ELECTROPHOTOGRAPHIC PHOTORECEPTOR, PROCESS CARTRIDGE, AND IMAGE FORMING APPARATUS

Abstract

An electrophotographic photoreceptor includes a conductive substrate, and a lamination-type photosensitive layer disposed on the conductive substrate and having a charge generation layer and a charge transport layer, 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), the charge generation layer contains, as a charge generation material, a chlorogallium phthalocyanine, and a value of a content of a binder resin to a total content of the binder resin and the charge generation material in the charge generation layer is more than 0.4 and less than 0.7,

##STR00001## in Formula (A), Ar.sup.A1 and Ar.sup.42 are each independently an aromatic ring which may have a substituent, L.sup.A is a single bond or a divalent linking group, and n.sup.A1 is 0, 1, or 2, in Formula (B), Ar.sup.B1 and Ar.sup.B2 are each independently an aromatic ring which may have a substituent, L.sup.B is a single bond, an oxygen atom, a sulfur atom, or C(Rb.sup.1)(Rb.sup.2), and n.sup.B1 is 0, 1, or 2, where Rb.sup.1 and Rb.sup.2 are each independently a hydrogen atom, an alkyl group having 1 or more and 20 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an aralkyl group having 7 or more and 20 or less carbon atoms, and Rb.sup.1 and Rb.sup.2 may be bonded to each other to form a cyclic alkyl group.

Claims

1. An electrophotographic photoreceptor comprising: a conductive substrate; and a lamination-type photosensitive layer disposed on the conductive substrate and having a charge generation layer and a charge transport layer, wherein 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, as a charge generation material, a chlorogallium phthalocyanine, and a value of a content of a binder resin to a total content of the binder resin and the charge generation material in the charge generation layer is more than 0.4 and less than 0.7, ##STR00049## in Formula (A), Ar.sup.A1 and Ar.sup.A2 are each independently an aromatic ring which may have a substituent, L.sup.A is a single bond or a divalent linking group, and n.sup.A1 is 0, 1, or 2, in Formula (B), Ar.sup.B1 and Ar.sup.B2 are each independently an aromatic ring which may have a substituent, L.sup.B is a single bond, an oxygen atom, a sulfur atom, or C(Rb.sup.1)(Rb.sup.2), and n.sup.B1 is 0, 1, or 2, where Rb.sup.1 and Rb.sup.2 are each independently a hydrogen atom, an alkyl group having 1 or more and 20 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an aralkyl group having 7 or more and 20 or less carbon atoms, and Rb.sup.1 and Rb.sup.2 may be bonded to each other to form a cyclic alkyl group.

2. The electrophotographic photoreceptor according to claim 1, wherein the value of the content of the binder resin to the total content of the binder resin and the charge generation material in the charge generation layer is more 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 (A1) represented by Formula (A1), a dicarboxylic acid unit (A2) represented by Formula (A2), a dicarboxylic acid unit (A3) represented by Formula (A3), a dicarboxylic acid unit (A4) represented Formula (A4), and a dicarboxylic acid unit (A5) represented by Formula (A5), ##STR00050## in Formula (A1), n.sup.101 is an integer of 0 or greater and 4 or less, and n.sup.101 pieces of Ra.sup.101's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms, in Formula (A2), n.sup.201 and n.sup.202 are each independently an integer of 0 or greater and 4 or less, and n.sup.201 pieces of Ra.sup.201's and n.sup.202 pieces of Ra.sup.202's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms, in Formula (A3), n.sup.301 and n.sup.302 are each independently an integer of 0 or greater and 4 or less, and n.sup.301 pieces of Ra.sup.301's and n.sup.302 pieces of Ra.sup.302's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms, in Formula (A4), n.sup.401 is an integer of 0 or greater and 6 or less, and n.sup.401 pieces of Ra.sup.401's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms, in Formula (A5), n.sup.501, n.sup.502, and n.sup.503 are each independently an integer of 0 or greater and 4 or less, and n.sup.501 pieces of Ra.sup.501's, n.sup.502 pieces of Ra.sup.502's, and n.sup.503 pieces of Ra.sup.503's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less 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 a diol unit (B1) represented by Formula (B1), a diol unit (B2) represented by Formula (B2), a diol unit (B3) represented by Formula (B3), a diol unit (B4) represented by Formula (B4), a diol unit (B5) represented by Formula (B5), a diol unit (B6) represented by Formula (B6), a diol unit (B7) represented by Formula (B7), and a diol unit (B8) represented by Formula (B8), ##STR00051## ##STR00052## in Formula (B1), Rb.sup.101 is a branched alkyl group having 4 or more and 20 or less carbon atoms, Rb.sup.201 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.401, Rb.sup.501, Rb.sup.801, and Rb.sup.901 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom, in Formula (B2), Rb.sup.102 is a linear alkyl group having 4 or more and 20 or less carbon atoms, Rb.sup.202 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.402, Rb.sup.502, Rb.sup.802, and Rb.sup.902 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom, in Formula (B3), Rb.sup.113 and Rb.sup.213 are each independently a hydrogen atom, a linear alkyl group having 1 or more and 3 or less carbon atoms, an alkoxy group having 1 or more and 4 or less carbon atoms, or a halogen atom, d is an integer of 7 or greater and 15 or less, and Rb.sup.403, Rb.sup.503, Rb.sup.803, and Rb.sup.903 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom, in Formula (B4), Rb.sup.104 and Rb.sup.204 are each independently a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.404, Rb.sup.504, Rb.sup.804, and Rb.sup.904 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom, in Formula (B5), Ar.sup.105 is an aryl group having 6 or more and 12 or less carbon atoms or an aralkyl group having 7 or more and 20 or less carbon atoms, Rb.sup.205 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.405, Rb.sup.505, Rb.sup.805, and Rb.sup.905 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom, in Formula (B6), Rb.sup.116 and Rb.sup.216 are each independently a hydrogen atom, a linear alkyl group having 1 or more and 3 or less carbon atoms, an alkoxy group having 1 or more and 4 or less carbon atoms, or a halogen atom, e is an integer of 4 or greater and 6 or less, and Rb.sup.406, Rb.sup.506, Rb.sup.806, and Rb.sup.906 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom, in Formula (B7), Rb.sup.407, Rb.sup.507, Rb.sup.807, and Rb.sup.907 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom, in Formula (B8), Rb.sup.408, Rb.sup.508, Rb.sup.808, and Rb.sup.908 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less 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-based resin or a polyvinyl butyral-based 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. A process cartridge comprising: the electrophotographic photoreceptor according to claim 1, wherein the process cartridge is attachable to and detachable from an image forming apparatus.

9. A process cartridge comprising: the electrophotographic photoreceptor according to claim 2, wherein the process cartridge is attachable to and detachable from an image forming apparatus.

10. A process cartridge comprising: the electrophotographic photoreceptor according to claim 3, wherein the process cartridge is attachable to and detachable from an image forming apparatus.

11. A process cartridge comprising: the electrophotographic photoreceptor according to claim 4, wherein the process cartridge is attachable to and detachable from an image forming apparatus.

12. A process cartridge comprising: the electrophotographic photoreceptor according to claim 5, wherein the process cartridge is attachable to and detachable from an image forming apparatus.

13. A process cartridge comprising: the electrophotographic photoreceptor according to claim 6, wherein the process cartridge is attachable to and detachable from an image forming apparatus.

14. A process cartridge comprising: the electrophotographic photoreceptor according to claim 7, wherein the process cartridge is attachable to and detachable from an image forming apparatus.

15. An image forming apparatus comprising: the electrophotographic photoreceptor according to claim 1; a charging device that charges a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and a transfer device that transfers the toner image to a surface of a recording medium.

16. An image forming apparatus comprising: the electrophotographic photoreceptor according to claim 2; a charging device that charges a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and a transfer device that transfers the toner image to a surface of a recording medium.

17. An image forming apparatus comprising: the electrophotographic photoreceptor according to claim 3; a charging device that charges a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and a transfer device that transfers the toner image to a surface of a recording medium.

18. An image forming apparatus comprising: the electrophotographic photoreceptor according to claim 4; a charging device that charges a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and a transfer device that transfers the toner image to a surface of a recording medium.

19. An image forming apparatus comprising: the electrophotographic photoreceptor according to claim 5; a charging device that charges a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and a transfer device that transfers the toner image to a surface of a recording medium.

20. An image forming apparatus comprising: the electrophotographic photoreceptor according to claim 6; a charging device that charges a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and a transfer device that transfers the toner image to a surface of a recording medium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Exemplary embodiment(s) of the present invention will be described in detail based on the following figures, wherein:

[0013] FIG. 1 is a partial cross-sectional view showing an example of a layer configuration of an electrophotographic photoreceptor according to the present exemplary embodiment;

[0014] FIG. 2 is a schematic configuration view showing the configuration of an example of an image forming apparatus according to the present exemplary embodiment; and

[0015] FIG. 3 is a schematic configuration view showing a configuration of another example of the image forming apparatus according to the present exemplary embodiment.

DETAILED DESCRIPTION

[0016] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] In the present specification, a numerical range described using to represents a range including numerical values listed before and after to as the minimum value and the maximum value respectively.

[0018] Regarding the numerical ranges described in stages in the present specification, the upper limit or lower limit of a numerical range may be replaced with the upper limit or lower limit of another numerical range described in stages. Furthermore, in the present specification, the upper limit or lower limit of a numerical range may be replaced with values described in examples.

[0019] In the present specification, the term step includes not only an independent step but a step that is not clearly distinguished from other steps as long as the purpose of the step is achieved.

[0020] In the present specification, in a case where an exemplary embodiment is described with reference to drawings, the configuration of the exemplary embodiment is not limited to the configuration shown in the drawings. In addition, the sizes of members in each drawing are conceptual and do not limit the relative relationship between the sizes of the members.

[0021] In the present specification, each component may include a plurality of corresponding substances. In a case where the amount of each component in a composition is mentioned in the present exemplary embodiments, and there are two or more kinds of substances corresponding to each component in the composition, unless otherwise specified, the amount of each component means the total amount of two or more kinds of the substances present in the composition.

[0022] In the present specification, each component may include two or more kinds of corresponding particles. In a case where a plurality of kinds of particles corresponding to each component are present in a composition, the particle diameter of each component indicates the value of a mixture of the plurality of kinds of particles present in the composition, unless otherwise specified.

[0023] In the present specification, an alkyl group and an alkylene group include all linear, branched, and cyclic shapes unless otherwise specified.

[0024] In the present specification, a hydrogen atom in an organic group, an aromatic ring, a linking group, an alkyl group, an alkylene group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, and the like may be substituted with a halogen atom.

[0025] In the present specification, in a case where a compound is represented by a structural formula, the compound may be represented by a structural formula in which symbols representing a carbon atom and a hydrogen atom (C and H) in a hydrocarbon group and/or a hydrocarbon chain are omitted.

[0026] In the present specification, constitutional unit of a copolymer or a resin is the same as a monomer unit.

[0027] In the present specification, ppm stands for parts per million and is on a mass basis.

Electrophotographic Photoreceptor

[0028] An electrophotographic photoreceptor according to the present exemplary embodiment includes a conductive substrate, and a lamination-type photosensitive layer disposed on the conductive substrate and having a charge generation layer and a charge transport layer, 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), the charge generation layer contains, as a charge generation material, a chlorogallium phthalocyanine, and a value of a content of a binder resin to a total content of the binder resin and the charge generation material in the charge generation layer is more than 0.4 and less than 0.7.

##STR00003##

[0029] In Formula (A), Ar.sup.A1 and Ar.sup.A2 are each independently an aromatic ring which may have a substituent, L.sup.A is a single bond or a divalent linking group, and n.sup.A1 is 0, 1, or 2.

[0030] In Formula (B), Ar.sup.B1 and Ar.sup.B2 are each independently an aromatic ring which may have a substituent, L.sup.B is a single bond, an oxygen atom, a sulfur atom, or C(Rb.sup.1)(Rb.sup.2), and n.sup.B1 is 0, 1, or 2. Where Rb.sup.1 and Rb.sup.2 are each independently a hydrogen atom, an alkyl group having 1 or more and 20 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an aralkyl group having 7 or more and 20 or less carbon atoms, and Rb.sup.1 and Rb.sup.2 may be bonded to each other to form a cyclic alkyl group.

[0031] Since the polyarylate resin is synthesized using an acid chloride, the acid chloride itself or deactivated dicarboxylic acid is likely to remain as an impurity.

[0032] In a case where an acid chloride or a dicarboxylic acid of impurities is present, it is presumed that the impurities interact with the charge generation material, and thus the electrical properties locally deteriorate. In addition, it is also considered that the fact that the acid component moves to the vicinity of the charge generation material and interacts with the charge generation material over time even in a case where there is no problem at the initial stage is one of the causes of the local deterioration in the electrical properties.

[0033] It is considered that the hydroxygallium phthalocyanine, which is a charge generation material, easily interacts with the acid component, and thus the electrical properties are likely to deteriorate. On the other hand, it is considered that chlorogallium phthalocyanine is not likely to interact with the acid component, and thus the chlorogallium phthalocyanine is stably present over time and the electrical properties are stable for a long period of time.

[0034] In addition, it is presumed that the polyarylate resin using phthalic acid has a high acidity of phthalic acid, and thus easily interacts with chlorogallium phthalocyanine, which is considered to be a cause of deterioration in electrical properties.

[0035] In addition, in a case where the value of the content of the binder resin to the total content of the binder resin and the charge generation material in the charge generation layer is 0.4 or less, it is presumed that the proportion of the charge generation material that interacts with the acid component increases, which leads to local deterioration in electrical properties. In a case where the value of the content of the binder resin to the total content of the binder resin and the charge generation material is 0.7 or more, it is considered that the proportion of the charge generation material that interacts with the acid component is small, but the influence of the deterioration of the local electrical properties in a case of the interaction is large, which leads to the deterioration of the electrical properties.

[0036] In the electrophotographic photoreceptor according to the present exemplary embodiment, the charge transport layer contains a polyarylate resin having a dicarboxylic acid unit (A) and a diol unit (B), the charge generation layer contains chlorogallium phthalocyanine, and a value of a content of a binder resin to a total content of the binder resin and the charge generation material in the charge generation layer is more than 0.4 and less than 0.7, so that an interaction between the charge generation material and an acid component is suppressed, and the local deterioration suppression properties of the electrical properties after long-term printing is excellent.

[0037] The electrophotographic photoreceptor (hereinafter, also referred to as photoreceptor) according to the present exemplary embodiment includes a conductive substrate and a lamination-type photosensitive layer disposed on the conductive substrate and having a charge generation layer and a charge transport layer.

[0038] The electrophotographic photoreceptor according to the present exemplary embodiment may further include other layers (for example, an undercoat layer and an interlayer).

[0039] FIG. 1 is a partial cross-sectional view schematically showing an example of a layer configuration of the photoreceptor according to the present exemplary embodiment. A photoreceptor 10A shown in FIG. 1 includes a lamination-type photosensitive layer. The photoreceptor 10A has a structure in which an undercoat layer 2, a charge generation layer 3, and a charge transport layer 4 are laminated in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute a photosensitive layer 5 (so-called function separation-type photosensitive layer). The photoreceptor 10A may include an interlayer (not shown) between the undercoat layer 2 and the charge generation layer 3. The undercoat layer 2 may or may not be provided.

[0040] Hereinafter, each layer of the photoreceptor will be described in detail.

Charge Transport Layer

[0041] The charge transport layer in the electrophotographic photoreceptor according to the present exemplary embodiment contains a polyarylate resin having a dicarboxylic acid unit (A) represented by Formula (A) and a diol unit (B) represented by Formula (B).

[0042] In the polyarylate resin, resin molecules are bonded to each other by an intermolecular force due to stacking of aromatic rings, and thus the abrasion resistance of the charge transport layer is improved. As the polyarylate resin, for example, a polycondensate of bisphenols and an aromatic divalent carboxylic acid is preferable. Examples of the form of the polyarylate resin include a polyarylate resin (PA) described below.

[0043] The polyarylate resin contained in the charge transport layer contains at least a polyarylate resin having a dicarboxylic acid unit (A) and a diol unit (B). In the present disclosure, the polyarylate resin is referred to as a polyarylate resin (PA).

[0044] The dicarboxylic acid unit (A) is a constitutional unit represented by Formula (A).

##STR00004##

[0045] In Formula (A), Ar.sup.A1 and Ar.sup.A2 are each independently an aromatic ring which may have a substituent, L.sup.A is a single bond or a divalent linking group, and n.sup.A1 is 0, 1, or 2.

[0046] The aromatic ring as Ar.sup.A1 may be a monocycle or a polycycle. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Among these, for example, a benzene ring and a naphthalene ring are preferable.

[0047] A hydrogen atom on the aromatic ring as Ar.sup.A1 may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. As the substituent in a case where the aromatic ring as Ar.sup.A1 is substituted, for example, an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms is preferable.

[0048] The aromatic ring as Ar.sup.A2 may be a monocycle or a polycycle. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Among these, for example, a benzene ring and a naphthalene ring are preferable.

[0049] A hydrogen atom on the aromatic ring as Ar.sup.A2 may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. As the substituent in a case where the aromatic ring as Ar.sup.A2 is substituted, for example, an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms is preferable.

[0050] In a case where L.sup.A is a divalent linking group, examples of the divalent linking group include an oxygen atom, a sulfur atom, and C(Ra.sup.1)(Ra.sup.2). Here, Ra.sup.1 and Ra.sup.2 are each independently a hydrogen atom, an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an aralkyl group having 7 or more and 20 or less carbon atoms, and Ra.sup.1 and Ra.sup.2 may be bonded to each other to form a cyclic alkyl group.

[0051] The alkyl group having 1 or more and 10 or less carbon atoms, as Ra.sup.1 and Ra.sup.2, may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is, for example, preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and still more preferably 1 or 2.

[0052] The aryl group having 6 or more and 12 or less carbon atoms, as Ra.sup.1 and Ra.sup.2, may be a monocycle or a polycycle. The number of carbon atoms of the aryl group is, for example, preferably 6 or more and 10 or less and more preferably 6.

[0053] An alkyl group of the aralkyl group having 7 or more and 20 or less carbon atoms, as Ra.sup.1 and Ra.sup.2, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the aralkyl group having 7 or more and 20 or less carbon atoms is, for example, preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

[0054] An aryl group of the aralkyl group having 7 or more and 20 or less carbon atoms, as Ra.sup.1 and Ra.sup.2, may be a monocycle or a polycycle. The number of carbon atoms of the aryl group is, for example, preferably 6 or more and 10 or less and more preferably 6.

[0055] From the viewpoint of local deterioration suppression properties of electrical properties after long-term printing, the dicarboxylic acid unit (A) preferably includes, for example, at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by Formula (A1), a dicarboxylic acid unit (A2) represented by Formula (A2), a dicarboxylic acid unit (A3) represented by Formula (A3), a dicarboxylic acid unit (A4) represented by Formula (A4), and a dicarboxylic acid unit (A5) represented by Formula (A5). The dicarboxylic acid unit (A) includes, for example, more preferably at least one selected from the group consisting of a dicarboxylic acid unit (A2), a dicarboxylic acid unit (A3), and a dicarboxylic acid unit (A4) and still more preferably a dicarboxylic acid unit (A2).

##STR00005##

[0056] In Formula (A1), n.sup.101 is an integer of 0 or greater and 4 or less, and n.sup.101 pieces of Ra.sup.101's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0057] n.sup.101 is, for example, preferably 0, 1, or 2, more preferably 0 or 1, and still more preferably 0.

##STR00006##

[0058] In Formula (A2), n.sup.201 and n.sup.202 are each independently an integer of 0 or greater and 4 or less, and n.sup.201 pieces of Ra.sup.201's and n.sup.202 pieces of Ra.sup.202's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0059] n.sup.201 represents, for example, preferably 0, 1, or 2, more preferably 0 or 1, and still more preferably 0.

[0060] n.sup.202 represents, for example, preferably 0, 1, or 2, more preferably 0 or 1, and still more preferably 0.

##STR00007##

[0061] In Formula (A3), n.sup.301 and n.sup.302 are each independently an integer of 0 or greater and 4 or less, and n.sup.301 pieces of Ra.sup.301's and n.sup.302 pieces of Ra.sup.302's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0062] n.sup.301 is, for example, preferably 0, 1, or 2, more preferably 0 or 1, and still more preferably 0.

[0063] n.sup.302 is, for example, preferably 0, 1, or 2, more preferably 0 or 1, and still more preferably 0.

##STR00008##

[0064] In Formula (A4), n.sup.401 is an integer of 0 or greater and 6 or less, and n.sup.401 pieces of Ra.sup.401's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0065] n.sup.401 represents, for example, preferably an integer of 0 or greater and 4 or less, more preferably 0, 1, or 2, and still more preferably 0.

##STR00009##

[0066] In Formula (A5), n.sup.501, n.sup.502, and n.sup.503 are each independently an integer of 0 or greater and 4 or less, and n.sup.501 pieces of Ra.sup.501's, n.sup.502 pieces of Ra.sup.502's, and n.sup.503 pieces of Ra.sup.503's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0067] n.sup.501 represents, for example, preferably 0, 1, or 2, more preferably 0 or 1, and still more preferably 0.

[0068] n.sup.502 represents, for example, preferably 0, 1, or 2, more preferably 0 or 1, and still more preferably 0.

[0069] n.sup.503 represents, for example, preferably 0, 1, or 2, more preferably 0 or 1, and still more preferably 0.

[0070] The specific aspects and the preferred aspects of Ra.sup.101 in Formula (A1), Ra.sup.201 and Ra.sup.202 in Formula (A2), Ra.sup.301 and Ra.sup.302 in Formula (A3), Ra.sup.401 in Formula (A4), and Ra.sup.501, Ra.sup.502, and Ra.sup.503 in Formula (A5) are the same as each other, and hereinafter, Ra.sup.101, Ra.sup.201, Ra.sup.202, Ra.sup.301, Ra.sup.302, Ra.sup.401, Ra.sup.501, Ra.sup.502, and Ra.sup.503 will be collectively referred to as Ra.

[0071] The alkyl group having 1 or more and 10 or less carbon atoms as Ra may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is, for example, preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and still more preferably 1 or 2.

[0072] Examples of the linear alkyl group having 1 or more and 10 or less carbon atoms include a methyl group, an ethyl group, a n-propyl group, a n-butyl group, a n-pentyl group, a n-hexyl group, a n-heptyl group, a n-octyl group, a n-nonyl group, and a n-decyl group.

[0073] Examples of the branched alkyl group having 3 or more and 10 or less carbon atoms include an isopropyl group, an isobutyl group, an sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, an sec-hexyl group, a tert-hexyl group, an isoheptyl group, an sec-heptyl group, a tert-heptyl group, an isooctyl group, an sec-octyl group, a tert-octyl group, an isononyl group, an sec-nonyl group, a tert-nonyl group, an isodecyl group, an sec-decyl group, and a tert-decyl group.

[0074] Examples of the cyclic alkyl group having 3 or more and 10 or less carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and polycyclic (for example, bicyclic, tricyclic, or spirocyclic) alkyl groups to which these monocyclic alkyl groups are linked.

[0075] The aryl group having 6 or more and 12 or less carbon atoms as Ra may be a monocycle or a polycycle. The number of carbon atoms of the aryl group is, for example, preferably 6 or more and 10 or less and more preferably 6.

[0076] Examples of the aryl group having 6 or more and 12 or less carbon atoms include a phenyl group, a biphenyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0077] The alkyl group in the alkoxy group having 1 or more and 6 or less carbon atoms as Ra may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the alkoxy group having 1 or more and 6 or less carbon atoms is, for example, preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

[0078] Examples of the linear alkoxy group having 1 or more and 6 or less carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group.

[0079] Examples of the branched alkoxy group having 3 or more and 6 or less carbon atoms include an isopropoxy group, an isobutoxy group, an sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, an sec-hexyloxy group, and a tert-hexyloxy group.

[0080] Examples of the cyclic alkoxy group having 3 or more and 6 or less carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0081] Hereinafter, dicarboxylic acid units (A1-1) to (A1-9) are shown as specific examples of the dicarboxylic acid unit (A1). The dicarboxylic acid unit (A1) is not limited thereto.

##STR00010##

[0082] Hereinafter, dicarboxylic acid units (A2-1) to (A2-3) are shown as specific examples of the dicarboxylic acid unit (A2). The dicarboxylic acid unit (A2) is not limited thereto.

##STR00011##

[0083] Hereinafter, dicarboxylic acid units (A3-1) and (A3-2) are shown as specific examples of the dicarboxylic acid unit (A3). The dicarboxylic acid unit (A3) is not limited thereto.

##STR00012##

[0084] Hereinafter, dicarboxylic acid units (A4-1) to (A4-3) are shown as specific examples of the dicarboxylic acid unit (A4). The dicarboxylic acid unit (A4) is not limited thereto.

##STR00013##

[0085] Hereinafter, dicarboxylic acid units (A5-1) to (A5-4) are shown as specific examples of the dicarboxylic acid unit (A5). The dicarboxylic acid unit (A5) is not limited thereto.

##STR00014##

[0086] In the above-described specific examples, for example, at least one selected from the group consisting of (A1-1), (A1-7), (A2-3), (A3-2), and (A4-3) is preferably included, at least one selected from the group consisting of (A2-3), (A3-2), and (A4-3) is more preferably included, and at least (A2-3) is still more preferably included as the dicarboxylic acid unit (A).

[0087] The dicarboxylic acid unit (A) included in the polyarylate resin (PA) may be used alone or in combination of two or more kinds thereof.

[0088] A mass proportion of the dicarboxylic acid unit (A) in the polyarylate resin (PA) is, for example, preferably 15% by mass or more and 60% by mass or less.

[0089] In a case where the mass proportion of the dicarboxylic acid unit (A) is 15% by mass or more, the abrasion resistance of the charge transport layer is enhanced. From the viewpoint, the mass proportion of the dicarboxylic acid unit (A) is, for example, more preferably 20% by mass or more, and still more preferably 25% by mass or more.

[0090] In a case where the mass proportion of the dicarboxylic acid unit (A) is 60% by mass or less, peeling of the charge transport layer can be suppressed. From the viewpoint, the mass proportion of the dicarboxylic acid unit (A) is, for example, more preferably 55% by mass or less, and still more preferably 50% by mass or less.

[0091] The polyarylate resin (PA) may have other dicarboxylic acid units in addition to the dicarboxylic acid unit (A). Examples of other dicarboxylic acid units include aliphatic dicarboxylic acids (such as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenyl succinic acid, adipic acid, and sebacic acid) units, alicyclic dicarboxylic acid (such as cyclohexanedicarboxylic acid) units, and lower alkyl ester units (for example, having 1 or more and 5 or less carbon atoms) thereof. The dicarboxylic acid units included in the polyarylate resin (PA) may be used alone or in combination of two or more kinds thereof.

[0092] The diol unit (B) is a constitutional unit represented by Formula (B).

##STR00015##

[0093] In Formula (B), Ar.sup.B1 and Ar.sup.B2 are each independently an aromatic ring which may have a substituent, L.sup.B is a single bond, an oxygen atom, a sulfur atom, or C(Rb.sup.1)(Rb.sup.2), and n.sup.B1 is 0, 1, or 2, where Rb.sup.1 and Rb.sup.2 are each independently a hydrogen atom, an alkyl group having 1 or more and 20 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an aralkyl group having 7 or more and 20 or less carbon atoms, and Rb.sup.1 and Rb.sup.2 may be bonded to each other to form a cyclic alkyl group.

[0094] The aromatic ring as Ar.sup.B1 may be a monocycle or a polycycle. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Among these, for example, a benzene ring and a naphthalene ring are preferable.

[0095] A hydrogen atom on the aromatic ring as Ar.sup.B1 may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. As the substituent in a case where the aromatic ring as Ar.sup.B1 is substituted, for example, an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms is preferable.

[0096] The aromatic ring as Ar.sup.B2 may be a monocycle or a polycycle. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Among these, for example, a benzene ring and a naphthalene ring are preferable.

[0097] A hydrogen atom on the aromatic ring as Ar.sup.B2 may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. As the substituent in a case where the aromatic ring as Ar.sup.B2 is substituted, for example, an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms is preferable.

[0098] The alkyl group having 1 or more and 20 or less carbon atoms, as Rb.sup.1 and Rb.sup.2, may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is, for example, preferably 1 or more and 18 or less, more preferably 1 or more and 14 or less, and still more preferably 1 or more and 10 or less.

[0099] The aryl group having 6 or more and 12 or less carbon atoms, as Rb.sup.1 and Rb.sup.2, may be a monocycle or a polycycle. The number of carbon atoms of the aryl group is, for example, preferably 6 or more and 10 or less and more preferably 6.

[0100] An alkyl group of the aralkyl group having 7 or more and 20 or less carbon atoms, as Rb.sup.1 and Rb.sup.2, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the aralkyl group having 7 or more and 20 or less carbon atoms is, for example, preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

[0101] An aryl group of the aralkyl group having 7 or more and 20 or less carbon atoms, as Rb.sup.1 and Rb.sup.2, may be a monocycle or a polycycle. The number of carbon atoms of the aryl group is, for example, preferably 6 or more and 10 or less and more preferably 6.

[0102] From the viewpoint of local deterioration suppression properties of electrical properties after long-term printing, it is preferable that the diol unit (B) includes, for example, at least one selected from the group consisting of a diol unit (B1) represented by Formula (B1), a diol unit (B2) represented by Formula (B2), a diol unit (B3) represented by Formula (B3), a diol unit (B4) represented by Formula (B4), a diol unit (B5) represented by Formula (B5), a diol unit (B6) represented by Formula (B6), a diol unit (B7) represented by Formula (B7), and a diol unit (B8) represented by Formula (B8).

[0103] For example, the diol unit (B) more 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 (B4) represented by Formula (B4), the diol unit (B5) represented by Formula (B5), and the diol unit (B6) represented by Formula (B6); [0104] still more 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 (B5) represented by Formula (B5), and the diol unit (B6) represented by Formula (B6); [0105] even more preferably 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), and the diol unit (B6) represented by Formula (B6); and [0106] most preferably at least one selected from the group consisting of the diol unit (B1) represented by Formula (B1) and the diol unit (B2) represented by Formula (B2).

##STR00016##

[0107] In Formula (B1), Rb.sup.101 is a branched alkyl group having 4 or more and 20 or less carbon atoms, Rb.sup.201 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.401, Rb.sup.501, Rb.sup.801, and Rb.sup.901 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0108] The number of carbon atoms in the branched alkyl group having 4 or more and 20 or less carbon atoms, as Rb.sup.101, is, for example, preferably 4 or more and 16 or less, more preferably 4 or more and 12 or less, and still more preferably 4 or more and 8 or less. Specific examples of Rb.sup.101 include an isobutyl group, an sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, an sec-hexyl group, a tert-hexyl group, an isoheptyl group, an sec-heptyl group, a tert-heptyl group, an isooctyl group, an sec-octyl group, a tert-octyl group, an isononyl group, an sec-nonyl group, a tert-nonyl group, an isodecyl group, an sec-decyl group, a tert-decyl group, an isododecyl group, an sec-dodecyl group, a tert-dodecyl group, a tert-tetradecyl group, and a tert-pentadecyl group.

##STR00017##

[0109] In Formula (B2), Rb.sup.102 is a linear alkyl group having 4 or more and 20 or less carbon atoms, Rb.sup.202 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.402, Rb.sup.502, Rb.sup.802, and Rb.sup.902 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0110] The number of carbon atoms in the linear alkyl group having 4 or more and 20 or less carbon atoms, as Rb.sup.102, is, for example, preferably 4 or more and 16 or less, more preferably 4 or more and 12 or less, and still more preferably 4 or more and 8 or less. Specific examples of Rb.sup.102 include an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, a tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, and an n-icosyl group.

##STR00018##

[0111] In Formula (B3), Rb.sup.113 and Rb.sup.213 are each independently a hydrogen atom, a linear alkyl group having 1 or more and 3 or less carbon atoms, an alkoxy group having 1 or more and 4 or less carbon atoms, or a halogen atom, d is an integer of 7 or greater and 15 or less, and Rb.sup.403, Rb.sup.503, Rb.sup.803, and Rb.sup.903 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0112] The number of carbon atoms in the linear alkyl group having 1 or more and 3 or less carbon atoms, as Rb.sup.113 and Rb.sup.213, is, for example, preferably 1 or 2 and more preferably 1. Specific examples of such a group include a methyl group, an ethyl group, and an n-propyl group.

[0113] An alkyl group of the alkoxy group having 1 or more and 4 or less carbon atoms, as Rb.sup.113 and Rb.sup.213, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the alkoxy group having 1 or more and 4 or less carbon atoms is, for example, preferably 1 or more and 3 or less, more preferably 1 or 2, and still more preferably 1. Specific examples of such a group include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an isopropoxy group, an isobutoxy group, an sec-butoxy group, a tert-butoxy group, a cyclopropoxy group, and a cyclobutoxy group.

[0114] Examples of the halogen atom as Rb.sup.113 and Rb.sup.213 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

##STR00019##

[0115] In Formula (B4), Rb.sup.104 and Rb.sup.204 are each independently a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.404, Rb.sup.504, Rb.sup.804, and Rb.sup.904 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0116] The alkyl group having 1 or more and 3 or less carbon atoms, as Rb.sup.104, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is, for example, preferably 1 or 2 and more preferably 1. Specific examples of Rb.sup.104 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

##STR00020##

[0117] In Formula (B5), Ar.sup.105 is an aryl group having 6 or more and 12 or less carbon atoms or an aralkyl group having 7 or more and 20 or less carbon atoms, Rb.sup.205 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.405, Rb.sup.505, Rb.sup.805, and Rb.sup.905 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0118] The aryl group having 6 or more and 12 or less carbon atoms, as Ar.sup.105, may be a monocycle or a polycycle. The number of carbon atoms of the aryl group is, for example, preferably 6 or more and 10 or less and more preferably 6.

[0119] An alkyl group of the aralkyl group having 7 or more and 20 or less carbon atoms, as Ar.sup.105, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the aralkyl group having 7 or more and 20 or less carbon atoms is, for example, preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2. An aryl group of the aralkyl group having 7 or more and 20 or less carbon atoms, as Ar.sup.105, may be a monocycle or a polycycle. The number of carbon atoms of the aryl group is, for example, preferably 6 or more and 10 or less and more preferably 6. Examples of the aralkyl group having 7 or more and 20 or less carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, a 4-phenylbutyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, a phenylnonyl group, a naphthylmethyl group, a naphthylethyl group, an anthracenylmethyl group, and a phenyl-cyclopentylmethyl group.

##STR00021##

[0120] In Formula (B6), Rb.sup.116 and Rb.sup.216 are each independently a hydrogen atom, a linear alkyl group having 1 or more and 3 or less carbon atoms, an alkoxy group having 1 or more and 4 or less carbon atoms, or a halogen atom, e is an integer of 4 or greater and 6 or less, and Rb.sup.406, Rb.sup.506, Rb.sup.806, and Rb.sup.906 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0121] The number of carbon atoms in the linear alkyl group having 1 or more and 3 or less carbon atoms, as Rb.sup.116 and Rb.sup.216, is, for example, preferably 1 or 2 and more preferably 1. Specific examples of such a group include a methyl group, an ethyl group, and an n-propyl group.

[0122] An alkyl group of the alkoxy group having 1 or more and 4 or less carbon atoms, as Rb.sup.116 and Rb.sup.216, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the alkoxy group having 1 or more and 4 or less carbon atoms is, for example, preferably 1 or more and 3 or less, more preferably 1 or 2, and still more preferably 1. Specific examples of such a group include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an isopropoxy group, an isobutoxy group, an sec-butoxy group, a tert-butoxy group, a cyclopropoxy group, and a cyclobutoxy group.

[0123] Examples of the halogen atom as Rb.sup.116 and Rb.sup.216 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

##STR00022##

[0124] In Formula (B7), Rb.sup.407, Rb.sup.507, Rb.sup.807, and Rb.sup.907 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

##STR00023##

[0125] In Formula (B8), Rb.sup.408, Rb.sup.508, Rb.sup.808, and Rb.sup.908 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0126] Specific forms and preferred forms of Rb.sup.201 in Formula (B1), Rb.sup.202 in Formula (B2), Rb.sup.204 in Formula (B4), and Rb.sup.205 in Formula (B5) are the same as each other, so that Rb.sup.201, Rb.sup.202, Rb.sup.204, and Rb.sup.205 will be collectively referred to as Rb.sup.200.

[0127] The alkyl group having 1 or more and 3 or less carbon atoms, as Rb.sup.200, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is, for example, preferably 1 or 2 and more preferably 1.

[0128] Examples of the alkyl group having 1 or more and 3 or less carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

[0129] Specific forms and preferred forms of Rb.sup.401 in Formula (B1), Rb.sup.402 in Formula (B2), Rb.sup.403 in Formula (B3), Rb.sup.404 in Formula (B4), Rb.sup.405 in Formula (B5), Rb.sup.406 in Formula (B6), Rb.sup.407 in Formula (B7), and Rb.sup.408 in Formula (B8) are the same as each other, so that Rb.sup.401, Rb.sup.402, Rb.sup.403, Rb.sup.404, Rb.sup.405, Rb.sup.406, Rb.sup.407, and Rb.sup.408 will be collectively referred to as Rb.sup.400.

[0130] The alkyl group having 1 or more and 4 or less carbon atoms, as Rb.sup.400, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is, for example, preferably 1 or more and 3 or less, more preferably 1 or 2, and still more preferably 1.

[0131] Examples of the linear alkyl group having 1 or more and 4 or less carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group.

[0132] Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, an sec-butyl group, and a tert-butyl group.

[0133] Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0134] An alkyl group of the alkoxy group having 1 or more and 6 or less carbon atoms, as Rb.sup.400, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the alkoxy group having 1 or more and 6 or less carbon atoms is, for example, preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

[0135] Examples of the linear alkoxy group having 1 or more and 6 or less carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group.

[0136] Examples of the branched alkoxy group having 3 or more and 6 or less carbon atoms include an isopropoxy group, an isobutoxy group, an sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, an sec-hexyloxy group, and a tert-hexyloxy group.

[0137] Examples of the cyclic alkoxy group having 3 or more and 6 or less carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0138] Examples of the halogen atom as Rb.sup.400 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0139] Specific forms and preferred forms of Rb.sup.501 in Formula (B1), Rb.sup.502 in Formula (B2), Rb.sup.503 in Formula (B3), Rb.sup.504 in Formula (B4), Rb.sup.505 in Formula (B5), Rb.sup.506 in Formula (B6), Rb.sup.507 in Formula (B7), and Rb.sup.508 in Formula (B8) are the same as each other, so that Rb.sup.501, Rb.sup.502, Rb.sup.503, Rb.sup.504, Rb.sup.505, Rb.sup.506, Rb.sup.507, and Rb.sup.508 will be collectively referred to as Rb.sup.500.

[0140] The alkyl group having 1 or more and 4 or less carbon atoms, as Rb.sup.500, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is, for example, preferably 1 or more and 3 or less, more preferably 1 or 2, and still more preferably 1.

[0141] Examples of the linear alkyl group having 1 or more and 4 or less carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group.

[0142] Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, an sec-butyl group, and a tert-butyl group.

[0143] Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0144] An alkyl group of the alkoxy group having 1 or more and 6 or less carbon atoms, as Rb.sup.500, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the alkoxy group having 1 or more and 6 or less carbon atoms is, for example, preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

[0145] Examples of the linear alkoxy group having 1 or more and 6 or less carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group.

[0146] Examples of the branched alkoxy group having 3 or more and 6 or less carbon atoms include an isopropoxy group, an isobutoxy group, an sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, an sec-hexyloxy group, and a tert-hexyloxy group.

[0147] Examples of the cyclic alkoxy group having 3 or more and 6 or less carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0148] Examples of the halogen atom as Rb.sup.500 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0149] Specific forms and preferred forms of Rb.sup.801 in Formula (B1), Rb.sup.802 in Formula (B2), Rb.sup.803 in Formula (B3), Rb.sup.804 in Formula (B4), Rb.sup.805 in Formula (B5), Rb.sup.806 in Formula (B6), Rb.sup.807 in Formula (B7), and Rb.sup.808 in Formula (B8) are the same as each other, so that Rb.sup.801, Rb.sup.802, Rb.sup.803, Rb.sup.804, Rb.sup.805, Rb.sup.806, Rb.sup.807, and Rb.sup.808 will be collectively referred to as Rb.sup.800.

[0150] The alkyl group having 1 or more and 4 or less carbon atoms, as Rb.sup.800, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is, for example, preferably 1 or more and 3 or less, more preferably 1 or 2, and still more preferably 1.

[0151] Examples of the linear alkyl group having 1 or more and 4 or less carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group.

[0152] Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, an sec-butyl group, and a tert-butyl group.

[0153] Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0154] An alkyl group of the alkoxy group having 1 or more and 6 or less carbon atoms, as Rb.sup.800, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the alkoxy group having 1 or more and 6 or less carbon atoms is, for example, preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

[0155] Examples of the linear alkoxy group having 1 or more and 6 or less carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group.

[0156] Examples of the branched alkoxy group having 3 or more and 6 or less carbon atoms include an isopropoxy group, an isobutoxy group, an sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, an sec-hexyloxy group, and a tert-hexyloxy group.

[0157] Examples of the cyclic alkoxy group having 3 or more and 6 or less carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0158] Examples of the halogen atom as Rb.sup.800 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0159] Specific forms and preferred forms of Rb.sup.901 in Formula (B1), Rb.sup.902 in Formula (B2), Rb.sup.903 in Formula (B3), Rb.sup.904 in Formula (B4), Rb.sup.905 in Formula (B5), Rb.sup.906 in Formula (B6), Rb.sup.907 in Formula (B7), and Rb.sup.908 in Formula (B8) are the same as each other, so that Rb.sup.901, Rb.sup.902, Rb.sup.903, Rb.sup.904, Rb.sup.905, Rb.sup.906, Rb.sup.907, and Rb.sup.908 will be collectively referred to as Rb.sup.900.

[0160] The alkyl group having 1 or more and 4 or less carbon atoms, as Rb.sup.900, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is, for example, preferably 1 or more and 3 or less, more preferably 1 or 2, and still more preferably 1.

[0161] Examples of the linear alkyl group having 1 or more and 4 or less carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group.

[0162] Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, an sec-butyl group, and a tert-butyl group.

[0163] Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0164] An alkyl group of the alkoxy group having 1 or more and 6 or less carbon atoms, as Rb.sup.900, may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the alkoxy group having 1 or more and 6 or less carbon atoms is, for example, preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less, and still more preferably 1 or 2.

[0165] Examples of the linear alkoxy group having 1 or more and 6 or less carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group.

[0166] Examples of the branched alkoxy group having 3 or more and 6 or less carbon atoms include an isopropoxy group, an isobutoxy group, an sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, an sec-hexyloxy group, and a tert-hexyloxy group.

[0167] Examples of the cyclic alkoxy group having 3 or more and 6 or less carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0168] Examples of the halogen atom as Rb.sup.900 include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0169] Hereinafter, diol units (B1-1) to (B1-6) are shown as specific examples of the diol unit (B1). The diol unit (B1) is not limited thereto.

##STR00024##

[0170] Hereinafter, diol units (B2-1) to (B2-11) are shown as specific examples of the diol unit (B2). The diol unit (B2) is not limited thereto.

##STR00025## ##STR00026##

[0171] Hereinafter, diol units (B3-1) to (B3-4) are shown as specific examples of the diol unit (B3). The diol unit (B3) is not limited thereto.

##STR00027##

[0172] Hereinafter, diol units (B4-1) to (B4-7) are shown as specific examples of the diol unit (B4). The diol unit (B4) is not limited thereto.

##STR00028##

[0173] Hercinafter, diol units (B5-1) to (B5-6) are shown as specific examples of the diol unit (B5). The diol unit (B5) is not limited thereto.

##STR00029## ##STR00030##

[0174] Hereinafter, diol units (B6-1) to (B6-4) are shown as specific examples of the diol unit (B6). The diol unit (B6) is not limited thereto.

##STR00031##

[0175] Hereinafter, diol units (B7-1) to (B7-3) are shown as specific examples of the diol unit (B7). The diol unit (B7) is not limited thereto.

##STR00032##

[0176] Hereinafter, diol units (B8-1) to (B8-3) are shown as specific examples of the diol unit (B8). The diol unit (B8) is not limited thereto.

##STR00033##

[0177] The diol unit (B) included in the polyarylate resin (PA) may be used alone or in combination of two or more kinds thereof.

[0178] A mass proportion of the diol unit (B) in the polyarylate resin (PA) is, for example, preferably 25% by mass or more and 80% by mass or less.

[0179] In a case where the mass proportion of the diol unit (B) is 25% by mass or greater, peeling of the charge transport layer can be further suppressed. From the viewpoint, the mass proportion of the diol unit (B) is, for example, more preferably 30% by mass or greater and still more preferably 35% by mass or greater.

[0180] In a case where the mass proportion of the diol unit (B) is 80% by mass or less, the solubility in a coating solution for forming the charge transport layer is maintained, and thus the abrasion resistance can be improved. From the viewpoint, the mass proportion of the diol unit (B) is, for example, more preferably 75% by mass or less and still more preferably 70% by mass or less.

[0181] The polyarylate resin (PA) may have other diol units in addition to the diol unit (B). Examples of other diol units include aliphatic diol (such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, and neopentyl glycol) units, and alicyclic diol (such as cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A) units. The diol units included in the polyarylate resin (PA) may be used alone or in combination of two or more kinds thereof.

[0182] A terminal of the polyarylate resin (PA) may be sealed or modified with a terminal-sealing agent, a molecular weight modifier, or the like used in a case of the production. Examples of the terminal-sealing agent or the molecular weight modifier include monohydric phenol, monovalent acid chloride, monohydric alcohol, and monovalent carboxylic acid.

[0183] Examples of the monohydric phenol include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, 0-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, a 2,6-dimethylphenol derivative, a 2-methylphenol derivative, o-phenylphenol, m-phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl) propane, 2-phenyl-2-(2-hydroxyphenyl) propane, and 2-phenyl-2-(3-hydroxyphenyl) propane.

[0184] Examples of the monovalent acid chloride include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenylchloroformate, acetic acid chloride, butyric acid chloride, octyl acid chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzene phosphonyl chloride, and substituents thereof.

[0185] Examples of the monohydric alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenethyl alcohol.

[0186] Examples of the monovalent carboxylic acid include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0187] The weight-average molecular weight of the polyarylate resin (PA) is, for example, preferably 30,000 or greater and 300,000 or less, more preferably 40,000 or greater and 250,000 or less, and still more preferably 50,000 or greater and 200,000 or less.

[0188] The molecular weight of the polyarylate resin (PA) is a molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). The GPC is carried out by using tetrahydrofuran as an eluent.

[0189] The polyarylate resin (PA) can be obtained by polycondensing a monomer providing the dicarboxylic acid unit (A), a monomer providing the diol unit (B), and other monomers as necessary using a method in the related art. Examples of the method of polycondensing monomers include an interfacial polymerization method, a solution polymerization method, and a melt polymerization method. The interfacial polymerization method is a polymerization method of mixing a divalent carboxylic acid halide dissolved in an organic solvent that is incompatible with water and dihydric alcohol dissolved in an alkali aqueous solution to obtain polyester. Examples of documents related to the interfacial polymerization method include W. M. EARECKSON, J. Poly. Sci., XL399, 1959, and JP1965-1959B (JP-S40-1959B). Since the interfacial polymerization method enables the reaction to proceed faster than the reaction carried out by the solution polymerization method and also enables suppression of hydrolysis of the divalent carboxylic acid halide, as a result, a high-molecular-weight polyarylate resin (PA) can be obtained.

[0190] Examples of other resins contained in the charge transport layer include a polyarylate resin other than resins described above, a polycarbonate resin, a polyester resin other than the polyarylate resin, a methacrylic resin, an acrylic resin, a polyvinyl chloride resin, a polyvinylidene chloride resin, a polystyrene resin, a polyvinyl acetate resin, a styrene-butadiene copolymer, a vinylidene chloride-acrylonitrile copolymer, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinyl acetate-maleic anhydride copolymer, a silicone resin, a silicone alkyd resin, a phenol-formaldehyde resin, a styrene-alkyd resin, poly-N-vinylcarbazole, and polysilane. Two or more kinds of resins may be used in any combination of these resins.

[0191] From the viewpoint of abrasion resistance of the charge transport layer and local deterioration suppression properties of electrical properties after long-term printing, for example, the resin contained in the charge transport layer preferably includes at least one of a polyarylate resin or a polycarbonate resin, and more preferably includes a polyarylate resin and a polycarbonate resin. For example, a form in which a polyarylate resin and a polycarbonate resin are contained is also preferable from the viewpoint of forming a fine phase separation structure in the charge transport layer.

[0192] From the viewpoint of forming a fine phase separation structure in the charge transport layer, a proportion of the polyarylate resin in a total amount of the polyarylate resin and the polycarbonate resin contained in the charge transport layer is, for example, 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 still more preferably 30% by mass or more and 70% by mass or less.

[0193] As the polycarbonate resin, for example, a polycarbonate resin in which constitutional units having an aromatic ring are continuous is preferable. In the polycarbonate resin, resin molecules are bonded to each other by an intermolecular force due to stacking of aromatic rings, and thus the abrasion resistance of the charge transport layer is improved. For example, preferred aspects of the polycarbonate resin include, specifically, the polycarbonate resin disclosed in JP2023-121553A. For example, a polycarbonate resin used in Examples described later is shown as a more preferred aspect of the polycarbonate resin.

[0194] As a combination of the polyarylate resin and the polycarbonate resin, for example, a combination of resins each having a constitutional unit containing a biphenyl represented by Formula (BP) is preferable.

##STR00034##

[0195] In Formula (BP), j is an integer of 0 or greater and 4 or less, j pieces of R.sup.1's are each independently a methyl group or an ethyl group, k is an integer of 0 or greater and 4 or less, and k pieces of R.sup.2's are each independently a methyl group or an ethyl group.

[0196] The biphenyl represented by Formula (BP) may be an entire structure or a part of a structure obtained by removing an ester bond (C(O)O) or a carbonate bond (OC(O)O) from the constitutional unit including the biphenyl represented by Formula (BP). In other words, the right end and the left end of the biphenyl represented by Formula (BP) may be each independently bonded to an ester bond or a carbonate bond directly or bonded to an ester bond or a carbonate bond via another atom or an atomic group.

[0197] j is an integer of 0 or greater and 4 or less, for example, preferably an integer of 0 or greater and 3 or less, more preferably an integer of 0 or greater and 2 or less, still more preferably 0 or 1, and particularly preferably 0.

[0198] In a case where j is an integer of 1 or greater, j pieces of R.sup.1's are each independently a methyl group or an ethyl group and, for example, preferably a methyl group.

[0199] k is an integer of 0 or greater and 4 or less, for example, preferably an integer of 0 or greater and 3 or less, more preferably an integer of 0 or greater and 2 or less, still more preferably 0 or 1, and particularly preferably 0.

[0200] In a case where k is an integer of 1 or greater, k pieces of R.sup.2's are each independently a methyl group or an ethyl group and, for example, preferably a methyl group.

[0201] The biphenyl represented by Formula (BP) is, for example, preferably 4,4-biphenyl with respect to a linking position in a main chain.

[0202] As a combination of the polyarylate resin and the polycarbonate resin, for example, a combination of a polyarylate resin having at least one of a dicarboxylic acid unit (A2-3) or a diol unit (B7-1) and a polycarbonate resin having a constitutional unit (Cb7-1) is particularly preferable.

##STR00035##

[0203] The charge transport layer preferably further contains, for example, a phenolic compound.

[0204] Examples of the phenolic compound contained 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, and Z). The phenolic compound may be used alone or in combination of two or more kinds thereof.

[0205] Examples of the phenolic compound also include a hindered phenolic compound.

[0206] From the viewpoint of suppressing oxidative deterioration of the charge transport layer, the phenolic compound preferably includes, for example, a hindered phenolic compound. The hindered phenolic compound is generally a compound in which at least one of ortho positions of a hydroxy group of phenol is substituted with a bulky group, and exhibition of an oxidation inhibiting action of the composition is shown.

[0207] Examples of the hindered phenolic compound include the following. [0208] Alkylated monophenol compound and derivative thereof: for example, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, octyl-3,5-di-t-butyl-4-hydroxy-hydrocinnamate [0209] Alkylated hydroquinone compound and a derivative thereof: for example, 2,5-di-t-butylhydroquinone, 2,5-di-t-amylhydroquinone [0210] Alkyl thiomethyl phenol compound and a derivative thereof: for example, 2,4-dioctylthiomethyl-6-t-butylphenol, 2,4-dioctylthiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, and 2,6-didodecylthiomethyl-4-nonylphenol

[0211] Alkylidene bisphenol compound and derivative thereof: for example, 4,4-butylidenebis(6-t-butyl-3-methylphenol), 2,2-methylenebis(6-t-butyl-4-methylphenol), 2,2-methylenebis(6-t-butyl-4-ethylphenol), 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, and 3,9-bis[2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane

[0212] Examples of a commercially available product of the hindered phenolic compound include ADEKA STAB AO-80, ADEKA STAB AO-60, ADEKA STAB AO-50, ADEKA STAB AO-40, ADEKA STAB AO-30, ADEKA STAB AO-20, ADEKA STAB AO-330 (all manufactured by ADEKA Corporation), Irganox 1010, Irganox 245, Irganox 1076, Irganox 1520 (all manufactured by BASF Japan Ltd.), and Sumilizer GA-80, Sumilizer GM, and Sumilizer GS (all manufactured by Sumitomo Chemical Co., Ltd.).

[0213] The hindered phenolic compound may be used alone or in combination of two or more kinds thereof.

[0214] From the viewpoint of promoting phase separation of two or more kinds of resins during the formation of the charge transport layer and forming a fine phase separation structure in the charge transport layer, a content of the phenolic compound contained in the charge transport layer is, for example, preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and still more preferably 1% by mass or more and 5% by mass or less with respect to a total mass of the charge transport layer.

[0215] In the charge transport layer, for example, a proportion of the fluororesin particles in the layer is preferably 5% by mass or less, more preferably 1% by mass or less, and still more preferably 0% by mass (that is, the charge transport layer does not contain the fluororesin particles).

[0216] Since there is a high possibility that the regulations on manufacturing and use of the organic fluorine compounds are strengthened in the future, for example, a content of the fluororesin particles is preferably within the above-described range.

[0217] For example, the charge transport layer preferably contains a charge transport material.

[0218] Examples of the charge transport material include a quinone-based compound such as p-benzoquinone, chloranil, bromanil, or anthraquinone; a tetracyanoquinodimethane-based compound; a fluorenone compound such as 2,4,7-trinitrofluorenone; a xanthone compound; a benzophenone-based compound; a cyanovinyl-based compound; and an electron-transporting compound such as an ethylene-based compound. Examples of the charge transport material also include a positive hole-transporting compound such as a triarylamine-based compound, a benzidine-based compound, an arylalkane-based compound, an aryl-substituted ethylene-based compound, a stilbene-based compound, an anthracene-based compound, and a hydrazone-based compound. These charge transport materials are used alone or in combination of two or more kinds thereof, but are not limited thereto.

[0219] The charge transport layer may be a layer containing a polymer charge transport material.

[0220] Examples of the polymer charge transport material include known chemical substances having charge transport properties, such as poly-N-vinylcarbazole and polysilane. For example, a polyester-based polymer charge transport material is preferable. The polymer charge transport material may be used alone or in combination with a binder resin.

[0221] Examples of the charge transport material or the polymer charge transport material include a polycyclic aromatic compound, an aromatic nitro compound, an aromatic amine compound, a heterocyclic compound, a hydrazone compound, a styryl compound, an enamine compound, a benzidine compound, a triarylamine compound (particularly, a triphenylamine compound), a diamine compound, an oxadiazole compound, a carbazole compound, an organic polysilane compound, a pyrazoline compound, an indole compound, an oxazole compound, an isoxazole compound, a thiazole compound, a thiadiazole compound, an imidazole compound, a pyrazole compound, a triazole compound, a cyano compound, a benzofuran compound, an aniline compound, a butadiene compound, and a resin containing a group derived from these substances. Specific examples thereof include compounds described in paragraphs 0078 to 0080 of JP2021-117377A, paragraphs 0046 to 0048 of JP2019-035900A, paragraphs 0052 and 0053 of JP2019-012141A, paragraphs 0122 to 0134 of JP2021-071565A, paragraphs 0101 to 0110 of JP2021-015223A, paragraph 0116 of JP2013-097300A, paragraphs 0309 to 0316 of WO2019/070003A, paragraphs 0103 to 0107 of JP2018-159087A, and paragraphs 0102 to 0113 of JP2021-148818A.

[0222] From the viewpoint of the charge mobility, for example, it is preferable that the charge transport material contains at least one selected from the group consisting of a chemical substance (C1) represented by Formula (C1), a chemical substance (C2) represented by Formula (C2), a chemical substance (C3) represented by Formula (C3), and a chemical substance (C4) represented by Formula (C4).

##STR00036##

[0223] In Formula (C1), Ar.sup.T1, Ar.sup.T2, and Ar.sup.T3 are each independently an aryl group, C.sub.6H.sub.4C(R.sup.T4)C(R.sup.T5)(R.sup.T6), or C.sub.6H.sub.4CHCHCHC(R.sup.T7)(R.sup.T8). R.sup.T4, R.sup.T5, R.sup.T6, R.sup.T7, and R.sup.T8 are each independently a hydrogen atom, an alkyl group, or an aryl group. In a case where R.sup.T5 and R.sup.T6 are aryl groups, the aryl groups may be linked through a divalent group of C(R.sup.51)(R.sup.32) and/or C(R.sup.61)C(R.sup.62). R.sup.51, R.sup.52, R.sup.61, and R.sup.62 are each independently a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms.

[0224] The group in Formula (C1) may be substituted with a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, an alkoxy group having 1 or more and 5 or less carbon atoms, or a substituted amino group substituted with an alkyl group having 1 or more and 3 or less carbon atoms.

[0225] From the viewpoint of the charge mobility, as the chemical substance (C1), for example, a chemical substance containing at least one of an aryl group or C.sub.6H.sub.4CHCHCHC(R.sup.17)(R.sup.T8) is preferable, and a chemical substance (C1) represented by Formula (C1) is more preferable.

##STR00037##

[0226] In Formula (C1), R.sup.T111, R.sup.T112, R.sup.T121, R.sup.T122, R.sup.T131, and R.sup.T132 are each independently a hydrogen atom, a halogen atom, an alkyl group (for example, preferably an alkyl group having 1 or more and 3 or less carbon atoms), an alkoxy group (for example, preferably an alkoxy group having 1 or more and 3 or less carbon atoms), a phenyl group, or a phenoxy group. Tj1, Tj2, Tj3, Tk1, Tk2, and Tk3 are each independently 0, 1, or 2.

##STR00038##

[0227] In Formula (C2), R.sup.T201, R.sup.T202, R.sup.T211, and R.sup.T212 are each independently a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, an alkoxy group having 1 or more and 5 or less carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, C(R.sup.T21)C(R.sup.T22)(R.sup.T23), or CHCHCHC(R.sup.T24)(R.sup.T25). R.sup.T21, R.sup.T22, R.sup.T23, R.sup.T24, and R.sup.T25 are each independently a hydrogen atom, an alkyl group, or an aryl group. R.sup.T221 and R.sup.T222 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, or an alkoxy group having 1 or more and 5 or less carbon atoms. Tm1, Tm2, Tn1, and Tn2 are each independently 0, 1, or 2.

[0228] The group in Formula (C2) may be substituted with a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, an alkoxy group having 1 or more and 5 or less carbon atoms, or a substituted amino group substituted with an alkyl group having 1 or more and 3 or less carbon atoms.

[0229] From the viewpoint of the charge mobility, as the chemical substance (C2), for example, a chemical substance containing at least one of an alkyl group, an aryl group, or CHCHCHC(R.sup.T24)(R.sup.T25) is preferable, and a chemical substance containing two of an alkyl group, an aryl group, or CHCHCHC(R.sup.T24)(R.sup.T25) is more preferable.

##STR00039##

[0230] In Formula (C3), R.sup.T301, R.sup.T302, R.sup.T311, and R.sup.T312 are each independently a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, an alkoxy group having 1 or more and 5 or less carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, C(R.sup.T31)C(R.sup.T32)(R.sup.T33), or CHCHCHC(R.sup.T34)(R.sup.T35). R.sup.T31, R.sup.T32, R.sup.T33, R.sup.T34, and R.sup.T35 are each independently a hydrogen atom, an alkyl group, or an aryl group. R.sup.T321, R.sup.T322, and R.sup.T331 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, or an alkoxy group having 1 or more and 5 or less carbon atoms. To1, To2, Tp1, Tp2, Tq1, Tq2, and Tr1 are each independently 0, 1, or 2.

[0231] The group in Formula (C3) may be substituted with a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, an alkoxy group having 1 or more and 5 or less carbon atoms, or a substituted amino group substituted with an alkyl group having 1 or more and 3 or less carbon atoms.

##STR00040##

[0232] In Formula (C4), R.sup.T401, R.sup.T402, R.sup.T411, and R.sup.T412 are each independently a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, an alkoxy group having 1 or more and 5 or less carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, C(R.sup.T41)C(R.sup.T42)(R.sup.T43), or CHCHCHC(R.sup.T44)(R.sup.T45). R.sup.T41, R.sup.T42, R.sup.T43, R.sup.T44, and R.sup.T45 are each independently a hydrogen atom, an alkyl group, or an aryl group. R.sup.T421, R.sup.T422, and R.sup.T431 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, or an alkoxy group having 1 or more and 5 or less carbon atoms. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 are each independently 0, 1, or 2.

[0233] The group in Formula (C4) may be substituted with a halogen atom, an alkyl group having 1 or more and 5 or less carbon atoms, an alkoxy group having 1 or more and 5 or less carbon atoms, or a substituted amino group substituted with an alkyl group having 1 or more and 3 or less carbon atoms.

[0234] The content of the charge transport material contained in the charge transport layer is, for example, preferably 20% by mass or greater and 70% by mass or less with respect to the total mass of the charge transport layer.

[0235] The charge transport layer may also contain other known additives.

[0236] The formation of the charge transport layer is not particularly limited, and a known formation method is used. For example, the charge transport layer is obtained by forming a coating film of a coating solution for forming a charge transport layer, which is obtained by adding the above-described components to a solvent, drying the coating film, and heating the coating film as necessary.

[0237] Examples of the solvent for preparing the coating solution for forming the charge transport layer include typical organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride; and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. The solvents are used alone or in a form of a mixture of two or more kinds thereof.

[0238] Examples of the coating method of coating the charge generation layer with the coating solution for forming the charge transport layer include typical methods such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method.

[0239] A layer thickness of the charge transport layer may be set according to a function of the layer.

[0240] The layer thickness of the charge transport layer is, for example, preferably 5 m or greater and 50 m or less, more preferably 8 m or greater and 45 m or less, and still more preferably 10 m or greater and 40 m or less.

Charge Generation Layer

[0241] A charge generation layer is, for example, a layer containing a charge generation material and a binder resin. In addition, the charge generation layer may be a deposition layer of the charge generation material. For example, the deposition layer of the charge generation material is preferable in a case where an incoherent light source such as a light emitting diode (LED) and an organic electro-luminescence (EL) image array is used.

[0242] In the charge generation layer, a value of a content of the binder resin to a total content of the binder resin and the charge generation material is more than 0.4 and less than 0.7, and from the viewpoint of local deterioration suppression properties of electrical properties after long-term printing, for example, preferably 0.41 or more and 0.65 or less, more preferably more than 0.43 and less than 0.60, and particularly preferably more than 0.43 and less than 0.50.

[0243] The charge generation material contains chlorogallium phthalocyanine.

[0244] Other known charge generation materials may be used in combination. However, for example, from the viewpoint of local deterioration suppression properties of electrical properties after long-term printing, it is preferable that the other known charge generation materials are not used in combination.

[0245] The binder resin used for the charge generation layer is selected from a wide range of insulating resins, and the binder resin may be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane.

[0246] Examples of the binder resin include a polyvinyl butyral resin, a polyarylate resin (polycondensate of bisphenols and aromatic divalent carboxylic acid, or the like), a polycarbonate resin, a polyester resin, a phenoxy resin, a vinyl chloride-vinyl acetate copolymer, a polyamide resin, an acrylic resin, a polyacrylamide resin, a polyvinylpyridine resin, a cellulose resin, a urethane resin, an epoxy resin, casein, a polyvinyl alcohol resin, and a polyvinylpyrrolidone resin. Here, the term insulating means that a volume resistivity is 110.sup.13 .Math.cm or more.

[0247] Among these, as the binder resin, from the viewpoint of local deterioration suppression properties of electrical properties after long-term printing, for example, a vinyl acetate-based resin or a polyvinyl butyral-based resin is preferable, a vinyl chloride-vinyl acetate copolymer or a polyvinyl butyral resin is more preferable, and a vinyl chloride-vinyl acetate copolymer is particularly preferable.

[0248] These binder resins are used alone or in the form of a mixture of two or more kinds thereof.

[0249] The charge generation layer may also contain other known additives.

[0250] The formation of the charge generation layer is not particularly limited, and a known forming method is used. For example, a coating film of a coating solution for forming a charge generation layer in which the above-described components are added to a solvent is formed, and the coating film is dried and, as necessary, heated. The charge generation layer may be formed by a vapor deposition of the charge generation material. For example, the formation of the charge generation layer by the vapor deposition is particularly preferable in a case where the fused ring aromatic pigment or the perylene pigment is used as the charge generation material.

[0251] Examples of the solvent 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 are used alone or in the form of a mixture of two or more kinds thereof.

[0252] As a method of dispersing particles (for example, the charge generation material) in the coating solution for forming the charge generation layer, for example, a media disperser such as a ball mill, a vibration ball mill, an attritor, a sand mill, and a horizontal sand mill, or a medialess disperser such as a stirrer, an ultrasonic disperser, a roll mill, and a high-pressure homogenizer is used. Examples of the high-pressure homogenizer include a collision type homogenizer in which a dispersion liquid is dispersed by a liquid-liquid collision or a liquid-wall collision in a high-pressure state, and a penetration type homogenizer in which a dispersion liquid is dispersed by penetrating the liquid through a fine flow path in a high-pressure state. During the dispersion, it is effective to set the average particle diameter of the charge generation material in the coating solution for forming a charge generation layer to 0.5 m or less, for example, preferably 0.3 m or less, and more preferably 0.15 m or less.

[0253] Examples of the method of coating the undercoat layer (or the interlayer) with the coating solution for forming a charge generation layer include typical methods such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method.

[0254] The layer thickness of the charge generation layer is set to be, for example, preferably in a range of 0.1 m or greater and 5.0 m or less and more preferably in a range of 0.2 m or greater and 2.0 m or less.

Conductive Substrate

[0255] Examples of the conductive substrate include metal plates, metal drums, metal belts, or the like, containing a metal (such as aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, and platinum) or an alloy (such as stainless steel). In addition, examples of the conductive substrate also include paper, a resin film, a belt, or the like, that is obtained by being coated, vapor-deposited, or laminated with a conductive compound (such as a conductive polymer and indium oxide), a metal (such as aluminum, palladium, and gold) or an alloy. Here, the term conductive denotes that a volume resistivity is less than 110.sup.13 .Math.cm.

[0256] In a case where the electrophotographic photoreceptor is used in a laser printer, for example, it is preferable that the surface of the conductive substrate is roughened such that a centerline average roughness Ra thereof is 0.04 m or greater and 0.5 m or less for the purpose of suppressing interference fringes from occurring in a case of irradiation with laser beams. In a case where incoherent light is used as a light source, roughening of the surface to prevent interference fringes is not particularly necessary, and it is suitable for longer life because occurrence of defects due to the roughness of the surface of the conductive substrate is suppressed.

[0257] Examples of the roughening method include wet honing performed by suspending an abrasive in water and spraying the suspension to the conductive substrate, centerless grinding performed by pressure-welding the conductive substrate against a rotating grindstone and continuously grinding the conductive substrate, and an anodizing treatment.

[0258] Examples of the roughening method also include a method of dispersing conductive or semi-conductive powder in a resin without roughening the surface of the conductive substrate to form a layer on the surface of the conductive substrate, and performing roughening using the particles dispersed in the layer.

[0259] The roughening treatment performed by anodization is a treatment of forming an oxide film on the surface of the conductive substrate by carrying out anodization in an electrolytic solution using a conductive substrate made of a metal (for example, aluminum) as an anode. Examples of the electrolytic solution include a sulfuric acid solution and an oxalic acid solution. However, a porous anodized film formed by the anodization is chemically active in a natural state, is easily contaminated, and has a large resistance fluctuation depending on the environment. Therefore, for example, it is preferable that a sealing treatment is performed on the porous anodized film so that the fine pores of the oxide film are closed by volume expansion due to a hydration reaction in pressurized steam or boiling water (a metal salt such as nickel may be added thereto) for a change into a more stable a hydrous oxide.

[0260] The film thickness of the anodized film is, for example, preferably 0.3 m or greater and 15 m or less. In a case where the film thickness is in the above-described range, the barrier properties against injection tend to be exhibited, and an increase in the residual potential due to repeated use tends to be suppressed.

[0261] The conductive substrate may be subjected to a treatment with an acidic treatment liquid or a boehmite treatment.

[0262] The treatment with an acidic treatment liquid is carried out, for example, as follows. First, an acidic treatment liquid containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. As a blending proportion of the phosphoric acid, chromic acid, and hydrofluoric acid to the acidic treatment liquid, for example, a concentration of the phosphoric acid may be in a range of 10% by mass or more and 11% by mass or less, a concentration of the chromic acid may be in a range of 3% by mass or more and 5% by mass or less, and a concentration of the hydrofluoric acid may be in a range of 0.5% by mass or more and 2% by mass or less, and a concentration of all of these acids may be in a range of 13.5% by mass or more and 18% by mass or less. A treatment temperature is, for example, preferably 42 C. or higher and 48 C. or lower. The film thickness of the coating film is, for example, preferably 0.3 m or greater and 15 m or less.

[0263] The boehmite treatment is carried out, for example, by dipping the conductive substrate in pure water at 90 C. or higher and 100 C. or lower for 5 minutes to 60 minutes or by bringing the conductive substrate into contact with heated steam at 90 C. or higher and 120 C. or lower for 5 minutes to 60 minutes. A film thickness of the coating film is, for example, preferably 0.1 m or more and 5 m or less. This coating film may be further subjected to the anodizing treatment using an electrolytic solution having low film solubility, such as adipic acid, boric acid, a borate, a phosphate, a phthalate, a maleate, a benzoate, a tartrate, or a citrate.

Undercoat Layer

[0264] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0265] Examples of the inorganic particles include inorganic particles having a powder resistance (volume resistivity) of 110.sup.2 .Math.cm or more and 110.sup.11 .Math.cm or less.

[0266] Among these, as the inorganic particles having the above-described resistance value, for example, metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles may be used, and zinc oxide particles are particularly preferable.

[0267] A specific surface area of the inorganic particles, measured by a BET method, may be, for example, 10 m.sup.2/g or more.

[0268] The volume average particle diameter of the inorganic particles may be, for example, 50 nm or greater and 2,000 nm or less (for example, preferably 60 nm or greater and 1,000 nm or less).

[0269] The content of the inorganic particles is, for example, preferably 10% by mass or greater and 80% by mass or less and more preferably 40% by mass or greater and 80% by mass or less with respect to the amount of the binder resin.

[0270] The inorganic particles may be subjected to a surface treatment. As the inorganic particles, inorganic particles subjected to different surface treatments or inorganic particles having different particle diameters may be used in the form of a mixture of two or more kinds thereof.

[0271] Examples of the surface treatment agent include a silane coupling agent, a titanate-based coupling agent, an aluminum-based coupling agent, and a surfactant. In particular, for example, a silane coupling agent is preferable, and a silane coupling agent containing an amino group is more preferable.

[0272] Examples of the silane coupling agent containing an amino group include 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, but are not limited thereto.

[0273] The silane coupling agent may be used in the form of a mixture of two or more kinds thereof. For example, the silane coupling agent having an amino group and other silane coupling agents may be used in combination. Examples of other silane coupling agents include vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy) silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane, but are not limited thereto.

[0274] The surface treatment method using a surface treatment agent may be any method as long as the method is a known method, and any of a dry method or a wet method may be used.

[0275] The treatment amount of the surface treatment agent is, for example, preferably 0.5% by mass or greater and 10% by mass or less with respect to the amount of the inorganic particles.

[0276] Here, for example, the undercoat layer may contain an electron-accepting compound (acceptor compound) together with the inorganic particles from the viewpoint of enhancing long-term stability of electrical properties and carrier blocking properties.

[0277] Examples of the electron-accepting compound include electron-transporting substances, for example, a compound having an anthraquinone structure; a quinone-based compound such as chloranil and bromanil; a tetracyanoquinodimethane-based compound; a fluorenone compound such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; an oxadiazole-based compound 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; a xanthone-based compound; a thiophene compound; a diphenoquinone compound such as 3,3,5,5-tetra-t-butyldiphenoquinone; and a benzophenone compound.

[0278] In particular, as the electron-accepting compound, for example, a compound having an anthraquinone structure is preferable. As the compound having an anthraquinone structure, for example, a hydroxyanthraquinone compound, an aminoanthraquinone compound, or an aminohydroxyanthraquinone compound is preferable; and specifically, anthraquinone, alizarin, quinizarin, anthrarufin, purpurin, or a derivative thereof is preferable.

[0279] The electron-accepting compound may be contained in the undercoat layer in a state of being dispersed with inorganic particles or in a state of being attached to the surface of each inorganic particle.

[0280] Examples of the method of attaching the electron-accepting compound to the surface of the inorganic particle include a dry method and a wet method.

[0281] The dry method is, for example, a method of attaching the electron-accepting compound to the surface of the inorganic particles by adding the electron-accepting compound dropwise to the inorganic particles directly or by dissolving the electron-accepting compound in an organic solvent while stirring the inorganic particles with a mixer having a large shearing force and spraying the mixture together with dry air or nitrogen gas. For example, the dropwise addition or spraying of the electron-accepting compound may be performed at a temperature equal to or lower than a boiling point of the solvent. After the dropwise addition or spraying of the electron-accepting compound, the mixture may be further baked at 100 C. or higher. The baking is not particularly limited as long as the temperature and the time are adjusted such that the electrophotographic characteristics can be obtained.

[0282] The wet method is, for example, a method of attaching the electron-accepting compound to the surface of the inorganic particles by adding the electron-accepting compound to inorganic particles while dispersing the inorganic particles in a solvent by performing using a stirrer, an ultrasonic disperser, a sand mill, an attritor, or a ball mill, stirring or dispersing the mixture, and removing the solvent. The solvent removing method is carried out by, for example, filtration or distillation so that the solvent is distilled off. After removal of the solvent, the mixture may be further baked at 100 C. or higher. The baking is not particularly limited as long as the temperature and the time are adjusted such that electrophotographic characteristics can be obtained. In the wet method, the moisture contained in the inorganic particles may be removed before the electron-accepting compound is added, and examples thereof include a method of removing the moisture while stirring and heating the moisture in a solvent and a method of removing the moisture by azeotropically boiling the moisture with a solvent.

[0283] The electron-accepting compound may be attached to the surface before or after the inorganic particles are subjected to a surface treatment with a surface treatment agent or simultaneously with the surface treatment performed on the inorganic particles with a surface treatment agent.

[0284] The content of the electron-accepting compound may be, for example, 0.01% by mass or greater and 20% by mass or less and is preferably 0.01% by mass or greater and 10% by mass or less with respect to the amount of the inorganic particles.

[0285] Examples of the binder resin used for the undercoat layer include known polymer compounds such as an acetal resin (such as polyvinyl butyral), a polyvinyl alcohol resin, a polyvinyl acetal resin, a casein resin, a polyamide resin, a cellulose resin, gelatin, a polyurethane resin, a polyester resin, an unsaturated polyester resin, a methacrylic resin, an acrylic resin, a polyvinyl chloride resin, a polyvinyl acetate resin, a vinyl chloride-vinyl acetate-maleic anhydride resin, a silicone resin, a silicone-alkyd resin, a urea resin, a phenol resin, a phenol-formaldehyde resin, a melamine resin, a urethane resin, an alkyd resin, and an epoxy resin, a zirconium chelate compound, a titanium chelate compound, an aluminum chelate compound, a titanium alkoxide compound, an organic titanium compound, and known materials such as a silane coupling agent.

[0286] Examples of the binder resin used for the undercoat layer include a charge-transporting resin containing a charge-transporting group, and a conductive resin (such as polyaniline).

[0287] Among these, as the binder resin used for the undercoat layer, for example, a resin insoluble in a coating solvent of the upper layer is preferable, and a resin obtained by reaction between a curing agent and at least one resin selected from the group consisting of a thermosetting resin such as a urea resin, a phenol resin, a phenol-formaldehyde resin, a melamine resin, a urethane resin, an unsaturated polyester resin, an alkyd resin, or an epoxy resin; a polyamide resin, a polyester resin, a polyether resin, a methacrylic resin, an acrylic resin, a polyvinyl alcohol resin, and a polyvinyl acetal resin is particularly preferable.

[0288] In a case where these binder resins are used in combination of two or more kinds thereof, the mixing ratio thereof is set as necessary.

[0289] The undercoat layer may contain various additives for improving the electrical properties, the environmental stability, and the image quality.

[0290] Examples of the additive include known materials such as an electron-transporting pigment such as a polycyclic condensed pigment or an azo-based pigment, a zirconium chelate compound, a titanium chelate compound, an aluminum chelate compound, a titanium alkoxide compound, an organic titanium compound, and a silane coupling agent. The silane coupling agent is used for a surface treatment of the inorganic particles as described above, but may be further added to the undercoat layer as an additive.

[0291] Examples of the silane coupling agent serving as an additive include vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy) silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0292] Examples of the zirconium chelate compound include zirconium butoxide, ethyl zirconium acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl zirconium butoxide acetoacetate, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium butoxide methacrylate, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0293] Examples of the titanium chelate compound include tetraisopropyl titanate, tetranormal butyl titanate, a 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 triethanol aminate, and polyhydroxy titanium stearate.

[0294] Examples of the aluminum chelate compound include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0295] These additives may be used alone or in the form of a mixture or a polycondensate of a plurality of compounds.

[0296] The undercoat layer may have, for example, a Vickers hardness of 35 or greater.

[0297] For example, the surface roughness (ten-point average roughness) of the undercoat layer may be adjusted to from 1/(4n) (n is a refractive index of an upper layer) of a laser wavelength for exposure to be used to suppress moire fringes.

[0298] Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of the resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. In addition, the surface of the undercoat layer may be polished to adjust the surface roughness. Examples of the polishing method include buff polishing, a sandblast treatment, wet honing, and a grinding treatment.

[0299] The formation of the undercoat layer is not particularly limited, and a known forming method is used. For example, a coating film of a coating solution for forming an undercoat layer in which the above-described components are added to a solvent is formed, and the coating film is dried and, as necessary, heated.

[0300] Examples of the solvent for preparing the coating solution for forming an undercoat layer include known organic solvents such as an alcohol-based solvent, an aromatic hydrocarbon solvent, a halogenated hydrocarbon solvent, a ketone-based solvent, a ketone alcohol-based solvent, an ether-based solvent, and an ester-based solvent.

[0301] Specific examples of the solvent include typical 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.

[0302] Examples of the method of dispersing the inorganic particles in a case of preparing the coating solution for forming an undercoat layer include known methods such as a roll mill, a ball mill, a vibration ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0303] Examples of the method of coating the conductive substrate with the coating solution for forming an undercoat layer include typical coating methods such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, and a curtain coating method.

[0304] The layer thickness of the undercoat layer is set to be, for example, preferably 15 m or greater and more preferably in a range of 20 m or greater and 50 m or less.

Interlayer

[0305] The interlayer is, for example, a layer containing a resin. Examples of the resin used for the interlayer include polymer compounds such as an acetal resin (for example, polyvinyl butyral or the like), a polyvinyl alcohol resin, a polyvinyl acetal resin, a casein resin, a polyamide resin, a cellulose resin, gelatin, a polyurethane resin, a polyester resin, a methacrylic resin, an acrylic resin, a polyvinyl chloride resin, a polyvinyl acetate resin, a vinyl chloride-vinyl acetate-maleic anhydride resin, a silicone resin, a silicone-alkyd resin, a phenol-formaldehyde resin, and a melamine resin.

[0306] The interlayer may be a layer containing an organometallic compound. Examples of the organometallic compound used for the interlayer include organometallic compounds containing a metal atom such as zirconium, titanium, aluminum, manganese, and silicon.

[0307] The compounds used for the interlayer may be used alone or in the form of a mixture or a polycondensate of a plurality of compounds.

[0308] Among these, it is preferable that the interlayer is, for example, a layer containing an organometallic compound having a zirconium atom or a silicon atom.

[0309] The formation of the interlayer is not particularly limited, and a known forming method is used. For example, a coating film of a coating solution for forming an interlayer in which the above-described components are added to a solvent is formed, and the coating film is dried and, as necessary, heated.

[0310] Examples of the coating method of forming the interlayer include typical methods such as a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, an air knife coating method, and a curtain coating method.

[0311] The layer thickness of the interlayer is set to be, for example, preferably in a range of 0.1 m or greater and 3 m or less. The interlayer may be used as the undercoat layer.

Image Forming Apparatus and Process Cartridge

[0312] An image forming apparatus according to the present exemplary embodiment includes the electrophotographic photoreceptor, a charging device that charges a surface of the electrophotographic photoreceptor, an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image, a transfer device that transfers the toner image to a surface of a recording medium, and a cleaning device that cleans the surface of the electrophotographic photoreceptor. Further, the electrophotographic photoreceptor according to the present exemplary embodiment is employed as the electrophotographic photoreceptor.

[0313] In the image forming apparatus according to the present exemplary embodiment, the cleaning device has a cleaning blade that comes into contact with an outer peripheral surface of the photoreceptor, and cleans a surface of the photoreceptor after transfer of the toner image and before charging by the cleaning blade.

[0314] As the image forming apparatus according to the present exemplary embodiment, known image forming apparatuses such as an apparatus including a fixing device that fixes a toner image transferred to the surface of a recording medium; a direct transfer type apparatus that transfers a toner image formed on the surface of an electrophotographic photoreceptor directly to a recording medium; an intermediate transfer type apparatus that primarily transfers a toner image formed on the surface of an electrophotographic photoreceptor to the surface of an intermediate transfer member and secondarily transfers the toner image transferred to the surface of the intermediate transfer member to the surface of a recording medium; an apparatus including a charge erasing device that erases the charges on the surface of the electrophotographic photoreceptor by applying the charge erasing light after the transfer of the toner image and before the charging; and an apparatus including an electrophotographic photoreceptor heating member for increasing the temperature of an electrophotographic photoreceptor and decreasing the relative temperature are employed.

[0315] In a case of the intermediate transfer-type apparatus, for example, the transfer device has a configuration including an intermediate transfer member with a surface on which the toner image will be transferred, a primary transfer device that performs primary transfer to transfer the toner image formed on the surface of the electrophotographic photoreceptor to the surface of the intermediate transfer member, and a secondary transfer device that performs secondary transfer to transfer the toner image transferred to the surface of the intermediate transfer member to the surface of a recording medium.

[0316] The image forming apparatus according to the present exemplary embodiment may be any of a dry development type image forming apparatus or a wet development type (development type using a liquid developer) image forming apparatus.

[0317] In the image forming apparatus according to the present exemplary embodiment, for example, the portion including the electrophotographic photoreceptor may have a cartridge structure (process cartridge) that is attachable to and detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photoreceptor according to the present exemplary embodiment is preferably used. The process cartridge may include, for example, at least one selected from the group consisting of a charging device, an electrostatic latent image forming device, a developing device, and a transfer device in addition to the electrophotographic photoreceptor.

[0318] Hereinafter, an example of the image forming apparatus according to the present exemplary embodiment will be described, but the present exemplary embodiment is not limited thereto. Further, main parts shown in the figures will be described, but description of other parts will not be provided.

[0319] FIG. 2 is a schematic configuration view showing a configuration of an example of the image forming apparatus according to the present exemplary embodiment.

[0320] As shown in FIG. 2, an image forming apparatus 100 according to the present exemplary embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of the electrostatic latent image forming device), a transfer device 40 (primary transfer device), and an intermediate transfer member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position that can be exposed to the electrophotographic photoreceptor 7 from an opening portion of the process cartridge 300, the transfer device 40 is disposed at a position that faces the electrophotographic photoreceptor 7 via the intermediate transfer member 50, and the intermediate transfer member 50 is disposed such that a part of the intermediate transfer member 50 is in contact with the electrophotographic photoreceptor 7. Although not shown, the image forming apparatus also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer member 50 to a recording medium (for example, paper). The intermediate transfer member 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) correspond to an example of the transfer device.

[0321] The process cartridge 300 in FIG. 2 integrally supports the electrophotographic photoreceptor 7, a charging device 8 (an example of the charging device), a developing device 11 (an example of the developing device), and a cleaning device 13 (an example of the cleaning device) in a housing. The cleaning device 13 has a cleaning blade (an example of the cleaning member) 131, and a cleaning blade 131 is disposed to come into contact with the surface of the electrophotographic photoreceptor 7. The cleaning member may be a conductive or insulating fibrous member instead of the aspect of the cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

[0322] FIG. 2 shows an example of an image forming apparatus including a fibrous member 132 (roll shape) that supplies a lubricant 14 to the surface of the electrophotographic photoreceptor 7 and a fibrous member 133 (flat brush shape) that assists cleaning, but these are disposed as necessary.

[0323] Hereinafter, each configuration of the image forming apparatus according to the present exemplary embodiment will be described.

Charging Device

[0324] The charging device 8 may be a contact type charging device in which the charging member is in contact with the outer peripheral surface of the photoreceptor, or may be a non-contact type charging device in which the charging member is not in contact with the outer peripheral surface of the photoreceptor. An effect (the contamination of the charging member is unlikely to occur for a long period of time) obtained by the image forming apparatus according to the present exemplary embodiment is remarkable in the contact type charging device.

[0325] As the charging device 8, for example, a contact-type charging member formed of a conductive or semi-conductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, or the like is used. Further, known chargers such as a non-contact type roller charger, a scorotron charger using corona discharge, and a corotron charger are also used.

Exposure Device

[0326] Examples of the exposure device 9 include an optical system device that exposes the surface of the electrophotographic photoreceptor 7 to light such as a semiconductor laser beam, LED light, and liquid crystal shutter light in a predetermined image pattern. A wavelength of the light source is within the spectral sensitivity region of the electrophotographic photoreceptor. As a wavelength of a semiconductor laser, near infrared laser, which has an oscillation wavelength in the vicinity of 780 nm, is mostly used. However, the wavelength is not limited thereto, and a laser having an oscillation wavelength of an approximately 600 nm level or a laser having an oscillation wavelength of 400 nm or more and 450 nm or less as a blue laser may also be used. Further, a surface emission type laser light source capable of outputting a multi-beam is also effective for forming a color image.

Developing Device

[0327] Examples of the developing device 11 include a typical developing device that performs development in contact or non-contact with the developer. The developing device 11 is not particularly limited as long as the device has the above-described functions, and is selected depending on the purpose thereof. Examples thereof include known developing machines having a function of attaching a one-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, a roller, or the like. Among these, for example, a developing device formed of a developing roller having a surface on which a developer is held is preferably used.

[0328] The developer used in the developing device 11 may be a one-component developer containing only a toner or a two-component developer containing a toner and a carrier. Further, the developer may be magnetic or non-magnetic. Known developers are employed as these developers.

Cleaning Device

[0329] As the cleaning device 13, a cleaning blade type device including the cleaning blade 131 is used. In addition to the cleaning blade type device, a fur brush cleaning type device or a simultaneous development cleaning type device may be employed.

Transfer Device

[0330] Examples of the transfer device 40 include transfer chargers known per se such as a contact-type transfer charger formed of a belt, a roller, a film, and a rubber blade, a scorotron transfer charger using corona discharge, and a corotron transfer charger.

Intermediate Transfer Member

[0331] As the intermediate transfer member 50, a semi-conductive belt-like intermediate transfer member (intermediate transfer belt) containing polyimide, polyamide-imide, polycarbonate, polyarylate, polyester, rubber, or the like is used. Further, as the form of the intermediate transfer member, a drum-like intermediate transfer member may be used in addition to the belt-like intermediate transfer member.

[0332] FIG. 3 is a schematic configuration view showing a configuration of another example of the image forming apparatus according to the present exemplary embodiment.

[0333] An image forming apparatus 120 shown in FIG. 3 is a tandem type multicolor image forming apparatus in which four process cartridges 300 are mounted. The image forming apparatus 120 is configured such that four process cartridges 300 are arranged in parallel on the intermediate transfer member 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 the image forming apparatus 120 is of a tandem type.

EXAMPLES

[0334] Hereinafter, exemplary embodiments of the invention will be described in detail based on examples, but the exemplary embodiments of the invention are not limited to the examples.

[0335] In the following description, parts and % are on a mass basis unless otherwise specified.

[0336] In the following description, the synthesis, the treatment, the production, and the like are carried out at room temperature (25 C.+3 C.) unless otherwise specified.

Synthesis of Polyarylate Resin

[0337] Polyarylate resins PA1, PA2, and PA8 are synthesized.

[0338] Table 1 shows units and formulations constituting the polyarylate resins.

[0339] A2-3 and the like listed in Table 1 are specific examples of the dicarboxylic acid unit (A) described above.

[0340] B1-2 and the like listed in Table 1 are specific examples of the diol unit (B) described above.

TABLE-US-00001 TABLE 1 Polyarylate resin Dicarboxylic acid unit (A) Diol unit (B) Mw Number Number Mol % Number Mol % Number Mol % Number Mol % k PA1 A2-3 50 B1-2 50 110 PA2 A3-2 50 B4-4 50 120 PA8 A1-1 50 B4-3 50 110

Production of Photoreceptor

[0341] The following materials are prepared as materials for forming a charge transport layer. [0342] Charge transport material CTM-1 [0343] Charge transport material CTM-2

##STR00041## [0344] Polycarbonate resin PC1: the following compound, viscosity average molecular weight: 50000, numerical values in the following formulae indicate molar ratios.

##STR00042## [0345] Polycarbonate resin PC3: polymer compound having a constitutional repeating unit represented by the following formula (viscosity average molecular weight: 40,000)

##STR00043## [0346] Polyvinyl butyral resin: viscosity average molecular weight of 66,000, S-LEC BH-S, manufactured by Sekisui Chemical Co., Ltd. [0347] Phenolic compound PH3: ADEKA STAB AO-80, manufactured by ADEKA Corporation

Example 1

Formation of Undercoat Layer

[0348] 3.5 parts of a butyral resin (trade name: S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) and 41 parts of methyl ethyl ketone are mixed and dissolved. 10 parts of a curing agent (blocked isocyanate, trade name: SUMIDUR 3175, manufactured by Sumitomo Bayer Urethane Co., Ltd.), 45.5 parts of zinc oxide (trade name: SMZ-017N, manufactured by TAYCA Corporation) surface-treated with a silane coupling agent (trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.27 parts of the following compound are added and stirred, and then the mixture is dispersed for 2 hours with a sand mill using glass beads having a diameter of 1 mm. Further, 0.01 parts of dioctyl tin dilaurate and 2 parts of silicone resin particles (trade name: Tospearl 145, manufactured by GE Toshiba Silicones) are added thereto and stirred, thereby obtaining a coating solution for forming an undercoat layer. The outer peripheral surface of the conductive substrate is coated with the coating solution for forming an undercoat layer by dip coating, and dried and cured at 170 C. for 40 minutes to form an undercoat layer with a layer thickness of 20 m.

##STR00044##

Formation of Charge Generation Layer

[0349] A mixture of 14 parts of chlorogallium phthalocyanine as a charge generation material (having diffraction peaks at positions where Bragg angles (20.2) in the X-ray diffraction spectrum using CuK characteristic X-rays are at least of 7.4, 16.6, 25.5, and 28.3), 12 parts of a vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, manufactured by Nippon Unicar Company Limited) as a binder resin, and 200 parts of n-butyl acetate is dispersed in a sand mill for 4 hours using glass beads with a diameter of 1 mm. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone are added to the dispersion liquid, and the mixture is stirred to obtain a coating solution for forming a charge generation layer. The undercoat layer is dipped and coated with the coating solution for forming a charge generation layer, and dried at room temperature to form a charge generation layer having a layer thickness of 0.25 m.

Formation of Charge Transport Layer

[0350] Charge transport material CTM-1:47 parts [0351] Charge transport material CTM-2:20 parts [0352] Polyarylate resin (PA1): 29 parts (30% of total resin) [0353] Polycarbonate resin (PC1): 67 parts (70% of total resin) [0354] Phenolic compound (PH3): 4.9 parts [0355] Tetrahydrofuran: 570 parts [0356] Toluene: 57 parts

[0357] The above-described materials are stirred and mixed to obtain a coating solution for forming a charge transport layer. The charge generation layer is dipped and coated with the coating solution for forming a charge transport layer, and dried at 143 C. for 30 minutes to form a charge transport layer having a layer thickness of 33 m. In this way, a photoreceptor 1 is obtained.

Examples 2 to 10 and Comparative Examples 1 to 4

[0358] A photoreceptor is obtained in the same manner as in Example 1, except that the composition of each layer is changed as shown in Table 2.

Evaluation of Local Deterioration Suppression Properties of Electrical Properties

[0359] The photoreceptor is mounted on an electrophotographic image forming apparatus (Xerox 700 Digital Color Press, manufactured by Xerox Corporation). In addition, using a surface potential meter (manufactured by TREK INC., TREK 334), a surface potential probe is provided at a position 1 mm away from the surface of the photoreceptor, and the electrical properties of nine positions (a total of nine positions including four positions at a pitch of 20 mm upward and downward from the one center point) in the axial direction of the measurement target drum are evaluated as follows. The image forming apparatus is charged to 700 V, the post-exposure potential (VL) is set to 230 V, and then 200,000 sheets of A4-sized paper are output in a full halftone image with an image intensity of 30% in a high temperature and high humidity environment (temperature: 28 C., relative humidity: 85%). Then, the surface potential is measured with a surface potential meter (the surface potential is measured after charging-exposure amount irradiation in the same manner as the initial stage), and the results are classified as follows (the difference in VL at each point between initial state and after output of 200,000 sheets is, for example, preferably within 10 V, and it can be said that the more the number of such portions, the more stable the electrical properties).

[0360] The evaluation standards are as follows. [0361] A: 9/9 points, the difference between the initial surface potential and the long-term surface potential is within 5 V [0362] A: 9/9 points, the difference between the initial surface potential and the long-term surface potential is more than 5 V and within 10 V [0363] B+: 8/9 points, the difference between the initial surface potential and the long-term surface potential is within 10 V [0364] B: 7/9 points, the difference between the initial surface potential and the long-term surface potential is within 10 V [0365] B: 6/9 points, the difference between the initial surface potential and the long-term surface potential is within 10 V [0366] C: 5 to 3/9 points, the difference between the initial surface potential and the long-term surface potential is within 10 V [0367] D: 2 to 1/9 points, the difference between the initial surface potential and the long-term surface potential is within 10 V [0368] E: 0/9 points, the difference between the initial surface potential and the long-term surface potential is within 10 V

[0369] The evaluation results are collectively shown in Table 2.

TABLE-US-00002 TABLE 2 Charge generation layer Content of binder Evaluation resin/total of local Charge transport layer content of deterioration Polyarylate resin Polycarbonate resin Charge generation binder resin suppression Type Content Type Content material Binder resin and charge properties of of ratio of of ratio of Content Content generation electrical resin resin resin resin Type (mass %) Type of resin (mass %) material properties Example 1 PA1 0.3 PC1 0.7 Chlorogallium 54 Vinyl chloride- 46 0.46 A phthalocyanine vinyl acetate copolymer resin Example 2 PA1 1 None 0 Chlorogallium 54 Vinyl chloride- 46 0.46 A phthalocyanine vinyl acetate copolymer resin Example 3 PA2 1 None 0 Chlorogallium 59 Polyvinyl 41 0.41 B phthalocyanine butyral resin Example 4 PA2 1 None 0 Chlorogallium 35 Polyvinyl 65 0.65 B phthalocyanine butyral resin Example 5 PA8 1 None 0 Chlorogallium 59 Polyvinyl 41 0.41 B phthalocyanine butyral resin Comparative PA8 1 None 0 Chlorogallium 59 Polyvinyl 41 0.36 E Example 1 phthalocyanine butyral resin Comparative PA2 1 None 0 Hydroxygallium 59 Polyvinyl 41 0.41 D Example 2 phthalocyanine butyral resin Comparative PA2 1 None 0 Chlorogallium 61 Polyvinyl 39 0.39 C Example 3 phthalocyanine butyral resin Comparative PA2 1 None 0 Chlorogallium 29 Polyvinyl 71 0.71 C Example 4 phthalocyanine butyral resin Example 6 PA2 1 None 0 Chlorogallium 59 Phthalic acid 41 0.41 B phthalocyanine polyarylate resin Example 7 PA2 1 None 0 Chlorogallium 54 Polyvinyl 46 0.46 B+ phthalocyanine butyral resin Example 8 PA1 1 None 0 Chlorogallium 59 Polyvinyl 41 0.41 B+ phthalocyanine butyral resin Example 9 PA2 0.3 PC1 0.7 Chlorogallium 59 Polyvinyl 41 0.41 B+ phthalocyanine butyral resin Example 10 PA1 0.3 PC3 0.7 Chlorogallium 59 Polyvinyl 41 0.41 B+ phthalocyanine butvral resin

[0370] As shown in Table 2, the electrophotographic photoreceptors of Examples 1 to 10 are excellent in local deterioration suppression properties of electrical properties after long-term printing, as compared with the electrophotographic photoreceptors of Comparative Examples 1 to 4.

[0371] (((1))) An electrophotographic photoreceptor comprising: [0372] a conductive substrate; and [0373] a lamination-type photosensitive layer disposed on the conductive substrate and having a charge generation layer and a charge transport layer, [0374] wherein 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), [0375] the charge generation layer contains, as a charge generation material, a chlorogallium phthalocyanine, and [0376] a value of a content of a binder resin to a total content of the binder resin and the charge generation material in the charge generation layer is more than 0.4 and less than 0.7.

##STR00045##

[0377] In Formula (A), Ar.sup.A1 and Ar.sup.A2 are each independently an aromatic ring which may have a substituent, L.sup.A is a single bond or a divalent linking group, and n.sup.A1 is 0, 1, or 2.

[0378] In Formula (B), Ar.sup.B1 and Ar.sup.B2 are each independently an aromatic ring which may have a substituent, L.sup.B is a single bond, an oxygen atom, a sulfur atom, or C(Rb.sup.1)(Rb.sup.2), and n.sup.B1 is 0, 1, or 2. Where Rb.sup.1 and Rb.sup.2 are each independently a hydrogen atom, an alkyl group having 1 or more and 20 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an aralkyl group having 7 or more and 20 or less carbon atoms, and Rb.sup.1 and Rb.sup.2 may be bonded to each other to form a cyclic alkyl group.

[0379] (((2))) The electrophotographic photoreceptor according to (((1))), [0380] wherein the value of the content of the binder resin to the total content of the binder resin and the charge generation material in the charge generation layer is more than 0.43 and less than 0.60.

[0381] (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), [0382] wherein the dicarboxylic acid unit represented by Formula (A) includes at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by Formula (A1), a dicarboxylic acid unit (A2) represented by Formula (A2), a dicarboxylic acid unit (A3) represented by Formula (A3), a dicarboxylic acid unit (A4) represented Formula (A4), and a dicarboxylic acid unit (A5) represented by Formula (A5).

##STR00046##

[0383] In Formula (A1), n.sup.101 is an integer of 0 or greater and 4 or less, and n.sup.101 pieces of Ra.sup.101's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0384] In Formula (A2), n.sup.201 and n.sup.202 are each independently an integer of 0 or greater and 4 or less, and n.sup.201 pieces of Ra.sup.201's and n.sup.202 pieces of Ra.sup.202's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0385] In Formula (A3), n.sup.301 and n.sup.302 are each independently an integer of 0 or greater and 4 or less, and n.sup.301 pieces of Ra.sup.301's and n.sup.302 pieces of Ra.sup.302's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0386] In Formula (A4), n.sup.401 is an integer of 0 or greater and 6 or less, and n.sup.401 pieces of Ra.sup.401's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0387] In Formula (A5), n.sup.501, n.sup.502, and n.sup.503 are each independently an integer of 0 or greater and 4 or less, and n.sup.501 pieces of Ra.sup.501's, n.sup.502 pieces of Ra.sup.502's, and n.sup.503 pieces of Ra.sup.503's are each independently an alkyl group having 1 or more and 10 or less carbon atoms, an aryl group having 6 or more and 12 or less carbon atoms, or an alkoxy group having 1 or more and 6 or less carbon atoms.

[0388] (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), [0389] wherein the diol unit represented by Formula (B) includes at least one selected from the group consisting of a diol unit (B1) represented by Formula (B1), a diol unit (B2) represented by Formula (B2), a diol unit (B3) represented by Formula (B3), a diol unit (B4) represented by Formula (B4), a diol unit (B5) represented by Formula (B5), a diol unit (B6) represented by Formula (B6), a diol unit (B7) represented by Formula (B7), and a diol unit (B8) represented by Formula (B8).

##STR00047## ##STR00048##

[0390] In Formula (B1), Rb.sup.101 is a branched alkyl group having 4 or more and 20 or less carbon atoms, Rb.sup.201 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.401, Rb.sup.501, Rb.sup.801, and Rb.sup.901 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0391] In Formula (B2), Rb.sup.102 is a linear alkyl group having 4 or more and 20 or less carbon atoms, Rb.sup.202 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.402, Rb.sup.502, Rb.sup.802, and Rb.sup.902 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0392] In Formula (B3), Rb.sup.113 and Rb.sup.213 are each independently a hydrogen atom, a linear alkyl group having 1 or more and 3 or less carbon atoms, an alkoxy group having 1 or more and 4 or less carbon atoms, or a halogen atom, d is an integer of 7 or greater and 15 or less, and Rb.sup.403, Rb.sup.503, Rb.sup.803, and Rb.sup.903 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0393] In Formula (B4), Rb.sup.104 and Rb.sup.204 are each independently a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.404, Rb.sup.504, Rb.sup.804, and Rb.sup.904 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0394] In Formula (B5), Ar.sup.105 is an aryl group having 6 or more and 12 or less carbon atoms or an aralkyl group having 7 or more and 20 or less carbon atoms, Rb.sup.205 is a hydrogen atom or an alkyl group having 1 or more and 3 or less carbon atoms, and Rb.sup.405, Rb.sup.505, Rb.sup.805, and Rb.sup.905 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0395] In Formula (B6), Rb.sup.116 and Rb.sup.216 are each independently a hydrogen atom, a linear alkyl group having 1 or more and 3 or less carbon atoms, an alkoxy group having 1 or more and 4 or less carbon atoms, or a halogen atom, e is an integer of 4 or greater and 6 or less, and Rb.sup.406, Rb.sup.506, Rb.sup.806, and Rb.sup.906 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0396] In Formula (B7), Rb.sup.407, Rb.sup.507, Rb.sup.807, and Rb.sup.907 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0397] In Formula (B8), Rb.sup.408, Rb.sup.508, Rb.sup.808, and Rb.sup.908 are each independently a hydrogen atom, an alkyl group having 1 or more and 4 or less carbon atoms, an alkoxy group having 1 or more and 6 or less carbon atoms, or a halogen atom.

[0398] (((5))) The electrophotographic photoreceptor according to any one of (((1))) to (((4))), [0399] wherein the binder resin in the charge generation layer is a vinyl acetate-based resin or a polyvinyl butyral-based resin.

[0400] (((6))) The electrophotographic photoreceptor according to any one of (((1))) to (((5))), [0401] wherein the binder resin in the charge generation layer is a vinyl chloride-vinyl acetate copolymer or a polyvinyl butyral resin.

[0402] (((7))) The electrophotographic photoreceptor according to any one of (((1))) to (((6))), [0403] wherein the charge transport layer further contains a polycarbonate resin.

[0404] (((8))) A process cartridge comprising: [0405] the electrophotographic photoreceptor according to any one of (((1))) to (((7))), [0406] wherein the process cartridge is attachable to and detachable from an image forming apparatus.

[0407] (((9))) An image forming apparatus comprising: [0408] the electrophotographic photoreceptor according to any one of (((1))) to (((7))); [0409] a charging device that charges a surface of the electrophotographic photoreceptor; [0410] an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; [0411] a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and [0412] a transfer device that transfers the toner image to a surface of a recording medium.

[0413] The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.