Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that is excellent in wear resistance and filming resistance, and can prevent transfer memory.SOLUTION: An electrophotographic photoreceptor comprises a conductive substrate and a photosensitive layer. The photosensitive layer contains a polyarylate resin, a hole transport agent, and an antioxidant. The polyarylate resin includes a repeating unit represented by the formula (1) and a repeating unit represented by a specific formula (2). The antioxidant is a compound represented by the specific formula. In the formula (1), R1 and R2 each independently represent a hydrogen atom or a methyl group, and t represents an integer of 1 or more and 3 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, there has been an increasing demand for image forming apparatuses that do not include a static eliminator in order to save space and reduce costs. However, if a static eliminator is not used, a transfer bias of opposite polarity to the charging polarity is applied to the electrophotographic photosensitive member during the transfer process, and charges of the opposite polarity resulting from the transfer bias remain on the photosensitive layer of the electrophotographic photosensitive member. As a result, the charging process is carried out again while a potential difference remains between the exposed area (corresponding to the image area) and the non-exposed area (corresponding to the non-image area) of the previous rotation on the surface of the electrophotographic photosensitive member. For this reason, when an image is formed using an image forming apparatus that does not include a static eliminator, an image defect (transfer memory) may occur, in which a residual image (memory image) appears due to the image formed on the electrophotographic photosensitive member during the previous rotation.

[0003] Furthermore, electrophotographic photoreceptors are used as image carriers in electrophotographic image forming apparatuses (e.g., printers or multifunction peripherals). When an image is formed on a recording medium using an image forming apparatus, for example, a charging process, an exposure process, a development process, a transfer process, and a fixing process are carried out. Furthermore, as necessary, a charge removal process and a cleaning process are also carried out. To extend the life of an electrophotographic photoreceptor, it is desirable for the electrophotographic photoreceptor to have wear resistance and scratch resistance sufficient to withstand repeated use in these processes. Furthermore, in image formation by electrophotography, adhesion of toner components to the surface of the electrophotographic photoreceptor can cause image defects known as filming. Therefore, electrophotographic photoreceptors are required to have excellent performance in suppressing the occurrence of filming (filming resistance).

[0004] As an electrophotographic photoreceptor capable of reducing the residual potential during repeated use, Patent Document 1 proposes an electrophotographic photoreceptor in which a photosensitive layer contains a polyarylate resin as a binder resin, and further contains a specific charge transport agent and a specific additive. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5119733 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the electrophotographic photoreceptor described in Patent Document 1 does not take into consideration wear resistance, and there is room for improvement in terms of wear resistance. Furthermore, according to studies by the present inventors, it has been found that the electrophotographic photoreceptor described in Patent Document 1 is insufficient in wear resistance, filming resistance, scratch resistance, and suppression of transfer memory.

[0007] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide an electrophotographic photosensitive member, a process cartridge, and an image forming apparatus that have excellent abrasion resistance, filming resistance, and scratch resistance, and that can suppress transfer memory. [Means for solving the problem]

[0008] The electrophotographic photoreceptor according to the present invention comprises a conductive substrate and a photosensitive layer. The photosensitive layer contains a polyarylate resin, a hole transport agent, and an antioxidant. The polyarylate resin contains a repeating unit represented by formula (1) and a repeating unit represented by formula (2). The antioxidant is a compound represented by formula (AOX1).

[0009] [ka] In the formula (1), R 1and R 2 each independently represents a hydrogen atom or a methyl group, and t represents an integer of 1 or more and 3 or less.

[0010] [ka]

[0011] In the formula (2), R 3 represents a divalent group represented by formula (X1), (X2) or (X3).

[0012] [ka] In the formulae (X1), (X2) and (X3), * represents a bond.

[0013] [ka]

[0014] The process cartridge according to 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 photosensitive member.

[0015] The image forming apparatus according to the present invention includes an image carrier, a charging device that charges the surface of the image carrier, 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 as a toner image, and a transfer device that transfers the toner image from the image carrier to a transfer receiving body. The image carrier is the electrophotographic photosensitive body described above. [Effects of the Invention]

[0016] The electrophotographic photosensitive member, process cartridge, and image forming apparatus according to the present invention are excellent in abrasion resistance, filming resistance, and scratch resistance, and can suppress transfer memory. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view illustrating an example of a main part of a laminated electrophotographic photoreceptor according to a first embodiment of the present invention. [Figure 2] FIG. 3 is a cross-sectional view showing another example of a main part of the laminated electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view showing still another example of a main part of the laminated electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 4] 1 is a cross-sectional view illustrating an example of a main part of a single-layer electrophotographic photosensitive member according to a first embodiment of the present invention. [Figure 5] FIG. 3 is a cross-sectional view showing another example of a main part of the single-layer electrophotographic photosensitive member according to the first embodiment of the present invention. [Figure 6] FIG. 4 is a cross-sectional view illustrating an example of an image forming apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. The present invention can be modified in various ways within the scope of the object of the present invention, and embodiments obtained by appropriately combining the technical means described in different embodiments are also included in the technical scope of the present invention.

[0019] Hereinafter, the compound name may be followed by "system" to refer to the compound and its derivatives in a comprehensive manner. When the compound name is followed by "system" to refer to the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, general formulas and chemical formulas will be collectively referred to as "formulas." Furthermore, "independently" in the description of a formula means that it may represent the same group or different groups. Furthermore, each component described below may be used alone or in combination of two or more types. Furthermore, in this specification, "at least one of A and B" means "A and / or B." "A and / or B" means "A or B, or A and B."

[0020] In the following description, unless otherwise specified, the measured value of viscosity average molecular weight is a value measured in accordance with JIS (Japanese Industrial Standards) K7252-1:2016.

[0021] [First embodiment: electrophotographic photoreceptor] An electrophotographic photoreceptor (hereinafter sometimes simply referred to as photoreceptor) according to a first embodiment of the present invention will be described below. The photoreceptor according to this embodiment includes a conductive substrate and a photosensitive layer. The photosensitive layer contains at least a polyarylate resin, a hole transport agent, and an antioxidant. The photoreceptor may be a laminated electrophotographic photoreceptor (hereinafter sometimes referred to as laminated photoreceptor) or a single-layer electrophotographic photoreceptor (hereinafter sometimes referred to as single-layer photoreceptor).

[0022] (Layered photoreceptor) Hereinafter, a case where the photoreceptor 1 is a multi-layer photoreceptor will be described with reference to Figures 1 to 3. Figures 1 to 3 are each a cross-sectional view showing an example of a main part of the photoreceptor 1 (more specifically, a multi-layer photoreceptor).

[0023] As shown in FIG. 1, a multilayer photoreceptor, which is an example of a photoreceptor 1, includes, for example, a conductive substrate 2 and a photosensitive layer 3. When the photoreceptor 1 is a multilayer photoreceptor, the photosensitive layer 3 includes a charge generation layer 3a and a charge transport layer 3b. That is, the multilayer photoreceptor includes the charge generation layer 3a and the charge transport layer 3b as the photosensitive layer 3. The charge generation layer 3a contains a charge generating agent. The charge generation layer 3a may further contain a base resin as needed. The charge generation layer 3a may further contain an additive as needed.

[0024] The charge transport layer 3b contains at least a binder resin, a hole transport agent, and an antioxidant. The binder resin contains at least a polyarylate resin (hereinafter, sometimes referred to as a specific polyarylate resin) described below. The antioxidant contains at least an antioxidant (hereinafter, sometimes referred to as a specific antioxidant) described below. The charge transport layer 3b may further contain additives such as an electron acceptor compound and / or a leveling agent, as necessary.

[0025] As shown in FIG. 1, in the photoreceptor 1, a charge generation layer 3a may be provided on a conductive substrate 2, and a charge transport layer 3b may be provided on the charge generation layer 3a. Alternatively, as shown in FIG. 2, in the photoreceptor 1, a charge transport layer 3b may be provided on a conductive substrate 2, and a charge generation layer 3a may be provided on the charge transport layer 3b. However, by providing a charge transport layer 3b containing a specific polyarylate resin, a hole transport agent, and a specific antioxidant as the outermost layer, a photoreceptor 1 with superior abrasion resistance, filming resistance, scratch resistance, and transfer memory suppression effects can be obtained. For this reason, in the photoreceptor 1, it is preferable that the charge transport layer 3b be provided on the charge generation layer 3a.

[0026] Furthermore, as shown in FIG. 3, the photoreceptor 1 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. As shown in FIGS. 1 and 2, in the photoreceptor 1, the photosensitive layer 3 may be provided directly on the conductive substrate 2. Alternatively, as shown in FIG. 3, in the photoreceptor 1, the photosensitive layer 3 may be provided on the conductive substrate 2 via the intermediate layer 4. When the photoreceptor 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.

[0027] As shown in FIGS. 1 to 3, the photosensitive layer 3 (e.g., the charge transport layer 3b or the charge generation layer 3a) may be provided as the outermost layer of the photoreceptor 1. Alternatively, a protective layer (not shown) may be provided as the outermost layer of the photoreceptor 1. However, when a protective layer is formed on the photosensitive layer, charges generally accumulate at the interface between the photosensitive layer and the protective layer, which tends to increase the potential difference between the exposed and unexposed regions. An increase in the potential difference between the exposed and unexposed regions increases the likelihood of transfer memory. For this reason, as shown in FIGS. 1 to 3, it is preferable that the photosensitive layer 3 be provided as the outermost layer of the photoreceptor 1. Furthermore, as described above, by providing the charge transport layer 3b containing the specific polyarylate resin, the hole transport agent, and the specific antioxidant as the outermost layer, a photoreceptor 1 with excellent abrasion resistance, filming resistance, scratch resistance, and transfer memory suppression effects can be obtained.

[0028] The thickness of the charge generating layer 3a is not particularly limited, but is preferably 0.01 μm or more and 5.00 μm or less, and more preferably 0.10 μm or more and 3.00 μm or less.

[0029] The thickness of the charge transport layer 3b is not particularly limited, but is preferably from 2.00 μm to 100.0 μm, and more preferably from 5.00 μm to 50.00 μm. The case where the photoreceptor 1 is a multilayer photoreceptor has been described above with reference to FIGS.

[0030] (single-layer photoreceptor) Hereinafter, a case where the photoreceptor 1 is a single-layer type photoreceptor will be described with reference to Figures 4 and 5. Figures 4 and 5 are cross-sectional views showing an example of a main part of the photoreceptor 1 (more specifically, a single-layer type photoreceptor).

[0031] As shown in FIG. 4, a single-layer photoreceptor, which is an example of the photoreceptor 1, includes, for example, a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 included in the single-layer photoreceptor is a single layer. Hereinafter, the photosensitive layer 3 included in the single-layer photoreceptor may be referred to as a single-layer photosensitive layer 3c. The single-layer photosensitive layer 3c contains at least a binder resin, a hole transport agent, and an antioxidant. The binder resin contains at least a specific polyarylate resin. The antioxidant contains at least a specific antioxidant. The single-layer photosensitive layer 3c may contain a charge generating agent and various additives as necessary.

[0032] 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 an intermediate layer 4.

[0033] 4 and 5, the single-layer photosensitive layer 3c may be provided as the outermost layer, or a protective layer (not shown) may be provided as the outermost layer of the photoreceptor 1 on the single-layer photosensitive layer 3c.

[0034] The thickness of the single-layer photosensitive layer 3c is not particularly limited, but is preferably 5.00 μm or more and 100.00 μm or less, and more preferably 10.00 μm or more and 50.00 μm or less.

[0035] The above has described the case where the photoreceptor 1 is a single-layer photoreceptor with reference to Figures 4 and 5. The photoreceptor will be further described below.

[0036] (Conductive substrate) The conductive substrate 2 contains aluminum or an aluminum alloy. When the conductive substrate 2 contains aluminum or an aluminum alloy, the transfer of charges from the photosensitive layer 3 to the conductive substrate 2 tends to be improved. The shape of the conductive substrate 2 is appropriately selected in accordance with the structure of the image forming apparatus described later in the second embodiment. Examples of the shape of the conductive substrate 2 include a sheet shape and a drum shape. The thickness of the conductive substrate 2 is appropriately selected depending on the shape of the conductive substrate 2.

[0037] (Photosensitive layer) As described above, the photosensitive layer 3 contains a binder resin, a hole transport agent, and an antioxidant. The binder resin contains at least a specific polyarylate resin. The antioxidant contains at least a specific antioxidant. Next, the specific polyarylate resin, hole transport agent, and specific antioxidant contained in the photosensitive layer 3 will be described. In addition, other additives that may be contained in the photosensitive layer as needed, such as binder resins other than the specific polyarylate resin (hereinafter sometimes referred to as other binder resins), antioxidants other than the specific antioxidant, charge generating agents, base resins, electron acceptor compounds, and leveling agents, will also be described.

[0038] (Specific polyarylate resin) The photosensitive layer 3 contains a specific polyarylate resin as a binder resin. The specific polyarylate resin contains at least one repeating unit derived from a bisphenol represented by formula (1) and at least one repeating unit derived from a dicarboxylic acid represented by formula (2).

[0039] [ka]

[0040] In formula (1), R 1 and R 2 Each independently represents a hydrogen atom or a methyl group, and t represents an integer of 1 or more and 3 or less. 3 represents a divalent group represented by formula (X1), (X2) or (X3). [ka]

[0041] In addition, in the formulae (X1), (X2), and (X3), * represents a bond.

[0042] Hereinafter, the repeating units represented by formula (1) and formula (2) may be referred to as repeating units (1) and (2), respectively. Also, hereinafter, the divalent groups represented by formulas (X1), (X2), and (X3) may be referred to as groups (X1), (X2), and (X3), respectively.

[0043] When the photosensitive layer 3 contains the specific polyarylate resin as a binder resin, the photoreceptor 1 can be obtained that is excellent in abrasion resistance, filming resistance, scratch resistance, and transfer memory suppression effect.

[0044] In addition, in the formula (1), t preferably represents 2.

[0045] An example of the repeating unit (1) is a repeating unit represented by formula (P-1). Hereinafter, the repeating unit represented by formula (P-1) may be referred to as a repeating unit (P-1). At least one type of repeating unit (1) preferably contains a repeating unit (P-1). The repeating unit (1) is preferably a repeating unit (P-1).

[0046] [ka]

[0047] Examples of repeating unit (2) include repeating units represented by formulae (C-1), (C-2), and (C-3). Hereinafter, the repeating units represented by formulae (C-1), (C-2), and (C-3) may be referred to as repeating units (C-1), (C-2), and (C-3), respectively. At least one repeating unit (2) preferably contains at least one repeating unit selected from the group consisting of repeating units (C-1), (C-2), and (C-3), more preferably one or two of these repeating units. The repeating unit (2) preferably contains at least one repeating unit selected from the group consisting of repeating units (C-1), (C-2), and (C-3), more preferably one or two of these repeating units.

[0048] [ka]

[0049] The specific polyarylate resin preferably contains the repeating unit (P-1) and at least one repeating unit selected from the group consisting of repeating units (C-1), (C-2), and (C-3).More preferably, the specific polyarylate resin contains the repeating unit (P-1) and one or two repeating units selected from the group consisting of repeating units (C-1), (C-2), and (C-3).

[0050] The specific polyarylate resin may contain only repeating units (1) and (2). For example, the specific polyarylate resin may contain only repeating units (P-1) and at least one repeating unit selected from the group consisting of repeating units (C-1), (C-2), and (C-3). Furthermore, the specific polyarylate resin may further contain, in addition to repeating units (1) and (2), at least one repeating unit derived from a bisphenol other than repeating unit (1) and a repeating unit derived from a dicarboxylic acid other than repeating unit (2).

[0051] Suitable examples of the repeating units derived from bisphenol other than the repeating unit (1) include repeating units represented by formula (P-2), (P-3), (P-4), or (P-5). Among these, the repeating units represented by formula (P-4) and (P-5) are more preferred. When the specific polyarylate resin further contains at least one of the repeating units represented by formula (P-2), (P-3), (P-4), and (P-5) as the repeating unit derived from bisphenol in addition to the repeating unit (1), a photoreceptor 1 having excellent abrasion resistance and transfer memory suppression effects can be obtained.

[0052] [ka]

[0053] A suitable example of the repeating unit derived from a dicarboxylic acid other than the repeating unit (2) is a repeating unit represented by formula (C-4): When the specific polyarylate resin further contains a repeating unit represented by formula (C-4) as a repeating unit derived from a dicarboxylic acid in addition to the repeating unit (2), a photoreceptor 1 having superior abrasion resistance and transfer memory suppression effect can be obtained.

[0054] [ka]

[0055] Therefore, the specific polyarylate resin preferably further contains at least one of the repeating units represented by formulas (P-2), (P-3), (P-4), (P-5), and (C-4), and more preferably at least one of the repeating units represented by formulas (P-4), (P-5), and (C-4). Hereinafter, the repeating units represented by formulas (P-2), (P-3), (P-4), (P-5), and (C-4) may be referred to as repeating units (P-2), (P-3), (P-4), (P-5), and (C-4), respectively.

[0056] In the specific polyarylate resin, the repeating unit derived from a bisphenol and the repeating unit derived from a dicarboxylic acid are adjacently bonded to each other. Therefore, the specific polyarylate resin has at least a molecular chain in which the repeating unit (1) and the repeating unit (2) are adjacently bonded to each other. The repeating unit (1) may be bonded to the repeating unit (2) or to a repeating unit derived from a dicarboxylic acid other than the repeating unit (2). The repeating unit (2) may be bonded to the repeating unit (1) or to a repeating unit derived from a bisphenol other than the repeating unit (1).

[0057] The specific polyarylate resin may be, for example, a random copolymer, an alternating copolymer, a periodic copolymer, or a block copolymer.

[0058] Furthermore, when the specific polyarylate resin contains two or more types of repeating units derived from bisphenol, the arrangement of one type of repeating unit derived from bisphenol and the other type of repeating unit derived from bisphenol is not particularly limited. One type of repeating unit derived from bisphenol and the other type of repeating unit derived from bisphenol can be arranged randomly, alternately, periodically, or in blocks via the repeating unit derived from dicarboxylic acid. Furthermore, when the specific polyarylate resin contains two or more types of repeating units derived from dicarboxylic acid, the arrangement of one type of repeating unit derived from dicarboxylic acid and the other type of repeating unit derived from dicarboxylic acid is not particularly limited. One type of repeating unit derived from dicarboxylic acid and the other type of repeating unit derived from dicarboxylic acid can be arranged randomly, alternately, periodically, or in blocks via the repeating unit derived from bisphenol.

[0059] A preferred example of the specific polyarylate resin is a specific polyarylate resin having a structure represented by formula (Y), wherein W 1 , W 2 , W 3 , W 4 The polyarylate resins include polyarylate resins (R-1) to (R-7) in which the repeating units are shown in Table 1. In Table 1, (P-1), (P-4), (P-5), (C-1), (C-2), (C-3), and (C-4) represent the repeating units (P-1), (P-4), (P-5), (C-1), (C-2), (C-3), and (C-4), respectively.

[0060] [ka]

[0061] [Table 1]

[0062] In the polyarylate resin (R-1), the repeating unit (1) is the repeating unit (P-1), and the repeating unit (2) is the repeating units (C-2) and (C-3).

[0063] In the polyarylate resin (R-2), the repeating unit (1) is the repeating unit (P-1), and the repeating unit (2) is the repeating units (C-1) and (C-2). The polyarylate resin (R-2) further contains the repeating unit (P-4) as a repeating unit derived from bisphenol.

[0064] In the polyarylate resin (R-3), the repeating unit (1) is the repeating unit (P-1), and the repeating unit (2) is the repeating units (C-2) and (C-3). The polyarylate resin (R-3) further contains the repeating unit (P-4) as a repeating unit derived from bisphenol.

[0065] In the polyarylate resin (R-4), the repeating unit (1) is the repeating unit (P-1), and the repeating unit (2) is the repeating unit (C-3). The polyarylate resin (R-4) further contains the repeating unit (P-4) as a repeating unit derived from a bisphenol.

[0066] In the polyarylate resin (R-5), the repeating unit (1) is the repeating unit (P-1), and the repeating unit (2) is the repeating unit (C-1) and (C-2). The polyarylate resin (R-5) further contains the repeating unit (P-5) as a repeating unit derived from bisphenol.

[0067] In the polyarylate resin (R-6), the repeating unit (1) is the repeating unit (P-1), and the repeating unit (2) is the repeating unit (C-1). The polyarylate resin (R-6) further contains the repeating unit (P-5) as a repeating unit derived from a bisphenol, and further contains the repeating unit (C-4) as a repeating unit derived from a dicarboxylic acid.

[0068] In the polyarylate resin (R-7), the repeating unit (1) is the repeating unit (P-1), and the repeating unit (2) is the repeating unit (C-3). The polyarylate resin (R-7) further contains the repeating unit (P-5) as a repeating unit derived from a bisphenol, and further contains the repeating unit (C-4) as a repeating unit derived from a dicarboxylic acid.

[0069] As described above, the specific polyarylate resin may contain repeating units (1) and (2) as repeating units. However, as described above, the specific polyarylate resin may further contain repeating units derived from bisphenols other than repeating unit (1) and / or repeating units derived from bisphenols other than repeating unit (2). In addition to repeating units (1) and (2), the specific polyarylate resin preferably further contains at least one of repeating units (P-2), (P-3), (P-4), (P-5), and (C-4), more preferably at least one of repeating units (P-4), (P-5), and (C-4), thereby enabling the production of a photoreceptor 1 with superior wear resistance and transfer memory suppression effects.

[0070] The content of repeating unit (1) relative to the total number of repeating units derived from bisphenol contained in the specific polyarylate resin is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. The content of repeating unit (1) relative to the total number of repeating units derived from bisphenol contained in the specific polyarylate resin can be adjusted by changing the amount (unit: mole) of bisphenol added to form repeating unit (1) relative to the total amount (unit: mole) of bisphenol added to be used in the production of the specific polyarylate resin.

[0071] The content of repeating unit (2) relative to the total number of repeating units derived from dicarboxylic acid contained in the specific polyarylate resin is preferably 60% or more, more preferably 70% or more, and even more preferably 90% or more. The content of repeating unit (2) relative to the total number of repeating units derived from dicarboxylic acid contained in the specific polyarylate resin can be adjusted by changing the amount (unit: mole) of dicarboxylic acid added to constitute repeating unit (2) relative to the total (unit: mole) of dicarboxylic acid used in the production of the specific polyarylate resin.

[0072] The specific polyarylate resin may have a terminal group. Examples of the terminal group that the specific polyarylate resin has include a terminal group represented by formula (T-1). The terminal group represented by formula (T-1) is preferably a terminal group represented by formula (T-DMP) (hereinafter, sometimes referred to as terminal group (T-DMP)).

[0073] [ka]

[0074] In formula (T-1), R 4 represents an alkyl group having 1 to 6 carbon atoms or a halogen atom, and p represents an integer of 0 to 5. 4 preferably 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.

[0075] The * in the formulas (T-1) and (T-DMP) represents a bond. The bond represented by the * in the formulas (T-1) and (T-DMP) is bonded to a repeating unit located at the terminal of the specific polyarylate resin.

[0076] The viscosity average molecular weight of the specific polyarylate resin is preferably 10,000 or more, more preferably 20,000 or more, and particularly preferably 30,000 or more. When the viscosity average molecular weight of the specific polyarylate resin is 10,000 or more, the abrasion resistance of the photoreceptor is improved. On the other hand, the viscosity average molecular weight of the specific polyarylate resin is preferably 80,000 or less, more preferably 70,000 or less. When the viscosity average molecular weight of the specific polyarylate resin is 80,000 or less, the specific polyarylate resin is easily dissolved in a solvent for forming a charge transport layer and a solvent for forming a single-layer photosensitive layer, facilitating the formation of a charge transport layer and a single-layer photosensitive layer.

[0077] Next, a method for producing the specific polyarylate resin will be described. Examples of the method for producing the specific polyarylate resin include a method of condensation polymerization of a bisphenol (bisphenol monomer) for constituting a repeating unit derived from bisphenol and a dicarboxylic acid (dicarboxylic acid monomer) for constituting a repeating unit derived from dicarboxylic acid. As the bisphenol for constituting the repeating unit derived from bisphenol, a bisphenol containing a bisphenol for constituting the repeating unit (1) is used. As the dicarboxylic acid for constituting the repeating unit derived from dicarboxylic acid, a dicarboxylic acid containing a dicarboxylic acid for constituting the repeating unit (2) is used.

[0078] An example of a bisphenol for constituting the repeating unit (1) is a compound represented by formula (1-1). An example of a bisphenol for constituting a repeating unit derived from a bisphenol other than the repeating unit (1) is a compound represented by formula (1-2), (1-3), (1-4), and (1-5). Hereinafter, the compounds represented by formulas (1-1), (1-2), (1-3), (1-4), and (1-5) may be referred to as compounds (1-1), (1-2), (1-3), (1-4), and (1-5), respectively.

[0079] [ka]

[0080] Examples of dicarboxylic acids for constituting the repeating unit (2) include compounds represented by formulae (2-1), (2-2), and (2-3). Examples of dicarboxylic acids for constituting repeating units derived from dicarboxylic acids other than the repeating unit (2) include compounds represented by formula (2-4). Hereinafter, the compounds represented by formulae (2-1), (2-2), (2-3), and (2-4) may be referred to as compounds (2-1), (2-2), (2-3), and (2-4), respectively.

[0081] [ka]

[0082] In the polycondensation of bisphenol and dicarboxylic acid, a terminal terminator may be added. Examples of the terminal terminator include 2,6-dimethylphenol. By using 2,6-dimethylphenol as the terminal terminator, a terminal group (T-DMP) can be formed.

[0083] 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.

[0084] The photosensitive layer 3 preferably contains only the specific polyarylate resin as the binder resin. However, the photosensitive layer 3 may further contain, in addition to the specific polyarylate resin, a binder resin other than the specific polyarylate resin. The content of the specific polyarylate resin in the binder resin is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0085] Examples of other binder resins include thermoplastic resins (more specifically, polyarylate resins other than the specific polyarylate resins, 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).

[0086] (hole transport agent) Examples of the hole transport agent 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-oxadiazo Examples of the compound include phenylalanine compounds, 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.

[0087] As the hole transport agent, a hole transport agent having a triphenylamine structure is preferably used. Preferred examples of the hole transport agent include compounds represented by formula (HTM).

[0088] [ka]

[0089] In the formula (HTM), R 10 and R 11 R each independently represents an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms. 12 , R 13 , R 14 , R 15 , R 16 , R 17 , and R 18 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. f1 and f2 each independently represent an integer of 0 to 2. f3 and f4 each independently represent an integer of 0 to 5.

[0090] R 10 ~R 18 The alkyl group having 1 to 6 carbon atoms represented by R is preferably an alkyl group having 1 to 4 carbon atoms. 10 ~R 18 The alkoxy group having 1 to 6 carbon atoms represented by R is preferably an alkoxy group having 1 to 3 carbon atoms, more preferably an ethoxy group. 12 ~R 18 Preferably, each independently represents a hydrogen atom or an alkoxy group having 1 to 6 carbon atoms. When f3 represents an integer of 2 to 5, a plurality of R 10 may represent the same group or different groups. When f4 represents an integer of 2 or more and 5 or less, multiple R 11may represent the same group or different groups. f1 and f2 preferably represent 1. f3 and f4 each independently preferably represent an integer of 0 or more and 2 or less, more preferably 0.

[0091] Hereinafter, the compound represented by formula (HTM) may be referred to as compound (HTM). When the photosensitive layer 3 contains compound (HTM) as a hole transport agent together with the specific polyarylate resin and the specific antioxidant, the photoreceptor 1 can have excellent abrasion resistance, filming resistance, scratch resistance, and transfer memory suppression effects.

[0092] An example of the compound (HTM) is a compound represented by formula (HTM1). Hereinafter, the compound represented by formula (HTM1) may be referred to as compound (HTM1). When the photosensitive layer 3 contains the compound (HTM1) as a hole transport agent together with the specific polyarylate resin and the specific antioxidant, the photoreceptor 1 can have even better abrasion resistance, filming resistance, scratch resistance, and transfer memory suppression effects.

[0093] [ka]

[0094] The content of the hole transport agent is preferably 10.00 parts by mass or more and 200.00 parts by mass or less, and more preferably 40.00 parts by mass or more and 80.00 parts by mass or less, relative to 100.00 parts by mass of the specific polyarylate resin.

[0095] (Specific antioxidant) The photosensitive layer 3 contains a specific antioxidant as an antioxidant. The specific antioxidant is a compound represented by formula (AOX1). Hereinafter, the compound represented by formula (AOX1) may be referred to as compound (AOX1).

[0096] [ka]

[0097] When the photosensitive layer 3 contains the specific antioxidant as an antioxidant, the photoreceptor 1 can have excellent abrasion resistance.

[0098] The content of the specific antioxidant is preferably 1.00 parts by mass or more and 10.00 parts by mass or less, and more preferably 3.00 parts by mass or more and 9.00 parts by mass or less, relative to 100.00 parts by mass of the specific polyarylate resin.

[0099] The photosensitive layer 3 preferably contains only the specific antioxidant as the antioxidant. However, the photosensitive layer 3 may further contain an antioxidant other than the specific antioxidant in addition to the specific antioxidant. The content ratio of the specific antioxidant to the mass of the antioxidant is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 100 mass%.

[0100] Examples of antioxidants other than the specific antioxidant include hindered phenols, hindered amines, paraphenylenediamines, arylalkanes, hydroquinones, spirochromans, spiroindanones, or derivatives thereof, organic sulfur compounds, and organic phosphorus compounds.

[0101] (charge generating material) Examples of charge generating agents 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 photosensitive layer 3 may contain only one type of charge generating agent, or may contain two or more types of charge generating agents.

[0102] Phthalocyanine pigments are pigments having a phthalocyanine structure. Examples of phthalocyanine pigments include metal phthalocyanines and metal-free phthalocyanines. Examples of metal phthalocyanines include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine.

[0103] The phthalocyanine pigment may be crystalline or amorphous. Examples of metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter, sometimes referred to as X-type metal-free phthalocyanine). Examples of titanyl phthalocyanine crystals include 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).

[0104] For example, in a digital optical image forming apparatus (for example, a laser beam printer or facsimile using a light source such as a semiconductor laser), it is preferable to use a photoreceptor having sensitivity in the wavelength region of 700 nm or more. As the charge generating agent, phthalocyanine pigments are preferred, titanyl phthalocyanine is more preferred, and Y-type titanyl phthalocyanine is even more preferred, because they have a high quantum yield in the wavelength region of 700 nm or more. Titanyl phthalocyanine is represented by formula (CGM1).

[0105] [ka]

[0106] Y-type titanyl phthalocyanine is a titanyl phthalocyanine crystal having, for example, a main peak at 27.2° within a Bragg angle 2θ±0.2° in a CuKα characteristic X-ray diffraction spectrum. The main peak in a CuKα characteristic X-ray diffraction spectrum is the peak having the first or second highest intensity within a Bragg angle (2θ±0.2°) range of 3° to 40°. Y-type titanyl phthalocyanine has a peak at 9.6° within a Bragg angle 2θ±0.2° in a CuKα characteristic X-ray diffraction spectrum, but does not have a peak at 26.2°.

[0107] The CuKα characteristic X-ray diffraction spectrum is measured, for example, by the following method. First, a sample (titanyl phthalocyanine) is loaded into a sample holder of an X-ray diffractometer (e.g., Rigaku Corporation's "RINT (registered trademark) 1100"), and the X-ray diffraction spectrum is measured under the conditions of a Cu X-ray tube, a tube voltage of 40 kV, a tube current of 30 mA, and a CuKα characteristic X-ray wavelength 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.

[0108] When the photoreceptor is a multilayer photoreceptor, the content of the charge generating agent is preferably 10.00 parts by mass or more and 300.00 parts by mass or less, and more preferably 100.00 parts by mass or more and 200.00 parts by mass or less, relative to 100.00 parts by mass of the base resin. When the photoreceptor is a single-layer photoreceptor, the content of the charge generating agent is preferably 0.10 parts by mass or more and 50.00 parts by mass or less, relative to 100.00 parts by mass of the binder resin.

[0109] (base resin) The charge generating layer 3a may contain a base resin. Examples of the base resin are the same as the examples of other binder resins contained in the charge transport layer 3b or the single-layer photosensitive layer 3c. However, in order to properly form the charge generating layer 3a and the charge transport layer 3b, it is preferable to select a resin different from the resin used as the binder resin as the base resin. For example, a polyvinyl acetal resin is used as the base resin.

[0110] (Electron acceptor compounds) When the photoreceptor 3 is a multilayer photoreceptor, the charge transport layer 3b preferably contains an electron acceptor compound. Examples of electron acceptor compounds 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.

[0111] A suitable example of the electron acceptor compound is a compound represented by formula (EA).

[0112] [ka]

[0113] In formula (EA), Q 1 , Q 2 , Q 3 and Q 4 each independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an aryl group having 6 to 14 carbon atoms.

[0114] Q in Equation (EA) 1 , Q 2 , Q 3 and Q 4 The alkyl group having 1 to 6 carbon atoms represented by is preferably a tert-butyl group.

[0115] Q in Equation (EA) 1 , Q 2 , Q 3 and Q 4 The alkoxy group having 1 to 6 carbon atoms represented by is preferably an alkoxy group having 1 to 3 carbon atoms. 1 , Q 2 , Q 3 and Q 4 The cycloalkyl group having 5 to 7 carbon atoms represented by is preferably a cyclohexyl group. 1 , Q 2 , Q 3 and Q 4 The aryl group having 6 to 14 carbon atoms represented by is preferably an aryl group having 6 to 10 carbon atoms.

[0116] In formula (EA), Q 1 , Q 2 , Q 3 and Q 4 preferably each independently represents an alkyl group having 1 to 6 carbon atoms, and more preferably represents a tert-butyl group.

[0117] Hereinafter, the compound represented by formula (EA) may be referred to as compound (EA). A suitable example of compound (EA) is a compound represented by formula (EA1). Hereinafter, the compound represented by formula (EA1) may be referred to as compound (EA1).

[0118] [ka]

[0119] The content of the electron acceptor compound is preferably 0.10 parts by mass or more and 10.00 parts by mass or less, and more preferably 1.00 parts by mass or more and 5.00 parts by mass or less, relative to 100.00 parts by mass of the specific polyarylate resin.

[0120] (additives) Examples of additives include anti-degradants (e.g., antioxidants, radical scavengers, singlet quenchers, or UV absorbers), softeners, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, donors, surfactants, plasticizers, sensitizers, and leveling agents, such as dimethyl silicone oil.

[0121] (middle class) In the photoreceptor 1, the intermediate layer 4 (undercoat layer) is located, for example, between the conductive substrate 2 and the photosensitive layer 3. The intermediate layer 4 contains, for example, inorganic particles and a resin (intermediate layer resin) used in the intermediate layer 4. It is believed that the presence of the intermediate layer 4 maintains an insulating state sufficient to suppress leakage, while smoothing the flow of current generated when the photoreceptor 1 is exposed to light, thereby suppressing an increase in resistance.

[0122] Examples of inorganic particles include particles of metals (e.g., aluminum, iron, or copper), metal oxides (e.g., titanium oxide, alumina, zirconium oxide, tin oxide, or zinc oxide), or non-metal oxides (e.g., silica). These inorganic particles may be used alone or in combination of two or more.

[0123] The resin for the intermediate layer is not particularly limited as long as it is a resin that can be used to form the intermediate layer 4 .

[0124] The intermediate layer 4 may contain various additives to the extent that they do not adversely affect the electrophotographic characteristics of the photoreceptor 1. The additives are the same as those in the photosensitive layer 3.

[0125] The thickness of the intermediate layer 4 is not particularly limited, but is preferably 0.10 μm or more and 5.00 μm or less.

[0126] The photoreceptor 1 according to the first embodiment has been described above with reference to Figures 1 to 5. According to the first embodiment, it is possible to provide a photoreceptor 1 that is excellent in abrasion resistance, filming resistance, scratch resistance, and transfer memory suppression effect.

[0127] [Second embodiment: image forming apparatus] An image forming apparatus according to a second embodiment of the present invention will be described below. A tandem color image forming apparatus will be described below as an example with reference to Fig. 6. Fig. 6 is a cross-sectional view showing an example of an image forming apparatus.

[0128] 6 includes image forming units 40a, 40b, 40c, and 40d, a transfer belt 50, and a fixing device 54. The image forming units 40a, 40b, 40c, and 40d form toner images of different colors based on electrostatic latent images.

[0129] In the image forming apparatus 100, each of the image forming units 40a to 40d sequentially overlays toner images of multiple colors (for example, four colors: black, cyan, magenta, and yellow) on the recording medium P on the transfer belt 50. Hereinafter, when it is not necessary to distinguish between each of the image forming units 40a to 40d, each of the image forming units 40a to 40d will be simply referred to as the image forming unit 40.

[0130] The image forming unit 40 includes an image carrier 30, a charging device 42, an exposure device 44, a developing device 46, a transfer device 48, and a cleaning blade 52 that cleans the surface of the image carrier 30. The image carrier 30 is the photoreceptor 1 of the first embodiment.

[0131] As already mentioned, the photoreceptor 1 according to the first embodiment has excellent abrasion resistance, filming resistance, and scratch resistance, and can suppress the occurrence of transfer memory. Therefore, by including the photoreceptor 1 according to the first embodiment as the image carrier 30, the image forming apparatus 100 according to the present embodiment can improve the abrasion resistance, filming resistance, and scratch resistance of the image carrier 30, and can suppress transfer memory.

[0132] The 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 Figure 6. Around the image carrier 30, a charging device 42, an exposure device 44, a developing device 46, a transfer device 48, and a cleaning blade 52 are provided in this order from the upstream side in the rotation direction of the image carrier 30.

[0133] The charging device 42 positively charges the surface (for example, the circumferential surface) of the image carrier 30. The charging device 42 is, for example, a charging roller.

[0134] 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.

[0135] 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 circumferential 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 the 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 the toner and 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 a toner image.

[0136] The transfer belt 50 transports 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 so as to be rotatable in the direction of the arrow (clockwise direction) in FIG. 6.

[0137] The transfer device 48 transfers the toner image developed by the developing device 46 from the surface of the image carrier 30 to a transfer recipient. The transfer recipient is a recording medium P. When the toner image is transferred, the image carrier 30 is in contact with the recording medium P. In other words, the image forming apparatus 100 employs a direct transfer method. The transfer device 48 is, for example, a transfer roller.

[0138] The image carrier 30 is recharged by the charging device 42 without being neutralized in the area where the toner image has been transferred to the recording medium P, which is the transfer recipient. Generally, image forming apparatuses that employ a neutralization-less system tend to be prone to the occurrence of transfer memory. However, the image forming apparatus 100 according to this embodiment is equipped with a photosensitive member 1 that can suppress transfer memory as the image carrier 30, and thus can effectively suppress transfer memory even when employing a neutralization-less system. For this reason, the image forming apparatus 100 according to this embodiment is particularly effective when employing a neutralization-less system that does not have a neutralization device.

[0139] 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. By heating and / or pressurizing the toner image, the toner image is fixed to the recording medium P. As a result, an image is formed on the recording medium P.

[0140] An example of an image forming apparatus according to the present embodiment has been described above. However, the image forming apparatus according to the present embodiment is not limited to the image forming apparatus 100 already described. For example, the image forming apparatus 100 already described was a color image forming apparatus. However, the image forming apparatus according to the present embodiment may be a monochrome image forming apparatus. In this case, the image forming apparatus according to the present embodiment may include, for example, only one image forming unit. Furthermore, the image forming apparatus 100 already described employs a tandem system. However, the image forming apparatus according to the present embodiment may employ, for example, a rotary system. Furthermore, the image forming apparatus 100 already described employs a contact development system. However, the image forming apparatus according to the present embodiment may employ a non-contact development system. Furthermore, the image forming apparatus 100 already described employs a direct transfer system. However, the image forming apparatus according to the present embodiment may employ an intermediate transfer system. When the image forming apparatus according to the present embodiment employs an intermediate transfer system, the transfer target corresponds to an intermediate transfer belt. Furthermore, the image forming unit 40 already described does not include a static eliminator. However, the image forming unit included in the image forming apparatus according to the present embodiment may further include a static eliminator. Furthermore, the image forming unit 40 already described includes a cleaning blade. However, the image forming unit provided in the image forming apparatus according to this embodiment does not have to include a cleaning member such as a cleaning blade. Also, in this embodiment, a charging roller has been described as an example of the charging device 42. However, the charging device provided in the image forming apparatus according to this embodiment may be a charging device other than a charging roller (for example, a scorotron charger, a charging brush, or a corotron charger).

[0141] <Third Embodiment: Process Cartridge> Next, with continued reference to FIG. 6, an example of a process cartridge according to a third embodiment of the present invention will be described. The process cartridge according to this embodiment corresponds to each of the image forming units 40a to 40d. The process cartridge according to this embodiment includes an image carrier 30. The image carrier 30 is the photoreceptor 1 according to the first embodiment. As already mentioned, the photoreceptor 1 according to the first embodiment has excellent abrasion resistance, filming resistance, and scratch resistance, and can suppress transfer memory. Therefore, by including the photoreceptor 1 according to the first embodiment as the image carrier 30, the process cartridge according to this embodiment can improve the abrasion resistance, filming resistance, and scratch resistance of the image carrier 30 and suppress transfer memory.

[0142] The process cartridge according to this embodiment further includes, in addition to the image carrier 30, 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 according to this embodiment may further include one or both of a cleaning blade 52 and a static eliminator (not shown). The process cartridge according to this embodiment is designed to be detachable from the image forming apparatus 100. Therefore, the process cartridge according to this embodiment is easy to handle, and can be easily and quickly replaced, including the image carrier 30, when the sensitivity characteristics of the image carrier 30 deteriorate.

[0143] As an example of the process cartridge according to the present embodiment, a process cartridge equipped with the photosensitive member 1 according to the first embodiment has been described above with reference to Fig. 6. However, the process cartridge according to the present embodiment is not limited to the process cartridge equipped with the photosensitive member 1 according to the first embodiment. The process cartridge according to the present embodiment can be modified in the same manner as the modified image forming unit already described (for example, the modified example described in the second embodiment). [Example]

[0144] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples. In the following examples, a multi-layer photoreceptor was formed as the photoreceptor.

[0145] <Synthesis of Polyarylate Resins (R-1) to (R-11) and (r-1) to (r-4)> Polyarylate resins (R-1) to (R-7) and polyarylate resins (r-1) to (r-4) of formula (Y) in which W1, W2, W3, and W4 are repeating units shown in Table 2 were synthesized by the following method. As mentioned above, polyarylate resins (R-1) to (R-7) are specific polyarylate resins.

[0146] [Table 2]

[0147] (Synthesis of polyarylate resin (R-1)) A three-neck flask equipped with a thermometer, a three-way stopcock, and a dropping funnel was used as the reaction vessel. The monomer compound (1-1) (41.0 mmol), 2,6-dimethylphenol (0.413 mmol) as a terminal capping agent, sodium hydroxide (98 mmol) as a base, and benzyltributylammonium chloride (0.384 mmol) as a catalyst were placed in the reaction vessel, and the air in the reaction vessel was replaced with argon gas. Water (300 mL) was then added to the contents of the reaction vessel, and the contents of the reaction vessel were stirred at 50 °C for 1 hour. The contents of the reaction vessel were then cooled to 10 °C to obtain an alkaline aqueous solution SA.

[0148] Next, the dicarboxylic acid dichloride (16.0 mmol) of the monomer compound (2-2) and the dicarboxylic acid dichloride (16.0 mmol) of the monomer compound (2-3) were dissolved in chloroform (150 mL), thereby obtaining a chloroform solution SB.

[0149] Next, the chloroform solution SB was slowly added dropwise to the alkaline aqueous solution SA using a dropping funnel over 110 minutes. The contents of the reaction vessel were then stirred for 4 hours while the temperature (liquid temperature) of the contents of the reaction vessel was adjusted to 15±5°C, allowing the polymerization reaction to proceed. The upper layer (aqueous layer) of the contents of the reaction vessel was then removed using a decanter to obtain an organic layer (OL-1).

[0150] Meanwhile, ion-exchanged water (400 mL) was added to an Erlenmeyer flask. The organic layer (OL-1) obtained by the polymerization reaction described above was then added to the Erlenmeyer flask. Next, chloroform (400 mL) and acetic acid (2 mL) were further added to the Erlenmeyer flask. The contents of the Erlenmeyer flask were then stirred at room temperature (25°C) for 30 minutes. The upper layer (aqueous layer) of the contents of the Erlenmeyer flask was then removed using a decanter to obtain an organic layer (OL-2). The obtained organic layer (OL-2) was washed with ion-exchanged water (1 L) using a separatory funnel. Washing with ion-exchanged water was repeated five times, resulting in an organic layer (OL-2) that was washed with a total of 5 L of ion-exchanged water. The washed organic layer (OL-2) was then filtered to obtain a filtrate. The filtrate was then slowly added dropwise to methanol (1 L) to obtain a precipitate. The precipitate was then filtered off. The extracted precipitate was dried under vacuum at 70°C for 12 hours. As a result, a polyarylate resin (R-1) having the composition shown in Table 3 (type and addition ratio of each monomer) was obtained.

[0151] (Synthesis of Polyarylate Resins (R-2) to (R-7) and (r-1) to (r-4)) Polyarylate resins (R-2) to (R-7) and (r-1) to (r-4) were synthesized using the same method as for polyarylate resin (R-1), except that the type and addition rate of each monomer was changed as shown in Table 3. The amount of each bisphenol monomer added was set so that the total amount of bisphenol monomers was 41.0 mmol and the bisphenol addition rate was as shown in Table 1. For example, in the synthesis of polyarylate resin (R-2), the amount of compound (1-1) added was 38.95 mmol (= 41.0 × 95 / 100), and the amount of compound (1-4) added was 2.05 mmol (= 41.0 × 5 / 100). The amount of each dicarboxylic acid monomer added was set so that the total amount of dicarboxylic acid monomers was 32.0 mmol and the dicarboxylic acid addition rate was as shown in Table 2. For example, in the synthesis of resin (R-2), the amount of compound (2-1) added was 20.8 mmol (=32.0×65 / 100), and the amount of compound (2-2) added was 11.2 mmol (=32.0×35 / 100).

[0152] The obtained polyarylate resins (R-1) to (R-7) and (r-1) to (r-4) were identified as follows: 1 H-NMR (proton nuclear magnetic resonance analysis) was used.

[0153] (Measurement of viscosity average molecular weight) The viscosity average molecular weights of the obtained polyarylate resins (R-1) to (R-7) and (r-1) to (r-4) were measured in accordance with JIS (Japanese Industrial Standards) K7252-1: 2016. The measured viscosity average molecular weights are shown in Table 3 together with the compositions of the polyarylate resins (R-1) to (R-7) and (r-1) to (r-4).

[0154] In Table 3, "monomer" refers to the monomer used in the synthesis of the polyarylate resin. "Forming unit" refers to the repeating unit formed from the corresponding monomer. "Resin" refers to the polyarylate resin. "Bisphenol addition rate" refers to the percentage (unit: %) of the amount (unit: moles) of the corresponding bisphenol monomer relative to the total amount (unit: moles) of the bisphenol monomer added in the synthesis of the polyarylate resin. "Dicarboxylic acid addition rate" refers to the percentage (unit: %) of the amount (unit: moles) of the corresponding dicarboxylic acid monomer relative to the total amount (unit: moles) of the dicarboxylic acid monomer added in the synthesis of the polyarylate resin. "DMP" refers to 2,6-dimethylphenol. [Table 3]

[0155] <Production of Photoreceptors (A-1) to (A-8) and (B-1) to (B-13)> Photoreceptors (A-1) to (A-8) according to Examples 1 to 8 and photoreceptors (B-1) to (B-13) according to Comparative Examples 1 to 13 were produced by the following method.

[0156] [Production of photoreceptor (A-1)] (Preparation of coating solution for intermediate layer) Methanol, n-butanol, and toluene were mixed to prepare Solvent VA (methanol / n-butanol / toluene = 3 / 1 / 1 by mass). 1.00 parts by mass of polyamide resin ("Amilan® CM8000" manufactured by Toray Industries, Inc., a tetrapolymer polyamide resin of polyamide 6, polyamide 12, polyamide 66, and polyamide 610) was dissolved in 4.00 parts by mass of Solvent VA to prepare Resin Solution VB. 2.00 parts by mass of titanium oxide, 0.50 parts by mass of ion-exchanged water, 5.00 parts by mass of Resin Solution VB, and 8.00 parts by mass of Solvent VA were mixed using a circulating wet disperser ("DYNO®-MILL" manufactured by Willy & Bachofen) at a peripheral speed of 8 m / s for 6 hours to prepare a coating solution for the intermediate layer. The titanium oxide used was a prototype "SMT-A" (number average particle size 10 nm) manufactured by Teika Corporation, which was primarily surface-treated with alumina and silica, and then secondary-surface-treated with methylhydrogenpolysiloxane.

[0157] (Formation of intermediate layer) The obtained intermediate layer coating liquid was filtered using a filter with a mesh size of 30.00 μm. Then, the intermediate layer coating liquid was applied to the surface of a conductive substrate by dip coating. An aluminum drum-shaped support (diameter: 30.00 mm, length: 245.00 mm) was used as the conductive substrate. Next, the applied intermediate layer coating liquid was heat-treated at 120°C for 20 minutes to form an intermediate layer (film thickness: 0.70 μm) on the conductive substrate.

[0158] (Preparation of Coating Solution for Charge Generating Layer) Propylene glycol monomethyl ether and tetrahydrofuran were mixed to obtain solvent VC (mass ratio: propylene glycol monomethyl ether / tetrahydrofuran = 1 / 2). 1.00 parts by weight of polyvinyl acetal resin ("S-LEC BX-5" manufactured by Sekisui Chemical Co., Ltd.) was dissolved in 19.00 parts by weight of solvent VC to obtain resin solution VD. 2.30 parts by weight of Y-type titanyl phthalocyanine as a charge generating agent, 20.00 parts by weight of resin solution VD (amount of polyvinyl acetal resin: 1.00 parts by weight), and 65.00 parts by weight of solvent VC were mixed using a media-type disperser (bead mill) to obtain a coating liquid for a charge generating layer. The mixing conditions were as follows: Peripheral speed: 60rpm Mixing time: 4 hours Media for media-type disperser: Zirconia beads (diameter 0.65 mm) Media filling rate of media type disperser: 46.2%

[0159] (Formation of Charge Generation Layer) The resulting charge generating layer coating solution was filtered using a filter with a mesh size of 5 μm. The resulting filtrate was applied onto the intermediate layer by dip coating and heat-treated at 90° C. for 20 minutes. In this way, a charge generating layer (film thickness: 0.5 μm) was formed on the intermediate layer.

[0160] (Preparation of Coating Solution for Charge Transport Layer) Toluene and tetrahydrofuran were mixed to obtain solvent VE (mass ratio: toluene / tetrahydrofuran = 1 / 9). 61.00 parts by mass of compound (HTM1) as a hole transport agent, 2.00 parts by mass of compound (EA1) as an electron acceptor compound, 0.05 parts by mass of dimethyl silicone oil (KF96-50CS manufactured by Shin-Etsu Chemical Co., Ltd.) as a leveling agent, 100.00 parts by mass of polyarylate resin (R-1), and 4.00 parts by mass of compound (AOX1) as an antioxidant were dissolved in 650.00 parts by mass of solvent VE to obtain a coating liquid for a charge transport layer. As mentioned above, compound (AOX1) is a specific antioxidant.

[0161] (Formation of charge transport layer) The obtained charge transport layer coating liquid was applied onto the charge generation layer by dip coating, heated from 60°C to 125°C at a temperature increase rate of 1°C / min, and then heat-treated at 125°C for a total of 60 minutes. In this way, a charge transport layer (film thickness: 26.00 μm) was formed on the charge generation layer, and photoreceptor (A-1) was obtained. Photoreceptor (A-1) had an intermediate layer on a conductive substrate, a charge generation layer on the intermediate layer, and a charge transport layer on the charge generation layer.

[0162] [Production of Photoreceptors (A-2) to (A-8) and (B-1) to (B-13)] Photoreceptors (A-2) to (A-8) and (B-1) to (B-13) were each produced using the same method as that for producing photoreceptor (A-1), except that at least one of the type of polyarylate resin, the type of antioxidant, and the content of the antioxidant in the charge transport layer coating liquid was changed as shown in Table 4.

[0163] <Evaluation> The obtained photoreceptors (A-1) to (A-8) and (B-1) to (B-13) were each evaluated for filming resistance, scratch resistance, suppression of transfer memory (transfer memory potential difference), and abrasion resistance using the methods described below.

[0164] (Evaluation of filming resistance and scratch resistance) For these evaluations, paper ("Askul Multipaper Super Economy+" sold by Askul Corporation) was used. A modified image forming apparatus ("FS-C5250DN" manufactured by Kyocera Document Solutions Inc.) was used as the evaluation machine for these evaluations. This evaluation machine was equipped with a charging roller made of epichlorohydrin resin with conductive carbon dispersed therein as a charging device. The charging polarity of the charging roller was positive, and the voltage applied to the charging roller was a DC voltage. This evaluation machine employed a two-component development system and an intermediate transfer system. This evaluation machine was also equipped with a cleaning blade and a static eliminator.

[0165] The photoreceptor was mounted on an evaluation machine, and image I (a character image with a printing rate of 5%) was continuously printed on 50,000 sheets of paper using this evaluation machine in an environment of a temperature of 23°C and a relative humidity of 50%RH. Next, image II (an image including a halftone image and a white background image) was printed on one sheet of paper using the evaluation machine, and the resulting image was used as the first evaluation image.

[0166] After obtaining the first evaluation image, the photoreceptor was removed from the evaluation machine. The surface of the photoreceptor was observed with the naked eye to check for scratches and filming on the surface of the photoreceptor. After the naked eye observation, the photoreceptor was again mounted on the evaluation machine.

[0167] Next, in an environment of a temperature of 10°C and a relative humidity of 15%RH, an image I (a character image with a printing rate of 5%) was continuously printed on 50,000 sheets of paper using an evaluation machine. Next, an image II (an image including a halftone image and a white background image) was printed on one sheet of paper using the evaluation machine, and the resulting image was used as a second evaluation image.

[0168] The first evaluation image and the second evaluation image were observed to confirm the presence or absence of image defects due to scratches and filming. Image defects due to scratches include, for example, white streaks and black streaks. Image defects due to filming include, for example, dash marks and fog. Dash marks are black dots arranged parallel to the paper conveyance direction. The larger the area where filming occurred on the surface of the photoreceptor, the more fog originating from the dash marks occurred in the formed image. Based on the results of checking the surface of the photoreceptor and the results of checking the image defects on the first evaluation image and the second evaluation image, the filming resistance and scratch resistance were evaluated based on the following criteria.

[0169] A (particularly good): Neither scratches nor filming occurred on the surface of the photoreceptor. In addition, no image defects occurred in either the first or second evaluation image. B (Good): At least one of scratches and filming was found on the surface of the photoreceptor, but no image defects were found in either the first or second evaluation image. C (poor): At least one of scratches and filming was found on the surface of the photoreceptor. Also, image defects were found in at least one of the first and second evaluation images.

[0170] (Evaluation of transfer memory suppression (evaluation of transfer memory potential difference)) The evaluation of the suppression of transfer memory (also called "transfer memory resistance") was carried out in an environment of 23°C temperature and 65% RH relative humidity. Using a drum sensitivity tester (manufactured by Gentec Co., Ltd., no static eliminator), the photoreceptor was charged at a rotation speed of 220 rpm so that the surface potential of the photoreceptor was -600 V. Next, while a current of +15 μA was applied to the transfer device, monochromatic light (wavelength: 780 nm, exposure amount: 0.08 μJ / cm) extracted from the light of a halogen lamp was applied using a bandpass filter. 2 ) was irradiated onto the surface of the photoconductor. After the irradiation of the monochromatic light was completed and the photoconductor had rotated one revolution, the surface potential of the photoconductor was measured. The measured surface potential was expressed as the potential at 15 μA (V L1 , unit: -V).

[0171] Next, the current flowing through the transfer device was changed from +15 μA to +5 μA, and the potential at 15 μA (V L1 The photoconductor was charged and irradiated with monochromatic light in the same manner as in the measurement of the surface potential of the photoconductor. After the monochromatic light irradiation was completed, the photoconductor rotated two times and the surface potential of the photoconductor was measured. The measured surface potential was expressed as the potential at 5 μA (V L2 , unit: -V).

[0172] Equation: Transfer memory potential difference = (potential V at 5 μA) L2 )-(Potential V at 15μA L1 The transfer memory potential difference (unit: V) was calculated from the "transfer memory potential difference (V)." The suppression of transfer memory (transfer memory potential difference) was evaluated based on the following criteria.

[0173] A (good): The transfer memory potential difference is -10.0 V or more. B (bad): The transfer memory potential difference is less than -10.0V.

[0174] (Evaluation of abrasion resistance) The charge transport layer coating solution prepared in each Example or Comparative Example was applied to a polypropylene sheet (thickness: 0.3 mm) wrapped around an aluminum pipe (diameter: 78 mm). The applied charge transport layer coating solution was dried in an oven for 70 minutes to produce a polypropylene sheet on which a charge transport layer (film thickness: 30.00 μm) was formed. The oven heating conditions were a starting temperature of 60°C, a final temperature of 130°C, and a temperature increase rate of 1°C / min. The charge transport layer was then peeled off from the polypropylene sheet. The peeled charge transport layer was then attached to a card-shaped member ("S-36" manufactured by Taber). The mass MA of the card-shaped member with the attached charge transport layer was then measured. The card-shaped member with the attached charge transport layer was then attached to the turntable of a rotary abrasion tester (Toyo Seiki Seisakusho, Ltd.). Next, a 500 gf abrasive wheel ("CS-10" manufactured by Taber) was placed on the charge transport layer attached to the card-like member, and the turntable was rotated 1,000 times at a rotation speed of 60 rpm. In this manner, the charge transport layer on the turntable was abraded. After abrasion, the mass (MB) of the card-like member with the charge transport layer attached was measured. The abrasion loss (=MA-MB, unit: mg), which is the change in mass of the charge transport layer before and after abrasion, was then calculated. The abrasion resistance of the photoreceptor was evaluated from the abrasion loss based on the following criteria.

[0175] (Evaluation criteria for abrasion resistance) A (Good): The abrasion loss is 10.0 mg or less. B (poor): The abrasion loss exceeds 10.0 mg.

[0176] Table 4 also shows the evaluation results of filming resistance and scratch resistance, transfer memory potential difference, transfer memory suppression, abrasion loss, and abrasion resistance.

[0177] In Table 4, "resin" refers to polyarylate resin. The "type" of antioxidant refers to the type of compound used as the antioxidant in the corresponding example and comparative example. "AOX2" refers to a compound represented by formula (AOX2), and "AOX3" refers to a compound represented by formula (AOX3). Hereinafter, the compounds represented by formulas (AOX2) and (AOX3) may be referred to as compounds (AOX2) and (AOX3).

[0178] [ka]

[0179] In Table 4, the "amount" of antioxidant indicates the number of parts by mass of antioxidant per 100.00 parts by mass of polyarylate resin used. "Parts" indicates parts by mass. The content (number of parts by mass) of antioxidant in each charge transport layer coating solution per 100.00 parts by mass of polyarylate resin in each charge transport layer coating solution is maintained even after the charge transport layer is formed. "Filming / Scratch" indicates the evaluation results for filming resistance and scratch resistance. "Photosensitive layer formation impossible" indicates that the polyarylate resin was not dissolved in the solvent used to form the charge transport layer coating solution, making it impossible to prepare the charge transport layer coating solution, and therefore a photosensitive layer could not be formed, and the corresponding evaluation and measurement could not be performed. "-" indicates that the corresponding component was not used.

[0180] [Table 4]

[0181] As shown in Table 4, the photoreceptors (B-1) to (B-3) of Comparative Examples 1 to 3 contained a specific polyarylate resin (R-2), (R-7), or (R-3) containing repeating units (1) and (2) in the photosensitive layer. Furthermore, these photoreceptors (B-1) to (B-3) contained a hole transport agent and an antioxidant in the photosensitive layer. However, these photoreceptors (B-1) to (B-3) used compound (AOX2) or (AOX3) as the antioxidant, and did not contain the specific antioxidant compound (AOX1) in the photosensitive layer. The photoreceptors (B-1) to (B-3) had abrasion loss of more than 10.0 mg, and the evaluation results for abrasion resistance were "B" (poor).

[0182] As shown in Table 4, the photoreceptors (B-4) and (B-5) of Comparative Examples 4 and 5 contained a specific polyarylate resin (R-2) or (R-7) containing repeating units (1) and (2) and a hole transport agent in the photosensitive layer. However, these photoreceptors (B-4) and (B-5) did not contain an antioxidant in the photosensitive layer. These photoreceptors (B-4) and (B-5) had a transfer memory potential difference of less than -10.0 V, and the evaluation results for transfer memory suppression were "B" (poor).

[0183] As shown in Table 4, the photoreceptor (B-6) of Comparative Example 6 contained a specific antioxidant, compound (AOX1), in the photosensitive layer. Furthermore, the photoreceptor (B-6) contained a hole transport agent and a polyarylate resin in the photosensitive layer. However, the photoreceptor (B-6) used a polyarylate resin (r-1) that did not contain the repeating unit (2) as the polyarylate resin, and did not contain the specific polyarylate resin in the photosensitive layer. The photoreceptor (B-6) had at least filming on the surface of the photoreceptor, and image defects occurred in the second evaluation image. Therefore, the evaluation results for filming resistance and scratch resistance were "B" (poor). Furthermore, the abrasion loss of the photoreceptor (B-6) exceeded 10.0 mg, and the evaluation result for abrasion resistance was "B" (poor).

[0184] As shown in Table 4, the photoreceptor (B-7) of Comparative Example 7 did not contain an antioxidant in the photosensitive layer. Furthermore, the photoreceptor (B-7) used a polyarylate resin (r-2) that did not contain the repeating units (1) and (2) as the polyarylate resin, and did not contain a specific polyarylate resin in the photosensitive layer. The photoreceptor (B-7) had at least filming on the surface of the photoreceptor, and image defects occurred in the second evaluation image. Therefore, the evaluation results for filming resistance and scratch resistance were "B" (poor). Furthermore, the abrasion loss of the photoreceptor (B-7) exceeded 10.0 mg, and the evaluation result for abrasion resistance was "B" (poor).

[0185] As shown in Table 4, the photoreceptor (B-8) of Comparative Example 8 contained a specific antioxidant, compound (AOX1), in the photosensitive layer. Furthermore, the photoreceptor (B-8) contained a hole transport agent and a polyarylate resin in the photosensitive layer. However, the photoreceptor (B-8) used a polyarylate resin (r-2) that did not contain repeating units (1) and (2) as the polyarylate resin, and did not contain the specific polyarylate resin in the photosensitive layer. The photoreceptor (B-8) had at least filming on the surface of the photoreceptor, and image defects occurred in the second evaluation image. Therefore, the evaluation results for filming resistance and scratch resistance were "B" (poor). Furthermore, the transfer memory potential difference for the photoreceptor (B-8) was less than -10.0 V, and the evaluation result for transfer memory suppression was "B" (poor). In addition, the photoreceptor (B-8) had an abrasion loss of more than 10.0 mg, and the evaluation result of the abrasion resistance was "B" (poor).

[0186] As shown in Table 4, the photoreceptor (B-9) of Comparative Example 9 used compound (AOX2) as an antioxidant and did not contain compound (AOX1), which is a specific antioxidant. Furthermore, photoreceptor (B-9) used polyarylate resin (r-2) that did not contain repeating units (1) and (2) as the polyarylate resin, and did not contain the specific polyarylate resin in the photosensitive layer. For photoreceptor (B-9), at least filming occurred on the surface of the photoreceptor, and image defects occurred in the second evaluation image. Therefore, the evaluation results for filming resistance and scratch resistance were "B" (poor). Furthermore, for photoreceptor (B-9), the transfer memory potential difference was less than -10.0 V, and the evaluation result for transfer memory suppression was "B" (poor). Furthermore, for photoreceptor (B-9), the abrasion loss exceeded 10.0 mg, and the evaluation result for abrasion resistance was "B" (poor). The photoreceptor (B-9) had a larger abrasion loss than the photoreceptor (B-8) containing the compound (AOX1), which is a specific antioxidant, in the photosensitive layer.

[0187] As shown in Table 4, the photoreceptor (B-10) of Comparative Example 10 did not contain an antioxidant in the photosensitive layer. Furthermore, the photoreceptor (B-10) used a polyarylate resin (r-3) that did not contain the repeating unit (1) as the polyarylate resin, and did not contain a specific polyarylate resin in the photosensitive layer. Therefore, the transfer memory potential difference of the photoreceptor (B-10) was less than -10.0 V, and the evaluation result for the suppression of transfer memory was "B" (poor). Furthermore, the abrasion loss of the photoreceptor (B-10) exceeded 10.0 mg, and the evaluation result for the abrasion resistance was "B" (poor).

[0188] As shown in Table 4, the photoreceptor (B-11) of Comparative Example 11 contained a specific antioxidant, compound (AOX1), in the photosensitive layer. However, the photoreceptor (B-8) used a polyarylate resin (r-3) that did not contain the repeating unit (1) as the polyarylate resin, and did not contain the specific polyarylate resin in the photosensitive layer. The photoreceptor (B-11) had a transfer memory potential difference of less than -10.0 V, and the evaluation result for transfer memory suppression was "B" (poor). Furthermore, the photoreceptor (B-11) had an abrasion loss of more than 10.0 mg, and the evaluation result for abrasion resistance was "B" (poor).

[0189] As shown in Table 4, the photoreceptor (B-12) of Comparative Example 12 used the compound (AOX3) as the antioxidant and did not contain the specific antioxidant compound (AOX1). Furthermore, the photoreceptor (B-12) used a polyarylate resin (r-3) that did not contain the repeating unit (1) as the polyarylate resin, and did not contain the specific polyarylate resin in the photosensitive layer. The photoreceptor (B-12) had at least filming on the surface of the photoreceptor, and image defects occurred in the second evaluation image. Therefore, the evaluation results for filming resistance and scratch resistance were "B" (poor). Furthermore, the transfer memory potential difference of the photoreceptor (B-12) was less than -10.0 V, and the evaluation result for suppression of transfer memory was "B" (poor). Furthermore, the abrasion loss of the photoreceptor (B-12) exceeded 10.0 mg, and the evaluation result for abrasion resistance was "B" (poor). The photoreceptor (B-12) had a larger abrasion loss than the photoreceptor (B-8) containing the compound (AOX1), which is a specific antioxidant, in the photosensitive layer.

[0190] As shown in Table 4, in the production of the photoreceptor (B-13) of Comparative Example 13, no antioxidant was used, and the polyarylate resin used was a polyarylate resin (r-4) that did not contain the repeating unit (1). As described above, the polyarylate resin (r-4) was not dissolved in the solvent used to form the coating liquid for the charge transport layer, and a photosensitive layer could not be formed.

[0191] On the other hand, as shown in Table 4, the photosensitive layers of the photoreceptors (A-1) to (A-8) produced in Examples 1 to 8 contained one of the polyarylate resins (R-1) to (R-7), which are specific polyarylates containing repeating units (1) and (2), a hole transport agent, and a specific antioxidant compound (AOX1). All of the photoreceptors (A-1) to (A-8) were free of both scratches and filming, and were evaluated as "A" (particularly good) for filming resistance and scratch resistance. Furthermore, all of the photoreceptors (A-1) to (A-8) had a transfer memory potential difference of -10.0 or more and a wear loss of 10.0 mg or less, and were evaluated as "A" (good) for transfer memory suppression and wear resistance.

[0192] In particular, comparing Example 2 with Comparative Example 4, or Example 8 with Comparative Example 5, it is clear that the inclusion of the specific antioxidant in the photosensitive layer can sufficiently suppress transfer memory (in other words, the transfer memory resistance is improved). On the other hand, comparing Comparative Examples 7 and 8, or Comparative Examples 10 and 11, it is clear that the inclusion of the specific antioxidant in the photosensitive layer does not improve the transfer memory resistance, and that the effect of the specific antioxidant is only apparent when the photosensitive layer uses a specific polyarylate resin.

[0193] Furthermore, for example, a comparison between Example 1 and Example 3 reveals that when the specific polyarylate resin further contains, in addition to the repeating unit (1), for example, the repeating unit (P-4) as a repeating unit derived from bisphenol, a photoreceptor 1 having superior wear resistance and transfer memory suppression effects can be obtained.

[0194] Furthermore, for example, a comparison between Example 6 and Example 7 reveals that when the specific polyarylate resin further contains a repeating unit represented by formula (C-4) in addition to the repeating unit (2) as a repeating unit derived from a dicarboxylic acid, a photoreceptor 1 having superior wear resistance and transfer memory suppression effects can be obtained.

[0195] As described above, the photoreceptor of the present invention, including photoreceptors (A-1) to (A-8), has surface properties that can reduce wear on the photoreceptor surface and suppress the occurrence of filming, and can suppress the occurrence of transfer memory. Therefore, according to the present invention, it is possible to provide a photoreceptor that is excellent in wear resistance, filming resistance, and scratch resistance and can suppress transfer memory. Furthermore, by including the photoreceptor of the present invention, it is possible to provide a process cartridge and an image forming apparatus that are excellent in wear resistance, filming resistance, and scratch resistance and can suppress transfer memory. [Industrial Applicability]

[0196] The photoreceptor according to the present invention can be used in an image forming apparatus, and the process cartridge and image forming apparatus according to the present invention can be used to form an image on a recording medium. [Explanation of symbols]

[0197] 1: Electrophotographic photoreceptor 2: Conductive substrate 3: Photosensitive layer 3a: Charge generation layer 3b: Charge transport layer 3c: Single-layer photosensitive layer 4: Middle class 30: Image carrier 40a, 40b, 40c, 40d: image forming units 42: Charging device 44: Exposure equipment 46: Developing device 48: Transcription device 50: Transfer belt 52: Cleaning blade 54: Fixing device 100: Image forming device P: Recording medium

Claims

1. A conductive substrate and a photosensitive layer are provided. the photosensitive layer contains a polyarylate resin, a hole transport agent, and an antioxidant; The polyarylate resin contains a repeating unit represented by formula (1) and a repeating unit represented by formula (2), The electrophotographic photoreceptor, wherein the antioxidant is a compound represented by formula (AOX1): 【Chemical 1】 (In the formula (1), R 1 and R 2 each independently represents a hydrogen atom or a methyl group, and t represents an integer of 1 or more and 3 or less. 【Chemistry 2】 (In the formula (2), R 3 represents a divalent group represented by formula (X1), (X2) or (X3). 【Chemistry 3】 (In the formulas (X1), (X2), and (X3), * represents a bond.) 【Chemistry 4】

2. 2. The electrophotographic photoreceptor according to claim 1, wherein the repeating unit represented by formula (1) is a repeating unit represented by formula (P-1). 【Chemistry 5】

3. The electrophotographic photoreceptor according to claim 1 or 2, wherein the polyarylate resin further contains at least one of repeating units represented by formulas (P-2), (P-3), (P-4), (P-5), and (C-4). 【Chemistry 6】

4. The electrophotographic photoreceptor according to claim 1 or 2, wherein the hole transport agent has a triphenylamine structure.

5. 3. The electrophotographic photoreceptor according to claim 1, wherein the content of the antioxidant in the photosensitive layer is 1.00 parts by mass or more and 10.00 parts by mass or less with respect to 100.00 parts by mass of the polyarylate resin.

6. 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer comprises a charge generating layer containing a charge generating agent, and a charge transport layer containing the polyarylate resin, the hole transport agent, and the antioxidant.

7. 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 photosensitive member according to claim 1 or 2.

8. an image carrier; a charging device that charges the surface of the image carrier; 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 target, 3. An image forming apparatus, wherein the image bearing member is the electrophotographic photoreceptor according to claim 1.

9. 9. The image forming apparatus according to claim 8, wherein the image carrier is recharged by the charging device without being neutralized in an area where the toner image has been transferred to the transfer medium.

Images