Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that is excellent in electrical characteristics and wear resistance.SOLUTION: An electrophotographic photoreceptor comprises a photosensitive layer that is arranged on a conductive substrate and has a charge generating layer and a charge transport layer. The charge transport layer contains a charge transport material, and a polyarylate resin having a dicarboxylic acid unit represented by the formula (A) and a diol unit represented by the formula (B). The mass ratio of the charge transport material contained in the charge transport layer is 56 mass% or more and 70 mass% or less.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are laminated in this order on a conductive support, and the charge transport layer contains a charge transport material represented by a predetermined chemical formula, a polycarbonate resin, and a biphenyl derivative represented by a predetermined chemical formula.

[0003] Patent Document 2 discloses an electrophotographic photoreceptor including a conductive substrate and a photosensitive layer, the photosensitive layer containing a charge generating agent, a charge transporting agent, and a polyarylate resin having a repeating unit represented by a predetermined chemical formula.

[0004] Patent Document 3 discloses an electrophotographic photoreceptor including a conductive substrate and a laminated photosensitive layer having a charge generation layer and a charge transport layer disposed on the conductive substrate, the charge transport layer containing a polyarylate resin and a charge transport material, and the value of the ratio M1 / M2 of the mass M1 of the charge transport material contained in the charge transport layer to the mass M2 of the charge transport layer being 0.28 or more and 0.55 or less.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present disclosure aims to provide an electrophotographic photoreceptor that is superior in electrical characteristics and abrasion resistance compared to an electrophotographic photoreceptor in which the mass ratio of the charge transport material in the charge transport layer is less than 56% by mass or more than 70% by mass.

Means for Solving the Problems

[0007] Specific means for solving the above problems include the following aspects. Each formula representing a compound is the same as the formula with the same number described later.

[0008] <1> An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer having a charge generation layer and a charge transport layer disposed on the conductive substrate, wherein the charge transport layer contains a charge transport material and a polyarylate resin having a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), and the mass ratio of the charge transport material in the charge transport layer is 56% by mass or more and 70% by mass or less. Electrophotographic photoreceptor. <2> The electrophotographic photoreceptor according to <1>, wherein the mass ratio of the charge transport material in the charge transport layer is 60% by mass or more and 65% by mass or less. <3> The electrophotographic photoreceptor according to <1> or <2>, wherein the charge transport material contains at least one selected from the group consisting of a compound represented by formula (1), a compound represented by formula (2), a compound represented by formula (3), and a compound represented by formula (4). <4> The electrophotographic photoreceptor according to any one of <1> to <3>, wherein the diameter of the electrophotographic photoreceptor is 25 mm or less. <5> A process cartridge that is detachable from an image forming apparatus and includes the electrophotographic photoreceptor according to any one of <1> to <4>. Process cartridge detachable from an image forming apparatus. <6> The electrophotographic photoreceptor according to any one of <1> to <4>, and A charging device that charges the surface of the electrophotographic photoreceptor. An electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, A developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, A transfer device that transfers the toner image onto the surface of a recording medium, An image forming apparatus comprising the same.

Advantages of the Invention

[0009] <1>, <3> or <4> provides an electrophotographic photoreceptor having excellent electrical characteristics and abrasion resistance as compared with an electrophotographic photoreceptor in which the mass ratio of the charge transport material in the charge transport layer is less than 56% by mass or more than 70% by mass. <2> provides an electrophotographic photoreceptor having excellent electrical characteristics and abrasion resistance as compared with an electrophotographic photoreceptor in which the mass ratio of the charge transport material in the charge transport layer is less than 60% by mass or more than 65% by mass. <5> provides a process cartridge including an electrophotographic photoreceptor having excellent electrical characteristics and abrasion resistance as compared with an electrophotographic photoreceptor in which the mass ratio of the charge transport material in the charge transport layer is less than 56% by mass or more than 70% by mass. <6> provides an image forming apparatus including an electrophotographic photoreceptor having excellent electrical characteristics and abrasion resistance as compared with an electrophotographic photoreceptor in which the mass ratio of the charge transport material in the charge transport layer is less than 56% by mass or more than 70% by mass.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0011] Embodiments of the present disclosure will be described below. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the embodiments.

[0012] In the present disclosure, "A and / or B" is synonymous with "at least one of A and B". That is, "A and / or B" means that it may be only A, only B, or a combination of A and B.

[0013] The numerical range indicated by "~" in the present disclosure indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

[0014] In the present disclosure, the term "step" includes not only an independent step but also cases where it cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0015] When an embodiment in the present disclosure is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Also, the sizes of the members in each drawing are conceptual, and the relative relationships of the sizes between the members are not limited thereto.

[0016] In the present disclosure, each component may contain a plurality of corresponding substances. When referring to the amount of each component in the composition, in the case where there are a plurality of substances corresponding to each component in the composition, unless otherwise specified, it means the total amount of the plurality of substances present in the composition. In the present disclosure, the particles corresponding to each component may include a plurality of types. When there are a plurality of types of particles corresponding to each component in the composition, the particle diameter of each component means a value for the mixture of the plurality of types of particles present in the composition, unless otherwise specified.

[0017] In the present disclosure, when a compound is represented by a structural formula, it may be represented by a structural formula in which the symbols (C and H) representing carbon atoms and hydrogen atoms in the hydrocarbon group and / or hydrocarbon chain are omitted. In the present disclosure, unless otherwise specified, the alkyl group and alkylene group include any of linear, branched, and cyclic forms. In the present disclosure, organic groups, aromatic rings, linking groups, alkyl groups, alkylene groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, etc. may have hydrogen atoms in the group substituted by halogen atoms. In the present disclosure, “(meth)acryl” is an expression including both acrylic and methacrylic, and “(meth)acrylate” is an expression including both acrylate and methacrylate. In the present disclosure, the “structural unit” of a copolymer or resin is synonymous with the monomer unit.

[0018] In the present disclosure, the “axial direction” of the electrophotographic photoreceptor means the direction in which the rotation axis of the electrophotographic photoreceptor extends, and the “circumferential direction” of the electrophotographic photoreceptor means the rotation direction of the electrophotographic photoreceptor.

[0019] <Electrophotographic photoreceptor> The electrophotographic photoreceptor according to the present embodiment (hereinafter also referred to as “photoreceptor”) includes a conductive substrate and a photosensitive layer disposed on the conductive substrate. The photosensitive layer of the photoreceptor according to the present embodiment is a laminated photosensitive layer (so-called function-separated photosensitive layer) having a charge generation layer and a charge transport layer. The photoreceptor according to the present embodiment may further include a layer other than the photosensitive layer (for example, an undercoat layer, an intermediate layer).

[0020] FIG. 1 is a partial cross-sectional view schematically showing an example of the layer structure of the photoreceptor according to the present embodiment. The photoreceptor 10A shown in FIG. 1 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. The photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3.

[0021] In the photoreceptor according to the present embodiment, the charge transport layer contains a charge transport material and a polyarylate resin having a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), and the mass ratio of the charge transport material in the charge transport layer is 56% by mass or more and 70% by mass or less.

[0022]

Chemical formula

[0023] In formula (A), n 1 is 1, 2, or 3, and n 1 number of m 1 are each independently 0, 1, 2, 3, or 4, and m 1 number of Ra 1 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (B), Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7 , Rb 8 , Rb 9 and Rb 10 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, and Rb 1 and Rb2 It may be combined to form a cyclic alkyl group.

[0024] In the present disclosure, the dicarboxylic acid unit represented by the formula (A) is referred to as "dicarboxylic acid unit (A)", the diol unit represented by the formula (B) is referred to as "diol unit (B)", and a polyarylate resin having the dicarboxylic acid unit represented by the formula (A) and the diol unit represented by the formula (B) is referred to as "polyarylate resin (1)".

[0025] In the photoreceptor according to the present embodiment, since the mass ratio of the charge transport material in the charge transport layer is 56% by mass or more, the electrical characteristics are excellent, that is, the residual potential of the photoreceptor is less likely to increase. According to the photoreceptor according to the present embodiment, an image can be formed at a relatively high process speed. In the photoreceptor according to the present embodiment, the mass ratio of the charge transport material in the charge transport layer is 70% by mass or less, and the charge transport layer contains the polyarylate resin (1), so that the abrasion resistance is excellent. In the polyarylate resin (1), resin molecules are bonded by intermolecular forces due to the stacking of aromatic rings, improving the abrasion resistance of the charge transport layer.

[0026] In the photoreceptor according to the present embodiment, the mass ratio of the charge transport material in the charge transport layer is 56% by mass or more and 70% by mass or less from the viewpoint of the balance between electrical characteristics and abrasion resistance, preferably 58% by mass or more and 68% by mass or less, and more preferably 60% by mass or more and 65% by mass or less.

[0027] The method for measuring the mass of the charge transport material contained in the charge transport layer and the mass of the charge transport layer is as follows. Immerse the photoreceptor in various solvents (which may be a mixed solvent). Identify the solvent in which the charge transport layer dissolves. Immerse the photoreceptor in the solvent in which the charge transport layer dissolves to extract the charge transport layer. Concentrate the solution from which the charge transport layer has been extracted, perform vacuum drying, and then weigh it to obtain the mass of the charge transport layer. Separately, the solution from which the charge transport layer has been extracted is dropped into a poor solvent for the polyarylate resin (1) (for example, a nonpolar solvent such as hexane or toluene, a lower alcohol such as methanol or isopropanol. The poor solvent may be a mixed solvent.) to reprecipitate the resin. The remaining solution after the reprecipitation treatment is concentrated, and each material is isolated by preparative thin-layer chromatography and the yield is quantified. The charge transport material is identified from each isolated material by NMR (nuclear magnetic resonance) measurement, and the yields of the charge transport materials are totaled.

[0028] In the photoreceptor according to this embodiment, the mass ratio of the polyarylate resin (1) in the charge transport layer is preferably 30% by mass or more and 44% by mass or less, more preferably 32% by mass or more and 42% by mass or less, and still more preferably 35% by mass or more and 40% by mass or less, from the viewpoint of the balance between electrical properties and abrasion resistance.

[0029] In the photoreceptor according to this embodiment, since the mass ratio of the charge transport material in the charge transport layer is 56% by mass or more, the residual potential of the photoreceptor hardly increases even when it rotates relatively fast. Therefore, according to the photoreceptor of this embodiment, the diameter of the photoreceptor can be made relatively small. The diameter of the photoreceptor according to this embodiment may be 30 mm or less, and may be 25 mm or less. The diameter of the photoreceptor according to this embodiment is, for example, 20 mm or more. The photoreceptor according to this embodiment may be cylindrical or columnar.

[0030] Hereinafter, the polyarylate resin (1) and each layer of the photoreceptor will be described in detail.

[0031] [Polyarylate Resin (1)] The polyarylate resin (1) has at least a dicarboxylic acid unit (A) and a diol unit (B). The polyarylate resin (1) may contain other dicarboxylic acid units other than the dicarboxylic acid unit (A). The polyarylate resin (1) may contain other diol units other than the diol unit (B).

[0032] The dicarboxylic acid unit (A) is a structural unit represented by the following formula (A).

[0033] [Chemical formula]

[0034] In formula (A), n 1 is 1, 2 or 3, and n 1 number of m 1 are each independently 0, 1, 2, 3 or 4, and m 1 number of Ra 1 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms or an alkoxy group having 1 to 6 carbon atoms.

[0035] In formula (A), n 1 is 1, 2 or 3, and 2 is preferred. n 1 When n is 2, the two benzene rings in formula (A) may be the same benzene ring or different benzene rings with respect to m 1 and Ra 1 . n 1 When n is 3, the three benzene rings in formula (A) may be the same benzene ring or different benzene rings with respect to m 1 and Ra 1 .

[0036] In formula (A), when n 1 is 2 or 3, the linking position between the benzene rings may be ortho, meta or para, and meta or para is preferred.

[0037] In formula (A), m 1 is 0, 1, 2, 3 or 4, 0, 1 or 2 is preferred, 0 or 1 is more preferred, and 0 is even more preferred. m 1 When m is 2, the two Ra 1 bonded to the same benzene ring may be the same type of group or different types of groups. m 1When m is 3, the three Ra groups bonded to the same benzene ring 1 may be of the same type or different types of groups. m 1 When m is 4, the four Ra groups bonded to the same benzene ring 1 may be of the same type or different types of groups.

[0038] In formula (A), the alkyl group having 1 to 10 carbon atoms may be linear, branched or cyclic. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 or 2. In formula (A), the aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6 to 9. In formula (A), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched or cyclic. The number of carbon atoms of the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 or 2.

[0039] In formula (A), examples of the linear alkyl group having 1 to 10 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, and n-decyl group. Examples of the branched alkyl group having 3 to 10 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, etc. Examples of the cyclic alkyl group having 3 to 10 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and an alkyl group of a polycycle (for example, bicyclic, tricyclic, spiro ring) formed by linking these monocyclic alkyl groups.

[0040] In formula (A), examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a biphenyl group, a 1-naphthyl group, a 2-naphthyl group, and the like.

[0041] In formula (A), examples of the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. In formula (A), examples of the branched alkoxy group having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, a tert-hexyloxy group, and the like. In formula (A), examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, a cyclohexyloxy group, and the like.

[0042] In formula (A), m 1 When it is 1, 2, 3, or 4, Ra 1 is preferably a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 3 to 6 carbon atoms, more preferably a linear alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 or 4 carbon atoms, and still more preferably a methyl group or an ethyl group.

[0043] Specific examples of the dicarboxylic acid unit (A) are shown below as the dicarboxylic acid units (A-1) to (A-13). The dicarboxylic acid unit (A) is not limited thereto.

[0044] [Chemistry]

[0045] [Chemistry]

[0046] As the dicarboxylic acid unit (A), (A-1), (A-7) and (A-12) of the above specific examples are preferable, and (A-12) is most preferable.

[0047] The dicarboxylic acid unit (A) contained in the polyarylate resin (1) may be one kind or two or more kinds.

[0048] The diol unit (B) is a structural unit represented by the following formula (B).

[0049] [Chemistry]

[0050] In formula (B), Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7 , Rb 8 , Rb 9 and Rb 10 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and Rb 1 and Rb 2 may be bonded to form a cyclic alkyl group.

[0051] In formula (B), Rb 1 and Rb 2The alkyl group having 1 to 20 carbon atoms according to [it] may be linear, branched or cyclic. The number of carbon atoms of the alkyl group is preferably 1 to 15, more preferably 1 to 12, and still more preferably 1 to 10. In formula (B), Rb 1 and Rb 2 The aryl group having 6 to 12 carbon atoms according to [it] may be monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6 to 9. In formula (B), Rb 1 and Rb 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms according to [it] may be monocyclic or polycyclic, and the alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched or cyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6 to 9. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 5, and still more preferably 1 to 4. In formula (B), Rb 1 and Rb 2 The number of carbon atoms of the cyclic alkyl group that may be formed by bonding [them] is preferably 5 to 15, and more preferably 6 to 12.

[0052] In formula (B), Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7 , Rb 8 , Rb 9 and Rb 10 The alkyl group having 1 to 10 carbon atoms according to [it] may be linear, branched or cyclic. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 or 2. In formula (B), Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7 , Rb 8 , Rb 9 and Rb 10The aryl group having 6 to 12 carbon atoms according to may be either monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, more preferably 6 to 9. In formula (B), Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7 , Rb 8 , Rb 9 and Rb 10 The aryl group in the aralkyl group having 7 to 20 carbon atoms according to may be either monocyclic or polycyclic, and the alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched or cyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, more preferably 6 to 9. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 5, still more preferably 1 to 4. In formula (B), Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7 , Rb 8 , Rb 9 and Rb 10 The alkyl group in the alkoxy group having 1 to 6 carbon atoms according to may be linear, branched or cyclic. The number of carbon atoms of the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, still more preferably 1 or 2.

[0053] In formula (B), examples of the linear alkyl group having 1 to 20 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, tridecyl group, n-tetradecyl group, n-pentadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-icosyl group and the like. Examples of the branched alkyl group having 3 to 20 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, isododecyl group, sec-dodecyl group, tert-dodecyl group, tert-tetradecyl group, tert-pentadecyl group and the like. Examples of the cyclic alkyl group having 3 to 20 carbon atoms include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, cyclodecyl group and the like, and alkyl groups of polycycles (for example, bicyclic, tricyclic, spiro ring) formed by linking these monocyclic alkyl groups.

[0054] In formula (B), examples of the aryl group having 6 to 12 carbon atoms include phenyl group, biphenyl group, 1-naphthyl group, 2-naphthyl group and the like.

[0055] In formula (B), examples of the aralkyl group having 7 to 20 carbon atoms include benzyl group, phenylethyl group, phenylpropyl group, 4-phenylbutyl group, phenylpentyl group, phenylhexyl group, phenylheptyl group, phenyloctyl group, phenylnonyl group, naphthylmethyl group, naphthylethyl group, anthrathylmethyl group, phenyl-cyclopentylmethyl group and the like.

[0056] In formula (B), examples of the linear alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, n-propoxy group, n-butoxy group, n-pentyloxy group, n-hexyloxy group. In formula (B), examples of the branched alkoxy group having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, a tert-hexyloxy group, and the like. In formula (B), examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, a cyclohexyloxy group, and the like.

[0057] In formula (B), Rb 1 and Rb 2 are each independently a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms, or it is preferable that Rb 1 and Rb 2 are bonded to each other to form a cyclic alkyl group having 5 to 12 carbon atoms. In formula (B), Rb 1 and Rb 2 are each independently a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 1 to 10 carbon atoms, or it is more preferable that Rb 1 and Rb 2 are bonded to each other to form a cyclic alkyl group having 5 to 12 carbon atoms. In formula (B), Rb 1 and Rb 2 are each independently more preferably a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms or a branched alkyl group having 1 to 10 carbon atoms.

[0058] In formula (B), at least one of Rb 1 and Rb 2 is a linear alkyl group having 4 to 10 carbon atoms, a branched alkyl group having 4 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms, or Rb 1 and Rb 2It is preferably bonded to form a cyclic alkyl group having 5 to 12 carbon atoms. In formula (B), Rb 1 and Rb 2 It is more preferable that at least one of them is a linear alkyl group having 4 to 10 carbon atoms or a branched alkyl group having 4 to 10 carbon atoms. Rb 1 and Rb 2 When at least one of them is the above, Rb 1 and Rb 2 The other of them is preferably a hydrogen atom or a linear alkyl group having 1 to 3 carbon atoms.

[0059] The diol unit (B) is preferably a structural unit represented by the following formula (B’).

[0060]

Chemical formula

[0061] Rb in formula (B’) 1 , Rb 2 , Rb 4 and Rb 9 are respectively synonymous with Rb in formula (B) 1 , Rb 2 , Rb 4 and Rb 9 and the preferred forms are also the same.

[0062] As the diol unit (B), in formula (B’), Rb 1 is a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms or a branched alkyl group having 3 carbon atoms, Rb 2 is a linear alkyl group having 4 to 10 carbon atoms, a branched alkyl group having 4 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms or an aralkyl group having 7 to 10 carbon atoms, and Rb 4 and Rb 9 are each independently a hydrogen atom or a methyl group, which is a preferred form; Rb 1is a hydrogen atom or a methyl group, and Rb 2 is a linear alkyl group having 4 to 10 carbon atoms or a branched alkyl group having 4 to 10 carbon atoms, and Rb 4 and Rb 9 are each independently a hydrogen atom or a methyl group is more preferable.

[0063] Specific examples of the diol unit (B) are shown below as diol units (B-1) to (B-38). The diol unit (B) is not necessarily limited thereto.

[0064]

Chemical formula

[0065]

Chemical formula

[0066]

Chemical formula

[0067]

Chemical formula

[0068]

Chemical formula

[0069] The diol unit (B) contained in the polyarylate resin (1) may be one kind or two or more kinds.

[0070] The mass ratio of the dicarboxylic acid unit (A) in the polyarylate resin (1) is preferably 15% by mass or more and 60% by mass or less. When the mass ratio of the dicarboxylic acid unit (A) is 15% by mass or more, the abrasion resistance of the photosensitive layer is good. From this viewpoint, the mass ratio of the dicarboxylic acid unit (A) is more preferably 20% by mass or more, and still more preferably 25% by mass or more. When the mass ratio of the dicarboxylic acid unit (A) is 60% by mass or less, peeling of the photosensitive layer can be more suppressed. From this viewpoint, the mass ratio of the dicarboxylic acid unit (A) is more preferably 55% by mass or less, and still more preferably 50% by mass or less.

[0071] The mass ratio of the diol unit (B) in the polyarylate resin (1) is preferably 25% by mass or more and 60% by mass or less. When the mass ratio of the diol unit (B) is 25% by mass or more, peeling of the photosensitive layer can be more suppressed. From this viewpoint, the mass ratio of the diol unit (B) is more preferably 30% by mass or more, and still more preferably 35% by mass or more. When the mass ratio of the diol unit (B) is 60% by mass or less, the solubility in the coating liquid for forming the photosensitive layer can be maintained and the abrasion resistance can be improved. From this viewpoint, the mass ratio of the diol unit (B) is more preferably 55% by mass or less, and still more preferably 50% by mass or less.

[0072] The polyarylate resin (1) may contain other dicarboxylic acid units other than the dicarboxylic acid unit (A).

[0073] Examples of the other dicarboxylic acid units include a dicarboxylic acid unit (C) represented by the following formula (C).

[0074]

Chemical formula

[0075] In formula (C), Rc 1 , Rc 2 , Rc 3 , Rc 4 , Rc 5 and Rc 6Each is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0076] In formula (C), the alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 or 2. In formula (C), the aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6 to 9. In formula (C), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 or 2.

[0077] Examples of each form of the alkyl group, aryl group, and alkoxy group in formula (C) include the same groups as those listed for formula (A).

[0078] In formula (C), Rc 1 , Rc 2 , Rc 3 , Rc 4 , Rc 5 and Rc 6 are each independently preferably a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, or a branched alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a branched alkyl group having 1 to 4 carbon atoms, still more preferably a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, or a branched alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom.

[0079] As the dicarboxylic acid unit (C), a 2,6-naphthalenedicarboxylic acid unit (the following formula) is most preferred.

[0080] [Chemical formula]

[0081] The dicarboxylic acid unit (C) contained in the polyarylate resin (1) may be one kind or two or more kinds.

[0082] When the polyarylate resin (1) has a dicarboxylic acid unit (C), the mass ratio of the dicarboxylic acid unit (C) in the polyarylate resin (1) is preferably 1% by mass or more and 20% by mass or less.

[0083] Examples of other dicarboxylic acid units include a dicarboxylic acid unit (D) represented by the following formula (D).

[0084] [Chemical formula]

[0085] In formula (D), Rd 1 , Rd 2 , Rd 3 , Rd 4 , Rd 5 , Rd 6 , Rd 7 and Rd 8 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0086] In formula (D), the alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 or 2. In formula (D), the aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6 to 9. In formula (D), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched or cyclic. The number of carbon atoms of the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 or 2.

[0087] Examples of the respective forms of the alkyl group, aryl group and alkoxy group in formula (D) include the same groups as those listed for formula (A).

[0088] In formula (D), Rd 1 , Rd 2 , Rd 3 , Rd 4 , Rd 5 , Rd 6 , Rd 7 and Rd 8 are each independently preferably a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 1 to 4 carbon atoms, still more preferably a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms or a branched alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom.

[0089] The dicarboxylic acid unit (D) is preferably a structural unit represented by the following formula (D’).

[0090]

Chemical formula

[0091] Rd in formula (D’) 1 , Rd 2 , Rd 3 and Rd 4 are each synonymous with Rd in formula (D) 1 , Rd 2 , Rd 3 and Rd 4 and have the same preferred forms.

[0092] As the dicarboxylic acid unit (D), a diphenyl ether-4,4'-dicarboxylic acid unit (the following formula) is most preferable.

[0093]

Chemical formula

[0094] The dicarboxylic acid unit (D) contained in the polyarylate resin (1) may be one kind or two or more kinds.

[0095] When the polyarylate resin (1) has a dicarboxylic acid unit (D), the mass ratio of the dicarboxylic acid unit (D) in the polyarylate resin (1) is preferably 1% by mass or more and 20% by mass or less.

[0096] Examples of other dicarboxylic acid units include aliphatic dicarboxylic acid (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenyl succinic acid, adipic acid, sebacic acid) units, alicyclic dicarboxylic acid (e.g., cyclohexanedicarboxylic acid) units, and lower (e.g., having 1 to 5 carbon atoms) alkyl ester units thereof. These dicarboxylic acid units contained in the polyarylate resin (1) may be one kind or two or more kinds.

[0097] The polyarylate resin (1) may contain other diol units other than the diol unit (B).

[0098] Examples of other diol units include, for example, a diol unit (E) represented by the following formula (E).

[0099]

Chemical formula

[0100] In formula (E), Re 1 , Re 2 , Re 3 , Re 4, Re 5 , Re 6 , Re 7 and Re 8 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0101] In formula (E), the alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 or 2. In formula (E), the aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6 to 9. In formula (E), the aryl group in the aralkyl group having 7 to 20 carbon atoms may be monocyclic or polycyclic, and the alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6 to 9. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 5, and still more preferably 1 to 4. In formula (E), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 or 2.

[0102] Examples of the respective forms of the alkyl group, aryl group, aralkyl group, and alkoxy group in formula (E) include the same groups as those listed for formula (B).

[0103] In formula (E), Re 1 , Re 2 , Re 3 , Re 4 , Re 5 , Re 6 , Re 7 and Re 8Each is independently preferably a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, or a branched alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a branched alkyl group having 1 to 4 carbon atoms, still more preferably a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, or a branched alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom or a methyl group.

[0104] The diol unit (E) is preferably a structural unit represented by the following formula (E’).

[0105]

Chemical formula

[0106] Re in formula (E’) 1 , Re 2 , Re 3 and Re 4 are respectively synonymous with Re 1 , Re 2 , Re 3 and Re 4 in formula (E), and the preferred forms are also the same.

[0107] As the diol unit (E), any of the following is most preferred.

[0108]

Chemical formula

[0109] The polyarylate resin (1) may contain one or more kinds of the diol unit (E).

[0110] When the polyarylate resin (1) has the diol unit (E), the mass ratio of the diol unit (E) in the polyarylate resin (1) is preferably 1% by mass or more and 20% by mass or less.

[0111] Examples of other diol units include, for example, the diol unit (F) represented by the following formula (F).

[0112]

Chemical formula

[0113] In formula (F), Rf 1 , Rf 2 , Rf 3 , Rf 4 , Rf 5 , Rf 6 , Rf 7 and Rf 8 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0114] In formula (F), the alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 or 2. In formula (F), the aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6 to 9. In formula (F), the aryl group in the aralkyl group having 7 to 20 carbon atoms may be monocyclic or polycyclic, and the alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6 to 9. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 5, and still more preferably 1 to 4. In formula (F), the alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 or 2.

[0115] Examples of the forms of the alkyl group, aryl group, aralkyl group, and alkoxy group in formula (F) include the same groups as those listed for formula (B).

[0116] In formula (F), Rf 1 , Rf 2 , Rf 3 , Rf 4 , Rf 5 , Rf 6 , Rf 7 and Rf 8 are each independently preferably a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, or a branched alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a branched alkyl group having 1 to 4 carbon atoms, still more preferably a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, or a branched alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom or a methyl group.

[0117] The diol unit (F) is preferably a structural unit represented by the following formula (F’).

[0118]

Chemical formula

[0119] Rf 1 , Rf 2 , Rf 3 and Rf 4 are each synonymous with Rf 1 , Rf 2 , Rf 3 and Rf 4 in formula (F), and the preferred forms are also the same.

[0120] As the diol unit (F), the bis(4-hydroxyphenyl)ether unit (the following formula) is most preferred.

[0121]

Chemical formula

[0122] The diol unit (F) contained in the polyarylate resin (1) may be one kind or two or more kinds.

[0123] When the polyarylate resin (1) has a diol unit (F), the mass ratio of the diol unit (F) in the polyarylate resin (1) is preferably 1% by mass or more and 20% by mass or less.

[0124] Examples of other diol units include aliphatic diol (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) units and alicyclic diol (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A) units. These diol units contained in the polyarylate resin (1) may be one kind or two or more kinds.

[0125] The polyarylate resin (1) can be obtained by polycondensing a monomer that provides a dicarboxylic acid unit (A) and a monomer that provides a diol unit (B) with other monomers as necessary by a conventional method. Examples of the method for polycondensing monomers include the interfacial polymerization method, the solution polymerization method, and the melt polymerization method. The interfacial polymerization method is a polymerization method in which a polyester is obtained by mixing a dicarboxylic acid halide dissolved in an organic solvent immiscible with water and a dihydric alcohol dissolved in an aqueous alkali solution. Examples of the literature on the interfacial polymerization method include W.M. EARECKSON, J. Poly. Sci., XL 399, 1959, and Japanese Patent Publication No. 40-1959. Since the reaction is faster in the interfacial polymerization method than in the solution polymerization method, hydrolysis of the dicarboxylic acid halide can be suppressed, and as a result, a high molecular weight polyester resin can be obtained.

[0126] The terminals of the polyarylate resin (1) may be sealed or modified with a terminal blocking agent or a molecular weight regulator used during production. Examples of the terminal blocking agent or the molecular weight regulator include monohydric phenols, monohydric acid chlorides, monohydric alcohols, and monohydric carboxylic acids. 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, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m-phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, 2-phenyl-2-(3-hydroxyphenyl)propane. Examples of the monohydric acid chloride include benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetyl chloride, butyryl chloride, octanoyl chloride, benzoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and monofunctional acid halides such as their substituents. 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. Examples of the monocarboxylic acid include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0127] From the viewpoint of the abrasion resistance of the charge transport layer, the weight average molecular weight of the polyarylate resin (1) is preferably 50,000 or more, more preferably 60,000 or more, and still more preferably 70,000 or more. From the viewpoints of the coatability of the charge transport layer and the adhesion to the charge generation layer, the weight average molecular weight of the polyarylate resin (1) is preferably 400,000 or less, preferably 300,000 or less, and more preferably 250,000 or less.

[0128] The method for measuring the weight average molecular weight of the polyarylate resin (1) contained in the charge transport layer is as follows. The photoreceptor is immersed in various solvents (which may be a mixed solvent) to identify the solvent in which the charge transport layer dissolves. The photoreceptor is immersed in the solvent in which the charge transport layer dissolves to extract the charge transport layer. The solution obtained by extracting the charge transport layer is dropped into a poor solvent for the polyarylate resin (1) (for example, nonpolar solvents such as hexane and toluene, and lower alcohols such as methanol and isopropanol. The poor solvent may be a mixed solvent) to reprecipitate the resin. The reprecipitation treatment is repeated twice if necessary, and the reprecipitate is dried under vacuum to obtain the polyarylate resin (1). The molecular weight of the polyarylate resin (1) is measured by GPC (gel permeation chromatography) to specify the weight average molecular weight. Tetrahydrofuran is used as the eluent for GPC, and polystyrene is used as the standard sample.

[0129] [Conductive substrate] Examples of the conductive substrate include a metal plate, a metal drum, and a metal belt, etc. that contain a metal (such as aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or an alloy (such as stainless steel, etc.). Also, examples of the conductive substrate include paper, a resin film, a belt, etc. coated, vapor-deposited, or laminated with a conductive compound (such as a conductive polymer, indium oxide, etc.), a metal (such as aluminum, palladium, gold, etc.), or an alloy. Here, "conductive" means that the volume resistivity is less than 1×10 13 Ω cm.

[0130] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center line average roughness Ra of 0.04 μm or more and 0.5 μm or less for the purpose of suppressing interference fringes generated when irradiating laser light. When non-interference light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is more suitable for longer life in order to suppress the occurrence of defects due to unevenness on the surface of the conductive substrate.

[0131] Examples of the roughening method include wet honing performed by suspending an abrasive in water and spraying it onto the conductive substrate, centerless grinding in which the conductive substrate is pressed against a rotating grindstone and continuously ground, anodic oxidation treatment, etc.

[0132] Examples of the roughening method also include a method in which, without roughening the surface of the conductive substrate, a conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the layer is roughened by the particles dispersed therein.

[0133] The roughening treatment by anodic oxidation forms an oxide film on the surface of a conductive substrate made of metal (for example, made of aluminum) as an anode in an electrolyte solution by anodic oxidation. Examples of the electrolyte solution include a sulfuric acid solution and an oxalic acid solution. However, the porous anodic oxide film formed by anodic oxidation is chemically active in its original state, is easily contaminated, and has a large resistance variation due to the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film by blocking the micropores of the oxide film with volume expansion by a hydration reaction in pressurized steam or boiling water (a metal salt such as nickel may be added) to change it into a more stable hydrated oxide.

[0134] The film thickness of the anodic oxide film is preferably, for example, 0.3 μm or more and 15 μm or less. When the film thickness is within the above range, there is a tendency for the barrier property against injection to be exhibited, and there is also a tendency for the increase in the residual potential due to repeated use to be suppressed.

[0135] The conductive substrate may be treated with an acidic treatment solution or boehmite treatment. The treatment with the acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The mixing ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution are, for example, in the range of 10% by mass or more and 11% by mass or less for phosphoric acid, 3% by mass or more and 5% by mass or less for chromic acid, and 0.5% by mass or more and 2% by mass or less for hydrofluoric acid, and the concentration of these acids as a whole is preferably in the range of 13.5% by mass or more and 18% by mass or less. The treatment temperature is preferably, for example, 42°C or more and 48°C or less. The film thickness of the film is preferably 0.3 μm or more and 15 μm or less.

[0136] The boehmite treatment is carried out, for example, by immersing in pure water at 90°C or more and 100°C or less for 5 to 60 minutes, or by bringing into contact with heated steam at 90°C or more and 120°C or less for 5 to 60 minutes. The film thickness of the film is preferably 0.1 μm or more and 5 μm or less. This may be further subjected to anodic oxidation treatment using an electrolyte solution with low film solubility such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, citrate, etc.

[0137] The diameter of the conductive substrate is, for example, 20 mm or more and 100 mm or less. From the viewpoint of miniaturization of the photoreceptor and the image forming apparatus, the diameter of the conductive substrate is preferably 20 mm or more and 30 mm or less, more preferably 20 mm or more and 24 mm or less. The conductive substrate may be a cylinder or a column.

[0138] [Underlying layer] The underlying layer is, for example, a layer containing inorganic particles and a binder resin.

[0139] Examples of the inorganic particles include inorganic particles having a powder resistance (volume resistivity) of 1 × 10 2 Ωcm or more and 1 × 10 11 Ωcm or less. Among these, examples of the inorganic particles having the above resistance value include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, and particularly, zinc oxide particles are preferable.

[0140] The specific surface area of the inorganic particles by the BET method is, for example, 10 m 2 / g or more. The volume average particle diameter of the inorganic particles is, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

[0141] The content of the inorganic particles is preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, based on the binder resin.

[0142] The inorganic particles may be surface-treated. The inorganic particles may be used by mixing two or more kinds having different surface treatments or different particle diameters.

[0143] Examples of the surface treatment agent include silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, surfactants, and the like. In particular, silane coupling agents are preferable, and silane coupling agents having an amino group are more preferable.

[0144] Examples of the silane coupling agent having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, etc.

[0145] Two or more silane coupling agents may be mixed and used. For example, a silane coupling agent having an amino group and another silane coupling agent may be used in combination. Examples of this other silane coupling agent include, but are not limited to, vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, etc.

[0146] The surface treatment method using the surface treatment agent may be any known method, and either a dry method or a wet method may be used.

[0147] The treatment amount of the surface treatment agent is preferably, for example, 0.5% by mass or more and 10% by mass or less based on the inorganic particles.

[0148] Here, it is preferable that the underlayer contains an electron-accepting compound (acceptor compound) together with the inorganic particles from the viewpoints of enhancing the long-term stability of electrical characteristics and carrier blocking property.

[0149] Examples of the electron-accepting compound include quinone compounds such as chloranil and bromanil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; diphenoquinone compounds such as 3,3’,5,5’-tetra-t-butyldiphenoquinone; benzophenone compounds; and other electron-transporting substances, etc. In particular, as the electron-accepting compound, a compound having an anthraquinone structure is preferable. Examples of the compound having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, amino-hydroxyanthraquinone compounds, etc., and specifically, for example, anthraquinone, alizarin, quinizarin, anthralfin, purpurin, etc. are preferable.

[0150] The electron-accepting compound may be dispersed and contained together with inorganic particles in the undercoat layer, or may be contained in a state of adhering to the surface of the inorganic particles.

[0151] Examples of the method for adhering the electron-accepting compound to the surface of the inorganic particles include a dry method or a wet method.

[0152] The dry method is, for example, a method in which while stirring inorganic particles with a mixer having a large shearing force, etc., an electron-accepting compound dissolved directly or in an organic solvent is dropped and sprayed together with dry air or nitrogen gas to adhere the electron-accepting compound to the surface of the inorganic particles. When dropping or spraying the electron-accepting compound, it is preferably performed at a temperature below the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be further performed at 100°C or higher. The baking is not particularly limited as long as it is a temperature and time at which electrophotographic characteristics can be obtained.

[0153] The wet method is, for example, a method in which inorganic particles are dispersed in a solvent by means of stirring, ultrasonic waves, a sand mill, an attritor, a ball mill, etc., an electron-accepting compound is added, and after stirring or dispersing, the solvent is removed to adhere the electron-accepting compound to the surface of the inorganic particles. The solvent removal method is, for example, removed by filtration or distillation. After the solvent is removed, baking may be further performed at 100 °C or higher. The baking is not particularly limited as long as the electrophotographic characteristics can be obtained at the temperature and time. In the wet method, the contained moisture of the inorganic particles may be removed before adding the electron-accepting compound, and examples thereof include a method of removing while stirring and heating in a solvent and a method of removing by azeotroping with the solvent.

[0154] The adhesion of the electron-accepting compound may be performed before or after subjecting the inorganic particles to surface treatment with a surface treatment agent, or may be performed simultaneously with the surface treatment with the surface treatment agent.

[0155] The content of the electron-accepting compound is, for example, preferably 0.01% by mass or more and 20% by mass or less, more preferably 0.01% by mass or more and 10% by mass or less, based on the inorganic particles.

[0156] Examples of the binder resin used for the undercoat layer include known polymer compounds such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; known materials such as silane coupling agents. Examples of the binder resin used for the undercoat layer include a charge transport resin having a charge transport group, a conductive resin (such as polyaniline, etc.).

[0157] Among these, as the binder resin used for the undercoat layer, a resin insoluble in the coating solvent of the upper layer is preferable. In particular, thermosetting resins such as urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin; at least one resin selected from the group consisting of polyamide resin, polyester resin, polyether resin, methacrylic resin, acrylic resin, polyvinyl alcohol resin, and polyvinyl acetal resin and a resin obtained by the reaction of a curing agent are preferable. When two or more of these binder resins are used in combination, the mixing ratio is set as required.

[0158] The undercoat layer may contain various additives for improving electrical characteristics, environmental stability, and image quality. Examples of the additives include known materials such as polycyclic condensed type and azo type electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. The silane coupling agent is used for the surface treatment of inorganic particles as described above, but may be further added to the undercoat layer as an additive.

[0159] Examples of silane coupling agents as additives include vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, and the like.

[0160] Examples of zirconium chelate compounds include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, zirconium butoxide acetylacetonate, zirconium butoxide ethyl acetoacetate, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium butoxide methacrylate, zirconium butoxide stearate, zirconium butoxide isostearate, and the like.

[0161] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, poly titanium acetylacetonate, titanium octylene glycolate, ammonium salt of titanium lactate, titanium lactate, ethyl ester of titanium lactate, titanium triethanolamineate, polyhydroxy titanium stearate, and the like.

[0162] Examples of the aluminum chelate compound include aluminum isopropylate, monobutoxy aluminum diisopropylate, aluminum butyrate, ethyl acetoacetate aluminum diisopropylate, aluminum tris(ethyl acetoacetate), and the like.

[0163] These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0164] The undercoat layer preferably has a Vickers hardness of 35 or more. The surface roughness (ten-point mean roughness) of the undercoat layer is preferably adjusted to be from 1 / (4n) (n is the refractive index of the upper layer) to 1 / 2 of the laser wavelength λ used for exposure in order to suppress moiré images. Resin particles or the like may be added to the undercoat layer for adjusting the surface roughness. Examples of the resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. Further, the surface of the undercoat layer may be polished for adjusting the surface roughness. Examples of the polishing method include buff polishing, sandblasting treatment, wet honing, and grinding treatment.

[0165] The formation of the undercoat layer is not particularly limited, and known formation methods are used. For example, it is carried out by forming a coating film of a coating solution for forming an undercoat layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0166] Examples of the solvent for preparing the coating solution for forming an undercoat layer include known organic solvents such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include ordinary organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene, and the like.

[0167] Examples of the method for dispersing inorganic particles when preparing the coating liquid for forming the underlayer include known methods such as roll mills, ball mills, vibration ball mills, attritors, sand mills, colloid mills, paint shakers, and the like.

[0168] Examples of the method for applying the coating liquid for forming the underlayer onto the conductive substrate include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, curtain coating, and the like.

[0169] The thickness of the underlayer is, for example, preferably set within a range of 15 μm or more, more preferably 20 μm or more and 50 μm or less.

[0170] [Intermediate layer] An intermediate layer may be further provided between the underlayer and the photosensitive layer. The intermediate layer is, for example, a layer containing a resin. Examples of the resin used for the intermediate layer include polymer compounds such as acetal resins (such as polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, melamine resins, and the like. The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used for the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. These compounds used for the intermediate layer may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0171] Among these, it is preferable that the intermediate layer is a layer containing an organometallic compound containing a zirconium atom or a silicon atom.

[0172] The formation of the intermediate layer is not particularly limited, and known formation methods are used. For example, it is carried out by forming a coating film of a coating solution for forming the intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary. As the coating method for forming the intermediate layer, ordinary methods such as dip coating method, dip-up coating method, wire bar coating method, spray coating method, blade coating method, air knife coating method, and curtain coating method are used.

[0173] The thickness of the intermediate layer is, for example, preferably set in the range of 0.1 μm or more and 3 μm or less. The intermediate layer may be used as an undercoat layer.

[0174] [Charge Generation Layer] The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Further, the charge generation layer may be a vapor deposition layer of a charge generation material. The vapor deposition layer of the charge generation material is suitable when using a non-interfering light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array.

[0175] Examples of the charge generation material include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthraquinone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; trigonal selenium, etc.

[0176] Among these, in order to be compatible with laser exposure in the near-infrared region, as the charge generation material, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment. Specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine are more preferable.

[0177] On the other hand, in order to be compatible with laser exposure in the near-ultraviolet region, as the charge generation material, condensed polycyclic aromatic pigments such as dibromoanthraquinone, thioindigo-based pigments, porphyrazine compounds, zinc oxide, trigonal selenium, bisazo pigments, etc. are preferable.

[0178] When using non-coherent light sources such as LEDs and organic EL image arrays with a center wavelength of emission between 450 nm and 780 nm, the above charge generation materials may also be used. However, from the perspective of resolution, when the photosensitive layer is used as a thin film of 20 μm or less, the electric field strength in the photosensitive layer becomes high, and charge injection from the substrate causes charge leakage, so-called black dots, which are image defects that are likely to occur. This is particularly significant when using charge generation materials that are prone to dark current in p-type semiconductors such as trigonal selenium and phthalocyanine pigments.

[0179] On the other hand, when using n-type semiconductors such as condensed polycyclic aromatic pigments, perylene pigments, and azo pigments as the charge generation material, dark current is less likely to occur, and image defects called black dots can be suppressed even in thin films. The determination of n-type is made using the commonly used time-of-flight method, and is determined by the polarity of the flowing photocurrent. Those that are more likely to conduct electrons than holes as carriers are defined as n-type.

[0180] The binder resin used in the charge generation layer is selected from a wide range of insulating resins, and as the binder resin, it may also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of the binder resin include polyvinyl butyral resin, polyarylate resin (such as a polycondensate of bisphenols and aromatic dicarboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinyl pyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinyl pyrrolidone resin, etc. Here, "insulating property" means that the volume resistivity is 1×10 13 Ω·cm or more. These binder resins are used alone or in combination of two or more.

[0181] The mixing ratio of the charge generation material and the binder resin is preferably in the range of 10:1 to 1:10 by mass ratio.

[0182] The charge generation layer may also contain other known additives.

[0183] The formation of the charge generation layer is not particularly limited, and known formation methods are used. For example, a coating film of a coating solution for forming a charge generation layer obtained by adding the above components to a solvent is formed, and the coating film is dried and heated as necessary. The charge generation layer may be formed by vapor deposition of the charge generation material. The formation of the charge generation layer by vapor deposition is particularly suitable when a condensed aromatic pigment or a perylene pigment is used as the charge generation material.

[0184] 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, toluene, etc. These solvents are used alone or in combination of two or more.

[0185] As a method of dispersing particles (for example, charge generation materials) in a coating solution for forming a charge generation layer, for example, media dispersers such as ball mills, vibration ball mills, attritors, sand mills, horizontal sand mills, etc., and media-less dispersers such as stirring, ultrasonic dispersers, roll mills, high-pressure homogenizers, etc. are used. As high-pressure homogenizers, for example, a collision method in which a dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision in a high-pressure state, a penetration method in which it penetrates through a fine flow path in a high-pressure state, etc. can be mentioned. At the time of this dispersion, it is effective to make the average particle size of the charge generation material in the coating solution for forming the charge generation layer 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0186] As a method of applying the coating solution for forming the charge generation layer on the undercoat layer (or on the intermediate layer), for example, ordinary methods such as blade coating method, wire bar coating method, spray coating method, dipping coating method, bead coating method, air knife coating method, curtain coating method, etc. can be mentioned.

[0187] The thickness of the charge generation layer is set, for example, preferably in the range of 0.1 μm or more and 5.0 μm or less, more preferably 0.2 μm or more and 2.0 μm or less.

[0188] [Charge Transport Layer] The charge transport layer is a layer containing a charge transport material and a polyarylate resin (1).

[0189] Examples of the charge transport material include quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and electron transport compounds such as ethylene compounds. Examples of the charge transport material also include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination of two or more, but are not limited thereto.

[0190] From the viewpoint of charge mobility, as the charge transport material, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2) are preferable.

[0191] [Chemical formula]

[0192] In the structural formula (a-1), Ar T1 , Ar T2 , and Ar T3 each independently represent a substituted or unsubstituted aryl group, -C6H4-C(R T4 )=C(R T5 )(R T6 ), or -C6H4-CH=CH-CH=C(R T7 )(R T8 ). R T4 , R T5 , R T6 , R T7 , and R T8 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Examples of the substituents of each of the above groups include a halogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Further, examples of the substituents of each of the above groups also include a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0193]

Chemical formula

[0194] In structural formula (a-2), R T91 and R T92 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. R T101 , R T102 , R T111 and R T112 each independently represent a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ), and R T12 , R T13 , R T14 , R T15 and R T16 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, Tn1, and Tn2 each independently represent an integer of 0 or more and 2 or less. Examples of the substituents of each of the above groups include a halogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Further, examples of the substituents of each of the above groups also include a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0195] Among the triarylamine derivative represented by structural formula (a-1) and the benzidine derivative represented by structural formula (a-2), "-C6H4-CH=CH-CH=C(R T7 )(RT8 ) having a triarylamine derivative and "-CH=CH-CH=C(R T15 )(R T16 ) having a benzidine derivative is preferable from the viewpoint of charge mobility.

[0196] Examples of the polymer charge transport material include known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane. Among them, polyester-based polymer charge transport materials are preferable.

[0197] From the viewpoint of the electrical properties of the photoreceptor, the charge transport material preferably contains at least one selected from the group consisting of the compound represented by the following formula (1), the compound represented by formula (2), the compound represented by formula (3), and the compound represented by formula (4). In the present disclosure, the compound represented by formula (1) is referred to as "compound (1)", the compound represented by formula (2) is referred to as "compound (2)", the compound represented by formula (3) is referred to as "compound (3)", and the compound represented by formula (4) is referred to as "compound (4)".

[0198] [Chemical formula]

[0199] In formula (1), n 11 is an integer of 0 or more and 5 or less, and n 11 R's 11 are each independently an alkyl group having 1 or more and 6 or less carbon atoms or an alkoxy group having 1 or more and 6 or less carbon atoms, and n 12 is an integer of 0 or more and 5 or less, and n 12 R's 12 are each independently an alkyl group having 1 or more and 6 or less carbon atoms or an alkoxy group having 1 or more and 6 or less carbon atoms, and n 13 is an integer of 0 or more and 5 or less, and n 13 R's 13 are each independently an alkyl group having 1 or more and 6 or less carbon atoms or an alkoxy group having 1 or more and 6 or less carbon atoms, and R 14is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms.

[0200] In formula (1), R 11 , R 12 , R 13 and R 14 are each independently preferably an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms, still more preferably an alkyl group having 1 or 2 carbon atoms or an alkoxy group having 1 or 2 carbon atoms, and particularly preferably a methyl group or a methoxy group.

[0201] In formula (1), n 11 , n 12 and n 13 are each independently preferably an integer of 0 or more and 3 or less, more preferably an integer of 0 or more and 2 or less, and still more preferably 0 or 1.

[0202]

Chemical formula

[0203] In formula (2), R 21 , R 22 , R 23 , R 24 , R 25 and R 26 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and adjacent substituents may be bonded to form a hydrocarbon ring structure.

[0204] In formula (2), examples of the substituent for substituting the aryl group include a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and a phenyl group.

[0205] In formula (2), R21 , R 22 , R 23 , R 24 , R 25 and R 26 are each independently preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms, still more preferably a hydrogen atom, an alkyl group having 1 or 2 carbon atoms or an alkoxy group having 1 or 2 carbon atoms, and particularly preferably a hydrogen atom, a methyl group or a methoxy group.

[0206]

Chemical formula

[0207] In formula (3), R 31 , R 32 , R 33 , R 34 , R 35 , R 36 and R 37 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and n is 0 or 1.

[0208] In formula (3), examples of the substituent for substituting the aryl group include a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and a phenyl group.

[0209] In formula (3), R 31 , R 32 , R 33 , R 34 , R 35 , R 36 and R 37Each is independently preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms, still more preferably a hydrogen atom, an alkyl group having 1 or 2 carbon atoms, or an alkoxy group having 1 or 2 carbon atoms, and particularly preferably a hydrogen atom, a methyl group, or a methoxy group.

[0210] In formula (3), n is preferably 1.

[0211]

Chemical formula

[0212] In formula (4), R 41 , R 42 , R 43 , R 44 , R 45 , and R 46 are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, m is 0 or 1, and n is 0 or 1.

[0213] In formula (4), examples of the substituent for substituting the aryl group include a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and a phenyl group.

[0214] In formula (4), R 41 , R 42 , R 43 , R 44 , R 45 , and R 46 are each independently preferably a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms, still more preferably a hydrogen atom, an alkyl group having 1 or 2 carbon atoms, or an alkoxy group having 1 or 2 carbon atoms, and particularly preferably a hydrogen atom, a methyl group, or a methoxy group.

[0215] In formula (4), m is preferably 1 and n is preferably 1.

[0216] In Tables 1 to 2, Compounds (3-1) to (3-32) are shown as specific examples of Compound (3). Compound (3) is not limited thereto. In Tables 1 to 2, “-Me” means a methyl group, “-OMe” means a methoxy group, and the numbers attached to “-Me” and “-OMe” mean the positions on the benzene ring.

[0217] [Table 1]

[0218] [Table 2]

[0219] In Table 3, Compounds (4-1) to (4-20) are shown as specific examples of Compound (4). Compound (4) is not limited thereto. In Table 3, “-Me” means a methyl group, “-OMe” means a methoxy group, and the numbers attached to “-Me” and “-OMe” mean the positions on the benzene ring.

[0220] [Table 3]

[0221] Among Compound (1), Compound (2), Compound (3) and Compound (4), from the viewpoint of the electrical characteristics of the photoreceptor, Compound (1), Compound (2) and Compound (3) are preferable, and Compound (1) and Compound (2) are more preferable.

[0222] The content of the charge transport material contained in the charge transport layer is 56% by mass or more and 70% by mass or less, preferably 58% by mass or more and 68% by mass or less, and more preferably 60% by mass or more and 65% by mass or less, based on the mass of the charge transport layer.

[0223] The charge transport layer contains at least polyarylate resin (1) as a binder resin. The proportion of polyarylate resin (1) in the total amount of resin contained in the charge transport layer is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

[0224] The charge transport layer may contain other binder resins other than polyarylate resin (1). Examples of other binder resins include polyester resins other than polyarylate resin (1), polycarbonate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, polysilane, and the like. These binder resins may be used alone or in combination of two or more.

[0225] An example of an embodiment of the charge transport layer contains polyarylate resin (1) and polycarbonate resin as binder resins. In this case, the mass ratio of the two resins is preferably polyarylate resin (1): polycarbonate resin = 95:5 to 30:70.

[0226] As the polycarbonate resin, a polycarbonate resin having consecutive structural units having an aromatic ring is preferable, and specific examples include the polycarbonate resin used in the examples described later.

[0227] The charge transport layer may also contain other known additives. Examples of the additives include antioxidants, leveling agents, defoaming agents, fillers, viscosity modifiers, and the like.

[0228] The formation of the charge transport layer is not particularly limited, and known formation methods are used. For example, it is carried out by forming a coating film of a coating solution for forming a charge transport layer in which the above components are added to a solvent, and drying and, if necessary, heating the coating film.

[0229] Examples of the solvent for preparing the coating solution for forming the charge transport layer include 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 ordinary organic solvents such as cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents may be used alone or in combination of two or more.

[0230] Examples of the coating method when applying the coating solution for forming the charge transport layer onto the charge generation layer include ordinary methods such as blade coating method, wire bar coating method, spray coating method, dip coating method, bead coating method, air knife coating method, and curtain coating method.

[0231] The thickness of the charge transport layer is, for example, preferably set within the range of 5 μm or more and 50 μm or less, more preferably 10 μm or more and 40 μm or less.

[0232] [Protective layer] The protective layer is provided on the photosensitive layer as necessary. The protective layer is provided, for example, for the purpose of preventing chemical changes in the photosensitive layer during charging or further improving the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a layer composed of a cured film (crosslinked film) as the protective layer. Examples of these layers include the layers shown in the following 1) or 2).

[0233] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton in the same molecule (that is, a layer containing a polymer or crosslinked product of the reactive group-containing charge transport material) 2) A layer composed of a cured film of a composition containing a non-reactive charge transport material and a reactive group-containing non-charge transport material having no charge transport skeleton and having a reactive group (that is, a layer containing a non-reactive charge transport material and a polymer or crosslinked product of the reactive group-containing non-charge transport material)

[0234] Examples of the reactive group of the reactive group-containing charge transport material include chain polymerizable groups, epoxy groups, -OH, -OR [wherein R represents an alkyl group], -NH2, -SH, -COOH, -SiR Q1 3-Qn (OR Q2 ) Qn [wherein R Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group, and R Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group. Qn represents an integer of 1 to 3] and other known reactive groups can be mentioned.

[0235] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization. For example, it is a functional group having a group containing at least a carbon double bond. Specifically, groups containing at least one selected from a vinyl group, a vinyl ether group, a vinyl thioether group, a phenylvinyl group, a vinylphenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof can be mentioned. Among them, since it has excellent reactivity, the chain polymerizable group is preferably a group containing at least one selected from a vinyl group, a phenylvinyl group, a vinylphenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof.

[0236] The charge transport skeleton of the reactive group-containing charge transport material is not particularly limited as long as it is a known structure in an electrophotographic photoreceptor. For example, it is a skeleton derived from a nitrogen-containing hole transport compound such as a triarylamine-based compound, a benzidine-based compound, or a hydrazone-based compound, and has a structure conjugated with a nitrogen atom. Among these, a triarylamine skeleton is preferable.

[0237] The reactive group-containing charge transport material having these reactive groups and charge transport skeletons, the non-reactive charge transport material, and the reactive group-containing non-charge transport material may be selected from known materials.

[0238] The protective layer may also contain other known additives.

[0239] The formation of the protective layer is not particularly limited, and known formation methods are used. For example, it is performed by forming a coating film of a coating solution for forming a protective layer in which the above components are added to a solvent, drying the coating film, and performing a curing treatment such as heating as necessary.

[0240] Examples of the solvent for preparing the coating solution for forming the protective layer include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; cellosolve solvents such as ethylene glycol monomethyl ether; and alcohol solvents such as isopropyl alcohol and butanol. These solvents may be used alone or in combination of two or more. The coating solution for forming the protective layer may be a solvent-free coating solution.

[0241] Examples of the method of applying the coating solution for forming the protective layer onto the photosensitive layer (for example, the charge transport layer) include ordinary methods such as dip coating method, push-up coating method, wire bar coating method, spray coating method, blade coating method, air knife coating method, and curtain coating method.

[0242] The thickness of the protective layer is, for example, preferably set within the range of 1 μm or more and 20 μm or less, more preferably 2 μm or more and 10 μm or less.

[0243] <Image forming apparatus, process cartridge> The image forming apparatus according to this embodiment includes an electrophotographic photosensitive member, a charging device that charges the surface of the electrophotographic photosensitive member, an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photosensitive member, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image, and a transfer device that transfers the toner image onto the surface of a recording medium. And, as the electrophotographic photosensitive member, the electrophotographic photosensitive member according to this embodiment is applied.

[0244] The image forming apparatus according to this embodiment is a known image forming apparatus such as an apparatus including a fixing device that fixes the toner image transferred onto the surface of a recording medium; a direct transfer type apparatus that directly transfers the toner image formed on the surface of the electrophotographic photosensitive member onto the recording medium; an intermediate transfer type apparatus that primarily transfers the toner image formed on the surface of the electrophotographic photosensitive member onto the surface of an intermediate transfer member and secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of the recording medium; an apparatus including a cleaning device that cleans the surface of the electrophotographic photosensitive member after transfer of the toner image and before charging; an apparatus including a discharging device that discharges the surface of the electrophotographic photosensitive member by irradiating it with discharging light after transfer of the toner image and before charging; an apparatus including an electrophotographic photosensitive member heating member for raising the temperature of the electrophotographic photosensitive member and reducing the relative humidity, etc.

[0245] In the case of an intermediate transfer type apparatus, the transfer device has, for example, a configuration including an intermediate transfer member onto which the toner image is transferred on its surface, a primary transfer device that primarily transfers the toner image formed on the surface of the electrophotographic photosensitive member onto the surface of the intermediate transfer member, and a secondary transfer device that secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of the recording medium.

[0246] The image forming apparatus according to this embodiment may be either a dry developing type image forming apparatus or a wet developing type (developing method using a liquid developer) image forming apparatus.

[0247] In the image forming apparatus according to the present embodiment, for example, a portion including the electrophotographic photoreceptor may be a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photoreceptor according to the present embodiment is preferably used. The process cartridge may include at least one selected from the group consisting of, for example, a charging device, an electrostatic latent image forming device, a developing device, and a transfer device, in addition to the electrophotographic photoreceptor.

[0248] Hereinafter, an example of the image forming apparatus according to the present embodiment is shown, but the present invention is not limited thereto. The main parts shown in the drawings will be described, and the description of the others will be omitted.

[0249] FIG. 2 is a schematic configuration diagram showing an example of the image forming apparatus according to the present embodiment. As shown in FIG. 2, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (a primary transfer device), and an intermediate transfer member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 via the intermediate transfer member 50, and a part of the intermediate transfer member 50 is disposed in contact with the electrophotographic photoreceptor 7. Although not shown, the image forming apparatus 100 also has 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 a transfer device.

[0250] In FIG. 2, the process cartridge 300 integrally supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging device), a developing device 11 (an example of a developing device), and a cleaning device 13 (an example of a cleaning device) inside a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is arranged to contact the surface of the electrophotographic photoreceptor 7. The cleaning member may be a conductive or insulating fibrous member instead of the form of the cleaning blade 131, and this may be used alone or in combination with the cleaning blade 131.

[0251] FIG. 2 shows an example of an image forming apparatus including a fibrous member 132 (in a roll shape) for supplying a lubricant 14 to the surface of the electrophotographic photoreceptor 7 and a fibrous member 133 (in a flat brush shape) for assisting cleaning, but these are arranged as needed.

[0252] Hereinafter, each component of the image forming apparatus according to the present embodiment will be described.

[0253] - Charging device - As the charging device 8, for example, a contact charger using a conductive or semiconductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. is used. Also, a non-contact type roller charger, a charger known per se such as a scorotron charger or a corotron charger using corona discharge, etc. are also used.

[0254] - Exposure device - As the exposure device 9, for example, an optical system device that exposes light such as semiconductor laser light, LED light, and liquid crystal shutter light onto the surface of the electrophotographic photoreceptor 7 in a defined image pattern can be mentioned. The wavelength of the light source is set within the spectral sensitivity region of the electrophotographic photoreceptor. As the wavelength of the semiconductor laser, near-infrared light having an oscillation wavelength around 780 nm is the mainstream. However, it is not limited to this wavelength, and lasers having an oscillation wavelength in the 600 nm range or lasers having an oscillation wavelength between 400 nm and 450 nm, such as blue lasers, may also be used. Also, for color image formation, a surface-emitting type laser light source of a type that can output multi-beams is also effective.

[0255] -Developing device- As the developing device 11, for example, a general developing device that develops by bringing the developer into contact or non-contact can be mentioned. The developing device 11 is not particularly limited as long as it has the above-described functions, and is selected according to the purpose. For example, known developers 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 can be mentioned. Among these, those using a developing roller that holds the developer on its surface are preferable.

[0256] The developer used in the developing device 11 may be a one-component developer consisting of only toner, or a two-component developer containing toner and carrier. Also, the developer may be magnetic or non-magnetic. Known developers are applicable to these.

[0257] -Cleaning device- As the cleaning device 13, a cleaning blade type device including a cleaning blade 131 is used. In addition to the cleaning blade method, a fur brush cleaning method or a simultaneous development and cleaning method may be adopted.

[0258] -Transfer device- As the transfer device 40, for example, known transfer chargers such as a contact type transfer charger using a belt, a roller, a film, a rubber blade, etc., a scorotron transfer charger using corona discharge, or a corotron transfer charger can be mentioned.

[0259] -Intermediate transfer member- As the intermediate transfer member 50, a belt-shaped member (intermediate transfer belt) containing polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. imparted with semiconductive properties is used. Also, as the form of the intermediate transfer member, a drum-shaped member may be used in addition to the belt-shaped one.

[0260] Figure 3 is a schematic configuration diagram showing another example of the image forming apparatus according to the present embodiment. The image forming apparatus 120 shown in Figure 3 is a tandem type full-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer member 50, and a configuration is adopted in which one electrophotographic photoreceptor is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100 except that it is of the tandem type.

Example

[0261] Hereinafter, embodiments of the invention will be described in detail by way of examples, but the embodiments of the invention are not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are based on mass. In the following description, unless otherwise specified, synthesis, production, processing, measurement, etc. were carried out at room temperature (25°C ± 3°C).

[0262] <Production of polyarylate resin (1)> [Polyarylate resin (1-1)] Into a reaction vessel equipped with a stirring device, 12.6373 g of 4,4'-(2-ethylhexylidene)diphenol, 0.1233 g of 4-tert-butylphenol, 0.0632 g of sodium hydrosulfite, and 240 mL of water were added to form a suspension. To this suspension, 4.8392 g of sodium hydroxide, 0.1981 g of benzyltributylammonium chloride, and 160 mL of water were added at 20 °C under stirring, and the mixture was stirred for 30 minutes under a nitrogen atmosphere. 220 mL of o-dichlorobenzene was added to this aqueous solution, and after stirring for 30 minutes under a nitrogen atmosphere, 12.0000 g of 4,4'-biphenyldicarbonyl chloride was added as a powder. After the addition was completed, the mixture was stirred at 20 °C for 4 hours under a nitrogen atmosphere to allow the reaction to proceed. The polymerized solution was diluted with 300 mL of o-dichlorobenzene, and the aqueous phase was removed. After washing with a dilute acetic acid solution and ion-exchanged water, the mixture was poured into methanol to precipitate the polymer. The precipitated polymer was separated by filtration and dried at 50 °C. This polymer was redissolved in 900 mL of tetrahydrofuran and poured into methanol to precipitate the polymer. The precipitated polymer was separated by filtration, washed with methanol, and dried at 50 °C to obtain 17.5 g of a white polymer. Molecular weight measurement by GPC (gel permeation chromatography) was performed using tetrahydrofuran as an eluent, and the molecular weight of the polymer was determined as the molecular weight in terms of polystyrene. The weight average molecular weight of the polymer was 100,000. The chemical structure of the polyarylate resin (1-1) is shown below.

[0263] [Chemical formula]

[0264] <Manufacture of photoreceptor> [Example 1] -Formation of undercoat layer- As a conductive substrate, an aluminum cylindrical tube with an outer diameter of 30 mm, a length of 365 mm, and a wall thickness of 1 mm was prepared.

[0265] Zinc oxide (average particle diameter 70 nm, specific surface area 15 m 2100 parts of zinc oxide (manufactured by Teika Co., Ltd.) were stirred and mixed with 500 parts of toluene, and 1.3 parts of a silane coupling agent (trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) were added, followed by stirring for 2 hours. Then, toluene was distilled off under reduced pressure, and baking was carried out at 120 °C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent.

[0266] 110 parts of the surface-treated zinc oxide were stirred and mixed with 500 parts of tetrahydrofuran, and a solution prepared by dissolving 0.6 part of alizarin in 50 parts of tetrahydrofuran was added, followed by stirring at 50 °C for 5 hours. Then, the solid content was separated by filtration under reduced pressure, and drying under reduced pressure was carried out at 60 °C to obtain alizarin-imparted zinc oxide.

[0267] 60 parts of the alizarin-imparted zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, trade name: Sumidur 3175, manufactured by Sumitomo Bayer Urethane Co., Ltd.), and 15 parts of a butyral resin (trade name: Esrec BM-1, manufactured by Sekisui Chemical Co., Ltd.) were dissolved in 100 parts of a solution in 68 parts of methyl ethyl ketone, and 5 parts of methyl ethyl ketone were mixed. Using glass beads with a diameter of 1 mm, dispersion was carried out in a sand mill for 2 hours to obtain a dispersion. To the dispersion, 0.005 part of dioctyltin dilaurate as a catalyst and 4 parts of silicone resin particles (trade name: Tospearl 145, manufactured by Momentive Performance Materials Inc.) were added to obtain a coating solution for forming an undercoat layer. The coating solution for forming an undercoat layer was applied to the outer peripheral surface of a conductive substrate by the dip coating method, and drying and curing were carried out at 170 °C for 40 minutes to form an undercoat layer with an average thickness of 25 μm.

[0268] - Formation of Charge Generation Layer - 15 parts of hydroxygallium phthalocyanine as a charge generating substance (having diffraction peaks at positions with Bragg angles (2θ ± 0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1° and 28.3° in the X-ray diffraction spectrum using CuKα characteristic X-rays), 10 parts of a vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate were 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 were added to the dispersion and stirred to obtain a coating solution for forming a charge generation layer. The coating solution for forming a charge generation layer was dip-coated on the undercoat layer and dried at room temperature (25°C ± 3°C) to form a charge generation layer with an average thickness of 0.18 μm.

[0269] - Formation of Charge Transport Layer - 30 parts of polyarylate resin (1-1) as a binder resin and 70 parts of CTM(1) as a charge transport material were dissolved in 135 parts of tetrahydrofuran and 15 parts of toluene to obtain a coating solution for forming a charge transport layer. The coating solution for forming a charge transport layer was dip-coated on the charge generation layer and dried at 145°C for 30 minutes to form a charge transport layer with an average thickness of 32 μm.

[0270] [Examples 2 - 26, Comparative Examples 1 - 6] In the same manner as in Example 1, except that the outer diameter of the conductive substrate and the type and amount of the charge transport material used for forming the charge transport layer were changed to the specifications described in Table 4, each photoreceptor was produced. In Example 10, a part of the polyarylate resin (1-1) was replaced with polycarbonate resin (1-1) in the formation of the charge transport layer to produce a photoreceptor. The chemical structure of the polycarbonate resin (1-1) is shown below. The numerical values in the structural formula of the polycarbonate resin (1-1) are molar ratios.

[0271]

Chemical Formula

[0272] <Performance Evaluation of Photoreceptor> [Abrasion resistance] The photoreceptor was installed in an electrophotographic image forming apparatus (Apeos C7070, manufactured by Fujifilm Business Innovation Corp.). Under the environment of a temperature of 10°C and a relative humidity of 15%, on A3-sized paper, 100,000 solid images with an image density (area coverage) of 100% were formed. Before and after this image formation, the average thickness of the charge transport layer was determined, and the difference in the average thickness before and after image formation was taken as the wear amount. As the film thickness measuring instrument, a Permascope manufactured by Fischer Scope was used. The wear amount was classified as follows. The results are shown in Table 4. G0: Wear amount is less than 0.5 μm G0.5: Wear amount is 0.5 μm or more and less than 1 μm G1: Wear amount is 1 μm or more and less than 3 μm G2: Wear amount is 3 μm or more

[0273] [Electrical characteristics] The photoreceptor was installed in an electrophotographic image forming apparatus (Apeos C7070 modified machine, a modified machine with the process speed changed). Under the environment of a temperature of 10°C and a relative humidity of 15%, on A3-sized paper, 1000 solid images with an image density (area coverage) of 100% were formed. This image formation was carried out at a process speed of 308 mm / sec and a process speed of 400 mm / sec, respectively. After the first sheet was output and after 1000 sheets were output, the residual potential on the surface of the photoreceptor was measured respectively, and the difference in the absolute value was determined and taken as the increase value of the absolute value of the residual potential. This was classified as follows. The results are shown in Table 4. G0: Increase value of the absolute value of the residual potential is less than 10 V G0.5: Increase value of the absolute value of the residual potential is 10 V or more and less than 30 V G1: Increase value of the absolute value of the residual potential is 30 V or more and less than 50 V G2: Increase value of the absolute value of the residual potential is 50 V or more

[0274] "PS308" and "PS400" described in Table 4 respectively mean a process speed of 308 mm / sec and a process speed of 400 mm / sec.

[0275] The chemical structures of charge transport materials CTM(1) to CTM(5) are shown below.

[0276] [Chemical formula]

[0277] [Table 4]

[0278] The electrophotographic photoreceptor, process cartridge, and image forming apparatus of the present disclosure include the following aspects. Each formula representing a compound is the same as the formula with the same number described above.

[0279] (((1))) A photoreceptor layer having a conductive substrate and a charge generation layer and a charge transport layer disposed on the conductive substrate, wherein the charge transport layer contains a charge transport material and a polyarylate resin having a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B), and the mass ratio of the charge transport material in the charge transport layer is 56% by mass or more and 70% by mass or less. Electrophotographic photoreceptor. (((2))) The electrophotographic photoreceptor according to (((1))), wherein the mass ratio of the charge transport material in the charge transport layer is 60% by mass or more and 65% by mass or less. (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), wherein the charge transport material contains at least one selected from the group consisting of a compound represented by formula (1), a compound represented by formula (2), a compound represented by formula (3), and a compound represented by formula (4). (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the diameter of the electrophotographic photoreceptor is 25 mm or less. (((5))) An electrophotographic photoreceptor according to any one of ((1)) to ((4)), A process cartridge detachable from an image forming apparatus. ((6)) An electrophotographic photoreceptor according to any one of ((1)) to ((4)), and A charging device for charging the surface of the electrophotographic photoreceptor, An electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, A developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, A transfer device for transferring the toner image onto the surface of a recording medium, An image forming apparatus comprising the same.

[0280] According to ((1)), ((3)) or ((4)), there is provided an electrophotographic photoreceptor excellent in electrical characteristics and abrasion resistance as compared with an electrophotographic photoreceptor in which the mass ratio of the charge transport material in the charge transport layer is less than 56% by mass or more than 70% by mass. According to ((2)), there is provided an electrophotographic photoreceptor excellent in electrical characteristics and abrasion resistance as compared with an electrophotographic photoreceptor in which the mass ratio of the charge transport material in the charge transport layer is less than 60% by mass or more than 65% by mass. According to ((5)), there is provided a process cartridge including an electrophotographic photoreceptor excellent in electrical characteristics and abrasion resistance as compared with an electrophotographic photoreceptor in which the mass ratio of the charge transport material in the charge transport layer is less than 56% by mass or more than 70% by mass. According to ((6)), there is provided an image forming apparatus including an electrophotographic photoreceptor excellent in electrical characteristics and abrasion resistance as compared with an electrophotographic photoreceptor in which the mass ratio of the charge transport material in the charge transport layer is less than 56% by mass or more than 70% by mass.

Explanation of Signs

[0281] 1 Conductive substrate, 2 Undercoat layer, 3 Charge generation layer, 4 Charge transport layer, 5 Photosensitive layer, 10A Photoreceptor

[0282] 7 Electrophotographic photoreceptor, 8 Charging device, 9 Exposure device, 11 Developing device, 13 Cleaning device, 14 Lubricant, 40 Transfer device, 50 Intermediate transfer body, 100 Image forming apparatus, 120 Image forming apparatus, 131 Cleaning blade, 132 Fibrous member (roll shape), 133 Fibrous member (flat brush shape), 300 Process cartridge

Claims

1. An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer disposed on the conductive substrate and having a charge generation layer and a charge transport layer. The charge transport layer contains a charge transport material and a polyarylate resin having a dicarboxylic acid unit represented by the following formula (A) and a diol unit represented by the following formula (B). The mass ratio of the charge transport material in the charge transport layer is 56% by mass or more and 70% by mass or less. Electrophotographic photoreceptor. 【Chemical 1】 In formula (A), n １ is 1, 2 or 3, and n １ number of m １ are each independently 0, 1, 2, 3 or 4, and m １ number of Ra １ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms or an alkoxy group having 1 to 6 carbon atoms. In formula (B), Rb １ and Rb ２ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb ３ , Rb ４ , Rb ５ , Rb ６ , Rb ７ , Rb ８ , Rb ９ and Rb １０ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, and Rb １ and Rb ２ may be bonded to form a cyclic alkyl group.

2. The electrophotographic photoreceptor according to claim 1, wherein the mass ratio of the charge transport material in the charge transport layer is 60% by mass or more and 65% by mass or less.

3. The electrophotographic photoreceptor according to claim 1, wherein the charge transport material contains at least one selected from the group consisting of a compound represented by the following formula (1), a compound represented by the following formula (2), a compound represented by the following formula (3), and a compound represented by the following formula (4). [Chemical 2] In formula (1), n １１ is an integer of 0 or more and 5 or less, and n １１ number of R １１ are each independently an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and n １２ is an integer of 0 or more and 5 or less, and n １２ number of R １２ are each independently an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and n １３ is an integer of 0 or more and 5 or less, and n １３ number of R １３ are each independently an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and R １４ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms. In formula (2), R ２１ , R ２２ , R ２３ , R ２４ , R ２５ , and R ２６ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and adjacent substituents may be bonded to form a hydrocarbon ring structure. In formula (3), R ３１ , R ３２ , R ３３ , R ３４ , R ３５ , R ３６ , and R ３７ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, and n is 0 or 1. In formula (4), R ４１ , R ４２ , R ４３ , R ４４ , R ４５ , and R ４６ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, m is 0 or 1, and n is 0 or 1.

4. The electrophotographic photoreceptor according to claim 1, wherein the diameter of the electrophotographic photoreceptor is 25 mm or less.

5. A process cartridge detachably attached to an image forming apparatus, the process cartridge including the electrophotographic photoreceptor according to any one of claims 1 to 4.

6. An image forming apparatus comprising the electrophotographic photoreceptor according to any one of claims 1 to 4, a charging device for charging the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, and a transfer device for transferring the toner image onto the surface of a recording medium. ​

Images