Electrophotographic photoreceptor, process cartridge, and electrophotographic apparatus

Abstract

To provide an electrophotographic photoreceptor that can attain a high sensitivity and the effect of suppressing a transfer memory phenomenon at a high level.SOLUTION: The electrophotographic photoreceptor sequentially includes a supporting body, an undercoat layer, a charge generation layer, and a charge transport layer. The undercoat layer contains a polyamide resin and titanium oxide fine particles. The arithmetic average roughness Ra and the average length Rsm of a roughness curve element when the surface of the undercoat layer has the roughness of JIS B0601:2001 satisfy the relation of Ra≤50nm and 0.1≤Ra / Rsm≤0.5. The charge generation layer contains a hydroxy-gallium phthalocyanine pigment. The hydroxy-gallium phthalocyanine pigment has crystal particles of a crystal type that shows the peak in where the Bragg angle 2θ is in the range between 7.4° ±0.3° and 28.2° ±0.3° in the X-ray diffraction spectrum using a CuKα ray. There is a peak in where the size is in the range from 20nm to 50nm in a size distribution of crystal particles measured by a small-angle X-ray diffusion. The half width of the peak is not larger than 50nm.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Currently, since the oscillation wavelengths of semiconductor lasers, which are often used as image exposure means in the electrophotographic field, are as long as 650 to 820 nm, the development of electrophotographic photoreceptors having high sensitivity to these long-wavelength lights is underway. Phthalocyanine pigments are effective as charge generating substances having high sensitivity to light up to such a long-wavelength region. In particular, oxytitanium phthalocyanine and gallium phthalocyanine have excellent sensitivity characteristics, and various crystal forms have been reported so far.

[0003] Patent Document 1 describes that a sensitizing effect can be brought about by adding a specific organic electron acceptor during the acid pasting process of a phthalocyanine pigment. However, this method has problems such as concerns about chemical changes in the additive (organic electron acceptor) and difficulties in converting to a desired crystal form in some cases.

[0004] Patent Document 2 describes hydroxygallium phthalocyanine crystals containing a polar organic solvent. By using a conversion solvent such as N,N-dimethylformamide, it is described that conversion solvent molecules are incorporated into the crystal and crystals having high sensitivity characteristics can be obtained.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, in response to the rapid acceleration of the electrophotographic process, various improvements have been attempted to achieve higher sensitivity using phthalocyanine pigments used as charge generation materials for electrophotographic photoreceptors. However, according to the studies of the present inventors, it has been found that with the acceleration of the electrophotographic process, a new transfer memory has emerged as a problem.

[0007] The transfer memory in the present invention is considered to occur by the mechanism described below. The electrophotographic process related to the electrophotographic photoreceptor mainly consists of four processes: charging, exposure, development, and transfer. In the case of an electrophotographic apparatus corresponding to recent digitization, it is common to adopt an inversion development system. In inversion development, since toner is developed on the exposed part of the electrophotographic photoreceptor, the charge and the toner have the same polarity. As a result, the charging and the transfer have opposite polarities. When a negatively charged photoreceptor is used, transfer is performed with a positive charge of the opposite polarity. Therefore, the residual optical carriers generated by the negative charging and the subsequent exposure are driven in the opposite direction (electrons are in the direction of the photoreceptor surface, and holes are in the direction of the photoreceptor support) by the positive electric field generated by the positive charge during transfer. As a result, electrons and holes accumulate near the interfaces between the charge generation layer and the charge transport layer and between the charge generation layer and the undercoat layer, respectively. If they are not erased and the next charging is encountered, a sufficient charging potential cannot be obtained, and fogging occurs on the image, resulting in a problem called transfer memory.

[0008] Therefore, an object of the present invention is to provide an electrophotographic photoreceptor that can achieve both suppression of transfer memory and high sensitivity at a high level, as well as a process cartridge and an electrophotographic apparatus using the electrophotographic photoreceptor.

[0009] The above object is achieved by the following present invention. That is, the electrophotographic photoreceptor according to the present invention has, in this order, a support, an undercoat layer, a charge generation layer, and a charge transport layer containing a charge transport material. The undercoat layer contains a polyamide resin and titanium oxide fine particles, The arithmetic mean roughness Ra and the average length Rsm of the roughness curve elements on the surface of the undercoat layer satisfy the following formulas (A) and (B) according to JIS B0601:2001, Ra ≦ 50 nm Formula (A) 0.1 ≦ Ra / Rsm ≦ 0.5 Formula (B) The charge generation layer contains a hydroxygallium phthalocyanine pigment, The hydroxygallium phthalocyanine pigment has crystalline particles of a crystal form that exhibit peaks at Bragg angles 2θ of 7.4° ± 0.3° and 28.2° ± 0.3° in an X-ray diffraction spectrum using CuKα rays, and in the size distribution of the crystal particles measured using small-angle X-ray scattering, a peak exists in the range of 20 nm or more and 50 nm or less, and the half-value width of the peak is 50 nm or less.

[0010] Further, the present invention is a process cartridge that integrally supports the above electrophotographic photoreceptor and at least one means selected from the group consisting of charging means, developing means, and cleaning means, and is detachable from the main body of the electrophotographic apparatus.

[0011] Further, the present invention is an electrophotographic apparatus having the above electrophotographic photoreceptor, and charging means, exposure means, developing means, and transfer means.

Effects of the Invention

[0012] According to the present invention, it is possible to provide an electrophotographic photoreceptor that can achieve both high sensitivity required for electrophotographic photoreceptors in recent years and a high level of suppression effect on transfer memory phenomenon, and a process cartridge and an electrophotographic apparatus using such an electrophotographic photoreceptor.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described in detail with reference to preferred embodiments. The electrophotographic photoreceptor of the present invention has a support, an undercoat layer, a charge generation layer, and a charge transport layer containing a charge transport material, in this order. The undercoat layer contains a polyamide resin and titanium oxide fine particles. The arithmetic mean roughness Ra in JIS B0601:2001 and the average length Rsm of the roughness curve elements on the surface of the undercoat layer satisfy the following formulas (A) and (B). Ra ≦ 50 nm Formula (A) 0.1 ≦ Ra / Rsm ≦ 0.5 Formula (B) The charge generation layer contains a hydroxygallium phthalocyanine pigment. The hydroxygallium phthalocyanine pigment has crystal particles of a crystal form that show peaks at Bragg angles 2θ of 7.4° ± 0.3° and 28.2° ± 0.3° in the X-ray diffraction spectrum using CuKα rays, and in the size distribution of the crystal particles measured using small-angle X-ray scattering, a peak exists in the range of 20 nm or more and 50 nm or less, and the half-value width of the peak is 50 nm or less.

[0015] Regarding the reason why such an electrophotographic photoreceptor can achieve both high sensitivity and suppression of the transfer memory phenomenon at a high level, the present inventors speculate as follows. For the purpose of preventing charge accumulation in the undercoat layer during long-term use of the electrophotographic photoreceptor, it is generally known to contain metal oxide particles such as titanium oxide in the undercoat layer. At this time, surface roughness caused by containing oxide particles on the surface of the undercoat layer appears.

[0016] In the present invention, the arithmetic mean roughness Ra in JIS B0601:2001 and the average length Rsm of the roughness curve elements on the surface of the undercoat layer containing titanium oxide fine particles satisfy Ra≦50 nm (Formula (A)) and 0.1≦Ra / Rsm≦0.5 (Formula (B)). Further, in the present invention, in the size distribution of crystal particles measured using small-angle X-ray scattering in the charge generation layer, a peak exists in the range of 20 nm or more and 50 nm or less, and a hydroxygallium phthalocyanine pigment having a half-value width of the peak of 50 nm or less is used. By having these characteristics, the scale of the concave portions of the unevenness on the surface of the undercoat layer becomes close to the scale of the hydroxygallium phthalocyanine pigment particles. As a result, the contact area between the hydroxygallium phthalocyanine pigment and the surface of the undercoat layer increases, the charge injection efficiency between the undercoat layer and the charge generation layer improves, the accumulation of positive charges is suppressed in the transfer process, and a sufficient charging potential can be obtained in the next charging process, and transfer memory can be suppressed without fogging occurring on the image.

[0017] When Ra is larger than 50 nm or Ra / Rsm is smaller than 0.1, the scale of the concave portions of the undercoat layer becomes larger than the scale of the crystal particles of the hydroxygallium phthalocyanine pigment, and the contact area between the hydroxygallium phthalocyanine pigment and the surface of the undercoat layer decreases, so that the effect of suppressing transfer memory cannot be sufficiently obtained. Also, when Ra / Rsm is larger than 0.5, the concave portions of the undercoat layer become deeper, the hydroxygallium phthalocyanine pigment cannot enter the concave portions, and a binder resin enters between the undercoat layer and the hydroxygallium phthalocyanine pigment, so that the contact area between the hydroxygallium phthalocyanine pigment and the surface of the undercoat layer decreases, and thus the effect of suppressing transfer memory cannot be sufficiently obtained. In the size distribution of crystal particles of the hydroxygallium phthalocyanine pigment measured using small-angle X-ray scattering, if the peak position is larger than 50 nm or the half-value width of the peak is larger than 50 nm, the light utilization efficiency decreases, resulting in a decrease in sensitivity. Further, since there are many hydroxygallium phthalocyanine pigment particles having a different scale from the concave portions of the undercoat layer, the effect of suppressing transfer memory cannot be sufficiently obtained.

[0018] [Electrophotographic Photoconductor] The electrophotographic photoconductor of the present invention has a support, an undercoat layer, and a photosensitive layer formed on the undercoat layer. FIG. 2 is a diagram showing an example of the layer structure of the electrophotographic photoconductor. In FIG. 2, 101 is a support, 102 is an undercoat layer, 103 is a charge generation layer, 104 is a charge transport layer, and 105 is a photosensitive layer (laminated photosensitive layer).

[0019] Hereinafter, the support and each layer will be described. [Support] In the present invention, the support is preferably a conductive support having conductivity. Examples of the conductive support include supports formed of metals or alloys such as aluminum, iron, nickel, copper, and gold, and thin films of metals such as aluminum, chromium, silver, and gold; thin films of conductive materials such as indium oxide, tin oxide, and zinc oxide; and supports formed with thin films of conductive ink added with silver nanowires on insulating supports such as polyester resins, polycarbonate resins, polyimide resins, and glass. The surface of the support may be subjected to electrochemical treatments such as anodic oxidation, wet honing treatment, blasting treatment, cutting treatment, etc. to improve electrical characteristics and suppress interference fringes. Examples of the shape of the support include a cylindrical shape or a film shape.

[0020] [Conductive Layer] In the present invention, a conductive layer may be provided on the support. By providing the conductive layer, it becomes possible to cover unevenness and defects on the support surface and prevent interference fringes. The average film thickness of the conductive layer is preferably 5 μm or more and 40 μm or less, and more preferably 10 μm or more and 30 μm or less.

[0021] The conductive layer preferably contains conductive particles and a binder resin. Examples of the conductive particles include carbon black, metal particles, and metal oxide particles. 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, chromium, copper, zinc, and silver. Among these, it is preferable to use metal oxide as the conductive particles, and more preferably to use titanium oxide, tin oxide, or zinc oxide. When using metal oxide as the conductive particles, the surface of the metal oxide may be treated with a silane coupling agent or the like, or the metal oxide may be doped with an element such as phosphorus or aluminum or its oxide. Examples of the element or its oxide to be doped include phosphorus, aluminum, niobium, and tantalum. Further, the conductive particles may have a laminated structure having core particles and a coating layer covering the particles. Examples of the core particles include titanium oxide, barium sulfate, and zinc oxide. Examples of the coating layer include metal oxides such as tin oxide and titanium oxide.

[0022] When using metal oxide as the conductive particles, the volume average particle diameter thereof is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

[0023] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, and alkyd resin. Further, the conductive layer may further contain a hiding agent such as silicone oil, resin particles, or titanium oxide.

[0024] The average film thickness of the conductive layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less. The conductive layer can be formed by preparing a coating solution for the conductive layer containing the above-mentioned respective materials and a solvent, forming this coating film on a support, and drying it. Examples of the solvent used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, and the like. Examples of the dispersion method for dispersing conductive particles in the coating solution for the conductive layer include methods using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

[0025] <Undercoat layer> An undercoat layer is provided between the support or the conductive layer and the charge generation layer. The undercoat layer contains a polyamide resin and titanium oxide fine particles. As the polyamide resin, a polyamide resin soluble in an alcohol-based solvent is preferable. For example, ternary (6-66-610) copolymer polyamide, quaternary (6-66-610-12) copolymer polyamide, N-methoxymethylated nylon, polymerized fatty acid-based polyamide, polymerized fatty acid-based polyamide block copolymer, copolymer polyamide having a diamine component, etc. are preferably used.

[0026] From the viewpoint of suppressing charge accumulation, the crystal structure of the titanium oxide fine particles is preferably rutile type or anatase type, and more preferably rutile type with weak photocatalytic activity. When the crystal structure is rutile type, the rutile ratio is preferably 90% or more. The shape of the titanium oxide fine particles is preferably spherical, and its average primary particle size (number average particle size) is 10 nm or more and 120 nm or less, preferably 10 nm or more and 100 nm or less, and more preferably 30 nm or more and 60 nm or less from the viewpoints of suppressing charge accumulation and uniform dispersibility. The titanium oxide fine particles may be treated with a silane coupling agent or the like from the viewpoint of uniform dispersibility.

[0027] In addition to the above polyamide resin and titanium oxide fine particles, the undercoat layer in the present invention may contain additives such as organic particles and leveling agents for the purpose of enhancing the film-forming property of the undercoat layer of the electrophotographic photoreceptor. However, the content of the additive in the undercoat layer is preferably 10% by mass or less based on the total mass of the undercoat layer.

[0028] The average film thickness of the undercoat layer is 0.3 μm or more and 5 μm or less, and preferably 0.5 μm or more and 3.0 μm or less. When the film thickness of the undercoat layer is 3.0 μm or less, the effect of suppressing charge accumulation is further enhanced. When the film thickness of the undercoat layer is less than 0.3 μm, leakage is more likely to occur due to a decrease in local charging performance.

[0029] The undercoat layer can be formed by preparing a coating solution for the undercoat layer containing the above-mentioned respective materials and a solvent, forming this coating film on a support or a conductive layer, and drying and / or curing it. Examples of the solvent used in the coating solution for the undercoat layer include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Examples of the dispersion method for dispersing titanium oxide fine particles in the coating solution for the undercoat layer include ultrasonic dispersion, paint shaker, sand mill, ball mill, and a method using a liquid collision type high-speed disperser.

[0030] <Charge generation layer> A charge generation layer is provided directly above the undercoat layer. The charge generation layer of the present invention is obtained by dispersing the hydroxygallium phthalocyanine pigment of the present invention as a charge generating substance and, if necessary, a binder resin in a solvent to prepare a coating solution for the charge generation layer, and forming and drying a coating film of the coating solution for the charge generation layer on the undercoat layer. The coating solution for the charge generation layer may be prepared by adding only the charge generating substance to a solvent for dispersion treatment and then adding the binder resin, or by adding the charge generating substance and the binder resin together to a solvent for dispersion treatment. During the above dispersion, a media type disperser such as a sand mill or a ball mill, or a disperser such as a liquid collision type disperser or an ultrasonic disperser can be used.

[0031] Examples of the binder resin used in the charge generation layer include resins (insulating resins) such as polyvinyl butyral resin, polyvinyl acetal resin, polyarylate resin, polycarbonate resin, polyester resin, polyvinyl acetate resin, polysulfone resin, polystyrene resin, phenoxy resin, acrylic resin, phenoxy resin, polyacrylamide resin, polyvinyl pyridine resin, urethane resin, agarose resin, cellulose resin, casein resin, polyvinyl alcohol resin, polyvinyl pyrrolidone resin, vinylidene chloride resin, acrylonitrile copolymer, and polyvinyl benzal resin. Further, organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinyl anthracene, and polyvinyl pyrene can also be used. The binder resin may be used alone or in combination of two or more as a mixture or copolymer.

[0032] Examples of the solvent used in the coating liquid for the charge generation layer include toluene, xylene, tetralin, chlorobenzene, dichloromethane, chloroform, trichloroethylene, tetrachloroethylene, carbon tetrachloride, methyl acetate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, acetone, methyl ethyl ketone, cyclohexanone, diethyl ether, dipropyl ether, propylene glycol monomethyl ether, dioxane, methylal, tetrahydrofuran, water, methanol, ethanol, n-propanol, isopropanol, butanol, methyl cellosolve, methoxypropanol, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and the like. The solvent can be used alone or in a mixture of one or more.

[0033] The average film thickness of the charge generation layer of the present invention is 0.15 μm or more, preferably 0.2 μm or more.

[0034] (Hydroxygallium phthalocyanine pigment) In the present invention, the charge generating material contains a hydroxygallium phthalocyanine pigment. These may have axial ligands or substituents. In the present invention, the hydroxygallium phthalocyanine pigment has crystalline particles showing peaks at Bragg angles 2θ of 7.4° ± 0.3° and 28.2° ± 0.3° in an X-ray diffraction spectrum using CuKα rays, and in the size distribution of the crystalline particles measured using small-angle X-ray scattering, a peak exists in the range of 20 nm or more and 50 nm or less, and the half-value width of the peak is 50 nm or less.

[0035] Furthermore, it is more preferable that the hydroxygallium phthalocyanine pigment has crystalline particles containing an amide compound represented by the following formula (A1) therein. Examples of the amide compound represented by formula (A1) include N-methylformamide, N-propylformamide, or N-vinylformamide.

Chemical formula

[0036] Also, the content of the amide compound represented by the formula (A1) contained in the crystalline particles is preferably 0.1% by mass or more and 3.0% by mass or less, and more preferably 0.1% by mass or more and 1.4% by mass or less, based on the content of the crystalline particles. When the content of the amide compound is 0.1% by mass or more and 3.0% by mass or less, the size of the crystalline particles can be made uniform. The hydroxygallium phthalocyanine pigment containing the amide compound represented by the formula (A1) in the crystalline particles is obtained by a hydroxygallium phthalocyanine pigment obtained by an acid pasting method and a step of crystal conversion of the amide compound represented by the above formula (A1) by wet milling treatment.

[0037] When using a dispersant in the milling process, the amount of the dispersant is preferably 10 to 50 times that of the hydroxygallium phthalocyanine pigment on a mass basis. Examples of the solvent to be used include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, the compound represented by the above formula (A1), N-methylacetamide, and N-methylpropionamide; halogen solvents such as chloroform; ether solvents such as tetrahydrofuran; and sulfoxide solvents such as dimethyl sulfoxide. The amount of the solvent used is preferably 5 to 30 times that of the hydroxygallium phthalocyanine pigment on a mass basis.

[0038] Further, when attempting to obtain the crystalline hydroxygallium phthalocyanine pigment used in the present invention in the crystal conversion step, the inventors have found that when using the amide compound represented by the above formula (A1) as the solvent, the time required for the crystal form conversion becomes longer. Specifically, when using N-methylformamide as the solvent, the time required for crystal conversion increases several times compared to when using N,N-dimethylformamide. The long time required for crystal conversion provides a time allowance for reducing the size of crystal particles to a certain extent until the crystal form conversion is completed, making it easier to obtain the hydroxygallium phthalocyanine pigment of the present invention.

[0039] Whether the hydroxygallium phthalocyanine pigment of the present invention contains the amide compound represented by the above formula (A1) in the crystal particles was determined by analyzing the data of 1H-NMR measurement of the obtained hydroxygallium phthalocyanine pigment. Also, the content of the amide compound represented by the above formula (A1) in the crystal particles was determined by analyzing the results of 1H-NMR measurement. For example, when performing a milling treatment with a solvent capable of dissolving the amide compound represented by the above formula (A1) or a washing step after milling, the obtained hydroxygallium phthalocyanine pigment is subjected to 1H-NMR measurement. When a peak derived from the amide compound represented by the above formula (A1) is detected in the data of the 1H-NMR measurement, it can be determined that the amide compound represented by the above formula (A1) is contained in the crystal.

[0040] When obtaining the hydroxygallium phthalocyanine pigment of the present invention by centrifugation, in order to control the ratio P of the volume of the charge generating substance to the total volume of the charge generation layer, in the liquid for mixing the hydroxygallium phthalocyanine pigment and the binder resin, the weight ratio of the hydroxygallium phthalocyanine pigment to the binder resin must be measured. The weight ratio in the liquid for mixing the hydroxygallium phthalocyanine pigment and the binder resin was determined by analyzing the data of 1H-NMR measurement. For example, when using a hydroxygallium phthalocyanine pigment as the phthalocyanine pigment and polyvinyl butyral as the binder resin, the weight ratio of the hydroxygallium phthalocyanine pigment to the binder resin can be determined by comparing the peak derived from the hydroxygallium phthalocyanine pigment and the peak derived from polyvinyl butyral in the data of 1H-NMR measurement.

[0041] The powder X-ray diffraction measurement and 1H-NMR measurement of the hydroxygallium phthalocyanine pigment contained in the electrophotographic photoreceptor of the present invention were performed under the following conditions. (Powder X-ray diffraction measurement) Measuring instrument used: RINT-TTRII X-ray diffractometer manufactured by Rigaku Corporation X-ray tube: Cu X-ray wavelength: Kα1 Tube voltage: 50 KV Tube current: 300 mA Scanning method: 2θ scan Scanning speed: 4.0° / min Sampling interval: 0.02° Start angle (2θ): 5.0° Stop Angle (2θ): 35.0° Goniometer: Rotor Horizontal Goniometer (TTR-2) Attachment: Capillary Rotating Sample Stage Filter: None Detector: Scintillation Counter Incident Monochromator: Used Slit: Variable Slit (Parallel Beam Method) Counter Monochromator: Not Used Divergence Slit: Open Divergence Vertical Limiting Slit: 10.00 mm Scattering Slit: Open Receiving Slit: Open (1H-NMR Measurement) Measuring Instrument Used: AVANCEIII 500, manufactured by BRUKER Solvent: Deuterium Sulfate (D2SO4) Number of Integrations: 2,000

[0042] <Charge Transport Layer> The charge transport layer preferably contains a charge transport material and a resin.

[0043] Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Among these, triarylamine compounds and benzidine compounds are preferred. The content of the charge transport material in the charge transport layer is preferably 25% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 55% by mass or less, based on the total mass of the charge transport layer.

[0044] Examples of the resin include polyester resins, polycarbonate resins, acrylic resins, polystyrene resins, etc. Among these, polycarbonate resins and polyester resins are preferred. Among the polyester resins, polyarylate resins are particularly preferred. The content ratio (mass ratio) of the charge transport material to the resin is preferably from 4:10 to 20:10, more preferably from 5:10 to 12:10.

[0045] In addition, the charge transport layer may contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slipperiness imparting agents, and wear resistance improving agents. Specifically, hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles, etc. can be mentioned.

[0046] 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.

[0047] The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing the above-mentioned respective materials and a solvent, forming this coating film on the charge generation layer, and drying it. Examples of the solvent used in the coating solution include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Among these solvents, ether solvents or aromatic hydrocarbon solvents are preferred.

[0048] <Protective layer> In the present invention, a protective layer may be provided on the photosensitive layer. By providing the protective layer, the durability can be improved. The protective layer preferably contains conductive particles and / or a charge transport material and a resin. Examples of the conductive particles include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide. Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Among these, triarylamine compounds and benzidine compounds are preferred. Examples of the resin include polyester resin, acrylic resin, phenoxy resin, polycarbonate resin, polystyrene resin, phenol resin, melamine resin, epoxy resin, etc. Among them, polycarbonate resin, polyester resin, and acrylic resin are preferable.

[0049] 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 thermal polymerization reaction, photopolymerization reaction, radiation polymerization reaction, etc. Examples of the polymerizable functional group of the monomer having a polymerizable functional group include an acrylic group, a methacrylic group, etc. As the monomer having a polymerizable functional group, a material having a charge transport ability may be used.

[0050] The protective layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a slipperiness imparting agent, a wear resistance improving agent, etc. Specifically, hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, boron nitride particles, etc. may be mentioned.

[0051] 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.

[0052] The protective layer can be formed by preparing a coating liquid for the protective layer containing each of the above materials and a solvent, forming this coating film on the photosensitive layer, and drying and / or curing it. Examples of the solvent used in the coating liquid include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0053] [Process Cartridge and Electrophotographic Apparatus] FIG. 3 shows an example of the schematic configuration of an electrophotographic apparatus having a process cartridge including an electrophotographic photoreceptor. In FIG. 3, reference numeral 1 denotes a cylindrical (drum-shaped) electrophotographic photoreceptor, which is rotationally driven about an axis 2 at a predetermined peripheral speed (process speed) in the direction of the arrow.

[0054] The surface of the electrophotographic photoreceptor 1 is charged to a predetermined positive or negative potential by a charging unit 3 during the rotation process. Next, exposure light 4 is irradiated from an exposure unit (not shown) onto the charged surface of the electrophotographic photoreceptor 1, and an electrostatic latent image corresponding to the target image information is formed. The image exposure light 4 is light whose intensity is modulated corresponding to a time-series electrical digital image signal of the target image information output from an exposure unit such as slit exposure or laser beam scanning exposure.

[0055] The electrostatic latent image formed on the surface of the electrophotographic photoreceptor 1 is developed (normal development or reversal development) with toner housed in a developing unit 5, and a toner image is formed on the surface of the electrophotographic photoreceptor 1. The toner image formed on the surface of the electrophotographic photoreceptor 1 is transferred onto a transfer material 7 by a transfer unit 6. At this time, a bias voltage having a polarity opposite to the charge held by the toner is applied to the transfer unit 6 from a bias power source (not shown). Further, when the transfer material 7 is paper, the transfer material 7 is taken out from a paper feed unit (not shown) and fed between the electrophotographic photoreceptor 1 and the transfer unit 6 in synchronization with the rotation of the electrophotographic photoreceptor 1.

[0056] The transfer material 7 onto which the toner image has been transferred from the electrophotographic photoreceptor 1 is conveyed to the fixing means 8 after being separated from the surface of the electrophotographic photoreceptor 1, and is printed out of the electrophotographic apparatus as an image formation (print, copy) by undergoing the fixing process of the toner image. The surface of the electrophotographic photoreceptor 1 after transferring the toner image to the transfer material 7 is cleaned by the cleaning means 9 to remove deposits such as toner (remaining transferred toner). With the cleanerless system developed in recent years, the remaining transferred toner can also be directly removed by a developing device or the like. Further, the surface of the electrophotographic photoreceptor 1 is discharged by the pre-exposure light 10 from the pre-exposure means (not shown) and then used repeatedly for image formation. In the case where the charging means 3 is a contact charging means using a charging roller or the like, the pre-exposure means is not necessarily required. In the present invention, among the components such as the above-described electrophotographic photoreceptor 1, charging means 3, developing means 5, and cleaning means 9, a plurality of components are housed in a container and integrally supported to form a process cartridge. This process cartridge can be configured to be detachable from the electrophotographic apparatus main body. For example, at least one selected from the charging means 3, developing means 5, and cleaning means 9 is integrally supported together with the electrophotographic photoreceptor 1 to form a cartridge. A process cartridge 11 that is detachable from the electrophotographic apparatus main body can be formed using guiding means 12 such as rails of the electrophotographic apparatus main body. The exposure light 4 may be reflected light or transmitted light from an original when the electrophotographic apparatus is a copying machine or a printer. Alternatively, it may be light emitted by reading an original with a sensor, converting it into a signal, and performing scanning of a laser beam, driving of an LED array, or driving of a liquid crystal shutter array according to this signal.

[0057] The electrophotographic photoreceptor 1 of the present invention can be widely applied to electrophotographic application fields such as laser beam printers, CRT printers, LED printers, FAX machines, liquid crystal printers, and laser plate making.

Example

[0058] Hereinafter, the present invention will be described in more detail using 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, "parts" means parts by mass unless otherwise specified.

[0059] For the film thickness of each layer of the electrophotographic photoreceptors in the examples and comparative examples, except for the charge generation layer, it was determined by a method using an eddy current type film thickness meter (Fischerscope, manufactured by Fischer Instruments), or a method of converting from the mass per unit area to specific gravity. The film thickness of the charge generation layer was measured by using a calibration curve previously obtained from the Macbeth density value measured by pressing a spectrocolorimeter (trade name: X-Rite504 / 508, manufactured by X-Rite) against the surface of the photoreceptor and the film thickness measurement value by cross-sectional SEM image observation, and converting the Macbeth density value of the photoreceptor.

[0060] [Preparation Example of Coating Liquid 1 for Undercoat Layer] 100 parts of rutile type titanium oxide fine particles (average primary particle size: 50 nm, manufactured by Tayca) were stirred and mixed with 500 parts of toluene, 3.0 parts of methyldimethoxysilane ("TSL8117" manufactured by Toshiba Silicone Co., Ltd.) was added, and the mixture was stirred for 8 hours. Thereafter, toluene was distilled off under reduced pressure, and the mixture was dried at 120 °C for 3 hours to obtain rutile type titanium oxide fine particles surface-treated with methyldimethoxysilane. 18 parts of the rutile type titanium oxide fine particles surface-treated with methyldimethoxysilane, 4.5 parts of N-methoxymethylated nylon (trade name: Torelina EF-30T, manufactured by Nagase ChemteX), and 1.5 parts of a copolymerized nylon resin (trade name: Amilan CM8000, manufactured by Toray) were added to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol to prepare a dispersion. This dispersion was subjected to a dispersion treatment for 6 hours in a vertical sand mill using glass beads with a diameter of 1.0 mm. Thereafter, the liquid subjected to the sand mill dispersion treatment was further subjected to a dispersion treatment for 1 hour using an ultrasonic disperser (UT-205, manufactured by Sharp) to prepare Coating Liquid 1 for Undercoat Layer. The output of the ultrasonic disperser was set to 100%. Also, no media such as glass beads were used in this milling treatment.

[0061] [Preparation Example of Coating Liquid 2 for Undercoat Layer] A coating liquid 2 for an undercoat layer was prepared in the same manner as the coating liquid 1 for an undercoat layer, except that the sand mill dispersion treatment time was changed to 4 hours in the preparation example of the coating liquid 1 for an undercoat layer.

[0062] [Preparation Example of Coating Liquid 3 for Undercoat Layer] 100 parts of rutile-type titanium oxide fine particles (average primary particle size: 15 nm, manufactured by Tayca) were stirred and mixed with 500 parts of toluene, 9.6 parts of methyldimethoxysilane ("TSL8117" manufactured by Toshiba Silicone Co., Ltd.) was added, and the mixture was stirred for 8 hours. Then, toluene was distilled off under reduced pressure and dried at 120 °C for 3 hours to obtain rutile-type titanium oxide fine particles surface-treated with methyldimethoxysilane. 6 parts of the rutile-type titanium oxide fine particles surface-treated with the methyldimethoxysilane, 4.5 parts of N-methoxymethylated nylon (trade name: Trelene EF-30T, manufactured by Nagase ChemteX), and 1.5 parts of a copolymer nylon resin (trade name: Amilan CM8000, manufactured by Toray) were added to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol to prepare a dispersion. This dispersion was subjected to a dispersion treatment for 6 hours using a vertical sand mill with glass beads having a diameter of 1.0 mm. Then, the liquid subjected to the sand mill dispersion treatment was further subjected to a dispersion treatment for 1 hour using an ultrasonic disperser (UT-205, manufactured by Sharp) to prepare a coating liquid 3 for an undercoat layer. The output of the ultrasonic disperser was set to 100%. Also, no media such as glass beads were used in this milling treatment.

[0063] [Preparation Example of Coating Liquid 4 for Undercoat Layer] A coating liquid 4 for an undercoat layer was prepared in the same manner as the coating liquid 3 for an undercoat layer, except that the sand mill dispersion treatment time was changed to 4 hours in the preparation example of the coating liquid 3 for an undercoat layer.

[0064] [Preparation Example of Coating Liquid 5 for Undercoat Layer] 100 parts of rutile-type titanium oxide fine particles (average primary particle size: 35 nm, manufactured by Teika) were stirred and mixed with 500 parts of toluene. 4.32 parts of methyldimethoxysilane (TSL8117, manufactured by Toshiba Silicone Co., Ltd.) was added, and the mixture was stirred for 8 hours. Thereafter, toluene was distilled off under reduced pressure and dried at 120 °C for 3 hours to obtain rutile-type titanium oxide fine particles surface-treated with methyldimethoxysilane. 12 parts of the rutile-type titanium oxide fine particles surface-treated with methyldimethoxysilane, 4.5 parts of N-methoxymethylated nylon (trade name: Torelina EF-30T, manufactured by Nagase ChemteX), and 1.5 parts of copolymerized nylon resin (trade name: Amilan CM8000, manufactured by Toray) were added to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol to prepare a dispersion. This dispersion was subjected to a dispersion treatment for 6 hours using a vertical sand mill with glass beads having a diameter of 1.0 mm. Thereafter, the liquid subjected to the sand mill dispersion treatment was further subjected to a dispersion treatment for 1 hour using an ultrasonic disperser (UT-205, manufactured by Sharp) to prepare a coating liquid 5 for the undercoat layer. The output of the ultrasonic disperser was set to 100%. Also, no media such as glass beads were used in this milling treatment.

[0065] [Preparation Example of Coating Liquid 6 for Undercoat Layer] A coating liquid 6 for the undercoat layer was prepared in the same manner as the coating liquid 5 for the undercoat layer, except that the sand mill dispersion treatment time was changed to 4 hours in the preparation example of the coating liquid 5 for the undercoat layer.

[0066] [Preparation Example of Coating Liquid 7 for Undercoat Layer] 100 parts of rutile-type titanium oxide fine particles (average primary particle size: 80 nm, manufactured by Teika) were stirred and mixed with 500 parts of toluene. 1.8 parts of methyldimethoxysilane (TSL8117, manufactured by Toshiba Silicone Co., Ltd.) was added, and the mixture was stirred for 8 hours. Thereafter, toluene was distilled off under reduced pressure and dried at 120 °C for 3 hours to obtain rutile-type titanium oxide fine particles surface-treated with methyldimethoxysilane. 18 parts of rutile-type titanium oxide fine particles surface-treated with methyl dimethoxysilane, 4.5 parts of N-methoxymethylated nylon (trade name: Trezene EF-30T, manufactured by Nagase ChemteX), and 1.5 parts of copolymerized nylon resin (trade name: Amilan CM8000, manufactured by Toray) were added to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol to prepare a dispersion. This dispersion was subjected to a dispersion treatment for 6 hours using a vertical sand mill with glass beads having a diameter of 1.0 mm. Subsequently, the liquid that had undergone the sand mill dispersion treatment was further subjected to a dispersion treatment for 1 hour using an ultrasonic disperser (UT-205, manufactured by Sharp) to prepare a coating liquid 7 for the undercoat layer. The output of the ultrasonic disperser was set to 100%. Also, no media such as glass beads were used in this milling treatment.

[0067] [Preparation Example of Coating Liquid 8 for Undercoat Layer] A coating liquid 8 for the undercoat layer was prepared in the same manner as the coating liquid 7 for the undercoat layer, except that the sand mill dispersion treatment time was changed to 4 hours in the preparation example of the coating liquid 7 for the undercoat layer.

[0068] [Preparation Example of Coating Liquid 9 for Undercoat Layer] 100 parts of rutile-type titanium oxide fine particles (average primary particle size: 120 nm, manufactured by Tayca) were stirred and mixed with 500 parts of toluene, 1.8 parts of methyl dimethoxysilane ("TSL8117" manufactured by Toshiba Silicone Co., Ltd.) was added, and the mixture was stirred for 8 hours. Then, toluene was distilled off under reduced pressure and dried at 120°C for 3 hours to obtain rutile-type titanium oxide fine particles surface-treated with methyl dimethoxysilane. 18 parts of rutile-type titanium oxide fine particles surface-treated with methyl dimethoxysilane, 4.5 parts of N-methoxymethylated nylon (trade name: Trezene EF-30T, manufactured by Nagase ChemteX), and 1.5 parts of a copolymer nylon resin (trade name: Amilan CM8000, manufactured by Toray) were added to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol to prepare a dispersion. This dispersion was subjected to a dispersion treatment for 6 hours using a vertical sand mill with 1.0 mm diameter glass beads. Subsequently, the liquid that had undergone the sand mill dispersion treatment was further subjected to a dispersion treatment for 1 hour using an ultrasonic disperser (UT-205, manufactured by Sharp) to prepare a coating liquid 9 for the undercoat layer. The output of the ultrasonic disperser was set to 100%. Also, no media such as glass beads were used in this milling treatment.

[0069] [Preparation Example of Coating Liquid 10 for Undercoat Layer] In the preparation example of coating liquid 1 for the undercoat layer, coating liquid 10 for the undercoat layer was prepared in the same manner as coating liquid 1 for the undercoat layer, except that methyl dimethoxylane was changed to vinyltrimethoxysilane (trade name: KBM-1003, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0070] [Preparation Example of Coating Liquid 11 for Undercoat Layer] In the preparation example of coating liquid 10 for the undercoat layer, coating liquid 11 for the undercoat layer was prepared in the same manner as coating liquid 10 for the undercoat layer, except that the sand mill dispersion treatment time was changed to 4 hours.

[0071] [Preparation Example of Coating Liquid 12 for Undercoat Layer] 18 parts of rutile-type titanium oxide fine particles (average primary particle size: 50 nm, manufactured by Tayca), 4.5 parts of N-methoxymethylated nylon (trade name: Trezene EF-30T, manufactured by Nagase ChemteX), and 1.5 parts of copolymerized nylon resin (trade name: Amilan CM8000, manufactured by Toray) were added to a mixed solvent of 90 parts of methanol and 60 parts of 1-butanol to prepare a dispersion. This dispersion was subjected to a dispersion treatment for 6 hours using a vertical sand mill with glass beads having a diameter of 1.0 mm. Subsequently, the liquid subjected to the sand mill dispersion treatment was further subjected to a dispersion treatment for 1 hour using an ultrasonic disperser (UT-205, manufactured by Sharp) to prepare a coating liquid 12 for the undercoat layer. The output of the ultrasonic disperser was set to 100%. Also, in this milling treatment, media such as glass beads were not used.

[0072] [Preparation Example of Coating Liquid 13 for Undercoat Layer] A coating liquid 13 for the undercoat layer was prepared in the same manner as the coating liquid 3 for the undercoat layer, except that ultrasonic dispersion was not carried out in the preparation example of the coating liquid 3 for the undercoat layer.

[0073] [Preparation Example of Coating Liquid 14 for Undercoat Layer] A coating liquid 14 for the undercoat layer was prepared in the same manner as the coating liquid 3 for the undercoat layer, except that the sand mill dispersion treatment time was changed to 15 hours in the preparation example of the coating liquid 3 for the undercoat layer.

[0074] [Preparation Example of Coating Liquid 15 for Undercoat Layer] A coating liquid 15 for the undercoat layer was prepared in the same manner as the coating liquid 5 for the undercoat layer, except that ultrasonic dispersion was not carried out in the preparation example of the coating liquid 5 for the undercoat layer.

[0075] [Preparation Example of Coating Liquid 16 for Undercoat Layer] A coating liquid 16 for the undercoat layer was prepared in the same manner as the coating liquid 7 for the undercoat layer, except that ultrasonic dispersion was not carried out in the preparation example of the coating liquid 7 for the undercoat layer.

[0076] [Preparation Example of Coating Liquid 17 for Undercoat Layer] In the preparation example of the coating liquid 7 for the undercoat layer, the coating liquid 17 for the undercoat layer was prepared in the same manner as the coating liquid 7 for the undercoat layer, except that the sand mill dispersion treatment time was changed to 15 hours.

[0077] [Synthesis of Phthalocyanine Pigment] [Synthesis Example 1] Under a nitrogen flow atmosphere, 5.46 parts of orthophthalonitrile and 45 parts of α-chloronaphthalene were charged into a reaction kettle, and then heated to raise the temperature to 30 °C and maintained at this temperature. Next, 3.75 parts of gallium trichloride were added at this temperature (30 °C). The moisture concentration of the mixed solution at the time of addition was 150 ppm. Then, the temperature was raised to 200 °C. Next, after reacting for 4.5 hours at 200 °C under a nitrogen flow atmosphere, it was cooled, and the product was filtered when the temperature reached 150 °C. The obtained filtrate was dispersed and washed at 140 °C for 2 hours using N,N-dimethylformamide and then filtered. The obtained filtrate was washed with methanol and then dried to obtain chlorogallium phthalocyanine pigment with a yield of 71%.

[0078] [Synthesis Example 2] 4.65 parts of the chlorogallium phthalocyanine pigment obtained in Synthesis Example 1 was dissolved in 139.5 parts of concentrated sulfuric acid at 10 °C, and while stirring, it was dropped into 620 parts of ice water for reprecipitation, and then filtered under reduced pressure using a filter press. At this time, No. 5C (manufactured by Advantec) was used as the filter. The obtained wet cake (filtrate) was dispersed and washed with 2% aqueous ammonia for 30 minutes and then filtered using a filter press. Next, the obtained wet cake (filtrate) was dispersed and washed with ion-exchanged water, and the filtration using a filter press was repeated 3 times. Finally, freeze-drying was performed to obtain a hydroxygallium phthalocyanine pigment with a solid content of 23% (hydrous hydroxygallium phthalocyanine pigment) with a yield of 97%.

[0079] [Synthesis Example 3] 6.6 kg of the water-containing hydroxygallium phthalocyanine pigment obtained in Synthesis Example 2 was dried as follows using a hyper-dryer (trade name: HD-06R, frequency (oscillation frequency): 2455 MHz ± 15 MHz, manufactured by Nippon Bio-Con). The hydroxygallium phthalocyanine pigment was placed on a dedicated circular plastic tray in a solidified state as taken out from a filter press (water-containing cake thickness 4 cm or less), with the far-infrared off and the temperature of the inner wall of the dryer set to 50°C. During microwave irradiation, the vacuum pump and leak valve were adjusted to adjust the degree of vacuum to 4.0 to 10.0 kPa. First, as the first step, 4.8 kW of microwaves were irradiated on the hydroxygallium phthalocyanine pigment for 50 minutes. Next, the microwaves were turned off once and the leak valve was closed once to create a high vacuum of 2 kPa or less. The solid content of the hydroxygallium phthalocyanine pigment at this point was 88%. As the second step, the leak valve was adjusted to adjust the degree of vacuum (pressure inside the dryer) within the above set value (4.0 to 10.0 kPa). Then, 1.2 kW of microwaves were irradiated on the hydroxygallium phthalocyanine pigment for 5 minutes, and again the microwaves were turned off once and the leak valve was closed once to create a high vacuum of 2 kPa or less. This second step was repeated one more time (for a total of 2 times). The solid content of the hydroxygallium phthalocyanine pigment at this point was 98%. Further, as the third step, microwave irradiation was performed in the same manner as the second step except that the output of the microwaves in the second step was changed from 1.2 kW to 0.8 kW. This third step was repeated one more time (for a total of 2 times). Further, as the fourth step, the leak valve was adjusted to repressurize the degree of vacuum (pressure inside the dryer) within the above set value (4.0 to 10.0 kPa). Then, 0.4 kW of microwaves were irradiated on the hydroxygallium phthalocyanine pigment for 3 minutes, and again the microwaves were turned off once and the leak valve was closed once to create a high vacuum of 2 kPa or less. This fourth step was repeated 7 more times (for a total of 8 times). In total, in 3 hours, 1.52 kg of a hydroxygallium phthalocyanine pigment (crystal) with a water content of 1% or less was obtained.

[0080] [Synthesis Example 4] In an atmosphere of nitrogen flow, 10 g of gallium trichloride and 29.1 g of ortho-phthalonitrile were added to 100 mL of α-chloronaphthalene, and after reacting at 200 °C for 24 hours, the product was filtered. The obtained wet cake was heated and stirred at 150 °C for 30 minutes using N,N-dimethylformamide, and then filtered. The obtained filtrate was washed with methanol and then dried to obtain a chlorogallium phthalocyanine pigment in a yield of 83%. 2 parts of the chlorogallium phthalocyanine pigment obtained by the above method was dissolved in 50 parts of concentrated sulfuric acid, stirred for 2 hours, and then dropped into a mixed solution of 170 mL of distilled water and 66 mL of concentrated aqueous ammonia that had been ice-cooled for reprecipitation. This was thoroughly washed with distilled water and dried to obtain 1.8 parts of a hydroxygallium phthalocyanine pigment.

[0081] [Preparation Example of Coating Liquid 1 for Charge Generation Layer] 1 part of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 3, 9 parts of N-methylformamide (product code: F0059, manufactured by Tokyo Chemical Industry Co., Ltd.), and 15 parts of glass beads with a diameter of 0.9 mm were milled at a cooling water temperature of 18 °C for 70 hours using a sand mill (K-800, manufactured by Igarashi Machinery Manufacturing Co., Ltd. (currently Imex), disk diameter 70 mm, number of disks 5). At this time, it was carried out under the condition that the disk rotated 400 times per minute. After adding 30 parts of N-methylformamide to the liquid thus treated, it was filtered, and the filtrate on the filter was thoroughly washed with tetrahydrofuran. Then, the washed filtrate was vacuum dried to obtain 0.45 part of a hydroxygallium phthalocyanine pigment. The obtained pigment had peaks at Bragg angles 2θ of 7.5° ± 0.2°, 9.9° ± 0.2°, 16.2° ± 0.2°, 18.6° ± 0.2°, 25.2° ± 0.2° and 28.3° ± 0.2° in the X-ray diffraction spectrum (Figure 1) using CuKα radiation. Also, the content of the amide compound (N-methylformamide) represented by the above formula (A1) in the hydroxygallium phthalocyanine crystal particles estimated by 1H-NMR measurement was 1.5 mass% with respect to the content of hydroxygallium phthalocyanine. Subsequently, 25 parts of hydroxygallium phthalocyanine pigment obtained by milling, 5 parts of polyvinyl butyral (trade name: Esrec BX-1, manufactured by Sekisui Chemical Co., Ltd.), and 190 parts of cyclohexanone were placed in a centrifugation container and centrifuged at a set temperature of 18°C for 30 minutes using a high-speed cooling centrifuge (trade name: himac CR22G, manufactured by Hitachi Koki Co., Ltd.). At this time, a rotor with the trade name: R14A (manufactured by Hitachi Koki Co., Ltd.) was used, and the acceleration and deceleration were carried out under the condition of rotating 1,800 times per minute in the shortest time. The supernatant after this centrifugation was quickly collected in another centrifugation container. The solution thus obtained was centrifuged again in the same manner as above except that the condition was set to rotate 8,000 times per minute, and the solution remaining after removing the supernatant after centrifugation was quickly collected in another sample bottle. The weight ratio of the hydroxygallium phthalocyanine pigment to polyvinyl butyral in the solution thus obtained was determined by 1H-NMR measurement. In addition, the solid content of the obtained solution was determined by a method of drying it for 30 minutes using a dryer set at 150°C and measuring the weight difference before and after drying. Subsequently, polyvinyl butyral (trade name: Esrec BX-1, manufactured by Sekisui Chemical Co., Ltd.) and cyclohexanone were added to the solution obtained by the centrifugation treatment so that the weight ratio of the hydroxygallium phthalocyanine pigment, polyvinyl butyral, and cyclohexanone was 20:10:190. 220 parts of this solution and 482 parts of glass beads with a diameter of 0.9 mm were dispersed at a cooling water temperature of 18°C for 4 hours using a sand mill (K-800, manufactured by Igarashi Machinery Manufacturing (currently Imex), disk diameter 70 mm, number of disks 5). At this time, the disk was rotated at a rate of 1,800 revolutions per minute. 444 parts of cyclohexanone and 634 parts of ethyl acetate were added to this dispersion to prepare coating solution 1 for the charge generation layer.

[0082] The measurement of the hydroxygallium phthalocyanine pigment in the present invention by small-angle X-ray scattering was evaluated according to the following procedure. Cyclohexanone was added to the prepared coating solution 1 for the charge generation layer and diluted until the concentration of the charge generation material became 1 wt.% to obtain a measurement sample. Using a Rigaku multi-purpose X-ray diffractometer SmartLab, small-angle X-ray scattering measurement (X-ray wavelength: 0.154 nm) was performed to obtain the results. The scattering profile obtained from the measurement was analyzed using particle size analysis software NANO-Solver to obtain the particle size distribution. The particle shape was assumed to be spherical. As a result of the measurement, as shown in Table 1, the obtained pigment had a peak at the position of 32 nm in the crystallite size distribution measured using small-angle X-ray scattering, and the full width at half maximum of the peak was 38 nm.

[0083] [Preparation Example of Coating Liquid 2 for Charge Generation Layer] A coating liquid 2 for the charge generation layer was prepared in the same manner as the coating liquid 1 for the charge generation layer, except that the milling treatment for 70 hours in a sand mill was changed to 10 hours. The pigment obtained before the centrifugation treatment had peaks at Bragg angles 2θ of 7.5° ± 0.2°, 9.9° ± 0.2°, 16.2° ± 0.2°, 18.6° ± 0.2°, 25.2° ± 0.2° and 28.3° ± 0.2° in the X-ray diffraction spectrum using CuKα radiation. Also, 1 The content of the amide compound (N-methylformamide) represented by the above formula (A1) in the hydroxygallium phthalocyanine crystal particles estimated by 1H-NMR measurement was 2.7% by mass based on the content of hydroxygallium phthalocyanine. As shown in Table 1, the obtained pigment had a peak at the position of 45 nm in the crystallite size distribution measured using small-angle X-ray scattering, and the full width at half maximum of the peak was 44 nm.

[0084] [Preparation Example of Coating Liquid 3 for Charge Generation Layer] A coating liquid 3 for the charge generation layer was prepared in the same manner as the coating liquid 1 for the charge generation layer, except that the milling treatment for 70 hours in a sand mill was changed to 30 hours. The pigment obtained before the centrifugation treatment has peaks at Bragg angles 2θ of 7.5° ± 0.2°, 9.9° ± 0.2°, 16.2° ± 0.2°, 18.6° ± 0.2°, 25.2° ± 0.2° and 28.3° ± 0.2° in the X-ray diffraction spectrum using CuKα rays. Also, 1 The content of the amide compound (N-methylformamide) represented by the above formula (A1) in the hydroxygallium phthalocyanine crystal particles estimated by 1H-NMR measurement was 2.0% by mass based on the content of hydroxygallium phthalocyanine. Also, as shown in Table 1, the obtained pigment had a peak at the position of 38 nm in the crystallite size distribution measured using small-angle X-ray scattering, and the half-width at half maximum of the peak was 41 nm.

[0085] [Preparation Example of Coating Liquid 4 for Charge Generation Layer] In the preparation example of the coating liquid 1 for the charge generation layer, the coating liquid 4 for the charge generation layer was prepared in the same manner as the coating liquid 1 for the charge generation layer, except that the milling treatment for 70 hours with a sand mill was changed to 100 hours. The pigment obtained before the centrifugation treatment has peaks at Bragg angles 2θ of 7.5° ± 0.2°, 9.9° ± 0.2°, 16.2° ± 0.2°, 18.6° ± 0.2°, 25.2° ± 0.2° and 28.3° ± 0.2° in the X-ray diffraction spectrum using CuKα rays. Also, 1 The content of the amide compound (N-methylformamide) represented by the above formula (A1) in the hydroxygallium phthalocyanine crystal particles estimated by 1H-NMR measurement was 1.0% by mass based on the content of hydroxygallium phthalocyanine. Also, as shown in Table 1, the obtained pigment had a peak at the position of 30 nm in the crystallite size distribution measured using small-angle X-ray scattering, and the half-width at half maximum of the peak was 35 nm.

[0086] [Preparation Example of Coating Liquid 5 for Charge Generation Layer] In the preparation example of the coating liquid 1 for the charge generation layer, except that the hydroxygallium phthalocyanine pigment obtained by the milling treatment was changed as follows, the coating liquid 5 for the charge generation layer was prepared in the same manner as the coating liquid 1 for the charge generation layer. 1 part of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 3, 9 parts of N,N-dimethylformamide (product code: D0722, manufactured by Tokyo Chemical Industry Co., Ltd.), and 15 parts of glass beads with a diameter of 0.9 mm were subjected to milling treatment at a cooling water temperature of 18 °C for 30 hours using a sand mill (K-800, manufactured by Igarashi Machinery Manufacturing Co., Ltd. (currently Aimax), disk diameter 70 mm, number of disks 5). At this time, the treatment was carried out under the condition that the disk rotated 600 times per minute. The liquid thus treated was filtered through a filter (product number: N-NO.125T, pore diameter: 133 μm, manufactured by NBC Mesh Tech Co., Ltd.) to remove the glass beads. After adding 30 parts of N,N-dimethylformamide to this liquid, it was filtered, and the filtrate on the filter was thoroughly washed with tetrahydrofuran. Then, the washed filtrate was vacuum dried to obtain 0.45 part of the hydroxygallium phthalocyanine pigment. The pigment obtained before the centrifugation treatment has peaks at Bragg angles 2θ of 7.5° ± 0.2°, 9.9° ± 0.2°, 16.2° ± 0.2°, 18.6° ± 0.2°, 25.2° ± 0.2°, and 28.3° ± 0.2° in the X-ray diffraction spectrum using CuKα radiation. Also, as shown in Table 1, the obtained pigment has a peak at a position of 45 nm in the crystal size distribution measured using small-angle X-ray scattering, and the half-width at half maximum of the peak is 47 nm.

[0087] [Preparation Example of Coating Liquid 6 for Charge Generation Layer] In the preparation example of the coating liquid 5 for the charge generation layer, except that the milling treatment for 30 hours with a sand mill was changed to 50 hours, the coating liquid 6 for the charge generation layer was prepared in the same manner as the coating liquid 5 for the charge generation layer. The pigment obtained before the centrifugation treatment has peaks at Bragg angles 2θ of 7.5° ± 0.2°, 9.9° ± 0.2°, 16.2° ± 0.2°, 18.6° ± 0.2°, 25.2° ± 0.2°, and 28.3° ± 0.2° in the X-ray diffraction spectrum using CuKα radiation. Also, as shown in Table 1, the obtained pigment had a peak at the position of 41 nm in the crystallite size distribution measured using small-angle X-ray scattering, and the full width at half maximum of the peak was 46 nm.

[0088] [Preparation Example of Coating Liquid 7 for Charge Generation Layer] In Coating Liquid 2 for Charge Generation Layer, Coating Liquid 7 for Charge Generation Layer was prepared in the same manner as Coating Liquid 2 for Charge Generation Layer, except that centrifugation was not performed. The obtained pigment 1 The content of the amide compound (N-methylformamide) represented by the above formula (A1) in the hydroxygallium phthalocyanine crystal particles estimated by 1H-NMR measurement was 2.7% by mass based on the content of hydroxygallium phthalocyanine. Also, as shown in Table 1, the obtained pigment had a peak at the position of 43 nm in the crystallite size distribution measured using small-angle X-ray scattering, and the full width at half maximum of the peak was 55 nm.

[0089] [Preparation Example of Coating Liquid 8 for Charge Generation Layer] In the preparation example of Coating Liquid 5 for Charge Generation Layer, Coating Liquid 8 for Charge Generation Layer was prepared in the same manner as Coating Liquid 5 for Charge Generation Layer, except that the milling treatment with a sand mill for 30 hours was changed to 10 hours. The pigment obtained before centrifugation had peaks at Bragg angles 2θ of 7.5° ± 0.2°, 9.9° ± 0.2°, 16.2° ± 0.2°, 18.6° ± 0.2°, 25.2° ± 0.2° and 28.3° ± 0.2° in the X-ray diffraction spectrum using CuKα radiation. Also, as shown in Table 1, the obtained pigment had a peak at the position of 55 nm in the crystallite size distribution measured using small-angle X-ray scattering, and the full width at half maximum of the peak was 48 nm.

[0090] [Preparation Example of Coating Liquid 9 for Charge Generation Layer] In Coating Liquid 5 for Charge Generation Layer, Coating Liquid 9 for Charge Generation Layer was prepared in the same manner as Coating Liquid 5 for Charge Generation Layer, except that centrifugation was not performed. As shown in Table 1, the obtained pigment had a peak at 53 nm in the crystallite size distribution measured using small-angle X-ray scattering, and the full width at half maximum of the peak was 60 nm.

[0091] [Preparation Example of Coating Liquid 10 for Charge Generation Layer] In the preparation example of coating liquid 1 for the charge generation layer, except that the process of obtaining the hydroxygallium phthalocyanine pigment was changed as follows, coating liquid 9 for the charge generation layer was prepared in the same manner as coating liquid 1 for the charge generation layer. 0.5 part of the hydroxygallium phthalocyanine pigment obtained in Synthesis Example 4, 7.5 parts of N,N-dimethylformamide (product code: D0722, manufactured by Tokyo Chemical Industry Co., Ltd.), and 29 parts of glass beads with a diameter of 0.9 mm were milled with a ball mill at a temperature of 25 °C for 24 hours. At this time, a standard bottle (product name: PS-6, manufactured by Kashiwa Glass Co., Ltd.) was used as the container, and the operation was carried out under the condition that the container rotated 60 times per minute. The liquid thus treated was filtered through a filter (product number: N-NO.125T, pore diameter: 133 μm, manufactured by NBC Mesh Tech Co., Ltd.) to remove the glass beads. After adding 30 parts of N,N-dimethylformamide to this liquid, it was filtered, and the filtrate on the filter was thoroughly washed with n-butyl acetate. Then, the washed filtrate was vacuum dried to obtain 0.45 part of the hydroxygallium phthalocyanine pigment. As shown in Table 1, in the crystallite size distribution of the obtained pigment measured using small-angle X-ray scattering, a peak was present at 60 nm, and the full width at half maximum of the peak was 59 nm.

[0092] [Example 1] [Support] An aluminum cylinder with a diameter of 30 mm and a length of 260.5 mm was used as the support (cylindrical support).

[0093] [Conductive Layer] As the substrate, anatase-type titanium oxide with an average primary particle size of 200 nm was used, and titanium was 33.7 parts in terms of TiO 2 conversion, and niobium was Nb 2 O 5A titanium niobium sulfate solution containing 2.9 parts by conversion was prepared. 100 parts of the substrate was dispersed in pure water to form a 1000-part suspension, which was heated to 60 °C. The titanium niobium sulfate solution and 10 mol / L sodium hydroxide were added dropwise to the suspension over 3 hours so that the pH of the suspension became 2 - 3. After the total amount was added dropwise, the pH was adjusted to near neutral, and a polyacrylamide-based flocculant was added to precipitate 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 at 750 °C for 1 hour in nitrogen and then at 450 °C in air to produce titanium oxide fine particles 1. The obtained particles had an average particle size (average primary particle size) of 220 nm in the particle size measurement method using a scanning electron microscope. Subsequently, 50 parts of a phenol resin (monomer / oligomer of phenol resin) (trade name: Pryophen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g / cm 2 ) was dissolved in 35 parts of 1-methoxy-2-propanol as a solvent to obtain a solution. 60 parts of titanium oxide fine particles 1 was added to this solution, and the mixture was placed in a vertical sand mill using 120 parts of glass beads with an average particle size of 1.0 mm as a dispersion medium, and subjected to a dispersion treatment for 4 hours under the conditions of a dispersion liquid temperature of 23 ± 3 °C and a rotation speed of 1500 rpm (circumferential speed 5.5 m / s) to obtain a dispersion liquid. The glass beads were removed from this dispersion liquid with a mesh. To the dispersion liquid after removing the glass beads, 0.01 part of silicone oil (trade name: SH28 PAINT ADDITIVE, manufactured by Toray Dow Corning) as a leveling agent and 8 parts of silicone resin particles (trade name: KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., average particle size: 2 μm, density: 1.3 g / cm 3 ) were added and stirred, and a conductive layer coating solution was prepared by pressure filtration using a PTFE filter paper (trade name: PF060, manufactured by Advantec Toyo). The conductive layer coating solution thus prepared was dip-coated on the above-mentioned support to form a coating film, and the coating film was heated and cured at 150 °C for 20 minutes to form a conductive layer with a film thickness of 17 μm.

[0094] <Undercoat layer> The undercoat layer coating liquid prepared according to the above-described preparation example of the undercoat layer coating liquid 1 was dip-coated on the above-described conductive layer to form a coating film, and the coating film was heated and dried at a temperature of 100 ° C for 10 minutes to form an undercoat layer with a film thickness of 2 μm. Table 1 shows the arithmetic mean roughness Ra in JIS B0601:2001, and the average length Rsm of the roughness curve elements and Ra / Rsm of the obtained undercoat layer.

[0095] Note that the surface roughness of the undercoat layer in the present invention was evaluated according to the following procedure. The charge transport layer of the produced electrophotographic photoreceptor was dissolved with toluene and dried to expose the surface of the charge generation layer. Next, the exposed charge generation layer of the electrophotographic photoreceptor was dissolved with cyclohexanone and dried to expose the surface of the undercoat layer. Further, the electrophotographic photoreceptor with the surface of the undercoat layer exposed was cut out into a square shape with a side length of about 5 mm to obtain a measurement sample. Using a scanning probe microscope JSPM-5200 manufactured by JEOL Ltd., height information was obtained in a square region with a side length of 500 nm on the surface of the undercoat layer. For the measurement, a cantilever NCR manufactured by NanoWorld was used, and height information was obtained by scanning the surface in tapping mode. From the obtained height information, the arithmetic mean roughness Ra in JIS B0601:2001, and the average length Rsm of the roughness curve elements and Ra / Rsm were calculated.

[0096] <Charge generation layer> The charge generation layer coating liquid prepared according to the above-described preparation example of the charge generation layer coating liquid 1 was dip-coated on the above-described undercoat layer to form a coating film, and the coating film was heated and dried at a temperature of 100 ° C for 10 minutes to form a charge generation layer with a film thickness of 0.2 μm.

[0097] <Charge transport layer> As the charge transport material, 5.4 parts of a triarylamine compound represented by the following formula (B-1), [Chemical formula] 3.6 parts of a triarylamine compound represented by the following formula (B-2), [Chemical formula] 10 parts of polycarbonate (trade name: Iupilon Z-400, manufactured by Mitsubishi Engineering-Plastics Corporation) was dissolved in a mixed solvent of 25 parts of ortho-xylene / 25 parts of methyl benzoate / 25 parts of dimethoxymethane to prepare a coating solution for the charge transport layer. The coating solution for the charge transport layer thus prepared was dip-coated on the above-described charge generation layer to form a coating film, and the coating film was heated and dried at a temperature of 120 ° C for 30 minutes to form a charge transport layer having a film thickness of 14 μm.

[0098] [Protective layer] 9.6 parts of a polymerizable compound represented by the following formula (B-3), [Chemical formula] 14.4 parts of a polymerizable compound represented by the following formula (B-4), [Chemical formula] 1.2 parts of a siloxane-modified acrylic compound (CYMEL US270, manufactured by Toagosei Co., Ltd.) was mixed with a mixed solvent of 42 parts of cyclohexane and 18 parts of 1-propanol and stirred. Thus, a coating solution for the protective layer was prepared. This coating solution for the protective layer was dip-coated on the charge transport layer to form a coating film, and the obtained coating film was dried at 35 ° C for 4 minutes. Then, in a nitrogen atmosphere, with the distance between the support (the irradiated object) and the electron beam irradiation window being 25 mm under the conditions of an acceleration voltage of 57 kV and a beam current of 5.3 mA, the support (the irradiated object) was rotated at a speed of 300 rpm, and the coating film was irradiated with an electron beam for 4.8 seconds. When the absorbed dose of the electron beam at this time was measured, it was 20 kGy. Then, in a nitrogen atmosphere, the temperature was raised from 25 ° C to 137 ° C over 10 seconds to heat the coating film. The oxygen concentration from the electron beam irradiation to the subsequent heat treatment was 10 ppm or less. Next, in the air, it was naturally cooled until the temperature of the coating film reached 25 ° C, and heat treatment was performed for 10 minutes under the condition that the temperature of the coating film reached 100 ° C to form a protective layer having a film thickness of 1.9 μm.

[0099] [Examples 2 to 21] An electrophotographic photoreceptor was manufactured in the same manner as in Example 1, except that the coating liquid for the undercoat layer and the film thickness of the undercoat layer, and the coating liquid for the charge generation layer and the film thickness of the charge generation layer in Example 1 were changed as shown in Table 1. The arithmetic mean roughness Ra in JIS B0601:2001, the average length Rsm of the roughness curve elements, and Ra / Rsm of the obtained undercoat layer are shown in Table 1.

[0100] [Comparative Examples 1 to 9] An electrophotographic photoreceptor was manufactured in the same manner as in Example 1, except that the coating liquid for the undercoat layer and the film thickness of the undercoat layer, and the coating liquid for the charge generation layer and the film thickness of the charge generation layer in Example 1 were changed as shown in Table 1. The arithmetic mean roughness Ra in JIS B0601:2001, the average length Rsm of the roughness curve elements, and Ra / Rsm of the obtained undercoat layer are shown in Table 1.

[0101]

Table 1

[0102] [Evaluation of Electrophotographic Photoreceptor] The following evaluations were performed on the electrophotographic photoreceptors prepared in Examples 1 to 21 and Comparative Examples 1 to 9. The results are shown in Table 2.

[0103] <Initial Potential and Potential after 10,000 Cycles of Durability> As an electrophotographic apparatus for evaluation, a monochrome direct transfer type printer was adopted. A modified machine of a laser beam printer (trade name: HP LaserJet Enterprise M612dn) manufactured by Hewlett-Packard was used. As the modification points, the voltage applied to the charging roller was adjusted and measured, and the image exposure light amount was adjusted and measured. First, the image forming apparatus and the electrophotographic photoreceptor were left in an environment of a temperature of 15°C and a relative humidity of 10% RH for 24 hours or more, and then the electrophotographic photoreceptors of Examples 1 to 21 and Comparative Examples 1 to 9 were mounted on the cartridge of the image forming apparatus. As an evaluation of repeated use, image output using a test chart with a printing ratio of 1% was continuously performed 10,000 times on A4-sized plain paper. As the charging condition, the dark part potential was -500 V, and as the exposure condition, the image exposure light amount was adjusted to 0.2 μJ / cm 2 2. Before and after the above repeated use, the bright part potential (Vl) was evaluated. The surface potential of the photoreceptor was measured by modifying the cartridge and attaching a potential probe (product name: model6000B-8, manufactured by Trek Japan Co., Ltd.) at the development position. The potential was measured using a surface potentiometer (product name: model344, manufactured by Trek Japan Co., Ltd.). From the results in Table 2, in Examples 1 to 21, the potential difference between the initial potential and the potential after 10,000 cycles of durability was 16 V or less, while in Comparative Examples 1 to 9, the potential difference between the initial potential and the potential after 10,000 cycles of durability was 20 V or more.

[0104] <Transfer Memory> As an electrophotographic apparatus for evaluation, a monochrome direct transfer type printer was adopted. A laser beam printer (product name: HP LaserJet Enterprise M612dn) manufactured by Hewlett-Packard was prepared, and the applied voltage to the charging roller, the adjustment of the applied voltage to the transfer roller and the image exposure amount, the adjustment of the pre-exposure amount, and the transfer bias control in the intersheet part were modified so as to be disabled. Furthermore, a high-voltage power supply (Model615-3, manufactured by Trek Japan) was connected to the transfer roller, and the apparatus was modified so that a voltage could be applied to the transfer roller from outside the LBP. First, the image forming apparatus and the electrophotographic photoreceptor were left in an environment of a temperature of 23°C and a relative humidity of 50% RH for 24 hours or more, and then the electrophotographic photoreceptors prepared in Examples 1 to 21 and Comparative Examples 1 to 9 were attached to the cartridge of the image forming apparatus. The charging voltage applied to the charging roller and the image exposure amount to the electrophotographic photoreceptor were set so that the dark potential was -500 V and the bright potential was -100 V. Pre-exposure was not used. For measuring the surface potential of the electrophotographic photoreceptor during potential setting, a device with a potential probe (product name: model6000B-8, manufactured by Trek Japan) attached to the development position of the process cartridge was used, and it was measured using a surface electrometer (product name: model344, manufactured by Trek Japan). Also, the voltage applied to the transfer roller during image formation was set to +3000 V using an external power supply. Next, two consecutive A4-sized plain papers with a halftone image of 1 dot 4 spaces were output. There is paper during the transfer of the first sheet, but the electrophotographic photoreceptor and the transfer roller are in direct contact between the first and second sheets. A black spot appears at the tip of the second sheet due to the influence of the memory received in the space between the transfer papers. The transfer memory was evaluated based on the following criteria by visually observing the black spots in the output image. · Rank A: There is no transfer memory. · Rank B: There is transfer memory, but it is not noticeable. · Rank C: There is transfer memory and it is noticeable. · Rank D: The degree of transfer memory is severe and it is in a black band shape.

[0105]

Table 2

Explanation of Symbols

[0106] 101: Conductive substrate 102: Undercoat layer 103: Charge generation layer 104: Hole transport layer 105: Photosensitive layer 1: Electrophotographic photoreceptor 2: Shaft 3: Charging means 4: Image exposure light 5: Developing means 6: Transfer means 7: Transfer material 8: Image fixing means 9: Cleaning means 10: Front exposure light 11: Process cartridge 12: Guide means

Claims

1. An electrophotographic photoreceptor having a support, an undercoat layer, a charge generation layer, and a charge transport layer containing a charge transport material, in this order, wherein the undercoat layer contains a polyamide resin and titanium oxide fine particles, the arithmetic mean roughness Ra and the mean length Rs of the roughness curve elements on the surface of the undercoat layer satisfy the following formulas (A) and (B) according to JIS B0601:2001, Ra ≤ 50 nm Formula (A) 0.1 ≤ Ra / Rsm ≤ 0.5 Formula (B) the charge generation layer contains a hydroxygallium phthalocyanine pigment, the hydroxygallium phthalocyanine pigment has crystalline particles of a crystal form showing peaks at Bragg angles 2θ of 7.4° ± 0.3° and 28.2° ± 0.3° in an X-ray diffraction spectrum using CuKα rays, and in the size distribution of the crystal particles measured using small-angle X-ray scattering, there is a peak in the range of 20 nm or more and 50 nm or less, and the half-value width of the peak is 50 nm or less An electrophotographic photoreceptor characterized by the above.

2. The electrophotographic photoreceptor according to claim 1, wherein the arithmetic mean roughness Ra is 30 nm or less.

3. The electrophotographic photoreceptor according to claim 1 or 2, wherein the average primary particle diameter of the titanium oxide fine particles is 10 nm or more and 100 nm or less.

4. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the average primary particle diameter of the titanium oxide fine particles is 30 nm or more and 60 nm or less.

5. The electrophotographic photoreceptor according to any one of claims 1 to 4, wherein the film thickness of the undercoat layer is 0.5 μm or more and 3.0 μm or less.

6. The electrophotographic photoreceptor according to claim 1, wherein the film thickness of the charge generation layer is 0.15 μm or more.

7. A process cartridge integrally supporting the electrophotographic photoreceptor according to any one of claims 1 to 6 and at least one means selected from the group consisting of charging means, developing means, transferring means, and cleaning means, and being detachable from the main body of an electrophotographic apparatus.

8. An electrophotographic apparatus comprising the electrophotographic photoreceptor according to any one of claims 1 to 6, and charging means, exposure means, developing means, and transferring means.

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