Electronic photography photoreceptor, process cartridge, and image forming device

Abstract

To provide a electronic photography photoreceptor which hardly causes contamination of a charging member and abnormal noise due to vibration of a photoreceptor cleaning blade over a long period of time.SOLUTION: The electrophotographic photoreceptor includes a conductive substrate and a photosensitive layer disposed on the conductive substrate, wherein the outermost layer contains a charge transport material, two or more kinds of resins and a phenolic compound, and RzJIS of the outer peripheral face is 0. 1nm or more and 100nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus. [Background technology]

[0002] Patent Document 1 describes a method for manufacturing an image bearing member having a Vickers hardness of 714,000 to 1,326,500 N / cm 2 The image forming apparatus is disclosed in which the average surface roughness Ra of the image carrier within a 10 μm×10 μm area is 1.0 nm or more and 9.0 nm or less, and a cleaning-less system is provided that omits a cleaning member that scrapes off untransferred toner remaining on the surface of the image carrier.

[0003] Patent Document 2 discloses an image forming apparatus in which the ten-point average surface roughness (Rz) of the surface of an electrophotographic photosensitive member is 1.00 μm or less.

[0004] Patent Document 3 discloses an electrophotographic photoreceptor in which the convex portions on the uneven outermost surface of the photoreceptor are smoothly curved. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-108420 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-43709 [Patent Document 3] Japanese Patent Application Publication No. 7-92697 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide an electrophotographic photoreceptor that is less likely to cause contamination of a charging member and abnormal noise due to vibration of a photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor having an RzJIS of less than 0.1 nm or more than 100 nm on the outer peripheral surface. [Means for solving the problem]

[0007] Specific means for solving the above problems include the following aspects: Each formula is the same as the formula with the same number described below.

[0008] <1> A conductive substrate and a photosensitive layer disposed on the conductive substrate, the outermost layer contains a charge transport material, two or more types of resin, and a phenol compound; The RzJIS of the outer surface is 0.1 nm or more and 100 nm or less. Electrophotographic photoreceptor. <2> The RzJIS of the outer peripheral surface is 0.5 nm or more and 50 nm or less. <1> The electrophotographic photoreceptor according to claim 1. <3> The phenol compound includes a hindered phenol compound. <1> or <2> The electrophotographic photoreceptor according to claim 1. <4> The two or more resins include at least one of a polyarylate resin and a polycarbonate resin. <1> ~ <3> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <5> The two or more resins include a polyarylate resin having a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B). <1> ~ <4> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <6> The dicarboxylic acid unit represented by formula (A) includes at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by formula (A1), a dicarboxylic acid unit (A2) represented by formula (A2), a dicarboxylic acid unit (A3) represented by formula (A3), a dicarboxylic acid unit (A4) represented by formula (A4), and a dicarboxylic acid unit (A5) represented by formula (A5). <5> The electrophotographic photoreceptor according to claim 1. <7> The diol unit represented by formula (B) includes at least one selected from the group consisting of a diol unit (B1) represented by formula (B1), a diol unit (B2) represented by formula (B2), a diol unit (B3) represented by formula (B3), a diol unit (B4) represented by formula (B4), a diol unit (B5) represented by formula (B5), a diol unit (B6) represented by formula (B6), a diol unit (B7) represented by formula (B7), and a diol unit (B8) represented by formula (B8). <5> or <6> The electrophotographic photoreceptor according to claim 1. <8> the outermost layer contains a polyarylate resin and a polycarbonate resin; <1> ~ <7> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <9> The polyarylate resin and the polycarbonate resin each have a structural unit containing biphenyl represented by formula (BP): <8> The electrophotographic photoreceptor according to claim 1. <10> the proportion of the polyarylate resin in the total amount of the polyarylate resin and the polycarbonate resin contained in the outermost layer is 25% by mass or more and 75% by mass or less; <8> or <9> The electrophotographic photoreceptor according to claim 1. <11> the photosensitive layer has a charge generating layer and a charge transport layer, and the charge transport layer is the outermost layer; <1> ~ <10> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <12> <1> ~ <11> The electrophotographic photoreceptor according to any one of the above items is provided, Attaching to and detaching from the image forming device Process cartridge. <13> <1> ~ <11> an electrophotographic photoreceptor according to any one of the above items; a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; a cleaning device having a cleaning blade that comes into contact with the surface of the electrophotographic photosensitive member and that cleans the surface of the electrophotographic photosensitive member, Image forming device. [Effects of the Invention]

[0009] <1> , <3> , <4> , <5> , <6> , <7> or <11> According to this, an electrophotographic photoreceptor is provided that is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor having an RzJIS of less than 0.1 nm or more than 100 nm on the outer peripheral surface. <2> According to this, an electrophotographic photoreceptor is provided that is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor having an RzJIS of less than 0.5 nm or more than 50 nm on the outer peripheral surface. <8> According to the present invention, an electrophotographic photoreceptor is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to a configuration in which the outermost surface layer contains only one of a polyarylate resin and a polycarbonate resin. <9> According to the present invention, an electrophotographic photoreceptor is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to a configuration in which at least one of the polyarylate resin and the polycarbonate resin does not have a structural unit containing biphenyl represented by formula (BP). <10> According to the present invention, an electrophotographic photoreceptor is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor in which the proportion of polyarylate resin in the total amount of polyarylate resin and polycarbonate resin contained in the outermost surface layer is less than 25 mass % or more than 75 mass %. <12> According to the present invention, a process cartridge is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photosensitive member cleaning blade over a long period of time compared to a process cartridge in which the RzJIS of the outer peripheral surface of the electrophotographic photosensitive member is less than 0.1 nm or more than 100 nm. <13> According to the present invention, an image forming apparatus is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photosensitive member cleaning blade over a long period of time, compared to an image forming apparatus in which the RzJIS of the outer peripheral surface of the electrophotographic photosensitive member is less than 0.1 nm or more than 100 nm. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a partial cross-sectional view showing an example of a layer structure of the electrophotographic photosensitive member according to the first embodiment. [Figure 2] FIG. 6 is a partial cross-sectional view showing an example of a layer structure of an electrophotographic photosensitive member according to a second embodiment. [Figure 3] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 4] FIG. 10 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0023] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0012] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0013] In the present disclosure, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B.

[0014] In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0015] When embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these.

[0016] In the present disclosure, each component may contain multiple corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified. In the present disclosure, the composition may contain multiple types of particles corresponding to each component. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0017] In the present disclosure, alkyl groups and alkylene groups include any of linear, branched and cyclic groups, unless otherwise specified. In the present disclosure, a hydrogen atom in an organic group, aromatic ring, linking group, alkyl group, alkylene group, aryl group, aralkyl group, alkoxy group, aryloxy group, or the like may be substituted with a halogen atom.

[0018] In the present disclosure, when a compound is represented by a structural formula, the symbols (C and H) representing carbon atoms and hydrogen atoms in the hydrocarbon group and / or hydrocarbon chain may be omitted.

[0019] In the present disclosure, the term "structural unit" of a copolymer or resin has the same meaning as a monomer unit.

[0020] <Electrophotographic photoreceptor> The electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") according to this embodiment includes a conductive substrate and a photosensitive layer disposed on the conductive substrate.

[0021] FIG. 1 is a partial cross-sectional view schematically illustrating an example of the layer structure of a photoreceptor according to this embodiment. Photoreceptor 10A shown in FIG. 1 has a laminated photosensitive layer. Photoreceptor 10A has a structure in which an undercoat layer 2, a charge generation layer 3, and a charge transport layer 4 are laminated in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute a photosensitive layer 5 (a so-called function-separated photosensitive layer). Photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3. The undercoat layer 2 may or may not be present.

[0022] Fig. 2 is a partial cross-sectional view schematically showing another example of the layer structure of the photoreceptor according to this embodiment. The photoreceptor 10B shown in Fig. 2 has a single-layer photosensitive layer. The photoreceptor 10B has a structure in which an undercoat layer 2 and a photosensitive layer 5 are laminated in this order 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 undercoat layer 2 may or may not be present.

[0023] The photoreceptor according to this embodiment has an outermost layer containing a charge transport material, two or more types of resin, and a phenol compound, and the outer peripheral surface has an RzJIS of 0.1 nm to 100 nm. The outer peripheral surface of the photoreceptor is the exposed surface of the outermost layer of the photoreceptor.

[0024] An example of an embodiment of the photoreceptor has a laminated photosensitive layer in which a charge generating layer and a charge transport layer are laminated, and the charge transport layer is the outermost layer and forms the outer peripheral surface. Another example of an embodiment of the photoreceptor has a single-layer photosensitive layer, which is the outermost layer and forms the outer peripheral surface.

[0025] The method for measuring RzJIS of the outer peripheral surface of the photoreceptor is as follows. The outermost layer is peeled off from the photoreceptor and attached to a flat plate with double-sided tape. The outermost layer on the plate is subjected to static electricity removal treatment, and this is used as a sample. The static electricity removal treatment is performed for 15 minutes using, for example, a static electricity removal blower SIB-10DC (AS ONE Corporation). The surface of the sample is scanned using an atomic force microscope (AFM) under the following measurement conditions to obtain three-dimensional data of the surface shape. Atomic force microscope: AFM5200S, Hitachi High-Tech Corporation Cantilever: SI-DF40, Hitachi High-Tech Fielding Corporation Measurement mode: Dynamic force mode Measurement data type: Shape image ·Measurement area: 5μm×5μm After flattening the three-dimensional data of the surface shape in the X-axis and Y-axis directions, a line profile is taken in the Z-axis direction to determine the ten-point average roughness RzJIS (JIS B0601).

[0026] The photoreceptor according to this embodiment has an outermost layer containing a charge transport material, two or more types of resin, and a phenolic compound, and an outer peripheral surface with an RzJIS of 0.1 nm to 100 nm, which makes it difficult for the charging member to be contaminated and for the photoreceptor cleaning blade to make abnormal noise (so-called "blade squeal") due to vibration over a long period of time. The mechanism behind this is presumed to be as follows.

[0027] Conventionally, fluororesin particles have been incorporated into the outermost layer of a photoreceptor in order to reduce the coefficient of friction of the outer peripheral surface of the photoreceptor. However, since restrictions on the production and use of organic fluorine compounds are likely to become stricter in the future, there is a demand for a technology that can replace the internal addition of fluororesin particles. Another method for reducing the coefficient of friction on the outer peripheral surface of a photoreceptor is to polish the outer peripheral surface to form minute irregularities, but the irregularities formed by polishing wear away with use of the photoreceptor, so the coefficient of friction on the outer peripheral surface of the photoreceptor gradually increases. In contrast, the photoreceptor according to this embodiment has an outermost surface layer containing two or more types of resins and a phenolic compound, thereby reducing the coefficient of friction of the outer surface. During the formation of the outermost surface layer, the phenolic compound promotes phase separation between the two or more types of resins, resulting in the formation of a nano-order fine phase-separated structure within the outermost surface layer. This fine phase-separated structure creates fine irregularities on the outer surface of the photoreceptor, thereby reducing the coefficient of friction. Furthermore, because a fine phase-separated structure also exists within the outermost surface layer, even if the outermost surface layer wears with use of the photoreceptor, new fine irregularities appear on the outer surface, thereby reducing the coefficient of friction. Additionally, lubricating components contained in the toner (e.g., higher fatty acid metal salts as external additives, hydrophobic treatment agents (e.g., silicone oils) present on the surfaces of external additive particles, etc.) penetrate into the fine irregularities on the outer surface of the photoreceptor, thereby reducing the coefficient of friction. The photoreceptor according to this embodiment can maintain a low coefficient of friction, so that the cleaning performance of the outer peripheral surface of the photoreceptor with a cleaning blade is good for a long period of time, and as a result, contamination of the charging member and blade noise of the photoreceptor cleaning blade are unlikely to occur for a long period of time. Contamination of charging members is likely to occur in charging members that come into contact with the outer peripheral surface of the photosensitive member, but can also occur in charging members that do not come into contact with the outer peripheral surface of the photosensitive member, as they electrostatically adsorb contaminants.

[0028] The photoreceptor according to this embodiment has an outer peripheral surface with a RzJIS of 0.1 nm or more and 100 nm or less. If the RzJIS of the outer peripheral surface is less than 0.1 nm, the outer peripheral surface will be too smooth, resulting in a high coefficient of friction. Furthermore, if the RzJIS of the outer peripheral surface is less than 0.1 nm, it is presumed that the lubricating components contained in the toner will not be sufficiently retained. From the viewpoint of suppressing the coefficient of friction, the RzJIS of the outer peripheral surface is 0.1 nm or more, preferably 0.3 nm or more, more preferably 0.5 nm or more, and even more preferably 1 nm or more. If the RzJIS of the outer peripheral surface exceeds 100 nm, the unevenness will be too large and the coefficient of friction will be high. From the viewpoint of suppressing the coefficient of friction, the RzJIS of the outer peripheral surface is 100 nm or less, preferably 80 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less.

[0029] The RzJIS of the outer peripheral surface of the photoreceptor can be controlled within the range of 0.1 nm to 100 nm by using a composition containing two or more resins and a phenolic compound to form the outermost layer. In this case, the RzJIS value can be controlled by adjusting the combination and mass ratio of the two or more resins and the amount of the phenolic compound used.

[0030] [Top surface layer] The outermost layer of the photoreceptor contains a charge transport material, two or more types of resin, and a phenol compound.

[0031] The charge transport material contained in the outermost surface layer may be the same compound as the charge transport material contained in the charge transport layer described later, and the preferred compounds are also the same.

[0032] Examples of resins contained in the outermost surface layer include polyarylate resin, polycarbonate resin, polyester resin other than 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-vinylcarbazole, polysilane, etc. Any combination of two or more of these resins may be used.

[0033] The resin contained in the outermost layer preferably contains at least one of a polyarylate resin and a polycarbonate resin, more preferably a polyarylate resin and a polycarbonate resin, from the viewpoint of the abrasion resistance of the outermost layer. The embodiment containing a polyarylate resin and a polycarbonate resin is also preferred from the viewpoint of forming a fine phase-separated structure in the outermost layer.

[0034] The proportion of the polyarylate resin in the total amount of the polyarylate resin and the polycarbonate resin contained in the outermost layer of the photoreceptor is preferably 20% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 75% by mass or less, and even more preferably 30% by mass or more and 70% by mass or less, from the viewpoint of forming a fine phase-separated structure in the outermost layer.

[0035] In polyarylate resins, resin molecules are bound together by intermolecular forces due to stacking of aromatic rings, improving the abrasion resistance of the outermost surface layer. Polyarylate resins are preferably polycondensates of bisphenols and aromatic dicarboxylic acids. A preferred example of polyarylate resins is polyarylate resin (PA), which will be described later.

[0036] As the polycarbonate resin, a polycarbonate resin having a continuous structural unit having an aromatic ring is preferred. In this polycarbonate resin, resin molecules are bound to each other by intermolecular forces due to stacking of aromatic rings, improving the abrasion resistance of the outermost surface layer. Specific examples of preferred forms of polycarbonate resin include the polycarbonate resin disclosed in JP 2023-121553 A. More preferred forms of polycarbonate resin include the polycarbonate resin used in the examples described below.

[0037] A preferred combination of a polyarylate resin and a polycarbonate resin is one in which both resins have a biphenyl-containing structural unit represented by the following formula (BP).

[0038] [ka]

[0039] In formula (BP), j is an integer of 0 to 4, and j R 1 are each independently a methyl group or an ethyl group, k is an integer of 0 to 4, and k R 2 are each independently a methyl group or an ethyl group.

[0040] The biphenyl represented by formula (BP) may be the entire structure or a part thereof obtained by removing the ester bond (-C(=O)O-) or carbonate bond (-OC(=O)O-) from a structural unit containing the biphenyl represented by formula (BP). In other words, the right and left ends of the biphenyl represented by formula (BP) may each independently be bonded directly to an ester bond or a carbonate bond, or may be bonded to an ester bond or a carbonate bond via another atom or atomic group.

[0041] j is an integer of 0 or more and 4 or less, preferably an integer of 0 or more and 3 or less, more preferably an integer of 0 or more and 2 or less, further preferably 0 or 1, and particularly preferably 0. When j is an integer equal to or greater than 1, j R1 are each independently a methyl group or an ethyl group, and are preferably a methyl group.

[0042] k is an integer of 0 or more and 4 or less, preferably an integer of 0 or more and 3 or less, more preferably an integer of 0 or more and 2 or less, even more preferably 0 or 1, and particularly preferably 0. When k is an integer equal to or greater than 1, k R 2 are each independently a methyl group or an ethyl group, and are preferably a methyl group.

[0043] The biphenyl represented by formula (BP) is preferably 4,4'-biphenyl with respect to the linking position in the main chain.

[0044] As a combination of a polyarylate resin and a polycarbonate resin, a combination of a polyarylate resin having at least one of a dicarboxylic acid unit (A2-3) and a diol unit (B7-1) with a polycarbonate resin having a structural unit (Cb7-1) is particularly preferred.

[0045] [ka]

[0046] Examples of the phenol compound contained in the outermost surface layer include phenol, cresol, catechol, resorcinol, hydroquinone, naphthol, bisphenol (bisphenol A, AP, AF, B, BP, C, C2, E, F, G, M, S, P, PH, TMC, Z), etc. One type of phenol compound may be used alone, or two or more types may be used in combination.

[0047] The phenol compound contained in the outermost surface layer may also be a hindered phenol compound. From the viewpoint of suppressing oxidative deterioration of the outermost surface layer, the phenol compound contained in the outermost surface layer preferably contains a hindered phenol compound. A hindered phenol compound is generally a compound in which at least one of the ortho positions of a phenol hydroxy group is substituted with a bulky group, and is known to exhibit an oxidation suppression effect on the composition.

[0048] Examples of the hindered phenol compound include the following. Alkylated monophenolic compounds and their derivatives: for example, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, octyl-3,5-di-t-butyl-4-hydroxy-hydrocinnamate Alkylated hydroquinone compounds and their derivatives: for example, 2,5-di-t-butylhydroquinone, 2,5-di-t-amylhydroquinone Alkylthiomethylphenol compounds and their derivatives: for example, 2,4-dioctylthiomethyl-6-t-butylphenol, 2,4-dioctylthiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, 2,6-didodecylthiomethyl-4-nonylphenol Alkylidenebisphenol compounds and their derivatives: for example, 4,4'-butylidenebis(6-t-butyl-3-methylphenol), 2,2'-methylenebis(6-t-butyl-4-methylphenol), 2,2'-methylenebis(6-t-butyl-4-ethylphenol), 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 3,9-bis[2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane

[0049] Commercially available hindered phenol compounds include "ADK STAB AO-80," "ADK STAB AO-60," "ADK STAB AO-50," "ADK STAB AO-40," "ADK STAB AO-30," "ADK STAB AO-20," and "ADK STAB AO-330" from ADEKA Corporation; "Irganox 1010," "Irganox 245," "Irganox 1076," and "Irganox 1520" from BASF Japan Ltd.; and "Sumilizer GA-80," "Sumilizer GM," and "Sumilizer GS" from Sumitomo Chemical Co., Ltd.

[0050] The hindered phenol compounds may be used alone or in combination of two or more.

[0051] The content of the phenol compound contained in the outermost layer is preferably from 0.1% by mass to 20% by mass, more preferably from 0.5% by mass to 10% by mass, and even more preferably from 1% by mass to 5% by mass, relative to the total mass of the outermost layer, from the viewpoint of promoting phase separation of two or more types of resins during formation of the outermost layer and forming a fine phase-separated structure in the outermost layer.

[0052] The proportion of fluororesin particles in the outermost layer of the photoreceptor is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass (i.e., no fluororesin particles are contained). Since there is a high possibility that restrictions on the production and use of organic fluorine compounds will become stricter in the future, the content of the fluororesin particles is preferably within the above range.

[0053] The thickness of the outermost layer may be set depending on the function of the layer. When the charge transport layer is the outermost layer, the thickness of the outermost layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 40 μm or less, and even more preferably 10 μm or more and 30 μm or less. When the single-layer photosensitive layer is the outermost layer, the thickness of the outermost layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 45 μm or less, and even more preferably 10 μm or more and 40 μm or less.

[0054] The method for forming the outermost surface layer is the same as the method for forming the charge transport layer and the method for forming the single-layer photosensitive layer, which will be described later.

[0055] [Polyarylate resin (PA)] The polyarylate resin contained in the outermost layer is preferably a polyarylate resin having at least a dicarboxylic acid unit (A) and a diol unit (B). In the present disclosure, such a polyarylate resin is referred to as polyarylate resin (PA).

[0056] The dicarboxylic acid unit (A) is a structural unit represented by the following formula (A).

[0057] [ka]

[0058] In formula (A), Ar A1 and Ar A2 each independently represents an aromatic ring which may have a substituent, and L A is a single bond or a divalent linking group, and n A1 is 0, 1 or 2.

[0059] Ar A1 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0060] Ar A1 The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. A1When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0061] Ar A2 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0062] Ar A2 The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. A2 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0063] L A When is a divalent linking group, examples of the divalent linking group include an oxygen atom, a sulfur atom, -C(Ra 1 )(Ra 2 )-, where Ra 1 and Ra 2 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms; 1 and Ra 2 may be bonded to form a cyclic alkyl group.

[0064] Ra 1 and Ra 2 The alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0065] Ra 1 and Ra 2The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0066] Ra 1 and Ra 2 The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Ra 1 and Ra 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, more preferably 6.

[0067] The dicarboxylic acid unit (A) preferably contains at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by the following formula (A1), a dicarboxylic acid unit (A2) represented by the formula (A2), a dicarboxylic acid unit (A3) represented by the formula (A3), a dicarboxylic acid unit (A4) represented by the formula (A4), and a dicarboxylic acid unit (A5) represented by the formula (A5). The dicarboxylic acid unit (A) more preferably contains at least one selected from the group consisting of the dicarboxylic acid unit (A2), the dicarboxylic acid unit (A3), and the dicarboxylic acid unit (A4), and further preferably contains the dicarboxylic acid unit (A2).

[0068] [ka]

[0069] In formula (A1), n 101 is an integer between 0 and 4, and n 101 Ra 101 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 101is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0070] [ka]

[0071] In formula (A2), n 201 and n 202 are each independently an integer of 0 to 4, 201 Ra 201 and n 202 Ra 202 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 201 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. n 202 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0072] [ka]

[0073] In formula (A3), n 301 and n 302 are each independently an integer of 0 to 4, 301 Ra 301 and n 302 Ra 302 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 301 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. n 302 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0074] [ka]

[0075] In formula (A4), n 401 is an integer between 0 and 6, and n 401 Ra 401 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 401 is preferably an integer of 0 or more and 4 or less, more preferably 0, 1 or 2, and even more preferably 0. It is more preferable that:

[0076] [ka]

[0077] In formula (A5), n 501 , n 502 and n 503 are each independently an integer of 0 to 4, 501 Ra 501 , n 502 Ra 502 and n 503 Ra 503 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 501 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. n 502 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. n 503 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0078] Ra in formula (A1) 101 , Ra in formula (A2) 201 and Ra 202 , Ra in formula (A3) 301 and Ra 302 , Ra in formula (A4) 401 and Ra in formula (A5) 501 , Ra 502 and Ra 503 Since the specific and preferred embodiments of Ra are the same as those of 101 , Ra 201 , Ra 202 , Ra 301 , Ra 302 , Ra 401 , Ra 501 , Ra 502 and Ra 503 These will be collectively referred to as "Ra".

[0079] The alkyl group having 1 to 10 carbon atoms represented by Ra may be linear, branched, or cyclic. The alkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms. Examples of the linear alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group. Examples of branched alkyl groups having 3 to 10 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group. Examples of the cyclic alkyl group having 3 to 10 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl groups formed by linking these monocyclic alkyl groups.

[0080] The aryl group having 6 to 12 carbon atoms for Ra may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a biphenyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0081] The alkyl group in the alkoxy group having 1 to 6 carbon atoms, represented by Ra, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0082] Specific examples of the dicarboxylic acid unit (A1) include dicarboxylic acid units (A1-1) to (A1-9), but the dicarboxylic acid unit (A1) is not limited thereto.

[0083] [ka]

[0084] Specific examples of the dicarboxylic acid unit (A2) include dicarboxylic acid units (A2-1) to (A2-3), but the dicarboxylic acid unit (A2) is not limited thereto.

[0085] [ka]

[0086] Specific examples of the dicarboxylic acid unit (A3) include dicarboxylic acid units (A3-1) and (A3-2), but the dicarboxylic acid unit (A3) is not limited thereto.

[0087] [ka]

[0088] Specific examples of the dicarboxylic acid unit (A4) include dicarboxylic acid units (A4-1) to (A4-3), but the dicarboxylic acid unit (A4) is not limited thereto.

[0089] [ka]

[0090] Specific examples of the dicarboxylic acid unit (A5) include dicarboxylic acid units (A5-1) to (A5-4), but the dicarboxylic acid unit (A5) is not limited thereto.

[0091] [ka]

[0092] The dicarboxylic acid unit (A) preferably contains at least one selected from the group consisting of the above specific examples (A1-1), (A1-7), (A2-3), (A3-2) and (A4-3), more preferably contains at least one selected from the group consisting of (A2-3), (A3-2) and (A4-3), and even more preferably contains at least (A2-3).

[0093] The dicarboxylic acid units (A) contained in the polyarylate resin (PA) may be of one type or two or more types.

[0094] The mass proportion of the dicarboxylic acid units (A) in the polyarylate resin (PA) is preferably 15 mass % or more and 60 mass % or less. When the mass proportion of the dicarboxylic acid units (A) is 15 mass% or more, the outermost layer has good abrasion resistance. From this viewpoint, the mass proportion of the dicarboxylic acid units (A) is more preferably 20 mass% or more, and further preferably 25 mass% or more. When the mass proportion of the dicarboxylic acid unit (A) is 60 mass% or less, peeling of the outermost surface layer can be suppressed. From this viewpoint, the mass proportion of the dicarboxylic acid unit (A) is more preferably 55 mass% or less, and even more preferably 50 mass% or less.

[0095] The polyarylate resin (PA) may contain dicarboxylic acid units other than the dicarboxylic acid units (A). Examples of the other dicarboxylic acid units include aliphatic dicarboxylic acid units (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acid units (e.g., cyclohexanedicarboxylic acid), and lower alkyl ester units thereof (e.g., having 1 to 5 carbon atoms). The polyarylate resin (PA) may contain one or more types of these dicarboxylic acid units.

[0096] The diol unit (B) is a structural unit represented by the following formula (B).

[0097] [ka]

[0098] In formula (B), Ar B1 and Ar B2 each independently represents an aromatic ring which may have a substituent, and L B is a single bond, an oxygen atom, a sulfur atom, or -C(Rb 1 )(Rb 2 )- and n B1 is 0, 1 or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may be bonded to form a cyclic alkyl group.

[0099] Ar B1 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0100] Ar B1 The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. B1 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0101] Ar B2 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0102] Ar B2The hydrogen atoms on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. B2 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0103] Rb 1 and Rb 2 The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 18 carbon atoms, more preferably 1 to 14 carbon atoms, and even more preferably 1 to 10 carbon atoms.

[0104] Rb 1 and Rb 2 The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0105] Rb 1 and Rb 2 The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Rb 1 and Rb 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, more preferably 6.

[0106] The diol unit (B) preferably contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the formula (B2), a diol unit (B3) represented by the formula (B3), a diol unit (B4) represented by the formula (B4), a diol unit (B5) represented by the formula (B5), a diol unit (B6) represented by the formula (B6), a diol unit (B7) represented by the formula (B7), and a diol unit (B8) represented by the formula (B8).

[0107] It is more preferable that the diol unit (B) contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the formula (B2), a diol unit (B4) represented by the formula (B4), a diol unit (B5) represented by the formula (B5), and a diol unit (B6) represented by the formula (B6): It is more preferable that the diol unit (B1) contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the following formula (B2), a diol unit (B5) represented by the following formula (B5), and a diol unit (B6) represented by the following formula (B6): It is even more preferable that the diol unit (B1) contains at least one selected from the group consisting of a diol unit (B2) represented by the following formula (B1), a diol unit (B2) represented by the following formula (B2), and a diol unit (B6) represented by the following formula (B6): It is most preferable that the diol unit (B1) contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1) and a diol unit (B2) represented by the following formula (B2).

[0108] [ka]

[0109] In formula (B1), Rb 101 is a branched alkyl group having 4 to 20 carbon atoms, and Rb 201 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 401 , Rb 501 , Rb801 and Rb 901 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0110] Rb 101 The number of carbon atoms in the branched alkyl group having 4 to 20 carbon atoms in the formula Rb is preferably 4 to 16, more preferably 4 to 12, and even more preferably 4 to 8. 101 Specific examples of the aryl group include an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, an isododecyl group, a sec-dodecyl group, a tert-dodecyl group, a tert-tetradecyl group, and a tert-pentadecyl group.

[0111] [ka]

[0112] In formula (B2), Rb 102 is a linear alkyl group having 4 to 20 carbon atoms, and Rb 202 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 402 , Rb 502 , Rb 802 and Rb 902 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0113] Rb 102 The carbon number of the linear alkyl group having 4 to 20 carbon atoms in the formula (Rb) is preferably 4 to 16, more preferably 4 to 12, and even more preferably 4 to 8. 102Specific examples of the alkyl group include an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, a tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, and an n-icosyl group.

[0114] [ka]

[0115] In formula (B3), Rb 113 and Rb 213 are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; d is an integer of 7 to 15; Rb 403 , Rb 503 , Rb 803 and Rb 903 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0116] Rb 113 and Rb 213 The number of carbon atoms in the linear alkyl group having 1 to 3 carbon atoms is preferably 1 or 2, and more preferably 1. Specific examples of such groups include a methyl group, an ethyl group, and an n-propyl group. Rb 113 and Rb 213 The alkyl group in the alkoxy group having from 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 4 carbon atoms is preferably from 1 to 3, more preferably 1 or 2, and even more preferably 1. Specific examples of such groups include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a cyclopropoxy group, and a cyclobutoxy group. Rb 113 and Rb 213Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0117] [ka]

[0118] In formula (B4), Rb 104 and Rb 204 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 404 , Rb 504 , Rb 804 and Rb 904 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0119] Rb 104 The alkyl group having 1 to 3 carbon atoms in the formula (1) may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or 2, and more preferably 1. 104 Specific examples of the group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

[0120] [ka]

[0121] In formula (B5), Ar 105 is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 205 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 405 , Rb 505 , Rb 805 and Rb 905 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0122] Ar 105The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Ar 105 The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Ar 105 The aryl group in the aralkyl group having 7 to 20 carbon atoms according to the above formula may be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Examples of aralkyl groups having 7 to 20 carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, a 4-phenylbutyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, a phenylnonyl group, a naphthylmethyl group, a naphthylethyl group, an anthrathymethyl group, and a phenyl-cyclopentylmethyl group.

[0123] [ka]

[0124] In formula (B6), Rb 116 and Rb 216 are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; e is an integer of 4 to 6; Rb 406 , Rb 506 , Rb 806 and Rb 906 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0125] Rb 116 and Rb 216 The number of carbon atoms in the linear alkyl group having 1 to 3 carbon atoms is preferably 1 or 2, and more preferably 1. Specific examples of such groups include a methyl group, an ethyl group, and an n-propyl group. Rb 116 and Rb 216 The alkyl group in the alkoxy group having from 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 4 carbon atoms is preferably from 1 to 3, more preferably 1 or 2, and even more preferably 1. Specific examples of such groups include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a cyclopropoxy group, and a cyclobutoxy group. Rb 116 and Rb 216 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0126] [ka]

[0127] In formula (B7), Rb 407 , Rb 507 , Rb 807 and Rb 907 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0128] [ka]

[0129] In formula (B8), Rb 408 , Rb 508 , Rb 808 and Rb 908 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0130] Rb in formula (B1) 201 , Rb in formula (B2) 202 , Rb in formula (B4) 204 and Rb of formula (B5) 205Since the specific and preferred embodiments of Rb are the same as those of Rb, 201 , Rb 202 , Rb 204 and Rb 205 "Rb 200 " is collectively referred to as ".

[0131] Rb 200 The alkyl group having 1 to 3 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 or 2 carbon atoms, and more preferably 1 carbon atom. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

[0132] Rb in formula (B1) 401 , Rb in formula (B2) 402 , Rb in formula (B3) 403 , Rb in formula (B4) 404 , Rb in formula (B5) 405 , Rb in formula (B6) 406 , Rb in formula (B7) 407 and Rb of formula (B8) 408 Since the specific and preferred embodiments of Rb are the same as those of Rb, 401 , Rb 402 , Rb 403 , Rb 404 , Rb 405 , Rb 406 , Rb 407 and Rb 408 "Rb 400 " is collectively referred to as ".

[0133] Rb 400 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0134] Rb 400 The alkyl group in the alkoxy group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0135] Rb 400 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0136] Rb in formula (B1) 501 , Rb in formula (B2) 502 , Rb in formula (B3) 503 , Rb in formula (B4) 504 , Rb in formula (B5) 505 , Rb in formula (B6) 506 , Rb in formula (B7) 507 and Rb of formula (B8) 508 Since the specific and preferred embodiments of Rb are the same as those of Rb, 501 , Rb 502 , Rb 503 , Rb 504 , Rb 505 , Rb 506 , Rb 507 and Rb508 "Rb 500 " is collectively referred to as ".

[0137] Rb 500 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0138] Rb 500 The alkyl group in the alkoxy group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0139] Rb 500 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0140] Rb in formula (B1) 801 , Rb in formula (B2) 802 , Rb in formula (B3) 803 , Rb in formula (B4) 804 , Rb in formula (B5) 805 , Rb in formula (B6) 806 , Rb in formula (B7) 807 and Rb of formula (B8) 808 Since the specific and preferred embodiments of Rb are the same as those of Rb, 801 , Rb 802 , Rb 803 , Rb 804 , Rb 805 , Rb 806 , Rb 807 and Rb 808 "Rb 800 " is collectively referred to as ".

[0141] Rb 800 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0142] Rb 800 The alkyl group in the alkoxy group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0143] Rb 800 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0144] Rb in formula (B1) 901 , Rb in formula (B2) 902 , Rb in formula (B3) 903 , Rb in formula (B4) 904 , Rb in formula (B5) 905 , Rb in formula (B6) 906 , Rb in formula (B7) 907 and Rb of formula (B8) 908 Since the specific and preferred embodiments of Rb are the same as those of Rb, 901 , Rb 902 , Rb 903 , Rb 904 , Rb 905 , Rb 906 , Rb 907 and Rb 908 "Rb 900 " is collectively referred to as ".

[0145] Rb 900 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0146] Rb 900 The alkyl group in the alkoxy group having from 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 1 to 3, and even more preferably 1 or 2. Examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of branched alkoxy groups having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0147] Rb 900 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0148] Specific examples of the diol unit (B1) include diol units (B1-1) to (B1-6), but the diol unit (B1) is not limited thereto.

[0149] [ka]

[0150] Specific examples of the diol unit (B2) include diol units (B2-1) to (B2-11), but the diol unit (B2) is not limited thereto.

[0151] [ka]

[0152] Specific examples of the diol unit (B3) include diol units (B3-1) to (B3-4), but the diol unit (B3) is not limited thereto.

[0153] [ka]

[0154] Specific examples of the diol unit (B4) include diol units (B4-1) to (B4-7), but the diol unit (B4) is not limited thereto.

[0155] [ka]

[0156] Specific examples of the diol unit (B5) include diol units (B5-1) to (B5-6), but the diol unit (B5) is not limited thereto.

[0157] [ka]

[0158] Specific examples of the diol unit (B6) include diol units (B6-1) to (B6-4), but the diol unit (B6) is not limited thereto.

[0159] [ka]

[0160] Specific examples of the diol unit (B7) include diol units (B7-1) to (B7-3), but the diol unit (B7) is not limited thereto.

[0161] [ka]

[0162] Specific examples of the diol unit (B8) include diol units (B8-1) to (B8-3), but the diol unit (B8) is not limited thereto.

[0163] [ka]

[0164] The diol unit (B) contained in the polyarylate resin (PA) may be of one type or two or more types.

[0165] The mass proportion of the diol units (B) in the polyarylate resin (PA) is preferably 25 mass % or more and 80 mass % or less. When the mass proportion of the diol units (B) is 25 mass% or more, peeling of the outermost surface layer can be suppressed. From this viewpoint, the mass proportion of the diol units (B) is more preferably 30 mass% or more, and even more preferably 35 mass% or more. When the mass proportion of the diol unit (B) is 80 mass% or less, solubility in a coating liquid for forming the outermost layer can be maintained and abrasion resistance can be improved. From this viewpoint, the mass proportion of the diol unit (B) is more preferably 75 mass% or less, and even more preferably 70 mass% or less.

[0166] The polyarylate resin (PA) may contain other diol units besides the diol units (B). Examples of other diol units include aliphatic diol units (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, and neopentyl glycol) units and alicyclic diol units (e.g., cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A). The polyarylate resin (PA) may contain one or more types of these diol units.

[0167] The terminals of the polyarylate resin (PA) may be blocked or modified with a terminal blocking agent or a molecular weight modifier used during production. Examples of the terminal blocking agent or molecular weight modifier include monohydric phenols, monohydric acid chlorides, monohydric alcohols, and monocarboxylic acids. Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m Examples include o-phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, and 2-phenyl-2-(3-hydroxyphenyl)propane. Examples of the monovalent acid chloride include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetic acid chloride, butyric acid chloride, octylic acid chloride, benzoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and substituted versions thereof. Examples of monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenethyl alcohol. Examples of the monocarboxylic acid include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0168] The weight average molecular weight of the polyarylate resin (PA) is preferably 30,000 or more and 300,000 or less, more preferably 40,000 or more and 250,000 or less, and even more preferably 50,000 or more and 200,000 or less. The molecular weight of polyarylate resin (PA) is the molecular weight in terms of polystyrene measured by GPC (gel permeation chromatography). GPC uses tetrahydrofuran as the eluent.

[0169] Polyarylate resins (PA) can be obtained by conventional polycondensation of a monomer that provides dicarboxylic acid units (A) and a monomer that provides diol units (B), along with other monomers as needed. Examples of methods for polycondensation of monomers include interfacial polymerization, solution polymerization, and melt polymerization. Interfacial polymerization is a polymerization method for obtaining polyesters by mixing a dicarboxylic acid halide dissolved in a water-immiscible organic solvent with a dihydric alcohol dissolved in an alkaline aqueous solution. References related to interfacial polymerization include WMA Reckson, J. Poly. Sci., XL399, 1959, and Japanese Patent Publication No. 1965-1959. Because interfacial polymerization has a faster reaction rate than solution polymerization, it can suppress hydrolysis of the dicarboxylic acid halide, resulting in the production of high-molecular-weight polyarylate resins (PA).

[0170] Each layer of the photoreceptor will be described in detail below.

[0171] [Conductive substrate] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Other examples of conductive substrates include paper, resin films, belts, etc. coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.), or alloys. Here, "conductive" refers to a material having a volume resistivity of 1×10 13 This means that the resistance is less than Ω·cm.

[0172] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center line average roughness Ra of 0.04 μm to 0.5 μm inclusive in order to suppress interference fringes that occur when irradiated with laser light. When incoherent light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for extending the life of the conductive substrate by suppressing defects caused by surface irregularities.

[0173] Examples of methods for roughening the surface include wet honing, which involves spraying an abrasive suspended in water onto the conductive substrate; centerless grinding, which involves pressing the conductive substrate against a rotating grinding wheel and continuously grinding the substrate; and anodizing.

[0174] As a method for roughening the surface, there may be mentioned a method in which, without roughening the surface of the conductive substrate, conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the surface is roughened by the particles dispersed in the layer.

[0175] Anodizing is a surface roughening treatment that uses a metallic (e.g., aluminum) conductive substrate as the anode and anodizes it in an electrolyte solution to form an oxide film on the surface of the conductive substrate. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active in its original state, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film, in which the micropores of the oxide film are sealed by volume expansion caused by hydration in pressurized steam or boiling water (with the addition of a metal salt such as nickel), converting the film into a more stable hydrated oxide.

[0176] The thickness of the anodic oxide film is preferably, for example, from 0.3 μm to 15 μm, inclusive, and within this range, the film tends to exhibit barrier properties against injection and also tends to suppress an increase in residual potential due to repeated use.

[0177] The conductive substrate may be subjected to a treatment with an acidic treatment solution or a boehmite treatment. Treatment with an acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The compounding ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution are, for example, in the range of 10% by mass to 11% by mass for phosphoric acid, 3% by mass to 5% by mass for chromic acid, and 0.5% by mass to 2% by mass for hydrofluoric acid, with the total concentration of these acids preferably in the range of 13.5% by mass to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness of the coating is preferably 0.3 μm to 15 μm.

[0178] The boehmite treatment is carried out, for example, by immersing the steel sheet in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting the steel sheet with heated steam at 90°C to 120°C for 5 to 60 minutes. The coating film preferably has a thickness of 0.1 μm to 5 μm. This may be further anodized using an electrolyte solution with low coating solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0179] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0180] For example, inorganic particles have a powder resistance (volume resistivity) of 1×10 2 Ω cm or more 1×10 11 Examples include inorganic particles with a particle size of Ω·cm or less. Among these, inorganic particles having the above resistance value are preferably metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0181] The specific surface area of ​​inorganic particles measured by the BET method is, for example, 10 m 2 / g or more is preferable. The volume average particle size of the inorganic particles is, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

[0182] The content of the inorganic particles is, for example, preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, relative to the binder resin.

[0183] The inorganic particles may be surface-treated, and two or more types of inorganic particles having different surface treatments or different particle sizes may be used in combination.

[0184] Examples of the surface treatment agent include a silane coupling agent, a titanate-based coupling agent, an aluminum-based coupling agent, a surfactant, etc. In particular, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

[0185] Examples of silane coupling agents 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.

[0186] Two or more silane coupling agents may be used in combination. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, 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.

[0187] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

[0188] The amount of the surface treatment agent to be used is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0189] Here, it is preferable that the undercoat layer contains an electron-accepting compound (acceptor compound) together with the inorganic particles, from the viewpoint of improving the long-term stability of the electrical properties and the carrier blocking property.

[0190] Examples of electron-accepting compounds include electron-transporting substances such as compounds having an anthraquinone structure; quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane 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-t-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-t-butyldiphenoquinone; and benzophenone compounds. In particular, the electron-accepting compound is preferably a compound having an anthraquinone structure, such as a hydroxyanthraquinone compound, an aminoanthraquinone compound, or an aminohydroxyanthraquinone compound, and specifically, for example, anthraquinone, alizarin, quinizarin, anthrarphine, purpurin, or a derivative thereof.

[0191] 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 a state of being attached to the surfaces of the inorganic particles.

[0192] The electron-accepting compound can be attached to the surface of the inorganic particles by, for example, a dry method or a wet method.

[0193] The dry method is a method in which, while stirring inorganic particles using a mixer or the like with high shear force, an electron-accepting compound is added dropwise, either directly or dissolved in an organic solvent, or sprayed together with dry air or nitrogen gas to adhere the electron-accepting compound to the surface of the inorganic particles. The electron-accepting compound is preferably added dropwise or sprayed at a temperature below the boiling point of the solvent. After the electron-accepting compound has been added dropwise or sprayed, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as they achieve electrophotographic properties.

[0194] The wet method is a method in which inorganic particles are dispersed in a solvent using, for example, a stirrer, ultrasonic disperser, sand mill, attritor, or ball mill, while an electron-accepting compound is added, followed by stirring or dispersion, and then the solvent is removed to adhere the electron-accepting compound to the surfaces of the inorganic particles. The solvent can be removed, for example, by filtration or distillation. After solvent removal, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as electrophotographic properties are obtained. In the wet method, moisture contained in the inorganic particles may be removed before adding the electron-accepting compound. Examples of such methods include a method in which the inorganic particles are removed by stirring and heating in a solvent, and a method in which the inorganic particles are removed by azeotropy with the solvent.

[0195] The attachment of the electron-accepting compound may be carried out before or after the inorganic particles are surface-treated with a surface-treating agent, or the attachment of the electron-accepting compound and the surface treatment with a surface-treating agent may be carried out simultaneously.

[0196] The content of the electron-accepting compound is, for example, 0.01% by mass or more and 20% by mass or less, and preferably 0.01% by mass or more and 10% by mass or less, based on the inorganic particles.

[0197] Examples of binder resins used in the undercoat layer include known polymer compounds such as acetal resins (e.g., polyvinyl butyral, etc.), 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, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; and silane coupling agents. Examples of binder resins used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline), and the like.

[0198] Among these, the binder resin used in the undercoat layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and in particular, a resin obtained by reacting at least one resin selected from the group consisting of thermosetting resins such as urea resins, phenolic resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins, and polyamide resins, polyester resins, polyether resins, methacrylic resins, acrylic resins, polyvinyl alcohol resins, and polyvinyl acetal resins with a curing agent is preferred. When two or more of these binder resins are used in combination, the mixing ratio is set as necessary.

[0199] The undercoat layer may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of additives include known materials such as polycyclic condensation and azo electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Silane coupling agents are used for the surface treatment of inorganic particles as described above, and may also be added to the undercoat layer as an additive.

[0200] Examples of silane coupling agents as additives 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.

[0201] Examples of zirconium chelate compounds include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0202] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-normal-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0203] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0204] These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0205] The undercoat layer preferably has a Vickers hardness of 35 or more. The surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to between 1 / (4n) (n is the refractive index of the upper layer) and 1 / 2 of the wavelength λ of the exposure laser used to suppress moiré images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. The surface of the undercoat layer may be polished to adjust the surface roughness. Examples of polishing methods include buffing, sandblasting, wet honing, and grinding.

[0206] The formation of the undercoat layer is not particularly limited, and a known formation method can be used. For example, the undercoat layer can be formed by forming a coating film of a coating liquid for forming the undercoat layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0207] Examples of solvents for preparing the coating liquid for forming the undercoat layer include known organic solvents, such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include ordinary organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0208] Examples of a method for dispersing inorganic particles when preparing a coating liquid for forming an undercoat layer include known methods such as using a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0209] Examples of methods for applying the coating liquid for forming the undercoat layer onto the conductive substrate include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0210] The thickness of the undercoat layer is preferably set to 15 μm or more, more preferably in the range of 20 μm to 50 μm.

[0211] [Middle layer] The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include polymer compounds such as acetal resins (such as 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, and melamine resins. The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used in the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in the intermediate layer may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0212] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0213] The formation of the intermediate layer is not particularly limited, and a known formation method can be used. For example, the intermediate layer can be formed by forming a coating film of a coating liquid for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it if necessary. The intermediate layer can be formed by any of the usual coating methods, such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating.

[0214] The thickness of the intermediate layer is preferably set in the range of 0.1 μm to 3 μm, and the intermediate layer may also be used as an undercoat layer.

[0215] [Charge generation layer] The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Alternatively, the charge generation layer may be a vapor-deposited layer of the charge generation material. A vapor-deposited layer of the charge generation material is suitable for use with an incoherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array.

[0216] Examples of the charge generating material include azo pigments such as bisazo and trisazo; fused-ring aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0217] Among these, in order to be compatible with laser exposure in the near-infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material, specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, or titanyl phthalocyanine.

[0218] On the other hand, in order to accommodate laser exposure in the near ultraviolet region, preferred charge generating materials include fused ring aromatic pigments such as dibromoanthanthrone; thioindigo pigments; porphyrazine compounds; zinc oxide; trigonal selenium; and bisazo pigments.

[0219] The above charge generating material may also be used when an incoherent light source such as an LED or organic EL image array having a central emission wavelength of 450 nm or more and 780 nm or less is used.

[0220] In contrast, when n-type semiconductors such as fused-ring aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark current is less likely to occur, and image defects known as black spots can be suppressed even in thin films. The n-type is determined by the polarity of the photocurrent that flows using the commonly used time-of-flight method, and materials that more easily pass electrons as carriers than holes are considered n-type.

[0221] The binder resin used in the charge generating layer may be selected from a wide range of insulating resins, and may also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (e.g., polycondensation product of bisphenols and aromatic dicarboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinylpyrrolidone resin, etc. Here, "insulating" means a material having a volume resistivity of 1×1013 This means that the resistance is Ω·cm or more. These binder resins can be used alone or in combination of two or more.

[0222] The compounding ratio of the charge generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass.

[0223] The charge generating layer may contain other known additives.

[0224] The formation of the charge generation layer is not particularly limited, and a known formation method can be used. For example, the charge generation layer can be formed by forming a coating film of a coating liquid for forming the charge generation layer by adding the above components to a solvent, drying the coating film, and heating it as necessary. The charge generation layer can also be formed by vapor deposition of the charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when a fused ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0225] Examples of solvents for preparing the coating liquid for forming the charge generating layer 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, methylene chloride, chloroform, chlorobenzene, toluene, etc. These solvents may be used alone or in combination of two or more.

[0226] Methods for dispersing particles (e.g., charge-generating material) in the coating liquid for forming a charge-generating layer include media-based dispersers such as ball mills, vibration ball mills, attritors, sand mills, and horizontal sand mills, as well as media-less dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion liquid is dispersed by passing through a fine flow path under high pressure. During dispersion, it is effective to adjust the average particle size of the charge-generating material in the coating liquid for forming a charge-generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0227] Examples of methods for applying the coating liquid for forming the charge generating layer onto the undercoat layer (or onto the intermediate layer) include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0228] The thickness of the charge generating layer is preferably set within the range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0229] [Charge transport layer] The charge transport layer is, for example, a layer containing a binder resin and a charge transport material, and may be a layer containing a polymer charge transport material.

[0230] Examples of charge transport materials include electron transport compounds such as quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds. Examples of charge transport materials also include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination, but are not limited to these.

[0231] As the charge transport material, triarylamine derivatives represented by the following structural formula (a-1) and benzidine derivatives represented by the following structural formula (a-2) are preferred from the viewpoint of charge mobility.

[0232] [ka]

[0233] In 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 ) indicates R 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. Examples of the substituents on each of the above groups include halogen atoms, alkyl groups having from 1 to 5 carbon atoms, and alkoxy groups having from 1 to 5 carbon atoms. Examples of the substituents on each of the above groups also include substituted amino groups substituted with alkyl groups having from 1 to 3 carbon atoms.

[0234] [ka]

[0235] In 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 with 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 ) and R T12 , R T13 , R T14 , R T15 and R T16each 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. Examples of the substituents on each of the above groups include halogen atoms, alkyl groups having from 1 to 5 carbon atoms, and alkoxy groups having from 1 to 5 carbon atoms. Examples of the substituents on each of the above groups also include substituted amino groups substituted with alkyl groups having from 1 to 3 carbon atoms.

[0236] Among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), in particular, "-C6H4-CH=CH-CH=C(R T7 )(R T8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 ) is preferred from the viewpoint of charge mobility.

[0237] As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane are used. In particular, polyester polymer charge transport materials are particularly preferred. The polymer charge transport material may be used alone or in combination with a binder resin.

[0238] Examples of binder resins used in the charge transport layer include polycarbonate resins, polyester resins, polyarylate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, and polysilanes. Among these, polycarbonate resins or polyarylate resins are preferred as binder resins. These binder resins may be used alone or in combination of two or more. The compounding ratio of the charge transport material to the binder resin is preferably from 10:1 to 1:5 by mass.

[0239] When the charge transport layer is the outermost layer of the photoreceptor, the charge transport layer contains at least two types of resins. When the charge transport layer is the outermost layer of the photoreceptor, the charge transport layer preferably contains at least one of a polyarylate resin and a polycarbonate resin, and more preferably contains a polyarylate resin and a polycarbonate resin. A combination of a polyarylate resin and a polycarbonate resin is preferred, with both resins having a biphenyl-containing structural unit represented by formula (BP). As the polyarylate resin, a polyarylate resin (PA) is preferred.

[0240] When the charge transport layer is the outermost layer of the photoreceptor, the charge transport layer contains a phenol compound, the preferred forms of which are as described above.

[0241] The charge transport layer may contain other known additives.

[0242] The formation of the charge transport layer is not particularly limited, and a known formation method can be used, for example, by forming a coating film of a coating solution for forming the charge transport layer by adding the above components to a solvent, drying the coating film, and heating it as necessary.

[0243] Examples of solvents for preparing the coating solution for forming the charge transport layer include ordinary organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride; and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents may be used alone or in combination.

[0244] Examples of a coating method for applying the coating liquid for forming the charge transport layer onto the charge generating layer include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0245] The thickness of the charge transport layer is set, for example, preferably in the range of 5 μm to 50 μm, more preferably 10 μm to 30 μm.

[0246] [Single-layer photosensitive layer] The single-layer photosensitive layer (charge generation / charge transport layer) is a layer containing, for example, 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. The content of the charge generating material in the single-layer photosensitive layer is preferably 0.1% by mass to 10% by mass, more preferably 0.8% by mass to 5% by mass, based on the total solid content, and the content of the charge transport material in the single-layer photosensitive layer is preferably 5% by mass to 50% by mass, based on the total solid content. The method for forming the single-layer photosensitive layer is the same as the method for forming the charge generating layer and the charge transport layer. The thickness of the single-layer photosensitive layer is, for example, 5 μm or more and 50 μm or less, and preferably 10 μm or more and 40 μm or less.

[0247] When the single-layer photosensitive layer is the outermost layer of the photoreceptor, the single-layer photosensitive layer contains at least two types of resins. When the single-layer photosensitive layer is the outermost layer of the photoreceptor, the single-layer photosensitive layer preferably contains at least one of a polyarylate resin and a polycarbonate resin, and more preferably contains a polyarylate resin and a polycarbonate resin. A combination of a polyarylate resin and a polycarbonate resin is preferred, where both resins have a biphenyl-containing structural unit represented by formula (BP). As the polyarylate resin, a polyarylate resin (PA) is preferred.

[0248] When the single-layer photosensitive layer is the outermost layer of the photoreceptor, the single-layer photosensitive layer contains a phenol compound, the preferred forms of which are as described above.

[0249] <Image forming apparatus, process cartridge> The image forming apparatus according to the present embodiment includes an electrophotographic photosensitive member, a charging device that charges the surface of the electrophotographic photosensitive member, an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image, a transfer device that transfers the toner image to the surface of a recording medium, and a cleaning device that cleans the surface of the electrophotographic photosensitive member.The electrophotographic photosensitive member according to the present embodiment is used as the electrophotographic photosensitive member.

[0250] In the image forming apparatus according to this embodiment, the cleaning device has a cleaning blade that comes into contact with the outer peripheral surface of the photosensitive member, and cleans the surface of the photosensitive member after the toner image has been transferred and before it is charged by the cleaning blade.

[0251] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as an apparatus equipped with a fixing device that fixes a toner image transferred onto the surface of a recording medium; an apparatus of a direct transfer type that directly transfers a toner image formed on the surface of an electrophotographic photosensitive member onto a recording medium; an apparatus of an intermediate transfer type that primarily transfers a toner image formed on the surface of an electrophotographic photosensitive member onto the surface of an intermediate transfer member, and then secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium; an apparatus equipped with a static elimination device that irradiates the surface of an electrophotographic photosensitive member with static elimination light to eliminate static electricity after the toner image is transferred and before charging; and an apparatus equipped with an electrophotographic photosensitive member heating member that increases the temperature of the electrophotographic photosensitive member and reduces the relative temperature.

[0252] In the case of an intermediate transfer type device, the transfer device is configured to have, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer device that performs primary transfer of the toner image formed on the surface of the electrophotographic photosensitive body onto the surface of the intermediate transfer body, and a secondary transfer device that performs secondarily transfer of the toner image transferred onto the surface of the intermediate transfer body onto the surface of the recording medium.

[0253] The image forming apparatus according to this embodiment may be either a dry development type image forming apparatus or a wet development type image forming apparatus (a development type using a liquid developer).

[0254] In the image forming apparatus according to the present embodiment, for example, a portion including an electrophotographic photosensitive member may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member according to the present embodiment is preferably used. In addition to the electrophotographic photosensitive member, the process cartridge may include, 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.

[0255] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. The main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0256] FIG. 3 is a schematic diagram showing an example of the configuration of an image forming apparatus according to the present embodiment. As shown in FIG. 3 , the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 having an electrophotographic photosensitive member 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 member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photosensitive member 7 through the opening of the process cartridge 300, and the transfer device 40 is disposed at a position facing the electrophotographic photosensitive member 7 via the intermediate transfer member 50, with a portion of the intermediate transfer member 50 being in contact with the electrophotographic photosensitive member 7. Although not shown, the image forming apparatus 100 also includes a secondary transfer device that transfers the toner image transferred onto the intermediate transfer member 50 onto a recording medium (e.g., paper). The intermediate transfer member 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown) correspond to examples of transfer devices.

[0257] 3 integrally supports an electrophotographic photosensitive member 7, a charging device 8 (an example of a charging device), a developing device 11 (an example of a developing device), and a cleaning device 13 (an example of a cleaning device) within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is disposed so as to come into contact with the surface of the electrophotographic photosensitive member 7. The cleaning member may not be in the form of the cleaning blade 131, but may be a conductive or insulating fibrous member, which may be used alone or in combination with the cleaning blade 131.

[0258] FIG. 3 shows an example of an image forming apparatus that includes a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists cleaning, which may be arranged as needed.

[0259] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0260] -Charging device- The charging device 8 may be a contact-type charging device in which the charging member contacts the outer peripheral surface of the photoconductor, or a non-contact-type charging device in which the charging member does not contact the outer peripheral surface of the photoconductor. The effect of the image forming apparatus according to this embodiment (the charging member is less likely to be contaminated over a long period of time) is particularly pronounced in a contact-type charging device.

[0261] The charging device 8 may be a contact-type charging member such as a conductive or semi-conductive charging roller, charging brush, charging film, charging rubber blade, or charging tube. Also usable are non-contact roller chargers, scorotron chargers and corotron chargers that utilize corona discharge, and other known chargers.

[0262] -Exposure equipment- The exposure device 9 may be, for example, an optical system that exposes the surface of the electrophotographic photosensitive member 7 to light such as semiconductor laser light, LED light, or liquid crystal shutter light in a predetermined image. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photosensitive member. The wavelength of semiconductor lasers is mainly near-infrared, with an oscillation wavelength around 780 nm. However, this wavelength is not limited to this, and lasers with an oscillation wavelength in the 600 nm range or blue lasers with an oscillation wavelength of 400 nm to 450 nm may also be used. Furthermore, for color image formation, a surface-emitting laser light source capable of outputting multiple beams is also effective.

[0263] -Developing device- The developing device 11 may be, for example, a general developing device that develops by contact or non-contact application of a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected depending on the purpose. For example, it may be a known developing device that has a function of applying a one-component developer or a two-component developer to the electrophotographic photosensitive member 7 using a brush, roller, or the like. Among these, a developing roller that holds a developer on its surface is preferred.

[0264] The developer used in the developing device 11 may be a one-component developer containing only toner, or a two-component developer containing toner and a carrier. The developer may be magnetic or non-magnetic. Known developers are used.

[0265] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131. In addition to the cleaning blade type, a fur brush cleaning type or a simultaneous development cleaning type may also be used.

[0266] -Transfer device- Examples of the transfer device 40 include a contact type transfer charger using a belt, roller, film, rubber blade, etc., and a known transfer charger such as a scorotron transfer charger or corotron transfer charger that utilizes corona discharge.

[0267] -Intermediate transfer body- A belt-like intermediate transfer belt containing semiconductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. is used as the intermediate transfer body 50. The intermediate transfer body may be in the form of a drum other than a belt.

[0268] FIG. 4 is a schematic diagram showing another example of the configuration of the image forming apparatus according to the present embodiment. The image forming apparatus 120 shown in Fig. 4 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer member 50, and one electrophotographic photosensitive member is used per color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem-type apparatus. [Example]

[0269] Hereinafter, the embodiments of the present invention will be described in detail with reference to examples, but the embodiments of the present invention are not limited to these examples in any way. In the following description, unless otherwise specified, "parts" and "%" are by mass. In the following description, syntheses, treatments, manufacturing, etc. were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0270] <Synthesis of polyarylate resin> Polyarylate resins (PA1) to (PA7) were synthesized. Table 1 shows the units and compositions that make up the polyarylate resin. A2-3 and the like shown in Table 1 are specific examples of the dicarboxylic acid unit (A) already described. B1-2 and the like shown in Table 1 are specific examples of the diol unit (B) already described.

[0271] [Table 1]

[0272] <Photoreceptor manufacturing> The following materials were prepared to form the outermost layer (charge transport layer). ·Charge transport material CTM-1 ·Charge transport material CTM-2

[0273] [ka]

[0274] Polycarbonate resin (PC1), viscosity average molecular weight 50,000 Polycarbonate resin (PC2), viscosity average molecular weight 45,000 Polycarbonate resin (PC3), viscosity average molecular weight 40,000

[0275] [ka]

[0276] Phenolic compound (PH1): ADK STAB AO-30, ADEKA Corporation Phenolic compounds (PH2): ADK STAB AO-50, ADEKA Corporation Phenolic compounds (PH3): ADK STAB AO-80, ADEKA Corporation Phenolic compounds (PH4): SUMILIZER MDP-S, Sumitomo Chemical Co., Ltd.

[0277] [Example 1] - Formation of undercoat layer - 3.5 parts of butyral resin (product name: S-LEC BM-1, Sekisui Chemical Co., Ltd.) and 41 parts of methyl ethyl ketone were mixed and dissolved. 10 parts of a curing agent (blocked isocyanate, product name: Sumidur 3175, Sumitomo Bayer Urethane Co., Ltd.), 45.5 parts of zinc oxide (product name: SMZ-017N, Teika Corporation) surface-treated with a silane coupling agent (product name: KBM603, Shin-Etsu Chemical Co., Ltd.), and 0.27 parts of the following compound were added and stirred, and then dispersed in a sand mill using 1 mm diameter glass beads for 2 hours. Furthermore, 0.01 parts of dioctyltin dilaurate and 2 parts of silicone resin particles (product name: Tospearl 145, GE Toshiba Silicones Co., Ltd.) were added and stirred to obtain a coating solution for forming an undercoat layer. The coating liquid for forming the undercoat layer was applied to the outer peripheral surface of the conductive substrate by dip coating, and dried and cured at 170° C. for 40 minutes to form an undercoat layer having a thickness of 20 μm.

[0278] [ka]

[0279] - Formation of charge generation layer - A mixture consisting of 15 parts of hydroxygallium phthalocyanine (CuKα characteristic X-rays) as a charge-generating material (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, 10 parts of vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using 1 mm diameter glass beads for 4 hours. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion and stirred to obtain a coating solution for forming a charge-generating layer. The coating solution for forming the charge-generating layer was dip-coated onto the undercoat layer and dried at room temperature to form a 0.25 μm thick charge-generating layer.

[0280] - Formation of charge transport layer - ·Charge transport material: CTM-1 ··· 47 parts ·Charge transport material: CTM-2 ··· 20 parts Resin: Polyarylate resin (PA1) 58 parts (60% of total resin) Resin: Polycarbonate resin (PC1) 38 parts (40% of total resin) Phenolic compounds (PH3) 4.9 parts Solvent: tetrahydrofuran 570 parts Solvent: toluene 57 parts The above materials were mixed by stirring to obtain a coating solution for forming a charge transport layer. The coating solution for forming a charge transport layer was dip-coated onto the charge generation layer and dried at 143°C for 30 minutes to form a charge transport layer with a thickness of 33 μm. Photoreceptor 1 was thus obtained.

[0281] [Comparative Example 1] Comparative photoreceptor 1 was obtained in the same manner as in Example 1, except that the specifications of the charge transport layer were changed as shown in Table 2, and the outer peripheral surface was subjected to a polishing treatment.

[0282] [Comparative Example 2, Examples 2 to 12, Examples 14 to 18] Each photoreceptor was manufactured in the same manner as in Example 1, except that the specifications of the charge transport layer were changed as shown in Table 2. The resin ratios shown in Table 2 are the mass ratios relative to the total mass of the polyarylate resin and the polycarbonate resin, and the phenol compound content shown in Table 2 is the mass ratio relative to the mass of the entire charge transport layer.

[0283] [Example 13] Photoreceptor 13 was obtained in the same manner as in Example 1, except that the composition of the charge transport layer was changed as follows. ·Charge transport material: CTM-1 ··· 71 parts Resin: Polyarylate resin (PA1) 28 parts (30% of total resin) Resin: Polycarbonate resin (PC1) 66 parts (70% of total resin) Phenolic compounds (PH3) 2.8 parts Solvent: tetrahydrofuran 570 parts Solvent: toluene 57 parts

[0284] <Performance evaluation> The photoreceptor of each example or comparative example was mounted in an electrophotographic image forming apparatus (models are shown in Table 2; all manufactured by Xerox Corporation). The developing device was filled with a two-component developer (that is, a developer containing toner and carrier). The toner used contained silica particles surface-treated with silicone oil as an external additive. Using the above image forming apparatus, 10,000 black images with a density of 0.5% were printed on A4 plain paper in an environment of 25°C and 50% relative humidity. During this image formation period, the apparatus was stopped once after printing 10 sheets for the performance evaluation described below.

[0285] [RzJIS measurement] The RzJIS of the outer peripheral surface of the photoreceptor was measured before use and after the above-mentioned image formation. The measurement method was as described above. The results are shown in Table 2. The AFM system used for the measurements had a Z-axis resolution of 0.01 nm. If the surface roughness was undetectable, it was recorded as "<0.01" in Table 2.

[0286] [Photoconductor / charging device contamination] After printing 10 sheets and 10,000 sheets of the above image formation, the outer surfaces of the photoconductor and charging device were observed with the naked eye and with a magnifying glass (×25), and the degree of contamination was classified as follows. The results are shown in Table 2.

[0287] 5: No dirt is visible on the photosensitive drum or charging device when viewed with a magnifying glass. 4: A slight streak of dirt is visible on the photosensitive drum with a magnifying glass. No dirt is visible on the charging device with a magnifying glass. 3: Streaky deposits are visible to the naked eye on the photoreceptor. No dirt is visible on the charging device with a magnifying glass. 2: Streaks of adhesion can be seen with the naked eye on the photosensitive drum. Slight streaks of adhesion can be seen on the charging device with a magnifying glass. This is not a problem in monochrome printing, but is at a level that becomes a problem in color printing. 1: Streaks of adhesion are visible to the naked eye on the photoconductor. Streaks of adhesion are visible to the naked eye on the charging device. This is a level that can cause problems even in monochrome printing.

[0288] [Blade whine] Blade noise (noise caused by the vibration of the photoreceptor cleaning blade) is likely to occur when the rotating photoreceptor stops. During the above image formation, the presence or absence of blade noise was checked by ear near the image forming device during the period when the device was stopped after outputting 10 sheets, and during the period just before the device was stopped after outputting 10,000 sheets, and the results were classified as follows. Table 2 shows the results.

[0289] 5: I can't hear you. 4: A slight noise can be heard when the unit is stopped. Not audible in the office. 3: A slight noise can be heard when the unit is stopped. Slightly audible in an office. 2: A slight sound can be heard when outputting. 1: Sound can be heard from the output.

[0290] [Scratches on the outer surface of the photoconductor] After printing 10,000 sheets of the image formed as described above, the outer peripheral surface of the photoreceptor was observed with the naked eye and with a magnifying glass (×25), and the presence or absence of scratches was classified as follows. The results are shown in Table 2.

[0291] 5: No scratches visible with a magnifying glass. 4: Faint lines can be seen with a magnifying glass. 3: Lines are clearly visible with a magnifying glass. 2: Faint lines are visible to the naked eye. 1: Lines are clearly visible to the naked eye.

[0292] [Oxidative deterioration of photoreceptor] After printing 10,000 sheets of the above image formation, 1,000 black images with an image density of 0.5% were printed on A4 plain paper in an environment with a temperature of 29°C and a relative humidity of 90%. The image forming apparatus was then left in the same environment for two days. Next, in the same environment, 100 black images with an image density of 5% were printed on A4 plain paper. The 100 images were observed with the naked eye and with a magnifying glass (x25) and classified as follows. The results are shown in Table 2. This series of image formation processes mimics office use with a two-day work week. While the office's air conditioning is turned off, the image forming device is placed in a high-temperature, high-humidity environment. If the outer surface of the photoconductor oxidizes and deteriorates during this time, image defects will occur when the image forming device is restarted after the break.

[0293] 5: No image defects are observed. 4: A faint image defect can be seen with a magnifying glass on the first image. No image defects can be seen on the second and subsequent images. 3: The first image has a faint image defect that can be seen with the naked eye. The second to fifth images have no image defect, even when viewed with a magnifying glass. 2: Image defects are visible to the naked eye on the 1st to 10th images. Image defects are no longer visible even with a magnifying glass on the 11th to 100th images. 1: Image defects are visible to the naked eye on sheets 1 to 100.

[0294] The resin ratios shown in Table 2 are mass ratios relative to the total mass of the polyarylate resin and polycarbonate resin. The phenol compound content shown in Table 2 is mass ratios relative to the total mass of the charge transport layer (i.e., total solid content).

[0295] [Table 2]

[0296] The electrophotographic photoreceptor, process cartridge, and image forming apparatus of the present disclosure include the following aspects: Each formula is the same as the formula with the same number described above.

[0297] (Addendum) (((1))) A conductive substrate and a photosensitive layer disposed on the conductive substrate, the outermost layer contains a charge transport material, two or more types of resin, and a phenol compound; The RzJIS of the outer surface is 0.1 nm or more and 100 nm or less. Electrophotographic photoreceptor. (((2))) The electrophotographic photoreceptor according to (((1))), wherein the RzJIS of the outer peripheral surface is 0.5 nm or more and 50 nm or less. (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), wherein the phenol compound includes a hindered phenol compound. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the two or more types of resins include at least one of a polyarylate resin and a polycarbonate resin. (((5))) The electrophotographic photoreceptor according to any one of (((1))) to (((4))), wherein the two or more types of resins include a polyarylate resin having a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B). (((6))) The electrophotographic photoreceptor according to (((5))), wherein the dicarboxylic acid unit represented by formula (A) comprises at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by formula (A1), a dicarboxylic acid unit (A2) represented by formula (A2), a dicarboxylic acid unit (A3) represented by formula (A3), a dicarboxylic acid unit (A4) represented by formula (A4), and a dicarboxylic acid unit (A5) represented by formula (A5). (((7))) The electrophotographic photoreceptor according to (((5))) or (((6))), wherein the diol unit represented by formula (B) comprises at least one selected from the group consisting of a diol unit (B1) represented by formula (B1), a diol unit (B2) represented by formula (B2), a diol unit (B3) represented by formula (B3), a diol unit (B4) represented by formula (B4), a diol unit (B5) represented by formula (B5), a diol unit (B6) represented by formula (B6), a diol unit (B7) represented by formula (B7), and a diol unit (B8) represented by formula (B8). (((8))) The electrophotographic photoreceptor according to any one of (((1))) to (((7))), wherein the outermost layer contains a polyarylate resin and a polycarbonate resin. (((9))) The electrophotographic photoreceptor according to (((8))), wherein the polyarylate resin and the polycarbonate resin each have a structural unit containing biphenyl represented by formula (BP). (((10))) The electrophotographic photoreceptor according to (((8))) or (((9))), wherein the proportion of the polyarylate resin in the total amount of the polyarylate resin and the polycarbonate resin contained in the outermost layer is 25% by mass or more and 75% by mass or less. (((11))) The electrophotographic photoreceptor according to any one of (((1))) to (((10))), wherein the photosensitive layer has a charge generating layer and a charge transporting layer, and the charge transporting layer is the outermost layer. (((12))) An electrophotographic photoreceptor according to any one of (((1))) to (((11))), Attaching to and detaching from the image forming device Process cartridge. (((13))) an electrophotographic photoreceptor according to any one of (((1))) to (((11))); a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; a cleaning device having a cleaning blade that comes into contact with the surface of the electrophotographic photosensitive member and that cleans the surface of the electrophotographic photosensitive member, Image forming device.

[0298] According to (((1))), (((3))), (((4))), (((5))), (((6))), (((7))) or (((11))), an electrophotographic photoreceptor is provided which is less likely to contaminate the charging member and less likely to generate abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor having an RzJIS of the outer peripheral surface of less than 0.1 nm or more than 100 nm. According to (((2))), an electrophotographic photoreceptor is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor having an RzJIS of less than 0.5 nm or more than 50 nm on the outer peripheral surface. According to (((8))), an electrophotographic photoreceptor is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to a configuration in which the outermost surface layer contains only one of a polyarylate resin and a polycarbonate resin. According to (((9))), an electrophotographic photoreceptor is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to a configuration in which at least one of the polyarylate resin and the polycarbonate resin does not have a structural unit containing biphenyl represented by formula (BP). According to (((10))), an electrophotographic photoreceptor is provided which is less likely to contaminate the charging member and less likely to generate abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor in which the proportion of polyarylate resin in the total amount of polyarylate resin and polycarbonate resin contained in the outermost surface layer is less than 25 mass % or more than 75 mass %. According to (((12))), a process cartridge is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photosensitive member cleaning blade over a long period of time, compared to a process cartridge in which the RzJIS of the outer peripheral surface of the electrophotographic photosensitive member is less than 0.1 nm or more than 100 nm. According to (((13))), an image forming apparatus is provided which is less likely to cause contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, compared to an image forming apparatus in which the RzJIS of the outer peripheral surface of the electrophotographic photoreceptor is less than 0.1 nm or more than 100 nm. [Explanation of symbols]

[0299] 1 Conductive substrate, 2 Undercoat layer, 3 Charge generation layer, 4 Charge transport layer, 5 Photosensitive layer, 10A photoreceptor, 10B photoreceptor

[0300] 7 electrophotographic photosensitive member, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 40 transfer device, 50 intermediate transfer body, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll-shaped), 133 fibrous member (flat brush-shaped), 300 process cartridge

Claims

1. A conductive substrate and a photosensitive layer disposed on the conductive substrate, the outermost layer contains a charge transport material, two or more types of resin, and a phenol compound; The RzJIS of the outer surface is 0.1 nm or more and 100 nm or less. Electrophotographic photoreceptor.

2. 2. The electrophotographic photoreceptor according to claim 1, wherein the RzJIS of the outer peripheral surface is 0.5 nm or more and 50 nm or less.

3. 2. The electrophotographic photoreceptor according to claim 1, wherein the phenol compound comprises a hindered phenol compound.

4. 2. The electrophotographic photoreceptor according to claim 1, wherein the two or more types of resins include at least one of a polyarylate resin and a polycarbonate resin.

5. 2. The electrophotographic photoreceptor according to claim 1, wherein the two or more resins include a polyarylate resin having a dicarboxylic acid unit represented by the following formula (A) and a diol unit represented by the following formula (B): 【Chemistry 1】 In formula (A), Ar Ａ１ and Ar Ａ２ each independently represents an aromatic ring which may have a substituent, and L Ａ is a single bond or a divalent linking group, n Ａ１ is 0, 1 or 2. In formula (B), Ar Ｂ１ and Ar Ｂ２ each independently represents an aromatic ring which may have a substituent, and L Ｂ is a single bond, an oxygen atom, a sulfur atom, or -C(Rb １ )(Rb ２ )- and n Ｂ１ is 0, 1 or 2. １ and Rb ２ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb １ and Rb ２ may be bonded to form a cyclic alkyl group.

6. 6. The electrophotographic photoreceptor according to claim 5, wherein the dicarboxylic acid unit represented by formula (A) comprises at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by formula (A1), a dicarboxylic acid unit (A2) represented by formula (A2), a dicarboxylic acid unit (A3) represented by formula (A3), a dicarboxylic acid unit (A4) represented by formula (A4), and a dicarboxylic acid unit (A5) represented by formula (A5): 【Chemistry 2】 In formula (A1), n １０１ is an integer of 0 to 4, １０１ Ra １０１ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A2), n ２０１ and n ２０２ are each independently an integer of 0 to 4, ２０１ Ra ２０１ and n ２０２ Ra ２０２ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A3), n ３０１ and n ３０２ are each independently an integer of 0 to 4, ３０１ Ra ３０１ and n ３０２ Ra ３０２ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A4), n ４０１ is an integer of 0 to 6, ４０１ Ra ４０１ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A5), n ５０１ , n ５０２ and n ５０３ are each independently an integer of 0 to 4, ５０１ Ra ５０１ , n ５０２ Ra ５０２ and n ５０３ Ra ５０３ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

7. 6. The electrophotographic photoreceptor according to claim 5, wherein the diol unit represented by formula (B) comprises at least one selected from the group consisting of a diol unit (B1) represented by formula (B1), a diol unit (B2) represented by formula (B2), a diol unit (B3) represented by formula (B3), a diol unit (B4) represented by formula (B4), a diol unit (B5) represented by formula (B5), a diol unit (B6) represented by formula (B6), a diol unit (B7) represented by formula (B7), and a diol unit (B8) represented by formula (B8). 【Transformation 3】 【Chemistry 4】 In formula (B1), Rb １０１ is a branched alkyl group having 4 to 20 carbon atoms, and Rb ２０１ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０１ , Rb ５０１ , Rb ８０１ and Rb ９０１ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B2), Rb １０２ is a linear alkyl group having 4 to 20 carbon atoms, and Rb ２０２ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０２ , Rb ５０２ , Rb ８０２ and Rb ９０２ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B3), Rb １１３ and Rb ２１３ are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; d is an integer of 7 to 15; Rb ４０３ , Rb ５０３ , Rb ８０３ and Rb ９０３ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B4), Rb １０４ and Rb ２０４ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０４ , Rb ５０４ , Rb ８０４ and Rb ９０４ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B5), Ar １０５ is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb ２０５ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０５ , Rb ５０５ , Rb ８０５ and Rb ９０５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B6), Rb １１６ and Rb ２１６ are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; e is an integer of 4 to 6; Rb ４０６ , Rb ５０６ , Rb ８０６ and Rb ９０６ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B7), Rb ４０７ , Rb ５０７ , Rb ８０７ and Rb ９０７ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B8), Rb ４０８ , Rb ５０８ , Rb ８０８ and Rb ９０８ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

8. 2. The electrophotographic photoreceptor according to claim 1, wherein the outermost layer contains a polyarylate resin and a polycarbonate resin.

9. 9. The electrophotographic photoreceptor according to claim 8, wherein the polyarylate resin and the polycarbonate resin each have a structural unit containing biphenyl represented by the following formula (BP): 【Transformation 5】 In formula (BP), j is an integer of 0 to 4, and j R １ are each independently a methyl group or an ethyl group, k is an integer of 0 to 4, and k R ２ are each independently a methyl group or an ethyl group.

10. 9. The electrophotographic photoreceptor according to claim 8, wherein the proportion of the polyarylate resin in the total amount of the polyarylate resin and the polycarbonate resin contained in the outermost layer is 25% by mass or more and 75% by mass or less.

11. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a charge generating layer and a charge transporting layer, and the charge transporting layer is the outermost layer.

12. An electrophotographic photoreceptor according to any one of claims 1 to 11, Attaching to and detaching from the image forming device Process cartridge.

13. The electrophotographic photoreceptor according to any one of claims 1 to 11, a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; a cleaning device having a cleaning blade that comes into contact with the surface of the electrophotographic photosensitive member and that cleans the surface of the electrophotographic photosensitive member, Image forming device.

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