Electrophotographic photoreceptor, process cartridge and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor which is less susceptible to contamination of a charging member and generation of abnormal noise due to vibration of a photoreceptor cleaning blade over a long period of time. [Solution] The electroconductive electroconductive layer comprises 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, and the RzJIS of the outer peripheral surface is 0.1 nm or more and 100 nm or less.

Description

[Technical field]

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

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

[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 surfaces. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2007-108420 A [Patent Document 2] JP 2003-43709 A [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 susceptible to contamination of a charging member and abnormal noise caused by vibration of a photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor having an outer peripheral surface RzJIS of less than 0.1 nm or more than 100 nm. [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> 13. The electrophotographic photoreceptor according to claim 12, <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> 13. The electrophotographic photoreceptor according to claim 12, <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> 13. The electrophotographic photoreceptor according to claim 12, <9> The polyarylate resin and the polycarbonate resin each have a biphenyl-containing structural unit 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> 13. The electrophotographic photoreceptor according to claim 12, <12> <1> ~ <11> The electrophotographic photoreceptor according to any one of the above items is provided, Attaching to and detaching from an image forming apparatus; Process cartridge. <13> <1> ~ <11> and an electrophotographic photoreceptor according to any one of the above items. a charging device for charging a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring 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 photoreceptor and that cleans the surface of the electrophotographic photoreceptor; Image forming device. Effect of the Invention

[0009] <1> , <3> , <4> , <5> , <6> , <7> or <11> According to this, an electrophotographic photoreceptor is provided which is less susceptible to contamination of the charging member and abnormal noise caused by vibration of the photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor having an outer peripheral surface RzJIS of less than 0.1 nm or more than 100 nm. <2> According to the present invention, an electrophotographic photoreceptor is provided which is less susceptible to contamination of the charging member and abnormal noise caused by vibration of the photoreceptor cleaning blade over a long period of time, compared to an electrophotographic photoreceptor having an outer peripheral surface RzJIS of less than 0.5 nm or more than 50 nm. <8> According to the present invention, an electrophotographic photoreceptor is provided which is less susceptible to contamination of the charging member and abnormal noise caused by vibration of the photoreceptor cleaning blade over a long period of time, as compared with a configuration in which the outermost 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 the formula (BP). <10> According to the present invention, an electrophotographic photoreceptor is provided which is less susceptible to contamination of the charging member and abnormal noise caused by 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 layer is less than 25 mass % or more than 75 mass %. <12> According to this, a process cartridge is provided which is less susceptible to contamination of the charging member and abnormal noise caused by vibration of the photoreceptor 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 photoreceptor is less than 0.1 nm or exceeds 100 nm. <13> According to this, an image forming apparatus is provided in which contamination of the charging member and abnormal noise caused by vibration of the photoreceptor cleaning blade are less likely to occur 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. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a partial cross-sectional view showing an example of a layer structure of the electrophotographic photoreceptor according to the first embodiment. [Diagram 2] FIG. 11 is a partial cross-sectional view showing an example of a layer structure of an electrophotographic photoreceptor according to a second embodiment. [Diagram 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. 2 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples are merely illustrative of the embodiments, and are not intended to limit the scope of the embodiments.

[0012] In the present disclosure, a numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present disclosure in stages, 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. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the 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, it may be only B, or it may be 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 an embodiment of the present disclosure is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the size of the members in each drawing is conceptual, and the relative relationship between the sizes of the members is not limited to this.

[0016] In the present disclosure, each component may contain multiple types of 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 particles corresponding to each component may include multiple types. 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, unless otherwise specified, the alkyl group and the alkylene group include any of straight-chain, branched, and cyclic groups. In the present disclosure, a hydrogen atom in an organic group, an aromatic ring, a linking group, an alkyl group, an alkylene group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, and the like may be substituted with a halogen atom.

[0018] In the present disclosure, when a compound is shown 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 is synonymous with 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 showing an example of the layer structure of the photoreceptor according to the present embodiment. The photoreceptor 10A shown in Fig. 1 has a laminated photosensitive layer. The 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). The 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 that shows a schematic example of another example of the layer structure of the photoreceptor according to the present embodiment. The photoreceptor 10B shown in Fig. 2 has a single-layer type 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 the present embodiment has an outermost layer containing a charge transport material, two or more types of resin, and a phenol compound, and has an RzJIS of 0.1 nm to 100 nm on the outer peripheral surface. 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 constitutes the outer peripheral surface. Another example of an embodiment of the photoreceptor has a single-layer type photosensitive layer, the single-layer type photosensitive layer being the outermost layer and constituting the outer circumferential 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 a static electricity removal treatment, which 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 measurement conditions listed below to obtain three-dimensional data of the surface shape. Atomic force microscope: AFM5200S, Hitachi High-Tech Corporation Cantilever: SI-DF40, Hitachi High-Tech Fielding Co., Ltd. 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 the present embodiment has an outermost surface layer containing a charge transport material, two or more types of resin, and a phenolic compound, and has 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") to occur over a long period of time. The mechanism behind this is assumed to be as follows.

[0027] Conventionally, in order to reduce the friction coefficient of the outer peripheral surface of a photoreceptor, fluororesin particles have been incorporated into the outermost layer of the photoreceptor. However, since there is a high possibility that restrictions on the manufacture and use of organic fluorine compounds will become stricter in the future, there is a demand for a technology to replace the internal addition of fluororesin particles. Another method for lowering the coefficient of friction of the outer peripheral surface of the photoreceptor is to polish the outer peripheral surface of the photoreceptor to form minute irregularities, but the irregularities formed by polishing wear away with use of the photoreceptor, so the coefficient of friction of the outer peripheral surface of the photoreceptor gradually increases. In contrast, the photoreceptor according to this embodiment has a surface layer containing two or more resins and a phenolic compound, thereby lowering the coefficient of friction of the outer circumferential surface. When the surface layer is formed, the phenolic compound promotes phase separation of two or more resins, and a fine phase separation structure of nano-order is formed in the surface layer. This fine phase separation structure forms fine irregularities on the outer circumferential surface of the photoreceptor, and the coefficient of friction can be kept low. In addition, since a fine phase separation structure also exists inside the surface layer, even if the surface layer is worn with use of the photoreceptor, new fine irregularities appear on the outer circumferential surface, and the coefficient of friction can be kept low. In addition, the lubricating components contained in the toner (for example, higher fatty acid metal salts as external additives, hydrophobic treatment agents (for example, silicone oil) that were present on the surface of the external additive particles, etc.) enter the fine irregularities on the outer circumferential surface of the photoreceptor, and the coefficient of friction can be kept low. Since the photoconductor according to the present embodiment can maintain a low coefficient of friction, the cleaning performance of the outer peripheral surface of the photoconductor with a cleaning blade is good for a long period of time. As a result, contamination of the charging member and blade noise of the photoconductor cleaning blade are unlikely to occur for a long period of time. Contamination of the charging member is likely to occur in charging members that come into contact with the outer peripheral surface of the photoreceptor, but can also occur in charging members that do not come into contact with the outer peripheral surface of the photoreceptor because 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 is too smooth and has a high friction coefficient. It is also presumed that if the RzJIS of the outer peripheral surface is less than 0.1 nm, the lubricating components contained in the toner cannot be sufficiently retained. From the viewpoint of suppressing the friction coefficient, 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 is too large and the friction coefficient is high. From the viewpoint of suppressing the friction coefficient, 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 types of resin 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 types of resin 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 layer may be the same compound as the charge transport material contained in the charge transport layer described below, and the preferred compounds are also the same.

[0032] Examples of the resin contained in the outermost 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 from the viewpoint of the abrasion resistance of the outermost layer, and more preferably contains a polyarylate resin and a polycarbonate resin. The embodiment containing a polyarylate resin and a polycarbonate resin is also preferable from the viewpoint of forming a fine phase separation 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 resin, resin molecules are bound by intermolecular forces due to stacking of aromatic rings, improving the wear resistance of the outermost layer. As the polyarylate resin, a polycondensation product of bisphenols and aromatic dicarboxylic acids is preferable. As a preferable example of the polyarylate resin, there is polyarylate resin (PA) described later.

[0036] As the polycarbonate resin, a polycarbonate resin having a continuous structural unit having an aromatic ring is preferable. In the polycarbonate resin, the resin molecules are bound to each other by intermolecular forces due to stacking of the 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] As a combination of a polyarylate resin and a polycarbonate resin, a combination of resins both having a biphenyl-containing structural unit represented by the following formula (BP) is preferable.

[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 whole or a part of the structure obtained by removing an ester bond (-C(=O)O-) or a carbonate bond (-OC(=O)O-) from a structural unit containing the biphenyl represented by formula (BP). In other words, the right end and the left end of the biphenyl represented by formula (BP) may be directly bonded 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, further 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. The phenol compound may be used alone or in combination of two or more kinds.

[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 hydroxyl 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: e.g., 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 Alkylidene bisphenol 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 kinds.

[0051] The content of the phenol compound contained in the outermost layer is preferably 0.1 mass % or more and 20 mass % or less, more preferably 0.5 mass % or more and 10 mass % or less, and even more preferably 1 mass % or more and 5 mass % or less, 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 regulations on the production and use of organic fluorine compounds will become stronger in the future, the content of the fluororesin particles is preferably in 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 from 5 μm to 50 μm, more preferably from 8 μm to 40 μm, and further preferably from 10 μm to 30 μm. When the single-layer type photosensitive layer is the outermost layer, the thickness of the outermost layer is preferably from 5 μm to 50 μm, more preferably from 8 μm to 45 μm, and even more preferably from 10 μm to 40 μm.

[0054] The method for forming the outermost layer is the same as the method for forming the charge transport layer and the method for forming the single-layer type 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 a 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; L A is a single bond or a divalent linking group, 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, and the benzene ring and the naphthalene ring are preferred.

[0060] Ar A1 The hydrogen atoms on the aromatic ring of 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, and the benzene ring and the naphthalene ring are preferred.

[0062] Ar A2 The hydrogen atoms on the aromatic ring of 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 of 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 the dicarboxylic acid unit (A1) represented by the following formula (A1), the dicarboxylic acid unit (A2) represented by the formula (A2), the dicarboxylic acid unit (A3) represented by the formula (A3), the dicarboxylic acid unit (A4) represented by the formula (A4), and the 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 each independently represents 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 each independently represents 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 each independently represents 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 each independently represents 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 each independently represents 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 are the same, hereinafter, Ra 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 related to Ra may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 or 2. 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 the branched alkyl group 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 group formed by linking these monocyclic alkyl groups.

[0080] The aryl group having 6 to 12 carbon atoms related to Ra may be either a monocyclic or polycyclic ring. The number of carbon atoms of 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 related to 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 the branched alkoxy group 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 the following 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 the following 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 the 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 the following 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 the following 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 unit (A) contained in the polyarylate resin (PA) may be of one type or of two or more types.

[0094] The mass proportion of the dicarboxylic acid unit (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 unit (A) is 15 mass% or more, the outermost layer has good abrasion resistance. From this viewpoint, the mass proportion of the dicarboxylic acid unit (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 further preferably 50 mass% or less.

[0095] The polyarylate resin (PA) may contain other dicarboxylic acid units other than the dicarboxylic acid units (A). Examples of other dicarboxylic acid units include aliphatic dicarboxylic acid (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) units, alicyclic dicarboxylic acid (e.g., cyclohexanedicarboxylic acid) units, 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 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; 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 each independently represents 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; 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, and the benzene ring and the naphthalene ring are preferred.

[0100] Ar B1 The hydrogen atoms on the aromatic ring of 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, and the benzene ring and the naphthalene ring are preferred.

[0102] Ar B2The hydrogen atoms on the aromatic ring of 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 of 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 following formula (B2), a diol unit (B4) represented by the following formula (B4), a diol unit (B5) represented by the following formula (B5), and a diol unit (B6) represented by the following formula (B6): It is more preferable that the diol unit (B1) represented by the following formula (B1), the diol unit (B2) represented by the following formula (B2), the diol unit (B5) represented by the following formula (B5), and the diol unit (B6) represented by the following formula (B6) are contained in the diol unit (B1), It is even more preferable that the diol unit (B1) represented by the following formula (B1), the diol unit (B2) represented by the following formula (B2), and the diol unit (B6) represented by the following formula (B6) are contained in the diol unit (B1), 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 each independently represents 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 carbon number of 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 each independently represents 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 aryl 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 each independently represents 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 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 1 to 4 carbon atoms is preferably 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 each independently represents 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 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 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, 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 each independently represents 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 of 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 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. Examples of the aralkyl group 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 anthrathylmethyl 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 each independently represents 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 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 1 to 4 carbon atoms is preferably 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 each independently represents 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 each independently represents 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 forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 201 , Rb 202 , Rb 204 and Rb 205 "Rb 200 " is collectively described as such.

[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 has 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 forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 401 , Rb 402 , Rb 403 , Rb 404 , Rb 405 , Rb 406 , Rb 407 and Rb 408 "Rb 400 " is collectively described as such.

[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 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 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 the branched alkoxy group 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 forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 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 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 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 the branched alkoxy group 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 forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 801 , Rb 802 , Rb 803 , Rb 804 , Rb 805 , Rb 806 , Rb 807 and Rb 808 "Rb 800 " is collectively described as such.

[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 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 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 the branched alkoxy group 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 forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 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 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 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 the branched alkoxy group 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 the 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 the 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 the 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 the 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 the 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 of 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 unit (B) is 25 mass% or more, peeling of the outermost surface layer can be suppressed. From this viewpoint, the mass proportion of the diol unit (B) is more preferably 30 mass% or more, and further preferably 35 mass% or more. When the mass proportion of the diol unit (B) is 80 mass% or less, the solubility in the coating liquid for forming the outermost layer can be maintained and the abrasion resistance can be improved. From this viewpoint, the mass proportion of the diol unit (B) is more preferably 75 mass% or less, and further preferably 70 mass% or less.

[0166] The polyarylate resin (PA) may contain other diol units other than the diol units (B). Examples of the 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 capped or modified with a terminal capping agent or a molecular weight regulator used during production. Examples of the terminal capping agent or the molecular weight regulator include a monohydric phenol, a monovalent acid chloride, a monohydric alcohol, and a monovalent carboxylic acid. 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 -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 of these. 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 monovalent carboxylic 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 from 30,000 to 300,000, more preferably from 40,000 to 250,000, and even more preferably from 50,000 to 200,000. 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] The polyarylate resin (PA) can be obtained by polycondensing a monomer that gives a dicarboxylic acid unit (A) and a monomer that gives a diol unit (B) with other monomers as required by a conventional method. Examples of the method of polycondensing a monomer include an interfacial polymerization method, a solution polymerization method, and a melt polymerization method. The interfacial polymerization method is a polymerization method for obtaining a polyester by mixing a dicarboxylic acid halide dissolved in an organic solvent that is not compatible with water with a dihydric alcohol dissolved in an alkaline aqueous solution. Examples of literature related to the interfacial polymerization method include WME ARECSON, J. Poly. Sci., XL399, 1959, and JP-B-1959. The interfacial polymerization method has a faster reaction rate than the solution polymerization method, so that the hydrolysis of the dicarboxylic acid halide can be suppressed, and as a result, a polyarylate resin (PA) with a high molecular weight can be obtained.

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

[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.). 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 in order to suppress interference fringes that occur when irradiating with laser light. When non-interfering 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 since it suppresses the occurrence of defects due to unevenness on the surface.

[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, in which the conductive substrate is pressed against a rotating grindstone and continuously ground; and anodizing.

[0174] As a method for roughening the surface, there can be mentioned a method in which, without roughening the surface of the conductive substrate, a 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] In the roughening treatment by anodization, an oxide film is formed on the surface of a conductive substrate made of metal (e.g., aluminum) by anodizing the substrate in an electrolyte solution using the substrate as the anode. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodization is chemically active in its original state, easily contaminated, and has a large resistance variation 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 filled by volume expansion caused by hydration reaction in pressurized steam or boiling water (metal salts such as nickel may be added) to change 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. If the thickness is within this range, the film tends to exhibit a barrier property against injection and 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 acid treatment liquid is carried out, for example, as follows. First, an acid treatment liquid containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The compounding ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acid treatment liquid 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, and the total concentration of these acids is 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 material in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting the material with heated steam at 90°C to 120°C for 5 to 60 minutes. The thickness of the coating is preferably 0.1 μm to 5 μm. This may be further anodized using an electrolyte solution having low coating solubility, such as adipic acid, boric acid, borates, phosphates, phthalates, maleates, benzoates, tartrates, or citrates.

[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, examples of inorganic particles having the above-mentioned resistance value include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, and zinc oxide particles are particularly preferred.

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

[0182] The content of the inorganic particles is, for example, preferably from 10% by mass to 80% by mass, more preferably from 40% by mass to 80% by mass, based on the binder resin.

[0183] The inorganic particles may be surface-treated. 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 coupling agent, an aluminum 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] Silane coupling agents may be used in combination of two or more kinds. 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 based on 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 viewpoints of improving the long-term stability of electrical properties and carrier blocking properties.

[0190] Examples of the electron-accepting compound 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. Examples of the compound having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds, and more specifically, anthraquinone, alizarin, quinizarin, anthraphin, purpurin, and derivatives 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 method for attaching the electron accepting compound to the surface of the inorganic particles may be, for example, a dry method or a wet method.

[0193] The dry method is, for example, a method in which an electron-accepting compound is attached to the surface of inorganic particles by dropping an electron-accepting compound directly or dissolved in an organic solvent or spraying it together with dry air or nitrogen gas while stirring inorganic particles with a mixer or the like that exerts a large shearing force. When dropping or spraying the electron-accepting compound, it is preferable to do so at a temperature below the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be performed at 100°C or higher. The temperature and time of baking are not particularly limited as long as electrophotographic properties can be obtained.

[0194] The wet method is a method in which, for example, an electron-accepting compound is added while dispersing inorganic particles in a solvent using a stirrer, ultrasonic disperser, sand mill, attritor, ball mill, etc., and the solvent is removed after stirring or dispersing, so that the electron-accepting compound adheres to the surface of the inorganic particles. The solvent is removed, for example, by filtration or distillation. After the solvent is removed, 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, and examples of such methods include a method of removing the moisture while stirring and heating in a solvent, and a method of removing the moisture by azeotropy with the solvent.

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

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

[0197] Examples of the binder resin used in the undercoat layer include known materials 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, phenol 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 the binder resin used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline, etc.), 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, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy 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 for improving electrical properties, environmental stability, and image quality. Examples of the additives include known materials such as polycyclic condensation and azo-based electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, silane coupling agents, etc. As described above, silane coupling agents are used for surface treatment of inorganic particles, 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, 3-chloropropyltrimethoxysilane, and the like.

[0201] Examples of the zirconium chelate compound 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-n-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 polycondensation product 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 in order to suppress moire images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of the 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 the polishing method include buffing, sandblasting, wet honing, grinding, and the like.

[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 solution for forming the undercoat layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary.

[0207] Examples of the solvent 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 the method for dispersing the inorganic particles when preparing the coating liquid for forming the undercoat layer include known methods such as those 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 the method for applying the coating liquid for forming the undercoat layer onto the conductive substrate include ordinary 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, and more preferably within 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 (e.g., polyvinyl butyral, etc.), 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 solution for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it as 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. The intermediate layer may 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. The charge generation layer may also be a vapor deposition layer of the charge generation material. The vapor deposition layer of the charge generation material is suitable for use with a non-coherent 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; condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0217] Among these, in order to accommodate 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 condensed 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 using an incoherent light source such as an LED or an organic EL image array having an emission center wavelength of 450 nm or more and 780 nm or less.

[0220] In contrast, when n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge generating materials, dark current is unlikely to occur, and image defects called black spots can be suppressed even in thin films. The n-type is determined by the polarity of the flowing photocurrent using the commonly used time-of-flight method, and those that are more likely to pass electrons as carriers than holes are considered to be 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, polysilane, and the like. Examples of binder resins include polyvinyl butyral resins, polyarylate resins (polycondensates of bisphenols and aromatic dicarboxylic acids, etc.), polycarbonate resins, polyester resins, phenoxy resins, vinyl chloride-vinyl acetate copolymers, polyamide resins, acrylic resins, polyacrylamide resins, polyvinylpyridine resins, cellulose resins, urethane resins, epoxy resins, casein, polyvinyl alcohol resins, polyvinylpyrrolidone resins, etc. Here, "insulating" refers to a material having a volume resistivity of 1×1013 This means that the resistance is Ω·cm or more. These binder resins are 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 a 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 is used, for example, by forming a coating film of a coating solution for forming the charge generation layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary. The formation of the charge generation layer may be performed by vapor deposition of the charge generation material. The formation of the charge generation layer by vapor deposition is particularly suitable when a condensed ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0225] Examples of the solvent 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] As a method for dispersing particles (e.g., charge generating material) in the coating liquid for forming a charge generating layer, for example, a media dispersing machine such as a ball mill, a vibration ball mill, an attritor, a sand mill, or a horizontal sand mill, or a media-less dispersing machine such as a stirrer, an ultrasonic dispersing machine, a roll mill, or a high-pressure homogenizer, is used. Examples of the high-pressure homogenizer 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 is dispersed by penetrating a fine flow path under high pressure. During dispersion, it is effective to set 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 a method 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 or more and 5.0 μm or less, and more preferably 0.2 μm or more and 2.0 μm or less.

[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 the charge transport material include electron transporting 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 the charge transport material include hole transporting 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, from the viewpoint of charge mobility, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2) are preferable.

[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 -CH-CH=CH-CH=C(R T7 )(R T8 ) is shown. 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 substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group 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 from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, an amino group substituted with an alkyl group having from 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 substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group 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 preferable 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 the binder resin used in the charge transport layer include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polysilane, etc. Among these, polycarbonate resin or polyarylate resin is suitable as the binder resin. These binder resins are 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 kinds 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. As a combination of a polyarylate resin and a polycarbonate resin, a combination of resins both having a biphenyl-containing structural unit represented by the formula (BP) is preferable. As the polyarylate resin, a polyarylate resin (PA) is preferable.

[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, the charge transport layer can be formed by forming a coating film of a coating solution for forming the charge transport layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary.

[0243] Examples of solvents for preparing the coating liquid 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 of two or more.

[0244] Examples of a coating method for coating the coating liquid for forming the charge transport layer on the charge generating layer include ordinary 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 or more and 50 μm or less, and more preferably in the range of 10 μm or more and 30 μm or less.

[0246] [Single-layer photosensitive layer] The single-layer type photosensitive layer (charge generation / charge transport layer) is, for example, a layer containing a charge generation material, a charge transport material, and, if necessary, a binder resin and other known additives. These materials are the same as those described for the charge generation layer and the charge transport layer. 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. 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 type 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, from 5 μm to 50 μm, and preferably from 10 μm to 40 μm.

[0247] When the single-layer photosensitive layer is the outermost layer of the photoreceptor, the single-layer photosensitive layer contains at least two kinds 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. As a combination of a polyarylate resin and a polycarbonate resin, a combination of resins both having a biphenyl-containing structural unit represented by the formula (BP) is preferable. As the polyarylate resin, a polyarylate resin (PA) is preferable.

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

[0249] <Image forming apparatus, process cartridge> The image forming apparatus according to the present embodiment includes an electrophotographic photoreceptor, a charging device for charging the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, a transfer device for transferring the toner image to the surface of a recording medium, and a cleaning device for cleaning the surface of the electrophotographic photoreceptor.The electrophotographic photoreceptor according to the present embodiment is applied as the electrophotographic photoreceptor.

[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 photoconductor, and cleans the surface of the photoconductor after the toner image has been transferred and before it is charged with 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 provided 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 provided with a static elimination device that irradiates the surface of an electrophotographic photosensitive member with static elimination light to eliminate static electricity after the transfer of the toner image and before charging; and an apparatus provided with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing 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 which primarily transfers the toner image formed on the surface of an electrophotographic photosensitive body onto the surface of the intermediate transfer body, and a secondary transfer device which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

[0253] The image forming apparatus according to the present 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. The process cartridge may include, in addition to the electrophotographic photosensitive member, 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. Principal 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 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 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 via the intermediate transfer body 50, and the intermediate transfer body 50 is disposed with a part of it in contact with the electrophotographic photoreceptor 7. Although not shown, the image forming apparatus 100 also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown) correspond to an example of a transfer device.

[0257] 3 supports an electrophotographic photoreceptor 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) integrally 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 photoreceptor 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 including a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of the electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists in cleaning, which are 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 for a long period of time) is remarkable in a contact type charging device.

[0261] As the charging device 8, for example, a contact-type charging member using a conductive or semiconductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. Also, a non-contact type roller charger, a scorotron charger or corotron charger that utilizes corona discharge, or other chargers known per se, can be used.

[0262] -Exposure equipment- The exposure device 9 may be, for example, an optical device that exposes the surface of the electrophotographic photoreceptor 7 with 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 photoreceptor. The wavelength of the semiconductor laser is mainly near infrared light having an oscillation wavelength of about 780 nm. However, it is not limited to this wavelength, and a laser having an oscillation wavelength of 600 nm or a blue laser having an oscillation wavelength of 400 nm to 450 nm may also be used. In addition, a surface-emitting laser light source capable of outputting multiple beams is also effective for forming a color image.

[0263] -Developing device- The developing device 11 may be, for example, a general developing device that develops by contacting or non-contacting a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected according to the purpose. For example, it may be a known developing device that has a function of attaching a one-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, roller, or the like. Among them, it is preferable to use a developing roller that holds a developer on its surface.

[0264] The developer used in the developing device 11 may be a one-component developer containing only toner, or may be 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 and cleaning type may also be adopted.

[0266] -Transfer device- Examples of the transfer device 40 include known transfer chargers such as a contact type transfer charger using a belt, roller, film, rubber blade, etc., and 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 image forming apparatus according to the present embodiment. 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 body 50, and one electrophotographic photosensitive body is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem type. EXAMPLES

[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 in no way limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are by mass. In the following description, syntheses, treatments, manufactures, 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 composition of the polyarylate resin. A2-3 and the like shown in Table 1 are specific examples of the above-mentioned dicarboxylic acid unit (A). B1-2 and the like shown in Table 1 are specific examples of the diol unit (B) described above.

[0271] [Table 1]

[0272] <Production of photoconductors> The following materials were prepared as materials for forming 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 45000 Polycarbonate resin (PC3), viscosity average molecular weight 40,000

[0275] [ka]

[0276] Phenolic compounds (PH1): Adeka STAB AO-30, ADEKA Corporation Phenolic compounds (PH2): Adeka STAB AO-50, ADEKA Corporation Phenolic compounds (PH3): Adeka 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 (trade 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, trade name: Sumidur 3175, Sumitomo Bayer Urethane Co., Ltd.), 45.5 parts of zinc oxide (trade name: SMZ-017N, Teika Co., Ltd.) surface-treated with a silane coupling agent (trade name: KBM603, Shin-Etsu Chemical Co., Ltd.), and 0.27 parts of the following compound were added and stirred, and then dispersed for 2 hours in a sand mill using glass beads with a diameter of 1 mm. Furthermore, 0.01 parts of dioctyltin dilaurate and 2 parts of silicone resin particles (trade name: Tospearl 145, GE Toshiba Silicone 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 of 15 parts of hydroxygallium phthalocyanine (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in the X-ray diffraction spectrum using CuKα characteristic X-rays) as a charge generating material, 10 parts of vinyl chloride-vinyl acetate copolymer resin (product name: VMCH, Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using glass beads with a diameter of 1 mm 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 a charge generating layer was dip-coated on the undercoat layer and dried at room temperature to form a charge generating layer with a layer thickness of 0.25 μm.

[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 on the charge generating layer and dried at 143° C. for 30 minutes to form a charge transport layer with a layer thickness of 33 μm. Thus, a photoreceptor 1 was 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, and 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 ratio shown in Table 2 is the mass ratio with respect to the total of the polyarylate resin and the polycarbonate resin, and the phenol compound content shown in Table 2 is the mass ratio with respect to the total mass of the 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 a toner and a 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 temperature and 50% relative humidity. During this image formation period, the apparatus was stopped once after printing 10 sheets for the performance evaluation described later.

[0285] [RzJIS measurement] The RzJIS of the outer peripheral surface of the photoconductor was measured before use and after the above-mentioned image formation. The measurement method is as described above. The results are shown in Table 2. The Z-axis resolution of the AFM system used in the measurements is 0.01 nm. If the surface roughness was not detectable, it is recorded as "<0.01" in Table 2.

[0286] [Photoconductor / charging device dirt] After 10 sheets and 10,000 sheets of the above image formation, the outer circumferential surfaces of the photoconductor and the 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 photoconductor or charging device when viewed with a magnifying glass. 4: A slight streak of dirt is visible on the photoconductor with a magnifying glass. No dirt is visible on the charging device with a magnifying glass. 3: Streaks of dirt are visible on the photoconductor with the naked eye. No dirt is visible on the charging device with a magnifying glass. 2: Streaks of adhesion are visible to the naked eye on the photoconductor. Slight streaks of adhesion are visible on the charging device with a magnifying glass. This is not a problem for monochrome printing, but is at a level that will become a problem for 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 is problematic even for monochrome printing.

[0288] [Blade whine] Blade noise (abnormal noise caused by vibration of the photoconductor cleaning blade) is likely to occur when the rotating photoconductor stops. In 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 classified as follows. The results are shown in Table 2.

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

[0290] [Scratches on the outer surface of the photoconductor] After outputting 10,000 sheets of the above-mentioned image formation, the outer peripheral surface of the photoconductor was observed with the naked eye and with a loupe (×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 streaks can be seen with a magnifying glass. 3: Streaks are clearly visible with a magnifying glass. 2: Faint streaks are visible to the naked eye. 1: Lines are clearly visible to the naked eye.

[0292] [Oxidation deterioration of photoconductor] After outputting 10,000 sheets of the above image formation, 1,000 black images with an image density of 0.5% were output 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 2 days. Then, in the same environment, 100 black images with an image density of 5% were output on A4 plain paper. The 100 images were observed with the naked eye and with a loupe (×25) and classified as follows. The results are shown in Table 2. This series of image formation imitates office use on a two-day work week. During the time when the office air conditioning is turned off, the image forming device is placed in a high-temperature and 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 loupe on the first image. No image defects can be seen from the second image onwards. 3: The first image has a faint image defect that can be seen with the naked eye. The second through 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 sheets. Image defects are no longer visible even with a loupe on the 11th to 100th sheets. 1: Image defects are visible to the naked eye on sheets 1 to 100.

[0294] The resin ratio shown in Table 2 is the mass ratio with respect to the total of the polyarylate resin and the polycarbonate resin. The content of the phenol compound shown in Table 2 is the mass ratio with respect to the total mass of the charge transport layer (i.e., the 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] (Additional Note) (((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 comprises a hindered phenol compound. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the two or more kinds 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 an image forming apparatus; Process cartridge. (((13))) An electrophotographic photoreceptor according to any one of (((1))) to (((11))); a charging device for charging a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring 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 photoreceptor and that cleans the surface of the electrophotographic photoreceptor; Image forming device.

[0298] According to (((1))), (((3))), (((4))), (((5))), (((6))), (((7))) or (((11))), an electrophotographic photoreceptor is provided which is less susceptible to contamination of the charging member and abnormal noise due to vibration of the photoreceptor cleaning blade over a long period of time, as compared with 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 susceptible to contamination of the charging member and abnormal noise caused by vibration of the photoreceptor cleaning blade over a long period of time, compared with an electrophotographic photoreceptor having an outer peripheral surface RzJIS of less than 0.5 nm or more than 50 nm. According to (((8))), an electrophotographic photoreceptor is provided which is less susceptible to contamination of the charging member and abnormal noise caused by vibration of the photoreceptor cleaning blade over a long period of time, as compared with a configuration in which the outermost 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 susceptible to contamination of the charging member and abnormal noise caused by vibration of the photoreceptor cleaning blade over a long period of time, as compared with electrophotographic photoreceptors in which the proportion of polyarylate resin in the total amount of polyarylate resin and polycarbonate resin contained in the outermost layer is less than 25 mass % or more than 75 mass %. According to (((12))), a process cartridge is provided which is less susceptible to 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 process cartridge in which the RzJIS of the outer peripheral surface of the electrophotographic photoreceptor is less than 0.1 nm or exceeds 100 nm. According to (((13))), an image forming apparatus is provided which is less susceptible to 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 exceeds 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, a polyarylate resin, a polycarbonate resin, and a phenol compound; The polyarylate resin and the polycarbonate resin each have a biphenyl-containing structural unit represented by the following formula (BP): The RzJIS of the outer peripheral surface is 0.1 nm or more and 100 nm or less. Electrophotographic photoreceptor. 【Chemistry 1】 In formula (BP), j is an integer of 0 to 4, j R 1 s are each independently a methyl group or an ethyl group, k is an integer of 0 to 4, and k R 2 s are each independently a methyl group or an ethyl group.

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 polyarylate resin comprises 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 2】 In formula (A), Ar Ａ１ and Ar Ａ２ each independently represents an aromatic ring which may have a substituent; 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; L Ｂ is a single bond, an oxygen atom, a sulfur atom or -C(Rb １ )(Rb ２ )-, n Ｂ１ is 0, 1 or 2. １ and Rb ２ each independently represents 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; Rb １ and Rb ２ may be bonded to form a cyclic alkyl group.

5. The electrophotographic photoreceptor according to claim 4, 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 3】 In formula (A1), n １０１ is an integer of 0 to 4, １０１ Ra １０１ each independently represents 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 each independently represents 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 each independently represents 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 each independently represents 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 each independently represents 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.

6. The electrophotographic photoreceptor according to claim 4, wherein 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). 【Chemistry 4】 【Chemistry 5】 In formula (B1), Rb １０１ is a branched alkyl group having 4 to 20 carbon atoms, Rb ２０１ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, Rb ４０１ , Rb ５０１ , Rb ８０１ and Rb ９０１ each independently represents 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; Rb ２０２ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, Rb ４０２ , Rb ５０２ , Rb ８０２ and Rb ９０２ each independently represents 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; ４０３ , Rb ５０３ , Rb ８０３ and Rb ９０３ each independently represents 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 each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; ４０４ , Rb ５０４ , Rb ８０４ and Rb ９０４ each independently represents 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, Rb ２０５ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, Rb ４０５ , Rb ５０５ , Rb ８０５ and Rb ９０５ each independently represents 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 each independently represents 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 each independently represents 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 each independently represents 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.

7. 2. The electrophotographic photoreceptor according to claim 1, 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.

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

9. The electrophotographic photoreceptor according to any one of claims 1 to 8 is provided, Attaching to and detaching from an image forming apparatus; Process cartridge.

10. An electrophotographic photoreceptor according to any one of claims 1 to 8, a charging device for charging a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring 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 photoreceptor and that cleans the surface of the electrophotographic photoreceptor; Image forming device.

Images