Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor in which potential fluctuations after electrostatic latent image formation are suppressed. [Solution] The laminated photosensitive layer comprises a conductive substrate, an undercoat layer disposed on the conductive substrate, and a charge generating layer and a charge transport layer disposed on the undercoat layer, wherein the charge transport layer contains a charge transport material and a polyarylate resin, the polyarylate resin contains dicarboxylic acid units represented by the following formula (A) and diol units represented by formula (B), and the capacitance of the undercoat layer is 1.0 × 10 -10 F or higher 3.0×10 -9 Electrophotographic photoreceptor with an F value of 0 or less. JPEG2026084601000053.jpg44109

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an electrophotographic photoreceptor comprising: a support; an undercoat layer provided on the support, comprising at least a binder resin, metal oxide particles, and an electron-accepting compound having an anthraquinone structure, wherein the content of the electron-accepting compound is 0.5% by mass or more and 1.5% by mass or less relative to the metal oxide particles, and the contact angle of the metal oxide particles with respect to water is 7 degrees or more and 12 degrees or less; and a photosensitive layer provided on the undercoat layer.

[0003] Patent Document 2 discloses an electrophotographic photoreceptor comprising a conductive substrate, an undercoat layer provided on the conductive substrate, the undercoat layer comprising a binder resin, metal oxide particles, and an electron-accepting compound having an anthraquinone skeleton represented by the following general formula (1A), wherein the reflectance RL of light in the wavelength range of 470 nm to 510 nm is 2% to 5%, and a photosensitive layer provided on the undercoat layer.

[0004] Patent Document 3 describes a conductive substrate, an undercoat layer provided on the conductive substrate, a charge generation layer provided on the undercoat layer, a charge transport layer provided on the charge generation layer, and a protective layer provided on the charge transport layer, wherein the undercoat layer contains a conductive agent, the number of primary particles of the conductive agent is 58% or less of the sum of the number of primary particles and secondary particles of the conductive agent, and the charge mobility μ(CTL) of the charge transport layer and the charge mobility μ(OCL) of the protective layer are μ(CTL) ≥ 1.0 × 10 -5 (cm 2 / Vs) and μ(OCL) ≥ 0.68 × 10 -5 (cm 2 An electrophotographic photoreceptor satisfying / Vs) is disclosed. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-242483 [Patent Document 2] Patent No. 6838324 [Patent Document 3] Japanese Patent Publication No. 2024-043372 [Overview of the project] [Problems that the invention aims to solve]

[0006] The problem of this disclosure is to provide an electrophotographic photoreceptor comprising a conductive substrate, a base layer disposed on the conductive substrate, and a multilayer photosensitive layer disposed on the base layer having a charge generation layer and a charge transport layer, wherein the charge transport layer contains a charge transport material and a polyarylate resin containing dicarboxylic acid units represented by formula (A) and diol units represented by formula (B), wherein the capacitance of the base layer is 1.0 × 10 -10 Less than F, or 3.0 × 10 -9 The objective is to provide an electrophotographic photoreceptor in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases where the F value exceeds F. [Means for solving the problem]

[0007] The following embodiments are included as specific means for solving the aforementioned problems.

[0008] <1> The device comprises a conductive substrate, an undercoat layer disposed on the conductive substrate, and a laminated photosensitive layer disposed on the undercoat layer having a charge generation layer and a charge transport layer, wherein the charge transport layer contains a charge transport material and a polyarylate resin. The polyarylate resin comprises a dicarboxylic acid unit represented by the following formula (A) and a diol unit represented by the following formula (B). The capacitance of the aforementioned lower layer is 1.0 × 10 -10 F or higher 3.0×10 -9 Electrophotographic photoreceptor with an F value of 0 or less. [ka] In formula (A), Ar A1 and Ar A2 are each independently an aromatic ring which may have a substituent, and L A is a single bond or a divalent linking group, and n A1 is 0, 1, or 2. In formula (B), Ar B1 and Ar B2 are each independently an aromatic ring which may have a substituent, and L B is a single bond, an oxygen atom, a sulfur atom, or -C(Rb 1 )(Rb 2 )-, and n B1 is 0, 1, or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may combine to form a cyclic alkyl group. <2> The electrophotographic photoreceptor according to <1>, wherein the relative permittivity of the charge transport layer is 3.0 or more and 5.0 or less. <3> The electrophotographic photoreceptor according to <2>, wherein the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat layer (relative permittivity of the charge transport layer / relative permittivity of the undercoat layer) is 0.010 or more and 0.400 or less. <4> The electrophotographic photoreceptor according to any one of <1> to <3>, wherein the undercoat layer contains zinc oxide particles imparted with an electron-accepting compound at 62% by mass or more and 75% by mass or less with respect to the undercoat layer. <5> The electrophotographic photoreceptor according to <5>, wherein the electron-accepting compound is an anthraquinone derivative having three OH groups or having two OH groups and one alkoxy group. <6> The electrophotographic photoreceptor according to <4>, wherein the anthraquinone derivative is an alizarin derivative represented by formula (C). [ka] In formula (C), R represents a hydroxyl group or an alkoxy group having 1 to 10 carbon atoms. <7> The thickness of the aforementioned underlayer is 17 μm or more and 35 μm or less. <1> ~ <6> The electrophotographic photoreceptor described above. <8> The charge transport layer further comprises a polycarbonate resin, and the polyarylate resin and the polycarbonate resin each have a constituent unit containing biphenyl represented by the following formula (BP). <1> ~ <7> An electrophotographic photoreceptor as described in any one of the following. [ka] In equation (BP), j is an integer between 0 and 4, and j R 1 Each is independently either a methyl group or an ethyl group, k is an integer between 0 and 4, and there are k R 2 These are independently either a methyl group or an ethyl group. <9> <1> ~ <8> A process cartridge equipped with an electrophotographic photoreceptor as described in any one of the following, which can be attached to and detached from an image forming apparatus. <10> <1> ~ <8> An image forming apparatus comprising: an electrophotographic photoreceptor as described in any one of the above; charging means for charging the surface of the electrophotographic photoreceptor; electrostatic latent image forming means for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image; and transfer means for transferring the toner image to the surface of a recording medium. [Effects of the Invention]

[0009] <1> According to the invention, an electrophotographic photoreceptor comprises a conductive substrate, an undercoat layer disposed on the conductive substrate, and a laminated photosensitive layer disposed on the undercoat layer having a charge generating layer and a charge transport layer, wherein the charge transport layer contains a charge transport material and a polyarylate resin containing a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), wherein the capacitance of the undercoat layer is 1.0 × 10 -10 Less than F, or 3.0 × 10 -9 Compared to cases where the F value exceeds a certain threshold, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed. <2> According to the invention, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases where the relative permittivity of the charge transport layer is less than 3.0 or greater than 5.0. <3> According to the present invention, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases where the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the underlying layer (relative permittivity of the charge transport layer / relative permittivity of the underlying layer) is less than 0.010 or greater than 0.400. <4> According to the invention, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed, compared to the case in which the undercoat contains zinc oxide particles to which an electron-accepting compound is applied in an amount of less than 62% by mass or more than 75% by mass relative to the undercoat. <5> According to the invention, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to when the electron-accepting compound is an anthraquinone. <6> According to the invention, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to the case where the electron-accepting compound is alizarin. <7> According to the invention, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases where the thickness of the undercoat layer is less than 17 μm or more than 35 μm. <8> According to the invention, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to a case in which neither the polyarylate resin nor the polycarbonate resin has a constituent unit containing biphenyl represented by the above formula (BP). <9> or <10> According to the invention, an electrophotographic photoreceptor comprises a conductive substrate, an undercoat layer disposed on the conductive substrate, and a laminated photosensitive layer disposed on the undercoat layer having a charge generating layer and a charge transport layer, wherein the charge transport layer contains a charge transport material and a polyarylate resin containing a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), wherein the capacitance of the undercoat layer is 1.0 × 10 -10 Less than F, or 3.0 × 10 -9 A process cartridge or image forming apparatus is provided that features an electrophotographic photoreceptor in which potential fluctuations after electrostatic latent image formation are suppressed compared to the case in which an electrophotographic photoreceptor with a potential f-value exceeding F is applied. [Brief explanation of the drawing]

[0010] [Figure 1] This is a partial cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to this embodiment. [Figure 2] This is a schematic diagram showing an example of an image forming apparatus according to this embodiment. [Figure 3] This is a schematic diagram showing another example of the image forming apparatus according to this embodiment. [Modes for carrying out the invention]

[0011] The embodiments of this disclosure are described below. These descriptions and embodiments are illustrative and do not limit the scope of the embodiments.

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

[0013] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that their objectives are achieved.

[0014] When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto.

[0015] In this disclosure, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this disclosure, if there are multiple types of the substance corresponding to each component in the composition, it means the total amount of those multiple types of substances present in the composition unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified.

[0016] In this disclosure, alkyl groups include linear, branched, and cyclic alkyl groups unless otherwise specified.

[0017] In this disclosure, organic groups, aromatic rings, linking groups, alkyl groups, aryl groups, aralkyl groups, alkoxy groups, and aryloxy groups may have hydrogen atoms substituted by halogen atoms.

[0018] <Electrophotographic photoconductor> The electrophotographic photoreceptor (hereinafter also referred to as the photoreceptor) according to this embodiment comprises a laminated photoreceptor having a conductive substrate, an undercoat layer, a charge generation layer, and a charge transport layer. The undercoat layer is provided on the conductive substrate. The laminated photoreceptor is provided on the undercoat layer. The charge transport layer contains a charge transport material and a polyarylate resin containing dicarboxylic acid units represented by formula (A) and diol units represented by formula (B) above. The capacitance of the undercoat layer is 1.0 × 10⁻⁶. -10 F or higher 3.0×10 -9It is less than or equal to F. In this embodiment, the photoreceptor is located in the outermost layer, specifically the charge transport layer.

[0019] The photoreceptor according to this embodiment, with the above configuration, is a photoreceptor in which potential fluctuations after electrostatic latent image formation are suppressed. The reason for this is presumed to be as follows.

[0020] To enhance the chargeability of a photoreceptor, it is effective to use a resin with a high dielectric constant in the charge transport layer. One such resin is a polyarylate resin containing dicarboxylic acid units represented by formula (A) and diol units represented by formula (B) above. On the other hand, if a polyarylate resin with a high dielectric constant is used in the charge transport layer, the voltage applied to the charge transport layer decreases when the photoreceptor is charged, making it easier for trace amounts of carriers to remain. In particular, when images are repeatedly formed over a long period of time, the influence of trace amounts of residual carriers causes potential fluctuations after electrostatic latent image formation. These potential fluctuations cause image quality defects such as fogging (i.e., the formation of point-like images in non-image areas) or ghosting (i.e., afterimage phenomena caused by the retention of the history of the previous image).

[0021] Therefore, in the photoreceptor according to this embodiment, the capacitance of the underlayer is increased in order to increase the voltage applied to the charge transport layer. In a multilayer photoreceptor, the voltage across each layer is calculated by the inverse ratio of the capacitances of each layer. Therefore, increasing the capacitance of the underlayer increases the voltage across the charge transport layer. This suppresses the retention of trace amounts of carriers in the charge transport layer even when images are repeatedly formed over a long period, thereby suppressing potential fluctuations after electrostatic latent image formation.

[0022] For the reasons stated above, it is presumed that the photoreceptor according to this embodiment will be a photoreceptor in which potential fluctuations after electrostatic latent image formation are suppressed.

[0023] The details of the photoreceptor according to this embodiment will be described below.

[0024] Figure 1 is a schematic partial cross-sectional view showing an example of the layer structure of a photoreceptor according to this embodiment. The photoreceptor 10A shown in Figure 1 has a stacked photoreceptor layer. The photoreceptor 10A has a structure in which a base layer 2, a charge generation layer 3, and a charge transport layer 4 are stacked in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute the photoreceptor layer 5 (a so-called functionally separated photoreceptor layer). The photoreceptor 10A may have an intermediate layer (not shown) between the base layer 2 and the charge generation layer 3.

[0025] The following describes each layer of the photoreceptor in detail. However, the symbols will be omitted, and the individual layers of the photoreceptor will be described accordingly.

[0026] [Conductive substrate] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Other examples of conductive substrates include paper, resin films, and belts 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 volume resistivity of 10⁻¹⁰. 13 This refers to a value less than Ω·cm.

[0027] When an 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 irradiated with laser light. While roughening to prevent interference fringes is not particularly necessary when using non-interfering light as the light source, it is beneficial for extending the lifespan by suppressing the occurrence of defects due to surface irregularities of the conductive substrate.

[0028] Methods for roughening a surface include, for example, wet honing, which involves suspending an abrasive in water and spraying it onto a conductive substrate; centerless grinding, which involves pressing a conductive substrate against a rotating grinding wheel and continuously grinding it; and anodizing.

[0029] One method for roughening the surface is to disperse conductive or semiconductive powder in a resin without roughening the surface of the conductive substrate, to form a layer on the surface of the conductive substrate, and then roughen the surface with the particles dispersed in that layer.

[0030] Anodizing roughening treatment involves forming an oxide film on the surface of a conductive substrate (e.g., aluminum) by anodizing it in an electrolyte solution. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film to block the micropores of the oxide film by volume expansion due to a hydration reaction using pressurized steam or boiling water (metal salts such as nickel may be added), thereby converting it into a more stable hydrated oxide.

[0031] The thickness of the anodic oxide film is preferably, for example, 0.3 μm to 15 μm. When the film thickness is within this range, it tends to exhibit barrier properties against injection and tends to suppress the increase in residual potential due to repeated use.

[0032] The conductive substrate may be treated with an acidic treatment solution or with boehmite. Treatment with an acidic solution is carried out, for example, as follows: First, an acidic solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic solution is, for example, in the range of 10% to 11% by mass for phosphoric acid, 3% to 5% by mass for chromic acid, and 0.5% to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness is preferably 0.3 μm to 15 μm.

[0033] 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 it with heated steam at 90°C to 120°C for 5 to 60 minutes. The film thickness is preferably 0.1 μm to 5 μm. This can be further treated with anodic oxidation using an electrolyte solution with low film solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0034] (subbing layer) The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0035] As for inorganic particles, for example, powder resistance (volume resistivity) 10 2 Ω cm or more 10 11 Examples include inorganic particles with a size of Ω·cm or less. Among these, suitable inorganic particles having the above-mentioned resistance values ​​include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0036] The specific surface area of ​​inorganic particles using the BET method is, for example, 10 m². 2 A value of 1g or more is preferable. The volume-average particle size of the inorganic particles is preferably between 50 nm and 2000 nm (preferably between 60 nm and 1000 nm).

[0037] The inorganic particle content is preferably 10% by mass or more and 80% by mass or less relative to the binder resin, and more preferably 40% by mass or more and 80% by mass or less.

[0038] The inorganic particles may be surface-treated. Two or more types of inorganic particles with different surface treatments or particle sizes may be mixed and used.

[0039] Examples of surface treatment agents include silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, and surfactants. Silane coupling agents are particularly preferred, and silane coupling agents having an amino group are more preferred.

[0040] 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.

[0041] Silane coupling agents may be used in combination of two or more types. 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-methacrylateoxypropyl-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.

[0042] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry or wet method.

[0043] The amount of surface treatment agent applied is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0044] Here, the lower layer is preferably made of zinc oxide particles as inorganic particles, from the viewpoint of setting the capacitance within the above range and suppressing potential fluctuations after electrostatic latent image formation. In particular, zinc oxide particles to which an electron-accepting compound has been added are preferred as inorganic particles.

[0045] - Zinc oxide particles conjugated with electron-accepting compounds - The zinc oxide particles to which the electron-accepting compound is attached are preferably present in an amount of 62% to 75% by mass relative to the base layer, and more preferably in an amount of 65% to 73% by mass. When the content of zinc oxide particles coated with electron-accepting compounds is 62% by mass or more, the capacitance of the underlying layer increases, and the voltage applied to the charge transport layer tends to increase. As a result, potential fluctuations after electrostatic latent image formation tend to be suppressed. When the content of zinc oxide particles contaminated with electron-accepting compounds is 75% by mass or less, excessively high capacitance in the underlying layer is suppressed. As a result, potential fluctuations after electrostatic latent image formation are more easily suppressed.

[0046] By ensuring that the content of zinc oxide particles contaminated with electron-accepting compounds meets the above range, the dielectric constant of the lower layer of the photoreceptor increases, and the voltage applied to the charge transport layer increases, thereby suppressing potential fluctuations after electrostatic latent image formation.

[0047] -Electron-accepting compounds- The electron-accepting compound is preferably an anthraquinone derivative having three OH groups or two OH groups and one alkoxy group. The anthraquinone derivative is preferably an alizarin derivative represented by formula (C). When the above compound is applied as an electron-accepting compound, the capacitance of the underlying layer increases, and the voltage applied to the charge transport layer increases. As a result, potential fluctuations after electrostatic latent image formation are suppressed. The reason for this is presumed to be as follows: When the same amount of the above anthraquinone derivative and the alizarin derivative represented by formula (C) below is added to the charge transport layer, the difference in molecular weight results in a larger mass-based and volume-based proportion of the lower layer compared to anthraquinone or alizarin. As a result, the above anthraquinone derivative and the alizarin derivative represented by formula (C) below form charge transfer complexes with zinc oxide particles over a wider area. Therefore, it is presumed that the capacitance of the lower layer increases.

[0048] [ka] In formula (C), R represents a hydroxyl group or an alkoxy group having 1 to 10 carbon atoms.

[0049] In formula (C), the number of carbon atoms in the alkoxy group represented by R is preferably 1 to 4, and more preferably 1 to 2.

[0050] Examples of electron-accepting compounds include purpurin and compound (A) below. Among these, purpurin and compound (A) below are preferred as electron-accepting compounds. In addition, other electron-accepting compounds such as quinizalin, anthralphine, or derivatives thereof may be used. [ka]

[0051] Methods for imparting electron-accepting compounds to inorganic particles (i.e., methods for attaching them to the surface of inorganic particles) include, for example, dry methods or wet methods.

[0052] The dry method involves, for example, adding an electron-accepting compound, either directly or dissolved in an organic solvent, dropwise while stirring inorganic particles with a mixer that has a high shear force, or spraying it with dry air or nitrogen gas, to adhere the electron-accepting compound to the surface of the inorganic particles. When adding or spraying the electron-accepting compound, it is preferable to do so at a temperature below the boiling point of the solvent. After adding or spraying the electron-accepting compound, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained.

[0053] The wet method involves dispersing inorganic particles in a solvent using, for example, a stirrer, ultrasonic disperser, sand mill, attritor, or ball mill, while adding an electron-accepting compound. After stirring or dispersion, the solvent is removed, and the electron-accepting compound adheres to the surface of the inorganic particles. Solvent removal methods include, for example, filtration or distillation. After solvent removal, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained. In the wet method, the water content of the inorganic particles may be removed before adding the electron-accepting compound. Examples of this include removing water while stirring and heating in the solvent, or removing water by azeotrope with the solvent.

[0054] Furthermore, the attachment of the electron-accepting compound may be performed before or after surface treatment with a surface treatment agent on the inorganic particles, or it may be performed simultaneously with the attachment of the electron-accepting compound and surface treatment with the surface treatment agent.

[0055] The content (i.e., amount) of the electron-accepting compound is preferably 0.01% to 20% by mass relative to the inorganic particles, and more preferably 0.01% to 10% by mass.

[0056] Examples of known polymer compounds used as the binder resin for the undercoat include acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, unsaturated polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, alkyd resin, epoxy resin, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Examples of binder resins used in the undercoat include charge-transporting resins having charge-transporting groups, conductive resins (e.g., polyaniline), and the like.

[0057] Among these, a resin insoluble in the coating solvent of the upper layer is preferred as the binder resin used for the undercoat layer. In particular, a resin obtained by the reaction of a curing agent with at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin is preferred. When using two or more of these binder resins in combination, the mixing ratio is set as needed.

[0058] The undercoat may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of known additives include electron-transporting pigments such as polycyclic condensation and azo pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. As mentioned above, silane coupling agents are used for surface treatment of inorganic particles, but they may also be added to the undercoat as additives.

[0059] Examples of silane coupling agents used as additives include vinyltrimethoxysilane, 3-methacrylateoxypropyl-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.

[0060] Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetate 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.

[0061] Examples of titanium chelate compounds include tetraisopropyl titanate, tetran-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.

[0062] Examples of aluminum chelating compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0063] These additives may be used individually or as a mixture or polycondensate of multiple compounds.

[0064] -Capacitance of the lower layer- The capacitance of the lower layer is 1.0 × 10⁻⁶ -10 F or higher 3.0×10 -9 It is less than or equal to F. The capacitance of the underlayer is more preferably 2.5 × 10⁻⁶. -10 F or higher 2.0×10 -9 F or less, more preferably 5.3 × 10 -10 F or more 1.5×10 -9 It is less than or equal to F. The capacitance of the lower layer is 1.0 × 10⁻⁶ -10 If the voltage is less than F, the voltage across the charge transport layer weakens, and the potential fluctuations after electrostatic latent image formation worsen. The capacitance of the lower layer is 3.0 × 10 -9 If the F value exceeds a certain threshold, the voltage applied to the lower layer becomes excessively low, which again worsens the potential fluctuations after the formation of the electrostatic latent image.

[0065] One method for setting the capacitance of the undercoat layer within the above range is to use an alizarin derivative represented by the above formula (C) as the electron-accepting compound, and to adjust the thickness of the undercoat layer to 17 μm or more and 35 μm or less.

[0066] The capacitance of the undercoat is measured by removing the charge transport layer and charge generation layer with a solvent, leaving a single layer of the undercoat attached to the substrate. In this state, a 3mm radius Au electrode is formed on the surface of the undercoat, and the capacitance is measured using an impedance analyzer with a DC voltage of 10V and an AC voltage of 2V applied to the undercoat from the conductive substrate and the Au electrode, at an AC frequency of 1Hz.

[0067] -Film thickness of the underlayer- The thickness of the undercoat layer is set to a range of 17 μm to 35 μm, more preferably 18 μm to 26 μm. When the thickness of the undercoat layer is 17 μm or more, the capacitance of the undercoat layer increases, the voltage applied to the charge transport layer increases, and potential fluctuations after electrostatic latent image formation are more easily suppressed. If the thickness of the undercoat layer is 35 μm or less, it is possible to suppress the excessive decrease in capacitance of the undercoat layer and the resulting excessive decrease in the voltage applied to the charge transport layer, thereby making it easier to suppress potential fluctuations after electrostatic latent image formation. When the film thickness of the undercoat satisfies the above configuration, the capacitance of the undercoat increases in the photoreceptor, and the voltage applied to the charge transport layer increases. As a result, potential fluctuations after electrostatic latent image formation are suppressed.

[0068] The underlayer should ideally have a Vickers hardness of 35 or higher. The surface roughness (ten-point average roughness) of the undercoat layer should be adjusted to between 1 / (4n) (where n is the refractive index of the upper layer) and 1 / 2 of the exposure laser wavelength λ used, in order to suppress moiré patterns. Resin particles may be added to the undercoat to adjust the surface roughness. Examples of resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. The surface of the undercoat may also be polished to adjust the surface roughness. Polishing methods include buffing, sandblasting, wet honing, and grinding.

[0069] There are no particular restrictions on the formation of the undercoat layer, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of an undercoat-forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0070] Solvents for preparing the coating solution for forming the undercoat 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. Examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0071] Known methods for dispersing inorganic particles when preparing a coating solution for forming an undercoat include, for example, roll mills, ball mills, vibrating ball mills, attritors, sand mills, colloid mills, and paint shakers.

[0072] Conventional methods for applying the undercoating solution onto a conductive substrate include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0073] (Middle class) Although not shown in the diagram, an intermediate layer may be further provided between the undercoat layer and the photosensitive layer. The intermediate layer is, for example, a layer containing a resin. Examples of resins used in the intermediate layer include polymer compounds such as acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, and melamine resin. The intermediate layer may contain an organometallic compound. Examples of organometallic compounds used in the intermediate layer include those containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in these intermediate layers may be used individually, as a mixture of multiple compounds, or as polycondensates.

[0074] Among these, the intermediate layer is preferably a layer containing an organometallic compound that contains zirconium atoms or silicon atoms.

[0075] There are no particular restrictions on the formation of the intermediate layer, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of an intermediate layer-forming coating solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary. Conventional methods such as immersion coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating are used to form the intermediate layer.

[0076] The thickness of the intermediate layer is preferably set to a range of 0.1 μm to 3 μm, for example. The intermediate layer may also be used as a base layer.

[0077] (Charge generation layer) The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Alternatively, the charge generation layer may be a vapor-deposited layer of the charge generation material. A vapor-deposited layer of the charge generation material is suitable when using non-coherent light sources such as LEDs (Light Emitting Diodes) or organic EL (Electro-Luminescence) image arrays.

[0078] Examples of charge-generating materials include azo pigments such as bisazo and trisazo; fused aromatic pigments such as dibromoanthonthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0079] 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; and titanyl phthalocyanine are more preferable.

[0080] On the other hand, to accommodate laser exposure in the near-ultraviolet region, preferred charge-generating materials include fused aromatic pigments such as dibromoanthoten; thioindigo pigments; porphyrazine compounds; zinc oxide; trigonal selenium; and bisazo pigments.

[0081] The above charge generating material may also be used when using non-coherent light sources such as LEDs and organic EL image arrays, which have a central emission wavelength between 450 nm and 780 nm.

[0082] When n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark currents are less likely to occur, and image defects called black spots can be suppressed even in thin films. Furthermore, the n-type is determined using the commonly used time-of-flight method, based on the polarity of the photocurrent that flows. Those that are more likely to carry electrons as carriers than holes are classified as n-type.

[0083] The binder resin used in the charge generation layer can be selected from a wide range of insulating resins, or it may be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (such as polycondensates of bisphenols and aromatic divalent carboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinylpyrrolidone resin. Here, "insulating properties" refer to a volume resistivity of 10¹³ Ω·cm or higher. These binder resins can be used individually or in combination of two or more types.

[0084] Furthermore, the mixing ratio of the charge-generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass ratio.

[0085] The charge generation layer may also contain other well-known additives.

[0086] The formation of the charge generation layer is not particularly limited, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of a charge generation layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it as necessary. The charge generation layer may also be formed by vapor deposition of the charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when using fused aromatic pigments or perylene pigments as the charge generation material.

[0087] Solvents for preparing the coating solution for forming the charge generation layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene. These solvents can be used individually or in mixtures of two or more.

[0088] Methods for dispersing particles (e.g., charge-generating materials) in a coating solution for forming a charge-generating layer include, for example, media dispersers such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, as well as media-less dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include collision methods, which disperse the dispersion by causing liquid-liquid collisions or liquid-wall collisions under high pressure, and penetration methods, which disperse the dispersion by penetrating fine channels under high pressure. Furthermore, during this dispersion, it is effective to set the average particle size of the charge-generating material in the coating solution for forming the charge-generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0089] Conventional methods for applying the charge-generating layer forming coating solution onto the undercoat (or intermediate layer) include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0090] The thickness of the charge generation layer is preferably set to a range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0091] [Charge transport layer] The charge transport layer is a layer containing a binder resin and a charge transport material.

[0092] (charge transport material) Examples of charge transport materials include 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, which are electron transport compounds. Other examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used individually or in combination of two or more, but are not limited to these.

[0093] Examples of polymeric charge transport materials include known chemical substances with charge transport properties such as poly-N-vinylcarbazole and polysilane. For example, polyester-based polymeric charge transport materials are preferred. Polymeric charge transport materials may be used alone or in combination with a binder resin.

[0094] Examples of charge transport materials or polymeric charge transport materials include polycyclic aromatic compounds, aromatic nitro compounds, aromatic amine compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds (especially triphenylamine compounds), diamine compounds, oxadiazole compounds, carbazole compounds, organic polysilane compounds, pyrazoline compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, cyano compounds, benzofuran compounds, aniline compounds, butadiene compounds, and resins having groups derived from these substances. Specifically, paragraphs 0078-0080 of JP 2021-117377, paragraphs 0046-0048 of JP 2019-035900, paragraphs 0052-0053 of JP 2019-012141, paragraphs 0122-0134 of JP 2021-071565, and paragraph 0078-0080 of JP 2021-015223 Examples of compounds include those described in paragraphs 0101-0110, paragraph 0116 of Japanese Patent Publication No. 2013-097300, paragraphs 0309-0316 of International Publication No. 2019 / 070003, paragraphs 0103-0107 of Japanese Patent Publication No. 2018-159087, and paragraphs 0102-0113 of Japanese Patent Publication No. 2021-148818.

[0095] From the viewpoint of charge mobility, the charge transport material preferably contains at least one selected from the group consisting of a chemical substance (C1) represented by the following formula (C1), a chemical substance (C2) represented by the formula (C2), a chemical substance (C3) represented by the formula (C3), and a chemical substance (C4) represented by the formula (C4).

[0096] [ka]

[0097] In equation (C1), Ar T1 Ar T2 and Ar T3 Each is independently an aryl group, -C6H4-C(R T4 )=C(RT5 )(R T6 ) or -C6H4-CH=CH-CH=C(R T7 )(R T8 ) is R T4 , R T5 , R T6 , R T7 and R T8 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T5 and R T6 When it is an aryl group, the aryl groups are -C(R 51 )(R 52 )-and / or-C(R 61 )=C(R 62 )- may be linked by a divalent group. R 51 , R 52 , R 61 and R 62 Each of these is independently either a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0098] The group in formula (C1) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0099] As for the chemical substance (C1), from the viewpoint of charge mobility, it is an aryl group or -C6H4-CH=CH-CH=C(R T7 )(R T8 A chemical substance having at least one of the following is preferred, and a chemical substance (C'1) represented by the following formula (C'1) is more preferred.

[0100] [ka]

[0101] In equation (C'1), R T111 , R T112 , R T121 , R T122 , R T131 and R T132Each is independently a hydrogen atom, a halogen atom, an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 3 carbon atoms), a phenyl group or a phenoxy group. Tj1, Tj2, Tj3, Tk1, Tk2 and Tk3 are each independently 0, 1 or 2.

[0102]

Chemical formula

[0103] In formula (C2), R T201 , R T202 , R T211 and R T212 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, -C(R T21 )=C(R T22 )(R T23 ) or -CH=CH-CH=C(R T24 )(R T25 ). R T21 , R T22 , R T23 , R T24 and R T25 are each independently a hydrogen atom, an alkyl group or an aryl group. R T221 and R T222 are each independently 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. Tm1, Tm2, Tn1 and Tn2 are each independently 0, 1 or 2.

[0104] The groups in formula (C2) may be substituted by a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0105] As the chemical substance (C2), from the viewpoint of charge mobility, an alkyl group, an aryl group, or -CH=CH-CH=C(R T24 )(R T25A chemical substance having at least one T24 )(R T25 ) is preferred, and a chemical substance having two

[0106]

Chemical formula

[0107] In formula (C3), R T301 , R T302 , R T311 and R T312 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, -C(R T31 )=C(R T32 )(R T33 ) or -CH=CH-CH=C(R T34 )(R T35 ). R T31 , R T32 , R T33 , R T34 and R T35 are each independently a hydrogen atom, an alkyl group or an aryl group. R T321 , R T322 and R T331 are each independently 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. To1, To2, Tp1, Tp2, Tq1, Tq2 and Tr1 are each independently 0, 1 or 2.

[0108] The group in formula (C3) may be substituted by a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0109]

Chemical formula

[0110] In equation (C4), R T401 , R T402 , R T411 and R T412 Each of these is independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, and -C(R T41 )=C(R T42 )(R T43 ) or -CH=CH-CH=C(R T44 )(R T45 ) is R T41 , R T42 , R T43 , R T44 and R T45 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T421 , R T422 and R T431 Each of these is independently 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. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 are each independently 0, 1, or 2.

[0111] The group in formula (C4) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0112] The amount of charge transport material contained in the charge transport layer is preferably 20% by mass or more and 70% by mass or less, relative to the total mass of the charge transport layer.

[0113] [Binding resin] The binder resin used in the charge transport layer includes dicarboxylic acid units represented by the following formula (A) (hereinafter referred to as "dicarboxylic acid units (A)") and diol units represented by the following formula (B) (hereinafter referred to as "diol units (B)"). In this disclosure, the polyarylate resin is also referred to as polyarylate resin (PA).

[0114] The dicarboxylic acid unit (A) is a constituent unit represented by the following formula (A).

[0115] [ka]

[0116] In equation (A), Ar A1 and Ar A2 Each of these is an aromatic ring which may independently have substituents, L A is a single bond or a divalent linking group, n A1 It is 0, 1, or 2.

[0117] Ar A1 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0118] Ar A1 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. A1 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0119] Ar A2 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0120] Ar A2 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. A2 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0121] LA When it is a divalent linking group, the divalent linking group can be, for example, an oxygen atom, a sulfur atom, -C(Ra 1 )(Ra 2 )- is one example. Here, Ra 1 and Ra 2 Each of these is 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, Ra 1 and Ra 2 These may be bonded together to form a cyclic alkyl group.

[0122] Ra 1 and Ra 2 The alkyl group having 1 to 10 carbon atoms 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.

[0123] Ra 1 and Ra 2 The aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0124] 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 monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0125] The dicarboxylic acid unit (A) preferably contains at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by the following formula (A1), a dicarboxylic acid unit (A2) represented by 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). 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 still more preferably contains the dicarboxylic acid unit (A2).

[0126]

Chemical formula

[0127] In formula (A1), n 101 is an integer of 0 or more and 4 or less, and n 101 pieces of Ra 101 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 101 is preferably 0, 1, or 2, more preferably 0 or 1, and still more preferably 0.

[0128]

Chemical formula

[0129] In formula (A2), n 201 and n 202 are each independently an integer of 0 or more and 4 or less, and n 201 pieces of Ra 201 and n 202 pieces of Ra 202 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 201It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 202 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0130] [ka]

[0131] In equation (A3), n 301 and n 302 Each of these is an independent integer between 0 and 4, and n 301 Individual Ra 301 and n 302 Individual Ra 302 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 301 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 302 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0132] [ka]

[0133] In equation (A4), n 401 n is an integer between 0 and 6, and 401 Individual Ra 401 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 401 It is preferably an integer between 0 and 4, more preferably 0, 1, or 2, and even more preferably 0.

[0134] [ka]

[0135] In equation (A5), n 501 , n 502 and n 503 Each of these is an independent integer between 0 and 4, and n 501 Individual Ra 501 , n 502 Individual Ra 502 and n 503 Individual Ra 503 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 501 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 502 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 503 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0136] Ra in equation (A1) 101 Ra in equation (A2) 201 and Ra 202 Ra of formula (A3) 301 and Ra 302 Ra of formula (A4) 401 Also, Ra in formula (A5) 501 Ra 502 and Ra 503 Since the specific form and preferred form are the same, hereinafter, Ra 101 Ra 201 Ra 202 Ra 301 Ra 302 Ra 401 Ra 501 Ra 502 and Ra 503 We will refer to them collectively as "Ra" and explain them accordingly.

[0137] 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 linear alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups. Examples of branched alkyl groups having 3 to 10 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, and the like. Examples of cyclic alkyl groups having 3 to 10 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl groups, as well as polycyclic alkyl groups (e.g., bicyclic, tricyclic, spirocyclic) formed by linking these monocyclic alkyl groups.

[0138] The aryl group with 6 to 12 carbon atoms related to Ra may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Examples of aryl groups having 6 to 12 carbon atoms include phenyl, biphenyl, 1-naphthyl, and 2-naphthyl groups.

[0139] 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 linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0140] Below are examples of dicarboxylic acid units (A1) (A1-1) to (A1-9). Dicarboxylic acid units (A1) are not limited to these examples.

[0141] [ka]

[0142] Below are examples of dicarboxylic acid units (A2) (A2-1) to (A2-3). Dicarboxylic acid units (A2) are not limited to these examples.

[0143] [ka]

[0144] The following are specific examples of dicarboxylic acid units (A3), namely (A3-1) and (A3-2). However, dicarboxylic acid units (A3) are not limited to these examples.

[0145] [ka]

[0146] Below are examples of dicarboxylic acid units (A4) (A4-1) to (A4-3). Dicarboxylic acid units (A4) are not limited to these examples.

[0147] [ka]

[0148] Below are examples of dicarboxylic acid units (A5), specifically (A5-1) to (A5-4). Dicarboxylic acid units (A5) are not limited to these examples.

[0149] [ka]

[0150] The dicarboxylic acid unit (A) preferably includes at least one selected from the group consisting of (A1-1), (A1-7), (A2-3), (A3-2), and (A4-3) as described above, more preferably includes at least one selected from the group consisting of (A2-3), (A3-2), and (A4-3), and even more preferably includes at least (A2-3).

[0151] The dicarboxylic acid units (A) contained in the polyarylate resin (PA) may be one type or two or more types.

[0152] The mass percentage of dicarboxylic acid units (A) in the polyarylate resin (PA) is preferably 15% by mass or more and 60% by mass or less. When the mass percentage of dicarboxylic acid units (A) is 15% by mass or more, the abrasion resistance of the charge transport layer is good. From this viewpoint, the mass percentage of dicarboxylic acid units (A) is more preferably 20% by mass or more, and even more preferably 25% by mass or more. When the mass percentage of dicarboxylic acid units (A) is 60% by mass or less, peeling of the charge transport layer can be suppressed. From this viewpoint, the mass percentage of dicarboxylic acid units (A) is more preferably 55% by mass or less, and even more preferably 50% by mass or less.

[0153] Polyarylate resin (PA) may contain dicarboxylic acid units other than dicarboxylic acid unit (A). Examples of other dicarboxylic acid units include aliphatic dicarboxylic acid units (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid), alicyclic dicarboxylic acid units (e.g., cyclohexanedicarboxylic acid), and lower alkyl ester units thereof (e.g., having 1 to 5 carbon atoms). The polyarylate resin (PA) may contain one or more of these dicarboxylic acid units.

[0154] The diol unit (B) is a constituent unit represented by the following formula (B).

[0155] [ka]

[0156] In equation (B), Ar B1 and Ar B2 Each of these is an aromatic ring which may independently have substituents, L B is a single bond, oxygen atom, sulfur atom or -C(Rb 1 )(Rb 2 )- and n B1 Rb is 0, 1, or 2. 1 and Rb 2 Each of these is independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 These may be bonded together to form a cyclic alkyl group.

[0157] Ar B1 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0158] Ar B1 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. B1 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0159] Ar B2 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0160] Ar B2 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. B2 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0161] Rb 1 and Rb 2 The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 18, more preferably 1 to 14, and even more preferably 1 to 10.

[0162] Rb 1 and Rb 2 The aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0163] Rb 1 and Rb 2The 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 monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0164] The diol unit (B) preferably includes at least one selected from the group consisting of the diol unit (B1) represented by formula (B1), the diol unit (B2) represented by formula (B2), the diol unit (B3) represented by formula (B3), the diol unit (B4) represented by formula (B4), the diol unit (B5) represented by formula (B5), the diol unit (B6) represented by formula (B6), the diol unit (B7) represented by formula (B7), and the diol unit (B8) represented by formula (B8).

[0165] The diol unit (B) more preferably includes at least one selected from the group consisting of the diol unit (B1) represented by the following formula (B1), the diol unit (B2) represented by the formula (B2), the diol unit (B4) represented by the formula (B4), the diol unit (B5) represented by the formula (B5), and the diol unit (B6) represented by the formula (B6). It is even more preferable to include at least one selected from the group consisting of a diol unit represented by the following formula (B1), a diol unit represented by the following formula (B2), a diol unit represented by the following formula (B5), and a diol unit represented by the following formula (B6): It is even more preferable to include at least one selected from the group consisting of a diol unit represented by the following formula (B1), a diol unit represented by the following formula (B2), and a diol unit represented by the following formula (B6): It is most preferable that the material 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).

[0166] [ka]

[0167] In equation (B1), Rb 101 Rb is a branched alkyl group having 4 to 20 carbon atoms. 201 Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 401 , Rb 501 , Rb 801 and Rb 901 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0168] Rb 101 The number of carbon atoms in the branched alkyl group having 4 to 20 carbon atoms is preferably 4 to 16, more preferably 4 to 12, and even more preferably 4 to 8. 101 Specific examples include isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, isododecyl group, sec-dodecyl group, tert-dodecyl group, tert-tetradecyl group, tert-pentadecyl group, and the like.

[0169] [ka]

[0170] In equation (B2), Rb 102Rb is a linear alkyl group having 4 to 20 carbon atoms. 202 Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 402 , Rb 502 , Rb 802 and Rb 902 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0171] Rb 102 The number of carbon atoms in the linear alkyl group having 4 to 20 carbon atoms is preferably 4 to 16, more preferably 4 to 12, and even more preferably 4 to 8. 102 Specific examples include n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, tridecyl group, n-tetradecyl group, n-pentadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-icosyl group, and the like.

[0172] [ka]

[0173] In equation (B3), Rb 113 and Rb 213 Each of these is 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 between 7 and 15, and Rb 403 , Rb 503 , Rb 803 and Rb 903 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0174] 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 this group 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 the group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy groups. Rb 113 and Rb 213 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0175] [ka]

[0176] In equation (B4), Rb 104 and Rb 204 Each is 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 of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0177] 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. Rb 104 Specific examples include methyl groups, ethyl groups, n-propyl groups, isopropyl groups, and cyclopropyl groups.

[0178] [ka]

[0179] In equation (B5), Ar 105 Rb is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms. 205 Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 405 , Rb 505 , Rb 805 and Rb 905 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0180] Ar 105 The aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Ar 105 The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. 105 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Examples of aralkyl groups having 7 to 20 carbon atoms include benzyl group, phenylethyl group, phenylpropyl group, 4-phenylbutyl group, phenylpentyl group, phenylhexyl group, phenylheptyl group, phenyloctyl group, phenylnonyl group, naphthylmethyl group, naphthylethyl group, anthratilmethyl group, and phenylcyclopentylmethyl group.

[0181] [ka]

[0182] In equation (B6), Rb 116 and Rb 216 Each of these is 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 between 4 and 6, and Rb406 , Rb 506 , Rb 806 and Rb 906 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0183] 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 this group 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 the group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy groups. Rb 116 and Rb 216 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0184] [ka]

[0185] In equation (B7), Rb 407 , Rb 507 , Rb 807 and Rb 907 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0186] [ka]

[0187] In equation (B8), Rb 408 , Rb 508 , Rb 808 and Rb 908 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0188] Rb of equation (B1) 201 Rb of formula (B2) 202 Rb in formula (B4) 204 and Rb of formula (B5) 205 Since the specific form and preferred form are the same, hereinafter referred to as Rb 201 , Rb 202 , Rb 204 and Rb 205 to "Rb 200 They explain it collectively as "[...]."

[0189] Rb 200 The alkyl group having 1 to 3 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 or 2 carbon atoms, and more preferably 1 carbon atom. Examples of alkyl groups having 1 to 3 carbon atoms include methyl, ethyl, n-propyl, isopropyl, and cyclopropyl groups.

[0190] Rb of equation (B1) 401 Rb of formula (B2) 402 Rb of formula (B3) 403 Rb in formula (B4) 404 Rb in formula (B5) 405 Rb in formula (B6) 406 Rb in equation (B7) 407 and Rb of formula (B8) 408 Since the specific form and preferred form are the same, hereinafter referred to as Rb 401 , Rb 402 , Rb 403 , Rb 404 , Rb 405 , Rb 406 , Rb 407 and Rb 408 to "Rb 400 They explain it collectively as "[...]."

[0191] Rb 400 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0192] 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 linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0193] Rb 400 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0194] Rb of equation (B1) 501 Rb of formula (B2) 502Rb of formula (B3) 503 Rb in formula (B4) 504 Rb in formula (B5) 505 Rb in formula (B6) 506 Rb in equation (B7) 507 and Rb of formula (B8) 508 Since the specific form and preferred form are the same, hereinafter referred to as Rb 501 , Rb 502 , Rb 503 , Rb 504 , Rb 505 , Rb 506 , Rb 507 and Rb 508 to "Rb 500 They explain it collectively as "[...]."

[0195] Rb 500 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0196] 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 linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0197] Rb 500 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0198] Rb of equation (B1) 801 Rb of formula (B2) 802 Rb of formula (B3) 803 Rb in formula (B4) 804 Rb in formula (B5) 805 Rb in formula (B6) 806 Rb in equation (B7) 807 and Rb of formula (B8) 808 Since the specific form and preferred form are the same, hereinafter referred to as Rb 801 , Rb 802 , Rb 803 , Rb 804 , Rb 805 , Rb 806 , Rb 807 and Rb 808 to "Rb 800 They explain it collectively as "[...]."

[0199] Rb 800 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0200] 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 linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0201] Rb 800 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0202] Rb of equation (B1) 901 Rb of formula (B2) 902 Rb of formula (B3) 903 Rb in formula (B4) 904 Rb in formula (B5) 905 Rb in formula (B6) 906 Rb in equation (B7) 907 and Rb of formula (B8) 908 Since the specific form and preferred form are the same, hereinafter referred to as Rb 901 , Rb 902 , Rb 903 , Rb 904 , Rb 905 , Rb 906 , Rb907 and Rb 908 to "Rb 900 They explain it collectively as "[...]."

[0203] Rb 900 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0204] 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 linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0205] Rb 900 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0206] The following are specific examples of diol units (B1), specifically (B1-1) to (B1-6). Diol units (B1) are not limited to these examples.

[0207] [ka]

[0208] The following are specific examples of diol units (B2), specifically (B2-1) to (B2-11). Diol units (B2) are not limited to these examples.

[0209] [ka]

[0210] The following are specific examples of diol units (B3), namely (B3-1) to (B3-4). Diol units (B3) are not limited to these examples.

[0211] [ka]

[0212] The following are examples of diol units (B4-1) to (B4-7). Diol units (B4) are not limited to these examples.

[0213] [ka]

[0214] The following are examples of diol units (B5-1) to (B5-6). Diol units (B5) are not limited to these examples.

[0215] [ka]

[0216] The following are specific examples of diol units (B6), namely (B6-1) to (B6-4). Diol units (B6) are not limited to these examples.

[0217] [ka]

[0218] The following are examples of diol units (B7-1) to (B7-3). Diol units (B7) are not limited to these examples.

[0219] [ka]

[0220] The following are specific examples of diol units (B8), namely (B8-1) to (B8-3). Diol units (B8) are not limited to these examples.

[0221] [ka]

[0222] The diol units (B) contained in the polyarylate resin (PA) may be one type or two or more types.

[0223] The mass percentage of diol units (B) in the polyarylate resin (PA) is preferably 25% by mass or more and 80% by mass or less. When the mass percentage of diol units (B) is 25% by mass or more, peeling of the charge transport layer can be suppressed. From this viewpoint, the mass percentage of diol units (B) is more preferably 30% by mass or more, and even more preferably 35% by mass or more. When the mass percentage of diol units (B) is 80% by mass or less, it is possible to maintain solubility in the coating solution for forming the charge transport layer and improve wear resistance. From this viewpoint, the mass percentage of diol units (B) is more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0224] Polyarylate resin (PA) may contain other diol units besides diol unit (B). Examples of other diol units include aliphatic diol units (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) and alicyclic diol units (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A). The polyarylate resin (PA) may contain one or more of these diol units.

[0225] The ends of the polyarylate resin (PA) may be sealed or modified with end-capping agents or molecular weight modifiers used during manufacturing. Examples of end-capping agents or molecular weight modifiers include monohydric phenols, monohydric acid chlorides, monohydric alcohols, and monohydric carboxylic acids. Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m Examples include -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 monovalent acid chlorides include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetate chloride, butyrate chloride, octic acid chloride, benzoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and their substituted derivatives. 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 monocarboxylic acids include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0226] The weight-average molecular weight of the polyarylate resin (PA) is preferably 30,000 to 300,000, more preferably 40,000 to 250,000, and even more preferably 50,000 to 200,000. The molecular weight of polyarylate resin (PA) is the molecular weight in polystyrene equivalent, measured by GPC (gel permeation chromatography). Tetrahydrofuran is used as the eluent in GPC.

[0227] Polyarylate resins (PA) can be obtained by polycondensation of monomers that give dicarboxylic acid units (A) and monomers that give diol units (B), along with other monomers as needed, using conventional methods. Methods for the polycondensation of monomers include interfacial polymerization, solution polymerization, and melt polymerization. Interfacial polymerization is a polymerization method that obtains polyester by mixing a divalent carboxylic acid halide dissolved in an organic solvent immiscible with water with a divalent alcohol dissolved in an alkaline aqueous solution. Literature on interfacial polymerization includes WMERECKSON, J. Poly. Sci., XL399, 1959, and Japanese Patent Publication No. 40-1959. Because interfacial polymerization is faster than solution polymerization, it can suppress the hydrolysis of divalent carboxylic acid halides, resulting in the acquisition of high molecular weight polyarylate resins (PA).

[0228] The proportion of polyarylate resin (PA) in the total binding resin is preferably 20% to 80% by mass, more preferably 25% to 75% by mass, and even more preferably 30% to 70% by mass, relative to the charge transport layer.

[0229] (Other binding resins) The binder resin used in the charge transport layer may be polyarylate resin (PA) or polycarbonate resin. When polyarylate resin (PA) and polycarbonate resin are used together, the ester bonds of polycarbonate have higher symmetry and lower local polarity than the carbonate ester bonds of polyarylate. Therefore, it is preferable because it is presumed that fewer carriers will be trapped in the charge transport layer compared to when polyarylate resin is used alone, thus less likely to hinder charge transfer.

[0230] The proportion of polyarylate resin (PA) in the total amount of polyarylate resin (PA) and polycarbonate resin contained in the charge transport layer 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.

[0231] Polyarylate resins (PA) improve the abrasion resistance of the charge transport layer because the resin molecules are bound together by intermolecular forces through the stacking of aromatic rings. Polycondensates of bisphenols and aromatic divalent carboxylic acids are preferred as the polyarylate resin (PA).

[0232] As the polycarbonate resin, a polycarbonate resin having a continuous structure of aromatic rings is preferred. In this polycarbonate resin, the resin molecules are bound together by intermolecular forces through the stacking of aromatic rings, improving the wear resistance of the charge transport layer. Specifically, a preferred form of the polycarbonate resin is the polycarbonate resin disclosed in Japanese Patent Application Publication No. 2023-121553.

[0233] As for the combination of polyarylate resin (PA) and polycarbonate resin, a combination of resins in which both have structural units containing biphenyl represented by the following formula (BP) is preferred. In other words, it is preferable that the polyarylate resin (PA) and the polycarbonate resin each have structural units containing biphenyl represented by the following formula (BP). The inclusion of biphenyl in both the polyarylate resin (PA) and the polycarbonate resin strengthens the orientation of molecules. As a result, the dielectric constant of the charge transport layer increases, and when the same number of charges are trapped inside, it becomes less likely to appear as a potential change, thus making it easier to suppress potential fluctuations after electrostatic latent image formation. Furthermore, it is presumed that the presence of biphenyl-containing structural units in both materials increases compatibility between polyarylate resin (PA) and polycarbonate resin, reducing charge trapping that originates from the structure of each resin.

[0234] [ka]

[0235] In equation (BP), j is an integer between 0 and 4, and j R 1 Each is independently either a methyl group or an ethyl group, k is an integer between 0 and 4, and there are k R 2 These are independently either a methyl group or an ethyl group.

[0236] The biphenyl represented by formula (BP) may be the entire structure or a part of the structure obtained by removing the ester bond (-C(=O)O-) or carbonate bond (-OC(=O)O-) from the constituent unit containing the biphenyl represented by formula (BP). In other words, the right and left ends of the biphenyl represented by formula (BP) may be independently directly bonded to an ester bond or a carbonate bond, or they may be bonded to an ester bond or a carbonate bond via other atoms or groups of atoms.

[0237] j is an integer between 0 and 4, preferably between 0 and 3, more preferably between 0 and 2, even more preferably 0 or 1, and particularly preferably 0. If j is an integer greater than or equal to 1, then j R 1 Each of these is independently a methyl group or an ethyl group, and a methyl group is preferred.

[0238] k is an integer between 0 and 4, preferably between 0 and 3, more preferably between 0 and 2, even more preferably 0 or 1, and particularly preferably 0. If k is an integer greater than or equal to 1, then k R 2 Each of these is independently a methyl group or an ethyl group, and a methyl group is preferred.

[0239] The biphenyl represented by formula (BP) is preferably 4,4'-biphenyl in terms of its linkage position in the main chain.

[0240] As for the combination of polyarylate resin (PA) and polycarbonate resin, a combination of polyarylate resin (PA) having at least one of dicarboxylic acid units (A2-3) and diol units (B7-1) and polycarbonate resin having constituent units (Cb7-1) is particularly preferred.

[0241] [ka]

[0242] In addition to polyarylate resin (PA) and polycarbonate resin, other binder resins may be used in the charge transport layer, such as 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, and polysilane. However, the proportion of other resins in the binder resin is preferably 10% by mass or less, and more preferably 5% by mass or less.

[0243] The preferred mixing ratio of the charge transport material to the binder resin is between 10:1 and 1:5 by mass.

[0244] (Other additives) The charge transport layer may also contain other known additives. For example, the charge transport layer may contain a phenolic compound.

[0245] Examples of phenol compounds included in the charge transport layer include phenol, cresol, catechol, resorcinol, hydroquinone, naphthol, and bisphenol (bisphenol A, AP, AF, B, BP, C, C2, E, F, G, M, S, P, PH, TMC, Z). One phenol compound may be used alone, or two or more may be used in combination.

[0246] Hindered phenol compounds are also examples of phenol compounds included in the charge transport layer. From the viewpoint of suppressing oxidative degradation of the charge transport layer, it is preferable that the phenol compounds included in the charge transport layer include hindered phenol compounds. Hindered phenol compounds are generally compounds in which at least one of the ortho positions of the hydroxyl group of phenol is substituted with a bulky group, and are known to exhibit an antioxidant effect on the composition.

[0247] Examples of hindered phenol compounds include the following: • Alkylated monophenol compounds and their derivatives: e.g., 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, octyl-3,5-di-t-butyl-4-hydroxyhydrocinnamate • 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 • Alkylidenebisphenol compounds and their derivatives: e.g., 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

[0248] Commercially available hindered phenol compounds include ADEKA Corporation's "ADEKA Stab AO-80," "ADEKA Stab AO-60," "ADEKA Stab AO-50," "ADEKA Stab AO-40," "ADEKA Stab AO-30," "ADEKA Stab AO-20," and "ADEKA Stab AO-330," BASF Japan Ltd.'s "Irganox 1010," "Irganox 245," "Irganox 1076," and "Irganox 1520," and Sumitomo Chemical Co., Ltd.'s "Sumilizer GA-80," "Sumilizer GM," and "Sumilizer GS."

[0249] Hindered phenol compounds may be used individually or in combination of two or more.

[0250] The content of the phenol compound in the charge transport layer is preferably 0.1% to 20% by mass, more preferably 0.5% to 10% by mass, and even more preferably 1% to 5% by mass, based on the total mass of the charge transport layer.

[0251] The charge transport layer preferably contains 5% by mass or less of fluororesin particles, preferably 1% by mass or less, and more preferably 0% by mass (i.e., it does not contain fluororesin particles). Given the high likelihood of increased regulations on the manufacture and use of organofluorine compounds in the future, the above-mentioned range for the content of fluororesin particles is preferable.

[0252] -Relative permittivity of the charge transport layer- The relative permittivity of the charge transport layer is preferably 3.0 to 5.0, more preferably 3.0 to 4.0, and even more preferably 3.1 to 3.3. When the relative permittivity of the charge transport layer is 3.0 or higher, the ratio of the relative permittivity of the charge transport layer to that of the underlying layer falls within a favorable range, making it easier to suppress potential fluctuations after electrostatic latent image formation. If the relative permittivity of the charge transport layer is 5.0 or less, it actually suppresses the ratio of the relative permittivity of the charge transport layer to that of the underlying layer from becoming too large, making it easier to suppress potential fluctuations after electrostatic latent image formation. The relative permittivity of the charge transport layer is increased when it satisfies the above range.

[0253] One way to control the dielectric constant of the charge transport layer within the above range is by controlling it through the structure of the resin used. For example, using resins that contain many aromatic rings in their structure or those with less twisting in their structure tends to increase the dielectric constant because the molecules stack together. Another method is to mix multiple types of resins to obtain an intermediate value between their dielectric constants.

[0254] -Ratio of the relative permittivity of the charge transport layer to the relative permittivity of the underlying layer- The ratio of the relative permittivity of the charge transport layer to the relative permittivity of the underlying layer (relative permittivity of the charge transport layer / relative permittivity of the underlying layer) is preferably 0.010 or more and 0.400 or less, more preferably 0.02 or more and 0.2 or less, and even more preferably 0.03 or more and 0.1 or less. When the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the underlayment layer is 0.01 or higher, the relative permittivity of the underlayment layer relative to the charge transport layer falls within a desirable range, preventing the voltage of the underlayment layer from dropping excessively in order to increase the voltage of the charge transport layer, thus preventing potential fluctuations after electrostatic latent image formation. When the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the underlying layer is 0.40 or less, the relative permittivity of the underlying layer falls within a favorable range, which suppresses a decrease in the voltage applied to the charge transport layer and makes it easier to suppress potential fluctuations after electrostatic latent image formation. When the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the underlying layer satisfies the above range, the dielectric constant of the underlying layer in the photoreceptor increases, and the voltage applied to the charge transport layer increases. As a result, potential fluctuations after electrostatic latent image formation are suppressed.

[0255] The relative permittivity of the charge transport layer and the underlying layer is measured as follows: First, the capacitance (C) of the charge transport layer. CT ) and capacitance of the underlayer (C UC ) is measured and calculated by the following method. A sample of appropriate size (i.e., a sample with a base layer, charge generation layer, and charge transport layer laminated on a conductive substrate) is cut from the photoreceptor to be measured. A 3mm radius Au electrode is formed on the surface of this sample by vacuum deposition as a counter electrode. An impedance analyzer is used to measure the capacitance at an AC frequency of 1Hz while a DC voltage of 10V and an AC voltage of 2V are applied to the base layer from the conductive substrate and the Au electrode. This capacitance is then measured as C. T Let's assume that. Next, the charge transport layer and charge generation layer are removed from the above sample using a solvent, leaving a single layer of undercoat attached to the conductive substrate. In this state, an Au electrode with a radius of 3 mm is formed on the surface of the undercoat, and using an impedance analyzer, a DC voltage of 10 V and an AC voltage of 2 V are applied to the undercoat from the conductive substrate and the Au electrode, and the capacitance of the undercoat is measured at an AC frequency of 1 Hz. The capacitance of this undercoat is then measured as C UC Let's assume that. Capacitance C of the charge transport layer CT is capacitance C T and capacitance C of the lower layer UC Therefore, it can be calculated using the following formula. Formula:C CT =(C T ×C UC ) / (C UC -C T ) Capacitance C of the charge transport layer CT and capacitance C of the lower layer UC From the values, the relative permittivity of the charge transport layer and the lower layer are calculated using the following formulas, with respect to the dielectric constant of vacuum, the area of ​​the Au electrode, and the film thickness of each layer. Formula: Relative permittivity of the target layer = (C / S × d) / ε0 In the formula, C is the capacitance (F) of the target layer, and S is the capacitance (m) of the Au electrode. 2 ), d is the film thickness of the target layer (m), ε0 is the dielectric constant of vacuum (= 8.854 × 10⁻¹⁴). -12 )

[0256] -Film thickness of each layer- The thickness of the undercoat layer is determined by making an incision in the film with a cutter knife or similar tool while the undercoat layer is in a single layer, exposing the conductive substrate, and measuring the depth of the exposed area with a roughness meter. The thickness of the charge transport layer is calculated by making cuts with a utility knife in each layer below the charge transport layer to expose the conductive substrate, measuring the depth of the exposed area with a roughness meter, and subtracting the thickness of the aforementioned undercoat layer from the thickness of each layer below the charge transport layer.

[0257] The formation of the charge transport layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of a charge transport layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0258] Suitable solvents for preparing the coating solution for forming the charge transport layer include common organic solvents such as aromatic hydrocarbons like benzene, toluene, xylene, and chlorobenzene; ketones like acetone and 2-butanone; halogenated aliphatic hydrocarbons like methylene chloride, chloroform, and ethylene chloride; and cyclic or linear ethers like tetrahydrofuran and ethyl ether. These solvents can be used individually or in mixtures of two or more.

[0259] Conventional methods for applying a charge transport layer forming coating solution onto a charge generation layer include blade coating, wire bar coating, spray coating, immersion coating, bead coating, air knife coating, and curtain coating.

[0260] The thickness of the charge transport layer is set, for example, preferably within the range of 5 μm to 50 μm, and more preferably within the range of 10 μm to 30 μm.

[0261] <Image forming apparatus, process cartridge> The image forming apparatus according to this embodiment comprises 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 charged surface of the electrophotographic photoreceptor, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing 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 this embodiment is used as the electrophotographic photoreceptor.

[0262] In the image forming apparatus according to this embodiment, the cleaning apparatus has a cleaning blade that contacts the outer surface of the photoreceptor, and the cleaning blade cleans the surface of the photoreceptor after the toner image has been transferred and before it has been charged.

[0263] The image forming apparatus according to this embodiment includes known image forming apparatuses such as: an apparatus equipped with a fixing device for fixing a toner image transferred to the surface of a recording medium; a direct transfer apparatus for directly transferring a toner image formed on the surface of an electrophotographic photoreceptor to a recording medium; an intermediate transfer apparatus for first transferring a toner image formed on the surface of an electrophotographic photoreceptor to the surface of an intermediate transfer body, and secondarily transferring the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium; an apparatus equipped with a static elimination device for irradiating the surface of the electrophotographic photoreceptor with static elimination light to eliminate static charge after the transfer of the toner image and before charging; and an apparatus equipped with an electrophotographic photoreceptor heating member for raising the temperature of the electrophotographic photoreceptor and reducing the relative temperature.

[0264] In the case of an intermediate transfer method apparatus, the transfer apparatus may be configured to include, for example, an intermediate transfer body on which a toner image is transferred; a primary transfer apparatus that first transfers the toner image formed on the surface of an electrophotographic photoreceptor to the surface of the intermediate transfer body; and a secondary transfer apparatus that secondarily transfers the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium.

[0265] The image forming apparatus according to this embodiment may be either a dry developing type image forming apparatus or a wet developing type image forming apparatus (a developing method using a liquid developer).

[0266] In the image forming apparatus according to this embodiment, for example, the portion comprising the electrophotographic photoreceptor may be a cartridge structure (process cartridge) that can be attached to and detached from the image forming apparatus. As the process cartridge, for example, a process cartridge comprising the electrophotographic photoreceptor according to this embodiment is preferably used. In addition to the electrophotographic photoreceptor, the process cartridge may also include at least one selected from the group consisting of, for example, a charging device, an electrostatic latent image forming device, a developing device, and a transfer device.

[0267] The following is an example of an image forming apparatus according to this embodiment, but it is not limited to this example. The main parts shown in the figure will be described, and the descriptions of other parts will be omitted.

[0268] Figure 2 is a schematic diagram showing an example of an image forming apparatus according to this embodiment. As shown in Figure 2, the image forming apparatus 100 according to this embodiment includes a process cartridge 300 equipped with an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming apparatus), 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 positioned to expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, and the transfer device 40 is positioned opposite the electrophotographic photoreceptor 7 via the intermediate transfer body 50, with a portion of the intermediate transfer body 50 in contact with the electrophotographic photoreceptor 7. Although not shown, the apparatus 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 (primary transfer device), and the secondary transfer device (not shown) are examples of transfer devices.

[0269] In Figure 2, the process cartridge 300 integrally 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) within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is positioned to contact the surface of the electrophotographic photoreceptor 7. The cleaning member may be a conductive or insulating fibrous member, rather than a cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

[0270] Figure 2 shows an example of an image forming apparatus that includes a fibrous member 132 (roll-shaped) for supplying lubricant 14 to the surface of the electrophotographic photoreceptor 7, and a fibrous member 133 (flat brush-shaped) for assisting cleaning. These can be arranged as needed.

[0271] The following describes the various components of the image forming apparatus according to this embodiment.

[0272] -Charging device- The charging device 8 may be a contact-type charging device in which the charging member contacts the outer surface of the photoreceptor, or a non-contact-type charging device in which the charging member does not contact the outer surface of the photoreceptor. The effect of the image forming apparatus according to this embodiment (less likely to cause contamination of the charging member over a long period of time) is particularly pronounced in the contact-type charging device.

[0273] As the charging device 8, for example, contact-type charging members using conductive or semiconductive charging rollers, charging brushes, charging films, charging rubber blades, charging tubes, etc. are used. Non-contact roller chargers, known chargers such as scorotron chargers and corotron chargers that utilize corona discharge are also used.

[0274] -Exposure equipment- Examples of exposure devices 9 include optical equipment that exposes the surface of an electrophotographic photoreceptor 7 to a predetermined image using light such as semiconductor laser light, LED light, or liquid crystal shutter light. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photoreceptor. As for the wavelength of the semiconductor laser, near-infrared lasers with an oscillation wavelength of around 780 nm are the mainstream. However, the wavelength is not limited to this, and lasers with oscillation wavelengths in the 600 nm range or blue lasers with oscillation wavelengths between 400 nm and 450 nm may also be used. Furthermore, for color image formation, surface-emitting laser light sources capable of outputting multiple beams are also effective.

[0275] -Developing equipment- Examples of developing devices 11 include general developing devices that develop by contacting or not contacting the developing agent. There are no particular restrictions on the developing device 11 as long as it has the above-described functions, and it can be selected according to the purpose. For example, known developing devices that have the function of applying a one-component or two-component developing agent to the electrophotographic photoreceptor 7 using a brush, roller, etc. Among these, those that use a developing roller that holds the developing agent on its surface are preferred.

[0276] The developer used in the developing device 11 may be a one-component developer consisting of toner alone, or a two-component developer containing toner and a carrier. Furthermore, the developer may be magnetic or non-magnetic. Known developers can be used.

[0277] -Cleaning device- The cleaning device 13 uses a cleaning blade system equipped with a cleaning blade 131. In addition to the cleaning blade system, a fur brush cleaning system or a developing and cleaning system may also be used.

[0278] -Transfer device- Examples of the transfer device 40 include contact-type transfer chargers using belts, rollers, films, rubber blades, etc., and transfer chargers that are known themselves, such as scorotron transfer chargers and corotron transfer chargers that utilize corona discharge.

[0279] -Intermediate Transcript- As the intermediate transfer body 50, a belt-shaped material (intermediate transfer belt) containing semiconducting polyimide, polyamide-imide, polycarbonate, polyarylate, polyester, rubber, etc. is used. In addition to the belt shape, a drum-shaped intermediate transfer body may also be used.

[0280] Figure 3 is a schematic diagram showing another example of the image forming apparatus according to this embodiment. The image forming apparatus 120 shown in Figure 3 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 photoreceptor 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]

[0281] The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following explanation, unless otherwise specified, "parts" and "%" refer to mass. In the following descriptions, synthesis, processing, and manufacturing were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0282] <Example 1> [Formation of the lower layer] Zinc oxide particles (average particle size 70 nm, specific surface area 15 m²) 2 100 parts of zinc oxide (manufactured by Teika Co., Ltd.) were mixed with 500 parts of toluene and stirred. 1.3 parts of a silane coupling agent (product name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) were added and the mixture was stirred for 2 hours. The toluene was then removed by distillation under reduced pressure, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide particles surface-treated with the silane coupling agent.

[0283] 110 parts of surface-treated zinc oxide particles were mixed with 500 parts of tetrahydrofuran by stirring. A solution of 0.6 parts of the above-mentioned compound (A) dissolved in 50 parts of tetrahydrofuran was added as an electron-accepting compound, and the mixture was stirred at 50°C for 5 hours. The solids were then filtered off by vacuum filtration, and the mixture was dried under reduced pressure at 60°C to obtain zinc oxide particles conferred with the electron-accepting compound.

[0284] 100 parts of a solution prepared by dissolving 60 parts of electron-accepting compound-contained zinc oxide particles, 13.5 parts of a curing agent (blocked isocyanate, trade name: Sumijoule 3175, manufactured by Sumitomo Bayern Urethanes), and 15 parts of butyral resin (trade name: Esrec BM-1, manufactured by Sekisui Chemical Co., Ltd.) in 68 parts of methyl ethyl ketone, were mixed with 5 parts of methyl ethyl ketone and dispersed in a sand mill for 2 hours using 1 mmφ glass beads to obtain a dispersion. To the dispersion, 0.005 parts of dioctyl tin dilaurate as a catalyst and 4 parts of silicone resin particles (trade name: Tospar 145, manufactured by Momentive Performance Materials, Inc.) were added to obtain a coating solution for forming an undercoat. The undercoat coating solution was applied to the outer surface of a conductive substrate by immersion coating and dried and cured at 170°C for 40 minutes to form an undercoat with a film thickness of 23.5 μm.

[0285] [Formation of charge generation layer] A mixture consisting of 15 parts of hydroxygallium phthalocyanine (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in its X-ray diffraction spectrum using Cukα characteristic X-rays), 10 parts of vinyl chloride / vinyl acetate copolymer resin (product name: VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed for 4 hours using glass beads with a diameter of 1 mm in a sand mill. 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 the charge generation layer. The coating solution for forming the charge generation layer was immersed and coated onto the undercoat, and dried at room temperature (25℃±3℃) to form a charge generation layer with a thickness of 0.18 μm.

[0286] [Formation of charge transport layer] A coating solution for forming a charge transport layer was obtained by dissolving 35 parts of the following polyarylate resin (PA1) and 24 parts of the following polycarbonate resin (PC1) as binder resins, and 28.7 parts of CTM-1 and 12.3 parts of CTM-2 as charge transport materials, in 270 parts of tetrahydrofuran and 30 parts of toluene. The coating solution for forming a charge transport layer was applied to a charge generating layer by immersion, and dried at 143°C for 30 minutes to form a charge transport layer with a thickness of 32 μm.

[0287] [ka] JPEG2026084601000042.jpg33124 The numbers accompanying the constituent units represent the molar ratio.

[0288] [ka]

[0289] [ka]

[0290] A photoreceptor was obtained through the above process.

[0291] <Example 2> A photoreceptor was obtained in the same manner as in Example 1, except that the charge transport layer was made using 41.0 parts of CTM-1 alone as the charge transport material.

[0292] <Example 3> A photoreceptor was obtained in the same manner as in Example 1, except that the mass% of the electron-accepting compound-contained zinc oxide particles was changed to 62% by mass in the formation of the undercoat layer.

[0293] <Example 4> A photoreceptor was obtained in the same manner as in Example 1, except that the mass percentage of electron-accepting compound-contained zinc oxide particles was changed to 72% by mass in the formation of the undercoat layer.

[0294] <Example 5> In forming the charge transport layer, a photoreceptor was obtained in the same manner as in Example 1, except that the ratio of the binder resin in the charge transport layer was changed to 17.7 parts of polyarylate resin and 41.3 parts of polycarbonate resin, and the charge transport material was changed to 44 parts of CTM-1 alone.

[0295] <Example 6> In forming the charge transport layer, a photoreceptor was obtained in the same manner as in Example 1, except that the binder resin of the charge transport layer was changed to 59.0 parts of polyarylate resin alone, and the charge transport material consisted of 26.4 parts of CTM-1 and 11.3 parts of CTM-2.

[0296] <Example 7> A photoreceptor was obtained in the same manner as in Example 1, except that the binder resin of the charge transport layer was changed to 59.0 parts of a polyarylate resin (PA2) containing 50 mol% dicarboxylic acid units and 50 mol% diol units (B4-3).

[0297] <Examples 8 and 9> A photoreceptor was obtained in the same manner as in Example 1, except that the electron-accepting compound was changed to one of the compounds listed in Table 1 during the formation of the undercoat layer.

[0298] <Example 10> A photoreceptor was obtained in the same manner as in Example 1, except that in the formation of the undercoat layer, the mass percentage of electron-accepting compound-containing zinc oxide particles in the undercoat layer was changed to 75% by mass, and in the formation of the charge transport layer, the ratio of the binder resin in the charge transport layer was changed to 17.7 parts of polyarylate resin and 41.3 parts of polycarbonate resin, and the charge transport material was changed to 44 parts of CTM-1 alone.

[0299] <Examples 11-14> A photoreceptor was obtained in the same manner as in Example 1, except that the film thickness of the undercoat layer was changed as shown in Table 1 during the formation of the undercoat layer.

[0300] <Example 15> A photoreceptor was obtained in the same manner as in Example 1, except that the polycarbonate resin of the charge transport layer was changed to the polycarbonate resin (PC3) shown below.

[0301] [ka]

[0302] <Example 16> In forming the charge transport layer, a photoreceptor was obtained in the same manner as in Example 1, except that the polyarylate resin in the charge transport layer was changed to a polyarylate resin (PA3) composed of dicarboxylic acid units of (A3-2) 40 mol% and (A4-3) 10 mol% and diol units of (B6-4) 50 mol%, and the polycarbonate resin was changed to the above-mentioned polycarbonate resin (PC3).

[0303] <Example 17> In forming the charge transport layer, a photoreceptor was obtained in the same manner as in Example 1, except that the polyarylate resin in the charge transport layer was changed to a polyarylate resin (PA4) composed of 50 mol% dicarboxylic acid units (A3-2) and 50 mol% diol units (B4-4), and the polycarbonate resin was changed to the above-mentioned polycarbonate resin (PC3).

[0304] <Comparative Examples 1 and 4> A photoreceptor was obtained in the same manner as in Example 1, except that the electron-accepting compound was changed to one of the compounds listed in Table 1 during the formation of the undercoat layer.

[0305] <Comparative Example 2> A photoreceptor was obtained in the same manner as in Example 1, except that the mass percentage of electron-accepting compound-contained zinc oxide particles was changed to 76% in the formation of the undercoat layer.

[0306] <Comparative Example 3> A photoreceptor was obtained in the same manner as in Example 1, except that the binder resin for the charge transport layer was changed to 59 parts of polycarbonate resin (PC1) alone in the formation of the charge transport layer.

[0307] <Comparative Example 5> A photoreceptor was obtained in the same manner as in Example 1, except that in the formation of the undercoat layer, the mass percentage of electron-accepting compound-containing zinc oxide particles included in the undercoat layer was changed to 77%, and in the formation of the charge transport layer, the ratio of the binder resin in the charge transport layer was changed to 17.7 parts of polyarylate resin and 41.3 parts of polycarbonate resin.

[0308] <Comparative Example 6> A photoreceptor was obtained in the same manner as in Example 1, except that in the formation of the undercoat layer, the mass % of electron-accepting compound-containing zinc oxide particles included in the undercoat layer was changed to 61%, and in the formation of the charge transport layer, the binder resin of the charge transport layer was changed to 59 parts of polyarylate resin (PA1) alone, and the charge transport material consisted of 26.4 parts of CTM-1 and 11.3 parts of CTM-2.

[0309] <Various Measurements> The following items were measured according to the description method. • Capacitance of the lower layer • Ratio of the relative permittivity of the charge transport layer to the relative permittivity of the lower layer Note that in the table, the notation "(Value A)E-(Value B)" means (Value A) × 10 -(数値B) This shows the value.

[0310] <Evaluation of photoreceptor performance> [Electrical potential fluctuations] The potential fluctuations of the photoreceptor after electrostatic latent image formation were evaluated for each example as follows. The photoreceptor was mounted in an image forming machine (a modified Apeos C7070 manufactured by Fujifilm Business Innovation Co., Ltd.), a potential estimation probe was attached to the developer position, and under conditions of process speed: 350 nm / sec, temperature: 30°C, humidity: 75%, it was charged to 700 V, and then 4 mJm -2 The potential fluctuations observed when the exposure sequence was repeated 6400 times were classified as follows. A: Less than 15V B: 15V or higher, less than 17.5V C: 17.5V or higher, less than 20V D: 20V or higher, less than 22.5V E: 22.5V or higher, less than 25V F: 25V or higher, less than 27.5V

[0311] [Table 1]

[0312] From the above results, the photoreceptor of the example exhibits suppressed potential fluctuations after electrostatic latent image formation compared to the photoreceptor of the comparative example.

[0313] This embodiment includes the following aspects. (((1))) The device comprises a conductive substrate, an undercoat layer disposed on the conductive substrate, and a laminated photosensitive layer disposed on the undercoat layer having a charge generation layer and a charge transport layer, wherein the charge transport layer contains a charge transport material and a polyarylate resin, the polyarylate resin contains dicarboxylic acid units represented by the following formula (A) and diol units represented by the following formula (B), and the capacitance of the undercoat layer is 1.0 × 10⁻⁶ -10 F or higher 3.0×10 -9 Electrophotographic photoreceptor with an F value of 0 or less. [ka] In equation (A), Ar A1 and Ar A2 Each of these is an aromatic ring which may independently have substituents, L A is a single bond or a divalent linking group, n A1 It is 0, 1, or 2. In equation (B), Ar B1 and Ar B2 Each of these is an aromatic ring which may independently have substituents, L B is a single bond, oxygen atom, sulfur atom or -C(Rb 1 )(Rb 2 )- and n B1 Rb is 0, 1, or 2. 1 and Rb 2Each of these is independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 These may be bonded together to form a cyclic alkyl group. (((2))) The electrophotographic photoreceptor according to (((1))), wherein the relative permittivity of the charge transport layer is 3.0 or more and 5.0 or less. (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), wherein the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat layer (relative permittivity of the charge transport layer / relative permittivity of the undercoat layer) is 0.010 or more and 0.400 or less. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the undercoat contains zinc oxide particles to which an electron-accepting compound has been attached in an amount of 62% by mass or more and 75% by mass or less relative to the undercoat. (((5))) The electrophotographic photoreceptor according to ((4))) wherein the electron-accepting compound is an anthraquinone derivative having three OH groups or two OH groups and one alkoxy group. (((6))) The electrophotographic photoreceptor according to (((5))), wherein the anthraquinone derivative is an alizarin derivative represented by formula (C). [ka] In formula (C), R represents a hydroxyl group or an alkoxy group having 1 to 10 carbon atoms. (((7))) The electrophotographic photoreceptor according to any one of (((1))) to (((6))), wherein the thickness of the undercoat layer is 17 μm or more and 35 μm or less. (((8))) The electrophotographic photoreceptor according to any one of (((1))) to (((7))), wherein the polyarylate resin and the polycarbonate resin each have a constituent unit containing biphenyl represented by the following formula (BP). [ka] In equation (BP), j is an integer between 0 and 4, and j R 1 Each is independently either a methyl group or an ethyl group, k is an integer between 0 and 4, and there are k R 2 These are independently either a methyl group or an ethyl group. (((9))) A process cartridge for attaching to and detaching from an image forming apparatus, comprising an electrophotographic photoreceptor as described in any one of (((1))) to (((8))). (((10))) An image forming apparatus comprising: an electrophotographic photoreceptor as described in any one of (((1))) to (((8))); a charging means for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming means for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing means for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image; and a transfer means for transferring the toner image to the surface of a recording medium.

[0314] The effects of the above embodiment are as follows: According to the invention of (((1))), the invention comprises a conductive substrate, an undercoat layer disposed on the conductive substrate, and a laminated photosensitive layer disposed on the undercoat layer having a charge generating layer and a charge transport layer, wherein the charge transport layer contains a charge transport material and a polyarylate resin, the polyarylate resin contains dicarboxylic acid units represented by the following formula (A) and diol units represented by the following formula (B), and the capacitance of the undercoat layer is 1.0 × 10 -10 Less than F, or 3.0 × 10 -9 Compared to cases where the F value exceeds a certain threshold, an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed. According to the invention of (((2))), an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases where the relative permittivity of the charge transport layer is less than 3.0 or greater than 5.0. According to the invention of (((3))), an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases where the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the underlayment (relative permittivity of the charge transport layer / relative permittivity of the underlayment) is less than 0.010 or greater than 0.400. According to the invention of (((4))), an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to the case in which the undercoat contains zinc oxide particles to which an electron-accepting compound is applied in an amount of less than 62% by mass or more than 75% by mass. According to the invention of (((5))), an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases where the electron-accepting compound is an anthraquinone derivative that does not have three OH groups or has two OH groups and one alkoxy group. According to the invention of (((6))), an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to the case in which the anthraquinone derivative is an alizarin derivative that does not satisfy the configuration represented by formula (C). According to the invention of (((7))), an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases where the film thickness of the undercoat is less than 17 μm or more than 35 μm. According to the invention of (((8))), an electrophotographic photoreceptor is provided in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases in which the polyarylate resin and polycarbonate resin each do not have a constituent unit containing biphenyl. According to the invention of (((9))) or (((10))), the invention comprises a conductive substrate, an undercoat layer disposed on the conductive substrate, and a laminated photosensitive layer disposed on the undercoat layer having a charge generating layer and a charge transport layer, wherein the charge transport layer contains a charge transport material and a polyarylate resin, the polyarylate resin contains dicarboxylic acid units represented by the following formula (A) and diol units represented by the following formula (B), and the capacitance of the undercoat layer is 1.0 × 10 -10 Less than F, or 3.0 × 10 -9 A process cartridge or image forming apparatus is provided that includes an electrophotographic photoreceptor in which potential fluctuations after electrostatic latent image formation are suppressed compared to cases where the potential f-value exceeds F. [Explanation of Symbols]

[0315] 1 conductive substrate, 2 subbing layer, 3 charge generation layer, 4 charge transport layer, 5 photosensitive layer, 10A photoreceptor

[0316] 7 Electrophotographic photoreceptor, 8 Charging device, 9 Exposure device, 11 Developing device, 13 Cleaning device, 14 Lubricant, 40 Transfer device, 50 Intermediate transfer body, 100 Image forming device, 120 Image forming device, 131 Cleaning blade, 132 Fibrous material (roll type), 133 Fibrous material (flat brush type), 300 Process cartridge

Claims

1. A conductive substrate, A base layer disposed on the conductive substrate, A stacked photosensitive layer having a charge generation layer and a charge transport layer is disposed on the aforementioned underlayer, Equipped with, The charge transport layer contains a charge transport material and a polyarylate resin. The polyarylate resin comprises a dicarboxylic acid unit represented by the following formula (A) and a diol unit represented by the following formula (B). The capacitance of the aforementioned lower layer is 1.0 × 10 -１０ F or higher 3.0×10 -９ An electrophotographic photoreceptor with an F rating of 0. 【Chemistry 1】 In equation (A), Ar Ａ１ and Ar Ａ２ Each of these is an aromatic ring which may independently have substituents, L Ａ is a single bond or a divalent linking group, n Ａ１ It is 0, 1, or 2. In formula (B), Ar Ｂ１ and Ar Ｂ２ are each independently 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. Rb １ and Rb ２ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb １ and Rb ２ , together with the ２ may combine to form a cyclic alkyl group.

2. The electrophotographic photoreceptor according to claim 1, wherein the relative permittivity of the charge transport layer is 3.0 or more and 5.0 or less.

3. The electrophotographic photoreceptor according to claim 2, wherein the ratio of the relative permittivity of the charge transport layer to the relative permittivity of the undercoat layer (relative permittivity of the charge transport layer / relative permittivity of the undercoat layer) is 0.010 or more and 0.400 or less.

4. The electrophotographic photoreceptor according to claim 1, wherein the undercoat contains zinc oxide particles to which an electron-accepting compound has been attached in an amount of 62% by mass or more and 75% by mass or less relative to the undercoat.

5. The electrophotographic photoreceptor according to claim 4, wherein the electron-accepting compound is an anthraquinone derivative having three OH groups or two OH groups and one alkoxy group.

6. The electrophotographic photoreceptor according to claim 5, wherein the anthraquinone derivative is an alizarin derivative represented by formula (C). 【Chemistry 2】 In formula (C), R represents a hydroxyl group or an alkoxy group having 1 to 10 carbon atoms.

7. The electrophotographic photoreceptor according to claim 1, wherein the thickness of the undercoat is 17 μm or more and 35 μm or less.

8. The charge transport layer further comprises a polycarbonate resin, The electrophotographic photoreceptor according to claim 1, wherein the polyarylate resin and the polycarbonate resin each have a structural unit containing biphenyl represented by the following formula (BP). 【Transformation 3】 In equation (BP), j is an integer between 0 and 4, and j R １ Each is independently either a methyl group or an ethyl group, k is an integer between 0 and 4, and there are k R ２ These are independently either a methyl group or an ethyl group.

9. The electrophotographic photoreceptor is provided according to any one of claims 1 to 8, A process cartridge that is attached to and detached from an image forming apparatus.

10. An electrophotographic photoreceptor according to any one of claims 1 to 8, A charging means for charging the surface of the electrophotographic photoreceptor, An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, A developing means that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, The system includes a transfer means for transferring the toner image onto the surface of a recording medium. Image forming apparatus.

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