Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

In the present invention, a first photosensitive layer of an electrophotographic photoreceptor is provided on the side, of a photosensitive layer constituted of at least one layer, furthest toward the front surface. The first photosensitive layer contains a charge-generating agent, a binder resin, an electron transport agent, and a hole transport agent. The binder resin includes a polyarylate resin having repeating units (1), (2), (3), and (4). The content percentage of the repeating unit (3) in relation to the sum of the repeating units (1) and (3) is greater than 0% but less than 50%. The content percentage of the repeating unit (4) in relation to the sum of the repeating units (2) and (4) is greater than or equal to 35% but less than 70%. The electron transport agent includes a compound represented by formula (10), (11), or (12). The hole transport agent includes a compound represented by formula (21) and (22).

Description

[Technical field]

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

[0002] Electrophotographic photoreceptors are used as image carriers in electrophotographic image forming apparatuses (e.g., printers or multifunction machines). Electrophotographic photoreceptors include a photosensitive layer. As electrophotographic photoreceptors, for example, single-layer electrophotographic photoreceptors and multi-layer electrophotographic photoreceptors are used. The single-layer electrophotographic photoreceptor includes a single photosensitive layer having a charge generation function and a charge transport function. The multi-layer electrophotographic photoreceptor includes a photosensitive layer including a charge generation layer having a charge generation function and a charge transport layer having a charge transport function.

[0003] Patent Document 1 describes an electrophotographic photoreceptor having a surface layer containing a polyarylate resin obtained from a divalent carboxylic acid component and a dihydric phenol component, as shown in the following formula.

[0004] [ka] [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-20514 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the present inventors have found through their studies that the electrophotographic photoreceptor described in Patent Document 1 is insufficient in terms of increasing the solubility of the binder resin in a solvent to form a good photosensitive layer. The present inventors have also found through their studies that the electrophotographic photoreceptor described in Patent Document 1 is insufficient in terms of sensitivity characteristics, crack resistance of the photosensitive layer, and suppression of crystallization of the photosensitive layer.

[0007] The present invention has been made in view of the above problems, and its object is to provide an electrophotographic photoreceptor capable of forming a good photosensitive layer, suppressing crystallization of the photosensitive layer, and having excellent crack resistance and sensitivity characteristics of the photosensitive layer. Another object of the present invention is to provide a process cartridge and an image forming apparatus capable of suppressing image defects caused by crystallization and cracks of the photosensitive layer, and capable of forming high-quality images due to excellent sensitivity characteristics. [Means for solving the problem]

[0008] The electrophotographic photoreceptor of the present invention comprises a conductive substrate and at least one photosensitive layer. The at least one photosensitive layer includes a first photosensitive layer. The first photosensitive layer is provided on the outermost side of the at least one photosensitive layer. The first photosensitive layer contains a charge generating agent, a binder resin, an electron transport agent, and a hole transport agent. The binder resin includes a polyarylate resin. The polyarylate resin has repeating units represented by formulas (1), (2), (3), and (4). A third content, which is a content rate of the repeating unit represented by formula (3) relative to the total number of repeating units represented by formulas (1) and (3), is greater than 0% and less than 50%. A fourth content, which is a content rate of the repeating unit represented by formula (4) relative to the total number of repeating units represented by formulas (2) and (4), is 35% or more and less than 70%. The electron transport agent includes a compound represented by formula (10), (11), or (12). The hole transport material includes a first hole transport material and a second hole transport material. The first hole transport material includes a compound represented by formula (21). The second hole transport material includes a compound represented by formula (22).

[0009] [ka]

[0010] In the formula (1), R 1 and R 2 represents a methyl group, and X represents a divalent group represented by formula (X1), or R 1 and R 2 represents a hydrogen atom, and X represents a divalent group represented by formula (X2).

[0011] [ka]

[0012] In the formulae (X1) and (X2), * represents a bond.

[0013] [ka]

[0014] In the formula (10), Q 5A and Q 5B each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. 6A and Q 6B Each of m1 and m2 independently represents an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. Each of m1 and m2 independently represents an integer of 0 to 4. In the formula (11), Q 7 and Q 8 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. 9 represents an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. m3 represents an integer of 0 to 4. In the formula (12), Q 10 and Q 11 Each independently represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. 12represents a halogen atom or a hydrogen atom.

[0015] [ka]

[0016] In the formula (21), R 1A , R 2A , R 3A , R 4A , R 5A , R 6A , R 7A , R 8A , R 9A , and R 10A Each of R in the formula (21) independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms. 1B and R in the formula (22) 1C is R in the formula (21). 1A R in the above formula (21) represents the same group as 2B and R in the formula (22) 2C is R in the formula (21). 2A R in the above formula (21) represents the same group as 3B and R in the formula (22) 3C is R in the formula (21). 3A R in the above formula (21) represents the same group as 4B and R in the formula (22) 4C is R in the formula (21). 4A R in the above formula (21) represents the same group as 5B and R in the formula (22) 5C is R in the formula (21). 5A R in the above formula (21) represents the same group as 6B and R in the formula (22) 6C and R 6D is R in the formula (21). 6A R in the above formula (21) represents the same group as 7B and R in the formula (22) 7C and R 7D is R in the formula (21). 7AR in the above formula (21) represents the same group as 8B and R in the formula (22) 8C and R 8D is R in the formula (21). 8A R in the above formula (21) represents the same group as 9B and R in the formula (22) 9C and R 9D is R in the formula (21). 9A R in the above formula (21) represents the same group as 10B and R in the formula (22) 10C and R 10D is R in the formula (21). 10A In the formula (21), Y represents a divalent group represented by the formula (Y2).

[0017] [ka]

[0018] The process cartridge of the present invention includes at least one selected from the group consisting of a charging device, an exposure device, a developing device, and a transfer device, and the above-mentioned electrophotographic photoreceptor.

[0019] The image forming apparatus of the present invention includes an image carrier, a charging device that charges the surface of the image carrier to a positive polarity, an exposure device that exposes the charged surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier, a developing device that supplies toner to the surface of the image carrier to develop the electrostatic latent image into a toner image, and a transfer device that transfers the toner image from the image carrier to a transferee. The image carrier is the electrophotographic photoreceptor described above. Effect of the Invention

[0020] The electrophotographic photoreceptor of the present invention can form a good photosensitive layer, can suppress crystallization of the photosensitive layer, and has excellent crack resistance and sensitivity characteristics. The process cartridge and image forming apparatus of the present invention can suppress image defects caused by crystallization and cracks of the photosensitive layer, and can form high-quality images due to the excellent sensitivity characteristics. [Brief description of the drawings]

[0021] [Figure 1] 1 is a partial cross-sectional view of a single-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to a first embodiment of the present invention. [Diagram 2] 1 is a partial cross-sectional view of a single-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to a first embodiment of the present invention. [Diagram 3] 1 is a partial cross-sectional view of a single-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to a first embodiment of the present invention. [Figure 4] 1 is a partial cross-sectional view of a positively charged multi-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to a first embodiment of the present invention. [Diagram 5] 1 is a partial cross-sectional view of a positively charged multi-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to a first embodiment of the present invention. [Figure 6] 1 is a partial cross-sectional view of a positively charged multi-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to a first embodiment of the present invention. [Figure 7] FIG. 11 is a diagram illustrating an example of an image forming apparatus according to a second embodiment of the present invention. [Figure 8] 1 is a 1H-NMR spectrum of polyarylate resin (R-1). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, the embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be practiced by making appropriate modifications within the scope of the object of the present invention. Hereinafter, the compound and its derivatives may be collectively referred to by adding "system" after the compound name. In addition, when the compound name is followed by "system" to represent the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. In addition, "general formula" and "chemical formula" are collectively described as "formula". In the explanation of the formula, "independently" means that it may represent the same group or different groups. Each component described in this specification may be used alone or in combination of two or more types, unless otherwise specified.

[0023] First, the substituents used in this specification will be described. Examples of halogen atoms (halogen groups) include fluorine atoms (fluoro groups), chlorine atoms (chloro groups), bromine atoms (bromo groups), and iodine atoms (iodo groups).

[0024] Unless otherwise specified, the alkyl group having 1 to 8 carbon atoms, the alkyl group having 1 to 6 carbon atoms, and the alkyl group having 1 to 3 carbon atoms are each linear or branched and unsubstituted. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylpropyl group, a 2-ethylpropyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, an n-hexyl group, a 1-methylpentyl group, a 2 ... Examples of alkyl groups having 1 to 6 carbon atoms and alkyl groups having 1 to 3 carbon atoms are those groups having the corresponding number of carbon atoms among the groups given as examples of alkyl groups having 1 to 8 carbon atoms.

[0025] Perfluoroalkyl groups having 1 to 10 carbon atoms, perfluoroalkyl groups having 3 to 10 carbon atoms, perfluoroalkyl groups having 5 to 7 carbon atoms, and perfluoroalkyl groups having 6 carbon atoms are linear or branched and unsubstituted, unless otherwise specified. Examples of perfluoroalkyl groups having 1 to 10 carbon atoms include trifluoromethyl, perfluoroethyl, perfluoro-n-propyl, perfluoroisopropyl, perfluoro-n-butyl, perfluoro-sec-butyl, perfluoro-tert-butyl, perfluoro-n-pentyl, perfluoro-1-methylbutyl, perfluoro-2-methylbutyl, perfluoro-3-methylbutyl, perfluoro-1-ethylpropyl, perfluoro-2-ethylpropyl, perfluoro-1,1-dimethylpropyl, perfluoro-1,2-dimethylpropyl, perfluoro-2,2-dimethylpropyl, perfluoro-n-hexyl, perfluoro-1-methylpentyl, perfluoro-2-methylpent ... Examples of perfluoroalkyl groups include fluoro-3-methylpentyl, perfluoro-4-methylpentyl, perfluoro-1,1-dimethylbutyl, perfluoro-1,2-dimethylbutyl, perfluoro-1,3-dimethylbutyl, perfluoro-2,2-dimethylbutyl, perfluoro-2,3-dimethylbutyl, perfluoro-3,3-dimethylbutyl, perfluoro-1,1,2-trimethylpropyl, perfluoro-1,2,2-trimethylpropyl, perfluoro-1-ethylbutyl, perfluoro-2-ethylbutyl, and perfluoro-3-ethylbutyl groups, linear and branched perfluoroheptyl groups, linear and branched perfluorooctyl groups, linear and branched perfluorononyl groups, and linear and branched perfluorodecyl groups. Examples of perfluoroalkyl groups having 3 to 10 carbon atoms, perfluoroalkyl groups having 5 to 7 carbon atoms, and perfluoroalkyl groups having 6 carbon atoms are groups having the corresponding numbers of carbon atoms among the groups mentioned as examples of perfluoroalkyl groups having 1 to 10 carbon atoms.

[0026] The alkanediyl group having 1 to 6 carbon atoms and the alkanediyl group having 1 to 3 carbon atoms are each linear or branched and unsubstituted, unless otherwise specified. Examples of the alkanediyl group having 1 to 6 carbon atoms include a methanediyl group (methylene group), an ethanediyl group, an n-propanediyl group, an isopropanediyl group, an n-butanediyl group, a sec-butanediyl group, a tert-butanediyl group, an n-pentanediyl group, a 1-methylbutanediyl group, a 2-methylbutanediyl group, a 3-methylbutanediyl group, a 1-ethylpropanediyl group, a 2-ethylpropanediyl group, a 1,1-dimethylpropanediyl group, a 1,2-dimethylpropanediyl group, a 2,2-dimethylpropanediyl group, an n-hexane group, and the like. Examples of the alkanediyl group having 1 to 3 carbon atoms include a diyl group, a 1-methylpentanediyl group, a 2-methylpentanediyl group, a 3-methylpentanediyl group, a 4-methylpentanediyl group, a 1,1-dimethylbutanediyl group, a 1,2-dimethylbutanediyl group, a 1,3-dimethylbutanediyl group, a 2,2-dimethylbutanediyl group, a 2,3-dimethylbutanediyl group, a 3,3-dimethylbutanediyl group, a 1,1,2-trimethylpropanediyl group, a 1,2,2-trimethylpropanediyl group, a 1-ethylbutanediyl group, a 2-ethylbutanediyl group, and a 3-ethylbutanediyl group. Examples of the alkanediyl group having 1 to 3 carbon atoms are groups having the corresponding number of carbon atoms among the groups mentioned as examples of the alkanediyl group having 1 to 6 carbon atoms.

[0027] The alkoxy group having 1 to 8 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the alkoxy group having 1 to 3 carbon atoms are each linear or branched and unsubstituted unless otherwise specified. Examples of the alkoxy group having 1 to 8 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, an n-pentoxy group, a 1-methylbutoxy group, a 2-methylbutoxy group, a 3-methylbutoxy group, a 1-ethylpropoxy group, a 2-ethylpropoxy group, a 1,1-dimethylpropoxy group, a 1,2-dimethylpropoxy group, a 2,2-dimethylpropoxy group, an n-hexyloxy group, a 1-methylpentyloxy group, a 2 ... Examples of alkoxy groups having 1 to 6 carbon atoms and alkoxy groups having 1 to 3 carbon atoms are the groups having the corresponding carbon atoms among the groups mentioned as examples of alkoxy groups having 1 to 8 carbon atoms.

[0028] Each of the aryl group having 6 to 14 carbon atoms and the aryl group having 6 to 10 carbon atoms is unsubstituted unless otherwise specified. Examples of the aryl group having 6 to 14 carbon atoms include a phenyl group, a naphthyl group, an indacenyl group, a biphenylenyl group, an acenaphthylenyl group, an anthryl group, and a phenanthryl group. Examples of the aryl group having 6 to 10 carbon atoms include a phenyl group and a naphthyl group. The substituents used in this specification have been described above.

[0029] <First embodiment: electrophotographic photoreceptor> The first embodiment of the present invention relates to an electrophotographic photoreceptor (hereinafter, sometimes referred to as photoreceptor). The photoreceptor of the first embodiment includes a conductive substrate and at least one photosensitive layer. The at least one photosensitive layer includes a first photosensitive layer. The first photosensitive layer is provided on the outermost surface side of the at least one photosensitive layer. The surface side is the outer surface side of the photoreceptor (for example, the surface side on which exposure light is incident), and is the opposite side to the side of the photoreceptor on which the conductive substrate is provided.

[0030] The photoreceptor of the first embodiment is, for example, a single-layer electrophotographic photoreceptor (hereinafter, may be referred to as a single-layer photoreceptor) and a positively charged multilayer electrophotographic photoreceptor (hereinafter, may be referred to as a positively charged multilayer photoreceptor).

[0031] (single-layer photoreceptor) A single-layer photoreceptor 1, which is an example of the photoreceptor of the first embodiment, will be described below with reference to Figures 1 to 3. Each of Figures 1 to 3 shows a partial cross-sectional view of the single-layer photoreceptor 1.

[0032] 1, the single-layer photoreceptor 1 includes, for example, a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 included in the single-layer photoreceptor 1 is a single layer (one layer). The single photosensitive layer 3 is a single-layer photosensitive layer 3s that is a first photosensitive layer.

[0033] As shown in Fig. 2, the single-layer photoreceptor 1 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2 and the single-layer photosensitive layer 3s. The intermediate layer 4 is provided between the conductive substrate 2 and the single-layer photosensitive layer 3s. As shown in Fig. 1, the single-layer photosensitive layer 3s may be provided directly on the conductive substrate 2. Alternatively, as shown in Fig. 2, the single-layer photosensitive layer 3s may be provided on the conductive substrate 2 via the intermediate layer 4.

[0034] As shown in FIG. 3, the single-layer photoreceptor 1 may further include a protective layer 5 in addition to the conductive substrate 2 and the single-layer photosensitive layer 3s. The protective layer 5 is provided on the single-layer photosensitive layer 3s. As shown in FIG. 1 and FIG. 2, the single-layer photosensitive layer 3s is preferably provided as the outermost layer of the single-layer photoreceptor 1. By providing the single-layer photosensitive layer 3s containing a polyarylate resin (PA) described later and a specific electron transport agent described later as the outermost layer, the crack resistance of the single-layer photosensitive layer 3s is easily improved. Note that, as shown in FIG. 3, the protective layer 5 may be provided as the outermost layer of the single-layer photoreceptor 1.

[0035] The thickness of the single-layer type photosensitive layer 3s is not particularly limited, but is preferably from 5 μm to 100 μm, and more preferably from 10 μm to 50 μm.

[0036] The single-layer photosensitive layer 3s, which is the first photosensitive layer, contains a charge generating agent, a binder resin, an electron transport agent, and a hole transport agent. Hereinafter, the "hole transport agent contained in the single-layer photosensitive layer 3s" may be referred to as the "hole transport agent (SL)". The "binder resin contained in the single-layer photosensitive layer 3s" may be referred to as the "binder resin (SL)". The single-layer photosensitive layer 3s may contain additives as necessary. The single-layer photoreceptor 1 has been described above with reference to Figs. 1 to 3.

[0037] (Positively charged laminated photoconductor) A positively charged multi-layer photoreceptor 10, which is an example of the photoreceptor of the first embodiment, will be described below with reference to Figures 4 to 6. Figures 4 to 6 each show a partial cross-sectional view of the positively charged multi-layer photoreceptor 10.

[0038] As shown in FIG. 4, the positively charged laminated photoreceptor 10 includes, for example, a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 of the positively charged laminated photoreceptor 10 is two layers. The two photosensitive layers 3 are a charge generating layer 12 and a charge transport layer 11. The charge generating layer 12 is a first photosensitive layer. The charge transport layer 11 is a second photosensitive layer. The charge generating layer 12, which is the first photosensitive layer, is provided on the most surface side of the two photosensitive layers 3 (the charge generating layer 12 and the charge transport layer 11). The charge transport layer 11 is provided on the conductive substrate 2 side of the charge generating layer 12. Since the charge generating layer 12 is located on the most surface side (the side opposite to the side where the conductive substrate 2 of the positively charged laminated photoreceptor 10 is provided), for example, the charge transport layer 11 is provided on the conductive substrate 2, and the charge generating layer 12 is provided on the charge transport layer 11. When the positively charged multi-layer photoconductor 10 is provided in an image forming apparatus 100 (see FIG. 7), the positively charged multi-layer photoconductor 10 is positively charged by a charging device 42 (see FIG. 7).

[0039] As shown in Fig. 5, the positively charged laminated photoreceptor 10 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2 and the photosensitive layer 3. The intermediate layer 4 is provided between the conductive substrate 2 and the photosensitive layer 3 (e.g., charge transport layer 11). As shown in Fig. 4, the photosensitive layer 3 (e.g., charge transport layer 11) may be provided directly on the conductive substrate 2. Alternatively, as shown in Fig. 5, the photosensitive layer 3 (e.g., charge transport layer 11) may be provided on the conductive substrate 2 via the intermediate layer 4.

[0040] As shown in FIG. 6, the positively charged laminated photoreceptor 10 may further include a protective layer 5 in addition to the conductive substrate 2 and the photosensitive layer 3. The protective layer 5 is provided on the photosensitive layer 3 (e.g., the charge generating layer 12). As shown in FIG. 4 and FIG. 5, the photosensitive layer 3 is preferably provided as the outermost layer of the positively charged laminated photoreceptor 10. By providing the photosensitive layer 3 (e.g., the charge generating layer 12) containing the polyarylate resin (PA) described later and the specific electron transport agent described later as the outermost layer, the crack resistance of the photosensitive layer 3 (e.g., the charge generating layer 12) is easily improved. Note that, as shown in FIG. 6, the protective layer 5 may be provided as the outermost layer of the positively charged laminated photoreceptor 10.

[0041] The thickness of the charge generating layer 12 is preferably from 2 μm to 100 μm, more preferably from 15 μm to 30 μm, and the thickness of the charge transport layer 11 is preferably from 2 μm to 100 μm, more preferably from 3 μm to 20 μm, and even more preferably from 5 μm to 15 μm.

[0042] The charge generation layer 12, which is the first photosensitive layer, contains a charge generation material, a binder resin, an electron transport material, and a hole transport material. Hereinafter, the "hole transport material contained in the charge generation layer 12" may be referred to as the "hole transport material (CG)". Also, the "binder resin contained in the charge generation layer 12" may be referred to as the "binder resin (CG)". The charge generation layer 12 may contain additives as necessary.

[0043] The charge transport layer 11, which is the second photosensitive layer, contains a hole transport agent and a binder resin. Hereinafter, the "hole transport agent contained in the charge transport layer 11" may be referred to as the "hole transport agent (CT)". Also, the "binder resin contained in the charge transport layer 11" may be referred to as the "binder resin (CT)". The charge transport layer 11 may contain additives as necessary. The positively charged multilayer photoreceptor 10 has been described above with reference to Figs. 4 to 6.

[0044] The photoreceptor will be described in more detail below. When it is not necessary to distinguish between the binder resin (SL), the binder resin (CG), and the binder resin (CL), they will be simply referred to as "binder resin". When it is not necessary to distinguish between the hole transport material (SL), the hole transport material (CG), and the hole transport material (CL), they will be simply referred to as "hole transport material".

[0045] (Hole transport agent) The hole transport agents (SL) and (CG) contained in the first photosensitive layer each include a first hole transport agent and a second hole transport agent. The first hole transport agent includes a compound represented by formula (21). The second hole transport agent includes a compound represented by formula (22). Hereinafter, the compounds represented by formulas (21) and (22) may be referred to as hole transport agents (21) and (22), respectively.

[0046] The hole transport material (CT) contained in the second photosensitive layer is not particularly limited. The hole transport material (CT) may contain either the first hole transport material or the second hole transport material, or may contain both. The hole transport material (CT) may also be another hole transport material described later. The hole transport material (CG) and the hole transport material (CT) may be the same or different from each other.

[0047] [ka]

[0048] In formula (21), R 1A , R 2A , R 3A , R 4A , R 5A , R 6A , R 7A , R 8A , R 9A , and R 10A Each of R in formula (21) independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms. 1B , and R in formula (22) 1C is R in Eq. (21). 1A R in formula (21) represents the same group as 2B , and R in formula (22) 2C is R in Eq. (21). 2A R in formula (21) represents the same group as 3B , and R in formula (22) 3C is R in Eq. (21). 3A R in formula (21) represents the same group as 4B , and R in formula (22) 4Cis R in Eq. (21). 4A R in formula (21) represents the same group as 5B , and R in formula (22) 5C is R in Eq. (21). 5A R in formula (21) represents the same group as 6B , and R in formula (22) 6C and R 6D is R in Eq. (21). 6A R in formula (21) represents the same group as 7B , and R in formula (22) 7C and R 7D is R in Eq. (21). 7A R in formula (21) represents the same group as 8B , and R in formula (22) 8C and R 8D is R in Eq. (21). 8A R in formula (21) represents the same group as 9B , and R in formula (22) 9C and R 9D is R in Eq. (21). 9A R in formula (21) represents the same group as 10B , and R in formula (22) 10C and R 10D is R in Eq. (21). 10A In formula (21), Y represents a divalent group represented by formula (Y2).

[0049] [ka]

[0050] The photosensitive layer (particularly, the first photosensitive layer) contains both the hole transport agents (21) and (22), which improves the crack resistance of the photosensitive body (particularly, a single-layer type photosensitive body and a positively charged multi-layer type photosensitive body) and suppresses crystallization of the photosensitive layer. The crack resistance of the photosensitive body is a property that can suppress the occurrence of cracks in the photosensitive layer even if a cleaning agent remains on the surface of the photosensitive body during maintenance. Here, the hole transport agent (22) is a by-product generated when synthesizing the hole transport agent (21), which is the final product. Usually, the final product is obtained by removing the by-product through purification. However, the present inventors have found that the crack resistance of the photosensitive body is improved by deliberately leaving the hole transport agent (22) mixed with the hole transport agent (21) without completely removing the by-product hole transport agent (22) through purification. The present inventors also found that the hole transport agent (22) suppresses aggregation of the hole transport agent (21), thereby suppressing crystallization of the photosensitive layer. Furthermore, the photoreceptor of the first embodiment includes a photosensitive layer containing the hole transport agent (21) that has excellent sensitivity characteristics. Therefore, in addition to suppressing crystallization of the photosensitive layer and improving crack resistance, the sensitivity characteristics of the photoreceptor are also improved.

[0051] R in formula (21) 1A , R 2A , R 3A , R 4A , R 5A , R 6A , R 7A , R 8A , R 9A , and R 10A The alkyl group having 1 to 8 carbon atoms represented by the formula (I) is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and further preferably a methyl group or an ethyl group.

[0052] R in formula (21) 1A , R 2A , R 3A , R 4A , R 5A , R 6A , R 7A , R 8A , R 9A , and R 10AThe alkoxy group having 1 to 8 carbon atoms represented by the formula (I) is preferably an alkoxy group having 1 to 6 carbon atoms, more preferably an alkoxy group having 1 to 3 carbon atoms, and even more preferably a methoxy group.

[0053] R in formula (21) 1A , R 2A , R 3A , R 4A , R 5A , R 6A , R 7A , R 8A , R 9A , and R 10A The aryl group having 6 to 14 carbon atoms represented by is preferably an aryl group having 6 to 10 carbon atoms.

[0054] In order to improve the crack resistance of the photoconductor and suppress crystallization, R 1A , R 2A , R 3A , R 4A , R 5A , R 6A , R 7A , R 8A , R 9A , and R 10A At least two of R represent a group other than a hydrogen atom. 1A , R 2A , R 3A , R 4A , R 5A , R 6A , R 7A , R 8A , R 9A , and R 10A The remainder of R preferably represents a hydrogen atom. The total number of carbon atoms of the groups other than the hydrogen atom is preferably 3 or more. 1A , R 2A , R 3A , R 4A , R 5A , R 6A , R 7A , R 8A , R 9A , and R 10AThe group other than a hydrogen atom represented by is an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

[0055] In order to improve the crack resistance of the photoconductor and suppress crystallization, R 3A preferably represents an alkoxy group having 1 to 8 carbon atoms.

[0056] In order to improve the crack resistance of the photoconductor and suppress crystallization, R 1A , R 3A , and R 5A one or two of represent an alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms; R 1A , R 3A , and R 5A The remainder of the groups represent hydrogen atoms, and R 2A , and R 4A Preferably, each represents a hydrogen atom.

[0057] In order to improve the crack resistance of the photoconductor and suppress crystallization, R 8A represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms; R 6A , R 7A , R 9A , and R 10A preferably represents a hydrogen atom.

[0058] In order to improve the sensitivity characteristics and crack resistance of the photoreceptor and suppress crystallization, it is preferable that the hole transport agent (21) is a compound represented by formula (HTM-1) and the hole transport agent (22) is a compound represented by formula (HTM-A). For the same reason, it is preferable that the hole transport agent (21) is a compound represented by formula (HTM-2) and the hole transport agent (22) is a compound represented by formula (HTM-B). For the same reason, it is preferable that the hole transport agent (21) is a compound represented by formula (HTM-3) and the hole transport agent (22) is a compound represented by formula (HTM-C). For the same reason, it is preferable that the hole transport agent (21) is a compound represented by formula (HTM-4) and the hole transport agent (22) is a compound represented by formula (HTM-D). Hereinafter, the compounds represented by the formulae (HTM-1) to (HTM-4) may be referred to as hole transport agents (HTM-1) to (HTM-4), respectively. Also, the compounds represented by the formulae (HTM-A) to (HTM-D) may be referred to as hole transport agents (HTM-A) to (HTM-D), respectively.

[0059] [ka]

[0060] The content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22) is preferably 1.0% by mass or more and 30.0% by mass or less, more preferably 1.0% by mass or more and 10.0% by mass or less, and even more preferably 2.0% by mass or more and 5.0% by mass or less. When the content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22) is 1.0% by mass or more, the crack resistance of the photoreceptor can be further improved and the crystallization of the photoreceptor can be further suppressed. When the content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22) is 30.0% by mass or less, the sensitivity characteristics of the photoreceptor can be improved. A method for adjusting the content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22) will be described later in "Method for producing a hole transport agent".

[0061] The content of the hole transport agent (SL) relative to 100 parts by mass of the binder resin (SL) (i.e., the total content of the hole transport agents (21) and (22)) is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 50 parts by mass or more and 150 parts by mass or less, and even more preferably 60 parts by mass or more and 100 parts by mass or less. The content of the hole transport agent (CG) relative to 100 parts by mass of the binder resin (CG) (i.e., the total content of the hole transport agents (21) and (22)) is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 50 parts by mass or more and 150 parts by mass or less, and even more preferably 60 parts by mass or more and 100 parts by mass or less. The content of the hole transport agent (CT) per 100 parts by mass of the binder resin (CT) (i.e., the total content of the hole transport agents (21) and (22)) is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 50 parts by mass or more and 150 parts by mass or less, and even more preferably 70 parts by mass or more and 130 parts by mass or less.

[0062] The first photosensitive layer may contain only the hole transport agents (21) and (22) as the hole transport agent. Alternatively, the first photosensitive layer may further contain, in addition to the hole transport agents (21) and (22), hole transport agents other than these (hereinafter, may be referred to as other hole transport agents). Examples of other hole transport agents include triphenylamine derivatives, diamine derivatives (e.g., N,N,N',N'-tetraphenylbenzidine derivatives, N,N,N',N'-tetraphenylphenylenediamine derivatives, N,N,N',N'-tetraphenylnaphthylenediamine derivatives, N,N,N',N'-tetraphenylphenanthrylenediamine derivatives, and di(aminophenylethenyl)benzene derivatives), oxadiazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole derivatives, and di(aminophenylethenyl)benzene derivatives). azoles), styryl compounds (e.g., 9-(4-diethylaminostyryl)anthracene), carbazole compounds (e.g., polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (e.g., 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

[0063] (Method of manufacturing hole transport material) An example of a method for producing a hole transport agent will be described below. The method for producing a hole transport agent includes a first stirring step and a second stirring step. In the first stirring step, a mixed liquid (hereinafter sometimes simply referred to as "liquid") is subjected to a first stirring step. The liquid contains a compound represented by formula (A) and a compound represented by formula (B). In the second stirring step, a compound represented by formula (C) is further added to the liquid obtained in the first stirring step, and the liquid is subjected to a second stirring step. After the first stirring step, the second stirring step is performed without purifying the liquid. Through the first stirring step and the second stirring step, a hole transport agent containing both the first hole transport agent and the second hole transport agent (i.e., a mixture of hole transport agents (21) and (22)) is obtained. The obtained mixture of hole transport agents (21) and (22) is used as a hole transport agent in the photosensitive layer forming step. Hereinafter, the compounds represented by formulas (A), (B), and (C) may be referred to as compounds (A), (B), and (C), respectively.

[0064] [ka]

[0065] R in formula (A) 1 , R 2 , R 3 , R 4 , and R 5 are R in formula (21), 1A , R 2A , R 3A , R 4A , and R 5A R in formula (B) represents the same group as 6 , R 7 , R 8 , R 9 , and R 10 are R in formula (21), 6A , R 7A , R 8A , R 9A , and R 10A Z in formula (B) represents the same group as 1 represents a halogen atom. Y in formula (C) represents the same group as Y in formula (21). Z in formula (C) 2 and Z 3 represents a halogen atom.

[0066] As shown in the following reaction formula (r-1), 1 molar equivalent of compound (A) reacts with 2 molar equivalents of compound (B) to obtain 1 molar equivalent of hole transport agent (22). In the first stirring step, the reaction shown in reaction formula (r-1) proceeds. Note that the reaction shown in reaction formula (r-1) may proceed not only in the first stirring step but also in the second stirring step.

[0067] [ka]

[0068] Also, as shown in the following reaction formulas (r-2) and (r-3), 2 molar equivalents of compound (A), 2 molar equivalents of compound (B), and 1 molar equivalent of compound (C) react to obtain 1 molar equivalent of hole transport agent (21). More specifically, as shown in reaction formula (r-2), 2 molar equivalents of compound (A) react with 2 molar equivalents of compound (B) to obtain 2 molar equivalents of compound represented by formula (D) (hereinafter, sometimes referred to as compound (D)). Compound (D) is an intermediate product. Next, as shown in reaction formula (r-3), 2 molar equivalents of compound (D) react with 1 molar equivalent of compound (C) to obtain 1 molar equivalent of hole transport agent (21). In the first stirring step, the reaction shown in reaction formula (r-2) proceeds, and in the second stirring step, the reaction shown in reaction formula (r-3) proceeds. Note that the reaction represented by reaction formula (r-2) may proceed not only in the first stirring step but also in the second stirring step.

[0069] [ka]

[0070] Since the raw materials of the hole transport materials (21) and (22) are the same as compound (A), R 1 is R in Eq. (21). 1A , and R 1B , and R in formula (22)1C It is the same group as R 1 Similarly, R in formula (A) 2 ~R 5 The raw materials for the hole transport materials (21) and (22) are the same as the compound (B), so that R 6 is R in Eq. (21). 6A and R 6B , and R in formula (22) 6C and R 6D R 6 Similarly, R in formula (B) 7 ~R 10 are the same groups as the corresponding substituents in formulae (21) and (22).

[0071] A palladium catalyst may be added to the liquid to be first stirred in the first stirring step and the liquid to be second stirred in the second stirring step. Examples of the palladium catalyst include palladium(II) acetate, palladium(II) chloride, sodium hexachloropalladate(IV) tetrahydrate, and tris(dibenzylideneacetone)dipalladium(0).

[0072] A ligand may be added to the liquid to be first stirred in the first stirring step and the liquid to be second stirred in the second stirring step. Examples of the ligand include 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl, (4-dimethylaminophenyl)di-tertbutylphosphine, tricyclohexylphosphine, triphenylphosphine, and methyldiphenylphosphine.

[0073] A base may be added to the liquid to be first stirred in the first stirring step and the liquid to be second stirred in the second stirring step. Examples of the base include sodium tert-butoxide, tripotassium phosphate, and cesium fluoride.

[0074] A solvent may be added to the liquid to be first stirred in the first stirring step and the liquid to be second stirred in the second stirring step. Examples of the solvent include xylene, toluene, tetrahydrofuran, and dimethylformamide.

[0075] The temperature of the liquid to be first stirred in the first stirring step and the liquid to be second stirred in the second stirring step is preferably 80° C. or more and 140° C. or less. The time for the first stirring is preferably 1 hour or more and 10 hours or less, more preferably 5 hours or more and 10 hours or less. The time for the second stirring is preferably 1 hour or more and 10 hours or less, more preferably 1 hour or more and 4 hours or less. The first stirring and the second stirring may be performed under an atmosphere of an inert gas (e.g., nitrogen gas or argon gas).

[0076] In the hole transport agent manufacturing process, the solution is not purified after the first stirring step. This simplifies the hole transport agent manufacturing process. Furthermore, through the first stirring step and the second stirring step, the hole transport agents (21) and (22) are simultaneously obtained in a mixture state. Since they are obtained in a mixture state, it is possible to omit the task of measuring and mixing the hole transport agents (21) and (22) separately when preparing the coating solution in the photosensitive layer forming step.

[0077] In the hole transport agent production process, the hole transport agent (22) remains in the hole transport agent obtained in the second stirring step. By intentionally leaving the hole transport agent (22) as a by-product without completely removing it, both the hole transport agents (21) and (22) can be contained in the photosensitive layer. This can improve the crack resistance of the photoreceptor and suppress crystallization of the photoreceptor. Note that purification may be performed after the second stirring step so that the hole transport agent (22) is not completely removed. Also, purification may be performed after the second stirring step so that the hole transport agent (21) is not completely removed. Examples of purification methods after the second stirring step include activated clay treatment, recrystallization, and combinations thereof.

[0078] The content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22) can be adjusted, for example, by changing the ratio (B / A) of the amount of the added compound (B) relative to the amount of the added compound (A). The ratio (B / A) is a molar ratio value. The higher the ratio (B / A), the higher the content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22). The ratio (B / A) is preferably 1.05 or more and 1.45 or less, and more preferably 1.05 or more and 1.25 or less.

[0079] The content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22) can be adjusted, for example, by changing the ratio (A / C) of the amount of the compound (A) added to the amount of the compound (C). The ratio (A / C) is a molar ratio value. The higher the ratio (A / C), the higher the content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22). The ratio (A / C) is preferably 2.30 or more and 3.30 or less, and more preferably 2.30 or more and 2.60 or less.

[0080] The content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22) can be adjusted, for example, by performing purification after the second stirring step without completely removing the hole transport agent (22) and by changing the purification conditions. In order to adjust the content of the hole transport agent (22) relative to the total mass of the hole transport agents (21) and (22), one or both of the hole transport agents (21) and (22) may be further added to the hole transport agent obtained through the first stirring step and the second stirring step.

[0081] (binder resin) The binder resins (SL) and (CG) contained in the first photosensitive layer each contain a polyarylate resin. This polyarylate resin has repeating units represented by formulas (1), (2), (3), and (4). In the polyarylate resin, the third content is greater than 0% and less than 50%. The third content is the content of the repeating unit represented by formula (3) relative to the total number of repeating units represented by formulas (1) and (3). In the polyarylate resin, the fourth content is 35% or more and less than 70%. The fourth content is the content of the repeating unit represented by formula (4) relative to the total number of repeating units represented by formulas (2) and (4).

[0082] [ka]

[0083] In formula (1), R 1 and R 2 represents a methyl group, and X represents a divalent group represented by formula (X1). 1 and R 2 represents a hydrogen atom, and X represents a divalent group represented by formula (X2).

[0084] [ka]

[0085] In formulae (X1) and (X2), * represents a bond. The bond represented by * in formulae (X1) and (X2) is bonded to the carbon atom to which X in formula (1) is bonded.

[0086] Hereinafter, "repeating units represented by formulas (1), (2), (3), and (4)" may be referred to as "repeating units (1), (2), (3), and (4)," respectively. Also, "a polyarylate resin having repeating units (1), (2), (3), and (4), in which the third content is greater than 0% and less than 50%, and the fourth content is 35% or more and less than 70%" may be referred to as "polyarylate resin (PA)."

[0087] The binder resin (CL) contained in the second photosensitive layer is not particularly limited, and may contain a polyarylate resin (PA) or other binder resins described later. The binder resin (CG) and the binder resin (CT) may be the same or different from each other.

[0088] The photosensitive layer (particularly the first photosensitive layer) contains polyarylate resin (PA) in addition to the first hole transport material, the second hole transport material, and the specific electron transport material, so that the crack resistance of the photosensitive layer can be particularly improved. Also, since polyarylate resin (PA) has excellent solubility in solvents, the photosensitive layer (particularly the first photosensitive layer) can be formed well.

[0089] In formula (1), R 1 and R 2 When R represents a methyl group and X represents a divalent group represented by formula (X1), the repeating unit (1) is a repeating unit represented by formula (1-1) (hereinafter, sometimes referred to as repeating unit (1-1)). 1 and R 2 When represents a hydrogen atom and X represents a divalent group represented by formula (X2), the repeating unit (1) is a repeating unit represented by formula (1-2) (hereinafter, may be referred to as repeating unit (1-2)). The polyarylate resin (PA) may have only one type of repeating unit (1), or may have two types of repeating units (1).

[0090] [ka]

[0091] The content of the repeating unit (1) relative to the total number of the repeating units (1) and (3) is referred to as the first content. The first content corresponds to the percentage of the number M1 of the repeating units (1) relative to the sum of the number M1 of the repeating units (1) and the number M3 of the repeating units (3) contained in the polyarylate resin (PA) (i.e., 100×M1 / (M1+M3)). Note that when the polyarylate resin (PA) has two types of repeating units (1), the number M1 of the repeating units (1) is the total number of the two types of repeating units (1).

[0092] The first content is preferably less than 100%, more preferably 99% or less, even more preferably 90% or less, even more preferably 80% or less, even more preferably 70% or less, even more preferably less than 70%, and particularly preferably 65% ​​or less. The first content is preferably greater than 50%, more preferably 51% or more, and even more preferably 55% or more. The first content is preferably greater than 50% and less than 70%, and even more preferably greater than 50% and less than 70%.

[0093] The content of the repeating unit (2) relative to the total number of the repeating units (2) and (4) is referred to as the second content. The second content corresponds to the percentage of the number M2 of the repeating units (2) relative to the sum of the number M2 of the repeating units (2) and the number M4 of the repeating units (4) contained in the polyarylate resin (PA) (i.e., 100×M2 / (M2+M4)).

[0094] The second content is preferably 65% ​​or less, and more preferably 60% or less. The second content is preferably greater than 30%, more preferably 31% or more, even more preferably 35% or more, even more preferably 40% or more, and particularly preferably 55% or more. The second content is preferably greater than 30% and 60% or less. The second content is also preferably 55% or more and 65% or less.

[0095] As already described, the third content is greater than 0% and less than 50%. The third content corresponds to the percentage of the number M3 of repeating units (3) relative to the total of the number M1 of repeating units (1) and the number M3 of repeating units (3) contained in the polyarylate resin (PA) (i.e., 100×M3 / (M1+M3)).

[0096] When the third content is less than 50%, the solubility of the polyarylate resin (PA) in a solvent is improved, and the photosensitive layer can be formed well. When the third content is greater than 0%, that is, the third content is not 0%, the abrasion resistance of the photoreceptor when the polyarylate resin (PA) is contained in the photosensitive layer can be improved. The third content is preferably 1% or more, more preferably 10% or more, even more preferably 20% or more, even more preferably 30% or more, still more preferably greater than 30%, and particularly preferably 35% or more. In addition, the third content is preferably 49% or less, and more preferably 45% or less.

[0097] In order to suppress crystallization of the photosensitive layer and improve the crack resistance and sensitivity characteristics of the photosensitive layer, the third content is preferably 30% or more and less than 50%, and more preferably more than 30% and less than 50%.

[0098] As described above, the fourth content is 35% or more and less than 70%. The fourth content corresponds to the percentage of the number M4 of repeating units (4) relative to the total number M2 of repeating units (2) and the number M4 of repeating units (4) contained in the polyarylate resin (PA) (i.e., 100×M4 / (M2+M4)).

[0099] In order to form a good photosensitive layer, suppress crystallization of the photosensitive layer, and improve the crack resistance and sensitivity characteristics of the photosensitive layer, the fourth content is 35% or more and less than 70%. The fourth content is preferably 40% or more. In addition, the fourth content is preferably 69% or less, more preferably 65% ​​or less, even more preferably 60% or less, and even more preferably 45% or less.

[0100] In order to suppress crystallization of the photosensitive layer and improve the crack resistance and sensitivity characteristics of the photosensitive layer, the fourth content is preferably 40% or more and less than 70%. For the same reason, the fourth content is also preferably 35% or more and 45% or less.

[0101] The first content, the second content, the third content, and the fourth content are each determined by measuring the amount of the polyarylate resin (PA) using a proton nuclear magnetic resonance spectrometer. 1 The H-NMR spectrum was measured and 1 It can be calculated from the ratio of peaks characteristic of each repeating unit in the H-NMR spectrum.

[0102] In order to form the photosensitive layer well, suppress the crystallization of the photosensitive layer, and improve the crack resistance and sensitivity characteristics of the photosensitive layer, it is preferable that the first content is different from the second content and different from the fourth content. For the same reason, it is preferable that the third content is different from the second content and different from the fourth content.

[0103] In order to form a good photosensitive layer, suppress crystallization of the photosensitive layer, and improve the crack resistance and sensitivity characteristics of the photosensitive layer, R 1 and R 2 represents a methyl group, and X represents a divalent group represented by formula (X1), and the fourth content is preferably 40% or more and less than 70%.

[0104] In order to form a good photosensitive layer, suppress crystallization of the photosensitive layer, and improve the crack resistance and sensitivity characteristics of the photosensitive layer, R 1 and R 2 represents a methyl group, and X represents a divalent group represented by formula (X1), and the third content is preferably 30% or more and less than 50%.

[0105] In order to form a good photosensitive layer, suppress crystallization of the photosensitive layer, and improve the crack resistance and sensitivity characteristics of the photosensitive layer, R 1 and R 2represents a hydrogen atom, and X represents a divalent group represented by formula (X2), and the fourth content is preferably 35% or more and 45% or less.

[0106] The polyarylate resin (PA) may not have a repeating unit having a biphenyl structure. Examples of the repeating unit having a biphenyl structure include a repeating unit represented by formula (5). Examples of the repeating unit represented by formula (5) include repeating units represented by formulas (5-1) and (5-2).

[0107] [ka]

[0108] [ka]

[0109] The polyarylate resin (PA) may not have a repeating unit derived from isophthalic acid.

[0110] The polyarylate resin (PA) may have a terminal group. Examples of the terminal group of the polyarylate resin (PA) include terminal groups represented by formulas (T-1) and (T-2). The terminal group represented by formula (T-1) is preferably a terminal group represented by formula (T-DMP) (hereinafter, may be referred to as terminal group (T-DMP)). The terminal group represented by formula (T-2) is preferably a terminal group represented by formula (T-PFH) (hereinafter, may be referred to as terminal group (T-PFH)).

[0111] [ka]

[0112] In formula (T-1), R 11 represents an alkyl group having 1 to 6 carbon atoms or a halogen atom, and p represents an integer of 0 to 5. 11preferably represents an alkyl group having 1 to 6 carbon atoms, more preferably represents an alkyl group having 1 to 3 carbon atoms, and even more preferably represents a methyl group. p preferably represents an integer of 1 to 3, and more preferably represents 2.

[0113] In formula (T-2), R 12 represents an alkanediyl group having 1 to 6 carbon atoms, and Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms. 12 preferably represents an alkanediyl group having from 1 to 3 carbon atoms, and more preferably represents a methylene group. Rf preferably represents a perfluoroalkyl group having from 3 to 10 carbon atoms, more preferably represents a perfluoroalkyl group having from 5 to 7 carbon atoms, and even more preferably represents a perfluoroalkyl group having 6 carbon atoms.

[0114] The * in the formulae (T-1), (T-2), (T-DMP), and (T-PFH) represents a bond. The bond represented by the * in the formulae (T-1), (T-2), (T-DMP), and (T-PFH) is bonded to a repeating unit derived from a dicarboxylic acid (more specifically, repeating unit (2) or (4)) located at the end of the polyarylate resin (PA).

[0115] In order to form a good photosensitive layer, suppress crystallization of the photosensitive layer, and improve the crack resistance and sensitivity characteristics of the photosensitive layer, it is preferable that the polyarylate resin (PA) has an end group having a halogen atom. For the same reason, in formula (1), R 1 and R 2 It is more preferable that X represents a divalent group represented by the formula (X1), and the polyarylate resin (PA) has a terminal group having a halogen atom.

[0116] An example of a terminal group having a halogen atom is R 11 represents a halogen atom. Another example of an end group having a halogen atom is the end group (T-2).

[0117] Suitable examples of the polyarylate resin (PA) include polyarylate resins (PA-1) to (PA-2) shown in Table 1. The polyarylate resins (PA-1) to (PA-2) each have the repeating units (1) to (4) shown in Table 1. More suitable examples of the polyarylate resin (PA) include polyarylate resins (PA-a) to (PA-d) shown in Table 2. The polyarylate resins (PA-a) to (PA-d) each have the repeating units (1) to (4) shown in Table 2 and the terminal groups shown in Table 2. In Tables 1 and 2, "units (1) to (4)" respectively refer to "repeating units (1) to (4)".

[0118] [Table 1]

[0119] [Table 2]

[0120] In the polyarylate resin (PA), the repeating unit derived from bisphenol (more specifically, the repeating unit (1) or (3)) and the repeating unit derived from dicarboxylic acid (more specifically, the repeating unit (2) or (4)) are adjacent to each other and bonded to each other. That is, the repeating unit (1) may be bonded to the repeating unit (2) or to the repeating unit (4). The repeating unit (3) may be bonded to the repeating unit (2) or to the repeating unit (4). The number of the repeating units derived from bisphenol is approximately the same as the number of the repeating units derived from dicarboxylic acid, and satisfies the formula "the number of repeating units derived from dicarboxylic acid = the number of repeating units derived from bisphenol + 1". The polyarylate resin (PA) may be, for example, a random copolymer, an alternating copolymer, a periodic copolymer, or a block copolymer.

[0121] The polyarylate resin (PA) may further have repeating units other than the repeating units (1) to (4) as repeating units. However, in order to form a good photosensitive layer, suppress crystallization of the photosensitive layer, and improve the crack resistance and sensitivity characteristics of the photosensitive layer, the content of the repeating units (1) to (4) in the total number of repeating units contained in the polyarylate resin (PA) is preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, even more preferably 99% or more, and particularly preferably 100%. That is, it is particularly preferable that the polyarylate resin (PA) has only the repeating units (1) to (4) as repeating units.

[0122] The content of repeating unit (1) relative to the total number of repeating units derived from bisphenol contained in the polyarylate resin (PA) is preferably greater than 50% and less than 100%, more preferably 55% to 90%, even more preferably 60% to 80%, even more preferably 60% to 70%, and even more preferably 60% to 70%. The content of repeating unit (3) relative to the total number of repeating units derived from bisphenol contained in the polyarylate resin (PA) is preferably greater than 0% and less than 50%, more preferably 10% to 45%, even more preferably 20% to 40%, even more preferably 30% to 40%, and even more preferably more than 30% to 40%.

[0123] The content of the repeating unit (2) relative to the total number of repeating units derived from dicarboxylic acid contained in the polyarylate resin (PA) is preferably more than 30% and not more than 65%, more preferably 35% or more and not more than 65%, and even more preferably 40% or more and not more than 60%. The content of the repeating unit (4) relative to the total number of repeating units derived from dicarboxylic acid contained in the polyarylate resin (PA) is preferably 35% or more and less than 70%, more preferably 35% or more and not more than 65%, and even more preferably 40% or more and not more than 60%.

[0124] The viscosity average molecular weight of the polyarylate resin (PA) is preferably 10,000 or more, more preferably 30,000 or more, even more preferably 35,000 or more, even more preferably 50,000 or more, and particularly preferably 55,000 or more. When the viscosity average molecular weight of the polyarylate resin (PA) is 10,000 or more, the abrasion resistance of the photoreceptor is improved when the polyarylate resin (PA) is contained in the photosensitive layer of the photoreceptor. On the other hand, the viscosity average molecular weight of the polyarylate resin (PA) is preferably 80,000 or less, more preferably 70,000 or less, and even more preferably 60,000 or less. When the viscosity average molecular weight of the polyarylate resin (PA) is 80,000 or less, the solubility of the polyarylate resin (PA) in a solvent is improved. The viscosity average molecular weight of the polyarylate resin (PA) is measured according to JIS (Japanese Industrial Standards) K7252-1:2016.

[0125] In order to form a good photosensitive layer, suppress crystallization of the photosensitive layer, and improve the crack resistance and sensitivity characteristics of the photosensitive layer, the ratio of the mass of the binder resin (SL) to the mass of the first photosensitive layer and the ratio of the mass of the binder resin (CG) to the mass of the first photosensitive layer are preferably 0.35 or more and 0.50 or less. When the binder resin (SL) contains two or more resins, the mass of the binder resin (SL) is the total mass of the two or more resins. When the binder resin (CG) contains two or more resins, the mass of the binder resin (CG) is the total mass of the two or more resins.

[0126] Next, the method for producing polyarylate resin (PA) will be described. For example, the method for producing polyarylate resin (PA) includes a method of polycondensing bisphenol for forming a repeating unit derived from bisphenol and dicarboxylic acid for forming a repeating unit derived from dicarboxylic acid. For polycondensation, a known synthesis method (for example, solution polymerization, melt polymerization, or interfacial polymerization) can be adopted.

[0127] Examples of bisphenols for constituting the repeating units derived from bisphenols include compounds represented by formulae (BP-1) and (BP-3) (hereinafter, these may be referred to as compounds (BP-1) and (BP-3), respectively). Examples of dicarboxylic acids for constituting the repeating units derived from dicarboxylic acids include compounds represented by formulae (DC-2) and (DC-4) (hereinafter, these may be referred to as compounds (DC-2) and (DC-4), respectively). R in formula (BP-1) 1 , R 2 , and X is R in formula (1). 1 , R 2 , and X.

[0128] [ka]

[0129] In the production of polyarylate resin (PA), the first content is adjusted by changing the amount (unit: mole) of compound (BP-1) added relative to the total amount (unit: mole) of compounds (BP-1) and (BP-3) added. The first content corresponds to the molar fraction (unit: mole%) of repeating unit (1) in the total amount of repeating units (1) and (3) contained in polyarylate resin (PA). The second content is adjusted by changing the amount (unit: mole) of compound (DC-2) added relative to the total amount (unit: mole) of compounds (DC-2) and (DC-4) added. The second content corresponds to the molar fraction (unit: mole%) of repeating unit (2) in the total amount of repeating units (2) and (4) contained in polyarylate resin (PA). The third content is adjusted by changing the amount (unit: mole) of compound (BP-3) added relative to the total amount (unit: mole) of compounds (BP-1) and (BP-3) added. The third content corresponds to the molar fraction (unit: mol%) of the repeating unit (3) in the total amount of the repeating units (1) and (3) contained in the polyarylate resin (PA). The fourth content is adjusted by changing the amount (unit: mol) of the compound (DC-4) added relative to the total amount (unit: mol) of the compounds (DC-2) and (DC-4) added. The fourth content corresponds to the molar fraction (unit: mol%) of the repeating unit (4) in the total amount of the repeating units (2) and (4) contained in the polyarylate resin (PA).

[0130] Bisphenols may be derivatized to aromatic diacetates for use. Dicarboxylic acids may be derivatized for use. Examples of dicarboxylic acid derivatives include dicarboxylic acid dichlorides, dicarboxylic acid dimethyl esters, dicarboxylic acid diethyl esters, and dicarboxylic acid anhydrides. Dicarboxylic acid dichlorides are compounds in which two "-C(=O)-OH" groups of a dicarboxylic acid are each replaced with a "-C(=O)-Cl" group.

[0131] In the polycondensation of bisphenol and dicarboxylic acid, a terminal terminator may be added. Examples of the terminal terminator include 2,6-dimethylphenol and 1H,1H-perfluoro-1-heptanol. By using 2,6-dimethylphenol as the terminal terminator, a terminal group (T-DMP) is formed. By using 1H,1H-perfluoro-1-heptanol as the terminal terminator, a terminal group (T-PFH) is formed.

[0132] In the polycondensation of bisphenol and dicarboxylic acid, a base and / or a catalyst may be added. An example of the base is sodium hydroxide. An example of the catalyst is benzyltributylammonium chloride, ammonium chloride, ammonium bromide, quaternary ammonium salt, triethylamine, and trimethylamine.

[0133] The photosensitive layer (more specifically, each of the single-layer photosensitive layer, the charge generating layer, and the charge transport layer) may contain only one type of polyarylate resin (PA) as a binder resin, or may contain two or more types of polyarylate resin (PA). The photosensitive layer (more specifically, each of the single-layer photosensitive layer, the charge generating layer, and the charge transport layer) may contain only polyarylate resin (PA) as a binder resin, or may further contain a binder resin other than polyarylate resin (PA) (hereinafter, may be referred to as other binder resin).

[0134] Examples of other binder resins include thermoplastic resins (more specifically, polyarylate resins other than polyarylate resins (PA), polycarbonate resins, styrene-based resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, styrene-acrylic acid copolymers, acrylic copolymers, polyethylene resins, ethylene-vinyl acetate copolymers, chlorinated polyethylene resins, polyvinyl chloride resins, polypropylene resins, ionomers, vinyl chloride-vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyvinyl acetal resins, and polyether resins), thermosetting resins (more specifically, silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, and other crosslinkable thermosetting resins), and photocurable resins (more specifically, epoxy-acrylic acid-based resins, and urethane-acrylic acid-based copolymers).

[0135] (Electron transport agent) The electron transport material contains a compound represented by formula (10), (11), or (12) (hereinafter, these may be referred to as electron transport materials (10), (11), and (12), respectively). When the first photosensitive layer contains the electron transport materials (10) to (12) in addition to the first hole transport material, the second hole transport material, and the polyarylate resin (PA), crystallization of the photosensitive layer is suppressed, and the sensitivity characteristics of the photoreceptor are improved.

[0136] [ka]

[0137] In formula (10), Q 5A and Q 5B each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. 6A and Q 6Beach independently represents an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms; m1 and m2 each independently represent an integer of 0 to 4.

[0138] When m1 is an integer between 2 and 4, multiple Q 6A may be the same or different. When m2 represents an integer of 2 to 4, multiple Q 6B may be the same as or different from each other.

[0139] In formula (10), Q 5A and Q 5B each independently preferably represents an alkyl group having 1 to 8 carbon atoms, more preferably represents an alkyl group having 1 to 6 carbon atoms, and further preferably represents a 1,1-dimethylpropyl group.

[0140] In formula (11), Q 7 and Q 8 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. 9 represents an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. m3 represents an integer of 0 to 4.

[0141] When m3 is an integer between 2 and 4, multiple Q 9 may be the same as or different from each other.

[0142] In formula (11), Q 7 and Q 8 each independently preferably represents an alkyl group having 1 to 8 carbon atoms, more preferably represents an alkyl group having 1 to 6 carbon atoms, and further preferably represents a tert-butyl group.

[0143] In formula (12), Q 10 and Q 11Each independently represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. 12 represents a halogen atom or a hydrogen atom.

[0144] In formula (12), Q 10 and Q 11 Each of Q independently preferably represents an alkyl group having 1 to 6 carbon atoms, and more preferably represents a tert-butyl group. 12 preferably represents a halogen atom, and more preferably represents a chlorine atom.

[0145] In order to improve the crack resistance of the photoreceptor and suppress crystallization, the electron transport agent (10) is preferably a compound represented by formula (E-1). For the same reason, the electron transport agent (11) is preferably a compound represented by formula (E-2). For the same reason, the electron transport agent (12) is preferably a compound represented by formula (E-3). Hereinafter, the compounds represented by formulas (E-1), (E-2), and (E-3) may be referred to as electron transport agents (E-1), (E-2), and (E-3), respectively.

[0146] [ka]

[0147] The content of the electron transport agent per 100 parts by mass of the binder resin (SL) and the content of the electron transport agent per 100 parts by mass of the binder resin (CG) are each preferably 5 parts by mass or more and 150 parts by mass or less, more preferably 10 parts by mass or more and 100 parts by mass or less, and even more preferably 30 parts by mass or more and 70 parts by mass or less.

[0148] The first photosensitive layer may contain only one type of electron transport agent, or may contain two or more types of electron transport agents. The first photosensitive layer may further contain an electron transport agent other than the electron transport agents (10), (11), and (12) (hereinafter, may be referred to as other electron transport agents). Examples of other electron transport agents include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride. Examples of quinone compounds include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds.

[0149] (Charge generating material) Examples of the charge generating agent include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, indigo pigments, azulenium pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g., selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon), pyrylium pigments, anthanthrone pigments, triphenylmethane pigments, threne pigments, toluidine pigments, pyrazoline pigments, and quinacridone pigments. The single-layer photosensitive layer and the charge generating layer may each contain only one type of charge generating agent, or may contain two or more types of charge generating agents.

[0150] Phthalocyanine pigments are pigments having a phthalocyanine structure. Examples of phthalocyanine pigments include metal-free phthalocyanine and metal phthalocyanine. Examples of metal phthalocyanine include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. Metal-free phthalocyanine is represented by formula (CGM-1). Titanyl phthalocyanine is represented by formula (CGM-2).

[0151] [ka]

[0152] [ka]

[0153] The phthalocyanine pigment may be crystalline or non-crystalline. Examples of the metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter, may be referred to as X-type metal-free phthalocyanine). Examples of the titanyl phthalocyanine crystals include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter, may be referred to as α-type, β-type, and Y-type titanyl phthalocyanine, respectively).

[0154] For example, in a digital optical image forming apparatus (for example, a laser beam printer or a facsimile using a light source such as a semiconductor laser), it is preferable to use a photoreceptor having sensitivity in a wavelength region of 700 nm or more. As the charge generating agent, a phthalocyanine pigment is preferable because it has a high quantum yield in a wavelength region of 700 nm or more, a metal-free phthalocyanine or titanyl phthalocyanine is more preferable, titanyl phthalocyanine is further preferable, and Y-type titanyl phthalocyanine is particularly preferable.

[0155] The Y-type titanyl phthalocyanine has a main peak at, for example, 27.2° of Bragg angle (2θ±0.2°) in the CuKα characteristic X-ray diffraction spectrum. The main peak in the CuKα characteristic X-ray diffraction spectrum is the peak having the first or second largest intensity in the range of Bragg angle (2θ±0.2°) from 3° to 40°. The Y-type titanyl phthalocyanine does not have a peak at 26.2° in the CuKα characteristic X-ray diffraction spectrum.

[0156] The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, a sample (titanyl phthalocyanine) is loaded into a sample holder of an X-ray diffractometer (for example, Rigaku Corporation's "RINT (registered trademark) 1100"), and the X-ray diffraction spectrum is measured under the conditions of an X-ray tube Cu, a tube voltage of 40 kV, a tube current of 30 mA, and a wavelength of CuKα characteristic X-ray of 1.542 Å. The measurement range (2θ) is, for example, 3° to 40° (start angle 3°, stop angle 40°), and the scanning speed is, for example, 10° / min. The main peak is determined from the obtained X-ray diffraction spectrum, and the Bragg angle of the main peak is read.

[0157] The content of the charge generating agent per 100 parts by mass of the binder resin (SL) and the content of the charge generating agent per 100 parts by mass of the binder resin (CG) are preferably 0.1 parts by mass or more and 50 parts by mass or less, and more preferably 0.5 parts by mass or more and 5 parts by mass or less.

[0158] (Additives) Examples of additives include ultraviolet absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, donors, surfactants, plasticizers, sensitizers, electron acceptor compounds, and leveling agents.

[0159] (Conductive substrate) The conductive substrate is not particularly limited, and at least the surface portion may be made of a material having electrical conductivity. An example of the conductive substrate is a conductive substrate made of a material having electrical conductivity. Another example of the conductive substrate is a conductive substrate coated with a material having electrical conductivity. Examples of the conductive material include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass. Among these conductive materials, aluminum and aluminum alloys are preferred because they have good charge transfer from the photosensitive layer to the conductive substrate.

[0160] The shape of the conductive substrate is appropriately selected according to the structure of the image forming apparatus. The shape of the conductive substrate may be, for example, a sheet or a drum. The thickness of the conductive substrate is appropriately selected according to the shape of the conductive substrate.

[0161] (Middle class) The intermediate layer (undercoat layer) contains, for example, inorganic particles and a resin (intermediate layer resin) used in the intermediate layer. The presence of the intermediate layer makes it possible to maintain an insulating state sufficient to suppress leakage, while facilitating the flow of current generated when the photoreceptor is exposed to light, thereby suppressing an increase in resistance.

[0162] Inorganic particles include, for example, particles of metals (e.g., aluminum, iron, and copper), particles of metal oxides (e.g., titanium oxide, alumina, zirconium oxide, tin oxide, and zinc oxide), and particles of non-metal oxides (e.g., silica).

[0163] Examples of the resin for the intermediate layer are the same as the examples of other binder resins already described. In order to form the intermediate layer and the photosensitive layer well, it is preferable that the resin for the intermediate layer is different from the binder resin contained in the photosensitive layer. The intermediate layer may contain an additive. Examples of the additive contained in the intermediate layer are the same as the examples of the additive contained in the photosensitive layer.

[0164] (Photoreceptor manufacturing method) As a method for producing a photoreceptor, an example of a method for producing a single-layer type photoreceptor and an example of a method for producing a positively charged multi-layer type photoreceptor will be described.

[0165] The method for producing a single-layer photoreceptor includes, for example, a single-layer photosensitive layer forming step. In the single-layer photosensitive layer forming step, a coating liquid for forming a single-layer photosensitive layer (hereinafter, sometimes referred to as a coating liquid for a single-layer photosensitive layer) is prepared. The coating liquid for a single-layer photosensitive layer is applied onto a conductive substrate. Then, at least a part of the solvent contained in the applied coating liquid for a single-layer photosensitive layer is removed to form a single-layer photosensitive layer. The coating liquid for a single-layer photosensitive layer contains, for example, a charge generating agent, a binder resin (SL), an electron transport agent, a hole transport agent (SL), and a solvent. The coating liquid for a single-layer photosensitive layer is prepared by dissolving or dispersing a charge generating agent, a binder resin (SL), an electron transport agent, and a hole transport agent (SL) in a solvent. The coating liquid for a single-layer photosensitive layer may further contain an additive as necessary.

[0166] The method for producing a positively charged multi-layer photoreceptor includes, for example, a charge transport layer forming step and a charge generation layer forming step.

[0167] In the charge transport layer forming step, the coating liquid for the charge transport layer is applied onto a conductive substrate. Then, at least a part of the solvent contained in the applied coating liquid for the charge transport layer is removed to form a charge transport layer. The coating liquid for the charge transport layer contains a hole transport agent (CT), a binder resin (CT), and a solvent. The coating liquid for the charge transport layer can be prepared by dissolving or dispersing the hole transport agent (CT) and the binder resin (CT) in a solvent. The coating liquid for the charge transport layer may further contain an additive, if necessary.

[0168] In the charge generation layer forming step, the charge generation layer coating liquid is applied onto the charge transport layer. Then, at least a part of the solvent contained in the applied charge generation layer coating liquid is removed to form the charge generation layer. The charge generation layer coating liquid contains, for example, a charge generation agent, a binder resin (CG), an electron transport agent, a hole transport agent (CG), and a solvent. The charge generation layer coating liquid is prepared by dissolving or dispersing the charge generation agent, the binder resin (CG), the electron transport agent, and the hole transport agent (CG) in a solvent. The charge generation layer coating liquid may further contain an additive as necessary.

[0169] The solvent contained in the coating liquid for the single-layer photosensitive layer, the coating liquid for the charge generating layer, and the coating liquid for the charge transport layer (hereinafter, these may be collectively referred to as coating liquids) is not particularly limited as long as it can dissolve or disperse each component contained in the coating liquid. Examples of the solvent include alcohol (more specifically, methanol, ethanol, isopropanol, butanol, etc.), aliphatic hydrocarbons (more specifically, n-hexane, octane, cyclohexane, etc.), aromatic hydrocarbons (more specifically, benzene, toluene, xylene, etc.), halogenated hydrocarbons (more specifically, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, etc.), ethers (more specifically, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc.), ketones (more specifically, acetone, methyl ethyl ketone, cyclohexanone, etc.), esters (more specifically, ethyl acetate, methyl acetate, etc.), dimethylformaldehyde, dimethylformamide, and dimethylsulfoxide.

[0170] The solvent contained in the coating liquid for the charge transport layer is preferably different from the solvent contained in the coating liquid for the charge generation layer, because when the coating liquid for the charge generation layer is applied onto the charge transport layer, it is preferable that the charge transport layer is not dissolved in the solvent of the coating liquid for the charge generation layer.

[0171] The coating liquid is prepared by mixing the respective components and dispersing them in a solvent. For example, a bead mill, a roll mill, a ball mill, an attritor, a paint shaker, or an ultrasonic disperser can be used for mixing or dispersing.

[0172] The method for applying the coating liquid is not particularly limited as long as the coating liquid can be uniformly applied, and examples of the coating method include dip coating, spray coating, spin coating, and bar coating.

[0173] Methods for removing at least a part of the solvent contained in the coating liquid include, for example, heating, reducing pressure, or a combination of heating and reducing pressure. More specifically, a method for heat treatment (hot air drying) using a high-temperature dryer or a reduced-pressure dryer can be mentioned. The temperature for the heat treatment is, for example, 40°C or higher and 150°C or lower. The time for the heat treatment is, for example, 3 minutes or higher and 120 minutes or lower.

[0174] The method for producing a photoreceptor may further include one or both of a step of forming an intermediate layer and a step of forming a protective layer, if necessary. The step of forming an intermediate layer and the step of forming a protective layer can be appropriately selected from known methods.

[0175] <Second embodiment: Image forming apparatus> An image forming apparatus according to a second embodiment of the present invention will be described below. A tandem type color image forming apparatus will be described as an example with reference to Fig. 7. Fig. 7 is a cross-sectional view showing an example of an image forming apparatus.

[0176] 7 includes image forming units 40a, 40b, 40c, and 40d, a transfer belt 50, and a fixing device 54. Hereinafter, when there is no need to distinguish between the image forming units 40a, 40b, 40c, and 40d, each of them will be referred to as an image forming unit 40.

[0177] The image forming unit 40 includes an image carrier 30, a charging device 42, an exposure device 44, a developing device 46, and a transfer device 48. The image carrier 30 is the photoreceptor of the first embodiment (specifically, the single-layer photoreceptor 1 and the positively charged multilayer photoreceptor 10).

[0178] As already described, the photoreceptor of the first embodiment can satisfactorily form the photosensitive layer 3, can suppress crystallization of the photosensitive layer 3, and has excellent crack resistance and sensitivity characteristics of the photosensitive layer 3. Therefore, by providing the photoreceptor of the first embodiment as the image carrier 30, the image forming apparatus 100 can suppress image defects caused by crystallization and cracks of the photosensitive layer 3, and can form high-quality images due to the excellent sensitivity characteristics.

[0179] An image carrier 30 is provided at the center of the image forming unit 40. The image carrier 30 is provided so as to be rotatable in the direction of the arrow (counterclockwise in FIG. 7). A charging device 42, an exposure device 44, a developing device 46, and a transfer device 48 are provided around the image carrier 30 in this order from the upstream side in the rotation direction of the image carrier 30.

[0180] A plurality of color (for example, four colors: black, cyan, magenta, and yellow) toner images are sequentially superimposed on the recording medium P on the transfer belt 50 by each of the image forming units 40a to 40d.

[0181] The charging device 42 positively charges the surface (e.g., the peripheral surface) of the image carrier 30. In both cases where the image carrier 30 is a single-layer type photoreceptor 1 and where the image carrier 30 is a positively charged multi-layer type photoreceptor 10, the surface of the image carrier 30 is positively charged. The charging device 42 is, for example, a charging roller.

[0182] The exposure device 44 irradiates the charged surface of the image carrier 30 with exposure light. That is, the exposure device 44 exposes the charged surface of the image carrier 30. As a result, an electrostatic latent image is formed on the surface of the image carrier 30. The electrostatic latent image is formed based on image data input to the image forming apparatus 100.

[0183] The developing device 46 supplies toner to the surface of the image carrier 30 and develops the electrostatic latent image into a toner image. The developing device 46 (for example, the surface of the developing device 46, more specifically, the peripheral surface of the developing device 46) is in contact with the surface of the image carrier 30. That is, the image forming apparatus 100 employs a contact development method. The developing device 46 is, for example, a developing roller. When the developer is a one-component developer, the developing device 46 supplies toner, which is a one-component developer, to the electrostatic latent image formed on the image carrier 30. When the developer is a two-component developer, the developing device 46 supplies toner, which is a toner and a carrier contained in the two-component developer, to the electrostatic latent image formed on the image carrier 30. In this way, the image carrier 30 carries the toner image.

[0184] The transfer belt 50 conveys the recording medium P between the image carrier 30 and the transfer device 48. The transfer belt 50 is an endless belt. The transfer belt 50 is provided rotatably in the direction of the arrow (clockwise in FIG. 7).

[0185] The transfer device 48 transfers the toner image developed by the developing device 46 from the surface of the image carrier 30 to a receiving body. The receiving body is a recording medium P. When the toner image is transferred, the image carrier 30 is in contact with the recording medium P. That is, the image forming apparatus 100 employs a direct transfer method. The transfer device 48 is, for example, a transfer roller.

[0186] The recording medium P onto which the toner image has been transferred by the transfer device 48 is transported by the transfer belt 50 to the fixing device 54. The fixing device 54 is, for example, a heating roller and / or a pressure roller. The unfixed toner image transferred by the transfer device 48 is heated and / or pressurized by the fixing device 54. The toner image is fixed to the recording medium P by heating and / or pressing the toner image. As a result, an image is formed on the recording medium P.

[0187] Although an example of an image forming apparatus has been described above, the image forming apparatus is not limited to the image forming apparatus 100 already described. Although the image forming apparatus 100 already described is a color image forming apparatus, the image forming apparatus may be a monochrome image forming apparatus. In this case, the image forming apparatus may have only one image forming unit, for example. Furthermore, although the image forming apparatus 100 already described employs a tandem system, the image forming apparatus may employ, for example, a rotary system. Although the charging roller has been described as an example of the charging device 42, the charging device may be a charging device other than a charging roller (for example, a scorotron charger, a charging brush, or a corotron charger). Although the image forming apparatus 100 already described employs a contact development system, the image forming apparatus may employ a non-contact development system. Although the image forming apparatus 100 already described employs a direct transfer system, the image forming apparatus may employ an intermediate transfer system. When the image forming apparatus employs an intermediate transfer system, the transferred body corresponds to an intermediate transfer belt. In the image forming apparatus, the image forming unit 40 described above does not include a cleaning member, but the image forming unit may further include a cleaning member (e.g., a cleaning blade). In addition, the image forming unit 40 described above does not include a static eliminator, but the image forming unit may further include a static eliminator.

[0188] <Third embodiment: Process cartridge> Next, with continued reference to FIG. 7, an example of a process cartridge according to a third embodiment of the present invention will be described. The process cartridge corresponds to each of the image forming units 40a to 40d. The process cartridge includes an image carrier 30. The image carrier 30 is the photoconductor of the first embodiment. As already described, the photoconductor of the first embodiment can form the photosensitive layer 3 well, can suppress crystallization of the photosensitive layer 3, and has excellent crack resistance and sensitivity characteristics of the photosensitive layer 3. Therefore, by including the photoconductor of the first embodiment as the image carrier 30, the process cartridge can suppress image defects caused by crystallization and cracks of the photosensitive layer 3, and can form high-quality images due to excellent sensitivity characteristics. In addition to the image carrier 30, the process cartridge further includes at least one selected from the group consisting of a charging device 42, an exposure device 44, a developing device 46, and a transfer device 48. The process cartridge may further include a cleaning member (not shown) and a charge removing device (not shown). The process cartridge is designed to be detachable from the image forming apparatus 100. Therefore, the process cartridge is easy to handle, and when the sensitivity characteristics of the image carrier 30 deteriorate, the process cartridge can be easily and quickly replaced including the image carrier 30. The process cartridge equipped with the photoconductor of the first embodiment has been described above with reference to FIG. EXAMPLES

[0189] <Preparation of Polyarylate Resins (R-1) to (R-7) and (R-10) to (R-23)> Polyarylate resins (R-1) to (R-7) according to the examples and polyarylate resins (R-10) to (R-23) according to the comparative examples were synthesized by the methods shown below. Hereinafter, "polyarylate resins (R-1) to (R-7) and (R-10) to (R-23)" may be referred to as "resins (R-1) to (R-7) and (R-10) to (R-23)", respectively. The compositions of resins (R-1) to (R-7) and (R-10) to (R-23) are shown in Tables 3 and 4 below. The resin (R-20) had the same repeating units in the same ratio as the resin used in Example 4 of Patent Document 1 (JP Patent Publication 10-20514 A).

[0190] [Table 3]

[0191] [Table 4]

[0192] In Tables 3 and 4, "BisCZ", "BisB", "BisC", "BisZ", "BisCE", "BisA", "DHPE", "DPEC", "TPC", and "IPC" respectively refer to compounds represented by the following formulas (BisCZ), (BisB), (BisC), (BisZ), (BisCE), (BisA), (DHPE), (DPEC), (TPC), and (IPC) (hereinafter, these may be referred to as compounds (BisCZ), (BisB), (BisC), (BisZ), (BisCE), (BisA), (DHPE), (DPEC), (TPC), and (IPC), respectively).

[0193] [ka]

[0194] Moreover, the meanings of the terms in Tables 3 and 4 are as follows: Monomer: Monomer used in the synthesis of polyarylate resin Resin: Polyarylate resin Bisphenol addition rate: The percentage (unit: %) of the amount of the corresponding bisphenol monomer (unit: mole) to the total amount (unit: mole) of bisphenol monomer added in the synthesis of polyarylate resin Dicarboxylic acid addition rate: The percentage (unit: %) of the amount (unit: mole) of the corresponding dicarboxylic acid monomer to the total amount (unit: mole) of dicarboxylic acid monomer added in the synthesis of polyarylate resin Unit: repeating unit. The repeating units shown in Tables 3 and 4 are formed from the corresponding monomers shown in Tables 3 and 4. Unit (BisC): A repeating unit derived from the compound (BisC) Unit (BisZ): A repeating unit derived from the compound (BisZ). Unit (BisCE): A repeating unit derived from the compound (BisCE) Unit (BisA): A repeating unit derived from the compound (BisA). Unit (IPC): Repeating unit derived from compound (IPC) DMP: 2,6-dimethylphenol PFH: 1H,1H-perfluoro-1-heptanol Molecular weight: viscosity average molecular weight -: No corresponding monomer is used Unmeasurable: The resin did not dissolve in the solvent used for viscosity and molecular weight measurement, and the viscosity average molecular weight could not be measured.

[0195] (Synthesis of resin (R-1)) A three-neck flask equipped with a thermometer, a three-way cock, and a dropping funnel was used as the reaction vessel. The monomer compound (BisCZ) (32.8 mmol), the monomer compound (DHPE) (8.2 mmol), the end terminator 2,6-dimethylphenol (0.413 mmol), sodium hydroxide (98 mmol), and benzyltributylammonium chloride (0.384 mmol) were placed in the reaction vessel. The air in the reaction vessel was replaced with argon gas. Water (300 mL) was added to the contents of the reaction vessel. The contents of the reaction vessel were stirred at 50° C. for 1 hour. The contents of the reaction vessel were cooled to 10° C. to obtain an alkaline aqueous solution SA.

[0196] Next, the dicarboxylic acid dichloride (20.8 mmol) of the monomer compound (DPEC) and the dicarboxylic acid dichloride (11.2 mmol) of the monomer compound (TPC) were dissolved in chloroform (150 mL), thereby obtaining a chloroform solution SB.

[0197] The chloroform solution SB was slowly dropped into the alkaline aqueous solution SA over 110 minutes using a dropping funnel. The contents of the reaction vessel were stirred for 4 hours while controlling the temperature (liquid temperature) of the contents of the reaction vessel to 15±5°C to allow the polymerization reaction to proceed. The upper layer (aqueous layer) of the contents of the reaction vessel was removed using a decant to obtain an organic layer. Next, ion-exchanged water (400 mL) was added to the Erlenmeyer flask. The obtained organic layer was further added to the Erlenmeyer flask. Chloroform (400 mL) and acetic acid (2 mL) were further added to the Erlenmeyer flask. The contents of the Erlenmeyer flask were stirred at room temperature (25°C) for 30 minutes. The upper layer (aqueous layer) of the contents of the Erlenmeyer flask was removed using a decant to obtain an organic layer. The obtained organic layer was washed with ion-exchanged water (1 L) using a separating funnel. Washing with ion-exchanged water was repeated five times to obtain a water-washed organic layer. Next, the water-washed organic layer was filtered to obtain a filtrate. The obtained filtrate was slowly dropped into methanol (1 L) to obtain a precipitate. The precipitate was collected by filtration and then vacuum-dried at 70° C. for 12 hours to obtain a resin (R-1).

[0198] (Synthesis of Resins (R-2) to (R-7) and (R-10) to (R-23)) Resins (R-2) to (R-7) and (R-10) to (R-23) were synthesized in the same manner as in the synthesis of resin (R-1), except that the monomers shown in Tables 3 and 4 were used at the addition rates shown in Tables 3 and 4. The amount of each bisphenol monomer added was set so that the total amount of bisphenol monomers was 41.0 millimoles and the bisphenol addition rate was shown in Tables 3 and 4. For example, in the synthesis of resin (R-5), the amount of compound (BisB) added was 32.8 millimoles (=41.0×80 / 100), and the amount of compound (DHPE) added was 8.2 millimoles (=41.0×20 / 100). The amount of each dicarboxylic acid monomer added was set so that the total amount of dicarboxylic acid monomers was 32.0 millimoles and the dicarboxylic acid addition rate was shown in Tables 3 and 4. For example, in the synthesis of resin (R-5), the amount of compound (DPEC) added was 16.0 mmol (=32.0×50 / 100), and the amount of compound (TPC) added was 16.0 mmol (=32.0×50 / 100).

[0199] The obtained resins (R-1) to (R-7) and (R-10) to (R-23) were analyzed using a proton nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd., 600 MHz). 1 H-NMR spectrum was measured. Deuterated chloroform was used as the solvent. Tetramethylsilane (TMS) was used as the internal standard sample. As a representative example of resins (R-1) to (R-7) and (R-10) to (R-23), 1 The H-NMR spectrum is shown in FIG. 1 It was confirmed that resin (R-1) was obtained from the chemical shifts read from the H-NMR spectrum. It was also confirmed that resins (R-2) to (R-7) and (R-10) to (R-23) were obtained by the same method.

[0200] <Measurement of Viscosity Average Molecular Weight> The viscosity average molecular weight of the resin was measured in accordance with JIS (Japanese Industrial Standards) K7252-1: 2016. The measured viscosity average molecular weights are shown in Tables 3 to 4.

[0201] <Polycarbonate resin (R-8)~(R-9)> Polycarbonate resins represented by formulas (R-8) to (R-9) were prepared as binder resins used in the manufacture of photoreceptors according to comparative examples. Hereinafter, the "polycarbonate resins represented by formulas (R-8) to (R-9)" may be referred to as "resins (R-8) to (R-9)", respectively. The viscosity average molecular weights of resins (R-8) and (R-9) were 65,000 and 58,000, respectively.

[0202] [ka]

[0203] <Preparation of hole transport agent> Samples (M-A1) to (M-A4), which are mixtures of hole transport agents (1) and (2), were synthesized by the method shown below. Samples (M-B1) to (M-B5) used in comparative examples were synthesized by the method shown below. The compositions of samples (M-A1) to (M-A4) and (M-B1) to (M-B5) are shown in Tables 5 to 10. In the explanation of the synthesis method of each sample shown below, the compounds represented by the following formulas (A-1) to (A-4), (B-1) to (B-2), and (C-1) may be referred to as compounds (A-1) to (A-4), (B-1) to (B-2), and (C-1), respectively.

[0204] [ka]

[0205] (Preparation of Sample (M-A1)) A sample (M-A1) was prepared according to the following reaction formula (ra).

[0206] [ka]

[0207] Specifically, tris(dibenzylideneacetone)dipalladium (0.0366 g, 0.040 mmol), 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl (0.0763 g, 0.016 mmol), and sodium tert-butoxide (9.669 g, 100.7 mmol) were placed in a 500 mL three-neck flask equipped with a distillation tube. The air in the flask was replaced with nitrogen gas by repeating degassing and replacing with nitrogen gas twice.

[0208] Next, 2-ethylaniline (compound (A-1), 8.45 g, 69.8 mmol), 4-chlorotoluene (compound (B-1), 10.13 g, 80.0 mmol), and xylene (45 g) were further added to the flask. The liquid in the flask was heated to 130°C so that the liquid would reflux. The liquid was heated while distilling off tert-butanol that had been generated during the temperature increase. While refluxing the liquid, the liquid was stirred at 130°C for 2 hours (corresponding to the first stirring). Next, the liquid in the flask was cooled to 50°C.

[0209] Next, sodium tert-butoxide (7.680 g, 80.0 mmol), 4,4″-dibro-p-terphenyl (compound (C-1), 11.60 g, 30.0 mmol), palladium (II) acetate (0.0168 g, 0.075 mmol), 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (0.1425 g, 0.299 mmol), and xylene (32 g) were further added to the liquid in the flask. The liquid was heated to 130° C. so that the liquid in the flask would reflux. The liquid was heated while distilling off tert-butanol generated during the temperature increase. While refluxing the liquid, the liquid was stirred at 130° C. for 3 hours (corresponding to the second stirring).

[0210] The liquid in the flask was then cooled to 90°C. The liquid in the flask at 90°C was filtered to remove insoluble matter, and a filtrate was obtained. The filtrate was treated with activated clay twice. The activated clay treatment was a process in which activated clay (Japan Activated Clay Co., Ltd. "SA-1", 8 g) was added to the filtrate, which was stirred at 110°C for 15 minutes, filtered again, and the filtrate was collected. The filtrate that had been treated with activated clay twice was concentrated under reduced pressure to obtain a concentrated solution. To the concentrated solution, an amount of isohexane (about 50 g) was added so that the concentrated solution became slightly cloudy, and then methanol (50 g) was added. The concentrated solution was cooled to 5°C, and the precipitated crystals were removed by filtration. Xylene (100 g) was added to the crystals, and the mixture was heated to 110°C, and the crystals were dissolved in the xylene to obtain a solution. The solution was treated with activated clay five times. The filtrate that had been treated with activated clay five times was concentrated under reduced pressure to obtain a concentrated solution. To the concentrated solution, isohexane was added in an amount (about 50 g) such that the concentrated solution became slightly cloudy, and then methanol (50 g) was added. The concentrated solution was cooled to 5°C, and the precipitated crystals were removed by filtration. The obtained crystals were dried in vacuum at 70°C for 24 hours to obtain sample (M-A1). Sample (M-A1) was a mixture containing a hole transport agent (HTM-1) and a hole transport agent (HTM-A). The yield of sample (M-A1) was 16.3 g. The yield of the hole transport agent (HTM-1) contained in sample (M-A1) relative to compound (C-1) was 84%.

[0211] (Preparation of Sample (M-A2)) Sample (M-A2) was obtained in the same manner as sample (M-A1), except that 69.8 mmol of compound (A-1) was replaced with 69.8 mmol of compound (A-2). Sample (M-A2) was a mixture containing hole transport agent (HTM-2) and hole transport agent (HTM-B).

[0212] (Preparation of Sample (M-A3)) Sample (M-A3) was obtained in the same manner as sample (M-A1), except that 69.8 mmol of compound (A-1) was replaced with 69.8 mmol of compound (A-3). Sample (M-A3) was a mixture containing hole transport agent (HTM-3) and hole transport agent (HTM-C).

[0213] (Preparation of Sample (M-A4)) Sample (M-A4) was obtained in the same manner as sample (M-A1), except that 69.8 mmol of compound (A-1) was changed to 69.8 mmol of compound (A-4), and 80.0 mmol of compound (B-1) was changed to 80.0 mmol of compound (B-2). Sample (M-A4) was a mixture containing hole transport agent (HTM-4) and hole transport agent (HTM-D).

[0214] (Preparation of Sample (M-B1)) Sample (M-A1) was purified by silica gel column chromatography using a mixed solvent of toluene and isohexane (volume ratio 50 / 50) as the developing solvent. In this way, a fraction containing the hole transport agent (HTM-1) was separated. The separated liquid (fraction) was concentrated under reduced pressure until it became slightly cloudy, to obtain a concentrated liquid. Isohexane and methanol were added to the concentrated liquid. The concentrated liquid was cooled to 5°C, and the precipitated crystals were removed by filtration to obtain sample (M-B1). Sample (M-B1) contained only the hole transport agent (HTM-1) and did not contain the hole transport agent (HTM-A).

[0215] (Preparation of Sample (M-B2)) Sample (M-B2) was obtained in the same manner as in the preparation of sample (M-B1), except that sample (M-A1) was changed to sample (M-A2). Sample (M-B2) contained only the hole transport agent (HTM-2) and did not contain the hole transport agent (HTM-B).

[0216] (Preparation of Sample (M-B3)) Sample (M-B3) was obtained in the same manner as in the preparation of sample (M-B1), except that sample (M-A1) was changed to sample (M-A3). Sample (M-B3) contained only the hole transport agent (HTM-3) and did not contain the hole transport agent (HTM-C).

[0217] (Preparation of Sample (M-B4)) Sample (M-B4) was obtained in the same manner as in the preparation of sample (M-B1), except that sample (M-A1) was changed to sample (M-A4). Sample (M-B4) contained only the hole transport agent (HTM-4) and did not contain the hole transport agent (HTM-D).

[0218] (Preparation of Sample (M-B5)) Sample (M-A1) was purified by silica gel column chromatography using a mixed solvent of toluene and isohexane (volume ratio 50 / 50) as the developing solvent. In this way, a fraction containing the hole transport agent (HTM-A) was separated. The separated liquid (fraction) was concentrated under reduced pressure until it became slightly cloudy, to obtain a concentrated liquid. Isohexane and methanol were added to the concentrated liquid. The concentrated liquid was cooled to 5°C, and the precipitated crystals were removed by filtration to obtain sample (M-B5). Sample (M-B5) contained only the hole transport agent (HTM-A) and did not contain the hole transport agent (HTM-1).

[0219] (Measurement of the Content of Hole Transport Agent (1)) For each sample prepared, the content of hole transport agent (1) relative to the total mass of hole transport agent (1) and hole transport agent (2) was measured. As the content of hole transport agent (1), the contents of hole transport agents (HTM-1) to (HTM-4) included in formula (1) were measured. The measurement method was as follows.

[0220] 2.0 mg of the sample (more specifically, each of the samples (M-A1) to (M-A4) and (M-B1) to (M-B5)) was dissolved in 670 mg of tetrahydrofuran to obtain a tetrahydrofuran solution. The tetrahydrofuran used did not contain a stabilizer. The obtained tetrahydrofuran solution was analyzed by high performance liquid chromatography (HPLC). Specifically, the tetrahydrofuran solution of the sample was analyzed using the following analytical device and analytical conditions to obtain an HPLC chart. The content of the hole transport agent (1) in the sample was determined from the peak area of ​​the hole transport agent (1) in the HPLC chart. The content of the hole transport agent (2) in the sample was determined from the peak area of ​​the hole transport agent (2) in the HPLC chart. The content of the hole transport agent (1) was calculated from the determined contents of the hole transport agent (1) and the hole transport agent (2). The calculation results are shown in the "Content" column of Table 3.

[0221] (Analysis equipment and analysis conditions) -Analytical equipment: "LaChrom ELITE" manufactured by Hitachi High-Tech Corporation Detection wavelength: 254nm Column: GL Sciences Inertsil (registered trademark) ODS-3 (inner diameter: 4.6 mm, length: 250 mm) Column temperature: 40℃ Developing solvent: Acetonitrile ·Flow rate: 1mL / min Sample injection volume: 1μL

[0222] <Manufacturing of single-layer photoreceptor> (Production of single-layer photoreceptor (A-1)) 2 parts by mass of Y-type titanyl phthalocyanine as a charge generating agent, 70 parts by mass of sample (M-A1) as a hole transport agent (SL) (corresponding to 67.6 parts by mass of hole transport agent (HTM-1) and 2.5 parts by mass of hole transport agent (HTM-A)), 40 parts by mass of electron transport agent (E-1), 90 parts by mass of resin (R-1) as a binder resin (SL), and 500 parts by mass of tetrahydrofuran as a solvent were mixed for 20 minutes using a rod-shaped ultrasonic oscillator to obtain a dispersion. The dispersion was filtered using a filter with a mesh size of 5 μm to obtain a coating liquid for a single-layer type photosensitive layer. The coating liquid for a single-layer type photosensitive layer was applied onto a conductive substrate (aluminum drum-shaped support) by a dip coating method, and the coating was dried with hot air at 120 ° C. for 50 minutes. In this way, a single-layer type photosensitive layer (film thickness 30 μm) was formed on the conductive substrate to obtain a single-layer type photoreceptor (A-1). In the single-layer type photoreceptor (A-1), a single-layer type photosensitive layer was provided directly on the conductive substrate.

[0223] (Production of Single-Layer Photoreceptors (A-2) to (A-14) and (B-1) to (B-26)) Each of the single-layer photoreceptors (A-2) to (A-14) and (B-1) to (B-26) was manufactured by the same method as that for manufacturing the single-layer photoreceptor (A-1), except that the binder resin (SL), hole transport material (SL), and electron transport material shown in Tables 5 to 7 were used. The amount of the sample hole transport material (SL) added was 70 parts by mass in the manufacture of each single-layer photoreceptor. The amount of the first hole transport material added (unit: parts by mass) is calculated from the formula "amount of the first hole transport material added = 70 x content of the first hole transport material / 100". The amount of the second hole transport material added (unit: parts by mass) is calculated from the formula "amount of the second hole transport material added = 70 x (100 - content of the first hole transport material) / 100".

[0224] <Manufacture of positively charged laminated photoreceptor> (Manufacture of positively charged laminated photoreceptor (C-1)) First, a charge transport layer was formed. In detail, 100 parts by mass of sample (M-A1) as a hole transport agent (CT) (corresponding to 96.5 parts by mass of hole transport agent (HTM-1) and 3.5 parts by mass of hole transport agent (HTM-A)), 100 parts by mass of resin (R-1) as a binder resin (CT), and 500 parts by mass of tetrahydrofuran as a solvent were mixed for 20 minutes using a rod-shaped ultrasonic oscillator to obtain a dispersion liquid. The dispersion liquid was filtered using a filter with a mesh size of 5 μm to obtain a coating liquid for a charge transport layer. The coating liquid for a charge transport layer was applied onto a conductive substrate (aluminum drum-shaped support) by a dip coating method, and dried with hot air at 120 ° C. for 50 minutes. In this way, a charge transport layer (film thickness 15 μm) was formed on the conductive substrate.

[0225] Next, a charge generation layer was formed. In detail, 2 parts by mass of Y-type titanyl phthalocyanine as a charge generation agent, 70 parts by mass of sample (M-A1) as a hole transport agent (CG) (corresponding to 67.6 parts by mass of hole transport agent (HTM-1) and 2.5 parts by mass of hole transport agent (HTM-A)), 40 parts by mass of electron transport agent (E-1), 90 parts by mass of resin (R-1) as a binder resin (CG), and 500 parts by mass of 1,2-dichloroethane as a solvent were mixed for 20 minutes using a rod-shaped ultrasonic oscillator to obtain a dispersion liquid. The dispersion liquid was filtered using a filter with a mesh size of 5 μm to obtain a coating liquid for a charge generation layer. The coating liquid for a charge generation layer was applied on the formed charge transport layer by a dip coating method, and the mixture was dried with hot air at 120° C. for 50 minutes. In this way, a charge generation layer (film thickness 15 μm) was formed on the charge transport layer to obtain a positively charged laminated photoreceptor (C-1). In the positively charged laminated photoreceptor (C-1), a charge transport layer was provided directly on the conductive substrate, and a charge generation layer was provided directly on the charge transport layer.

[0226] (Manufacture of positively charged laminated photoreceptors (C-2) to (C-14) and (D-1) to (D-26)) Positively charged multi-layer photoreceptors (C-2) to (C-14) and (D-1) to (D-26) were manufactured by the same method as that for manufacturing the positively charged multi-layer photoreceptor (C-1), except that the binder resin (CG), hole transport agent (CG), and electron transport agent shown in Tables 8 to 10 were used. The amount of the sample hole transport agent (CG) added was 70 parts by mass in the manufacture of each positively charged multi-layer photoreceptor. The amount of the first hole transport agent added (unit: parts by mass) is calculated from the formula "amount of the first hole transport agent added = 70 x content of the first hole transport agent / 100". The amount of the second hole transport agent added (unit: parts by mass) is calculated from the formula "amount of the second hole transport agent added = 70 x (100 - content of the first hole transport agent) / 100".

[0227] <Evaluation of sensitivity characteristics> The sensitivity characteristics of the photoconductors (more specifically, single-layer photoconductors and positively charged multi-layer photoconductors) were evaluated in an environment with a temperature of 23°C and a relative humidity of 50%RH. The surface of the photoconductor was charged to +750V using a drum sensitivity tester (manufactured by Gentec Co., Ltd.). Then, monochromatic light (wavelength: 780 nm, half-width: 20 nm, light energy: 1.0 μJ / cm 2 ) was extracted from the light of a halogen lamp using a bandpass filter and irradiated onto the surface of the photoconductor. The surface potential of the photoconductor was measured 0.5 seconds after the end of the monochromatic light irradiation. The measured surface potential was taken as the post-exposure potential V of the photoconductor. L (Unit: +V) The potential after exposure V L The sensitivity characteristics of the photoconductor were evaluated according to the following criteria: L The results of the evaluation are shown in Tables 5 to 10. (Evaluation criteria for sensitivity characteristics) A: Post-exposure potential V L However, it is less than +130V. B: Post-exposure potential V L However, it is greater than +130V and less than +140V. C: Post-exposure potential V L However, it is +140V or more.

[0228] <Evaluation of crack resistance> The environment for evaluating the crack resistance of the photoreceptor (more specifically, the single-layer type photoreceptor and the positively charged multilayer type photoreceptor) was an environment with a temperature of 23° C. and a relative humidity of 50% RH. The region of the photoreceptor up to 40 mm from the bottom end was immersed in an isoparaffinic hydrocarbon solvent ("Isopar L" manufactured by ExxonMobil) for 24 hours. After immersion for 24 hours, the number of cracks that had occurred on the surface of the photoreceptor was confirmed. The crack resistance was evaluated based on the number of cracks according to the following criteria. The evaluation results are shown in Tables 5 to 10. (Crack resistance evaluation criteria) A: The number of cracks is 20 or less. B: The number of cracks is 21 or more and 100 or less. C: The number of cracks is 101 or more.

[0229] <Evaluation of crystallization inhibition> The entire photosensitive layer of the photoreceptor (more specifically, the single-layer type photoreceptor and the positively charged multi-layer type photoreceptor) was observed with the naked eye to confirm the presence or absence of crystallized areas in the photosensitive layer. From the confirmation results, it was evaluated whether or not crystallization of the photoreceptor was suppressed according to the following criteria. The evaluation results are shown in Tables 5 to 10. (Criteria for evaluation of crystallization inhibition) A: No crystallized areas were observed. B: Crystallized areas were observed.

[0230] <Overall rating> A photoconductor that was rated A in all of the evaluations of sensitivity characteristics, crack resistance, and crystallization inhibition was determined to pass. A photoconductor that was not rated A in at least one of the evaluations of sensitivity characteristics, crack resistance, and crystallization inhibition was determined to fail.

[0231] Tables 5 to 10 are shown below. The meanings of the terms used in Tables 5 to 10 are as follows. ·HTM: Hole transport material ·HTM(1): First hole transport material ·HTM(2): Second hole transport material HTM(1) content: the content of hole transport material (1) relative to the total mass of hole transport material (1) and hole transport material (2) (unit: wt%, i.e. mass%) ETM: Electron transport material Resin: Binder resin Coating solution preparation impossible: The resin did not dissolve in the solvent of the coating solution for the first photosensitive layer, so the first photosensitive layer could not be formed and the photoreceptor could not be evaluated. Hardness: Vickers hardness ·V L : Potential after exposure Crack: Evaluation result of crack resistance of photoconductor Crystallization: Evaluation results of crystallization suppression of photoreceptor -: The relevant ingredient is not included. E-4: A compound represented by the following formula (E-4):

[0232] [ka]

[0233] [Table 5]

[0234] [Table 6]

[0235] [Table 7]

[0236] [Table 8]

[0237] [Table 9]

[0238] [Table 10]

[0239] As can be seen from the formulas (R-8) to (R-9), the resins (R-8) to (R-9) were not included in the polyarylate resin (PA). As can be seen from Table 4, the resins (R-10) to (R-23) were not included in the polyarylate resin (PA). For this reason, as shown in Tables 7 and 10, the resins (R-11), (R-13), (R-15), (R-20), and (R-23) were not dissolved in the solvent for preparing the coating solution for the first photosensitive layer, and the first photosensitive layer (more specifically, the single-layer type photosensitive layer and the charge generating layer) could not be formed. Furthermore, as shown in Tables 6 to 7 and Tables 9 to 10, at least one of the evaluations of sensitivity characteristics, crack resistance, and crystallization inhibition of the single-layer photoreceptors (B-1) to (B-3), (B-15), (B-17), (B-19) to (B-22), and (B-24) to (B-25), and the positively charged multilayer photoreceptors (D-1) to (D-3), (D-15), (D-17), (D-19) to (D-22), and (D-24) to (D-25) was not A.

[0240] As shown in Tables 6 and 9, the first photosensitive layer of the single-layer photoreceptors (B-4) to (B-11) and the positively charged multi-layer photoreceptors (D-4) to (D-11) did not contain a second hole transport agent. Therefore, at least one of the evaluations of the sensitivity characteristics, the crack resistance, and the crystallization inhibition of the single-layer photoreceptors (B-4) to (B-11) and the positively charged multi-layer photoreceptors (D-4) to (D-11) was not A.

[0241] As shown in Tables 6 and 9, the first photosensitive layer of the single-layer photoreceptor (B-12) and the positively charged multi-layer photoreceptor (D-12) did not contain a first hole transport agent. Therefore, the single-layer photoreceptor (B-12) and the positively charged multi-layer photoreceptor (D-12) were rated C for sensitivity characteristics and crack resistance, and rated B for crystallization inhibition.

[0242] As shown in Tables 6 and 9, the first photosensitive layer of the single-layer photoreceptor (B-13) and the positive-charged multi-layer photoreceptor (D-13) contained an electron transport agent (E-4), but the electron transport agent (E-4) was not a compound included in formulas (10), (11), and (12). For this reason, the single-layer photoreceptor (B-13) and the positive-charged multi-layer photoreceptor (D-13) were evaluated as B in terms of sensitivity characteristics and crystallization inhibition.

[0243] On the other hand, as can be seen from Table 3, the resins (R-1) to (R-7) were resins included in the polyarylate resin (PA). As can be seen from Tables 5 and 8, the single-layer photoreceptors (A-1) to (A-14) and the positively charged multilayer photoreceptors (C-1) to (C-14) had the following configurations. The first photosensitive layer contained a charge generating agent, a binder resin, an electron transport agent, a first hole transport agent, and a second hole transport agent. The binder resin contained a polyarylate resin (PA) (more specifically, resins (R-1) to (R-7)). The electron transport agent contained an electron transport agent (10), (11), or (12) (more specifically, electron transport agents (E-1) to (E-3)). The first hole transport material contained a first hole transport material (21) (more specifically, first hole transport materials (HTM-1) to (HTM-4)). The second hole transport material contained a second hole transport material (22) (more specifically, second hole transport materials (HTM-A) to (HTM-D)). For this reason, the single-layer photoreceptors (A-1) to (A-14) and the positively charged multilayer photoreceptors (C-1) to (C-14) were all evaluated as A in terms of sensitivity characteristics, crack resistance, and crystallization inhibition.

[0244] From the above, it has been shown that the photoconductors of the present invention, including the single-layer type photoconductors (A-1) to (A-14) and the positively charged multi-layer type photoconductors (C-1) to (C-14), can form a good photosensitive layer, have excellent sensitivity characteristics and crack resistance, and can suppress crystallization of the photosensitive layer. It is also determined that the process cartridge and image forming apparatus of the present invention equipped with such photoconductors can form high-quality images with excellent sensitivity characteristics and can suppress the occurrence of image defects caused by cracks and crystallization of the photosensitive layer. [Industrial Applicability]

[0245] The photoconductor and the process cartridge according to the present invention can be used in an image forming apparatus, and the image forming apparatus according to the present invention can be used to form an image on a recording medium.

Claims

1. A conductive substrate and at least one photosensitive layer are provided. The at least one photosensitive layer includes a first photosensitive layer, and the first photosensitive layer is provided on the outermost surface side of the at least one photosensitive layer; the first photosensitive layer contains a charge generating material, a binder resin, an electron transport material, and a hole transport material; The binder resin includes a polyarylate resin, The polyarylate resin has repeating units represented by formulas (1), (2), (3), and (4), a third content, which is the content of the repeating unit represented by the formula (3) relative to the total number of repeating units represented by the formulas (1) and (3), is greater than 0% and less than 50%, a fourth content, which is a content of the repeating unit represented by the formula (4) relative to the total number of the repeating units represented by the formulas (2) and (4), is 35% or more and less than 70%, The electron transport agent includes a compound represented by formula (10), (11), or (12), The hole transport material includes a first hole transport material and a second hole transport material, The first hole transport agent includes a compound represented by formula (21), The second hole transport agent comprises a compound represented by formula (22). 【Chemistry 1】 (In the above formula (1), R 1 and R 2 represents a methyl group, and X represents a divalent group represented by formula (X1), or R 1 and R 2 represents a hydrogen atom, and X represents a divalent group represented by formula (X2). 【Chemistry 2】 (In the formulas (X1) and (X2), * represents a bond.) 【Chemistry 3】 (In the formula (10), Q 5A and Q. 5B each independently represents a hydrogen atom, an alkyl group having from 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having from 1 to 8 carbon atoms; Q 6A and Q. 6B each independently represents an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms; m 1 and m 2 each independently represents an integer of 0 to 4, In the formula (11), Q 7 and Q. 8 each independently represents a hydrogen atom, an alkyl group having from 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having from 1 to 8 carbon atoms; Q 9 represents an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms; m 3 represents an integer of 0 to 4, In the formula (12), Q 10 and Q. 11 each independently represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom; Q 12 represents a halogen atom or a hydrogen atom. 【Chemistry 4】 (In the above formula (21), R 1A , R 2A , R 3A , R 4A , R 5A , R 6A , R 7A , R 8A , R 9A , and R 10A each independently represents a hydrogen atom, an alkyl group having from 1 to 8 carbon atoms, an alkoxy group having from 1 to 8 carbon atoms, or an aryl group having from 6 to 14 carbon atoms, R in the formula (21) 1B and R in the formula (22) 1C is R in the formula (21). 1A represents the same group as R in the formula (21) 2B and R in the formula (22) 2C is R in the formula (21). 2A represents the same group as R in the formula (21) 3B and R in the formula (22) 3C is R in the formula (21). 3A represents the same group as R in the formula (21) 4B and R in the formula (22) 4C is R in the formula (21). 4A represents the same group as R in the formula (21) 5B and R in the formula (22) 5C is R in the formula (21). 5A represents the same group as R in the formula (21) 6B and R in the formula (22) 6C and R 6D is R in the formula (21). 6A represents the same group as R in the formula (21) 7B and R in the formula (22) 7C and R 7D is R in the formula (21). 7A represents the same group as R in the formula (21) 8B and R in the formula (22) 8C and R 8D is R in the formula (21). 8A represents the same group as R in the formula (21) 9B and R in the formula (22) 9C and R 9D is R in the formula (21). 9A represents the same group as R in the formula (21) 10B and R in the formula (22) 10C and R 10D is R in the formula (21). 10A represents the same group as In the formula (21), Y represents a divalent group represented by the formula (Y2). 【Chemistry 5】

2. In the formula (1), R 1 and R 2 2. The electrophotographic photoreceptor according to claim 1, wherein X represents a divalent group represented by formula (X1).

3. In the formula (1), R 1 and R 2 represents a methyl group, and X represents a divalent group represented by formula (X1), The electrophotographic photoreceptor according to claim 1 , wherein the fourth content is equal to or greater than 40% and less than 70%.

4. In the formula (1), R 1 and R 2 represents a methyl group, and X represents a divalent group represented by formula (X1), The electrophotographic photoreceptor according to claim 1 , wherein the third content is equal to or greater than 30% and less than 50%.

5. In the formula (1), R 1 and R 2 represents a methyl group, and X represents a divalent group represented by formula (X1), The electrophotographic photoreceptor according to claim 1 , wherein the polyarylate resin further has a terminal group having a halogen atom.

6. In the formula (1), R 1 and R 2 represents a hydrogen atom, and X represents a divalent group represented by formula (X2), The electrophotographic photoreceptor according to claim 1 , wherein the fourth content is equal to or greater than 35% and equal to or less than 45%.

7. a content of the repeating unit represented by the formula (1) relative to the total number of the repeating units represented by the formulas (1) and (3) is a first content; a content of the repeating unit represented by the formula (2) relative to the total number of the repeating units represented by the formulas (2) and (4) is a second content; the first content rate is a value different from the second content rate and a value different from the fourth content rate, 2. The electrophotographic photoreceptor according to claim 1, wherein the third content is a value different from the second content and a value different from the fourth content.

8. The electrophotographic photoreceptor according to claim 1 , wherein the third content is greater than 30% and less than 50%.

9. The electrophotographic photoreceptor according to claim 1 , wherein the polyarylate resin does not have a repeating unit represented by formula (5). 【Chemistry 6】

10. The compound represented by the formula (10) is a compound represented by the formula (E-1): The compound represented by the formula (11) is a compound represented by the formula (E-2):

2. The electrophotographic photoreceptor according to claim 1, wherein the compound represented by formula (12) is a compound represented by formula (E-3). 【Chemistry 7】

11. The compound represented by the formula (21) is a compound represented by the formula (HTM-1), and the compound represented by the formula (22) is a compound represented by the formula (HTM-A), The compound represented by the formula (21) is a compound represented by the formula (HTM-2), and the compound represented by the formula (22) is a compound represented by the formula (HTM-B), The compound represented by formula (21) is a compound represented by formula (HTM-3), and the compound represented by formula (22) is a compound represented by formula (HTM-C), or 2. The electrophotographic photoreceptor according to claim 1, wherein the compound represented by formula (21) is a compound represented by formula (HTM-4), and the compound represented by formula (22) is a compound represented by formula (HTM-D). 【Chemistry 8】

12. The electrophotographic photoreceptor according to claim 1 , wherein the photosensitive layer is a single-layer type photosensitive layer that is the first photosensitive layer.

13. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is a two-layer structure, the two photosensitive layers being a charge generating layer which is the first photosensitive layer, and a charge transport layer which is the second photosensitive layer.

14. At least one selected from the group consisting of a charging device, an exposure device, a developing device, and a transfer device; A process cartridge comprising the electrophotographic photoreceptor according to claim 1.

15. An image carrier; a charging device for charging the surface of the image carrier to a positive polarity; an exposure device that exposes the charged surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier; a developing device that supplies toner to the surface of the image carrier to develop the electrostatic latent image into a toner image; a transfer device that transfers the toner image from the image carrier to a transfer medium, The image forming apparatus, wherein the image bearing member is the electrophotographic photoreceptor according to claim 1 .

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