Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that excels at suppressing localized deterioration of electrical properties after long-term printing. [Solution] An electrophotographic photoreceptor comprising a conductive substrate and a laminated photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate, wherein the charge transport layer contains a polyarylate resin having dicarboxylic acid units of formula (A) and diol units of formula (B) below, the charge generating layer contains chlorogallium phthalocyanine as a charge generating material, and the value of the binder resin content / total content of binder resin and charge generating material in the charge generating layer is greater than 0.4 and less than 0.7. JPEG2026084597000056.jpg3585

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 having a charge generation layer and a charge transport layer in that order on a support, wherein at least one of the binder resins in the charge transport layer is a polyarylate resin, and the thickness of the charge transport layer is 28 μm or more, characterized in that the charge generation layer contains gallium phthalocyanine, and the charge transport layer contains an antioxidant in an amount of 5% by mass or more and less than 40% by mass relative to the total mass of the binder resin in the charge transport layer.

[0003] Patent Document 2 discloses an electrophotographic photoreceptor comprising a conductive substrate and a laminated photosensitive layer disposed on the conductive substrate, the laminate having a charge generating layer and a charge transport layer, wherein the charge transport layer contains a charge transport material, a polyester resin and a polycarbonate resin, and the polyester resin contains a polyester resin of a specific structure.

[0004] Patent Document 3 discloses an electrophotographic photoreceptor having at least two layers, a charge generation layer and a charge transport layer, on a conductive support, characterized in that the charge generation layer contains a phthalocyanine pigment and a polyarylate resin of a specific structure. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2005-164936 [Patent Document 2] Japanese Patent Publication No. 2024-11918 [Patent Document 3] Japanese Patent Publication No. 2003-202683 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide an electrophotographic photoreceptor that exhibits superior suppression of local deterioration of electrical properties after long-term printing compared to a case where the charge transport layer contains a polyarylate resin having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B), the charge generation layer contains chlorogallium phthalocyanine as a charge generation material, and the value of the binder resin content / total content of the binder resin and charge generation material in the charge generation layer is 0.4 or less or 0.7 or more. [Means for solving the problem]

[0007] Means for solving the aforementioned problem include the following embodiments. <1> An electrophotographic photoreceptor comprising a conductive substrate and a laminated photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate, wherein the charge transport layer contains a polyarylate resin having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by formula (B), the charge generating layer contains chlorogallium phthalocyanine as a charge generating material, and the value of the binder resin content / total content of binder resin and charge generating material in the charge generating layer is greater than 0.4 and less than 0.7.

[0008] [ka]

[0009] In equation (A), Ar A1 and Ar A2 Each of these is an aromatic ring which may independently have substituents, L A is a single bond or a divalent linking group, n A1 It is 0, 1, or 2. In equation (B), Ar B1 and Ar B2 Each of these is an aromatic ring which may independently have substituents, L Bis a single bond, an oxygen atom, a sulfur atom or -C(Rb 1 )(Rb 2 )-, and n B1 is 0, 1 or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may combine to form a cyclic alkyl group.

[0010] <2> The electrophotographic photoreceptor according to <1>, wherein the value of the content of the binder resin / the total content of the binder resin and the charge generating material in the charge generating layer is greater than 0.43 and less than 0.60. <3> The electrophotographic photoreceptor according to <1> or <2>, wherein the dicarboxylic acid unit represented by the formula (A) contains at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by the following formula (A1), a dicarboxylic acid unit (A2) represented by the formula (A2), a dicarboxylic acid unit (A3) represented by the formula (A3), a dicarboxylic acid unit (A4) represented by the formula (A4) and a dicarboxylic acid unit (A5) represented by the formula (A5).

[0011]

Chemical formula

[0012] In the formula (A1), n 101 is an integer of 0 or more and 4 or less, and n 101 Ra 101 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms or an alkoxy group having 1 to 6 carbon atoms. In the formula (A2), n 201 and n 202 are each independently an integer of 0 or more and 4 or less, and n 201 Ra 201 and n 202 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.

[0013] <4> The diol unit represented by formula (B) includes at least one selected from the group consisting of the following: diol unit represented by formula (B1) (B1), diol unit represented by formula (B2) (B2), diol unit represented by formula (B3) (B3), diol unit represented by formula (B4) (B4), diol unit represented by formula (B5) (B5), diol unit represented by formula (B6) (B6), diol unit represented by formula (B7) (B7), and diol unit represented by formula (B8) (B8). <1> ~ <3> An electrophotographic photoreceptor as described in any one of the following.

[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 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 Rb904 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 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.

[0017] <5> The binder resin in the charge generation layer is a vinyl acetate resin or a polyvinyl butyral resin. <1> ~ <4> An electrophotographic photoreceptor as described in any one of the following. <6> The binder resin in the charge generation layer is a vinyl chloride-vinyl acetate copolymer or a polyvinyl butyral resin. <1> ~ <5> An electrophotographic photoreceptor as described in any one of the following. <7> The charge transport layer further contains polycarbonate resin. <1> ~ <6> An electrophotographic photoreceptor as described in any one of the following. <8> <1> ~ <7> A process cartridge equipped with an electrophotographic photoreceptor as described in any one of the following, which can be attached to and detached from an image forming apparatus. <9> <1> ~ <7> An image forming apparatus comprising: an electrophotographic photoreceptor as described in any one of the above; 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. [Effects of the Invention]

[0018] <1> According to the present invention, an electrophotographic photoreceptor is provided in which the charge transport layer contains a polyarylate resin having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B) below, the charge generating layer contains chlorogallium phthalocyanine as a charge generating material, and the value of the binder resin content / total content of the binder resin and charge generating material in the charge generating layer is 0.4 or less or 0.7 or more, compared to the case in which the local deterioration of electrical properties after long-term printing is suppressed. <2> According to the present invention, an electrophotographic photoreceptor is provided that exhibits superior ability to suppress local deterioration of electrical properties after long-term printing compared to cases where the value of the binder resin content / total content of the binder resin and charge generating material in the charge generating layer is 0.43 or less or 0.60 or more. <3> According to the invention, an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to a case in which the dicarboxylic acid unit represented by formula (A) does not include at least one selected from the group consisting of the dicarboxylic acid unit represented by formula (A1) (A1), the dicarboxylic acid unit represented by formula (A2) (A2), the dicarboxylic acid unit represented by formula (A3) (A3), the dicarboxylic acid unit represented by formula (A4) (A4), and the dicarboxylic acid unit represented by formula (A5) (A5). <4> According to the invention, compared to the case where the diol unit represented by formula (B) does not include at least one selected from the group consisting of the diol unit represented by formula (B1), the diol unit represented by formula (B2), the diol unit represented by formula (B3), the diol unit represented by formula (B4), the diol unit represented by formula (B5), the diol unit represented by formula (B6), the diol unit represented by formula (B7), and the diol unit represented by formula (B8), an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing. <5> According to the invention, an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to a case where the binder resin in the charge generation layer is a polyester resin. <6> According to the invention, an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to a case where the binder resin in the charge generation layer is a vinyl acetate homopolymer. <7> According to the invention, an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to a case in which the charge transport layer further does not contain polycarbonate resin. <8> or <9> According to the present invention, the charge transport layer of the electrophotographic photoreceptor contains a polyarylate resin having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B) below, and the charge generation layer contains chlorogallium phthalocyanine as a charge generation material, and compared to the case where the value of the binder resin content / total content of the binder resin and charge generation material in the charge generation layer is 0.4 or less or 0.7 or more, a process cartridge or image forming apparatus is provided that exhibits superior suppression of local deterioration of electrical properties after long-term printing. [Brief explanation of the drawing]

[0019] [Figure 1] This is a partial cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to this embodiment. [Figure 2] This is a schematic diagram showing an example of an image forming apparatus according to this embodiment. [Figure 3] This is a schematic diagram showing another example of the image forming apparatus according to this embodiment. [Modes for carrying out the invention]

[0020] The following describes in detail an embodiment that is an example of the present invention. In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise within this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described within this specification, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that the purpose of the process is achieved. When embodiments are described herein with reference to the drawings, the configuration of such embodiments is not limited to that 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. In this specification, each component may contain multiple types of the corresponding substance. In this embodiment, when referring to the amount of each component in the composition, if there are multiple types of the substance corresponding to each component in the composition, unless otherwise specified, it refers to the total amount of those multiple types of substances present in the composition. In this specification, each component may contain multiple types of particles. When multiple types of particles corresponding to each component are present in a 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. In this specification, alkyl groups and alkylene groups include linear, branched, and cyclic groups unless otherwise specified. In this specification, organic groups, aromatic rings, linking groups, alkyl groups, alkylene groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, etc., may have hydrogen atoms in the group substituted with halogen atoms. In this specification, when compounds are shown by structural formulas, the symbols representing carbon atoms and hydrogen atoms (C and H) in the hydrocarbon group and / or hydrocarbon chain may be omitted. In this specification, the term "constituent unit" of a copolymer or resin is synonymous with "monomer unit." In this specification, ppm stands for parts per million and is based on mass.

[0021] <Electrophotographic photoconductor> The electrophotographic photoreceptor according to this embodiment includes a conductive substrate and a laminated photosensitive layer disposed on the conductive substrate and having a charge generation layer and a charge transport layer. The charge transport layer contains a polyarylate resin having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by formula (B). The charge generation layer contains chlorogallium phthalocyanine as a charge generation material. The value of the content of the binder resin / the total content of the binder resin and the charge generation material in the charge generation layer is greater than 0.4 and less than 0.7.

[0022]

Chemical formula

[0023] In formula (A), Ar A1 and Ar A2 are each independently an aromatic ring which may have a substituent, and L A is a single bond or a divalent linking group, and n A1 is 0, 1 or 2. In formula (B), Ar B1 and Ar B2 are each independently an aromatic ring which may have a substituent, and L B is a single bond, an oxygen atom, a sulfur atom or -C(Rb 1 )(Rb 2 )-, and n B1 is 0, 1 or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may combine with each other to form a cyclic alkyl group.

[0024] Since the polyarylate resin is synthesized using acid chloride, acid chloride itself or deactivated dicarboxylic acid tends to remain as impurities. The presence of impurities such as acid chlorides and dicarboxylic acids is presumed to interact with the charge-generating material, thereby locally degrading the electrical properties. Furthermore, even if there are no problems initially, the movement of acidic components near the charge-generating material over time and their interaction is also considered to be one of the causes of locally degrading electrical properties. Hydroxygallium phthalocyanine, a charge-generating material, is thought to readily interact with acidic components, leading to a deterioration of its electrical properties. On the other hand, chlorogallium phthalocyanine is thought to have less interaction with acidic components, remaining stable over time and maintaining stable electrical properties over the long term. Furthermore, polyarylate resins using phthalic acid are presumed to readily interact with chlorogallium phthalocyanine due to the high acidity of phthalic acid, which is thought to cause deterioration of electrical properties. Furthermore, if the ratio of binder resin content to the total content of binder resin and charge generating material in the charge generating layer is 0.4 or less, it is estimated that the proportion of charge generating material interacting with the acid component will be large, leading to a deterioration of local electrical properties. If the ratio of binder resin content to the total content of binder resin and charge generating material is 0.7 or more, it is thought that the proportion of charge generating material interacting with the acid component will be small, but the impact of local deterioration of electrical properties when interaction occurs will be large, leading to a deterioration of electrical properties. In the electrophotographic photoreceptor according to this embodiment, the charge transport layer contains a polyarylate resin having dicarboxylic acid units (A) and diol units (B), and the charge generation layer contains chlorogallium phthalocyanine. The value of the binder resin content / total content of binder resin and charge generation material in the charge generation layer is greater than 0.4 and less than 0.7, thereby suppressing the interaction between the charge generation material and the acid component, and providing excellent suppression of local deterioration of electrical properties after long-term printing.

[0025] The electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") according to this embodiment comprises a stacked photoreceptor having a charge generation layer and a charge transport layer disposed on the conductive substrate. The electrophotographic photoreceptor according to this embodiment may further include other layers (for example, an undercoat layer, an intermediate layer).

[0026] Figure 1 is a schematic partial cross-sectional view showing an example of the layer structure of a photoreceptor according to this embodiment. The photoreceptor 10A shown in Figure 1 has a stacked photoreceptor layer. The photoreceptor 10A has a structure in which a base layer 2, a charge generation layer 3, and a charge transport layer 4 are stacked in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute the photoreceptor layer 5 (a so-called functionally separated photoreceptor layer). The photoreceptor 10A may have an intermediate layer (not shown) between the base layer 2 and the charge generation layer 3. The base layer 2 may or may not be present.

[0027] The following provides a detailed explanation of each layer of the photoreceptor.

[0028] [Charge transport layer] The charge transport layer in the electrophotographic photoreceptor according to this embodiment contains a polyarylate resin having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by the following formula (B).

[0029] Polyarylate resins improve the wear resistance of the charge transport layer because the resin molecules are bound together by intermolecular forces through the stacking of aromatic rings. A polycondensate of bisphenols and aromatic divalent carboxylic acids is preferred as the polyarylate resin. A preferred form of polyarylate resin is the polyarylate resin (PA) described later.

[0030] The polyarylate resin contained in the charge transport layer includes a polyarylate resin having at least dicarboxylic acid units (A) and diol units (B). In this disclosure, the polyarylate resin is referred to as polyarylate resin (PA).

[0031] The dicarboxylic acid unit (A) is a constituent unit represented by the following formula (A).

[0032] [ka]

[0033] In equation (A), ArA1 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 2Each 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] From the viewpoint of suppressing local deterioration of electrical properties after long-term printing, the dicarboxylic acid unit (A) preferably includes at least one selected from the group consisting of dicarboxylic acid unit (A1) represented by formula (A1), dicarboxylic acid unit (A2) represented by formula (A2), dicarboxylic acid unit (A3) represented by formula (A3), dicarboxylic acid unit (A4) represented by formula (A4), and dicarboxylic acid unit (A5) represented by formula (A5). It is more preferable that the dicarboxylic acid unit (A) includes at least one selected from the group consisting of dicarboxylic acid unit (A2), dicarboxylic acid unit (A3), and dicarboxylic acid unit (A4), and even more preferable that it includes dicarboxylic acid unit (A2).

[0043] [ka]

[0044] 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.

[0045] [ka]

[0046] 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 201It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 202 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0047] [ka]

[0048] In equation (A3), n 301 and n 302 Each of these is an independent integer between 0 and 4, and n 301 Individual Ra 301 and n 302 Individual Ra 302 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 301 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 302 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0049] [ka]

[0050] 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. It is even more preferable that this be the case.

[0051] [ka]

[0052] In equation (A5), n 501 , n 502 and n 503 Each of these is an independent integer between 0 and 4, and n 501 Individual Ra 501 , n 502 Individual Ra 502 and n 503 Individual Ra 503 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 501 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 502 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 503 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0053] Ra in equation (A1) 101 Ra in equation (A2) 201 and Ra 202 Ra of formula (A3) 301 and Ra 302 Ra of formula (A4) 401 Also, Ra in formula (A5) 501 Ra 502 and Ra 503 Since the specific form and preferred form are the same, hereinafter, Ra 101 Ra 201 Ra 202 Ra 301 Ra 302 Ra 401 Ra 501 Ra 502 and Ra 503 We will refer to them collectively as "Ra" and explain them accordingly.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] Below are examples of dicarboxylic acid units (A1) (A1-1) to (A1-9). Dicarboxylic acid units (A1) are not limited to these examples.

[0058] [ka]

[0059] Below are examples of dicarboxylic acid units (A2) (A2-1) to (A2-3). Dicarboxylic acid units (A2) are not limited to these examples.

[0060] [ka]

[0061] The following are specific examples of dicarboxylic acid units (A3), namely (A3-1) and (A3-2). However, dicarboxylic acid units (A3) are not limited to these examples.

[0062] [ka]

[0063] Specific examples of the dicarboxylic acid unit (A4) are shown below as dicarboxylic acid units (A4-1) to (A4-3). The dicarboxylic acid unit (A4) is not limited thereto.

[0064] [Chemical formula]

[0065] Specific examples of the dicarboxylic acid unit (A5) are shown below as dicarboxylic acid units (A5-1) to (A5-4). The dicarboxylic acid unit (A5) is not limited thereto.

[0066] [Chemical formula]

[0067] The dicarboxylic acid unit (A) preferably contains at least one selected from the group consisting of (A1-1), (A1-7), (A2-3), (A3-2), and (A4-3) of the above specific examples, more preferably contains at least one selected from the group consisting of (A2-3), (A3-2), and (A4-3), and even more preferably contains at least (A2-3).

[0068] The dicarboxylic acid unit (A) contained in the polyarylate resin (PA) may be one kind or two or more kinds.

[0069] The mass ratio of the dicarboxylic acid unit (A) in the polyarylate resin (PA) is preferably 15% by mass or more and 60% by mass or less. When the mass ratio of the dicarboxylic acid unit (A) is 15% by mass or more, the wear resistance of the charge transport layer is good. From this viewpoint, the mass ratio of the dicarboxylic acid unit (A) is more preferably 20% by mass or more, and even more preferably 25% by mass or more. When the mass ratio of the dicarboxylic acid unit (A) is 60% by mass or less, peeling of the charge transport layer can be suppressed. From this viewpoint, the mass ratio of the dicarboxylic acid unit (A) is more preferably 55% by mass or less, and even more preferably 50% by mass or less.

[0070] The polyarylate resin (PA) may contain other dicarboxylic acid units in addition to the dicarboxylic acid unit (A). Examples of the other dicarboxylic acid units include aliphatic dicarboxylic acid (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenyl succinic acid, adipic acid, sebacic acid) units, alicyclic dicarboxylic acid (e.g., cyclohexanedicarboxylic acid) units, and lower (e.g., having 1 to 5 carbon atoms) alkyl ester units of these. These dicarboxylic acid units contained in the polyarylate resin (PA) may be one kind or two or more kinds.

[0071] The diol unit (B) is a structural unit represented by the following formula (B).

[0072]

Chemical formula

[0073] In formula (B), Ar B1 and Ar B2 are each independently an aromatic ring which may have a substituent, L B is a single bond, an oxygen atom, a sulfur atom or -C(Rb 1 )(Rb 2 )-, n B1 is 0, 1 or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may combine to form a cyclic alkyl group.

[0074] Ar B1 The aromatic ring of may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, and a benzene ring and a naphthalene ring are preferred.

[0075] 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.

[0076] 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.

[0077] Ar B2 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. B2 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] From the viewpoint of suppressing local deterioration of electrical properties after long-term printing, the diol unit (B) preferably includes at least one selected from the group consisting of the diol unit (B1) represented by formula (B1), the diol unit (B2) represented by formula (B2), the diol unit (B3) represented by formula (B3), the diol unit (B4) represented by formula (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).

[0082] The diol unit (B) more preferably includes at least one selected from the group consisting of the diol unit (B1) represented by the following formula (B1), the diol unit (B2) represented by the formula (B2), the diol unit (B4) represented by the formula (B4), the diol unit (B5) represented by the formula (B5), and the diol unit (B6) represented by the formula (B6). It is even more preferable to include at least one selected from the group consisting of a diol unit represented by the following formula (B1), a diol unit represented by the following formula (B2), a diol unit represented by the following formula (B5), and a diol unit represented by the following formula (B6): It is even more preferable to include at least one selected from the group consisting of a diol unit represented by the following formula (B1), a diol unit represented by the following formula (B2), and a diol unit represented by the following formula (B6): It is most preferable to contain 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 formula (B2).

[0083]

Chem.

[0084] 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.

[0085] Rb 101 The number of carbon atoms of the branched alkyl group having 4 to 20 carbon atoms related to is preferably 4 to 16, more preferably 4 to 12, and still more preferably 4 to 8. Specific examples of Rb 101 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, etc.

[0086]

Chem.

[0087] In formula (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.

[0088] 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.

[0089] [ka]

[0090] 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.

[0091] 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.

[0092] [ka]

[0093] 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.

[0094] 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.

[0095] [ka]

[0096] 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.

[0097] 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, anthracenylmethyl group, and phenylcyclopentylmethyl group.

[0098] [ka]

[0099] In equation (B6), Rb 116 and Rb 216 Each of these is independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, e is an integer between 4 and 6, and Rb406 , Rb 506 , Rb 806 and Rb 906 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0100] 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.

[0101] [ka]

[0102] 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.

[0103] [ka]

[0104] 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.

[0105] 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 "[...]."

[0106] 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.

[0107] 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 "[...]."

[0108] 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.

[0109] 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.

[0110] Rb 400 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0111] 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 "[...]."

[0112] 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.

[0113] 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.

[0114] Rb 500 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0115] 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 "[...]."

[0116] 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.

[0117] 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.

[0118] Rb 800 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0119] 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 "[...]."

[0120] 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.

[0121] 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.

[0122] Rb 900 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0123] The following are specific examples of diol units (B1), specifically (B1-1) to (B1-6). Diol units (B1) are not limited to these examples.

[0124] [ka]

[0125] The following are specific examples of diol units (B2), specifically (B2-1) to (B2-11). Diol units (B2) are not limited to these examples.

[0126] [ka]

[0127] The following are specific examples of diol units (B3), namely (B3-1) to (B3-4). Diol units (B3) are not limited to these examples.

[0128] [ka]

[0129] The following are examples of diol units (B4-1) to (B4-7). Diol units (B4) are not limited to these examples.

[0130] [ka]

[0131] The following are examples of diol units (B5-1) to (B5-6). Diol units (B5) are not limited to these examples.

[0132] [ka]

[0133] The following are specific examples of diol units (B6), namely (B6-1) to (B6-4). Diol units (B6) are not limited to these examples.

[0134] [ka]

[0135] The following are examples of diol units (B7-1) to (B7-3). Diol units (B7) are not limited to these examples.

[0136] [ka]

[0137] The following are specific examples of diol units (B8), namely (B8-1) to (B8-3). Diol units (B8) are not limited to these examples.

[0138] [ka]

[0139] The diol units (B) contained in the polyarylate resin (PA) may be one type or two or more types.

[0140] The mass percentage of diol units (B) in the polyarylate resin (PA) is preferably 25% by mass or more and 80% by mass or less. When the mass percentage of diol units (B) is 25% by mass or more, peeling of the charge transport layer can be suppressed. From this viewpoint, the mass percentage of diol units (B) is more preferably 30% by mass or more, and even more preferably 35% by mass or more. When the mass percentage of diol units (B) is 80% by mass or less, it is possible to maintain solubility in the coating solution for forming the charge transport layer and improve wear resistance. From this viewpoint, the mass percentage of diol units (B) is more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0141] Polyarylate resin (PA) may contain other diol units besides diol unit (B). Examples of other diol units include aliphatic diol units (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) and alicyclic diol units (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A). The polyarylate resin (PA) may contain one or more of these diol units.

[0142] The ends of the polyarylate resin (PA) may be sealed or modified with end-capping agents or molecular weight modifiers used during manufacturing. Examples of end-capping agents or molecular weight modifiers include monohydric phenols, monohydric acid chlorides, monohydric alcohols, and monohydric carboxylic acids. Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m Examples include -phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, and 2-phenyl-2-(3-hydroxyphenyl)propane. Examples of monovalent acid chlorides include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenylchloroformate, acetate chloride, butyrate chloride, octic acid 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.

[0143] The weight-average molecular weight of the polyarylate resin (PA) is preferably 30,000 to 300,000, more preferably 40,000 to 250,000, and even more preferably 50,000 to 200,000. The molecular weight of polyarylate resin (PA) is the molecular weight in polystyrene equivalent, measured by GPC (gel permeation chromatography). Tetrahydrofuran is used as the eluent in GPC.

[0144] Polyarylate resins (PA) can be obtained by polycondensation of monomers that give dicarboxylic acid units (A) and monomers that give diol units (B), along with other monomers as needed, using conventional methods. Methods for the polycondensation of monomers include interfacial polymerization, solution polymerization, and melt polymerization. Interfacial polymerization is a polymerization method that obtains polyester by mixing a divalent carboxylic acid halide dissolved in an organic solvent immiscible with water with a divalent alcohol dissolved in an alkaline aqueous solution. Literature on interfacial polymerization includes WMERECKSON, J. Poly. Sci., XL399, 1959, and Japanese Patent Publication No. 40-1959. Because interfacial polymerization is faster than solution polymerization, it can suppress the hydrolysis of divalent carboxylic acid halides, resulting in the acquisition of high molecular weight polyarylate resins (PA).

[0145] Other resins that can be included in the charge transport layer include polyarylate resins other than those mentioned above, polycarbonate resins, polyester resins other than polyarylate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, polysilanes, etc. Two or more resins can be used in any combination from these resins.

[0146] The resin included in the charge transport layer preferably contains at least one of a polyarylate resin and a polycarbonate resin, and more preferably contains both a polyarylate resin and a polycarbonate resin, from the viewpoint of the wear resistance of the charge transport layer and the ability to suppress local deterioration of electrical properties after long-term printing. The form containing both a polyarylate resin and a polycarbonate resin is also preferred from the viewpoint of forming a fine phase separation structure in the charge transport layer.

[0147] From the viewpoint of forming a fine phase separation structure in the charge transport layer, the proportion of polyarylate resin in the total amount of polyarylate resin and polycarbonate resin is preferably 20% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 75% by mass or less, and even more preferably 30% by mass or more and 70% by mass or less.

[0148] As the polycarbonate resin, a polycarbonate resin having continuous structural units with aromatic rings is preferred. In this polycarbonate resin, the resin molecules are bound together by intermolecular forces through the stacking of aromatic rings, improving the abrasion resistance of the charge transport layer. Specifically, a preferred form of the polycarbonate resin is the polycarbonate resin disclosed in Japanese Patent Application Publication No. 2023-121553. A more preferred form of the polycarbonate resin is the polycarbonate resin used in the examples described later.

[0149] As for the combination of polyarylate resin and polycarbonate resin, a combination of resins in which both have a structural unit containing biphenyl represented by the following formula (BP) is preferred.

[0150] [ka]

[0151] In equation (BP), j is an integer between 0 and 4, and j R 1 Each is independently either a methyl group or an ethyl group, k is an integer between 0 and 4, and there are k R 2These are independently either a methyl group or an ethyl group.

[0152] The biphenyl represented by formula (BP) may be the entire structure or a part of the structure obtained by removing the ester bond (-C(=O)O-) or carbonate bond (-OC(=O)O-) from the constituent unit containing the biphenyl represented by formula (BP). In other words, the right and left ends of the biphenyl represented by formula (BP) may be independently directly bonded to an ester bond or a carbonate bond, or they may be bonded to an ester bond or a carbonate bond via other atoms or groups of atoms.

[0153] j is an integer between 0 and 4, preferably between 0 and 3, more preferably between 0 and 2, even more preferably 0 or 1, and particularly preferably 0. If j is an integer greater than or equal to 1, then j R 1 Each of these is independently a methyl group or an ethyl group, and a methyl group is preferred.

[0154] k is an integer between 0 and 4, preferably between 0 and 3, more preferably between 0 and 2, even more preferably 0 or 1, and particularly preferably 0. If k is an integer greater than or equal to 1, then k R 2 Each of these is independently a methyl group or an ethyl group, and a methyl group is preferred.

[0155] The biphenyl represented by formula (BP) is preferably 4,4'-biphenyl in terms of its linkage position in the main chain.

[0156] As for the combination of polyarylate resin and polycarbonate resin, a combination of a polyarylate resin having at least one of dicarboxylic acid units (A2-3) and diol units (B7-1) and a polycarbonate resin having constituent units (Cb7-1) is particularly preferred.

[0157] [ka]

[0158] The charge transport layer preferably further contains a phenolic compound. Examples of phenol compounds included in the charge transport layer include phenol, cresol, catechol, resorcinol, hydroquinone, naphthol, and bisphenol (bisphenol A, AP, AF, B, BP, C, C2, E, F, G, M, S, P, PH, TMC, Z). One phenol compound may be used alone, or two or more may be used in combination.

[0159] Hindered phenol compounds are another example of phenolic compounds. From the viewpoint of suppressing oxidative degradation of the charge transport layer, it is preferable that the phenol compound includes a hindered phenol compound. Hindered phenol compounds are generally compounds in which at least one of the ortho positions of the hydroxyl group of phenol is substituted with a bulky group, and are known to exhibit an antioxidant effect on the composition.

[0160] Examples of hindered phenol compounds include the following: • Alkylated monophenol compounds and their derivatives: e.g., 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, octyl-3,5-di-t-butyl-4-hydroxyhydrocinnamate • Alkylated hydroquinone compounds and their derivatives: e.g., 2,5-di-t-butylhydroquinone, 2,5-di-t-amylhydroquinone • Alkylthiomethylphenol compounds and their derivatives: For example, 2,4-dioctylthiomethyl-6-t-butylphenol, 2,4-dioctylthiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, 2,6-didodecylthiomethyl-4-nonylphenol • Alkylidenebisphenol compounds and their derivatives: e.g., 4,4'-Butylidenebis(6-t-butyl-3-methylphenol), 2,2'-Methylenebis(6-t-butyl-4-methylphenol), 2,2'-Methylenebis(6-t-butyl-4-ethylphenol), 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 3,9-bis[2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane

[0161] Commercially available hindered phenol compounds include ADEKA Corporation's "ADEKA Stab AO-80," "ADEKA Stab AO-60," "ADEKA Stab AO-50," "ADEKA Stab AO-40," "ADEKA Stab AO-30," "ADEKA Stab AO-20," and "ADEKA Stab AO-330," BASF Japan Ltd.'s "Irganox 1010," "Irganox 245," "Irganox 1076," and "Irganox 1520," and Sumitomo Chemical Co., Ltd.'s "Sumilizer GA-80," "Sumilizer GM," and "Sumilizer GS."

[0162] Hindered phenol compounds may be used individually or in combination of two or more.

[0163] The content of the phenol compound in the charge transport layer is preferably 0.1% to 20% by mass, more preferably 0.5% to 10% by mass, and even more preferably 1% to 5% by mass, based on the total mass of the charge transport layer, from the viewpoint of promoting phase separation of two or more types of resins during the formation of the charge transport layer and forming a fine phase separation structure in the charge transport layer.

[0164] The charge transport layer preferably contains 5% by mass or less of fluororesin particles, preferably 1% by mass or less, and more preferably 0% by mass (i.e., it does not contain fluororesin particles). Given the high likelihood of increased regulations on the manufacture and use of organofluorine compounds in the future, the above-mentioned range for the content of fluororesin particles is preferable.

[0165] The charge transport layer preferably contains a charge transport material. Examples of charge transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds, which are electron transport compounds. Other examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used individually or in combination of two or more, but are not limited to these.

[0166] The charge transport layer may be a layer containing a polymer charge transport material. Examples of polymeric charge transport materials include known chemical substances with charge transport properties such as poly-N-vinylcarbazole and polysilane. For example, polyester-based polymeric charge transport materials are preferred. Polymeric charge transport materials may be used alone or in combination with a binder resin.

[0167] 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.

[0168] From the viewpoint of charge mobility, the charge transport material preferably contains at least one selected from the group consisting of a chemical substance (C1) represented by the following formula (C1), a chemical substance (C2) represented by the formula (C2), a chemical substance (C3) represented by the formula (C3), and a chemical substance (C4) represented by the formula (C4).

[0169] [ka]

[0170] In equation (C1), Ar T1 Ar T2 and Ar T3 Each is independently an aryl group, -C6H4-C(R T4 )=C(RT5 )(R T6 ) or -C6H4-CH=CH-CH=C(R T7 )(R T8 ) is R T4 , R T5 , R T6 , R T7 and R T8 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T5 and R T6 When it is an aryl group, the aryl groups are -C(R 51 )(R 52 )-and / or-C(R 61 )=C(R 62 )- may be linked by a divalent group. R 51 , R 52 , R 61 and R 62 Each of these is independently either a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0171] The group in formula (C1) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0172] As for the chemical substance (C1), from the viewpoint of charge mobility, it is an aryl group or -C6H4-CH=CH-CH=C(R T7 )(R T8 A chemical substance having at least one of the following is preferred, and a chemical substance (C'1) represented by the following formula (C'1) is more preferred.

[0173] [ka]

[0174] In equation (C'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.

[0175] [ka]

[0176] In equation (C2), 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.

[0177] The group in formula (C2) 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.

[0178] As for the chemical substance (C2), from the viewpoint of charge mobility, alkyl groups, aryl groups, or -CH=CH-CH=C(R T24 )(R T25A chemical substance having at least one alkyl group, aryl group, or -CH=CH-CH=C(R T24 )(R T25 A chemical substance having two of these is more preferable.

[0179] [ka]

[0180] In equation (C3), 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.

[0181] The group in formula (C3) 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.

[0182] [ka]

[0183] In equation (C4), R T401 , R T402 , R T411 and R T412 Each of these is independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, and -C(R T41 )=C(R T42 )(R T43 ) or -CH=CH-CH=C(R T44 )(R T45 ) is R T41 , R T42 , R T43 , R T44 and R T45 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T421 , R T422 and R T431 Each of these is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 are each independently 0, 1, or 2.

[0184] The group in formula (C4) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0185] 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.

[0186] The charge transport layer may also contain other known additives.

[0187] The formation of the charge transport layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of a charge transport layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0188] 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.

[0189] 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.

[0190] The thickness of the charge transport layer should be set according to the function of that layer. The thickness of the charge transport layer is preferably 5 μm to 50 μm, more preferably 8 μm to 45 μm, and even more preferably 10 μm to 40 μm.

[0191] [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.

[0192] In the charge generation layer, the value of the binder resin content / total content of binder resin and charge generation material is greater than 0.4 and less than 0.7. From the viewpoint of suppressing local deterioration of electrical properties after long-term printing, it is preferably 0.41 or more and 0.65 or less, more preferably greater than 0.43 and less than 0.60, and particularly preferably greater than 0.43 and less than 0.50.

[0193] The charge-generating material contains chlorogallium phthalocyanine. Other known charge-generating materials may be used in combination, but it is preferable not to use them in combination from the viewpoint of suppressing local deterioration of electrical properties after long-term printing.

[0194] The binder resin used in the charge generation layer can be selected from a wide range of insulating resins, or it may be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (such as polycondensates of bisphenols and aromatic divalent carboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinylpyrrolidone resin. Here, "insulating properties" refer to a volume resistivity of 1 × 10⁻⁶. 13 This refers to a value of Ω·cm or greater. In particular, from the viewpoint of suppressing local deterioration of electrical properties after long-term printing, the binder resin is preferably a vinyl acetate resin or a polyvinyl butyral resin, more preferably a vinyl chloride-vinyl acetate copolymer or a polyvinyl butyral resin, and especially preferably a vinyl chloride-vinyl acetate copolymer. These binder resins can be used individually or in combination of two or more types.

[0195] The charge generation layer may also contain other known additives.

[0196] The formation of the charge generation layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of a coating solution for forming a charge generation layer 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 a charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when using fused ring aromatic pigments or perylene pigments as the charge generation material.

[0197] Solvents for preparing the coating solution for forming the charge generation layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, 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.

[0198] Methods for dispersing particles (e.g., charge-generating material) 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, in which the dispersion is dispersed by liquid-liquid collisions or liquid-wall collisions under high pressure, and penetration methods, in which the dispersion is dispersed by penetrating fine channels under high pressure. During 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.

[0199] 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.

[0200] The thickness of the charge generation layer is preferably set within the range of 0.1 μm to 5.0 μm, and more preferably within the range of 0.2 μm to 2.0 μm.

[0201] [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 1 × 10⁻⁶. 13 This refers to a value less than Ω·cm.

[0202] 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. When non-interfering light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for a longer lifespan because it suppresses the occurrence of defects due to surface irregularities of the conductive substrate.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0210] As for inorganic particles, for example, powder resistance (volume resistivity) 1 × 10 2 Ω cm or more 1×10 11 Examples include inorganic particles with a size of Ω·cm or less. Among these, suitable inorganic particles having the above-mentioned resistance values ​​include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0211] 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).

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry or wet method.

[0218] 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.

[0219] 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.

[0220] Examples of electron-accepting compounds include electron-transporting substances such as compounds having anthraquinone structures; quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone; and benzophenone compounds. In particular, 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. Specifically, examples of preferred compounds include anthraquinone, alizarin, quinizalin, anthralphine, purpurin, and their derivatives.

[0221] 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.

[0222] Methods for attaching electron-accepting compounds to the surface of inorganic particles include, for example, dry methods or wet methods.

[0223] 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.

[0224] The wet method involves dispersing inorganic particles in a solvent using, for example, a stirrer, ultrasonic disperser, sand mill, attritor, or ball mill, while adding an electron-accepting compound. After stirring or dispersion, the solvent is removed, and the electron-accepting compound adheres to the surface of the inorganic particles. Solvent removal methods include, for example, filtration or distillation. After solvent removal, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained. In the wet method, the water content of the inorganic particles may be removed before adding the electron-accepting compound. Examples of this include removing water while stirring and heating in the solvent, or removing water by azeotrope with the solvent.

[0225] The electron-accepting compound may be applied before or after surface treatment with a surface treatment agent to the inorganic particles, or it may be applied simultaneously with the surface treatment with the surface treatment agent.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] Examples of aluminum chelating compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0234] These additives may be used individually or as a mixture or polycondensate of multiple compounds.

[0235] 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.

[0236] The formation of the undercoat is not particularly limited, and 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.

[0237] 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 cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0238] 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.

[0239] 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.

[0240] The thickness of the undercoat layer is preferably set to a range of 15 μm or more, and more preferably within the range of 20 μm to 50 μm.

[0241] [Middle class] 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.

[0242] Among these, the intermediate layer is preferably a layer containing an organometallic compound that contains zirconium atoms or silicon atoms.

[0243] The formation of the intermediate layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of an intermediate layer-forming coating solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary. Conventional methods such as immersion coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating are used to form the intermediate layer.

[0244] The thickness of the intermediate layer is preferably set in the range of 0.1 μm to 3 μm. The intermediate layer may also be used as a base layer.

[0245] <Image forming apparatus, process cartridge> The image forming apparatus according to this embodiment comprises an electrophotographic photoreceptor, a charging device for charging the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, a transfer device for transferring the toner image to the surface of a recording medium, and a cleaning device for cleaning the surface of the electrophotographic photoreceptor. The electrophotographic photoreceptor according to this embodiment is used as the electrophotographic photoreceptor.

[0246] In the image forming apparatus according to this embodiment, the cleaning apparatus has a cleaning blade that contacts the outer surface of the photoreceptor, and the cleaning blade cleans the surface of the photoreceptor after the toner image has been transferred and before it has been charged.

[0247] The image forming apparatus according to this embodiment includes known image forming apparatuses such as: an apparatus equipped with a fixing device for fixing a toner image transferred to the surface of a recording medium; a direct transfer apparatus for directly transferring a toner image formed on the surface of an electrophotographic photoreceptor to a recording medium; an intermediate transfer apparatus for first transferring a toner image formed on the surface of an electrophotographic photoreceptor to the surface of an intermediate transfer body, and secondarily transferring the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium; an apparatus equipped with a static elimination device for irradiating the surface of the electrophotographic photoreceptor with static elimination light to eliminate static charge after the transfer of the toner image and before charging; and an apparatus equipped with an electrophotographic photoreceptor heating member for raising the temperature of the electrophotographic photoreceptor and reducing the relative temperature.

[0248] 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.

[0249] 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).

[0250] In the image forming apparatus according to this embodiment, for example, the portion comprising the electrophotographic photoreceptor may be a cartridge structure (process cartridge) that can be attached to and detached from the image forming apparatus. As the process cartridge, for example, a process cartridge comprising the electrophotographic photoreceptor according to this embodiment is preferably used. In addition to the electrophotographic photoreceptor, the process cartridge may also include at least one selected from the group consisting of, for example, a charging device, an electrostatic latent image forming device, a developing device, and a transfer device.

[0251] The following is an example of an image forming apparatus according to this embodiment, but it is not limited to this example. The main parts shown in the figure will be described, and the descriptions of other parts will be omitted.

[0252] Figure 2 is a schematic diagram showing an example of an image forming apparatus according to this embodiment. As shown in Figure 2, the image forming apparatus 100 according to this embodiment includes a process cartridge 300 equipped with an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming apparatus), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is positioned to expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, and the transfer device 40 is positioned opposite the electrophotographic photoreceptor 7 via the intermediate transfer body 50, with a portion of the intermediate transfer body 50 in contact with the electrophotographic photoreceptor 7. Although not shown, the apparatus also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) are examples of transfer devices.

[0253] In Figure 2, the process cartridge 300 integrally supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging device), a developing device 11 (an example of a developing device), and a cleaning device 13 (an example of a cleaning device) within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is positioned to contact the surface of the electrophotographic photoreceptor 7. The cleaning member may be a conductive or insulating fibrous member, rather than a cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

[0254] Figure 2 shows an example of an image forming apparatus that includes a fibrous member 132 (roll-shaped) for supplying lubricant 14 to the surface of the electrophotographic photoreceptor 7, and a fibrous member 133 (flat brush-shaped) for assisting cleaning. These can be arranged as needed.

[0255] The following describes the various components of the image forming apparatus according to this embodiment.

[0256] -Charging device- The charging device 8 may be a contact-type charging device in which the charging member contacts the outer surface of the photoreceptor, or a non-contact-type charging device in which the charging member does not contact the outer surface of the photoreceptor. The effect of the image forming apparatus according to this embodiment (less likely to cause contamination of the charging member over a long period of time) is particularly pronounced in the contact-type charging device.

[0257] As the charging device 8, for example, contact-type charging members using conductive or semiconductive charging rollers, charging brushes, charging films, charging rubber blades, charging tubes, etc. are used. Non-contact roller chargers, known chargers such as scorotron chargers and corotron chargers that utilize corona discharge are also used.

[0258] -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.

[0259] -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.

[0260] The developer used in the developing device 11 may be a one-component developer consisting of toner alone, or a two-component developer containing toner and a carrier. Furthermore, the developer may be magnetic or non-magnetic. Known developers can be used.

[0261] -Cleaning device- The cleaning device 13 uses a cleaning blade system equipped with a cleaning blade 131. In addition to the cleaning blade system, a fur brush cleaning system or a developing and cleaning system may also be used.

[0262] -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.

[0263] -Intermediate Transcript- As the intermediate transfer body 50, a belt-shaped material (intermediate transfer belt) containing semiconducting polyimide, polyamide-imide, polycarbonate, polyarylate, polyester, rubber, etc. is used. In addition to the belt shape, a drum-shaped intermediate transfer body may also be used.

[0264] Figure 3 is a schematic diagram showing another example of the image forming apparatus according to this embodiment. The image forming apparatus 120 shown in Figure 3 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one electrophotographic photoreceptor is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem type. [Examples]

[0265] 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.

[0266] <Synthesis of polyarylate resin> Polyarylate resins PA1, PA2, and PA8 were synthesized. Table 1 shows the units and composition of polyarylate resin. A2-3 and others listed in Table 1 are specific examples of the dicarboxylic acid unit (A) described above. Table 1 shows examples of B1-2, etc., which are specific examples of the diol unit (B) described above.

[0267] [Table 1]

[0268] <Manufacturing of photoreceptors> The following materials were prepared to form the charge transport layer. ·Charge transport material CTM-1 ·Charge transport material CTM-2

[0269] [ka]

[0270] • Polycarbonate resin PC1: The following compound, viscosity-average molecular weight 50,000, the values ​​in the following formula indicate molar ratios.

[0271] [ka]

[0272] • Polycarbonate resin PC3: A polymer compound having repeating units represented by the following formula (viscosity-average molecular weight: 40,000)

[0273] [ka]

[0274] • Polyvinyl butyral resin: Viscosity-average molecular weight 66,000, S-REC BH-S, manufactured by Sekisui Chemical Co., Ltd. • Phenolic compound pH3: ADEKA stub AO-80, manufactured by ADEKA Corporation

[0275] (Example 1) -Formation of the lower layer- 3.5 parts of butyral resin (product name: S-Rec BM-1, manufactured by Sekisui Chemical Co., Ltd.) and 41 parts of methyl ethyl ketone were mixed and dissolved. 10 parts of a curing agent (blocked isocyanate, product name: Sumijoule 3175, manufactured by Sumitomo Bayer Urethane Co., Ltd.), 45.5 parts of zinc oxide (product name: SMZ-017N, manufactured by Teika Co., Ltd.) surface-treated with a silane coupling agent (product name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.27 parts of the compound listed below were added and stirred. The mixture was then dispersed for 2 hours using 1 mm diameter glass beads in a sand mill. Furthermore, 0.01 parts of dioctyl tin dilaurate and 2 parts of silicone resin particles (product name: Tospar 145, manufactured by GE Toshiba Silicone Co., Ltd.) were added and stirred to obtain a coating solution for forming the undercoat layer. A coating solution for forming the undercoat layer was applied to the outer surface of the conductive substrate by immersion coating, and drying and curing was performed at 170°C for 40 minutes to form an undercoat layer with a thickness of 20 μm.

[0276] [ka]

[0277] -Formation of a charge generation layer- Chlorogallium phthalocyanine (using CuKα characteristic X-rays) as a charge generation material. The linear diffraction spectrum has diffraction peaks at Bragg angles (2θ±0.2°) at least 7.4°, 16.6°, 25.5°, and 28.3°. A mixture consisting of 14 parts of (the substance), 12 parts of vinyl chloride / vinyl acetate copolymer resin (product name: VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed for 4 hours using glass beads with a diameter of 1 mm in a sand mill. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion and stirred to obtain a coating solution for forming the charge generation layer. The coating solution for forming the charge generation layer was immersed and coated onto the undercoat, and dried at room temperature to form a charge generation layer with a thickness of 0.25 μm.

[0278] -Formation of a charge transport layer- ·Charge transport material CTM-1: 47 parts ·Charge transport material CTM-2: 20 parts • Polyarylate resin (PA1): 29 parts (30% of total resin) • Polycarbonate resin (PC1): 67 parts (70% of total resin) • Phenolic compounds (pH 3): 4.9 parts Tetrahydrofuran: 570 parts • Toluene: 57 parts The above materials were stirred and mixed to obtain a coating solution for forming a charge transport layer. The coating solution for forming a charge transport layer was immersed and applied onto the charge generating layer, and dried at 143°C for 30 minutes to form a charge transport layer with a thickness of 33 μm. In this way, photoreceptor 1 was obtained.

[0279] (Examples 2 to 10, and Comparative Examples 1 to 4) A photoreceptor was obtained in the same manner as in Example 1, except that the composition of each layer was changed as shown in Table 2.

[0280] <Evaluation of suppression of localized deterioration of electrical characteristics> The photoreceptor was mounted in an electrophotographic image forming apparatus (Xerox 700 Digital Color Press, manufactured by Xerox Corporation). A surface potential probe was placed 1 mm away from the surface of the photoreceptor using a surface potential meter (Trek 334, manufactured by Trek). The electrical characteristics of nine points along the axial direction of the target drum (four points each above and below at 20 mm intervals from the central point) were evaluated as follows. The drum was charged to -700V by the image forming apparatus, and the post-exposure potential (VL) was set to -230V. Then, 200,000 full-surface halftone images with 30% image density were printed on A4 size paper under high temperature and high humidity conditions (temperature 28°C and relative humidity 85%). The surface potential was then measured using the surface potential meter (surface potential measurements were performed after charging and exposure, similar to the initial measurement), and classified as follows. (A difference of 10V between the initial and post-200,000 prints is preferable for each point; the more locations with this difference, the more stable the electrical characteristics are considered to be.) The evaluation criteria are as follows. A: 9 / 9 points, initial surface potential - long-term surface potential difference is within 5V. A-: 9 / 9 points, initial surface potential - long-term surface potential difference is greater than 5V and less than 10V. B+: 8 / 9 points, initial surface potential - long-term surface potential difference is within 10V. B: 7 / 9 points, initial surface potential - long-term surface potential difference is within 10V. B-: 6 / 9 points, initial surface potential - long-term surface potential difference is within 10V. C: 5~3 / 9 points, initial surface potential - long-term surface potential difference within 10V D: 2~1 / 9 points, initial surface potential - long-term surface potential difference is within 10V. E: 0 / 9 points, initial surface potential - long-term surface potential difference is within 10V.

[0281] The evaluation results are summarized in Table 2.

[0282] [Table 2]

[0283] As shown in Table 2, the electrophotographic photoreceptors of Examples 1 to 10 showed superior suppression of localized deterioration of electrical properties after long-term printing compared to the electrophotographic photoreceptors of Comparative Examples 1 to 4.

[0284] (((1))) An electrophotographic photoreceptor comprising a conductive substrate and a laminated photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate, wherein the charge transport layer contains a polyarylate resin having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by formula (B), the charge generating layer contains chlorogallium phthalocyanine as a charge generating material, and the value of the binder resin content / total binder resin and charge generating material content in the charge generating layer is greater than 0.4 and less than 0.7.

[0285] [ka]

[0286] In equation (A), Ar A1 and Ar A2 Each of these is an aromatic ring which may independently have substituents, L A is a single bond or a divalent linking group, n A1 It is 0, 1, or 2. In equation (B), Ar B1 and Ar B2 Each of these is an aromatic ring which may independently have substituents, L B is a single bond, oxygen atom, sulfur atom or -C(Rb 1 )(Rb 2 )- and n B1 Rb is 0, 1, or 2. 1 and Rb 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.

[0287] (((2))) The electrophotographic photoreceptor according to (((1))), wherein the value of the content of the binder resin in the charge generating layer / the total content of the binder resin and charge generating material is greater than 0.43 and less than 0.60. (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))) wherein the dicarboxylic acid unit represented by formula (A) comprises at least one selected from the group consisting of a dicarboxylic acid unit represented by formula (A1) (A1), a dicarboxylic acid unit represented by formula (A2) (A2), a dicarboxylic acid unit represented by formula (A3) (A3), a dicarboxylic acid unit represented by formula (A4) (A4), and a dicarboxylic acid unit represented by formula (A5) (A5).

[0288] [ka]

[0289] 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 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. 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 401n 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.

[0290] (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))) wherein the diol unit represented by formula (B) includes at least one selected from the group consisting of the diol unit represented by formula (B1) (B1), the diol unit represented by formula (B2) (B2), the diol unit represented by formula (B3) (B3), the diol unit represented by formula (B4) (B4), the diol unit represented by formula (B5) (B5), the diol unit represented by formula (B6) (B6), the diol unit represented by formula (B7) (B7), and the diol unit represented by formula (B8) (B8).

[0291] [ka]

[0292] [ka]

[0293] 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 , Rb801 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 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 905Each 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 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.

[0294] (((5))) The electrophotographic photoreceptor according to any one of (((1))) to (((4))) wherein the binding resin in the charge generation layer is a vinyl acetate resin or a polyvinyl butyral resin. (((6))) The electrophotographic photoreceptor according to any one of (((1))) to (((5))) wherein the binder resin in the charge generation layer is a vinyl chloride-vinyl acetate copolymer or a polyvinyl butyral resin. (((7))) The electrophotographic photoreceptor according to any one of (((1))) to (((6))), wherein the charge transport layer further contains a polycarbonate resin. A process cartridge for attaching to and detaching from an image forming apparatus, comprising an electrophotographic photoreceptor as described in any one of (((8))) (((1))) to (((7))). An image forming apparatus comprising: an electrophotographic photoreceptor as described in any one of (((9))) (((1))) to (((7))); 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.

[0295] According to the invention of (((1))), an electrophotographic photoreceptor is provided in which the charge transport layer contains a polyarylate resin having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by the formula (B), the charge generation layer contains chlorogallium phthalocyanine as a charge generation material, and the value of the binder resin content / total content of the binder resin and charge generation material in the charge generation layer is 0.4 or less or 0.7 or more, compared to the case in which the local deterioration of electrical properties after long-term printing is suppressed. According to the invention of (((2))), an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to cases where the value of the binder resin content / total content of the binder resin and charge generating material in the charge generating layer is 0.43 or less or 0.60 or more. According to the invention of (((3))), an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to the case in which the dicarboxylic acid unit represented by formula (A) does not include at least one selected from the group consisting of the dicarboxylic acid unit represented by formula (A1) (A1), the dicarboxylic acid unit represented by formula (A2) (A2), the dicarboxylic acid unit represented by formula (A3) (A3), the dicarboxylic acid unit represented by formula (A4) (A4), and the dicarboxylic acid unit represented by formula (A5) (A5). According to the invention of (((4))), an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to the case in which the diol unit represented by formula (B) does not include at least one selected from the group consisting of the diol unit represented by formula (B1) (B1), the diol unit represented by formula (B2) (B2), the diol unit represented by formula (B3) (B3), the diol unit represented by formula (B4) (B4), the diol unit represented by formula (B5) (B5), the diol unit represented by formula (B6) (B6), the diol unit represented by formula (B7) (B7), and the diol unit represented by formula (B8) (B8). According to the invention of (((5))), an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to the case in which the binder resin in the charge generation layer is polyester resin. According to the invention of (((6))), an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to the case in which the binder resin in the charge generation layer is a vinyl acetate homopolymer. According to the invention of (((7))), an electrophotographic photoreceptor is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to a case in which the charge transport layer further does not contain polycarbonate resin. According to the invention of (((8))) or (((9))), a process cartridge or image forming apparatus is provided that is superior in suppressing local deterioration of electrical properties after long-term printing compared to a case where the charge transport layer of an electrophotographic photoreceptor contains a polyarylate resin having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by formula (B), and the charge generating layer contains chlorogallium phthalocyanine as a charge generating material, and the value of the binder resin content / total content of the binder resin and charge generating material in the charge generating layer is 0.4 or less or 0.7 or more. [Explanation of Symbols]

[0296] 1 conductive substrate, 2 subbing layer, 3 charge generation layer, 4 charge transport layer, 5 photosensitive layer, 10A photoreceptor

[0297] 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. The device comprises a conductive substrate and a multilayer photosensitive layer having a charge generation layer and a charge transport layer disposed on the conductive substrate, The charge transport layer contains a polyarylate resin having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by the following formula (B). The charge generation layer contains chlorogallium phthalocyanine as a charge generation material, The value of the binder resin content / total content of the binder resin and charge generating material in the charge generating layer is greater than 0.4 and less than 0.

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

2. The electrophotographic photoreceptor according to claim 1, wherein the value of the content of the binder resin / the total content of the binder resin and charge generating material in the charge generating layer is greater than 0.43 and less than 0.

60.

3. The electrophotographic photoreceptor according to claim 1, wherein the dicarboxylic acid unit represented by formula (A) includes at least one selected from the group consisting of a dicarboxylic acid unit represented by formula (A1) (A1), a dicarboxylic acid unit represented by formula (A2) (A2), a dicarboxylic acid unit represented by formula (A3) (A3), a dicarboxylic acid unit represented by formula (A4) (A4), and a dicarboxylic acid unit represented by formula (A5) (A5). 【Chemistry 2】 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 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. 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.

4. The electrophotographic photoreceptor according to claim 1, wherein the diol unit represented by formula (B) includes at least one selected from the group consisting of the diol unit represented by formula (B1) (B1), the diol unit represented by formula (B2) (B2), the diol unit represented by formula (B3) (B3), the diol unit represented by formula (B4) (B4), the diol unit represented by formula (B5) (B5), the diol unit represented by formula (B6) (B6), the diol unit represented by formula (B7) (B7), and the diol unit represented by formula (B8) (B8). 【Transformation 3】 【Chemistry 4】 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 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 formula (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 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.

5. The electrophotographic photoreceptor according to claim 1, wherein the binder resin in the charge generation layer is a vinyl acetate resin or a polyvinyl butyral resin.

6. The electrophotographic photoreceptor according to claim 1, wherein the binder resin in the charge generation layer is a vinyl chloride-vinyl acetate copolymer or a polyvinyl butyral resin.

7. The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer further contains a polycarbonate resin.

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. 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, Equipped with Image forming apparatus.

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