.0 μm is obtained. ) Was formed.

(Electrophotographic photoreceptors 36 to 45)
The electrophotographic photoreceptors 36 to 45 were produced in the same manner as in the production example of the electrophotographic photoreceptor 1 except that the charge transport material, the polycarbonate resin or the polyester resin, and the additives were changed as shown in Table 6.

  In Table 6 above, (S-2) is a resin having a structure represented by the following formula (viscosity average molecular weight 20,000).

（式（Ｓ−２）中、ａ：ｂは［ ］内の構造単位のモル比率を示す。ｃは（ ）内の構造単位の繰り返し数の平均値を示し、ｃ＝４０である。ｄは（ ）内の構造単位の繰り返し数の平均値を示し、ｄ＝４０である。）
上記の表６において、（Ｓ−３）は、シリコーンアクリル変性グラフトポリマー（サイマックスＧＳ−１０１、東亞合成（株）製）である。

(In formula (S-2), a: b represents the molar ratio of the structural units in []. C represents the average number of repeating structural units in (), and c = 40. (Indicates the average number of repeating structural units in parentheses, d = 40.)
In Table 6 above, (S-3) is a silicone acrylic modified graft polymer (Cymax GS-101, manufactured by Toagosei Co., Ltd.).

(Electrophotographic photoreceptor 46)
An electrophotographic photoreceptor 46 was produced in the same manner as in the production example of the electrophotographic photoreceptor 1 except that the following cutting tube was used as a support.
An aluminum cylinder (JIS-A3003, aluminum alloy) having a length of 257 mm and a diameter of 30 mm was mounted on the lathe. Then, with a diamond sintered tool, cutting was performed so that the outer diameter was 30.0 ± 0.02 mm, the runout accuracy was 15 μm, and the surface ten-point average roughness Rzjis = 0.2 μm. At this time, the spindle rotation speed was 3,000 rpm, the bite feed rate was 0.3 mm / rev, and the machining time was 24 seconds except for the attachment and detachment of the workpiece.

(Electrophotographic photoreceptor 47)
An electrophotographic photoreceptor 47 was produced by forming a protective layer on the electrophotographic photoreceptor 1 by the method described below.
[Formation of protective layer of electrophotographic photoreceptor 47]
First, a product containing a compound represented by the following formula (a-1) as a main component was obtained by the method described in “Synthesis Example (E-3)” of JP-A-2009-104145.

続いて、特開２００９−１０４１４５号公報の「製造例（Ａ−１）」に記載の方法で、下記式（ｂ−１）で示される化合物を得た。下記式（ｂ−１）中の８０は繰り返し構造単位の繰り返し回数の平均値を示す。

Subsequently, a compound represented by the following formula (b-1) was obtained by the method described in “Production Example (A-1)” of JP2009-104145A. 80 in the following formula (b-1) represents an average value of the number of repeating structural units.

Next, each of the following components was introduced into a glass flask equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a gas inlet.
70 parts of the compound represented by the above formula (b-1) 30 parts of a product comprising the compound represented by the above formula (a-1) as a main component 30 parts of trifluorotoluene 0.35 parts of azobisisobutyronitrile Nitrogen gas was introduced into the flask into which the components had been introduced, and reacted for 20 hours under reflux (heating to about 100 ° C.). This reaction solution was poured into 10 times the amount of methanol, precipitated, and filtered.

  1 part of the obtained filtrate was stirred at 10 ° C. for 15 minutes in a mixed solution of 43 parts of methanol and 17 parts of ion-exchanged water, and then subjected to centrifugal filtration with a polypropylene filter. 40 parts of methanol was further added to the obtained filtrate, and the mixture was stirred at 10 ° C. for 40 minutes, followed by centrifugal filtration with a polypropylene filter. The obtained residue was air-dried for 8 hours or longer and then dried under reduced pressure in a vacuum dryer with a stirrer at a temperature of 70 ° C. and an internal pressure of 260 mmHg or less for 3 hours. Thus, a polymer (F-1) having a repeating structural unit represented by the following formula (c-1) and a repeating structural unit derived from the structure represented by the above formula (b-1) was obtained. The weight average molecular weight of the polymer (F-1) was 91,000, and the area with a molecular weight of 300,000 or more in the GPC (gel permeation chromatography) chart was 7.2% with respect to the entire area.

次に、下記にしたがって保護層用塗布液を得た。

Next, the coating liquid for protective layers was obtained according to the following.

<Step of obtaining first dispersion (i)>
1.8 parts of the polymer (C-1) were mixed with 39 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane (trade name: Zeolora H, manufactured by Nippon Zeon Co., Ltd.) and 1- It was dissolved in a mixed solvent of 51 parts of propanol. Thereafter, a solution obtained by adding 30 parts of tetrafluoroethylene resin particles (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) is used as a high-pressure disperser (trade name: Microfluidizer M-110EH, manufactured by Microfluidics, USA). Put in. And it passed 6 times with the pressure of 40 Mpa, and obtained the 1st dispersion liquid. The number average particle diameter of the tetrafluoroethylene resin particles in the obtained first dispersion was 0.20 μm.

<Step of obtaining second dispersion (ultrasonic step) (ii)>
Thereafter, the first dispersion was subjected to ultrasonic irradiation for 15 minutes using an ultrasonic cleaner (frequency 40 kHz, output 1,200 W) manufactured by Tokyo Ultrasonic Giken to obtain a second dispersion.

<Step of preparing a coating solution for protective layer (iii)>
Subsequently, 70 parts of a hole transporting compound represented by the following formula (H-5), 30 parts of 1,1,2,2,3,3,4-heptafluorocyclopentane and 30 parts of 1-propanol were added to the above-mentioned first. 2 to the dispersion. And the coating liquid for protective layers was prepared by filtering with a polyfluorone filter (brand name: PF-040, Advantech Toyo Co., Ltd. product).

<Process for forming protective layer (iv)>
This coating solution for protective layer was dip-coated on the charge transport layer of the electrophotographic photoreceptor 1 to form a coating film, and the obtained coating film was dried at a temperature of 50 ° C. for 5 minutes. After drying, the coating film was irradiated with an electron beam for 1.6 seconds under the conditions of an acceleration voltage of 60 kV and an absorbed dose of 8,000 Gy in a nitrogen atmosphere. Thereafter, heat treatment was performed for 1 minute in a nitrogen atmosphere under conditions where the temperature of the coating film was 130 ° C. Note that the oxygen concentration from the electron beam irradiation to the heat treatment for 1 minute was 15 ppm. Next, heat treatment was performed in the atmosphere for 1 hour under the condition that the coating film became 110 ° C. to form a surface layer (protective layer) having a thickness of 5 μm.

(Electrophotographic photoreceptor 48)
An electrophotographic photoreceptor 48 was produced in the same manner as in the production example of the electrophotographic photoreceptor 1 except that the second intermediate layer was formed by the following method.
[Method for Forming Second Intermediate Layer of Electrophotographic Photoreceptor 48]
100 parts of rutile-type titanium oxide particles (average primary particle size: 50 nm, manufactured by Teika Co., Ltd.) were mixed with 500 parts of toluene with stirring, and vinyltrimethoxysilane represented by the following formula (1) (trade name: KBM-1003, 3.0 parts of Shin-Etsu Chemical Co., Ltd.) was added and stirred for 8 hours.
(CH ₃ O) ₃ SiCH═CH ₂ Formula (1)
Then, toluene was distilled off under reduced pressure and dried at a temperature of 120 ° C. for 3 hours to obtain rutile-type titanium oxide particles surface-treated with vinyltrimethoxysilane.

A dispersion was prepared by adding the following materials to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol.
Rutile-type titanium oxide particles surface-treated with vinyltrimethoxysilane 18 parts N-methoxymethylated nylon (trade name: Toresin EF-30T, manufactured by Nagase ChemteX Corp.) 4.5 parts Copolymer nylon resin (product) Name: Amilan CM8000, manufactured by Toray Industries, Inc.) 1.5 parts This dispersion is subjected to a dispersion treatment for 5 hours in a vertical sand mill using glass beads having a diameter of 1.0 mm, thereby applying a second intermediate layer. A liquid was prepared. The second intermediate layer coating solution is dip-coated on the first intermediate layer, and the obtained coating film is dried at a temperature of 100 ° C. for 10 minutes, whereby a second film thickness of 2.0 μm is obtained. An intermediate layer was formed.

(Electrophotographic photoreceptor 49)
An electrophotographic photoreceptor 49 was produced in the same manner as in the production example of the electrophotographic photoreceptor 1 except that the second intermediate layer was formed by the following method.
[Method for Forming Second Intermediate Layer of Electrophotographic Photoreceptor 49]
Under a nitrogen stream at room temperature, 26.8 g (100 mmol) of naphthalene-1,4,5,8-tetracarboxylic dianhydride and 250 mL of dimethylacetamide were placed in a 500 mL three-necked flask. After heating to 120 ° C., 11.6 g (100 mmol) of 4-heptylamine was added dropwise thereto with stirring. It stirred for 3 hours after completion | finish of dripping.
Next, a mixture of 9.2 g (100 mmol) of 2-amino-1,3-propanediol and 50 mL of dimethylacetamide was added dropwise with stirring. After completion of dropping, the mixture was heated to reflux for 6 hours. After completion of the reaction, the container was cooled and concentrated under reduced pressure. Ethyl acetate was added to the residue, followed by filtration, and the filtrate was purified by silica gel column chromatography. Further, the recovered product was recrystallized with a mixed solvent of ethyl acetate / hexane to obtain 10.5 g of an electron transport material represented by the following formula (D-1).

この化合物をＭＡＬＤＩ−ＴＯＦ ＭＳ（Matrix Assisted Laser Desorption / Ionization-Time of Flight Mass Spectrometry）で測定したところ、ピークトップ値（分子量）４３８を得た。

When this compound was measured by MALDI-TOF MS (Matrix Assisted Laser Desorption / Ionization-Time of Flight Mass Spectrometry), a peak top value (molecular weight) 438 was obtained.

Next, the following materials were dissolved in a mixed solvent of 50 parts of 1-methoxy-2-propanol and 50 parts of tetrahydrofuran.
Compound represented by the above formula (D-1) as an electron transport material 3.36 parts Styrene-acrylic resin (trade name: UC-3920, manufactured by Toagosei Co., Ltd.) as a polyolefin resin 0.35 parts As an isocyanate compound Blocked isocyanate compound (trade name: SBB-70P, manufactured by Asahi Kasei Co., Ltd.) 6.40 parts Silica slurry dispersed in isopropyl alcohol in this solution (product name: IPA-ST-UP, Nissan Chemical Industries, Ltd.) (Manufactured, solid content concentration: 15% by mass, viscosity: 9 mPa · s) was added and stirred for 1 hour. Then, pressure filtration was performed using a polytetrafluoroethylene filter (product name: PF020) manufactured by ADVANTEC.
The coating solution for the second intermediate layer thus obtained was dip-coated on the first intermediate layer, and the resulting coating film was heated at 170 ° C. for 40 minutes to be cured (polymerized), whereby the film thickness was 0. A second intermediate layer of 7 μm was formed.

[Evaluation]
(Evaluation of fog and black spots during long-term use)
Each of the electrophotographic photoreceptors produced above was mounted on a laser beam printer Color Laser Jet Enterprise M552 manufactured by Hewlett-Packard, and a paper passing durability test was performed in an environment of a temperature of 23 ° C./relative humidity of 50%. For paper-passing durability, print operation is performed in an intermittent mode in which character images with a printing rate of 2% are output one by one on letter paper. Waste toner in the process cartridge is discharged and new toner is filled every 5,000 sheets. The image output was repeated until the thickness of the charge transport layer reached 7 μm. Film thickness measurement was performed for every 1,000 image outputs, and was performed with a Fischer MMS eddy current probe EAW3.3.

Then, fog and black spots were evaluated at the start of paper passing durability, and fog evaluation was performed after paper passing durability. In the evaluation of fog and black spots, application to the charging roller (roller-shaped charging member) was performed using an external power source so that the surface potential (Vd) of the electrophotographic photosensitive member was −400V. In the fog evaluation, the reflectance of the white portion of the above image and the unused paper was measured with a reflection measuring machine REFECTMETETER (Tokyo Denshoku Co., Ltd.) for fog evaluation, and the difference between the two was defined as fog. Evaluation was made according to the following criteria, as unused paper reflectance-image white area reflectance = fog%.
A: fog was less than 0.5% B: fog was 0.5% or more and less than 1.0% C: fog was 1.0% or more and less than 1.5% D: fog 1.5% E: It was less than 2.0%. E: Fog was 2.0% or more.

For the evaluation of black spots, A4 size gloss paper was used and a solid white image was output. The output image is included in the area of one circumference of the electrophotographic photosensitive member (a rectangular region having a vertical length of 297 mm which is the long side length of A4 paper and a horizontal length of 94.2 mm which is one circumference of the electrophotographic photosensitive member). The number of black spots was visually counted and evaluated according to the following criteria.
A: Black spots were not found B: 1 to 3 black spots with a diameter greater than 0.3 mm were found C: 4 to 5 black spots with a diameter greater than 0.3 mm were seen D: Diameter was 6 to 7 black spots larger than 0.3 mm were found E: Tables 7 and 8 show the evaluation results based on the above evaluation in which 8 or more black spots larger than 0.3 mm were seen.

DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 2 Axis 3 Charging means 4 Exposure light 5 Developing means 6 Transfer means 7 Transfer material 8 Fixing means 9 Cleaning means 10 Pre-exposure light 11 Process cartridge 12 Guide means

Claims (5)

An electrophotographic photoreceptor having a support, an intermediate layer formed on the support, and a photosensitive layer formed on the intermediate layer,
The intermediate layer comprises a first intermediate layer formed on the support and a second intermediate layer formed on the first intermediate layer,
The electrophotographic photoreceptor, wherein the first intermediate layer contains titanium oxide particles doped with niobium or tantalum.   The electrophotographic photosensitive member according to claim 1, wherein the number average particle size of primary particles of the titanium oxide particles is 50 nm or more and 500 nm or less.   The electrophotographic photosensitive member according to claim 1 or 2, wherein a doping amount of niobium or tantalum doped in the titanium oxide particles is 0.5% by mass or more and 10% by mass or less of the total mass of the titanium oxide.   An electrophotographic photosensitive member according to any one of claims 1 to 3 and at least one means selected from the group consisting of a charging means, a developing means, a transfer means and a cleaning means are integrally supported, and an electrophotographic A process cartridge which is detachable from the apparatus main body. An electrophotographic apparatus comprising: the electrophotographic photosensitive member according to claim 1; and a charging unit, an exposure unit, a developing unit, and a transfer unit.

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