Polyarylate resin and electrophotographic photoreceptor

Abstract

To provide a polyarylate resin which is excellent in dissolubility in a solvent, and improves repeated sensitivity characteristics and abrasion resistance of a photoreceptor when contained in a photosensitive layer.SOLUTION: A polyarylate resin has repeating units (1), (2) and (4). The polyarylate resin further has a repeating unit (3), and has a percentage content of the repeating unit (3) to the total number of the repeating units (1) and (3) of 0 mol% or more and less than 50 mol% with respect to the total diol units.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a polyarylate resin and an electrophotographic photoreceptor.

Background Art

[0002] An electrophotographic photoreceptor is used as an image carrier in an electrophotographic image forming apparatus (for example, a printer or a multifunction peripheral). The electrophotographic photoreceptor includes a photosensitive layer. As the electrophotographic photoreceptor, for example, a single-layer electrophotographic photoreceptor and a laminated electrophotographic photoreceptor are used. The single-layer electrophotographic photoreceptor includes a single photosensitive layer having a charge generation function and a charge transport function. The laminated 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 whose surface layer contains a polyarylate resin obtained from a dicarboxylic acid component and a diphenol component represented by the following formula.

[0004]

Chemical Formula

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the electrophotographic photoreceptor described in Patent Document 1 is insufficient in terms of abrasion resistance. Further, it has been found by the studies of the present inventors that the electrophotographic photoreceptor described in Patent Document 1 is insufficient in terms of the solubility of the binder resin in a solvent and the sensitivity characteristics when charging and exposure are repeated.

[0007] The present invention has been made in view of the above problems, and its object is to provide a polyarylate resin that has excellent solubility in a solvent and, when contained in the photosensitive layer of an electrophotographic photoreceptor, improves the sensitivity characteristics of the electrophotographic photoreceptor and the abrasion resistance of the electrophotographic photoreceptor when charging and exposure are repeated. Hereinafter, the "sensitivity characteristics when charging and exposure are repeated" may be referred to as "repeated sensitivity characteristics". Another object of the present invention is to provide an electrophotographic photoreceptor that can form a photosensitive layer well and has excellent repeated sensitivity characteristics and abrasion resistance.

Means for Solving the Problems

[0008] The polyarylate resin of the present invention has repeating units represented by formulas (1), (2), and (4). The polyarylate resin further has a repeating unit represented by formula (3), and the content of the repeating unit represented by formula (3) with respect to the total number of the repeating units represented by formulas (1) and (3) is greater than 0% and less than 50%. Alternatively, the polyarylate resin does not have the repeating unit represented by formula (3).

[0009]

Chemical Formula

[0010] In the formula (1), R 1 and R 2 each independently represent a hydrogen atom or a methyl group, and X represents a divalent group represented by formula (X1) or (X2). In the formula (3), R 5 and R 6 each independently represent a hydrogen atom or a methyl group, and W represents a single bond or an oxygen atom.

[0011]

Chemical Formula

[0012] In the formula (X1), t represents an integer of 1 or more and 3 or less, and * represents a bond. In the formula (X2), R 3 and R 4 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and * represents a bond.

[0013] The electrophotographic photoreceptor of the present invention includes a conductive substrate and a photosensitive layer. The photosensitive layer contains a charge generating agent, a hole transporting agent, and a binder resin. The binder resin includes the above polyarylate resin.

Advantages of the Invention

[0014] The polyarylate resin of the present invention is excellent in solubility in a solvent, and can improve the repeated sensitivity characteristics and abrasion resistance of the electrophotographic photoreceptor when contained in the photosensitive layer. The electrophotographic photoreceptor of the present invention can form a photosensitive layer well and is excellent in repeated sensitivity characteristics and abrasion resistance.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present invention. Note that, for parts where the description is repetitive, the description may be omitted as appropriate, but the gist of the invention is not limited. Hereinafter, a "system" may be appended after the compound name to comprehensively refer to the compound and its derivatives. Also, when a "system" is appended after the compound name to represent a polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Further, "general formula" and "chemical formula" are collectively referred to as "formula". "Independently of each other" in the description of the formula means that the same group or different groups may be represented. Each component described in this specification may be used alone or in combination of two or more, unless otherwise specified.

[0017] First, the substituents used in this specification will be described. An alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 4 carbon atoms, and an alkyl group having 1 to 3 carbon atoms are each, unless otherwise specified, linear or branched and unsubstituted. Examples of the alkyl group having 1 to 8 carbon atoms include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-ethylpropyl group, 2-ethylpropyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group, 1-ethylbutyl group, 2-ethylbutyl group and 3-ethylbutyl group, linear and branched heptyl groups, and linear and branched octyl groups. Examples of the alkyl group having 1 to 6 carbon atoms, the alkyl group having 1 to 4 carbon atoms, and the alkyl group having 1 to 3 carbon atoms are each a group having the corresponding number of carbon atoms among the groups described as examples of the alkyl group having 1 to 8 carbon atoms.

[0018] A perfluoroalkyl group having 1 to 10 carbon atoms, a perfluoroalkyl group having 3 to 10 carbon atoms, a perfluoroalkyl group having 5 to 7 carbon atoms, and a perfluoroalkyl group having 6 carbon atoms are each, unless otherwise specified, linear or branched and unsubstituted. Examples of the perfluoroalkyl group having 1 to 10 carbon atoms include, for example, trifluoromethyl group, perfluoroethyl group, perfluoro-n-propyl group, perfluoroisopropyl group, perfluoro-n-butyl group, perfluoro-sec-butyl group, perfluoro-tert-butyl group, perfluoro-n-pentyl group, perfluoro-1-methylbutyl group, perfluoro-2-methylbutyl group, perfluoro-3-methylbutyl group, perfluoro-1-ethylpropyl group, perfluoro-2-ethylpropyl group, perfluoro-1,1-dimethylpropyl group, perfluoro-1,2-dimethylpropyl group, perfluoro-2,2-dimethylpropyl group, perfluoro-n-hexyl group, perfluoro-1-methylpentyl group, perfluoro-2-methylpentyl group, perfluoro-3-methylpentyl group, perfluoro-4-methylpentyl group, perfluoro-1,1-dimethylbutyl group, perfluoro-1,2-dimethylbutyl group, perfluoro-1,3-dimethylbutyl group, perfluoro-2,2-dimethylbutyl group, perfluoro-2,3-dimethylbutyl group, perfluoro-3,3-dimethylbutyl group, perfluoro-1,1,2-trimethylpropyl group, perfluoro-1,2,2-trimethylpropyl group, perfluoro-1-ethylbutyl group, perfluoro-2-ethylbutyl group, and perfluoro-3-ethylbutyl group, linear and branched perfluoroheptyl groups, linear and branched perfluorooctyl groups, linear and branched perfluorononyl groups, and linear and branched perfluorodecyl groups. Examples of the perfluoroalkyl group having 3 to 10 carbon atoms, the perfluoroalkyl group having 5 to 7 carbon atoms, and the perfluoroalkyl group having 6 carbon atoms are the groups having the corresponding number of carbon atoms among the groups described as examples of the perfluoroalkyl group having 1 to 10 carbon atoms.

[0019] An alkoxy group having 1 to 8 carbon atoms and an alkoxy group having 1 to 3 carbon atoms are each, unless otherwise specified, linear or branched and unsubstituted. 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-methylpentyloxy group, a 3-methylpentyloxy group, a 4-methylpentyloxy group, a 1,1-dimethylbutoxy group, a 1,2-dimethylbutoxy group, a 1,3-dimethylbutoxy group, a 2,2-dimethylbutoxy group, a 2,3-dimethylbutoxy group, a 3,3-dimethylbutoxy group, a 1,1,2-trimethylpropoxy group, a 1,2,2-trimethylpropoxy group, a 1-ethylbutoxy group, a 2-ethylbutoxy group, a 3-ethylbutoxy group, linear and branched heptyloxy groups, and linear and branched octyloxy groups. Examples of the alkoxy group having 1 to 3 carbon atoms are the groups having the corresponding number of carbon atoms among the groups described as examples of the alkoxy group having 1 to 8 carbon atoms.

[0020] A cycloalkane having 5 to 7 carbon atoms is unsubstituted unless otherwise specified. Examples of the cycloalkane having 5 to 7 carbon atoms include cyclopentane, cyclohexane, and cycloheptane. The substituents used in this specification have been described above.

[0021] <First Embodiment: Polyarylate Resin> The first embodiment of the present invention relates to a polyarylate resin. The polyarylate resin of the first embodiment has repeating units represented by formulas (1), (2), and (4). The polyarylate resin of the first embodiment further has a repeating unit represented by formula (3), and the content of the repeating unit represented by formula (3) with respect to the total number of the repeating units represented by formulas (1) and (3) is greater than 0% and less than 50%. Alternatively, the polyarylate resin of the first embodiment does not have a repeating unit represented by formula (3).

[0022]

Chemical formula

[0023] In formula (1), R 1 and R 2 each independently represent a hydrogen atom or a methyl group, and X represents a divalent group represented by formula (X1) or (X2). In formula (3), R 5 and R 6 each independently represent a hydrogen atom or a methyl group, and W represents a single bond or an oxygen atom.

[0024]

Chemical formula

[0025] In formula (X1), t represents an integer of 1 or more and 3 or less, and * represents a bond. In formula (X2), R 3 and R 4 each independently represent a hydrogen atom or an alkyl group having 1 or more and 4 or less carbon atoms, and * represents a bond.

[0026] Hereinafter, the repeating units represented by formulas (1), (2), (3), and (4) may be described as "repeating units (1), (2), (3), and (4)", respectively. Also, the content ratio of repeating unit (3) to the total number of repeating units (1) and (3) may be described as "content ratio (3)". Further, a polyarylate resin having repeating units (1), (2), and (4), further having repeating unit (3) and with content ratio (3) being greater than 0% and less than 50%, or not having repeating unit (3) may be described as "polyarylate resin (PA)".

[0027] Polyarylate resin (PA) essentially has repeating units (1), (2), and (4). Due to having such repeating units, polyarylate resin (PA) has excellent solubility in solvents, and when contained in the photosensitive layer, it can improve the repeated sensitivity characteristics and abrasion resistance of the electrophotographic photoreceptor (hereinafter sometimes referred to as the photoreceptor).

[0028] Polyarylate resin (PA) may not have repeating unit (3). However, in order to improve the repeated sensitivity characteristics of the photoreceptor when contained in the photosensitive layer, polyarylate resin (PA) preferably has repeating unit (3).

[0029] When polyarylate resin (PA) further has repeating unit (3), content ratio (3) is greater than 0% and less than 50%. Content ratio (3) corresponds to the percentage of the number N3 of repeating unit (3) to the total of the number N1 of repeating unit (1) and the number N3 of repeating unit (3) that polyarylate resin (PA) has (that is, 100×N3 / (N1 + N3)). When polyarylate resin (PA) has two or more types of repeating unit (1), the number N1 of repeating unit (1) is the total number of the two or more types of repeating unit (1). When polyarylate resin (PA) has two or more types of repeating unit (3), the number N3 of repeating unit (3) is the total number of the two or more types of repeating unit (3).

[0030] When the content ratio (3) is less than 50%, the solubility of the polyarylate resin (PA) in the solvent is improved. When the content ratio (3) is greater than 0%, that is, the content ratio (3) is not 0%, the repeated sensitivity characteristics of the photoreceptor when the polyarylate resin (PA) is contained in the photosensitive layer are improved. The content ratio (3) is preferably 1% or more, more preferably 5% or more, still more preferably 10% or more, and particularly preferably 20% or more. Also, the content ratio (3) is preferably 45% or less, more preferably 40% or less, and still more preferably 30% or less.

[0031] In order to further improve the solubility of the polyarylate resin (PA) in the solvent, it is preferable that the polyarylate resin (PA) has a repeating unit (3) and the content ratio (3) is greater than 0% and 30% or less.

[0032] The content ratio of the repeating unit (4) to the total number of the repeating units (2) and (4) is greater than 0% and less than 100%. The content ratio of the repeating unit (4) to the total number of the repeating units (2) and (4) may be referred to as "content ratio (4)". The content ratio (4) corresponds to the percentage of the number N4 of the repeating unit (4) to the total of the number N2 of the repeating unit (2) and the number N4 of the repeating unit (4) that the polyarylate resin (PA) has (that is, 100×N4 / (N2+N4)). Since the content ratio (4) is greater than 0%, that is, the content ratio (4) is not 0%, the polyarylate resin (PA) has the repeating unit (4). By having the repeating unit (4), the repeating sensitivity characteristics and the abrasion resistance of the photoreceptor when the polyarylate resin (PA) is contained in the photosensitive layer are improved. On the other hand, since the content ratio (4) is less than 100%, that is, the content ratio (4) is not 100%, the polyarylate resin (PA) has the repeating unit (2). By having the repeating unit (2), the repeating sensitivity characteristics of the photoreceptor when the polyarylate resin (PA) is contained in the photosensitive layer are improved. The content ratio (4) is preferably 1% or more, more preferably 10% or more, still more preferably 20% or more, even more preferably 30% or more, and particularly preferably 35% or more. Also, the content ratio (4) is preferably 99% or less, more preferably 80% or less, still more preferably 65% or less, even more preferably 50% or less.

[0033] The content ratios (3) and (4) can be calculated from the ratios of the peaks characteristic of each repeating unit in the 1 1H-NMR spectrum measured using a proton nuclear magnetic resonance spectrometer for the polyarylate resin (PA), and the obtained 1 1H-NMR spectrum.

[0034] In formula (1), it is preferable that R 1 and R 2 represent hydrogen atoms. Alternatively, in formula (1), it is preferable that R 1 and R 2 represent methyl groups.

[0035] In formula (X1), t preferably represents 2.

[0036] In formula (X2), R 3 and R 4 As the alkyl group having 1 to 4 carbon atoms represented by them, an alkyl group having 1 to 3 carbon atoms is preferable, and a methyl group or an ethyl group is more preferable.

[0037] In formula (X2), R 3 and R 4 preferably each independently represents an alkyl group having 1 to 4 carbon atoms. R 3 and R 4 more preferably each independently represents an alkyl group having 1 to 3 carbon atoms. R 3 and R 4 even more preferably each independently represents a methyl group or an ethyl group. R 3 represents a methyl group and R 4 represents an ethyl group, or R 3 represents a methyl group and R 4 represents a methyl group is particularly preferable.

[0038] The bond represented by * in formulas (X1) and (X2) is bonded to the carbon atom to which X in formula (1) is bonded.

[0039] In order to further improve the repeated sensitivity characteristics of the photoreceptor when the polyarylate resin (PA) is contained in the photosensitive layer, in formula (1), X represents a divalent group represented by formula (X1), and in formula (X1), t preferably represents 2.

[0040] In formula (3), R 5 and R 6 preferably represent hydrogen atoms. Alternatively, in formula (3), R 5 and R 6 preferably represent methyl groups.

[0041] Examples of the repeating unit (1) include repeating units represented by formulas (1-1), (1-2), (1-3), and (1-4) (hereinafter, each may be referred to as repeating unit (1-1), (1-2), (1-3), and (1-4)).

[0042]

Chemical formula

[0043] The repeating unit (1) preferably contains the repeating unit (1-1), (1-2), or (1-3). More preferably, the repeating unit (1) further contains the repeating unit (1-4) in addition to the repeating unit (1-1), (1-2), or (1-3). Even more preferably, the repeating unit (1) contains both the repeating unit (1-1) and (1-4).

[0044] The polyarylate resin (PA) preferably has at least one kind of repeating unit (1), more preferably has one or more and four or less kinds of repeating units (1), and even more preferably has one or two kinds of repeating units (1).

[0045] Examples of the repeating unit (3) include repeating units represented by formulas (3-1) and (3-2) (hereinafter, each may be referred to as repeating unit (3-1) and (3-2)).

[0046]

Chemical formula

[0047] The repeating unit (3) preferably contains the repeating unit (3-1) or (3-2).

[0048] The polyarylate resin (PA) preferably has at least one kind of repeating unit (3), more preferably has one or more and four or less kinds of repeating units (3), and even more preferably has one or two kinds of repeating units (3).

[0049] When the polyarylate resin (PA) has the repeating unit (3), it is preferable that the repeating unit (3) includes the repeating unit (3-1). When the polyarylate resin (PA) has the repeating unit (3), it is more preferable that the repeating unit (3) includes the repeating unit (3-1) and the repeating unit (1) includes the repeating unit (1-1). Further, when the polyarylate resin (PA) has the repeating unit (3), it is also more preferable that the repeating unit (3) includes the repeating unit (3-2) and the repeating unit (1) includes the repeating unit (1-1).

[0050] When the polyarylate resin (PA) does not have the repeating unit (3), it is preferable that the repeating unit (1) includes the repeating unit (1-1), (1-2), or (1-3). When the polyarylate resin (PA) does not have the repeating unit (3), it is more preferable that the repeating unit (1) includes the repeating unit (1-1), (1-2), or (1-3) and the repeating unit (1) further includes the repeating unit (1-4). When the polyarylate resin (PA) does not have the repeating unit (3), it is particularly preferable that the repeating unit (1) includes the repeating unit (1-1) and the repeating unit (1) further includes the repeating unit (1-4).

[0051] In order to further improve the repeated sensitivity characteristics of the photoreceptor when the polyarylate resin (PA) is contained in the photosensitive layer, it is preferable that the polyarylate resin (PA) does not have the repeating unit represented by the formula (5).

[0052]

Chemical formula

[0053] The polyarylate resin (PA) may have end groups. Examples of the end groups that the polyarylate resin (PA) has include end groups represented by formula (T-1) and (T-2). As the end group represented by formula (T-1), an end group represented by formula (T-DMP) (hereinafter sometimes referred to as end group (T-DMP)) is preferable. As the end group represented by formula (T-2), an end group represented by formula (T-PFH) (hereinafter sometimes referred to as end group (T-PFH)) is preferable.

[0054] [Chemical formula]

[0055] 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. R 11 preferably represents an alkyl group having 1 to 6 carbon atoms, more preferably represents an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a methyl group. p preferably represents an integer of 1 to 3, and more preferably represents 2.

[0056] 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. R 12 preferably represents an alkanediyl group having 1 to 3 carbon atoms, and more preferably represents a methylene group. Rf preferably represents a perfluoroalkyl group having 3 to 10 carbon atoms, more preferably represents a perfluoroalkyl group having 5 to 7 carbon atoms, and still more preferably represents a perfluoroalkyl group having 6 carbon atoms.

[0057] In formulas (T-1), (T-2), (T-DMP), and (T-PFH), * represents a bond. The bonds represented by * in formulas (T-1), (T-2), (T-DMP), and (T-PFH) are bonded to the repeating units derived from dicarboxylic acids (more specifically, repeating unit (2) or (4)) located at the terminals of the polyarylate resin (PA).

[0058] Preferable examples of the polyarylate resin (PA) include the polyarylate resins (PA-1) to (PA-6) shown in Table 1. The polyarylate resins (PA-1) to (PA-6) each have the repeating units shown in Table 1 as repeating units (1) to (4). The meanings of the terms in Table 1 and Table 2 described later are as follows. "Unit (1) to (4)" each represents "repeating unit (1) to (4)". "-" indicates "not having the corresponding repeating unit". "1-1 / 1-4" indicates "having both repeating units (1-1) and (1-4) as repeating unit (1)".

[0059]

Table 1

[0060] More preferable examples of the polyarylate resin (PA) include the polyarylate resins (PA-a) to (PA-l) shown in Table 2. The polyarylate resins (PA-a) to (PA-l) each have the repeating units shown in Table 2 as repeating units (1) to (4) and the terminal groups shown in Table 2.

[0061]

Table 2

[0062] In a 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. That is, the repeating unit (1) may be bonded to the repeating unit (2) or the repeating unit (4). Also, the repeating unit (3) may be bonded to the repeating unit (2) or the repeating unit (4). The number of repeating units derived from bisphenol is substantially the same as the number of repeating units derived from dicarboxylic acid, and satisfies the calculation 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.

[0063] The polyarylate resin (PA) may further have repeating units other than the repeating units (1) to (4) as repeating units. However, in order to improve the solubility in a solvent and the repeating sensitivity characteristics and abrasion resistance of the photoreceptor when contained in the photosensitive layer, the content of the repeating units (1) to (4) in the total number of repeating units of the polyarylate resin (PA) is preferably 90% or more, more preferably 95% or more, still 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.

[0064] The viscosity-average molecular weight of the polyarylate resin (PA) is preferably 10,000 or more, more preferably 30,000 or more, still more preferably 45,000 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 it 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 in accordance with JIS (Japanese Industrial Standards) K7252-1:2016.

[0065] Next, the manufacturing method of the polyarylate resin (PA) will be described. As a manufacturing method of the polyarylate resin (PA), for example, a method of polycondensing bisphenol for constituting a repeating unit derived from bisphenol and dicarboxylic acid for constituting a repeating unit derived from dicarboxylic acid can be mentioned. For polycondensation, known synthesis methods (for example, solution polymerization, melt polymerization, or interfacial polymerization) can be adopted.

[0066] Examples of bisphenol for constituting a repeating unit derived from bisphenol include compounds represented by formula (BP-1) and (BP-3) (hereinafter, each may be described as compound (BP-1) and (BP-3)). Examples of dicarboxylic acid for constituting a repeating unit derived from dicarboxylic acid include compounds represented by formula (DC-2) and (DC-4) (hereinafter, each may be described as compound (DC-2) and (DC-4)). R in formula (BP-1) 1 , R 2 , and X are synonymous with R 1 , R 2 , and X in formula (1). R in formula (BP-3) 5 , R 6and W, R in formula (3) 5 R 6 is synonymous with W and R.

[0067] [Chemical formula]

[0068] In the production of polyarylate resin (PA), the content (3) can be adjusted by changing the addition amount (unit: mol) of compound (BP - 3) relative to the total addition amount (unit: mol) of compounds (BP - 1) and (BP - 3). Also, the content (4) can be adjusted by changing the addition amount (unit: mol) of compound (DC - 4) relative to the total addition amount (unit: mol) of compounds (DC - 2) and (DC - 4).

[0069] Bisphenol may be used after being derivatized into aromatic diacetate. Dicarboxylic acid may be used after being derivatized. Examples of derivatives of dicarboxylic acid include dicarboxylic acid dichloride, dimethyl dicarboxylate, diethyl dicarboxylate, and dicarboxylic acid anhydride. Dicarboxylic acid dichloride is a compound in which two "-C(=O)-OH" groups of dicarboxylic acid are each substituted with "-C(=O)-Cl" groups.

[0070] In the polycondensation of bisphenol and dicarboxylic acid, a terminal stopper may be added. Examples of the terminal stopper include 2,6 - dimethylphenol and 1H,1H - perfluoro - 1 - heptanol. By using 2,6 - dimethylphenol as the terminal stopper, the terminal group (T - DMP) can be formed. By using 1H,1H - perfluoro - 1 - heptanol as the terminal stopper, the terminal group (T - PFH) can be formed.

[0071] In the polycondensation of bisphenol and dicarboxylic acid, one or both of a base and a catalyst may be added. Examples of the base include sodium hydroxide. Examples of the catalyst include benzyltributylammonium chloride, ammonium chloride, ammonium bromide, quaternary ammonium salts, triethylamine, and trimethylamine.

[0072] <Second Embodiment: Photoconductor> The second embodiment of the present invention relates to a photoconductor. The photoconductor of the second embodiment includes a conductive substrate and a photosensitive layer. The photosensitive layer contains a charge generator, a hole transport agent, and a binder resin. The photoconductor is, for example, a single-layer type electrophotographic photoconductor (hereinafter sometimes referred to as a single-layer type photoconductor), or a laminated type electrophotographic photoconductor (hereinafter sometimes referred to as a laminated type photoconductor).

[0073] (Laminated type photoconductor) Hereinafter, with reference to FIGS. 1 to 3, a laminated type photoconductor 1 which is an example of a photoconductor will be described. FIGS. 1 to 3 each show a partial cross-sectional view of the laminated type photoconductor 1.

[0074] As shown in FIG. 1, the laminated type photoconductor 1 includes, for example, a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 includes a charge generation layer 3a and a charge transport layer 3b. That is, the laminated type photoconductor 1 includes the charge generation layer 3a and the charge transport layer 3b as the photosensitive layer 3. The charge generation layer 3a is, for example, a single layer. The charge transport layer 3b is, for example, a single layer.

[0075] As shown in FIG. 1, the charge generation layer 3a may be provided on the conductive substrate 2, and the charge transport layer 3b may be provided on the charge generation layer 3a. Alternatively, as shown in FIG. 2, the charge transport layer 3b may be provided on the conductive substrate 2, and the charge generation layer 3a may be provided on the charge transport layer 3b.

[0076] As shown in FIG. 3, in addition to the conductive substrate 2 and the photosensitive layer 3, the layered photosensitive member 1 may further include an intermediate layer 4 (undercoat layer). The intermediate layer 4 is provided between the conductive substrate 2 and the photosensitive layer 3. As shown in FIGS. 1 and 2, in the layered photosensitive member 1, the photosensitive layer 3 may be provided directly on the conductive substrate 2. Alternatively, as shown in FIG. 3, in the layered photosensitive member 1, the photosensitive layer 3 may be provided on the conductive substrate 2 via the intermediate layer 4. When the layered photosensitive member 1 includes the intermediate layer 4, as shown in FIG. 3, the intermediate layer 4 may be provided on the conductive substrate 2, the charge generation layer 3a may be provided on the intermediate layer 4, and the charge transport layer 3b may be provided on the charge generation layer 3a. Alternatively, the intermediate layer 4 may be provided on the conductive substrate 2, the charge transport layer 3b may be provided on the intermediate layer 4, and the charge generation layer 3a may be provided on the charge transport layer 3b.

[0077] In addition to the conductive substrate 2 and the photosensitive layer 3, the layered photosensitive member 1 may further include a protective layer 5 (see FIG. 6). The protective layer 5 is provided on the photosensitive layer 3. As shown in FIGS. 1 to 3, the photosensitive layer 3 (for example, the charge transport layer 3b or the charge generation layer 3a) may be provided as the outermost surface layer of the layered photosensitive member 1. Alternatively, the protective layer 5 may be provided as the outermost surface layer of the layered photosensitive member 1.

[0078] As shown in FIG. 1, it is preferable that the photosensitive layer 3 (preferably the charge transport layer 3b) is provided as the outermost surface layer of the layered photosensitive member 1. It is more preferable that the charge transport layer 3b is a single layer and is provided as the outermost surface layer of the layered photosensitive member 1. By providing the charge transport layer 3b containing a polyarylate resin (PA) as the outermost surface layer, the wear resistance of the layered photosensitive member 1 is further improved.

[0079] The charge generation layer 3a contains a charge generating agent. The charge generation layer 3a may contain a base resin as needed. The charge generation layer 3a may contain an additive as needed. The thickness of the charge generation layer 3a is not particularly limited, but is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 3 μm or less.

[0080] The charge transport layer 3b contains a hole transport agent and a binder resin. The charge transport layer 3b may contain an additive as required. The thickness of the charge transport layer 3b is not particularly limited, but is preferably 2 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less. As described above, the laminated photoreceptor 1 has been described with reference to FIGS. 1 to 3.

[0081] (Single-layer photoreceptor) Next, with reference to FIGS. 4 to 6, a single-layer photoreceptor 10, which is an example of a photoreceptor, will be described. FIGS. 4 to 6 each show a partial cross-sectional view of the single-layer photoreceptor 10.

[0082] As shown in FIG. 4, the single-layer photoreceptor 10 includes, for example, a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 provided in the single-layer photoreceptor 10 is a single layer. Hereinafter, the "single-layer photosensitive layer 3" may be referred to as the "single-layer photosensitive layer 3c".

[0083] As shown in FIG. 5, the single-layer photoreceptor 10 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2 and the single-layer photosensitive layer 3c. The intermediate layer 4 is provided between the conductive substrate 2 and the single-layer photosensitive layer 3c. As shown in FIG. 4, the single-layer photosensitive layer 3c may be provided directly on the conductive substrate 2. Alternatively, as shown in FIG. 5, the single-layer photosensitive layer 3c may be provided on the conductive substrate 2 via the intermediate layer 4.

[0084] As shown in FIG. 6, the single-layer photoreceptor 10 may further include a protective layer 5 in addition to the conductive substrate 2 and the single-layer photosensitive layer 3c. The protective layer 5 is provided on the single-layer photosensitive layer 3c. As shown in FIGS. 4 and 5, the single-layer photosensitive layer 3c may be provided as the outermost surface layer of the single-layer photoreceptor 10. Alternatively, as shown in FIG. 6, the protective layer 5 may be provided as the outermost surface layer of the single-layer photoreceptor 10.

[0085] As shown in FIGS. 4 and 5, it is preferable that the photosensitive layer 3 (more specifically, the single-layer photosensitive layer 3c) be provided as the outermost surface layer of the single-layer photoreceptor 10. By providing the single-layer photosensitive layer 3c containing a polyarylate resin (PA) as the outermost surface layer, the wear resistance of the single-layer photoreceptor 10 is further improved.

[0086] The single-layer photosensitive layer 3c contains a charge generator, a hole transport agent, and a binder resin. The single-layer photosensitive layer 3c may further contain an electron transport agent as needed. The single-layer photosensitive layer 3c may contain additives as needed.

[0087] The thickness of the single-layer photosensitive layer 3c is not particularly limited, but is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less. The single-layer photoreceptor 10 has been described above with reference to FIGS. 4 to 6.

[0088] (Binder Resin) The binder resin includes the polyarylate resin (PA) described in the first embodiment. By using a polyarylate resin (PA) excellent in solubility in a solvent, the photosensitive layer of the photoreceptor can be formed well. Further, since the photosensitive layer contains the polyarylate resin (PA), the repeated sensitivity characteristics and wear resistance of the photoreceptor are improved.

[0089] The photosensitive layer may contain only one type of polyarylate resin (PA) as the binder resin, or may contain two or more types of polyarylate resins (PA). Further, the photosensitive layer may contain only the polyarylate resin (PA) as the binder resin, or may further contain a binder resin other than the polyarylate resin (PA) (hereinafter sometimes referred to as other binder resins). Examples of other binder resins include thermoplastic resins (more specifically, polyarylate resins other than polyarylate resin (PA), polycarbonate resins, styrene 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, phenol 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).

[0090] (Hole transport agent) Examples of the hole transporting agent include, for example, triphenylamine derivatives, diamine derivatives (for example, N,N,N’,N’-tetraphenylbenzidine derivatives, N,N,N’,N’-tetraphenylphenylenediamine derivatives, N,N,N’,N’-tetraphenylnaphthylenediamine derivatives, N,N,N’,N’-tetraphenylphenanthrylene diamine derivatives, and di(aminophenylethenyl)benzene derivatives), oxadiazole compounds (for example, 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole), styryl compounds (for example, 9-(4-diethylaminostyryl)anthracene), carbazole compounds (for example, polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (for example, 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. The photosensitive layer may contain only one type of hole transporting agent or may contain two or more types of hole transporting agents.

[0091] Preferable examples of the hole transporting agent include compounds represented by formulas (20), (21), and (22) (hereinafter, each may be described as hole transporting agent (20), (21), and (22)). By containing the hole transporting agent (20), (21), or (22) together with the polyarylate resin (PA) in the photosensitive layer, the photosensitive layer can be formed more favorably, and the repetitive sensitivity characteristics and abrasion resistance of the photoreceptor are further improved.

[0092]

Chemical formula

[0093] In formula (20), R 21 and R 22 each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. R 23 , R 24 , R 25 , R26 , R 27 , R 28 , and R 29 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms. R 25 , R 26 , R 27 , R 28 , and R 29 Two adjacent ones of them may be bonded to form a ring. a1 and a2 each independently represent an integer of 0 or more and 5 or less.

[0094] In formula (20), when a1 represents an integer of 2 or more and 5 or less, a plurality of R 21 may represent the same group as each other, or may represent different groups. When a2 represents an integer of 2 or more and 5 or less, a plurality of R 22 may represent the same group as each other, or may represent different groups.

[0095] In formula (20), R 21 and R 22 each preferably independently represents an alkyl group having 1 to 8 carbon atoms, more preferably represents an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a methyl group.

[0096] In formula (20), R 23 and R 24 each preferably independently represents a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms, or a hydrogen atom. As the phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms represented by R 23 and R 24 , a phenyl group substituted with an alkyl group having 1 to 8 carbon atoms is preferable, a phenyl group substituted with an alkyl group having 1 to 3 carbon atoms is more preferable, a methylphenyl group is still more preferable, and a 4-methylphenyl group is particularly preferable.

[0097] In formula (20), R 25 to R 29Each independently preferably represents a hydrogen atom or an alkoxy group having 1 to 8 carbon atoms. R 25 ~R 29 The alkoxy group having 1 to 8 carbon atoms represented by is preferably an alkoxy group having 1 to 3 carbon atoms, more preferably a methoxy group or an ethoxy group. R 25 ~R 29 When two adjacent ones of form a ring by bonding to each other, the ring and the phenyl group to which R 25 ~R 29 is bonded condense to form a bicyclic condensed ring group. In this case, the condensation site of the ring and the phenyl group may contain a double bond. R 25 ~R 29 When two adjacent ones of form a ring, such a ring is preferably a cycloalkane having 5 to 7 carbon atoms, more preferably cyclohexane.

[0098] In formula (20), a1 and a2 each independently preferably represent 0 or 1.

[0099] In formula (21), R 31 、R 32 、R 33 、R 34 、R 35 、and R 36 each independently represent an alkyl group having 1 to 8 carbon atoms or a phenyl group. R 37 and R 38 each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group. b1, b2, b3, and b4 each independently represent an integer of 0 or more and 5 or less. b5 and b6 each independently represent an integer of 0 or more and 4 or less. d and e each independently represent 0 or 1.

[0100] In formula (21), when b1 represents an integer of 2 or more and 5 or less, the plurality of R 31 may represent the same group as each other or different groups. When b2 represents an integer of 2 or more and 5 or less, the plurality of R 32 may represent the same group as each other or different groups. When b3 represents an integer of 2 or more and 5 or less, the plurality of R33 may represent the same group as each other or different groups. When b4 represents an integer of 2 or more and 5 or less, a plurality of R 34 may represent the same group as each other or different groups. When b5 represents an integer of 2 or more and 4 or less, a plurality of R 35 may represent the same group as each other or different groups. When b6 represents an integer of 2 or more and 4 or less, a plurality of R 36 may represent the same group as each other or different groups.

[0101] In formula (21), R 31 ~R 36 each preferably independently represents an alkyl group having 1 to 8 carbon atoms, more preferably represents an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a methyl group or an ethyl group. R 37 and R 38 preferably represent a hydrogen atom. b1, b2, b3, and b4 each preferably independently represent an integer of 0 or more and 2 or less. b5 and b6 preferably represent 0.

[0102] In formula (22), R 41 , R 42 , R 43 , R 44 , R 45 , and R 46 each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. f1, f2, f4, and f5 each independently represent an integer of 0 or more and 5 or less. f3 and f6 each independently represent an integer of 0 or more and 4 or less.

[0103] In formula (22), when f1 represents an integer of 2 or more and 5 or less, a plurality of R 41 may represent the same group as each other or different groups. When f2 represents an integer of 2 or more and 5 or less, a plurality of R 42 may represent the same group as each other or different groups. When f4 represents an integer of 2 or more and 5 or less, a plurality of R 44may represent the same group as each other or different groups. When f5 represents an integer of 2 or more and 5 or less, a plurality of R 45 may represent the same group as each other or different groups. When f3 represents an integer of 2 or more and 4 or less, a plurality of R 43 may represent the same group as each other or different groups. When f6 represents an integer of 2 or more and 4 or less, a plurality of R 46 may represent the same group as each other or different groups.

[0104] In formula (22), R 41 ~R 46 each independently preferably represents an alkyl group having 1 to 8 carbon atoms, more preferably represents an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a methyl group or an ethyl group. f1, f2, f4, and f5 each independently preferably represent an integer of 0 or more and 2 or less. f3 and f6 preferably represent 0. R 44 R 45 and R 46 The diphenylaminophenylvinyl group having is preferably bonded to the para position of the phenyl group with respect to the diphenylaminophenylvinyl group having R 41 R 42 and R 43 More preferred examples of the hole transporting agent include compounds represented by formulas (HTM-1) to (HTM-6) (hereinafter, each may be described as hole transporting agent (HTM-1) to (HTM-6)).

[0105]

[0106]

Chemical formula

[0107]

Chemical formula

[0108] ​When the photoreceptor is a laminated photoreceptor, the content of the hole transport agent is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 20 parts by mass or more and 100 parts by mass or less, and still more preferably 40 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the binder resin. When the photoreceptor is a single-layer photoreceptor, the content of the hole transport agent is preferably 50 parts by mass or more and 200 parts by mass or less, and more preferably 50 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the binder resin.

[0109] (Charge generating agent) Examples of the charge generating agent include phthalocyanine-based pigments, perylene-based pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, indigo pigments, azulenium pigments, cyanine pigments, inorganic photoconductive materials (e.g., selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon) powders, pyrylium pigments, ansanthrone-based pigments, triphenylmethane-based pigments, threne-based pigments, toluidine-based pigments, pyrazoline-based pigments, and quinacridone-based pigments. The photosensitive layer may contain only one type of charge generating agent or two or more types of charge generating agents.

[0110] The phthalocyanine-based pigment is a pigment having a phthalocyanine structure. Examples of the phthalocyanine-based pigment include metal-free phthalocyanine and metal phthalocyanine. Examples of the metal phthalocyanine include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. The metal-free phthalocyanine is represented by the formula (CGM-1). The titanyl phthalocyanine is represented by the formula (CGM-2).

[0111] [Chemical formula]

[0112] [Chemical formula]

[0113] The phthalocyanine-based pigment may be crystalline or amorphous. Examples of the crystal of metal-free phthalocyanine include, for example, the X-type crystal of metal-free phthalocyanine (hereinafter sometimes referred to as X-type metal-free phthalocyanine). Examples of the crystal of titanyl phthalocyanine include, for example, the α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter sometimes referred to as α-type, β-type, and Y-type titanyl phthalocyanine, respectively).

[0114] 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. Since it has a high quantum yield in a wavelength region of 700 nm or more, as the charge generating agent, a phthalocyanine-based pigment is preferable, metal-free phthalocyanine or titanyl phthalocyanine is more preferable, titanyl phthalocyanine is still more preferable, and Y-type titanyl phthalocyanine is particularly preferable.

[0115] Y-type titanyl phthalocyanine has a main peak at, for example, 27.2° of the 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 a peak having the first or second largest intensity in the range where the Bragg angle (2θ ± 0.2°) is 3° or more and 40° or less. Y-type titanyl phthalocyanine does not have a peak at 26.2 °C in the CuKα characteristic X-ray diffraction spectrum.

[0116] The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, a sample (titanium phthalocyanine) is filled into the sample holder of an X-ray diffractometer (for example, "RINT (registered trademark) 1100" manufactured by Rigaku Corporation), 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 1.542 Å of the CuKα characteristic X-ray. The measurement range (2θ) is, for example, 3° or more and 40° or less (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.

[0117] When the photoreceptor is a laminated photoreceptor, the content of the charge generating agent is preferably 10 parts by mass or more and 300 parts by mass or less, more preferably 100 parts by mass or more and 200 parts by mass or less, based on 100 parts by mass of the base resin. When the photoreceptor is a single-layer photoreceptor, the content of the charge generating agent is preferably 0.1 parts by mass or more and 50 parts by mass or less, more preferably 0.5 parts by mass or more and 30 parts by mass or less, based on 100 parts by mass of the binder resin.

[0118] (Base resin) Examples of the base resin contained in the charge generation layer are the same as those of the other binder resins contained in the charge transport layer.

[0119] (Additive) Examples of the additive include, for example, an ultraviolet absorber, an antioxidant, a radical scavenger, a singlet quencher, a softening agent, a surface modifier, a filler, a thickening agent, a dispersion stabilizer, a wax, a donor, a surfactant, a plasticizer, a sensitizer, an electron acceptor compound, and a leveling agent. As the leveling agent, silicone oil is preferable, and silicone oil having a dimethylpolysiloxane structure is more preferable.

[0120] (Combination of materials) In order to form a photosensitive layer well and improve the repeated sensitivity characteristics and abrasion resistance of the photoreceptor, the combination of the hole transport agent and the binder resin is preferably each of combination Nos. a-1 to a-36 shown in Table 3, combination Nos. b-1 to b-72 shown in Table 4, and combination Nos. c-1 to c-60 shown in Table 5. For the same reason, the combination of the hole transport agent and the binder resin is preferably each of combination Nos. a-1 to a-36 shown in Table 3, combination Nos. b-1 to b-72 shown in Table 4, and combination Nos. c-1 to c-60 shown in Table 5, and the charge generating agent is preferably Y-type titanyl phthalocyanine. For the same reason, the combination of the hole transport agent and the binder resin is preferably each of combination Nos. a-1 to a-36 shown in Table 3, combination Nos. b-1 to b-72 shown in Table 4, and combination Nos. c-1 to c-60 shown in Table 5, and the additive contained in the charge transport layer is more preferably metaterphenyl. For the same reason, the combination of the hole transport agent and the binder resin is preferably each of combination Nos. a-1 to a-36 shown in Table 3, combination Nos. b-1 to b-72 shown in Table 4, and combination Nos. c-1 to c-60 shown in Table 5, and the additive contained in the charge transport layer is more preferably silicone oil (more specifically, silicone oil having a dimethylpolysiloxane structure). In Tables 3 to 5, "No." indicates "Combination No.", "HTM" indicates "hole transport agent", and "resin" indicates "polyarylate resin" which is the binder resin. Polyarylate resins A to J in Table 5 will be described in detail in the examples.

[0121]

Table 3

[0122]

Table 4

[0123]

Table 5

[0124] (Conductive substrate) The conductive substrate is not particularly limited as long as at least the surface portion is made of a conductive material. As an example of the conductive substrate, a conductive substrate made of a conductive material can be mentioned. As another example of the conductive substrate, a conductive substrate coated with a conductive material can be mentioned. 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 the transfer of charges from the photosensitive layer to the conductive substrate is good.

[0125] The shape of the conductive substrate is appropriately selected according to the structure of the image forming apparatus. Examples of the shape of the conductive substrate include a sheet shape and a drum shape. Also, the thickness of the conductive substrate is appropriately selected according to the shape of the conductive substrate.

[0126] (Intermediate layer) The intermediate layer (undercoat layer) contains, for example, inorganic particles and a resin used for the intermediate layer (resin for intermediate layer). By the presence of the intermediate layer, while maintaining an insulating state to the extent that leakage can be suppressed, the flow of current generated when the photoreceptor is exposed can be smoothed, and an increase in resistance can be suppressed.

[0127] Examples of the inorganic particles include particles of metals (such as aluminum, iron, and copper), particles of metal oxides (such as titanium oxide, alumina, zirconium oxide, tin oxide, and zinc oxide), and particles of non-metal oxides (such as silica).

[0128] Examples of the resin for intermediate layer are the same as the examples of the other binder resins already described. In order to form the intermediate layer and the photosensitive layer well, it is preferable that the resin for intermediate layer is different from the binder resin contained in the photosensitive layer. The intermediate layer may contain additives. Examples of the additives contained in the intermediate layer are the same as the examples of the additives contained in the photosensitive layer.

[0129] (Method for manufacturing a photoreceptor) As a method for manufacturing a photoreceptor, an example of a method for manufacturing a laminated photoreceptor and an example of a method for manufacturing a single-layer photoreceptor will be described.

[0130] The method for manufacturing a laminated photoreceptor includes, for example, a charge generation layer forming step and a charge transport layer forming step. In the charge generation layer forming step, first, a coating liquid for forming a charge generation layer (hereinafter sometimes referred to as a coating liquid for charge generation layer) is prepared. The coating liquid for charge generation layer is applied onto a conductive substrate. Next, at least a part of the solvent contained in the applied coating liquid for charge generation layer is removed to form a charge generation layer. The coating liquid for charge generation layer contains, for example, a charge generating agent, a base resin, and a solvent. Such a coating liquid for charge generation layer is prepared by dissolving or dispersing the charge generating agent and the base resin in the solvent. The coating liquid for charge generation layer may further contain an additive as needed.

[0131] In the charge transport layer forming step, first, a coating liquid for forming a charge transport layer (hereinafter sometimes referred to as a coating liquid for charge transport layer) is prepared. The coating liquid for charge transport layer is applied onto the charge generation layer. Next, at least a part of the solvent contained in the applied coating liquid for charge transport layer is removed to form a charge transport layer. The coating liquid for charge transport layer contains a hole transport agent, a binder resin, and a solvent. The coating liquid for charge transport layer can be prepared by dissolving or dispersing the hole transport agent and the binder resin in the solvent. The coating liquid for charge transport layer may further contain an additive as needed.

[0132] The manufacturing method of a single-layer photoreceptor includes, for example, a single-layer photosensitive layer forming step. In the single-layer photosensitive layer forming step, a coating solution for forming a single-layer photosensitive layer (hereinafter sometimes referred to as a coating solution for single-layer photosensitive layer) is prepared. The coating solution for single-layer photosensitive layer is applied onto a conductive substrate. Then, at least a part of the solvent contained in the applied coating solution for single-layer photosensitive layer is removed to form a single-layer photosensitive layer. The coating solution for single-layer photosensitive layer contains, for example, a charge generator, a hole transport agent, a binder resin, and a solvent. The coating solution for single-layer photosensitive layer is prepared by dissolving or dispersing a charge generator, a hole transport agent, and a binder resin in a solvent. The coating solution for single-layer photosensitive layer may further contain one or both of an electron transport agent and an additive as necessary.

[0133] The solvent contained in the coating solution for single-layer photosensitive layer, the coating solution for charge generation layer, and the coating solution for charge transport layer (hereinafter sometimes comprehensively referred to as coating solution) is not particularly limited as long as it can dissolve or disperse each component contained in the coating solution. Examples of the solvent include alcohols (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 dimethyl sulfoxide.

[0134] The solvent contained in the coating solution for charge transport layer is preferably different from the solvent contained in the coating solution for charge generation layer. This is because when the coating solution for charge transport layer is applied onto the charge generation layer, it is preferable that the charge generation layer is not dissolved in the solvent of the coating solution for charge transport layer.

[0135] The coating liquid is prepared by mixing each component and dispersing it in a solvent. For mixing or dispersing, for example, a bead mill, a roll mill, a ball mill, an attritor, a paint shaker, or an ultrasonic disperser can be used.

[0136] The method of applying the coating liquid is not particularly limited as long as it can uniformly apply the coating liquid. Examples of the coating method include a dip coating method, a spray coating method, a spin coating method, and a bar coating method.

[0137] Examples of the method for removing at least a part of the solvent contained in the coating liquid include heating, reduced pressure, or a combination of heating and reduced pressure. More specifically, a method of heat treatment (hot air drying) using a high-temperature dryer or a reduced-pressure dryer can be mentioned. The temperature of the heat treatment is, for example, 40°C or higher and 150°C or lower. The time of the heat treatment is, for example, 3 minutes or longer and 120 minutes or shorter.

[0138] Note that the method for manufacturing the photoreceptor may further include one or both of a step of forming an intermediate layer and a step of forming a protective layer as necessary. For the step of forming the intermediate layer and the step of forming the protective layer, known methods can be appropriately selected.

Examples

[0139] Hereinafter, the present invention will be described more specifically using examples. However, the present invention is not limited to the scope of the examples at all.

[0140] <Preparation of Polyarylate Resins A to O> The polyarylate resins A to J according to the examples and the polyarylate resins K to O according to the comparative examples were synthesized by the methods shown below. The compositions of the polyarylate resins A to O are shown in Table 6 below.

[0141]

Table 6

[0142] In Table 6, "BisCZ", "BisB", "BisC", "BisZ", "BP", "DHPE", "DPC", "14NACC", "26NACC", "DPEC", "TPC", and "IPC" each represent a compound represented by the following formulas (BisCZ), (BisB), (BisC), (BisZ), (BP), (DHPE), (DPC), (14NACC), (26NACC), (DPEC), (TPC), and (IPC) (hereinafter, each may be referred to as compound (BisCZ), (BisB), (BisC), (BisZ), (BP), (DHPE), (DPC), (14NACC), (26NACC), (DPEC), (TPC), and (IPC)).

[0143] [Chemical formula]

[0144] Also, the meanings of the terms in Table 6 are as follows. Monomer: The monomer used in the synthesis of the polyarylate resin Forming unit: The repeating unit formed from the corresponding monomer Resin: Polyarylate resin Bisphenol addition rate: The percentage (%) of the amount (unit: mol) of the corresponding bisphenol monomer with respect to the total amount (unit: mol) of the bisphenol monomer added in the synthesis of the polyarylate resin Dicarboxylic acid addition rate: The percentage (%) of the amount (unit: mol) of the corresponding dicarboxylic acid monomer with respect to the total amount (unit: mol) of the dicarboxylic acid monomer added in the synthesis of the polyarylate resin Molecular weight: Viscosity average molecular weight Unit: Repeating unit TPC / IPC: A mixture of compounds (TPC) and (IPC) with a molar ratio of 1 / 1 17.5 / 17.5 in the TPC / IPC column: The addition rate of compound (TPC) is 17.5% and the addition rate of compound (IPC) is 17.5% DMP: 2,6-Dimethylphenol PFH: 1H,1H-Perfluoro-1-heptanol

[0145] (Synthesis of Polyarylate Resin A) As a reaction vessel, a three-necked flask equipped with a thermometer, a three-way cock, and a dropping funnel was used. Into the reaction vessel were placed the monomer compound (BisCZ) (41.0 mmol), the end-capping agent 2,6-dimethylphenol (0.413 mmol), sodium hydroxide (98 mmol), and benzyltributylammonium chloride (0.384 mmol). 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 S-A.

[0146] Next, the dicarboxylic acid dichloride of the monomer compound (DPC) (16.0 mmol) and the dicarboxylic acid dichloride of the monomer compound (14NACC) (16.0 mmol) were dissolved in chloroform (150 mL). Thereby, a chloroform solution S-B was obtained.

[0147] To the alkaline aqueous solution S-A, the chloroform solution S-B was slowly added dropwise over 110 minutes using a dropping funnel. While adjusting the temperature (liquid temperature) of the contents of the reaction vessel to 15 ± 5 °C, the contents of the reaction vessel were stirred for 4 hours to allow the polymerization reaction to proceed. The upper layer (aqueous layer) of the contents of the reaction vessel was removed using a separatory funnel to obtain an organic layer. Next, ion-exchanged water (400 mL) was added to an 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 separatory funnel to obtain an organic layer. The obtained organic layer was washed with ion-exchanged water (1 L) using a separatory funnel. The washing with ion-exchanged water was repeated 5 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 added dropwise to methanol (1 L) to obtain a precipitate. The precipitate was taken out by filtration. The taken-out precipitate was vacuum dried at a temperature of 70 °C for 12 hours. As a result, polyarylate resin A was obtained.

[0148] (Synthesis of Polyarylate Resins B to O) Each of polyarylate resins B to O was synthesized in the same manner as the synthesis of polyarylate resin A, except that the monomers shown in Table 6 were used at the addition rates shown in Table 6. The addition amounts of the respective bisphenol monomers were set so that the total amount of the bisphenol monomers became 41.0 mmol and the bisphenol addition rate shown in Table 6 was obtained. For example, in the synthesis of polyarylate resin H, the addition amount of compound (BisCZ) was 32.8 mmol (= 41.0 × 80 / 100), and the addition amount of compound (DHPE) was 8.2 mmol (= 41.0 × 20 / 100). Also, the addition amounts of the respective dicarboxylic acid monomers were set so that the total amount of the dicarboxylic acid monomers became 32.0 mmol and the dicarboxylic acid addition rate shown in Table 6 was obtained. For example, in the synthesis of polyarylate resin H, the addition amount of compound (DPC) was 11.2 mmol (= 32.0 × 35 / 100), and the addition amount of compound (14NACC) was 20.8 mmol (= 32.0 × 65 / 100).

[0149] Using a proton nuclear magnetic resonance spectrometer (manufactured by JEOL Ltd., 600 MHz), the 1H-NMR spectra of the obtained polyarylate resins A to O were measured. Deuterated chloroform was used as the solvent. Tetramethylsilane (TMS) was used as the internal standard sample. As a representative example among the polyarylate resins A to N, the 1H-NMR spectrum of the polyarylate resin A is shown in Fig. 7. 1 From the chemical shifts read from the 1H-NMR spectrum, it was confirmed that the polyarylate resin A was obtained. For the polyarylate resins B to O, it was also confirmed that the polyarylate resins B to O were obtained by the same method. 1 The 1H-NMR spectrum of the polyarylate resin A is shown in Fig. 7. 1 From the chemical shifts read from the 1H-NMR spectrum, it was confirmed that the polyarylate resin A was obtained. For the polyarylate resins B to O, it was also confirmed that the polyarylate resins B to O were obtained by the same method.

[0150] <Preparation of Polyarylate Resin P> The polyarylate resin P according to the comparative example was prepared. The polyarylate resin P is represented by the following formula (P). The numbers attached to the right lower side of the repeating unit derived from bisphenol in the formula (P) indicate the content rate (unit: %) of the corresponding repeating unit derived from bisphenol with respect to the total number of repeating units derived from bisphenol contained in the polyarylate resin P. Also, the numbers attached to the right lower side of the repeating unit derived from dicarboxylic acid in the formula (P) indicate the content rate (unit: %) of the corresponding repeating unit derived from dicarboxylic acid with respect to the total number of repeating units derived from dicarboxylic acid contained in the polyarylate resin P. The polyarylate resin P had a terminal group derived from 2,6-dimethylphenol as a terminal group. The viscosity average molecular weight of the polyarylate resin P was 54,400.

[0151]

Chemical formula

[0152] <Measurement of Viscosity Average Molecular Weight> The viscosity average molecular weight of the polyarylate resin was measured according to JIS (Japanese Industrial Standard) K7252-1:2016. The measured viscosity average molecular weights are shown in Table 6.

[0153] <Manufacture of the laminated photoreceptor> (Manufacture of the laminated photoreceptor (A-1)) First, an intermediate layer was formed. Titanium oxide that had been surface-treated ("Prototype SMT-A" manufactured by Teika Corporation, number-average primary particle diameter 10 nm) was prepared. SMT-A was obtained by surface-treating titanium oxide with alumina and silica, and further surface-treating the surface-treated titanium oxide with methylhydrogenpolysiloxane while wet-dispersing it. Next, 2 parts by mass of SMT-A, 1 part by mass of a polyamide resin ("Amilan (registered trademark) CM8000" manufactured by Toray Industries, Inc., a quaternary copolymer polyamide resin of polyamide 6, polyamide 12, polyamide 66, and polyamide 610), 10 parts by mass of methanol, 1 part by mass of butanol, and 1 part by mass of toluene were mixed using a bead mill for 5 hours to obtain a coating liquid for the intermediate layer. The coating liquid for the intermediate layer was filtered using a filter with an opening of 5 μm. Then, the coating liquid for the intermediate layer was applied to the surface of the conductive substrate by the dip coating method. As the conductive substrate, a drum-shaped support made of aluminum was used. Subsequently, the applied coating liquid for the intermediate layer was dried at 130°C for 30 minutes to form an intermediate layer (film thickness: 1 μm) on the conductive substrate.

[0154] Next, a charge generation layer was formed. Specifically, 1.5 parts by mass of Y-type titanyl phthalocyanine, which is a charge generator, 1.0 part by mass of a polyvinyl acetal resin ("Esrec BX-5" manufactured by Sekisui Chemical Co., Ltd.), which is a base resin, 40.0 parts by mass of propylene glycol monomethyl ether, and 40.0 parts by mass of tetrahydrofuran were mixed using a bead mill for 2 hours to obtain a coating liquid for the charge generation layer. The coating liquid for the charge generation layer was filtered using a filter with an opening of 3 μm. The obtained filtrate was applied onto the intermediate layer by the dip coating method and dried at 50°C for 5 minutes. In this way, a charge generation layer (film thickness: 0.3 μm) was formed on the intermediate layer.

[0155] Next, a charge transport layer was formed. Specifically, 50.00 parts by mass of a hole transport agent (HTM-1), 100.00 parts by mass of a polyarylate resin F which is a binder resin, 5.00 parts by mass of metaterphenyl, 0.05 parts by mass of silicone oil (“KF96-50cs” manufactured by Shin-Etsu Chemical Co., Ltd., silicone oil having a dimethylpolysiloxane structure), 595.00 parts by mass of tetrahydrofuran, and 105.00 parts by mass of toluene were mixed to obtain a coating solution for the charge transport layer. By the dip coating method, the coating solution for the charge transport layer was applied onto the charge generation layer and dried using an oven for 70 minutes. The heating conditions by the oven were an initial temperature of 60°C, a final temperature reached of 130°C, and a heating rate of 1°C / min. In this way, a charge transport layer (film thickness: 20 μm) was formed on the charge generation layer to obtain a laminate type photoreceptor (A-1). In the laminate type photoreceptor (A-1), an intermediate layer was provided on a conductive substrate, a charge generation layer was provided on the intermediate layer, and a charge transport layer was provided on the charge generation layer.

[0156] (Manufacture of laminate type photoreceptors (A-2) to (A-15) and (B-1) to (B-6)) Except for using the hole transport agents and polyarylate resins shown in Table 8, each of the laminate type photoreceptors (A-2) to (A-15) and (B-1) to (B-6) was manufactured in the same manner as the manufacture of the laminate type photoreceptor (A-1).

[0157] (Evaluation of solubility in solvent) In an environment at a temperature of 22°C, 3 g of a polyarylate resin and an amount of tetrahydrofuran such that the concentration of the polyarylate resin was 15% by mass were stirred for 60 minutes to obtain an evaluation solution. The evaluation solution was visually confirmed, and the solubility of the polyarylate resin in tetrahydrofuran as the solvent was evaluated according to the following criteria. A polyarylate resin with an evaluation of A or B was determined to have good solubility in the solvent, and a polyarylate resin with an evaluation of C was determined to have poor solubility in the solvent. The evaluation results of each polyarylate resin are shown in Table 7. (Evaluation criteria for solubility in solvent) A: The polyarylate resin was completely dissolved in tetrahydrofuran, and no turbidity or gelation of the evaluation solution was confirmed. B: Cloudiness of the evaluation liquid was confirmed, but gelation of the evaluation liquid was not confirmed. C: Gelation of the evaluation liquid was confirmed.

[0158] <Evaluation of charging characteristics> Under the environment of temperature 25°C and relative humidity 50%RH, the charging characteristics of the photoreceptor were evaluated. Specifically, using a drum sensitivity tester (manufactured by Gentec Co., Ltd.), under the conditions that the charging current flowing through the charger is -10 μA and the rotation speed of the photoreceptor is 31 rpm, the surface of the photoreceptor was charged. The surface potential of the charged photoreceptor was measured. The measured surface potential was taken as the charging potential (V0, unit: -V) of the photoreceptor. The charging potentials of each photoreceptor are shown in Table 8. If the charging potential is -700 V or more and -650 V or less, it is judged that the photoreceptor has sufficient charging characteristics for actual use.

[0159] <Evaluation of initial sensitivity characteristics and repeated sensitivity characteristics> Under the environment of temperature 25°C and relative humidity 50%RH, the sensitivity characteristics of the photoreceptor were evaluated. Specifically, using a drum sensitivity tester (manufactured by Gentec Co., Ltd.), while rotating the photoreceptor, charging and exposure were repeated on the photoreceptor. The charging condition was such that the surface potential of the photoreceptor became -600 V. Also, the exposure condition was to extract monochromatic light (wavelength: 780 nm, exposure amount: 0.8 μJ / cm 2 ) from the light of a halogen lamp using a band-pass filter and irradiate the surface of the photoreceptor. When 80 milliseconds had elapsed since the exposure (irradiation with monochromatic light) at the 10th rotation of the photoreceptor, the surface potential of the photoreceptor was measured and taken as the post-exposure potential (V L at the 10th rotation, unit: -V). Also, when 80 milliseconds had elapsed since the exposure (irradiation with monochromatic light) at the 1860th rotation of the photoreceptor, the surface potential of the photoreceptor was measured and taken as the post-exposure potential (V L at the 1860th rotation, unit: -V). The post-exposure potentials at the 10th rotation and the 1860th rotation of each photoreceptor are shown in Table 8. From the post-exposure potential at the 10th rotation, the initial sensitivity characteristics of the photoreceptor were evaluated according to the following criteria. Also, from the post-exposure potential at the 1860th rotation, the repeated sensitivity characteristics of the photoreceptor were evaluated according to the following criteria. (Evaluation criteria for initial sensitivity characteristics) Good: The absolute value of the post-exposure potential at the 10th rotation is 90 V or less. Bad: The absolute value of the post-exposure potential at the 10th rotation exceeds 90 V. (Evaluation Criteria for Repeated Sensitivity Characteristics) Good: The absolute value of the post-exposure potential at the 1860th rotation is 120 V or less. Bad: The absolute value of the post-exposure potential at the 1860th rotation exceeds 120 V.

[0160] (Evaluation of Abrasion Resistance) The coating solution for the charge transport layer prepared in the above <Manufacture of the laminated photoreceptor> was applied to a polypropylene sheet (thickness: 0.3 mm) wound around an aluminum pipe (diameter: 78 mm). The coating solution for the charge transport layer applied was dried for 70 minutes using an oven. The heating conditions by the oven were an initial temperature of 60 °C, a final temperature reached of 130 °C, and a temperature increase rate of 1 °C / min. By drying, a polypropylene sheet on which a charge transport layer (film thickness 30 μm) was formed was produced. Subsequently, the charge transport layer was peeled off from the polypropylene sheet. The peeled charge transport layer was attached to a card-shaped member ("S-36" manufactured by Taber). The mass M A of the card-shaped member to which the charge transport layer was attached was measured. Next, the card-shaped member was attached to the turntable of a rotary abrasion tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.). Then, with an abrasion wheel ("CS-10" manufactured by Taber) with a load of 500 gf placed on the photosensitive layer on the card-shaped member, the turntable was rotated 1000 times at a rotation speed of 60 rpm. In this way, the charge transport layer on the turntable was abraded. After abrasion, the mass M B of the card-shaped member to which the charge transport layer was attached was measured again. And the abrasion loss (= M A - M B , unit: mg), which is the mass change of the charge transport layer before and after abrasion, was determined. The measured abrasion loss is shown in Table 8. From the abrasion loss, the abrasion resistance of the photoreceptor was evaluated according to the following criteria. (Evaluation Criteria for Abrasion Resistance) Good: The abrasion loss is 12.0 mg or less. Bad: The abrasion loss exceeds 12.0 mg.

[0161] In Table 7, "resin" indicates a polyarylate resin, and "solubility" indicates the evaluation of the solubility of the polyarylate resin in a solvent. The meanings of the terms in Table 8 are as follows. "Photoconductor" indicates a laminated photoconductor. "HTM" indicates a hole transport agent. "Resin" indicates a polyarylate resin. "Charging" indicates the evaluation of charging characteristics. "Sensitivity" indicates the evaluation of sensitivity characteristics. "V0" indicates the charging potential. The "V" in the "10th rotation" column L " indicates the potential after exposure at the 10th rotation of the photoconductor. The "V" in the "1860th rotation" column L " indicates the potential after exposure at the 1860th rotation of the photoconductor. "Unable to prepare coating solution" indicates that the polyarylate resin was not soluble in the solvent for forming the coating solution for the charge transport layer, and the charge transport layer coating solution could not be prepared.

[0162]

Table 7

[0163]

Table 8

[0164] As can be understood from Table 6, polyarylate resins K to O were not resins included in polyarylate resin (PA). Also, as can be understood from formula (P), polyarylate resin P was not a resin included in polyarylate resin (PA). Therefore, as shown in Table 7 and Table 8, the solubility of polyarylate resin K in the solvent was poor, and a coating solution for the charge transport layer could not be prepared using polyarylate resin K, and a photosensitive layer (more specifically, a charge transport layer) could not be formed. Also, as shown in Table 8, when polyarylate resins L and N were contained in the photosensitive layer, the abrasion resistance of the photoconductor could not be improved. Also, as shown in Table 8, when polyarylate resins M and O were contained in the photosensitive layer, the repeated sensitivity characteristics of the photoconductor could not be improved. Also, as shown in Table 8, when polyarylate resin P was contained in the photosensitive layer, the abrasion resistance and repeated sensitivity characteristics of the photoconductor could not be improved.

[0165] On the one hand, as can be understood from Table 6, polyarylate resins A to J were resins included in polyarylate resin (PA). Therefore, as shown in Table 7, the solubility of polyarylate resins A to J in solvents was good. Also, as shown in Table 8, when polyarylate resins A to J were contained in the photosensitive layer, the repetitive sensitivity characteristics and abrasion resistance of the photoreceptor could be improved. Further, as shown in Table 8, when polyarylate resins A to J were contained in the photosensitive layer, the repetitive sensitivity characteristics and abrasion resistance of the photoreceptor could be improved without impairing the charging characteristics and initial sensitivity characteristics of the photoreceptor.

[0166] From the above, it was shown that the polyarylate resin of the present invention including polyarylate resins A to J was excellent in solubility in solvents and could improve the repetitive sensitivity characteristics and abrasion resistance of the photoreceptor when contained in the photosensitive layer. Also, it was shown that the photoreceptor of the present invention including laminated photoreceptors (A-1) to (A-15) could form a photosensitive layer well and improve the repetitive sensitivity characteristics and abrasion resistance.

Industrial Applicability

[0167] The photoreceptor according to the present invention can be used in an image forming apparatus.

Explanation of Signs

[0168] 1: Laminated photoreceptor (laminated electrophotographic photoreceptor) 2: Conductive substrate 3: Photosensitive layer 3a: Charge generation layer 3b: Charge transport layer 3c: Single-layer photosensitive layer 10: Single-layer photoreceptor (single-layer electrophotographic photoreceptor)

Claims

1. having repeating units represented by formulas (1), (2), and (4), further having a repeating unit represented by formula (3), and the content ratio of the repeating unit represented by formula (3) with respect to the total number of the repeating units represented by formulas (1) and (3) being greater than 0% and less than 50%, and the content ratio of the repeating unit represented by formula (4) with respect to the total number of the repeating units represented by formulas (2) and (4) being 35% or more and 65% or less, a polyarylate resin. 【Chemical 1】 (In the above formula (1), R 1 and R 2 each independently represents a hydrogen atom or a methyl group, and X represents a divalent group represented by formula (X1) or (X2). In the formula (3), R 5 and R 6 each independently represents a hydrogen atom or a methyl group, and W represents a single bond or an oxygen atom.) [Chemical 2] (In the above formula (X1), t represents an integer of 1 or more and 3 or less, and * represents a bond, In the formula (X2), R 3 and R 4 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and * represents a bond.)

2. In the above formula (1), X represents a divalent group represented by the above formula (X1), and in the above formula (X1), t represents 2, the polyarylate resin according to Claim 1.

3. having the repeating unit represented by the above formula (3), the repeating unit represented by the above formula (3) including a repeating unit represented by formula (3-1), and the repeating unit represented by the above formula (1) including a repeating unit represented by formula (1-1), the polyarylate resin according to Claim 1 or 2. 【Chemical 3】

4. having the repeating unit represented by the above formula (3), the repeating unit represented by the above formula (3) including a repeating unit represented by formula (3-2), and the repeating unit represented by the above formula (1) including a repeating unit represented by formula (1-1), the polyarylate resin according to Claim 1 or 2. [Chemical Formula 4]

5. having the repeating unit represented by the above formula (3), and the content ratio of the repeating unit represented by the above formula (3) being greater than 0% and 30% or less, the polyarylate resin according to any one of Claims 1 to 4.

6. the repeating unit represented by the above formula (1) including a repeating unit represented by formula (1-1), (1-2), or (1-3), the polyarylate resin according to Claim 1. 【Chemical Formula 5】

7. Having repeating units represented by formulas (1), (2), and (4), not having the repeating unit represented by the above formula (3), the repeating unit represented by the above formula (1) including the repeating unit represented by the above formula (1-1), the repeating unit represented by the above formula (1) further including a repeating unit represented by formula (1-4), and the content ratio of the repeating unit represented by formula (4) with respect to the total number of the repeating units represented by formulas (2) and (4) being 35% or more and 65% or less, a polyarylate resin. 【Chemical Formula 6】 (In the above formula (1), R1 and R2 each independently represent a hydrogen atom or a methyl group, and X represents a divalent group represented by formula (X1) or (X2). (In the above formula (3), R5 and R6 each independently represent a hydrogen atom or a methyl group, and W represents a single bond or an oxygen atom.)) 【Chemical Formula 7】 (In the above formula (X1), t represents an integer of 1 or more and 3 or less, and * represents a bond. (In the above formula (X2), R3 and R4 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and * represents a bond.)) 【Chemical 8】

8. An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer, wherein the photosensitive layer contains a charge generating agent, a hole transporting agent, and a binder resin, and the binder resin contains the polyarylate resin according to any one of claims 1 to 7.

9. The electrophotographic photoreceptor according to claim 8, wherein the hole transporting agent contains a compound represented by formula (20), (21), or (22). 【Chemical Formula 9】 (In the above formula (20), R 21 and R 22 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, and R 23 to R 29 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, and two adjacent ones of R 25 to R 29 may be bonded to each other to form a ring, and a1 and a2 each independently represent an integer of 0 or more and 5 or less, In the formula (21), R 31 ~R 36 each independently represents an alkyl group having 1 to 8 carbon atoms or a phenyl group, R 37 and R 38 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group, b1, b2, b3, and b4 each independently represent an integer of 0 or more and 5 or less, b5 and b6 each independently represent an integer of 0 or more and 4 or less, and d and e each independently represent 0 or 1. In the above formula (22), R 41 to R 46 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, f1, f2, f4, and f5 each independently represent an integer of 0 or more and 5 or less, and f3 and f6 each independently represent an integer of 0 or more and 4 or less.)

10. The electrophotographic photoreceptor according to claim 8 or 9, wherein the hole transporting agent contains a compound represented by formula (HTM-1), (HTM-2), (HTM-3), (HTM-4), (HTM-5), or (HTM-6). 【Chemical Formula 10】 【Chemical Formula 11】

11. The photosensitive layer includes a charge generation layer containing the charge generating agent and a charge transport layer containing the hole transporting agent and the binder resin, and the electrophotographic photoreceptor according to any one of claims 8 to 10, wherein the charge transport layer is a single layer and is provided as the outermost surface layer.

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