Electrophotographic photoreceptor, method for manufacturing electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

An electrophotographic photoreceptor, a method of manufacturing the electrophotographic photoreceptor, a process cartridge, and an image forming apparatus, the electrophotographic photoreceptor including a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, in a power spectrum obtained by performing a fast Fourier transform on a roughness curve in the axial direction of the outer peripheral surface of the conductive substrate, the integrated value of the intensity in the period range of 0.01-0.1 mm is 0.02-0.10, and the layer thickness of the undercoat layer is 10 [mu] m or more.

Description

Technical Field

[0001] The present invention relates to an electronic photographic photosensitive body, a method for manufacturing the electronic photographic photosensitive body, a processing box and an image forming device. Background Art

[0002] Patent document 1 discloses an electronic photographic photosensitive body having a photosensitive layer on a substrate, wherein the coefficient of determination of the regression line of a data group with a relative cumulative frequency distribution curve of 10% to 50% obtained by performing a fast Fourier transform on a data group representing the height of a surface roughness curve of the substrate is greater than 0.970, the spacing at which the relative cumulative frequency reaches 90% is less than 200 μm, and the root mean square tilt RΔq specified in JIS B0601:2001 obtained from the roughness curve is greater than 0.08.

[0003] Patent document 2 discloses a substrate for an electronic photographic photosensitive body, wherein a cross-sectional curve specified in JIS B0601 is obtained for the surface state of a component for an image forming apparatus, and a multi-resolution analysis is performed on a position data string in the direction of surface roughness at equally spaced positions on the cross-sectional curve. The surface roughness evaluation method for components for an image forming apparatus is used to evaluate the state of the surface roughness based at least on the result.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2019-095510

[0005] Patent Document 2: Japanese Patent Application Publication No. 2007-292772 Summary of the invention

[0006] An object of the present invention is to provide an electrophotographic photoreceptor that forms an image with excellent granularity compared with an electrophotographic photoreceptor in which the thickness of an undercoat layer is less than 10 μm and the undercoat layer does not contain metal oxide particles.

[0007] Specific means for solving the above-mentioned problems include the following aspects.

[0008] <1> An electrophotographic photoreceptor comprising a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, wherein:

[0009] In a power spectrum obtained by fast Fourier transforming a roughness curve in the axial direction of the outer peripheral surface of the conductive substrate, the integrated value of the intensity in the range of a period of 0.01 mm to 0.1 mm is 0.02 to 0.10.

[0010] The undercoat layer has a thickness of 10 μm or more.

[0011] <2> The electrophotographic photoreceptor according to <1>, wherein

[0012] The undercoat layer has a thickness of 20 μm or more.

[0013] <3> An electrophotographic photoreceptor comprising a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, wherein:

[0014] In a power spectrum obtained by fast Fourier transforming a roughness curve in the axial direction of the outer peripheral surface of the conductive substrate, the integrated value of the intensity in the range of a period of 0.01 mm to 0.1 mm is 0.02 to 0.10.

[0015] The undercoat layer contains metal oxide particles.

[0016] <4> The electrophotographic photoreceptor according to <3>, wherein

[0017] The metal oxide particles include at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, and tin oxide particles.

[0018] <5> The electrophotographic photoreceptor according to <3> or <4>, wherein

[0019] The metal oxide particles have an average particle size of 10 nm or more and 80 nm or less.

[0020] <6> The electrophotographic photoreceptor according to any one of <3> to <5>, wherein

[0021] The mass ratio of the metal oxide particles in the undercoat layer is 60 mass % or more and 95 mass % or less.

[0022] <7> A method for producing an electrophotographic photoreceptor, which is a method for producing the electrophotographic photoreceptor according to any one of <1> to <6>, the method for producing an electrophotographic photoreceptor comprising the following steps:

[0023] Regenerating the conductive substrate by removing all layers on the conductive substrate from the used electrophotographic photoreceptor by spraying water;

[0024] forming an undercoat layer on the regenerated conductive substrate; and

[0025] A photosensitive layer is formed on the undercoat layer.

[0026] <8> A process cartridge comprising the electrophotographic photoreceptor according to any one of <1> to <6>, wherein

[0027] The process cartridge is attachable to and detachable from the image forming apparatus.

[0028] <9> An image forming apparatus comprising:

[0029] The electrophotographic photoreceptor according to any one of <1> to <6>;

[0030] A charging device for charging the surface of the electrophotographic photoreceptor;

[0031] An electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

[0032] a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and

[0033] The transfer device transfers the toner image to the surface of a recording medium.

[0034] Effects of the Invention

[0035] According to <1>, there is provided an electrophotographic photoreceptor that forms an image having excellent granularity compared with an electrophotographic photoreceptor in which the thickness of the undercoat layer is less than 10 μm and the undercoat layer does not contain metal oxide particles.

[0036] According to <2>, there is provided an electrophotographic photoreceptor that forms an image having excellent graininess compared with an electrophotographic photoreceptor having an undercoat layer having a thickness of less than 20 μm.

[0037] According to <3>, <4>, <5> or <6>, there is provided an electrophotographic photoreceptor that forms an image having excellent granularity compared with an electrophotographic photoreceptor having an undercoat layer thickness of less than 10 μm and containing no metal oxide particles.

[0038] According to <7>, a method for producing an electrophotographic photoreceptor capable of forming an image having excellent granularity is provided.

[0039] According to <8>, there is provided a process cartridge for forming an image having excellent granularity compared with a process cartridge including an electrophotographic photoreceptor having an undercoat layer having a thickness of less than 10 μm and containing no metal oxide particles in the undercoat layer.

[0040] According to <9>, there is provided an image forming apparatus that forms an image with excellent granularity compared to an image forming apparatus including an electrophotographic photoreceptor having an undercoat layer having a thickness of less than 10 μm and containing no metal oxide particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0042] Figure 1is a partial cross-sectional view showing an example of a layer structure of an electrophotographic photoreceptor according to the present embodiment;

[0043] Figure 2 is a partial cross-sectional view showing another example of the layer structure of the electrophotographic photoreceptor involved in this embodiment;

[0044] Figure 3 is a schematic structural diagram showing an example of an image forming apparatus according to the present embodiment;

[0045] Figure 4 It is a schematic configuration diagram showing another example of the image forming apparatus according to the present embodiment.

[0046] Explanation of symbols

[0047] 1-conductive substrate, 2-undercoat layer, 3-charge generating layer, 4-charge transporting layer, 5-photosensitive layer, 10A-photoreceptor, 10B-photoreceptor, 7-electrophotographic photoreceptor, 8-charging device, 9-exposure device, 11-developing device, 13-cleaning device, 14-lubricant, 40-transfer device, 50-intermediate transfer body, 100-image forming device, 120-image forming device, 131-cleaning blade, 132-fibrous component (roller-shaped), 133-fibrous component (flat brush-shaped), 300-processing box. DETAILED DESCRIPTION

[0048] Hereinafter, embodiments of the present invention will be described. These descriptions and examples are intended to illustrate the embodiments and do not limit the scope of the embodiments.

[0049] In the present invention, a numerical range expressed using "to" indicates a range including the numerical values ​​before and after "to" as the minimum value and the maximum value, respectively.

[0050] In the numerical ranges recorded in stages in the present invention, the upper limit or lower limit recorded in one numerical range may also be replaced by the upper limit or lower limit of the numerical range recorded in other stages. In addition, in the numerical ranges recorded in the present invention, the upper limit or lower limit of the numerical range may also be replaced by the value shown in the embodiment.

[0051] In the present invention, the word "process" is included in this term if the purpose of the process can be achieved not only in an independent process but also in a case where the process cannot be clearly distinguished from other processes.

[0052] In the present invention, when the embodiments are described with reference to the drawings, the structure of the embodiments is not limited to the structure shown in the drawings. In addition, the sizes of the components in the drawings are conceptual, and the relative relationship between the sizes of the components is not limited thereto.

[0053] In the present invention, each component may also include a plurality of corresponding substances. In the present invention, when referring to the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, it indicates the total amount of the plurality of substances present in the composition.

[0054] In the present invention, multiple types of particles corresponding to each component may be contained. When multiple types of particles corresponding to each component are present in the composition, unless otherwise specified, the particle size of each component represents a value for a mixture of the multiple types of particles present in the composition.

[0055] In the present invention, unless otherwise specified, an alkyl group and an alkylene group include linear, branched, and cyclic groups.

[0056] In the present invention, regarding the organic group, aromatic ring, linking group, alkyl group, alkylene group, aryl group, aralkyl group, alkoxy group, aryloxy group and the like, the hydrogen atom in the group may be substituted by a halogen atom.

[0057] In the present invention, when a compound is represented by a structural formula, the structural formula may be represented by omitting the symbols (C and H) representing the carbon atoms and hydrogen atoms in the hydrocarbon group and / or hydrocarbon chain.

[0058] In the present invention, the "structural unit" of the copolymer or resin has the same meaning as the monomer unit.

[0059] In the present invention, the “axial direction” of the electrophotographic photoreceptor means the direction in which the rotation axis of the electrophotographic photoreceptor extends, and the “circumferential direction” of the electrophotographic photoreceptor means the rotation direction of the electrophotographic photoreceptor.

[0060] <Electronic Photographic Photoreceptor>

[0061] The electrophotographic photoreceptor (hereinafter also referred to as “photoreceptor”) according to the present embodiment includes a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer.

[0062] Figure 1 This is a partial cross-sectional view schematically showing an example of the layer structure of the photoreceptor according to the present embodiment. Figure 1 The photoreceptor 10A shown has a laminated photosensitive layer. The photoreceptor 10A has a structure in which an undercoat layer 2, a charge generating layer 3, and a charge transporting layer 4 are sequentially laminated on a conductive substrate 1, and the charge generating layer 3 and the charge transporting layer 4 constitute a photosensitive layer 5 (a so-called functional separation type photosensitive layer). The photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generating layer 3. The photoreceptor 10A may have a protective layer (not shown) on the charge transporting layer 4.

[0063] Figure 2This is a partial cross-sectional view schematically showing another example of the layer structure of the photoreceptor according to the present embodiment. Figure 2 The photoreceptor 10B shown has a single-layer photosensitive layer. The photoreceptor 10B has a structure in which an undercoat layer 2 and a photosensitive layer 5 are sequentially stacked on a conductive substrate 1. The photoreceptor 10B may have an intermediate layer (not shown) between the undercoat layer 2 and the photosensitive layer 5. The photoreceptor 10B may have a protective layer (not shown) on the photosensitive layer 5.

[0064] In the power spectrum obtained by fast Fourier transforming the roughness curve of the outer peripheral surface of the conductive substrate in the axial direction, the integrated value of the intensity in the range of period 0.01 mm to 0.1 mm is 0.02 to 0.10.

[0065] In the present invention, in the power spectrum obtained by fast Fourier transforming the roughness curve in the axial direction of the outer peripheral surface of the conductive substrate, the integrated value of the intensity in the range of a period of 0.01 mm to 0.1 mm is referred to as “integrated value S”.

[0066] The integrated value S is obtained by the following (1) to (4).

[0067] (1) All layers are removed from the photoreceptor to expose the outer peripheral surface of the conductive substrate.

[0068] The removal of each layer of the photoreceptor is performed by immersing the photoreceptor in an organic solvent that dissolves the binder resin of each layer but does not corrode the conductive substrate.

[0069] (2) The roughness curve of the outer peripheral surface of the conductive substrate in the axial direction is obtained. The roughness curve is a roughness curve specified in JIS B0601:2013.

[0070] In an environment with a temperature of 23°C and a relative humidity of 55%, a contact surface roughness tester (SURFCOM1400A, TOKYO SEIMITSU CO., LTD.) was used to measure the roughness of the outer peripheral surface of the conductive substrate. The conductive substrate was scanned along the axial direction at a scanning speed of 0.3mm / sec, a measuring length of 2.5mm, and a cutoff value of 0.8mm. The probe was a conical probe with a vertex angle of 90°, a radius of curvature of 5μm at the front end, and a front end material of diamond. There were three measuring locations, namely the central part in the axial direction and the two ends of the image forming area. The roughness curve was obtained based on the measured values ​​at the three locations.

[0071] (3) Perform fast Fourier transform on the roughness curve to derive the power spectrum.

[0072] Microsoft Excel was used as the analysis software. Parameters in the height direction of 4096 points were extracted from the roughness curve at 0.6 μm intervals. The 4096-point data were converted so that the average of the 4096-point height data was 0. Fast Fourier transform was performed on the 4096-point parameter values, and a power spectrum with the horizontal axis as period (mm) and the vertical axis as intensity was derived.

[0073] (4) Intensities in a range of a period of 0.01 mm to 0.1 mm in the power spectrum are integrated to obtain an integrated value S. The integrated value S is an integrated value of power spectrum values ​​in a range of 0.01 mm to 0.1 mm.

[0074] This embodiment provides a method of regenerating a conductive substrate from a used photoreceptor and reusing the regenerated conductive substrate. As a result of research conducted by the inventors of the present invention, it is known that in the process of removing all layers from a used photoreceptor, fine concave-convex surfaces are formed on the surface of the conductive substrate; due to the fine concave-convex surfaces on the surface of the conductive substrate, the granularity of the image is deteriorated (for example, a rough feeling is felt in a halftone image or a gradient image). It is speculated that this is caused by the concave-convex surfaces on the surface of the conductive substrate being reflected on the outer peripheral surface of the photoreceptor, resulting in concave-convex surfaces on the outer peripheral surface of the photoreceptor.

[0075] As a result of further research, the inventors found that the cumulative value S in the power spectrum of the roughness curve of the conductive substrate subjected to fast Fourier transform is an indicator of the surface properties of the conductive substrate that causes the deterioration of the graininess of the image, and clarified that when the cumulative value S is 0.02 or more, the graininess of the image deteriorates. The cumulative value S is preferably 0.10 or less, and the smaller the value, the better.

[0076] In this embodiment, as a method for solving the problem (deterioration of the graininess of the image) caused by the conductive substrate having an integrated value S of 0.02 or more and 0.10 or less, a photoreceptor according to the first embodiment and a photoreceptor according to the second embodiment are provided. In the present invention, when explaining matters common to the first embodiment and the second embodiment, the two methods are collectively referred to as the present embodiment.

[0077] The photoreceptor according to the first embodiment includes a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer. The integrated value S is 0.02 to 0.10, and the thickness of the undercoat layer is 10 μm or more.

[0078] In the first embodiment, the thickness of the undercoat layer is 10 μm or more, so that the surface unevenness of the conductive substrate is difficult to be reflected on the peripheral surface of the photoreceptor, thereby forming an image with excellent granularity. From this viewpoint, the thickness of the undercoat layer is preferably 15 μm or more, more preferably 18 μm or more, and further preferably 20 μm or more.

[0079] From the viewpoint of suppressing residual charge, in the first embodiment, the thickness of the undercoat layer is, for example, preferably 50 μm or less, more preferably 40 μm or less, and further preferably 30 μm or less.

[0080] The thickness of the undercoat layer was the arithmetic average of values ​​measured by an electromagnetic film thickness meter, and the measurement location was four locations at 90° in the circumferential direction at the center in the axial direction of the photoreceptor.

[0081] In the first embodiment, the lower coating layer may or may not contain a filler. In the first embodiment, when the lower coating layer contains a filler, as the filler, for example, preferably inorganic particles, more preferably metal oxide particles, further preferably at least one selected from the group consisting of zinc oxide particles, titanium oxide particles and tin oxide particles. The inorganic particles may be surface treated by a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, etc. An electron accepting compound may be attached to the surface of the inorganic particles. The embodiments of the surface treatment agent and the electron accepting compound are described below.

[0082] The photoreceptor according to the second embodiment includes a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, the integrated value S is 0.02 or more and 0.10 or less, and the undercoat layer contains metal oxide particles.

[0083] In the second embodiment, since the undercoat layer contains metal oxide particles, the surface irregularities of the conductive substrate are less likely to be reflected on the outer peripheral surface of the photoreceptor, thereby forming an image with excellent granularity.

[0084] Examples of the metal oxide particles include zinc oxide particles, titanium oxide particles, tin oxide particles, zirconium oxide particles, etc. The metal oxide particles contained in the undercoat layer may be one type or two or more types.

[0085] From the viewpoint of electrical characteristics of the photoreceptor, the metal oxide particles are preferably at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, and tin oxide particles, and more preferably zinc oxide particles.

[0086] The metal oxide particles may be surface-treated with a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, etc. The surface treatment agent is described below.

[0087] An electron accepting compound may be attached to the surface of the metal oxide particle. The form of the electron accepting compound and the method of attaching the electron accepting compound to the surface of the metal oxide particle will be described later.

[0088] From the viewpoint of suppressing the reflection of the surface unevenness of the conductive substrate on the peripheral surface of the photosensitive body and forming an image with excellent granularity, the average particle size of the metal oxide particles contained in the undercoat layer is, for example, preferably greater than 5 nm and less than 100 nm, more preferably greater than 10 nm and less than 80 nm, and further preferably greater than 20 nm and less than 50 nm.

[0089] The average particle size of the metal oxide particles is determined by the following measuring method.

[0090] The metal oxide particles are removed from the undercoat layer. The method of removing the metal oxide particles from the undercoat layer includes, for example, immersing the undercoat layer peeled off from the photoreceptor in an organic solvent that dissolves the binder resin, dissolving the binder resin with the organic solvent and removing the metal oxide particles; heating the undercoat layer peeled off from the photoreceptor to about 800° C. to make the binder resin disappear, and removing the metal oxide particles; etc.

[0091] The metal oxide particles were observed with a scanning electron microscope, and the equivalent circle diameters of 100 randomly selected primary particles were determined. The arithmetic mean of the equivalent circle diameters was defined as the average particle diameter.

[0092] From the viewpoint of suppressing the reflection of the surface irregularities of the conductive substrate on the peripheral surface of the photosensitive body and forming an image with excellent granularity, the mass proportion of the metal oxide particles in the undercoat layer is, for example, preferably greater than 60 mass % and less than 95 mass %, more preferably greater than 70 mass % and less than 95 mass %, and further preferably greater than 80 mass % and less than 90 mass %.

[0093] From the viewpoint of better image granularity, in the second embodiment, the thickness of the undercoat layer is, for example, preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm or more, further preferably 18 μm or more, further preferably 20 μm or more.

[0094] From the viewpoint of suppressing residual charge, in the second embodiment, the thickness of the undercoat layer is, for example, preferably 50 μm or less, more preferably 40 μm or less, and further preferably 30 μm or less.

[0095] Hereinafter, each layer of the photoreceptor will be described in detail.

[0096] [Conductive substrate]

[0097] As the conductive substrate, for example, metal plates, metal rollers, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.) can be cited. In addition, as the conductive substrate, for example, conductive compounds (such as conductive polymers, indium oxide, etc.); paper coated, vapor-deposited, or laminated with metals (such as aluminum, palladium, gold, etc.) or alloys; resin films; belts, etc. Here, "conductive" means that the volume resistivity is less than 1×10 13 Ω·cm.

[0098] One embodiment of the conductive substrate is a conductive substrate that is regenerated by removing all layers on the conductive substrate from a used photoreceptor. An example of a method for removing all or each layer on the conductive substrate is a water jet method (details will be described later).

[0099] The used photoreceptor has a conductive substrate for manufacturing the photoreceptor, and the conductive substrate may be any known conductive substrate, such as a conductive substrate subjected to wet grinding, centerless grinding, anodizing treatment, acid treatment, boehmite treatment, etc.

[0100] [Undercoat]

[0101] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0102] Examples of inorganic particles include powder resistance (volume resistivity) of 1×10 2 Ω·cm or more and 1×10 11 Inorganic particles with a particle size of less than Ω·cm.

[0103] Among them, as the inorganic particles having the above resistance value, for example, metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles are preferred, and zinc oxide particles are particularly preferred.

[0104] The specific surface area of ​​the inorganic particles based on the BET method is preferably 10 m 2 / g or above.

[0105] The volume average particle diameter of the inorganic particles is, for example, preferably 50 nm or more and 2000 nm or less (for example, preferably 60 nm or more and 1000 nm or less).

[0106] When the undercoat layer contains inorganic particles, the content of the inorganic particles is, for example, preferably 60 mass % to 95 mass % relative to the total amount of the undercoat layer, more preferably 70 mass % to 95 mass % and further preferably 80 mass % to 90 mass %

[0107] The inorganic particles may be subjected to surface treatment. Two or more inorganic particles having different surface treatments or particles having different particle sizes may be used in combination.

[0108] Examples of the surface treatment agent include silane coupling agents, titanate coupling agents, aluminum coupling agents, surfactants, etc. In particular, for example, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

[0109] Examples of the silane coupling agent having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0110] Silane coupling agents can be mixed and used in two or more ways. For example, silane coupling agents with amino groups can be used in combination with other silane coupling agents. As other silane coupling agents, for example, vinyl trimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyl trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, vinyl triacetoxysilane, 3-mercaptopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, N-2- (aminoethyl) -3-aminopropyl trimethoxysilane, N-2- (aminoethyl) -3-aminopropyl methyl dimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyl triethoxysilane, 3-chloropropyl trimethoxysilane, etc. can be cited, but it is not limited thereto.

[0111] The surface treatment method using the surface treatment agent may be any method as long as it is a known method, and may be either a dry method or a wet method.

[0112] The treatment amount of the surface treatment agent is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0113] Here, from the viewpoint of improving the long-term stability of electrical characteristics and carrier blocking properties, the undercoat layer preferably contains an electron accepting compound (acceptor compound) together with inorganic particles, for example.

[0114] As electron accepting compounds, for example, there can be mentioned quinone compounds such as chloranil and tetrabromobenzoquinone; tetracyanobenzoquinone dimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; diphenoquinone compounds such as 3,3',5,5'-tetra-tert-butyldiphenoquinone; benzophenone compounds; and other electron transporting substances.

[0115] In particular, the electron accepting compound is preferably a compound having an anthraquinone structure. The compound having an anthraquinone structure is preferably a hydroxyanthraquinone compound, an aminoanthraquinone compound, an aminohydroxyanthraquinone compound, and more specifically, anthraquinone, alizarin, quinizarin, anthraquinone, purpurin, and the like.

[0116] The electron accepting compound may be contained in the undercoat layer in a dispersed state together with the inorganic particles, or may be contained in the undercoat layer in a state of being attached to the surfaces of the inorganic particles.

[0117] Examples of a method for attaching the electron accepting compound to the surface of the inorganic particles include a dry method and a wet method.

[0118] The dry method is, for example, a method in which an electron accepting compound or an electron accepting compound dissolved in an organic solvent is directly added dropwise while stirring the inorganic particles by a mixer with a large shear force, and the electron accepting compound is sprayed together with dry air or nitrogen to attach the electron accepting compound to the surface of the inorganic particles. When the electron accepting compound is added dropwise or sprayed, for example, it can be done at a temperature below the boiling point of the solvent. After the electron accepting compound is added dropwise or sprayed, sintering can also be performed at a condition of 100°C or above. There is no particular limitation on the sintering temperature and time as long as the electrophotographic properties can be obtained.

[0119] The wet method is, for example, a method in which inorganic particles are dispersed in a solvent by stirring, ultrasonic waves, a sand mill, a grinder, a ball mill, etc., and after adding an electron accepting compound and stirring or dispersing, the solvent is removed to attach the electron accepting compound to the surface of the inorganic particles. The solvent removal method is, for example, to remove the solvent by filtering or distilling. After removing the solvent, sintering can also be performed at a condition of 100°C or above. Sintering is not particularly limited as long as the temperature and time are such that electronic photographic properties can be obtained. In the wet method, the water contained in the inorganic particles can be removed before adding the electron accepting compound. As examples thereof, a method of removing the water while stirring and heating in a solvent and a method of removing the water by azeotropy with the solvent can be cited.

[0120] The electron accepting compound may be attached before or after the inorganic particles are surface treated with a surface treatment agent, or the electron accepting compound may be attached and the surface treated with a surface treatment agent may be simultaneously performed.

[0121] The content of the electron accepting compound may be, for example, 0.01 mass % to 20 mass % inclusive, and preferably 0.01 mass % to 10 mass % inclusive, based on the inorganic particles.

[0122] Examples of the binder resin used in the lower coating layer include acetal resins (e.g., polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenolic resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, epoxy resins and other well-known polymer compounds; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; silane coupling agents and other well-known materials.

[0123] Examples of the binder resin used in the undercoat layer include a charge transporting resin having a charge transporting group, and a conductive resin (for example, polyaniline).

[0124] Among them, the binding resin used in the lower coating layer is preferably a resin that is insoluble in the coating solvent in the upper layer, and is particularly preferably a resin obtained by reacting at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenolic resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, epoxy resin, polyamide resin, polyester resin, polyether resin, methacrylic resin, acrylic resin, polyvinyl alcohol resin and polyvinyl acetal resin with a curing agent.

[0125] When two or more of these binder resins are used in combination, the mixing ratio is set as necessary.

[0126] In order to improve electrical characteristics, improve environmental stability, and improve image quality, various additives may be included in the undercoat layer.

[0127] As additives, there can be mentioned known materials such as polycyclic condensation type, azo type and other electron transporting pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, silane coupling agents, etc. As mentioned above, silane coupling agents are used for surface treatment of inorganic particles, but can also be added to the undercoat layer as an additive.

[0128] Examples of the silane coupling agent as an additive include vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0129] Examples of the zirconium chelate compound include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, zirconium acetylacetonate butoxide, zirconium ethyl acetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium methacrylate butoxide, zirconium stearate butoxide, and zirconium isostearate butoxide.

[0130] Examples of the titanium chelate compound include tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, titanium polyacetylacetonate, titanium octanediol, ammonium lactate titanium, titanium lactate, ethyl lactate titanium, triethanolamine titanium, and polyhydroxystearate titanium.

[0131] Examples of the aluminum chelate compound include aluminum isopropoxide, monobutoxyaluminum diisopropoxide, aluminum butoxide, diethyl acetoacetate aluminum diisopropoxide, and tris(ethyl acetoacetate)aluminum.

[0132] These additives may be used alone or in the form of a mixture or polycondensate of a plurality of compounds.

[0133] The undercoat layer may have a Vickers hardness of 35 or more, for example.

[0134] In order to suppress interference moire images, the surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to, for example, 1 / (4n) (n is the refractive index of the upper layer) to 1 / 2 of the wavelength λ of the exposure laser used.

[0135] In order to adjust the surface roughness, resin particles or the like may be added to the undercoat layer. Examples of the resin particles include silicone resin particles and cross-linked polymethacrylate methyl resin particles. In addition, in order to adjust the surface roughness, the surface of the undercoat layer may be ground. Examples of the grinding method include polishing, sandblasting, wet grinding, grinding, and the like.

[0136] The formation of the undercoat layer is not particularly limited and can be performed by a known formation method. For example, the undercoat layer can be formed by forming a coating film of an undercoat layer-forming coating liquid in which the above-mentioned components are added to a solvent, drying the coating film, and heating as necessary.

[0137] Examples of the solvent used for preparing the coating solution for forming an undercoat layer include known organic solvents such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketone alcohol solvents, ether solvents, and ester solvents.

[0138] Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, and toluene.

[0139] Examples of a method for dispersing the inorganic particles when preparing the coating liquid for forming an undercoat layer include known methods such as a roll mill, a ball mill, a vibration ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0140] Examples of a method for applying the coating liquid for forming an undercoat layer onto the conductive substrate include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0141] In the first embodiment and the second embodiment, the thickness of the undercoat layer is preferably, for example, in the above-described range.

[0142] [Middle layer]

[0143] The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include acetal resins (e.g., polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, melamine resins and other polymer compounds.

[0144] The intermediate layer may be a layer containing an organic metal compound. Examples of the organic metal compound used in the intermediate layer include organic metal compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon.

[0145] The compounds used in the intermediate layer may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0146] Among them, the intermediate layer is preferably a layer containing an organic metal compound containing zirconium atoms or silicon atoms, for example.

[0147] The formation of the intermediate layer is not particularly limited and can be performed by a known formation method. For example, the intermediate layer can be formed by forming a coating film of an intermediate layer-forming coating liquid in which the above-mentioned components are added to a solvent, drying the coating film, and heating as necessary.

[0148] As a coating method for forming the intermediate layer, a common method such as a dip coating method, a push coating method, a wire bar coating method, a spray coating method, a blade coating method, an air knife coating method, a curtain coating method, etc. can be used.

[0149] The thickness of the intermediate layer is preferably set within a range of, for example, 0.1 μm or more and 3 μm or less. The intermediate layer can be used as an undercoat layer.

[0150] [Charge Generation Layer]

[0151] The charge generating layer is, for example, a layer containing a charge generating material and a binder resin. Furthermore, the charge generating layer may be a vapor-deposited layer of the charge generating material. The vapor-deposited layer of the charge generating material is suitable for the case where an incoherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array is used.

[0152] Examples of the charge generating material include azo pigments such as disazo and trisazo; condensed ring aromatic pigments such as dibromoanthraquinone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0153] Among them, in order to cope with laser exposure in the near-infrared region, metal phthalocyanine pigments or metal-free phthalocyanine pigments are preferably used as charge generating materials, and more specifically, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and oxytitanium phthalocyanine are more preferred.

[0154] On the other hand, in order to cope with laser exposure in the near-ultraviolet region, preferred charge generating materials include condensed ring aromatic pigments such as dibromoanthraquinone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and disazo pigments.

[0155] The above-mentioned charge generating material can be used even when an incoherent light source such as an LED or an organic EL array having a central wavelength of light emitted in the range of 450 nm to 780 nm is used.

[0156] In contrast, when n-type semiconductors such as condensed aromatic pigments, perylene pigments, and azo pigments are used as charge generating materials, dark current is less likely to be generated, and image defects called black spots can be suppressed even in thin films. The n-type is determined by the polarity of the photocurrent flowing using the commonly used time-of-flight method, and semiconductors that are more likely to flow with electrons as carriers than holes are defined as n-type.

[0157] The binder resin used in the charge generating layer can be selected from a wide range of insulating resins, and can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinyl anthracene, polyvinyl pyrene, and polysilane.

[0158] Examples of the binder resin include polyvinyl butyral resin, polyarylate resin (condensation products of bisphenols and aromatic dicarboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinyl pyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinyl pyrrolidone resin, etc. Here, "insulation" means that the volume resistivity is 10 13 These binder resins may be used alone or in combination of two or more.

[0159] The mixing ratio of the charge generating material to the binder resin is preferably in the range of 10:1 to 1:10, for example, in terms of mass ratio.

[0160] Other known additives may be contained in the charge generating layer.

[0161] The formation of the charge generating layer is not particularly limited, and a known formation method can be used, but for example, a coating film of a charge generating layer forming coating liquid in which the above-mentioned components are added to a solvent is formed, the coating film is dried, and heating is performed as needed. The charge generating layer can be formed by vapor deposition of the charge generating material. The formation of the charge generating layer by vapor deposition is particularly suitable for the case where a condensed ring aromatic pigment or a perylene pigment is used as the charge generating material.

[0162] Examples of the solvent used for preparing the charge generating layer-forming coating solution include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, toluene, etc. These solvents may be used alone or in combination of two or more.

[0163] As a method for dispersing particles (e.g., charge generating materials) in a coating liquid for forming a charge generating layer, for example, a medium disperser such as a ball mill, a vibrating ball mill, a grinder, a sand mill, a horizontal sand mill, or a stirrer, an ultrasonic disperser, a roller mill, a high-pressure homogenizer, or a medium-free disperser can be used. As a high-pressure homogenizer, for example, a collision method in which the dispersion is subjected to liquid-liquid collision or liquid-wall collision under high pressure to disperse it, a penetration method in which a fine flow path is penetrated under high pressure to disperse it, etc. can be cited. When dispersing, the average particle size of the charge generating material in the coating liquid for forming the charge generating layer is set to 0.5 μm or less, for example, preferably to 0.3 μm or less, and more preferably to 0.15 μm or less.

[0164] Examples of a method for applying the charge generating layer forming coating liquid onto the undercoat layer (or the intermediate layer) include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0165] The thickness of the charge generating layer is preferably set within the range of, for example, 0.1 μm to 5.0 μm, and more preferably within the range of 0.2 μm to 2.0 μm.

[0166] [Charge transport layer]

[0167] The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may be a layer containing a polymer charge transport material.

[0168] As charge transport materials, there can be cited quinone compounds such as p-benzoquinone, chloranil, tetrabromobenzoquinone, anthraquinone, etc.; tetracyanoterephthalene compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; anthrone compounds; benzophenone compounds; cyanoethylene compounds; vinyl compounds and other electron transport compounds. As charge transport materials, there can also be cited triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted vinyl compounds, stilbene compounds, anthracene compounds, hydrazone compounds and other hole transport compounds. These charge transport materials can be used alone or in combination of two or more, but are not limited thereto.

[0169] From the viewpoint of charge mobility, the charge transport material is preferably, for example, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2).

[0170] [Chemical formula 1]

[0171]

[0172] In the structural formula (a-1), Ar T1 ,ArT2 and Ar T3 Each independently represents a substituted or unsubstituted aryl group, -C6H4-C(R T4 )=C(R T5 )(R T6 ) or -C6H4-CH=CH-CH=C(R T7 )(R T8 ). T4 , R T5 , R T6 , R T7 and R T8 Each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

[0173] Examples of substituents of the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. In addition, examples of substituents of the above groups include substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms.

[0174] [Chemical formula 2]

[0175]

[0176] In the structural formula (a-2), R T91 and R T92 R each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. T101 , R T102 , R T111 and R T112 each independently represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted by an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ) or -CH=CH-CH=C(R T15 )(R T16 ), R T12 , R T13 , R T14 , R T15 and R T16 Each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, ​​Tn1, and Tn2 each independently represent an integer of 0 or more and 2 or less.

[0177] Examples of substituents of the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. In addition, examples of substituents of the above groups include substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms.

[0178] From the viewpoint of charge mobility, among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), for example, those having "-C6H4-CH=CH-CH=C(R T7 )(R T8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 )" benzidine derivatives.

[0179] As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinyl carbazole and polysilane can be cited. In particular, polyester-based polymer charge transport materials are particularly preferred. The polymer charge transport material can be used alone or in combination with a binder resin.

[0180] The binder resin used in the charge transport layer can be polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinyl carbazole, polysilane, etc. Among them, as a binder resin, for example, preferably polycarbonate resin or polyarylate resin. These binder resins are used alone or in combination of two or more.

[0181] The mixing ratio of the charge transport material to the binder resin is preferably, for example, 10:1 to 1:5 in terms of mass ratio.

[0182] Other known additives may be contained in the charge transport layer.

[0183] The charge transport layer can be formed by any known method without particular limitation, and can be formed by, for example, forming a coating film of a charge transport layer-forming coating liquid in which the above components are added to a solvent, drying the coating film, and heating as necessary.

[0184] As the solvent for preparing the coating solution for forming the charge transport layer, there can be mentioned aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, and dichloroethane; cyclic or linear ethers such as tetrahydrofuran and diethyl ether, and other common organic solvents. These solvents can be used alone or in combination of two or more.

[0185] Examples of a coating method for coating the charge transport layer-forming coating liquid on the charge generating layer include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0186] The thickness of the charge transport layer is preferably set within a range of, for example, 5 μm to 50 μm, and more preferably within a range of 10 μm to 30 μm.

[0187] [Protective layer]

[0188] The protective layer is provided on the photosensitive layer as required. The protective layer is provided, for example, to prevent chemical changes in the photosensitive layer during charging or to further improve the mechanical strength of the photosensitive layer.

[0189] Therefore, for example, a layer composed of a cured film (crosslinked film) is preferably used as the protective layer. Examples of these layers include the layers shown in the following 1) or 2).

[0190] 1) A layer consisting of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton in the same molecule (i.e., a layer containing a polymer or a crosslinked body of the reactive group-containing charge transport material)

[0191] 2) A layer composed of a cured film of a composition comprising a non-reactive charge transport material and a non-charge transport material having a reactive group but not having a charge transport skeleton (i.e., a layer comprising a non-reactive charge transport material and a polymer or a crosslinked body of the non-charge transport material having a reactive group)

[0192] Examples of the reactive group of the charge transport material containing a reactive group include a chain polymerizable group, an epoxy group, -OH, -OR [wherein R represents an alkyl group], -NH2, -SH, -COOH, -SiR Q1 3-Qn (OR Q2 ) Qn [Among them, R Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group, R Q2 represents a hydrogen atom, an alkyl group, a trialkylsilyl group, Qn represents an integer of 1 to 3] and the like.

[0193] As a chain polymerizable group, there is no particular limitation as long as it is a functional group capable of free radical polymerization, and for example, it is a functional group having a group containing at least a carbon double bond. Specifically, there can be mentioned a group containing at least one selected from vinyl, vinyl ether, vinyl sulfide, styryl (vinyl phenyl), acryloyl, methacryloyl and their derivatives. Among them, due to its excellent reactivity, as a chain polymerizable group, for example, it is preferably a group containing at least one selected from vinyl, styryl (vinyl phenyl), acryloyl, methacryloyl and their derivatives.

[0194] The charge transport skeleton of the charge transport material containing a reactive group is not particularly limited as long as it is a known structure in an electrophotographic photoreceptor, and examples thereof include skeletons derived from nitrogen-containing hole transport compounds such as triarylamine compounds, benzidine compounds, and hydrazone compounds, and structures conjugated with nitrogen atoms. Among them, for example, a triarylamine skeleton is preferred.

[0195] The reactive group-containing charge transport material, the non-reactive charge transport material, and the reactive group-containing non-charge transport material having these reactive groups and charge transport skeletons may be selected from known materials.

[0196] Other known additives may be contained in the protective layer.

[0197] The protective layer can be formed by any known method without particular limitation, and can be formed by, for example, forming a coating film of a protective layer-forming coating liquid in which the above components are added to a solvent, drying the coating film, and performing a curing treatment such as heating as necessary.

[0198] Examples of the solvent used to prepare the protective layer-forming coating solution include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; cellosolve solvents such as ethylene glycol monomethyl ether; alcohol solvents such as isopropyl alcohol and butanol, etc. These solvents may be used alone or in combination of two or more.

[0199] The protective layer-forming coating liquid may be a solvent-free coating liquid.

[0200] Examples of a method for applying the protective layer-forming coating liquid onto a photosensitive layer (eg, charge transport layer) include common methods such as dip coating, push coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating.

[0201] The film thickness of the protective layer is preferably set within the range of, for example, 1 μm to 20 μm, and more preferably within the range of 2 μm to 10 μm.

[0202] [Single-layer photosensitive layer]

[0203] The single-layer photosensitive layer (charge generation / charge transport layer) is, for example, a layer containing a charge generation material, a charge transport material, and, if necessary, a binder resin and other known additives. These materials are the same as those described for the charge generation layer and the charge transport layer.

[0204] In the monolayer photosensitive layer, the content of the charge generating material relative to the total solid content is, for example, 0.1 mass % or more and 10 mass % or less, preferably 0.8 mass % or more and 5 mass % or less. In the monolayer photosensitive layer, the content of the charge transporting material relative to the total solid content is, for example, 5 mass % or more and 50 mass % or less.

[0205] The method for forming the single-layer photosensitive layer is the same as the method for forming the charge generating layer or the charge transporting layer.

[0206] The thickness of the single-layer photosensitive layer may be, for example, 5 μm or more and 50 μm or less, and preferably 10 μm or more and 40 μm or less.

[0207] <Method for producing electrophotographic photoreceptor>

[0208] An example of a method for manufacturing a photoreceptor according to the present embodiment includes the following steps:

[0209] Regenerating the conductive substrate by removing all layers on the conductive substrate from the used photoreceptor (conductive substrate regeneration step);

[0210] forming an undercoat layer on the regenerated conductive substrate (undercoat layer forming step); and

[0211] A photosensitive layer is formed on the undercoat layer (photosensitive layer forming step).

[0212] The method for manufacturing a photoreceptor according to the present embodiment may further include a step of forming a protective layer on the photosensitive layer (protective layer forming step).

[0213] An example of the method for producing a photoreceptor according to the present embodiment uses a regenerated conductive substrate, and the conductive substrate having a cumulative value S of 0.02 or more and 0.10 or less.

[0214] [Conductive substrate regeneration process]

[0215] The regeneration step of the conductive substrate may remove all layers on the conductive substrate at once or may remove each layer in sequence.

[0216] The method for removing all or each layer on the conductive substrate is not limited, but a water jet method is preferably used to remove all or each layer by causing high-speed water to collide with the photoreceptor. Water jetting reduces the risk of chemical modification or contamination of the surface of the conductive substrate.

[0217] The surface of the conductive substrate regenerated by peeling off all or each layer on the conductive substrate by water jetting may have fine irregularities. The integrated value S of an example of an embodiment of the conductive substrate regenerated by water jetting is 0.02 or more and 0.10 or less.

[0218] The water pressure, water volume and water temperature of the water spray are not limited and can be set according to the material of the conductive substrate, the composition and thickness of each layer to be stripped, and the time and power required for stripping. The water pressure, water volume and water temperature of the water spray are set to a water pressure, water volume and water temperature at which the cumulative value S of the regenerated conductive substrate becomes less than 0.10.

[0219] The water used for the spraying may be water to which a surfactant has been added.

[0220] Water jetting may be combined with other stripping means. For example, after the used photoreceptor is immersed in a solvent or after the used photoreceptor is heated, all or each softened layer may be stripped by water jetting. In addition, for example, after a part of the layer is removed by air jetting, water jetting may be performed as a final process.

[0221] The material of the regenerated conductive substrate is, for example, metals such as aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.; alloys such as stainless steel; conductive polymers, conductive compounds such as indium oxide; paper or resin sheets coated, vapor deposited or laminated with metal or alloy; etc. "Conductive" means that the volume resistivity is less than 1×10 13 Ω·cm.

[0222] The regenerated conductive substrate may be in the form of a roll, a belt, a drum, a sheet, a plate, or the like.

[0223] The regenerated conductive substrate may be subjected to an acid treatment or a boehmite treatment to form a coating.

[0224] [Undercoat layer forming step]

[0225] The formation of the undercoat layer includes, for example, a step of preparing a coating liquid for forming the undercoat layer, a step of applying the coating liquid for forming the undercoat layer on the conductive substrate to form a coating film, a step of drying the coating film, and a step of heating the coating film as needed. The implementation of each step is as described for the undercoat layer.

[0226] When the photoreceptor according to the first embodiment is manufactured, an undercoat layer having a thickness of 10 μm or more is formed in the undercoat layer forming step. The range of the undercoat layer thickness is the same as described in the first embodiment.

[0227] When manufacturing the photoreceptor according to the second embodiment, an undercoat layer containing metal oxide particles is formed in an undercoat layer forming step. The embodiment of the metal oxide particles is as described in the second embodiment.

[0228] The photosensitive layer forming step is implemented as described with respect to the charge generating layer, the charge transporting layer, and the single-layer photosensitive layer.

[0229] The embodiment of the protective layer forming step is as described in relation to the protective layer.

[0230] <Image forming apparatus, process cartridge>

[0231] The image forming apparatus according to the present embodiment includes an electrophotographic photoreceptor, a charging device for charging the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image, and a transfer device for transferring the toner image to the surface of a recording medium. As the electrophotographic photoreceptor, the electrophotographic photoreceptor according to the present embodiment is applicable.

[0232] The image forming device involved in this embodiment is applicable to the following well-known image forming devices: a device equipped with a fixing device for fixing the toner image transferred to the surface of a recording medium; a device using a direct transfer method for directly transferring the toner image formed on the surface of an electrophotographic photosensitive body to the recording medium; a device using an intermediate transfer method for transferring the toner image formed on the surface of an electrophotographic photosensitive body once to the surface of an intermediate transfer body, and for a second time transferring the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium; a device equipped with a cleaning device for cleaning the surface of the electrophotographic photosensitive body after transferring the toner image but before charging; a device equipped with a static elimination device for removing static electricity by irradiating the surface of the electrophotographic photosensitive body with static elimination light after transferring the toner image and before charging; and a device equipped with an electrophotographic photosensitive body heating component for increasing the temperature of the electrophotographic photosensitive body and lowering the relative temperature, etc.

[0233] In the case of an intermediate transfer type device, the transfer device, for example, is applicable to the following structure, which has an intermediate transfer body that transfers the toner image on the surface, a primary transfer device that transfers the toner image formed on the surface of the electronic photographic photosensitive body to the surface of the intermediate transfer body for the first time, and a secondary transfer device that transfers the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium for the second time.

[0234] The image forming apparatus according to the present embodiment may be any of a dry developing system image forming apparatus and a wet developing system (development system using a liquid developer) image forming apparatus.

[0235] In the image forming apparatus according to the present embodiment, for example, the portion having the electrophotographic photoreceptor may be a cartridge structure (processing cartridge) that is detachable from the image forming apparatus. As the processing cartridge, for example, a processing cartridge having the electrophotographic photoreceptor according to the present embodiment is preferably used. In the processing cartridge, in addition to the electrophotographic photoreceptor, for example, at least one selected from the group consisting of a charging device, an electrostatic latent image forming device, a developing device, and a transfer device may be provided.

[0236] An example of the image forming apparatus according to the present embodiment is shown below, but the present invention is not limited thereto. The main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0237] Figure 3 It is a schematic configuration diagram showing an example of the image forming apparatus according to the present embodiment.

[0238] like Figure 3 As shown, the image forming apparatus 100 according to the present embodiment includes a process box 300 having an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is arranged at a position capable of exposing the electrophotographic photoreceptor 7 from the opening of the process box 300, and the transfer device 40 is arranged at a position opposed to the electrophotographic photoreceptor 7 with the intermediate transfer body 50 interposed therebetween, and the intermediate transfer body 50 is arranged so that a part thereof contacts the electrophotographic photoreceptor 7. Although not shown in the figure, a secondary transfer device is further provided for transferring the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown in the figure) correspond to an example of a transfer device.

[0239] Figure 3 The process box 300 in the embodiment integrally supports the electrophotographic photoreceptor 7, the charging device 8 (an example of a charging device), the developing device 11 (an example of a developing device), and the cleaning device 13 (an example of a cleaning device) in a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is configured to contact the surface of the electrophotographic photoreceptor 7. The cleaning member may be a conductive or insulating fibrous member instead of the cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

[0240] exist Figure 3 In the example shown, as the image forming apparatus, a fibrous member 132 (roller-shaped) for supplying lubricant 14 to the surface of electrophotographic photoreceptor 7 and a fibrous member 133 (flat brush-shaped) for assisting cleaning are provided, but these may be arranged as necessary.

[0241] Hereinafter, each structure of the image forming apparatus according to the present embodiment will be described.

[0242] -Electrified Devices-

[0243] As the charging device 8, for example, a contact type charging device such as a charging roller, a charging brush, a charging film, a charging rubber blade, a charging hose, etc. using conductive or semi-conductive charging can be used. In addition, a non-contact type roller charging device, a scorotron charging device or a corotron charging device using corona discharge, etc., which are known per se, can also be used.

[0244] -Exposure device-

[0245] As the exposure device 9, for example, there can be cited an optical system device that exposes semiconductor laser, LED light, liquid crystal shutter light, etc. on the surface of the electrophotographic photoreceptor 7 to a prescribed pattern. The wavelength of the light source is set within the spectral sensitivity region of the electrophotographic photoreceptor. As the wavelength of the semiconductor laser, near-infrared light with an oscillation wavelength near 780nm is the mainstream. However, it is not limited to this wavelength. As an oscillation wavelength laser or a blue laser in the 600nm band, a laser with an oscillation wavelength in the range of more than 400nm and less than 450nm can also be used. In addition, a surface-emitting laser light source of the type that can output multiple beams in order to form a color image is also effective.

[0246] -Developing device-

[0247] As the developing device 11, for example, a general developing device that develops by contact or non-contact with a developer can be cited. As the developing device 11, there is no particular limitation as long as it has the above-mentioned function, and it can be selected according to the purpose. For example, a known developer having a function of attaching a single-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, a roller, etc. can be cited. Among them, for example, a developer using a developing roller that holds the developer on the surface is preferred.

[0248] The developer used in the developing device 11 may be a single-component developer containing only a toner, or a two-component developer containing a toner and a carrier. Furthermore, the developer may be magnetic or non-magnetic. These developers are suitable for known developers.

[0249] -Cleaning device-

[0250] The cleaning device 13 may be a cleaning blade type device including a cleaning blade 131. In addition to the cleaning blade type, a brush cleaning method or a simultaneous development cleaning method may be used.

[0251] -Transfer device-

[0252] Examples of the transfer device 40 include a contact transfer charger using a belt, a roller, a film, a rubber blade, etc.; a corotron transfer charger using corona discharge; a corotron transfer charger, etc., which are known per se.

[0253] -Intermediate transfer body-

[0254] As the intermediate transfer body 50, a belt-shaped transfer body (intermediate transfer belt) made of polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. imparted with semiconductivity can be used. In addition, as a form of the intermediate transfer body, a roller-shaped transfer body can be used.

[0255] Figure 4 It is a schematic configuration diagram showing another example of the image forming apparatus according to the present embodiment.

[0256] Figure 4 The image forming apparatus 120 shown is a multi-color image forming apparatus of a tandem type equipped with four process cartridges 300. In the image forming apparatus 120, four process cartridges 300 are arranged on the intermediate transfer body 50, respectively, and a single electrophotographic photoreceptor is used for each color. The image forming apparatus 120 has the same structure as the image forming apparatus 100 except for the tandem type.

[0257] Example

[0258] Hereinafter, embodiments of the present invention will be described in detail based on examples, but embodiments of the present invention are not limited to these examples.

[0259] In the following description, "parts" and "%" are based on mass unless otherwise specified.

[0260] In the following description, unless otherwise specified, synthesis, production, treatment, measurement, etc. were performed at room temperature (25° C.±3° C.).

[0261] <Regeneration of conductive substrate>

[0262] A used photoreceptor is prepared. The photoreceptor includes an aluminum cylindrical tube for manufacturing the photoreceptor. The integrated value S of the new aluminum cylindrical tube for manufacturing the photoreceptor is less than 0.02.

[0263] The conductive substrate was regenerated by removing all layers from the used photoreceptor by spraying water. By changing the water pressure of the sprayed water, conductive substrates (1) to (3) with different cumulative values ​​S were obtained. The cumulative values ​​S of each of the conductive substrates (1) to (3) are shown in Table 1.

[0264] The conductive substrates (1) to (3) are aluminum cylindrical tubes with an outer diameter of 30 mm, a length of 250 mm, and a wall thickness of 1 mm.

[0265] <<First Embodiment>>

[0266] <Example 1>

[0267] [Formation of undercoat layer]

[0268] 20 parts of blocked isocyanate (trade name: SUMIDUR BL3175, manufactured by Sumitomo Bayer Urethane Co., Ltd., solid content 75%) and 7.5 parts of butyral resin (polyvinyl butyral, S-LEC BL-1, manufactured by SEKISUI CHEMICAL CO., LTD.) were dissolved in 150 parts of methyl ethyl ketone. 34 parts of a mixture of a violet ketone compound (1-1) and a violet ketone compound (2-1) (mass ratio 50:50) were mixed in the solution, and dispersed for 10 hours using a sand mill using glass beads with a diameter of 1 mm to obtain a dispersion. 0.005 parts of bismuth carboxylate (K-KAT XK-640, manufactured by KING INDUSTRY) were added to the dispersion to obtain a coating solution for forming an undercoat layer. The coating solution was dip-coated on the outer peripheral surface of the conductive substrate (1), and dried and cured at 160°C for 60 minutes to form an undercoat layer. The thickness of the undercoat layer is as shown in Table 1.

[0269] [Chemical formula 3]

[0270]

[0271] [Formation of Charge Generation Layer]

[0272] A mixture consisting of 15 parts of hydroxygallium phthalocyanine (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in the X-ray diffraction spectrum using CuKα characteristic X-rays) as a charge generating material, 10 parts of a vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, manufactured by Nippon Unicar Company Limited) as a binder resin, and 200 parts of n-butyl acetate was dispersed using glass beads having a diameter of 1 mm and a sand mill for 4 hours. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion, and the mixture was stirred to obtain a coating solution for forming a charge generating layer. The coating solution was dip-coated on the undercoat layer and dried at room temperature to form a charge generating layer having a layer thickness of 0.25 μm.

[0273] [Formation of Charge Transport Layer]

[0274] In a mixed solvent of 270 parts of tetrahydrofuran and 30 parts of toluene, 60 parts of polycarbonate resin (1) (viscosity average molecular weight 40000, the values ​​in the following structural formula are molar ratios) and 40 parts of CTM-1, a charge transport material, were dissolved to obtain a coating liquid for forming a charge transport layer. The coating liquid was dip-coated on the charge generating layer, and the coating film was dried at a temperature of 150° C. for 30 minutes to form a charge transport layer with a layer thickness of 20 μm.

[0275] [Chemical formula 4]

[0276]

[0277] In the formula, 75 and 25 represent molar ratios (mol %).

[0278] <Examples 2 to 9>

[0279] Except having changed the kind of the conductive substrate and the thickness of the undercoat layer into the specifications described in Table 1, it carried out similarly to Example 1, and each photoreceptor was produced.

[0280] <Comparative Examples 1 to 3>

[0281] Except having changed the kind of the conductive substrate and the thickness of the undercoat layer into the specifications described in Table 1, it carried out similarly to Example 1, and each photoreceptor was produced.

[0282] <<Second Embodiment>>

[0283] <Example 10>

[0284] A photoreceptor was prepared in the same manner as in Example 1 except that the formation of the undercoat layer was changed as follows.

[0285] [Formation of undercoat layer]

[0286] 100 parts of zinc oxide (average particle size 70 nm, manufactured by TAYCA CORPORATION) and 500 parts of toluene were stirred and mixed, and 1.3 parts of a silane coupling agent (trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) were added and stirred for 2 hours. Then, the toluene was distilled under reduced pressure and sintered at 120° C. for 3 hours to obtain zinc oxide surface-treated with a silane coupling agent.

[0287] 110 parts of surface-treated zinc oxide and 500 parts of tetrahydrofuran were mixed and stirred, and a solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added, followed by stirring at 50° C. for 5 hours. Then, the solid content was filtered out by vacuum filtration and dried at 60° C. to obtain zinc oxide with alizarin.

[0288] 60 parts of zinc oxide imparting alizarin, 13.5 parts of a curing agent (blocked isocyanate, trade name: SUMIDURBL3175, manufactured by Sumitomo Bayer Urethane Co., Ltd., solid content 25% by mass) and 10 parts of a butyral resin (trade name: S-LEC BM-1, manufactured by SEKISUI CHEMICAL CO., LTD.) were mixed and dissolved in 100 parts of a solution of 68 parts of methyl ethyl ketone and 5 parts of methyl ethyl ketone, and dispersed in a sand mill for 2 hours using glass beads with a diameter of 1 mm to obtain a dispersion. 0.005 parts of dioctyltin dilaurate as a catalyst was added to the dispersion to obtain a coating liquid for forming an undercoat layer. The coating liquid was dip-coated on the outer peripheral surface of the conductive substrate (1), and dried and cured at 170°C for 40 minutes to form an undercoat layer. The thickness of the undercoat layer is as shown in Table 1.

[0289] <Examples 11 to 17>

[0290] Each photoreceptor was prepared in the same manner as in Example 10 except that the type of the conductive substrate, the thickness of the undercoat layer, and the type of the metal oxide particles were changed to the specifications described in Table 1.

[0291] <Photoreceptor performance evaluation>

[0292] [Graininess of the image]

[0293] Under an environment of temperature 23° C. and relative humidity 55%, half-tone images with image densities ranging from 5% to 100% in 5% increments were formed on A3-size plain paper using cyan, and the roughness was evaluated visually.

[0294] G1: No roughness was felt.

[0295] G2: Roughness is slightly felt in low-density images.

[0296] G3: Roughness is slightly felt in low-density and medium-density images.

[0297] G4: Roughness is felt from low-density images to high-density images.

[0298] [Table 1]

[0299]

[0300] The electrophotographic photoreceptor, the method for producing the electrophotographic photoreceptor, the process cartridge, and the image forming apparatus of the present invention include the following aspects.

[0301] (1) An electrophotographic photoreceptor comprising a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, wherein:

[0302] In a power spectrum obtained by fast Fourier transforming a roughness curve in the axial direction of the outer peripheral surface of the conductive substrate, the integrated value of the intensity in the range of a period of 0.01 mm to 0.1 mm is 0.02 to 0.10.

[0303] The undercoat layer has a thickness of 10 μm or more.

[0304] (2) The electrophotographic photoreceptor according to (1), wherein

[0305] The undercoat layer has a thickness of 20 μm or more.

[0306] (3) An electrophotographic photoreceptor comprising a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, wherein:

[0307] In a power spectrum obtained by fast Fourier transforming a roughness curve in the axial direction of the outer peripheral surface of the conductive substrate, the integrated value of the intensity in the range of a period of 0.01 mm to 0.1 mm is 0.02 to 0.10.

[0308] The undercoat layer contains metal oxide particles.

[0309] (4) The electrophotographic photoreceptor according to (3), wherein

[0310] The metal oxide particles include at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, and tin oxide particles.

[0311] (5) The electrophotographic photoreceptor according to (3) or (4), wherein

[0312] The metal oxide particles have an average particle size of 10 nm or more and 80 nm or less.

[0313] (6) The electrophotographic photoreceptor according to any one of (3) to (5), wherein

[0314] The mass ratio of the metal oxide particles in the undercoat layer is 60 mass % or more and 95 mass % or less.

[0315] (7) A method for producing an electrophotographic photoreceptor, which is a method for producing the electrophotographic photoreceptor according to any one of (1) to (6), the method comprising the following steps:

[0316] Regenerating the conductive substrate by removing all layers on the conductive substrate from the used electrophotographic photoreceptor by spraying water;

[0317] forming an undercoat layer on the regenerated conductive substrate; and

[0318] A photosensitive layer is formed on the undercoat layer.

[0319] (8) A process cartridge comprising the electrophotographic photoreceptor according to any one of (1) to (6), wherein:

[0320] The process cartridge is attachable to and detachable from the image forming apparatus.

[0321] (9) An image forming apparatus comprising:

[0322] The electrophotographic photoreceptor according to any one of (1) to (6);

[0323] A charging device for charging the surface of the electrophotographic photoreceptor;

[0324] An electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

[0325] a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and

[0326] The transfer device transfers the toner image to the surface of a recording medium.

[0327] According to (1), there is provided an electrophotographic photoreceptor that forms an image having excellent granularity compared with an electrophotographic photoreceptor in which the thickness of the undercoat layer is less than 10 μm and the undercoat layer does not contain metal oxide particles.

[0328] According to (2), there is provided an electrophotographic photoreceptor capable of forming an image having excellent graininess compared with an electrophotographic photoreceptor having an undercoat layer having a thickness of less than 20 μm.

[0329] According to (3), (4), (5) or (6), there is provided an electrophotographic photoreceptor that forms an image with excellent granularity compared with an electrophotographic photoreceptor having an undercoat layer thickness of less than 10 μm and containing no metal oxide particles.

[0330] According to (7), a method for producing an electrophotographic photoreceptor capable of forming an image having excellent granularity is provided.

[0331] According to (8), there is provided a process cartridge capable of forming an image having excellent granularity compared with a process cartridge having an electrophotographic photoreceptor having an undercoat layer having a thickness of less than 10 μm and containing no metal oxide particles in the undercoat layer.

[0332] According to (9), there is provided an image forming apparatus that forms an image with excellent granularity compared to an image forming apparatus including an electrophotographic photoreceptor having an undercoat layer having a thickness of less than 10 μm and containing no metal oxide particles.

[0333] The above-mentioned embodiments of the present invention are provided for the purpose of illustration and description. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed methods. Obviously, various modifications and changes are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily understand the principles of the present invention and its application. Thus, other technicians in the art can understand the present invention through various variations optimized for specific uses assumed to be various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

Claims

1. An electrophotographic photoreceptor comprising a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, wherein: In a power spectrum obtained by fast Fourier transforming a roughness curve in the axial direction of the outer peripheral surface of the conductive substrate, the integrated value of the intensity in the range of a period of 0.01 mm to 0.1 mm is 0.02 to 0.

10. The undercoat layer has a thickness of 10 μm or more.

2. The electrophotographic photoreceptor according to claim 1, wherein The undercoat layer has a thickness of 20 μm or more.

3. An electrophotographic photoreceptor comprising a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, wherein: In a power spectrum obtained by fast Fourier transforming a roughness curve in the axial direction of the outer peripheral surface of the conductive substrate, the integrated value of the intensity in the range of a period of 0.01 mm to 0.1 mm is 0.02 to 0.

10. The undercoat layer contains metal oxide particles.

4. The electrophotographic photoreceptor according to claim 3, wherein The metal oxide particles include at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, and tin oxide particles.

5. The electrophotographic photoreceptor according to claim 3 or 4, wherein The metal oxide particles have an average particle size of 10 nm or more and 80 nm or less.

6. The electrophotographic photoreceptor according to any one of claims 3 to 5, wherein The mass ratio of the metal oxide particles in the undercoat layer is 60 mass % or more and 95 mass % or less.

7. A method for manufacturing an electrophotographic photoreceptor, which is a method for manufacturing the electrophotographic photoreceptor according to any one of claims 1 to 6, the method for manufacturing the electrophotographic photoreceptor comprising the following steps: Regenerating the conductive substrate by removing all layers on the conductive substrate from the used electrophotographic photoreceptor by spraying water; forming an undercoat layer on the regenerated conductive substrate; and A photosensitive layer is formed on the undercoat layer.

8. A process cartridge comprising the electrophotographic photoreceptor according to any one of claims 1 to 6, wherein: The process cartridge is attachable to and detachable from the image forming apparatus.

9. An image forming apparatus comprising: The electrophotographic photoreceptor according to any one of claims 1 to 6; A charging device for charging the surface of the electrophotographic photoreceptor; An electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and The transfer device transfers the toner image to the surface of a recording medium.

Images