Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor which is less susceptible to burn-in ghost images and prevents adhesion of toner onto a surface thereof.SOLUTION: An electrophotographic photoreceptor is provided, comprising a conductive base material and a laminated photosensitive layer having a charge generation layer and charge transport layer, or a single-layered photosensitive layer. The charge transport layer or the single-layered photosensitive layer constitutes an outermost layer and contains a charge transport material, a polyester resin having a dicarboxylic acid unit (A) represented by formula (A), and a compound with a molecular weight of 255 or greater having a phenol skeleton having a primary carbon atom or secondary carbon atom bonded to one of ortho positions and a tertiary carbon atom or quaternary carbon atom bonded to the other, and having no linear alkylene structure with four or more carbon atoms. In the formula (A), ArA1 and ArA2 independently represent an aromatic ring that may have a substituent, LA represents a single bond or divalent linking group, and nA1 represents 0, 1 or 2.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an electrophotographic photoreceptor obtained using a coating solution for a charge transport layer containing, in a specific ratio, at least one selected from the group consisting of a charge transport material, polycarbonate resin and polyester resin, at least one selected from the group consisting of xylene and toluene, cyclopentanone, and an antioxidant. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-164241 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present disclosure aims to provide an electrophotographic photoreceptor that comprises a conductive substrate and a multilayer photosensitive layer or a single-layer photosensitive layer, wherein the charge transport layer of the multilayer photosensitive layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having dicarboxylic acid units (A), and a compound, and the compound has a molecular weight of less than 260, and has a phenol skeleton in which a hydrogen atom, a tertiary carbon atom, or a quaternary carbon atom is bonded to one ortho position and a tertiary carbon atom or a quaternary carbon atom is bonded to the other, or has a linear alkylene structure with 4 or more carbon atoms, in which burn-in ghosting is less likely to occur and toner adhesion to the electrophotographic photoreceptor surface is suppressed. [Means for solving the problem]

[0005] The following embodiments are included as specific means for solving the aforementioned problems.

[0006] <1> A conductive substrate, A photosensitive layer disposed on the conductive substrate, comprising a multilayer type photosensitive layer having a charge generation layer and a charge transport layer, or a single-layer type photosensitive layer, Equipped with, The charge transport layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having a dicarboxylic acid unit (A) represented by the following formula (A), and a compound having a molecular weight of 255 or more, having a phenol skeleton in which a primary or secondary carbon atom is bonded to one ortho position and a tertiary or quaternary carbon atom is bonded to the other, and not having a linear alkylene structure with 4 or more carbon atoms. Electrophotographic photoreceptor.

[0007] [ka]

[0008] 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. <2> The aforementioned compound has two or more of the phenol skeletons in one molecule. <1> The electrophotographic photoreceptor described above. <3> The two or more phenol skeletons have at least one of the following structures: one in which the ortho position of the first phenol skeleton and the ortho position of the second phenol skeleton are bonded via an alkylene group having 1 to 3 carbon atoms, and another in which the para position of the first phenol skeleton and the para position of the second phenol skeleton are bonded via a divalent linking group. <2> The electrophotographic photoreceptor described above. <4> The content of the compound is 0.4% by mass or more and 10.0% by mass or less of the entire charge transport layer or the single-layer photosensitive layer. <1> ~ <3> An electrophotographic photoreceptor as described in any one of the following. <5> The electrophotographic photoreceptor according to any one of <1> to <4>, wherein an amount of phenolic hydroxyl groups contained in the compound contained in the entire charge transport layer or the entire single-layer type photosensitive layer is 5 mol% or more and 50 mol% or less relative to the number of moles of the charge transport material. <6> The electrophotographic photoreceptor according to any one of <1> to <5>, wherein the dicarboxylic acid unit (A) represented by formula (A) includes at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by formula (A1) below, a dicarboxylic acid unit (A2) represented by formula (A2) below, a dicarboxylic acid unit (A3) represented by formula (A3) below, a dicarboxylic acid unit (A4) represented by formula (A4) below and a dicarboxylic acid unit (A5) represented by formula (A5) below.

[0009]

Chemical Formula

[0010]

Chemical Formula

[0011] In formula (A1), n 101 is an integer of 0 or more and 4 or less, and n 101 Ra groups 101 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A2), n 201 and n 202 are each independently an integer of 0 or more and 4 or less, and n 201 Ra groups 201 and n 202 Ra groups 202 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A3), n 301 and n 302 are each independently an integer of 0 or more and 4 or less, and n 301Individual 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. 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. 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. <7> The polyester resin further comprises a diol unit (B) represented by the following formula (B): <1> ~ <6> An electrophotographic photoreceptor as described in any one of the following.

[0012] [ka]

[0013] 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. <8> The diol unit (B) represented by formula (B) 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). <7> The electrophotographic photoreceptor described above.

[0014] [ka]

[0015] [ka]

[0016] 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. In equation (B2), Rb 102 Rb 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 Rb902 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. 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. 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. 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. 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 Rb 406 , Rb 506 , Rb 806 and Rb 906each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B7), Rb 407 , Rb 507 , Rb 807 and Rb 907 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B8), Rb 408 , Rb 508 , Rb 808 and Rb 908 each independently represent 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.

[0017] <9> The electrophotographic photoreceptor according to any one of <1> to <8>, wherein the charge transport material comprises at least one selected from the group consisting of a compound (D1) represented by formula (D1) below, a compound (D2) represented by formula (D2) below, a compound (D3) represented by formula (D3) below, and a compound (D4) represented by formula (D4) below.

[0018] Chemical formula

[0019] In formula (D1), Ar T1 , Ar T2 and Ar T3 each independently represent an aryl group, -C6H4-C(R T4 )=C(R T5 )(R T6 ), or -C6H4-CH=CH-CH=C(R T7 )(R T8 ). R T4 , R T5 , R T6 , R T7 and R T8 each independently represent a hydrogen atom, an alkyl group, or an aryl group. R T5 and R T6When it is an aryl group, the aryl groups are -C(R 51 )(R 52 )- and -C(R 61 )=C(R 62 )- may be linked by at least one divalent group selected from the group consisting of 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. In equation (D2), R T201 , R T202 , R T211 and R T212 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 T21 )=C(R T22 )(R T23 ) or -CH=CH-CH=C(R T24 )(R T25 ) is R T21 , R T22 , R T23 , R T24 and R T25 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T221 and R T222 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. Tm1, Tm2, ​​Tn1, and Tn2 are each independently 0, 1, or 2. In equation (D3), R T301 , R T302 , R T311 and R T312 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 T31 )=C(R T32 )(R T33 ) or -CH=CH-CH=C(R T34 )(R T35 ) is R T31 , R T32 , RT33 , R T34 and R T35 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T321 , R T322 and R T331 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. To1, To2, Tp1, Tp2, Tq1, Tq2, and Tr1 are each independently 0, 1, or 2. In equation (D4), 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.

[0020] <10> <1> ~ <9> It comprises an electrophotographic photoreceptor as described in any one of the following: A process cartridge that is attached to and detached from an image forming apparatus. <11> The cleaning device further comprises a cleaning blade that contacts the surface of the electrophotographic photoreceptor and cleans the surface of the electrophotographic photoreceptor. <10> Process cartridge as described above. <12> <1> ~ <9> An electrophotographic photoreceptor as described in any one of the following, A charging device for charging the surface of the electrophotographic photoreceptor, An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, A developing apparatus that develops an electrostatic latent image formed on the surface of an electrophotographic photoreceptor using a developer containing toner to form a toner image, A transfer device for transferring the toner image onto the surface of a recording medium, An image forming apparatus equipped with the following features. <13> The cleaning device further comprises a cleaning blade that contacts the surface of the electrophotographic photoreceptor and cleans the surface of the electrophotographic photoreceptor. <12> The image forming apparatus described above. [Effects of the Invention]

[0021] <1> , <6> , <7> , <8> or <9> According to the present invention, an electrophotographic photoreceptor is provided that comprises a conductive substrate and a laminated photosensitive layer or a single-layer photosensitive layer, wherein the charge transport layer of the laminated photosensitive layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having dicarboxylic acid units (A), and a compound, and the compound has a molecular weight of less than 260. Compared to cases where the phenol skeleton has a hydrogen atom, a tertiary carbon atom, or a quaternary carbon atom bonded to one ortho position and a tertiary carbon atom or a quaternary carbon atom bonded to the other, or where the linear alkylene structure has 4 or more carbon atoms, the electrophotographic photoreceptor is less prone to burn-in ghosting and the adhesion of toner to the surface of the electrophotographic photoreceptor is suppressed. <2> or <3> According to the invention, an electrophotographic photoreceptor is provided that is less prone to burn-in ghosting compared to the case where the compound has only one phenol skeleton in one molecule. <4> According to the invention, an electrophotographic photoreceptor is provided that is less prone to burn-in ghosting compared to a case where the compound content is less than 0.4% by mass relative to the entire charge transport layer or single-layer photosensitive layer. <5> According to the invention, an electrophotographic photoreceptor is provided that is less prone to burn-in ghosting compared to a case where the amount of phenolic hydroxyl groups in the compound contained in the entire charge transport layer or single-layer photosensitive layer is less than 5 mol% of the moles of the charge transport material. <10> or <11> According to the present invention, a process cartridge is provided that provides an electrophotographic photoreceptor that is less prone to burn-in ghosting and suppresses toner adhesion to the surface of the electrophotographic photoreceptor compared to the case in which an electrophotographic photoreceptor is used, which comprises a conductive substrate and a multilayer photosensitive layer or a single-layer photosensitive layer, wherein the charge transport layer of the multilayer photosensitive layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having dicarboxylic acid units (A), and a compound, wherein the compound has a molecular weight of less than 260, an electrophotographic photoreceptor having a phenol skeleton in which a hydrogen atom, a tertiary carbon atom, or a quaternary carbon atom is bonded to one ortho position and a tertiary carbon atom or a quaternary carbon atom is bonded to the other, or an electrophotographic photoreceptor having a linear alkylene structure with 4 or more carbon atoms. <12> or <13> According to the present invention, an image forming apparatus is provided that provides an electrophotographic photoreceptor that is less prone to burn-in ghosting and suppresses toner adhesion to the surface of the electrophotographic photoreceptor, compared to the use of an electrophotographic photoreceptor that comprises a conductive substrate and a laminated photosensitive layer or a single-layer photosensitive layer, wherein the charge transport layer of the laminated photosensitive layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having dicarboxylic acid units (A), and a compound, wherein the compound has a molecular weight of less than 260, an electrophotographic photoreceptor having a phenol skeleton in which a hydrogen atom, a tertiary carbon atom, or a quaternary carbon atom is bonded to one ortho position and a tertiary carbon atom or a quaternary carbon atom is bonded to the other, or an electrophotographic photoreceptor having a linear alkylene structure with 4 or more carbon atoms. [Brief explanation of the drawing]

[0022] [Figure 1] This is a partial cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to the first embodiment. [Figure 2] This is a partial cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to the second embodiment. [Figure 3] This is a schematic diagram showing an example of an image forming apparatus according to this embodiment. [Figure 4] This is a schematic diagram showing another example of the image forming apparatus according to this embodiment. [Modes for carrying out the invention]

[0023] The embodiments of this disclosure are described below. These descriptions and embodiments are illustrative and do not limit the scope of the embodiments.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] In this disclosure, alkyl groups include linear, branched, and cyclic alkyl groups unless otherwise specified.

[0029] 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.

[0030] <Electrophotographic photoconductor> This disclosure provides a first embodiment and a second embodiment of an electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor").

[0031] The photoreceptor according to the first embodiment comprises a conductive substrate and a laminated photoreceptor having a charge generation layer and a charge transport layer disposed on the conductive substrate. The photoreceptor according to the first embodiment may further comprise other layers (e.g., an undercoat layer, an intermediate layer). However, in the photoreceptor according to the first embodiment, the charge transport layer is the outermost layer.

[0032] The photoreceptor according to the second embodiment comprises a conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate. The photoreceptor according to the second embodiment may further comprise other layers (e.g., an undercoat layer, an intermediate layer). However, in the photoreceptor according to the second embodiment, the single-layer photosensitive layer is the outermost layer. Hereinafter, the multilayer photosensitive layer will also be referred to as the "multilayer photosensitive layer," and the single-layer photosensitive layer will also be referred to as the "single-layer photosensitive layer."

[0033] Figure 1 is a schematic partial cross-sectional view showing an example of the layer configuration of a photoreceptor according to the first 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.

[0034] Figure 2 is a schematic partial cross-sectional view showing an example of the layer configuration of a photoreceptor according to the second embodiment. The photoreceptor 10B shown in Figure 2 has a single-layer photosensitive layer. The photoreceptor 10B has a structure in which an undercoat layer 2 and a photosensitive layer 5 are stacked in that order on a conductive substrate 1. The photoreceptor 10B may have an intermediate layer (not shown) between the undercoat layer 2 and the photosensitive layer 5.

[0035] The photoreceptor according to the first embodiment has a charge transport layer which is the outermost layer and contains a charge transport material, a polyester resin having a dicarboxylic acid unit (A) represented by the following formula (A), and a compound having a molecular weight of 255 or more, having a phenol skeleton in which a primary or secondary carbon atom is bonded to one ortho position and a tertiary or quaternary carbon atom is bonded to the other, and not having a linear alkylene structure with 4 or more carbon atoms.

[0036] The photoreceptor according to the second embodiment has a single-layer photoreceptor layer which is the outermost layer and contains a charge transport material, a polyester resin having a dicarboxylic acid unit (A) represented by the following formula (A), and a compound having a molecular weight of 255 or more, having a phenol skeleton in which a primary or secondary carbon atom is bonded to one ortho position and a tertiary or quaternary carbon atom is bonded to the other, and not having a linear alkylene structure with 4 or more carbon atoms.

[0037] [ka]

[0038] In equation (A), Ar A1 and ArA2 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.

[0039] Hereinafter, when describing matters common to the first and second embodiments, both embodiments will be collectively referred to as "this embodiment." When describing matters common to the charge transport layer and the single-layer photosensitive layer, both layers will be collectively referred to as the photosensitive layer. Furthermore, a phenol skeleton having a phenolic hydroxyl group, in which a primary or secondary carbon atom is bonded to one ortho position relative to the bonded position of the phenolic hydroxyl group and a tertiary or quaternary carbon atom is bonded to the other, is also called a "hindered phenol skeleton," and a structure having a molecular weight of 255 or more, possessing a hindered phenol skeleton, and not having a linear alkylene structure with 4 or more carbon atoms is also called a "specific hindered phenol structure."

[0040] The photoreceptor according to this embodiment, with the above configuration, is less prone to burn-in ghosting and suppresses toner adhesion to the surface of the photoreceptor. The reason for this is presumed to be as follows.

[0041] In a photosensitive layer containing a polyester resin having dicarboxylic acid units (A), the aromatic rings of the polyester resin interact with each other, causing molecules to attract each other and making it easier to obtain abrasion resistance. On the other hand, the structure in the dicarboxylic acid unit (A), in which the aromatic ring and carbonyl group are directly linked, has electron-withdrawing properties and tends to carry a negative charge, making it easy to capture positive charges through interaction with charge transport materials. In a photosensitive layer containing a polyester resin with dicarboxylic acid units (A), the captured positive charges tend to remain as cation radicals, and repeated image formation causes cation radicals to accumulate in areas of the photosensitive layer that have a particularly high exposure history. When cation radicals accumulate in a specific area, the negative charge from the charging in the next cycle is canceled out in that area, lowering the surface potential and causing burn-in ghosting. Here, "burn-in ghosting" is an image defect in which the surface potential of the part of the photoreceptor that has a high exposure history decreases, and the density of the halftone image becomes darker.

[0042] One method to suppress the occurrence of burn-in ghosting is to include an antioxidant in the photosensitive layer. It is thought that the accumulation of cation radicals in the photosensitive layer is suppressed because the antioxidant captures and eliminates the cation radicals, thereby preventing the occurrence of burn-in ghosting. However, when an antioxidant is included in the photosensitive layer, toner may adhere to the surface of the photoreceptor (hereinafter also referred to as "filming"). In particular, in image forming apparatuses that clean the surface of the photoreceptor with a cleaning blade, toner adhering to the surface of the photoreceptor is easily crushed and stretched by the cleaning blade, making it more likely for filming to occur. The above-mentioned filming is more likely to occur when antioxidants with small molecular weights or those with flexible chemical structures are used. For example, when the molecular weight of the antioxidant is small, it is thought that the antioxidant seeps out onto the surface of the photosensitive layer as the photoreceptor is used, and the surface of the photosensitive layer becomes plasticized by the antioxidant seeping out onto the surface, making it easier for toner and other materials to adhere, thus increasing the likelihood of filming. Also, for example, when the antioxidant has a flexible chemical structure, it is thought that the flexible chemical structure causes microscopic phase separation of the photosensitive layer, forming highly viscous regions, making it easier for toner and other materials to adhere to these highly viscous regions, thus increasing the likelihood of filming. Furthermore, in image forming apparatuses that clean the surface of the photoreceptor with a cleaning blade, it is also conceivable that filming may become even more likely due to the plasticization of the cleaning blade by the antioxidant seeping out onto the surface.

[0043] In contrast, this embodiment uses a compound having a specific hindered phenol structure (also referred to as the "specific compound"). Compounds having a specific hindered phenol structure have a molecular weight of 255 or more and do not have a linear alkylene structure with 4 or more carbon atoms, which is a flexible chemical structure. Therefore, in this embodiment, it is presumed that filming is suppressed compared to when a compound with a molecular weight of less than 255 is used, or when a compound having a linear alkylene structure with 4 or more carbon atoms is used. In addition, compounds having a specific hindered phenol structure have a hindered phenol skeleton, and therefore their ability to capture cation radicals is not excessively high compared to compounds with a phenol skeleton in which a hydrogen atom is bonded to one of the ortho positions. If the ability to capture cation radicals is too high, the compound itself will deactivate quickly, which can lead to cation radicals remaining in the photosensitive layer and making it easier for burn-in ghosting to occur. Therefore, in this embodiment, it is considered that the occurrence of burn-in ghosting is suppressed compared to when a compound having a phenol skeleton in which a hydrogen atom is bonded to one of the ortho positions is used. Furthermore, certain compounds having a hindered phenol skeleton have a higher cation radical scavenging ability compared to compounds having a phenol skeleton in which tertiary or quaternary carbon atoms are bonded to both ortho positions. Therefore, in this embodiment, it is considered that the generation of burnt-on ghosting is suppressed compared to when using a compound having a phenol skeleton in which tertiary or quaternary carbon atoms are bonded to both ortho positions.

[0044] For the reasons stated above, it is presumed that the photoreceptor according to this embodiment is less prone to burn-in ghosting and that filming is suppressed.

[0045] The following describes in detail each layer of the polyester resin, specific compound, and photoreceptor having a dicarboxylic acid unit (A).

[0046] [Polyester resin containing dicarboxylic acid units (A)] The polyester resin having a dicarboxylic acid unit (A) is not particularly limited as long as it is a polyester resin having a dicarboxylic acid unit (A). Hereinafter, the polyester resin having a dicarboxylic acid unit (A) will also be referred to as the "specific polyester resin". The specified polyester resin may have only one type of dicarboxylic acid unit (A), or it may have two or more types.

[0047] The polyester resin having dicarboxylic acid units (A) is preferably a polyester resin (1) having at least dicarboxylic acid units (A) and diol units (B). The polyester resin (1) may also contain other dicarboxylic acid units other than dicarboxylic acid units (A). The polyester resin (1) may also contain other diol units other than diol units (B).

[0048] The dicarboxylic acid unit (A) is a constituent unit represented by the following formula (A).

[0049] [ka]

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] L A 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] The dicarboxylic acid unit (A) preferably includes at least one selected from the group consisting of the dicarboxylic acid unit (A1) represented by the following formula (A1), the dicarboxylic acid unit (A2) represented by the following formula (A2), the dicarboxylic acid unit (A3) represented by the following formula (A3), the dicarboxylic acid unit (A4) represented by the following formula (A4), and the dicarboxylic acid unit (A5) represented by the following formula (A5).

[0060] [ka]

[0061] In equation (A1), n 101 n is an integer between 0 and 4, and 101 Individual Ra 101 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 101 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0062] [ka]

[0063] In equation (A2), n 201 and n 202 Each of these is an independent integer between 0 and 4, and n 201 Individual Ra 201 and n 202 Individual Ra 202 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 201 It 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.

[0064] [ka]

[0065] In equation (A3), n 301 and n 302Each 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.

[0066] [ka]

[0067] 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.

[0068] [ka]

[0069] 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 503Each 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.

[0070] Ra in equation (A1) 101 Ra in equation (A2) 201 and Ra 202 Ra of formula (A3) 301 and Ra 302 Ra in 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] Below are examples of dicarboxylic acid units (A1-1) to (A1-9). Dicarboxylic acid units (A1) are not limited to these examples.

[0075] [ka]

[0076] Below are examples of dicarboxylic acid units (A2) (A2-1) to (A2-5). Dicarboxylic acid units (A2) are not limited to these examples.

[0077] [ka]

[0078] The following are examples of dicarboxylic acid units (A3), specifically (A3-1) to (A3-2). However, dicarboxylic acid units (A3) are not limited to these examples.

[0079] [ka]

[0080] Below are examples of dicarboxylic acid units (A4-1) to (A4-3). Dicarboxylic acid units (A4) are not limited to these examples.

[0081] [ka]

[0082] Below are examples of dicarboxylic acid units (A5), specifically (A5-1) to (A5-4). Dicarboxylic acid units (A5) are not limited to these examples.

[0083] [ka]

[0084] The dicarboxylic acid units (A) are preferably (A1-1), (A1-7), (A2-3), (A2-4), (A3-2), and (A4-3) as shown in the above examples, more preferably (A2-3) and (A2-4), and most preferably (A2-3).

[0085] The total mass percentage of dicarboxylic acid units (A1) to (A5) in the polyester resin (1) is preferably 15% by mass or more and 60% by mass or less. When the total mass percentage of dicarboxylic acid units (A1) to (A5) is 15% by mass or more, the abrasion resistance of the photosensitive layer is good. From this viewpoint, the total mass percentage of dicarboxylic acid units (A1) to (A5) is more preferably 20% by mass or more, and even more preferably 25% by mass or more. When the total mass percentage of dicarboxylic acid units (A1) to (A5) is 60% by mass or less, peeling of the photosensitive layer can be suppressed. From this viewpoint, the total mass percentage of dicarboxylic acid units (A1) to (A5) is more preferably 55% by mass or less, and even more preferably 50% by mass or less. The dicarboxylic acid units (A1) to (A5) contained in the polyester resin (1) may be one type or two or more types.

[0086] Other dicarboxylic acid units (A) besides dicarboxylic acid units (A1) to (A5) include, for example, 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 their lower (e.g., C1 to C5) alkyl ester units. The polyester resin (1) may contain one or more of these dicarboxylic acid units.

[0087] The dicarboxylic acid unit (A) contained in the polyester resin (1) may be one type or two or more types.

[0088] The diol unit (B) is a constituent unit represented by the following formula (B).

[0089] [ka]

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] Ar B2 The hydrogen atoms on the aromatic ring are alkyl groups, aryl groups, aralkyl groups, and alkoxy groups. It may be substituted with a cy group, aryloxy group, halogen atom, 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] The diol unit (B) 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 following formula (B2), the diol unit (B3) represented by the following formula (B3), the diol unit (B4) represented by the following formula (B4), the diol unit (B5) represented by the following formula (B5), the diol unit (B6) represented by the following formula (B6), the diol unit (B7) represented by the following formula (B7), and the diol unit (B8) represented by the following formula (B8).

[0099] 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 following formula (B2), the diol unit (B4) represented by the following formula (B4), the diol unit (B5) represented by the following formula (B5), and the diol unit (B6) 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 (B1) represented by the following formula (B1), a diol unit (B2) represented by the following formula (B2), a diol unit (B5) represented by the following formula (B5), and a diol unit (B6) represented by the following formula (B6). It is even more preferable to include at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the following formula (B2), and a diol unit (B6) 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).

[0100] [ka]

[0101] 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.

[0102] 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.

[0103] [ka]

[0104] 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.

[0105] 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.

[0106] [ka]

[0107] 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.

[0108] 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.

[0109] [ka]

[0110] 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.

[0111] 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.

[0112] [ka]

[0113] 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.

[0114] 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.

[0115] [ka]

[0116] 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 5 or 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.

[0117] 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.

[0118] [ka]

[0119] 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.

[0120] [ka]

[0121] 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.

[0122] 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 "[...]."

[0123] 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.

[0124] 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 "[...]."

[0125] 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.

[0126] 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.

[0127] Rb 400 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0128] 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 "[...]."

[0129] 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.

[0130] 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.

[0131] Rb 500 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0132] 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 "[...]."

[0133] 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.

[0134] 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.

[0135] Rb 800 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0136] 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 "[...]."

[0137] 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.

[0138] 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.

[0139] Rb 900 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0140] The following are specific examples of diol units (B1), specifically (B1-1) to (B1-6). Diol units (B1) are not limited to these examples.

[0141] [ka]

[0142] The following are specific examples of diol units (B2), specifically (B2-1) to (B2-11). Diol units (B2) are not limited to these examples.

[0143] [ka]

[0144] The following are specific examples of diol units (B3), namely (B3-1) to (B3-4). Diol units (B3) are not limited to these examples.

[0145] [ka]

[0146] The following are examples of diol units (B4-1) to (B4-7). Diol units (B4) are not limited to these examples.

[0147] [ka]

[0148] The following are examples of diol units (B5-1) to (B5-6). Diol units (B5) are not limited to these examples.

[0149] [ka]

[0150] The following are examples of diol units (B6-1) to (B6-4). Diol units (B6) are not limited to these examples.

[0151] [ka]

[0152] The following are examples of diol units (B7-1) to (B7-3). Diol units (B7) are not limited to these examples.

[0153] [ka]

[0154] The following are specific examples of diol units (B8), namely (B8-1) to (B8-3). Diol units (B8) are not limited to these examples.

[0155] [ka]

[0156] The diol units (B) contained in the polyester resin (1) may be one type or two or more types.

[0157] The mass percentage of diol units (B) in the polyester resin (1) 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 photosensitive 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 photosensitive layer and improve abrasion 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.

[0158] Other diol units besides diol unit (B) include, for example, 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 polyester resin (1) may contain one or more of these diol units.

[0159] The ends of the polyester resin (1) may be sealed or modified with an end-capping agent or molecular weight modifier 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-phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 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.

[0160] The weight-average molecular weight of the polyester resin (1) 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 the polyester resin (1) is the polystyrene-equivalent molecular weight measured by GPC (gel permeation chromatography). Tetrahydrofuran is used as the eluent for GPC.

[0161] Methods for producing polyester resin (1) include interfacial polymerization, solution polymerization, and melt polymerization.

[0162] [Compounds having a specific hindered phenol structure] Compounds having a specific hindered phenol structure are those with a molecular weight of 255 or more, possessing a hindered phenol skeleton, and lacking a linear alkylene structure with 4 or more carbon atoms. The molecular weight of the specific compound is 255 or more, and from the viewpoint of achieving both suppression of filming and suppression of burnt-on ghosting, it is preferably 255 to 1200, more preferably 300 to 980, and even more preferably over 350 to 750.

[0163] A hindered phenol skeleton is a phenol skeleton in which a primary or secondary carbon atom is bonded to one ortho position and a tertiary or quaternary carbon atom is bonded to the other. The atom bonded to the meta position of the hindered phenol skeleton is not particularly limited and includes hydrogen atoms, primary carbon atoms, secondary carbon atoms, tertiary carbon atoms, quaternary carbon atoms, etc. Among these, hydrogen atoms or primary carbon atoms are preferred, and hydrogen atoms are more preferred. The atoms bonded to the two meta positions may be the same or different. The atoms bonded to the para position of the hindered phenol skeleton are not particularly limited and include hydrogen atoms, primary carbon atoms, secondary carbon atoms, tertiary carbon atoms, quaternary carbon atoms, etc. Among these, hydrogen atoms, primary carbon atoms, or secondary carbon atoms are preferred, and primary carbon atoms or secondary carbon atoms are more preferred.

[0164] Examples of compounds having a hindered phenol skeleton include the compound represented by the following formula (C).

[0165] [ka]

[0166] In equation (C), Rc 001 Rc is a monovalent organic group in which the atom directly attached to the benzene ring is a primary or secondary carbon atom, 002 Rc is a monovalent organic group in which the atom directly bonded to the benzene ring is a tertiary or quaternary carbon atom. 003 and Rc 004 Each is independently a hydrogen atom or an alkyl group, and Rc 005 Rc is a monovalent organic group in which the atom directly attached to the benzene ring is a carbon atom or a hydrogen atom. 001 ~Rc 005 None of them have a linear alkylene structure with four or more carbon atoms.

[0167] Rc 001 This refers to any monovalent organic group in which the atom directly bonded to the benzene ring is a primary or secondary carbon atom and does not have a linear alkylene structure with 4 or more carbon atoms. For example, a group represented by the following formula (C001) can be mentioned.

[0168] [ka]

[0169] In formula (C001), * represents the bond position to the ortho position of the benzene ring in formula (C), and Rc 011 Rc is a hydrogen atom or a monovalent organic group. 011 It does not have a linear alkylene structure with 3 or more carbon atoms.

[0170] Rc 011 The monovalent organic group represented by may contain a heteroatom. However, Rc 011In the monovalent organic group represented by (C001), it is preferable that the atom directly bonded to the carbon atom in formula (C001) is a carbon atom. Examples of heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, etc. 011 The monovalent organic group represented by is preferably a group consisting of a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, and a hydrogen atom, more preferably a group consisting of a carbon atom, an oxygen atom, and a hydrogen atom, and even more preferably a group consisting of a carbon atom and a hydrogen atom. 011 The monovalent organic group represented by may include an aromatic ring and may also include a hindered phenol skeleton. Rc 011 Examples include alkyl groups which may contain heteroatoms between hydrogen atoms and carbon atoms, and groups containing a hindered phenol skeleton. Preferably, a group containing a hydrogen atom, a methyl group, an ethyl group, and a hindered phenol skeleton is preferred, more preferably a group containing a hydrogen atom, a methyl group, and a hindered phenol skeleton is preferred, and even more preferably a group containing a hydrogen atom and a hindered phenol skeleton is preferred.

[0171] Rc 001 The group is preferably a methyl group, an ethyl group, or a group containing a hindered phenol skeleton, and more preferably a methyl group or a group containing a hindered phenol skeleton.

[0172] Rc 002 This refers to a monovalent organic group in which the atom directly bonded to the benzene ring is a tertiary or quaternary carbon atom, and which does not have a linear alkylene structure with 4 or more carbon atoms. For example, a group represented by the following formula (C002) can be mentioned.

[0173] [ka]

[0174] In formula (C002), * represents the bond position to the ortho position of the benzene ring in formula (C), and Rc 012 and Rc 022 Each of these is independently a monovalent organic group, and Rc 012 and Rc 022These may bond with each other to form a ring, Rc 032 is a monovalent organic group or hydrogen atom, Rc 012 , Rc 022 and Rc 033 None of them have a straight-chain alkylene structure with 3 or more carbon atoms.

[0175] Rc 012 , Rc 022 or Rc 032 The monovalent organic group represented by may contain a heteroatom. However, Rc 012 , Rc 022 or Rc 032 In the monovalent organic group represented by formula (C002), it is preferable that the atom directly bonded to the carbon atom is a carbon atom. Examples of heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, etc. 012 , Rc 022 or Rc 032 The monovalent organic group represented by is preferably a group consisting of a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, and a hydrogen atom, more preferably a group consisting of a carbon atom, an oxygen atom, and a hydrogen atom, and even more preferably a group consisting of a carbon atom and a hydrogen atom. Rc 012 and Rc 022 Examples include alkyl groups, which may contain heteroatoms between carbon atoms, independently of each other. 032 Examples include alkyl groups that may contain heteroatoms between hydrogen and carbon atoms.

[0176] Rc 002 Examples include isopropyl groups, sec-butyl groups, tert-butyl groups, cycloalkyl groups having 3 to 9 carbon atoms, and 1-methylcycloalkyl groups having 3 to 9 carbon atoms. Rc 002 The group is preferably an isopropyl group, a sec-butyl group, a tert-butyl group, a cyclohexyl group, or a 1-methylcyclohexyl group, and more preferably a tert-butyl group, a cyclohexyl group, or a 1-methylcyclohexyl group.

[0177] Rc 003 and Rc 004 Each is independently an alkyl group or a hydrogen atom, and Rc 003 and Rc 004 None of them have a linear alkylene structure with 4 or more carbon atoms. Rc 003 and Rc 004 Examples include hydrogen atoms, methyl groups, ethyl groups, propyl groups, isopropyl groups, and the like. Rc 003 and Rc 004 Each of these is independently preferably a hydrogen atom or a methyl group, with the hydrogen atom being more preferable. Rc 003 and Rc 004 They may be the same, or they may be different from one another.

[0178] Rc 005 This is a monovalent organic group or hydrogen atom in which the atom directly attached to the benzene ring is a carbon atom, and Rc 005 It does not have a linear alkylene structure with 4 or more carbon atoms. 005 Examples of monovalent organic groups represented by the formula (C005) below include the group represented by the formula (C005).

[0179] [ka]

[0180] In formula (C005), * represents the bond position at the para position of the benzene ring in formula (C), and Rc 015 and Rc 025 Each is independently a hydrogen atom or a monovalent organic group, and Rc 015 and Rc 025 None of them have a linear alkylene structure with 3 or more carbon atoms.

[0181] Rc 015 or Rc 025 Each of the monovalent organic groups represented by may independently contain a heteroatom. However, Rc 015 or Rc 025In the monovalent organic group represented by (C005), it is preferable that the atom directly bonded to the carbon atom in formula (C005) is a carbon atom. Examples of heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, etc. 015 or Rc 025 The monovalent organic group represented by is preferably a group consisting of a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, and a hydrogen atom, more preferably a group consisting of a carbon atom, an oxygen atom, and a hydrogen atom, and even more preferably a group consisting of a carbon atom and a hydrogen atom. 015 or Rc 025 Each of the monovalent organic groups represented by may independently contain an aromatic ring or a hindered phenol skeleton. Rc 015 and Rc 025 Examples of these groups include, independently, an alkyl group which may contain a heteroatom between a hydrogen atom and a carbon atom, and a group containing a hindered phenol skeleton. Preferably, a group containing a hydrogen atom, a methyl group, an ethyl group, and a hindered phenol skeleton is preferred, more preferably a group containing a hydrogen atom, a methyl group, and a hindered phenol skeleton is preferred, and even more preferably a group containing a hydrogen atom and a hindered phenol skeleton.

[0182] Rc 005 The group is preferably an alkyl group which may contain a heteroatom between the hydrogen atom and carbon atoms, or a hindered phenol skeleton; more preferably a group which contains a hydrogen atom, a methyl group, an ethyl group, or a hindered phenol skeleton; and even more preferably a group which contains a methyl group or a hindered phenol skeleton.

[0183] From the viewpoint of suppressing burnt-on ghosting, it is preferable that the specific compound has two or more hindered phenol skeletons in one molecule. The number of hindered phenol skeletons contained in one molecule of a particular compound can be between 2 and 4, preferably between 2 and 3, and more preferably 2. When a particular compound has two or more hindered phenol skeletons in one molecule, the ortho, meta, and para positions of one hindered phenol skeleton may be bonded to another hindered phenol skeleton via a linking group. In particular, it is preferable that the ortho or para position of one hindered phenol skeleton is bonded to another hindered phenol skeleton via a linking group. The bond positions of the two or more hindered phenol skeletons may be the same or different. That is, in the two or more hindered phenol skeletons, the ortho positions may be bonded to each other via a linking group, the para positions may be bonded to each other via a linking group, or the ortho position of one hindered phenol skeleton may be bonded to the para position of the other hindered phenol skeleton via a linking group.

[0184] The linking group connecting two or more phenol skeletons is not particularly limited as long as it is a linking group that does not have a linear alkylene structure with four or more carbon atoms. Examples include linear or branched aliphatic hydrocarbon groups with a valency of 2 to 4, cyclic aliphatic hydrocarbon groups with a valency of 2 to 4, ester bonds (-C(=O)O-), ether bonds (-O-), aromatic rings, isocyanurate rings, and combinations thereof. Among these, preferred linking groups for connecting two or more phenol skeletons are those consisting of a linear or branched aliphatic hydrocarbon group with a valency of 2 to 4, a linking group in which at least one of an ester bond (-C(=O)O-) and an ether bond (-O-) is interposed between the carbon-carbon bonds of a divalent to 4, a combination of a divalent to 4, or less aliphatic hydrocarbon group and an aromatic ring, and a combination of a divalent to 4, or less aliphatic hydrocarbon group and an isocyanurate ring. More preferred are linking groups consisting of a linear or branched aliphatic hydrocarbon group with a valency of 2 to 4, and linking groups in which at least one of an ester bond (-C(=O)O-) and an ether bond (-O-) is interposed between the carbon-carbon bonds of a divalent to 4, or less aliphatic hydrocarbon group.

[0185] When a specific compound has two or more hindered phenol skeletons in one molecule, it is preferable that the two or more phenol skeletons have at least one of the following structures: one in which the ortho position of the first phenol skeleton and the ortho position of the second phenol skeleton are linked via an alkylene group having 1 to 3 carbon atoms, and another in which the para position of the first phenol skeleton and the para position of the second phenol skeleton are linked via a divalent linking group.

[0186] The specific compound is more preferably a compound represented by the following formula (C1), the following formula (C2), or the following formula (C3), and even more preferably a compound represented by the following formula (C1) or the following formula (C2).

[0187] [ka]

[0188] In equations (C1), (C2), and (C3), Rc 201 , Rc 211 , Rc 301 , Rc 311 and Rc 321 Each of these is independently a monovalent organic group in which the atom directly bonded to the benzene ring is either a primary or secondary carbon atom, and Rc 102 , Rc 112 , Rc 202 , Rc 212 , Rc 302 , Rc 312 and Rc 322 Each of these is independently a monovalent organic group in which the atom directly bonded to the benzene ring is a tertiary carbon atom or a quaternary carbon atom, and Rc 103 , Rc 104 , Rc 113 , Rc 114 , Rc 203 , Rc 204 , Rc 213 , Rc 214 , Rc 303 , Rc 304 , Rc 313 , Rc 314 , Rc 323 and Rc 324Each is independently a hydrogen atom or an alkyl group, and Rc 105 and Rc 115 Each of these is independently a monovalent organic group or a hydrogen atom whose atom directly bonded to the benzene ring is a carbon atom, and n c1 Lc is an integer between 1 and 3, and 200 Lc is a divalent linking group. 300 It is a trivalent linking group, Rc 102 ~Rc 105 , Rc 112 ~Rc 115 , Rc 201 ~Rc 204 , Rc 211 ~Rc 214 , Rc 301 ~Rc 304 , Rc 311 ~Rc 314 , Rc 321 ~Rc 324 Lc 200 and Lc 300 None of them have a linear alkylene structure with four or more carbon atoms.

[0189] Rc 201 , Rc 211 , Rc 301 , Rc 311 and Rc 321 Specific examples and preferred groups are the aforementioned Rc 001 The specific examples and preferred groups are similar to those in [reference]. Rc 102 , Rc 112 , Rc 202 , Rc 212 , Rc 302 , Rc 312 and Rc 322 Specific examples and preferred groups are the aforementioned Rc 002 The specific examples and preferred groups are similar to those in [reference]. Rc 103 , Rc 104 , Rc 113 , Rc 114 , Rc 203 , Rc 204 , Rc 213 , Rc 214 , Rc 303 , Rc 304 , Rc 313, Rc 314 , Rc 323 and Rc 324 Specific examples and preferred groups are the aforementioned Rc 003 and Rc 004 The specific examples and preferred groups are similar to those in [reference]. Rc 105 and Rc 115 Specific examples and preferred groups are the aforementioned Rc 005 The specific examples and preferred groups are similar to those in [reference]. n c1 is an integer between 1 and 3, preferably between 1 and 2, and more preferably 1.

[0190] Lc 200 The divalent linking group represented by is not particularly limited as long as it is a divalent linking group and does not have a linear alkylene structure with 4 or more carbon atoms. Lc 200 Examples of divalent linking groups represented by include linear or branched divalent aliphatic hydrocarbon groups, cyclic divalent aliphatic hydrocarbon groups, ester bonds (-C(=O)O-), ether bonds (-O-), aromatic rings, isocyanurate rings, and combinations thereof. Lc 200 The divalent linking group represented by is preferably a linking group consisting of a linear or branched divalent aliphatic hydrocarbon group, a linking group in which at least one of an ester bond (-C(=O)O-) and an ether bond (-O-) is interposed between the carbon-carbon bonds of the divalent aliphatic hydrocarbon group, and a combination of a divalent aliphatic hydrocarbon group and an aromatic ring, and more preferably a linking group consisting of a linear or branched divalent aliphatic hydrocarbon group, and a linking group in which at least one of an ester bond (-C(=O)O-) and an ether bond (-O-) is interposed between the carbon-carbon bonds of the divalent aliphatic hydrocarbon group. Lc 200 Specific examples of divalent linking groups represented by the formulas (Lc2-1) to (Lc2-6) below include the linking groups represented by the following formulas. In the following formulas, * represents the bond position to the para position of the benzene ring in formula (C2), and n c21 , n c22 , n c23 , n c24 , n c25 , nc26 , n c27 , n c28 , n c29 and n c30 Each of these is an independent integer between 1 and 3. 200 The divalent linking groups represented by these are not limited to these.

[0191] [ka]

[0192] Lc 300 The trivalent linking group represented by is not particularly limited as long as it is a trivalent linking group and does not have a linear alkylene structure with 4 or more carbon atoms. Lc 300 Examples of trivalent linking groups represented by include trivalent aliphatic hydrocarbon groups, ester bonds (-C(=O)O-), ether bonds (-O-), aromatic rings, isocyanurate rings, and combinations thereof. Lc 300 The trivalent linking group represented by is preferably a linking group consisting of a trivalent aliphatic hydrocarbon group, a linking group in which at least one of an ester bond (-C(=O)O-) and an ether bond (-O-) is interposed between the carbon-carbon bonds of the trivalent aliphatic hydrocarbon group, a combination of a trivalent aliphatic hydrocarbon group and an aromatic ring, and a combination of a trivalent aliphatic hydrocarbon group and an isocyanurate ring, and more preferably a linking group consisting of a trivalent aliphatic hydrocarbon group, a combination of a trivalent aliphatic hydrocarbon group and an aromatic ring, and a combination of a trivalent aliphatic hydrocarbon group and an isocyanurate ring. Lc 300 Specific examples of trivalent linking groups represented by include trivalent alkylene groups having 3 to 10 carbon atoms, and linking groups represented by the following formulas (Lc3-1) to (Lc3-2). In the following formulas, * represents the bond position to the para position of the benzene ring in formula (C3), and n c31 , n c32 , n c33 , n c34 , n c35 and n c36 Each of these is an independent integer between 1 and 3. 300The trivalent linking groups represented by these are not limited to these.

[0193] [ka]

[0194] The following are specific examples of designated compounds: (C1-1) to (C1-12), (C2-1) to (C2-18), (C3-1) to (C3-9), and (C4-1) to (C4-3). Designated compounds are not limited to these.

[0195] [ka]

[0196] [ka]

[0197] [ka]

[0198] [ka]

[0199] [ka]

[0200] [ka]

[0201] In the photoreceptor according to the first embodiment, the content of the compound having a specific hindered phenol structure in the charge transport layer is preferably 0.5% by mass or more and 10.0% by mass or less, more preferably 1.5% by mass or more and 7.5% by mass or less, and even more preferably 2.0% by mass or more and 5.0% by mass or less, relative to the entire charge transport layer. In the photoreceptor according to the second embodiment, the content of the compound having a specific hindered phenol structure in the single-layer photoreceptor is preferably 0.5% by mass or more and 10.0% by mass or less, more preferably 1.5% by mass or more and 7.5% by mass or less, and even more preferably 2.0% by mass or more and 5.0% by mass or less, relative to the single-layer photoreceptor. When the content of the compound having a specific hindered phenol structure in the entire photosensitive layer is within the above range, burn-in ghosting is suppressed compared to when the content is lower than the above range, and filming is suppressed compared to when the content is higher than the above range.

[0202] In the photoreceptor according to the first embodiment, the amount of phenolic hydroxyl groups in the compound having a specific hindered phenol structure contained in the charge transport layer is preferably 5 mol% to 50 mol%, more preferably 8 mol% to 40 mol%, and even more preferably 10 mol% to 30 mol%, relative to the number of moles of charge transport material contained in the charge transport layer. In the photoreceptor according to the second embodiment, the amount of phenolic hydroxyl groups in the compound having a specific hindered phenol structure contained in the single-layer photoreceptor is preferably 5 mol% to 50 mol%, more preferably 8 mol% to 40 mol%, and even more preferably 10 mol% to 30 mol%, relative to the number of moles of charge transport material contained in the single-layer photoreceptor. When the amount of phenolic hydroxyl groups in a compound having a specific hindered phenol structure relative to the number of moles of charge transport material is within the above range, there are advantages such as suppressing burn-on ghosting compared to when the amount is lower than the above range, and suppressing residual potential during cycle stress compared to when the amount is higher than the above range.

[0203] The layers of the electrophotographic photoreceptor according to the first and second embodiments will be described in detail below. Reference numerals will be omitted in the description.

[0204] [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 Ωcm.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0213] As for inorganic particles, for example, powder resistance (volume resistivity) 10 2 Ωcm or more 10 11 Examples include inorganic particles smaller than Ωcm. 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.

[0214] 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).

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] 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.

[0220] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry or wet method.

[0221] 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.

[0222] In this case, it is preferable for the underlayer to contain electron-accepting compounds (acceptor compounds) along with inorganic particles, from the viewpoint of improving the long-term stability of electrical properties and carrier blocking ability.

[0223] Examples of electron-accepting compounds include quinone compounds such as chloranil and bromonil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; and diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone; as well as other electron-transporting substances. In particular, compounds having an anthraquinone structure are preferred as electron-accepting compounds. Examples of compounds having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds, and specifically, for example, anthraquinone, alizarin, quinizalin, anthralphine, and purpurin are preferred.

[0224] The electron-accepting compound may be dispersed in the underlayer together with inorganic particles, or it may be present attached to the surface of the inorganic particles.

[0225] Methods for attaching electron-accepting compounds to the surface of inorganic particles include, for example, dry methods or wet methods.

[0226] 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.

[0227] The wet method involves dispersing inorganic particles in a solvent using methods such as stirring, ultrasound, sand milling, attritoring, and ball milling, while adding an electron-accepting compound. After stirring or dispersion, the solvent is removed to adhere the electron-accepting compound 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.

[0228] 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.

[0229] The content of the electron-accepting compound is preferably, for example, 0.01% by mass or more and 20% by mass or less relative to the inorganic particles, and more preferably 0.01% by mass or more and 10% by mass or less.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] 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.

[0236] Examples of aluminum chelating compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0237] These additives may be used individually or as a mixture or polycondensate of multiple compounds.

[0238] 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.

[0239] There are no particular restrictions on the formation of the undercoat, 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.

[0240] 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. Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellsolve, ethyl cellsolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0241] 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.

[0242] 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.

[0243] The thickness of the undercoat layer is preferably set to a range of 15 μm or more, and more preferably 20 μm to 50 μm.

[0244] [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.

[0245] Among these, the intermediate layer is preferably a layer containing an organometallic compound that contains zirconium atoms or silicon atoms.

[0246] 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, knife coating, and curtain coating are used to form the intermediate layer.

[0247] 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.

[0248] [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.

[0249] 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.

[0250] 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.

[0251] 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.

[0252] Even when using non-coherent light sources such as LEDs and organic EL image arrays with a central emission wavelength between 450 nm and 780 nm, the above charge generating materials may be used. However, from the viewpoint of resolution, when using a thin film of 20 μm or less for the photosensitive layer, the electric field strength in the photosensitive layer becomes high, making it easier for charge reduction due to charge injection from the substrate to occur, resulting in image defects known as black spots. This is particularly noticeable when using charge generating materials that are p-type semiconductors that easily generate dark current, such as trigonal selenium and phthalocyanine pigments.

[0253] In contrast, 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. 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.

[0254] 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 (polycondensate of bisphenols and aromatic divalent carboxylic acids, etc.), 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" refers to a volume resistivity of 10 13 This refers to a value of Ωcm or greater. These binder resins can be used individually or in combination of two or more types.

[0255] 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.

[0256] The charge generation layer may also contain other well-known additives.

[0257] 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.

[0258] Solvents for preparing the coating solution for forming the charge generation layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellsolve, ethyl cellsolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene. These solvents may be used individually or in mixtures of two or more.

[0259] 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.

[0260] 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.

[0261] 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.

[0262] [Charge transport layer] The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may also be a layer containing a polymer charge transport material.

[0263] 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.

[0264] As polymer charge transport materials, known charge transport materials such as poly-N-vinylcarbazole and polysilane can be used. Polyester-based polymer charge transport materials are particularly preferred. The polymer charge transport material may be used alone, or it may be used in combination with a binder resin.

[0265] 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.

[0266] From the viewpoint of charge mobility, the charge transport material preferably contains at least one compound selected from the group consisting of a compound represented by the following formula (D1) (D1), a compound represented by the following formula (D2) (D2), a compound represented by the following formula (D3) (D3), and a compound represented by the following formula (D4) (D4).

[0267] [ka]

[0268] In equation (D1), 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 is independent It is 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 -C(R 61 )=C(R 62 )- may be linked by at least one divalent group selected from the group consisting of 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.

[0269] The group in formula (D1) 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.

[0270] As for compound (D1), from the viewpoint of charge mobility, it is an aryl group or -C6H4-CH=CH-CH=C(R T7 )(R T8 A compound having at least one of the following is preferred, and a compound represented by the following formula (D'1) (D'1) is more preferred.

[0271] [ka]

[0272] In equation (D'1), R T111 , R T112 , R T121 , R T122 , R T131 and R T132Each of these 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.

[0273] [ka]

[0274] In equation (D2), R T201 , R T202 , R T211 and R T212 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 T21 )=C(R T22 )(R T23 ) or -CH=CH-CH=C(R T24 )(R T25 ) is R T21 , R T22 , R T23 , R T24 and R T25 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T221 and R T222 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. Tm1, Tm2, ​​Tn1, and Tn2 are each independently 0, 1, or 2.

[0275] The group in formula (D2) 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.

[0276] As for compound (D2), from the viewpoint of charge mobility, it can be an alkyl group, an aryl group, or -CH=CH-CH=C(R T24 )(R T25A compound having at least one -CH=CH-CH=C(R) group is preferred, and is an alkyl group, an aryl group, or -CH=CH-CH=C(R) group. T24 )(R T25 Compounds having two of these are more preferable.

[0277] [ka]

[0278] In equation (D3), R T301 , R T302 , R T311 and R T312 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 T31 )=C(R T32 )(R T33 ) or -CH=CH-CH=C(R T34 )(R T35 ) is R T31 , R T32 , R T33 , R T34 and R T35 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T321 , R T322 and R T331 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. To1, To2, Tp1, Tp2, Tq1, Tq2, and Tr1 are each independently 0, 1, or 2.

[0279] The group in formula (D3) 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.

[0280] [ka]

[0281] In equation (D4), 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.

[0282] The group in formula (D4) 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.

[0283] 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.

[0284] The charge transport layer contains a polyester resin having at least dicarboxylic acid units (A) as a binder resin. The total proportion of the polyester resin having dicarboxylic acid units (A) in the total amount of binder resin contained in the charge transport layer is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

[0285] The charge transport layer may contain other binder resins other than polyester resins having dicarboxylic acid units (A). Examples of other binder resins include polyester resins other than polyester resins having dicarboxylic acid units (A), polycarbonate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, polysilanes, etc. These binder resins may be used individually or in combination of two or more.

[0286] The charge transport layer contains at least one specific compound as an antioxidant. The charge transport layer may also contain antioxidants other than the specific compound. From the viewpoint of achieving both suppression of filming and suppression of burn-on ghosting, it is preferable that the charge transport layer does not contain antioxidants other than the specific compound. The total proportion of specific compounds in the total amount of antioxidants contained in the charge transport layer is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0287] The charge transport layer may also contain other known additives. Examples of additives include leveling agents, defoaming agents, fillers, and viscosity modifiers.

[0288] The formation of the charge transport 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 transport layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0289] 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.

[0290] 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.

[0291] The average thickness of the charge transport layer is preferably 5 μm to 60 μm, more preferably 10 μm to 55 μm, and even more preferably 15 μm to 50 μm.

[0292] [Single-layer photosensitive layer] The single-layer photosensitive layer (charge generation / charge transport layer) is a layer comprising a charge generation material, a charge transport material, a binder resin, a compound having a specific hindered phenol structure, and other additives as needed. These materials are the same as those described for the charge generation layer and the charge transport layer.

[0293] The single-layer photosensitive layer contains a polyester resin having at least dicarboxylic acid units (A) as a binder resin. The total proportion of the polyester resin having dicarboxylic acid units (A) in the total amount of binder resin contained in the single-layer photosensitive layer is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

[0294] In the single-layer photosensitive layer, the content of the charge-generating material is preferably 0.1% to 10% by mass, and more preferably 0.8% to 5% by mass, relative to the total solid content.

[0295] The amount of charge transport material contained in the single-layer photosensitive layer should be between 40% and 60% by mass relative to the total solid content.

[0296] The method for forming a single-layer photosensitive layer is the same as the method for forming a charge generation layer or a charge transport layer.

[0297] The average thickness of the single-layer photosensitive layer is preferably 5 μm to 60 μm, more preferably 10 μm to 55 μm, and even more preferably 15 μm to 50 μm.

[0298] <Image forming apparatus and process cartridges> 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, and a transfer device for transferring the toner image to the surface of a recording medium. The electrophotographic photoreceptor according to this embodiment is used as the electrophotographic photoreceptor.

[0299] The image forming apparatus according to this embodiment includes a fixing device for fixing a toner image transferred to the surface of a recording medium; a direct transfer method apparatus for directly transferring a toner image formed on the surface of an electrophotographic photoreceptor to a recording medium; an intermediate transfer method 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; a cleaning device for cleaning the surface of the electrophotographic photoreceptor after the transfer of the toner image and before it is charged; 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 it is charged; and a well-known image forming apparatus such as an electrophotographic photoreceptor heating member for raising the temperature of the electrophotographic photoreceptor and reducing the relative temperature.

[0300] 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.

[0301] 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).

[0302] In the image forming apparatus according to this embodiment, for example, the part equipped with an 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 equipped with an 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.

[0303] 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 other parts will be omitted from the explanation.

[0304] Figure 3 is a schematic diagram showing an example of an image forming apparatus according to this embodiment. As shown in Figure 3, 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 facing 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.

[0305] In Figure 3, 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.

[0306] Figure 3 shows an example of an image forming apparatus equipped with 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.

[0307] The following describes the various components of the image forming apparatus according to this embodiment.

[0308] -Charging device- As the charging device 8, for example, a contact-type charger using conductive or semiconductive charging rollers, charging brushes, charging films, charging rubber blades, charging tubes, etc. may be used. Non-contact roller chargers, known chargers such as scorotron chargers and corotron chargers that utilize corona discharge may also be used.

[0309] -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.

[0310] -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.

[0311] 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. Well-known developers are applicable.

[0312] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131. In addition to the cleaning blade method, a fur brush cleaning method or a developing-simultaneous cleaning method may also be used.

[0313] -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.

[0314] -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, the intermediate transfer body may also be in the form of a drum.

[0315] Figure 4 is a schematic diagram showing another example of an image forming apparatus according to this embodiment. The image forming apparatus 120 shown in Figure 4 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one electrophotographic 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]

[0316] 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.

[0317] <Preparation of polyester resin> Polyester resins (PE1) to (PE7) were prepared. Table 1 shows the units and composition of the polyester resins. A2-3 and others listed in Table 1 are specific examples of the dicarboxylic acid unit (A) described above. Table 1 shows examples of B1-4, etc., which are specific examples of the diol unit (B) described above.

[0318] [Table 1]

[0319] <Manufacturing of photoreceptors with stacked photosensitive layers> [Examples S1-S20, Comparative Examples S1-S15] -Formation of the lower layer- As a conductive substrate, an aluminum cylindrical tube with an outer diameter of 30 mm, a length of 365 mm, and a wall thickness of 1.6 mm was prepared.

[0320] Zinc oxide (average particle size 70 nm, specific surface area 15 m²) 2 100 parts of (Teika Co., Ltd.) were mixed with 500 parts of toluene by stirring, and 1.3 parts of a silane coupling agent (product name: KBM603, Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) were added and the mixture was stirred for 2 hours. Then the toluene was removed by distillation under reduced pressure, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent.

[0321] 110 parts of surface-treated zinc oxide was mixed with 500 parts of tetrahydrofuran by stirring. A solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added, 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 alizarin-treated zinc oxide.

[0322] 60 parts of alizarin-modified zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, trade name: Sumijule 3175, manufactured by Sumitomo Bayern Urethanes), and 15 parts of butyral resin (trade name: Esrec BM-1, manufactured by Sekisui Chemical Co., Ltd.) were dissolved in 68 parts of methyl ethyl ketone. 100 parts of this solution were mixed with 5 parts of methyl ethyl ketone, and the mixture was dispersed for 2 hours using a sand mill with 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) were added to obtain a coating solution for forming the 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. The average thickness of the undercoat was 25 μm.

[0323] -Formation of a charge generation layer- A mixture consisting of 15 parts of hydroxygallium phthalocyanine as a charge-generating material (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in 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-generating layer. The coating solution for forming the charge-generating layer was immersed and coated onto the undercoat, and dried at room temperature (25℃±3℃) to form a charge-generating layer with an average thickness of 0.18 μm.

[0324] -Formation of a charge transport layer- A coating solution for forming a charge transport layer was obtained by dissolving 60 parts of a polyester resin of the type shown in Tables 2-3 as a binder resin, 40 parts of a charge transport material of the type shown in Tables 2-3 as a charge transport material, and a specific compound or an antioxidant other than the specific compound of the type and amount shown in Tables 2-3 as an antioxidant, in 550 parts of tetrahydrofuran and 50 parts of toluene. The coating solution for forming a charge transport layer was applied to a charge generating layer by immersion, and dried at a temperature of 150°C for 60 minutes to form a charge transport layer with an average thickness of 40 μm. The charge transport materials CTM-1 to CTM-5 listed in Tables 2 and 3 are the following compounds. C1-1, C2-1, C1-4, C1-3, C1-2, C2-4, and C4-1, listed in Table 2, are specific examples of the aforementioned compounds. The compounds HP-1 to HP-15 listed in Table 3 are as follows: The amount of phenolic hydroxyl groups of specific compounds or antioxidants other than specific compounds relative to the number of moles of charge transport material is shown in Tables 2-3 (in the column "Hydroxyl Groups (mol%)" in the table).

[0325] [ka]

[0326] [ka]

[0327] [ka]

[0328] [ka]

[0329] <Manufacturing of photoreceptors with a single-layer photosensitive layer> [Examples T1-T7, Comparative Examples T1-T3] -Formation of a single-layer photosensitive layer- A single-layer photosensitive coating solution was obtained by mixing 45.75 parts of a polyester resin of the type shown in Table 4 as a binder resin, 1.25 parts of V-type hydroxygallium phthalocyanine as a charge generating material (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.3°, 16.0°, 24.9°, and 28.0° in the X-ray diffraction spectrum using Cukα characteristic X-rays), 13 parts of ETM-1 as an electron transport material, 40 parts of a charge transport material of the type shown in Table 4 as a charge transport material, a specific compound or an antioxidant other than the specific compound shown in Table 4 in the type and amount added, and 175 parts of tetrahydrofuran and 75 parts of toluene as solvents. The mixture was dispersed using 1 mm diameter glass beads in a sand mill for 4 hours. The obtained photosensitive coating solution was applied by immersion coating onto an aluminum substrate with an outer diameter of 30 mm, a length of 365 mm, and a wall thickness of 1.6 mm. Drying was performed at a temperature of 150°C for 60 minutes to form a single-layer photosensitive layer with an average thickness of 36 μm. The electron transport material ETM-1 and the charge transport material CTM-1 listed in Table 4 are the following compounds. C1-1, C2-1, C1-3, and C2-4, listed in Table 4, are specific examples of the aforementioned compounds. HP-1, HP-5, and HP-15, listed in Table 4, are the aforementioned compounds. The amount of phenolic hydroxyl groups of specific compounds or antioxidants other than specific compounds relative to the number of moles of charge transport material is shown in Table 4 (in the column "Hydroxyl Groups (mol%)" in the table).

[0330] [ka]

[0331] <Evaluation of photoreceptor performance> [Electrical properties (burned-in ghost)] A photoreceptor was mounted in an electrophotographic image forming apparatus (Apeos C7070, manufactured by Fujifilm Business Innovation). In a high-temperature, high-humidity environment of 28°C and 85% relative humidity, 500 grid pattern charts were printed consecutively on A3-sized plain paper, and then one 30% halftone image in black (K) was output. The output halftone image was observed, and a visual sensory evaluation (grade determination) was performed on the density difference between the image and non-image areas of the 500 consecutively printed grid pattern charts. The grade determination was performed in 1G increments from 0 to 5G, with a smaller G number indicating a smaller density difference and suppression of burn-in ghosting. The grade determination results are shown in Tables 2 to 4.

[0332] [Filming] The photoreceptor was mounted in the image forming apparatus described above. Under high temperature and high humidity conditions of 28°C and 85% relative humidity, 50,000 image density patterns with 10% image density were continuously printed on A3 size paper. After evaluation, the photoreceptor was removed, and its surface was directly observed using a confocal laser microscope (OLS1100, OLYMPAS). Filming was evaluated based on the following criteria. The results are shown in Tables 2-4. -Filming Evaluation- A: No toner adhesion (filming) is observed on the surface of the photoconductor. B: Toner adhesion (filming) is visible on the surface of the photoconductor, but it can be removed by wiping with a non-woven cloth dampened with alcohol. C: Toner adhesion (filming) is observed on the surface of the photoconductor, and it cannot be removed even by wiping with a non-woven cloth dampened with alcohol.

[0333] [Table 2]

[0334] [Table 3]

[0335] [Table 4]

[0336] This disclosure includes the following aspects:

[0337] (((1))) A conductive substrate, A photosensitive layer disposed on the conductive substrate, comprising a multilayer type photosensitive layer having a charge generation layer and a charge transport layer, or a single-layer type photosensitive layer, Equipped with, The charge transport layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having a dicarboxylic acid unit (A) represented by the following formula (A), and a compound having a molecular weight of 255 or more, having a phenol skeleton in which a primary or secondary carbon atom is bonded to one ortho position and a tertiary or quaternary carbon atom is bonded to the other, and not having a linear alkylene structure with 4 or more carbon atoms. Electrophotographic photoreceptor.

[0338] [ka]

[0339] 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. (((2))) The aforementioned compound is an electrophotographic photoreceptor according to (((1))), having two or more of the phenol skeletons in one molecule. (((3))) The electrophotographic photoreceptor according to (((2))), wherein the two or more phenol skeletons have at least one of the following structures: a structure in which the ortho position of the first phenol skeleton and the ortho position of the second phenol skeleton are bonded via an alkylene group having 1 to 3 carbon atoms, and a structure in which the para position of the first phenol skeleton and the para position of the second phenol skeleton are bonded via a divalent linking group. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the content of the compound is 0.4% by mass or more and 10.0% by mass or less with respect to the entire charge transport layer or the single-layer photosensitive layer. (((5))) The electrophotographic photoreceptor according to any one of (((1))) to (((4))), wherein the amount of phenolic hydroxyl groups in the compound contained in the entire charge transport layer or the single-layer photosensitive layer is 5 mol% or more and 50 mol% or less with respect to the number of moles of the charge transport material. (((6))) An electrophotographic photoreceptor according to any one of (((1))) to (((5))), wherein the dicarboxylic acid unit (A) represented by formula (A) comprises at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by the following formula (A1), a dicarboxylic acid unit (A2) represented by the following formula (A2), a dicarboxylic acid unit (A3) represented by the following formula (A3), a dicarboxylic acid unit (A4) represented by the following formula (A4), and a dicarboxylic acid unit (A5) represented by the following formula.

[0340] [ka]

[0341] [ka]

[0342] In equation (A1), n 101 n is an integer between 0 and 4, and 101 Individual Ra 101 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. In equation (A2), n 201 and n 202 Each of these is an independent integer between 0 and 4, and n 201 Individual Ra 201 and n 202 Individual Ra 202Each 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. 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. 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. 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. (((7))) The electrophotographic photoreceptor according to any one of (((1))) to (((6))), wherein the polyester resin further comprises a diol unit (B) represented by the following formula (B).

[0343] [ka]

[0344] 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(Rb1 )(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. (((8))) The electrophotographic photoreceptor according to (((7))), wherein the diol unit (B) represented by formula (B) 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 following formula (B2), the diol unit (B3) represented by the following formula (B3), the diol unit (B4) represented by the following formula (B4), the diol unit (B5) represented by the following formula (B5), the diol unit (B6) represented by the following formula (B6), the diol unit (B7) represented by the following formula (B7), and the diol unit (B8) represented by the following formula (B8).

[0345] [ka]

[0346] [ka]

[0347] 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. 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. 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. 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. 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. In equation (B6), Rb 116 and Rb 216Each 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 Rb 406 , 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. 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. 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.

[0348] (((9))) The electrophotographic photoreceptor according to any one of (((1))) to (((8))), wherein the charge transport material comprises at least one selected from the group consisting of a compound (D1) represented by the following formula (D1), a compound (D2) represented by the following formula (D2), a compound (D3) represented by the following formula (D3), and a compound (D4) represented by the following formula (D4).

[0349] [ka]

[0350] In equation (D1), Ar T1 Ar T2 and Ar T3 Each is independently an aryl group, -C6H4-C(R T4 )=C(R T5 )(R T6 ) or -C6H4-CH=CH-CH=C(R T7 )(RT8 ) 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 -C(R 61 )=C(R 62 )- may be linked by at least one divalent group selected from the group consisting of 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. In equation (D2), R T201 , R T202 , R T211 and R T212 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 T21 )=C(R T22 )(R T23 ) or -CH=CH-CH=C(R T24 )(R T25 ) is R T21 , R T22 , R T23 , R T24 and R T25 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T221 and R T222 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. Tm1, Tm2, ​​Tn1, and Tn2 are each independently 0, 1, or 2. In equation (D3), R T301 , R T302 , R T311 and R T312Each 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 T31 )=C(R T32 )(R T33 ) or -CH=CH-CH=C(R T34 )(R T35 ) is R T31 , R T32 , R T33 , R T34 and R T35 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T321 , R T322 and R T331 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. To1, To2, Tp1, Tp2, Tq1, Tq2, and Tr1 are each independently 0, 1, or 2. In equation (D4), 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.

[0351] (((10))) The electrophotographic photoreceptor is provided as described in any one of (((1))) to (((9))), A process cartridge that is attached to and detached from an image forming apparatus. (((11))) The process cartridge according to (((10))), further comprising a cleaning device having a cleaning blade that contacts the surface of the electrophotographic photoreceptor and cleans the surface of the electrophotographic photoreceptor. (((12))) An electrophotographic photoreceptor described in any one of (((1))) to (((9))), A charging device for charging the surface of the electrophotographic photoreceptor, An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, A developing apparatus that develops an electrostatic latent image formed on the surface of an electrophotographic photoreceptor using a developer containing toner to form a toner image, A transfer device for transferring the toner image onto the surface of a recording medium, An image forming apparatus equipped with the following features. (((13))) The image forming apparatus according to (((12))), further comprising a cleaning device having a cleaning blade that contacts the surface of the electrophotographic photoreceptor and cleans the surface of the electrophotographic photoreceptor.

[0352] According to the inventions of (((1))), (((6))), (((7))), (((8))), or (((9))), an electrophotographic photoreceptor is provided that comprises a conductive substrate and a laminated photosensitive layer or a single-layer photosensitive layer, wherein the charge transport layer of the laminated photosensitive layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having dicarboxylic acid units (A), and a compound, and the compound has a molecular weight of less than 260. Compared to cases where a phenol skeleton is bonded to one ortho position with a hydrogen atom, a tertiary carbon atom, or a quaternary carbon atom bonded to the other, or a linear alkylene structure with 4 or more carbon atoms, an electrophotographic photoreceptor is provided that is less prone to burn-in ghosting and suppresses toner adhesion to the surface of the electrophotographic photoreceptor. According to the invention of (((2))) or (((3))), an electrophotographic photoreceptor is provided that is less prone to burn-in ghosting compared to the case in which the compound has only one phenol skeleton in one molecule. According to the invention of (((4))), an electrophotographic photoreceptor is provided that is less prone to burn-in ghosting compared to a case where the compound content is less than 0.4% by mass of the entire charge transport layer or single-layer photosensitive layer. According to the invention of (((5))), an electrophotographic photoreceptor is provided that is less prone to burn-in ghosting compared to a case where the amount of phenolic hydroxyl groups in the compound contained in the entire charge transport layer or single-layer photosensitive layer is less than 5 mol% of the moles of the charge transport material. According to the invention of (((10))) or (((11))), a process cartridge is provided which, compared to using an electrophotographic photoreceptor comprising a conductive substrate and a multilayer photosensitive layer or a single-layer photosensitive layer, wherein the charge transport layer of the multilayer photosensitive layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having dicarboxylic acid units (A), and a compound, wherein the compound has a molecular weight of less than 260, an electrophotographic photoreceptor having a phenol skeleton in which a hydrogen atom, a tertiary carbon atom, or a quaternary carbon atom is bonded to one ortho position and a tertiary carbon atom or a quaternary carbon atom is bonded to the other, or an electrophotographic photoreceptor having a linear alkylene structure with 4 or more carbon atoms, the process cartridge is provided which is less prone to burn-in ghosting and suppresses toner adhesion to the surface of the electrophotographic photoreceptor. According to the invention of (((12))) or (((13))), an image forming apparatus is provided that provides an electrophotographic photoreceptor that is less prone to burn-in ghosting and suppresses toner adhesion to the surface of the electrophotographic photoreceptor compared to the case in which an electrophotographic photoreceptor is used that comprises a conductive substrate and a laminated photosensitive layer or a single-layer photosensitive layer, wherein the charge transport layer of the laminated photosensitive layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having dicarboxylic acid units (A), and a compound, wherein the compound has a molecular weight of less than 260, an electrophotographic photoreceptor having a phenol skeleton in which a hydrogen atom, a tertiary carbon atom, or a quaternary carbon atom is bonded to one ortho position and a tertiary carbon atom or a quaternary carbon atom is bonded to the other, or an electrophotographic photoreceptor having a linear alkylene structure with 4 or more carbon atoms. [Explanation of Symbols]

[0353] 1 Conductive substrate, 2 Undercoat layer, 3 Charge generation layer, 4 Charge transport layer, 5 Photosensitive layer, 10A photoreceptor, 10B photoreceptor

[0354] 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 photosensitive layer disposed on the conductive substrate, comprising a multilayer type photosensitive layer having a charge generation layer and a charge transport layer, or a single-layer type photosensitive layer, Equipped with, The charge transport layer or the single-layer photosensitive layer is the outermost layer and contains a charge transport material, a polyester resin having at least one diol unit (B) selected from the group consisting of a dicarboxylic acid unit (A) represented by the following formula (A), a diol unit (B1) represented by the following formula (B1), and a diol unit (B2) represented by the following formula (B2), and a compound having a molecular weight of 255 or more, having a phenol skeleton in which a primary or secondary carbon atom is bonded to one ortho position and a tertiary or quaternary carbon atom is bonded to the other, and not having a linear alkylene structure with 4 or more carbon atoms. Electrophotographic photoreceptor. 【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. 【Chemistry 2】 In formula (B1), Rb 101 is a branched alkyl group having 4 to 20 carbon atoms, Rb 201 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 401, Rb 501, Rb 801, and Rb 901 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B2), Rb 102 is a linear alkyl group having 4 to 20 carbon atoms, Rb 202 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 402, Rb 502, Rb 802, and Rb 902 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

2. The electrophotographic photoreceptor according to claim 1, wherein the compound has two or more of the phenol skeletons in one molecule.

3. The electrophotographic photoreceptor according to claim 2, wherein the two or more phenol skeletons have at least one of the following structures: a structure in which the ortho position of the first phenol skeleton and the ortho position of the second phenol skeleton are bonded via an alkylene group having 1 to 3 carbon atoms, and a structure in which the para position of the first phenol skeleton and the para position of the second phenol skeleton are bonded via a divalent linking group.

4. The electrophotographic photoreceptor according to claim 1, wherein the content of the compound is 0.4% by mass or more and 10.0% by mass or less with respect to the entire charge transport layer or the single-layer photosensitive layer.

5. The electrophotographic photoreceptor according to claim 1, wherein the amount of phenolic hydroxyl groups in the compound contained in the entire charge transport layer or the single-layer photosensitive layer is 5 mol% or more and 50 mol% or less with respect to the number of moles of the charge transport material.

6. The electrophotographic photoreceptor according to claim 1, wherein the dicarboxylic acid unit (A) represented by formula (A) comprises at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by the following formula (A1), a dicarboxylic acid unit (A2) represented by the following formula (A2), a dicarboxylic acid unit (A3) represented by the following formula (A3), a dicarboxylic acid unit (A4) represented by the following formula (A4), and a dicarboxylic acid unit (A5) represented by the following formula (A5). 【Transformation 3】 【Chemistry 4】 In equation (A1), n １０１ n is an integer between 0 and 4, and １０１ Individual Ra １０１ 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. In formula (A2), n ２０１ and n ２０２ are each independently an integer of 0 or more and 4 or less, n ２０１ Ra's ２０１ and n ２０２ Ra's ２０２ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In 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. 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. 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.

7. The electrophotographic photoreceptor according to claim 1, wherein the charge transport material includes at least one selected from the group consisting of a compound represented by the following formula (D1) (D1), a compound represented by the following formula (D2) (D2), a compound represented by the following formula (D3) (D3), and a compound represented by the following formula (D4) (D4). 【Transformation 5】 In equation (D1), Ar Ｔ１ Ar Ｔ２ and Ar Ｔ３ Each is independently an aryl group, -C ６ H ４ -C(R Ｔ４ ) = C(R Ｔ５ )(R Ｔ６ ) or -C ６ H ４ -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 connected by -C(R ５１ )(R ５２ )- and -C(R ６１ ) = C(R ６２ ) - may be linked by at least one divalent group selected from the group consisting of . 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. In equation (D2), R Ｔ２０１ , R Ｔ２０２ , R Ｔ２１１ and R Ｔ２１２ 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 Ｔ２１ ) = C(R Ｔ２２ )(R Ｔ２３ ) or -CH=CH-CH=C(R Ｔ２４ )(R Ｔ２５ ) is R Ｔ２１ , R Ｔ２２ , R Ｔ２３ , R Ｔ２４ and R Ｔ２５ Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. Ｔ２２１ and R Ｔ２２２ 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. Tm1, Tm2, ​​Tn1, and Tn2 are each independently 0, 1, or 2. In formula (D3), 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. In formula (D4), R Ｔ４０１ , R Ｔ４０２ , R Ｔ４１１ and R Ｔ４１２ 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 Ｔ４１ )=C(R Ｔ４２ )(R Ｔ４３ ) or -CH=CH-CH=C(R Ｔ４４ )(R Ｔ４５ ). R Ｔ４１ , R Ｔ４２ , R Ｔ４３ , R Ｔ４４ and R Ｔ４５ are each independently a hydrogen atom, an alkyl group or an aryl group. R Ｔ４２１ , R Ｔ４２２ and R Ｔ４３１ 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. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2 and Tv1 are each independently 0, 1 or 2.

8. The electrophotographic photoreceptor is provided according to any one of claims 1 to 7, A process cartridge that is attached to and detached from an image forming apparatus.

9. The process cartridge according to claim 8, further comprising a cleaning device having a cleaning blade that contacts the surface of the electrophotographic photoreceptor and cleans the surface of the electrophotographic photoreceptor.

10. An electrophotographic photoreceptor according to any one of claims 1 to 7, A charging device for charging the surface of the electrophotographic photoreceptor, An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, A developing apparatus that develops an electrostatic latent image formed on the surface of an electrophotographic photoreceptor using a developer containing toner to form a toner image, A transfer device for transferring the toner image onto the surface of a recording medium, An image forming apparatus equipped with the following features.

11. The image forming apparatus according to claim 10, further comprising a cleaning device having a cleaning blade that contacts the surface of the electrophotographic photoreceptor and cleans the surface of the electrophotographic photoreceptor.

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