Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that is less prone to image defects even when used under high-stress conditions, until the end of its lifespan. [Solution] The electrophotographic photoreceptor comprises a conductive substrate and a photosensitive layer disposed on the conductive substrate, wherein the outermost layer contains a charge transport material, a polyarylate resin having dicarboxylic acid units represented by formula (A) and diol units represented by formula (B), a polycarbonate resin, and a phenol compound having three or fewer phenolic functional groups and a molecular weight of 300 or more, and the dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is 0.50 or less. JPEG2026084595000049.jpg44109

Description

[Technical Field]

[0001] This disclosure relates to an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses an organic photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive support, wherein the dielectric constant ε of the charge transport layer at a frequency of 20 Hz is 3.4 or less, and the dielectric loss Tanδ at a frequency of 1 kHz is 0.001 to 0.03. Patent Document 2 discloses an electrophotographic photoreceptor in which the photosensitive layer contains a charge generating agent, a charge transporting agent, and a binder resin, and the binder resin contains a polyarylate resin and a polycarbonate resin. Patent Document 3 discloses an electrophotographic photoreceptor comprising a conductive substrate and a laminated photosensitive layer having a charge generation layer and a charge transport layer, wherein the charge transport layer contains a charge transport material, a polyarylate resin, and a polycarbonate resin.

[0003] Patent Document 4 discloses a cleaning blade in which the contact portion that comes into contact with the member to be cleaned contains polyurethane rubber obtained by polymerizing at least a polyol component and a polyisocyanate component, the ratio of 100% modulus M100 (MPa) to rebound modulus Re (%) M100 / Re is 0.25 or more, the rebound modulus Re is less than 25%, and the tensile stress at 200% strain is 15 MPa or more. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-131406 [Patent Document 2] Japanese Patent Publication No. 2017-125878 [Patent Document 3] Japanese Patent Publication No. 2024-011918 [Patent Document 4] Japanese Patent Publication No. 2023-106209 [Overview of the project] [Problems that the invention aims to solve]

[0005] The objective of this disclosure is to provide an electrophotographic photoreceptor that is less prone to image defects even when used under high-stress conditions, until the end of its lifespan. [Means for solving the problem]

[0006] The following embodiments are specific means for solving the aforementioned problem. Each formula is identical to the formula with the same number described later.

[0007] <1> The device comprises a conductive substrate and a photosensitive layer disposed on the conductive substrate, The outermost layer contains a charge transport material, a polyarylate resin having dicarboxylic acid units represented by formula (A) and diol units represented by formula (B), a polycarbonate resin, and a phenol compound having three or fewer phenolic functional groups and a molecular weight of 300 or more. The dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is 0.50 or less. Electrophotographic photoreceptor. <2> The dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is 0.40 or less. <1> The electrophotographic photoreceptor described above. <3> The phenol compound includes a phenol compound having two or fewer phenolic functional groups and a molecular weight of 350 or more. <1> or <2> The electrophotographic photoreceptor described above. <4> The dicarboxylic acid unit represented by formula (A) includes at least one selected from the group consisting of a dicarboxylic acid unit represented by formula (A1) (A1), a dicarboxylic acid unit represented by formula (A2) (A2), a dicarboxylic acid unit represented by formula (A3) (A3), a dicarboxylic acid unit represented by formula (A4) (A4), and a dicarboxylic acid unit represented by formula (A5) (A5). <1> ~ <3> An electrophotographic photoreceptor as described in any one of the following. <5> The diol unit represented by formula (B) includes at least one selected from the group consisting of a diol unit represented by formula (B1) (B1), a diol unit represented by formula (B2) (B2), a diol unit represented by formula (B3) (B3), a diol unit represented by formula (B4) (B4), a diol unit represented by formula (B5) (B5), a diol unit represented by formula (B6) (B6), a diol unit represented by formula (B7) (B7), and a diol unit represented by formula (B8) (B8). <1> ~ <4> An electrophotographic photoreceptor as described in any one of the following. <6> The polyarylate resin and the polycarbonate resin each have a constituent unit containing biphenyl represented by formula (BP). <1> ~ <5> An electrophotographic photoreceptor as described in any one of the following. <7> The proportion of polyarylate resin in the total amount of polyarylate resin and polycarbonate resin contained in the outermost layer is 25% by mass or more and 75% by mass or less. <1> ~ <6> An electrophotographic photoreceptor as described in any one of the following. <8> The photosensitive layer has a charge generation layer and a charge transport layer, and the charge transport layer is the outermost layer. <1> ~ <7> An electrophotographic photoreceptor as described in any one of the following. <9> <1> ~ <8> It comprises an electrophotographic photoreceptor as described in any one of the following: To be attached to and detached from the image forming apparatus, Process cartridge. <10> <1> ~ <8> An electrophotographic photoreceptor as described in any one of the following, A charging device for charging the surface of the electrophotographic photoreceptor, An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, A developing apparatus that develops an electrostatic latent image formed on the surface of an electrophotographic photoreceptor using a developer containing toner to form a toner image, The system includes a transfer device for transferring the toner image onto the surface of a recording medium. Image forming apparatus. <11> The device further comprises a cleaning device having a cleaning blade that contacts the surface of the electrophotographic photoreceptor, for cleaning the surface of the electrophotographic photoreceptor. <10> The image forming apparatus described above. <12> The contact portion of the cleaning blade that contacts the electrophotographic photoreceptor is made of a material containing polyurethane rubber polymerized from at least a polyol component and a polyisocyanate component, having a 100% modulus M100 (MPa) to rebound modulus Re (%) ratio M100 / Re of 0.25 or more, a rebound modulus Re of less than 25%, and a tensile stress of 15 MPa or more at 200% strain. <11> The image forming apparatus described above. <13> The ratio M100 / Re is 0.28 or more and 1.0 or less. <12> The image forming apparatus described above. [Effects of the Invention]

[0008] <1> , <4> , <5> , <6> , <7> or <8> According to this, compared to cases where the outermost layer does not contain phenol compounds with three or fewer phenolic functional groups but contains phenol compounds with four phenolic functional groups, or where the dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is greater than 0.50, an electrophotographic photoreceptor is provided that is less prone to image defects even when used under high stress conditions until the end of its lifespan. <2> According to this, compared to cases where the dielectric loss tangent tanδ value at a frequency of 1 Hz of the outermost layer is greater than 0.40, an electrophotographic photoreceptor is provided that is less prone to image defects even when used under high stress conditions, until the end of its lifespan. <3> According to this, compared to cases where the outermost layer does not contain a phenol compound with two phenol functional groups but contains a phenol compound with three phenol functional groups, an electrophotographic photoreceptor is provided that is less prone to image defects even when used under high stress conditions, until the end of its lifespan. <9> According to this, a process cartridge is provided that is less prone to image defects even when used under high stress conditions, up to the end of its lifespan, compared to cases where the outermost layer of the electrophotographic photoreceptor does not contain phenol compounds with three or fewer phenol functional groups but contains phenol compounds with four phenol functional groups, or where the dielectric loss tangent tanδ value of the outermost layer of the electrophotographic photoreceptor at a frequency of 1 Hz is greater than 0.50. <10> or <11> According to this, compared to cases where the outermost layer of the electrophotographic photoreceptor does not contain phenol compounds with three or fewer phenolic functional groups but contains phenol compounds with four phenolic functional groups, or where the dielectric loss tangent tanδ of the outermost layer of the electrophotographic photoreceptor at a frequency of 1 Hz is greater than 0.50, an image forming apparatus is provided that is less prone to image defects even when used under high stress conditions until the end of its lifespan. <12> According to this, compared to image forming apparatuses in which the cleaning blade has a ratio M100 / Re of less than 0.25, a rebound modulus Re of 25% or more, or a tensile stress of less than 15 MPa, an image forming apparatus is provided in which image defects are less likely to occur even when used under high stress conditions, until the end of its lifespan. <13> According to this, compared to image forming apparatuses with a cleaning blade ratio M100 / Re of less than 0.28 or greater than 1.0, an image forming apparatus is provided that is less prone to image defects even when used under high stress conditions, until the end of its lifespan. [Brief explanation of the drawing]

[0009] [Figure 1] This is a partial cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to the first embodiment. [Figure 2] This is a partial cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to the second embodiment. [Figure 3] This is a schematic diagram showing an example of an image forming apparatus according to this embodiment. [Figure 4] This is a schematic diagram showing another example of the image forming apparatus according to this embodiment. [Figure 5] This is a schematic diagram showing an example of a cleaning blade in this embodiment. [Figure 6] This is a schematic diagram showing another example of the cleaning blade in this embodiment. [Figure 7] This is a schematic diagram showing another example of the cleaning blade in this embodiment. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure are described below. These descriptions and embodiments are illustrative and do not limit the scope of the embodiments.

[0011] In this disclosure, the numerical range indicated using "~" represents a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples.

[0012] In this disclosure, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" may be A alone, or B alone, or a combination of A and B.

[0013] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that their objectives are achieved.

[0014] When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto.

[0015] In this disclosure, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this disclosure, if there are multiple types of the substance corresponding to each component in the composition, it means the total amount of those multiple types of substances present in the composition unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified.

[0016] In this disclosure, alkyl groups and alkylene groups include linear, branched, and cyclic groups unless otherwise specified. In this disclosure, organic groups, aromatic rings, linking groups, alkyl groups, alkylene groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, etc., may have hydrogen atoms in the group substituted with halogen atoms.

[0017] In this disclosure, when a compound is shown by its structural formula, the symbols representing carbon atoms and hydrogen atoms (C and H) in the hydrocarbon group and / or hydrocarbon chain may be omitted.

[0018] In this disclosure, the term "constituent unit" of a copolymer or resin is synonymous with "monomer unit."

[0019] <Electrophotographic photoconductor> The electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") according to this embodiment comprises a conductive substrate and a photosensitive layer disposed on the conductive substrate.

[0020] One example of a photoreceptor has a laminated photoreceptor layer in which a charge generating layer and a charge transport layer are stacked, with the charge transport layer being the outermost layer and the charge transport layer forming the outer surface of the photoreceptor. Another example of the embodiment of the photoreceptor is one having a single-layer photosensitive layer, where the single-layer photosensitive layer is the outermost layer and constitutes the outer surface of the photoreceptor.

[0021] Figure 1 is a schematic partial cross-sectional view showing an example of the layer structure of a photoreceptor according to this embodiment. The photoreceptor 10A shown in Figure 1 has a stacked photoreceptor layer. The photoreceptor 10A has a structure in which a base layer 2, a charge generation layer 3, and a charge transport layer 4 are stacked in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute the photoreceptor layer 5 (a so-called functionally separated photoreceptor layer). The photoreceptor 10A may have an intermediate layer (not shown) between the base layer 2 and the charge generation layer 3. The base layer 2 may or may not be present.

[0022] Figure 2 is a schematic partial cross-sectional view showing another example of the layer configuration of the photoreceptor according to this embodiment. The photoreceptor 10B shown in Figure 2 has a single-layer photosensitive layer. The photoreceptor 10B has a structure in which an undercoat layer 2 and a photosensitive layer 5 are stacked in that order on a conductive substrate 1. The photoreceptor 10B may have an intermediate layer (not shown) between the undercoat layer 2 and the photosensitive layer 5. The undercoat layer 2 may or may not be present.

[0023] The photoreceptor according to this embodiment has a top surface layer containing a charge transport material, a polyarylate resin having dicarboxylic acid units represented by formula (A) and diol units represented by formula (B) below, a polycarbonate resin, and a phenol compound having three or fewer phenolic functional groups and a molecular weight of 300 or more, and the dielectric loss tangent tanδ of the top surface layer at a frequency of 1 Hz is 0.50 or less.

[0024] [ka]

[0025] In equation (A), Ar A1 and Ar A2is an aromatic ring which may each independently have a substituent, and L A is a single bond or a divalent linking group, and n A1 is 0, 1 or 2. In formula (B), Ar B1 and Ar B2 are each independently an aromatic ring which may have a substituent, and L B is a single bond, an oxygen atom, a sulfur atom or -C(Rb 1 )(Rb 2 )-, and n B1 is 0, 1 or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may combine with each other to form a cyclic alkyl group.

[0026] In the present disclosure, a polyarylate resin having a dicarboxylic acid unit represented by formula (A) and a diol unit represented by formula (B) is referred to as "polyarylate resin (PA)", a dicarboxylic acid unit represented by formula (A) is referred to as "dicarboxylic acid unit (A)", and a diol unit represented by formula (B) is referred to as "diol unit (B)".

[0027] In the present disclosure, the phenol functional group of a phenol compound means a hydroxy group bonded to a benzene ring.

[0028] The photoreceptor according to the present embodiment is less likely to generate image defects even when used under high stress conditions until the end of its life. The mechanism is presumed as follows.

[0029] In the polyarylate resin (PA), resin molecules are bonded to each other by intermolecular forces due to the stacking of aromatic rings, improving the abrasion resistance of the outermost surface layer. However, polyarylate resins (PA) tend to have high molecular polarity, resulting in a relatively large dielectric loss tangent tanδ value at a frequency of 1 Hz for the outermost layer. A large dielectric loss tangent tanδ value at a frequency of 1 Hz for the outermost layer increases the degree of thermal vibration, which can lead to cracking in the outermost layer or accelerate oxidative degradation of the outermost layer. In contrast, the outermost layer containing polycarbonate resin has a relatively small dielectric loss tangent tanδ at a frequency of 1 Hz and therefore experiences less thermal vibration. However, it has inferior mechanical strength compared to the outermost layer containing polyarylate resin (PA), and is therefore prone to cracking. When polyarylate resin (PA) and polycarbonate resin are used in combination for the outermost layer, the dielectric loss tangent tanδ value at a frequency of 1 Hz of the outermost layer becomes appropriate, the degree of thermal vibration is suppressed, and cracking and oxidative degradation of the outermost layer are suppressed. Furthermore, while adding a phenolic antioxidant is effective in suppressing oxidative degradation of the outermost layer, in order to avoid increasing the dielectric loss tangent tanδ value of the outermost layer at a frequency of 1 Hz, the outermost layer contains a phenol compound with a molecular weight of 300 or more that mitigates the polarity of the phenolic functional groups, with three or fewer phenolic functional groups that are the source of molecular polarity. Therefore, the photoreceptor according to this embodiment is less prone to developing image defects even when used under high-stress conditions, right up to the end of its lifespan.

[0030] [Top surface layer] The outermost layer of the photoreceptor contains a charge transport material, polyarylate resin (PA), polycarbonate resin, and a phenol compound with three or fewer phenolic functional groups and a molecular weight of 300 or more, and the dielectric loss tangent tanδ at a frequency of 1 Hz is 0.50 or less.

[0031] The dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is measured by the following method. The outermost layer is peeled off from the photoreceptor. The peeled outermost layer is dissolved in tetrahydrofuran, coated onto an ITO substrate, and dried at 143°C for 30 minutes to form a 7 μm thick film. A gold electrode is formed on the outer surface of this film by vacuum deposition, and this is used as the measurement sample. Alternatively, a solution with the same component composition and solid content composition as the outermost layer (specifically, a coating solution used to form the outermost layer when manufacturing a photoreceptor) can be prepared, and this solution can be applied to an ITO substrate to form a film and gold electrode in the same manner as described above, which can then be used as a measurement sample. An impedance meter (for example, a Solartron 1260 impedance analyzer) is connected to the gold electrode and the ITO substrate, and impedance measurements are performed under the following conditions to determine the dielectric loss tangent tanδ at a frequency of 1 Hz. Measurement environment: Temperature 22°C, relative humidity 50% DC applied voltage: 0V AC applied voltage: ±1V Frequency: Sweep from 0.1Hz to 10kHz

[0032] From the viewpoint of suppressing degradation of the outermost layer, the value of the dielectric loss tangent tanδ at a frequency of 1 Hz is preferably as low as possible, preferably 0.40 or less, more preferably 0.35 or less, even more preferably 0.30 or less, and most preferably 0.25 or less.

[0033] The dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz can be controlled by the mixing ratio of polyarylate resin (PA) and polycarbonate resin, and the content of phenolic compounds. The mixing ratio of polyarylate resin (PA) and polycarbonate resin, and the content of phenolic compounds, are preferably within the ranges described later. Other control methods include increasing or decreasing the drying temperature and / or drying time when forming the outermost layer.

[0034] The charge transport material included in the outermost layer is the same compound as the charge transport material included in the charge transport layer described later, and the preferred compound is also the same.

[0035] From the viewpoint of controlling the dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz, the proportion of polyarylate resin (PA) to polycarbonate resin is preferably 20% to 80% by mass, more preferably 25% to 75% by mass, and even more preferably 30% to 70% by mass.

[0036] As the polycarbonate resin, a polycarbonate resin having continuous structural units with aromatic rings is preferred. In this polycarbonate resin, the resin molecules are bound together by intermolecular forces due to the stacking of aromatic rings, improving the abrasion resistance of the outermost layer. A preferred form of the polycarbonate resin is specifically the polycarbonate resin disclosed in Japanese Patent Application Publication No. 2023-121553. A more preferred form of the polycarbonate resin is the polycarbonate resin used in the examples described later.

[0037] As for the combination of polyarylate resin (PA) and polycarbonate resin, a combination of resins in which both have a structural unit containing biphenyl represented by the following formula (BP) is preferred.

[0038] [ka]

[0039] In equation (BP), j is an integer between 0 and 4, and j R 1 Each is independently either a methyl group or an ethyl group, k is an integer between 0 and 4, and there are k R 2 These are independently either a methyl group or an ethyl group.

[0040] The biphenyl represented by formula (BP) may be the entire structure or a part of the structure obtained by removing the ester bond (-C(=O)O-) or carbonate bond (-OC(=O)O-) from the constituent unit containing the biphenyl represented by formula (BP). In other words, the right and left ends of the biphenyl represented by formula (BP) may be independently directly bonded to an ester bond or a carbonate bond, or they may be bonded to an ester bond or a carbonate bond via other atoms or groups of atoms.

[0041] j is an integer between 0 and 4, preferably between 0 and 3, more preferably between 0 and 2, even more preferably 0 or 1, and particularly preferably 0. If j is an integer greater than or equal to 1, then j R 1 Each of these is independently a methyl group or an ethyl group, and a methyl group is preferred.

[0042] k is an integer between 0 and 4, preferably between 0 and 3, more preferably between 0 and 2, even more preferably 0 or 1, and particularly preferably 0. If k is an integer greater than or equal to 1, then k R 2 Each of these is independently a methyl group or an ethyl group, and a methyl group is preferred.

[0043] The biphenyl represented by formula (BP) is preferably 4,4'-biphenyl in terms of its linkage position in the main chain.

[0044] As for the combination of polyarylate resin (PA) and polycarbonate resin, a combination of polyarylate resin (PA) having at least one of dicarboxylic acid units (A2-3) and diol units (B7-1) and polycarbonate resin having constituent units (Cb7-1) is particularly preferred.

[0045] [ka]

[0046] From the viewpoint of suppressing molecular polarity, phenol compounds with three or fewer phenolic functional groups and a molecular weight of 300 or more are preferable to have a small number of phenolic functional groups and a large molecular weight. The number of phenolic functional groups in the phenol compound is 3 or less, preferably 1 or 2. The molecular weight of the phenol compound is 300 or more, preferably 350 or more, more preferably 400 or more, and even more preferably 450 or more. From the viewpoint of easy dispersion in the outermost layer, the upper limit of the molecular weight of the phenol compound is preferably 1000 or less, more preferably 900 or less, and even more preferably 800 or less. The phenol compound is preferably a phenol compound having two or fewer phenolic functional groups and a molecular weight of 350 or more, preferably a phenol compound having two or fewer phenolic functional groups and a molecular weight of 350 to 1000, more preferably a phenol compound having two or fewer phenolic functional groups and a molecular weight of 400 to 900, and even more preferably a phenol compound having two or fewer phenolic functional groups and a molecular weight of 450 to 800. In this disclosure, the phenolic functional group of a phenol compound means a hydroxyl group bonded to a benzene ring.

[0047] Hindered phenol compounds are examples of phenol compounds having three or fewer phenolic functional groups and a molecular weight of 300 or more. Hindered phenol compounds are generally compounds in which at least one of the ortho positions of the hydroxyl group of phenol is substituted with a bulky group, and are known to exhibit an antioxidant effect on compositions. Hindered phenol compounds may be used individually or in combination of two or more.

[0048] Examples of hindered phenol compounds include the following: • Alkylated monophenol compounds and their derivatives: for example, octyl-3,5-di-t-butyl-4-hydroxy-hydrocinnamate • Alkylthiomethylphenol compounds and their derivatives: For example, 2,4-dioctylthiomethyl-6-t-butylphenol, 2,4-dioctylthiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, 2,6-didodecylthiomethyl-4-nonylphenol • Alkylidenebisphenol compounds and their derivatives: e.g., 4,4'-Butylidenebis(6-t-butyl-3-methylphenol), 2,2'-Methylenebis(6-t-butyl-4-methylphenol), 2,2'-Methylenebis(6-t-butyl-4-ethylphenol), 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 3,9-bis[2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane

[0049] Commercially available hindered phenol compounds include ADEKA Corporation's "ADEKA Stab AO-80," "ADEKA Stab AO-50," "ADEKA Stab AO-40," "ADEKA Stab AO-30," "ADEKA Stab AO-20," and "ADEKA Stab AO-330," BASF Japan Ltd.'s "Irganox 245," "Irganox 1076," and "Irganox 1520," and Sumitomo Chemical Co., Ltd.'s "Sumilizer GA-80," "Sumilizer GM," and "Sumilizer GS."

[0050] The content of phenolic compounds in the outermost layer is preferably 0.1% to 20% by mass, more preferably 0.5% to 10% by mass, and even more preferably 1% to 5% by mass, based on the total mass of the outermost layer, from the viewpoint of promoting phase separation of two or more types of resins during the formation of the outermost layer and forming a fine phase separation structure in the outermost layer.

[0051] The outermost surface layer of the photoreceptor preferably contains 5% by mass or less of fluororesin particles, preferably 1% by mass or less, and more preferably 0% by mass (i.e., it does not contain fluororesin particles). Given the high likelihood of increased regulations on the manufacture and use of organofluorine compounds in the future, the above-mentioned range for the content of fluororesin particles is preferable.

[0052] The thickness of the outermost layer should be set according to the function of that layer. When the charge transport layer is the outermost layer, the thickness of the outermost layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 45 μm or less, and even more preferably 10 μm or more and 40 μm or less. When a single-layer photosensitive layer is the outermost layer, the thickness of the outermost layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 45 μm or less, and even more preferably 10 μm or more and 40 μm or less.

[0053] The method for forming the outermost layer is the same as the method for forming the charge transport layer and the single-layer photosensitive layer, which will be described later.

[0054] [Polyarylate resin (PA)] The polyarylate resin (PA) has at least dicarboxylic acid units (A) and diol units (B).

[0055] The dicarboxylic acid unit (A) is a constituent unit represented by the following formula (A).

[0056] [ka]

[0057] In equation (A), Ar A1 and Ar A2 Each of these is an aromatic ring which may independently have substituents, L A is a single bond or a divalent linking group, n A1 It is 0, 1, or 2.

[0058] ArA1 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0059] Ar A1 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. A1 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0060] Ar A2 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0061] Ar A2 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. A2 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0062] L A When it is a divalent linking group, the divalent linking group can be, for example, an oxygen atom, a sulfur atom, -C(Ra 1 )(Ra 2 )- is one example. Here, Ra 1 and Ra 2 Each of these is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, Ra 1 and Ra 2 These may be bonded together to form a cyclic alkyl group.

[0063] Ra 1 and Ra 2 The alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 or 2.

[0064] Ra 1 and Ra 2 The aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0065] Ra 1 and Ra 2 The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Ra 1 and Ra 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0066] The dicarboxylic acid unit (A) preferably includes at least one selected from the group consisting of dicarboxylic acid unit (A1) represented by formula (A1), dicarboxylic acid unit (A2) represented by formula (A2), dicarboxylic acid unit (A3) represented by formula (A3), dicarboxylic acid unit (A4) represented by formula (A4), and dicarboxylic acid unit (A5) represented by formula (A5). More preferably, the dicarboxylic acid unit (A) includes at least one selected from the group consisting of dicarboxylic acid unit (A2), dicarboxylic acid unit (A3), and dicarboxylic acid unit (A4), and even more preferably includes dicarboxylic acid unit (A2).

[0067] [ka]

[0068] In equation (A1), n 101 n is an integer between 0 and 4, and 101 Individual Ra 101 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 101 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0069] [ka]

[0070] In equation (A2), n 201 and n 202 Each of these is an independent integer between 0 and 4, and n 201 Individual Ra 201 and n 202 Individual Ra 202 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 201 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 202 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0071] [ka]

[0072] In equation (A3), n 301 and n 302 Each of these is an independent integer between 0 and 4, and n 301 Individual Ra 301 and n 302 Individual Ra 302Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 301 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 302 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0073] [ka]

[0074] In equation (A4), n 401 n is an integer between 0 and 6, and 401 Individual Ra 401 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 401 It is preferably an integer between 0 and 4, more preferably 0, 1, or 2, and even more preferably 0.

[0075] [ka]

[0076] In equation (A5), n 501 , n 502 and n 503 Each of these is an independent integer between 0 and 4, and n 501 Individual Ra 501 , n 502 Individual Ra 502 and n 503 Individual Ra 503 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 501is preferably 0, 1 or 2, more preferably 0 or 1, and still more preferably 0. n 502 is preferably 0, 1 or 2, more preferably 0 or 1, and still more preferably 0. n 503 is preferably 0, 1 or 2, more preferably 0 or 1, and still more preferably 0.

[0077] Ra of formula (A1) 101 , Ra of formula (A2) 201 and Ra 202 , Ra of formula (A3) 301 and Ra 302 , Ra of formula (A4) 401 as well as Ra of formula (A5) 501 , Ra 502 and Ra 503 Since the specific forms and preferred forms of Ra 101 , Ra 201 , Ra 202 , Ra 301 , Ra 302 , Ra 401 , Ra 501 , Ra 502 and Ra 503 will be collectively described as "Ra".

[0078] The alkyl group having 1 to 10 carbon atoms related to Ra may be linear, branched or cyclic. The number of carbon atoms of the alkyl group is preferably 1 to 6, more preferably 1 to 4, and still more preferably 1 or 2. [[ID=�3]] Examples of the linear alkyl group having 1 to 10 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, and n-decyl group. Examples of branched alkyl groups having 3 to 10 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, and the like. Examples of cyclic alkyl groups having 3 to 10 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl groups, as well as polycyclic alkyl groups (e.g., bicyclic, tricyclic, spirocyclic) formed by linking these monocyclic alkyl groups.

[0079] The aryl group with 6 to 12 carbon atoms related to Ra may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Examples of aryl groups having 6 to 12 carbon atoms include phenyl, biphenyl, 1-naphthyl, and 2-naphthyl groups.

[0080] The alkyl group in the alkoxy group having 1 to 6 carbon atoms related to Ra may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0081] Below are examples of dicarboxylic acid units (A1) (A1-1) to (A1-9). Dicarboxylic acid units (A1) are not limited to these examples.

[0082] [ka]

[0083] Below are examples of dicarboxylic acid units (A2) (A2-1) to (A2-3). Dicarboxylic acid units (A2) are not limited to these examples.

[0084] [ka]

[0085] The following are specific examples of dicarboxylic acid units (A3), namely (A3-1) and (A3-2). However, dicarboxylic acid units (A3) are not limited to these examples.

[0086] [ka]

[0087] Below are examples of dicarboxylic acid units (A4-1) to (A4-3). Dicarboxylic acid units (A4) are not limited to these examples.

[0088] [ka]

[0089] Below are examples of dicarboxylic acid units (A5), specifically (A5-1) to (A5-4). Dicarboxylic acid units (A5) are not limited to these examples.

[0090] [ka]

[0091] The dicarboxylic acid unit (A) preferably includes at least one selected from the group consisting of (A1-1), (A1-7), (A2-3), (A3-2), and (A4-3) as described above, more preferably includes at least one selected from the group consisting of (A2-3), (A3-2), and (A4-3), and even more preferably includes at least (A2-3).

[0092] The polyarylate resin (PA) may contain one or more dicarboxylic acid units (A).

[0093] The mass percentage of dicarboxylic acid units (A) in the polyarylate resin (PA) is preferably 15% by mass or more and 60% by mass or less. When the mass percentage of dicarboxylic acid units (A) is 15% by mass or more, the wear resistance of the outermost layer is good. From this viewpoint, the mass percentage of dicarboxylic acid units (A) is more preferably 20% by mass or more, and even more preferably 25% by mass or more. When the mass percentage of dicarboxylic acid units (A) is 60% by mass or less, peeling of the outermost layer can be suppressed. From this viewpoint, the mass percentage of dicarboxylic acid units (A) is more preferably 55% by mass or less, and even more preferably 50% by mass or less.

[0094] Polyarylate resin (PA) may contain dicarboxylic acid units other than dicarboxylic acid unit (A). Examples of other dicarboxylic acid units include aliphatic dicarboxylic acid units (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid), alicyclic dicarboxylic acid units (e.g., cyclohexanedicarboxylic acid), and lower alkyl ester units thereof (e.g., having 1 to 5 carbon atoms). The polyarylate resin (PA) may contain one or more of these dicarboxylic acid units.

[0095] The diol unit (B) is a constituent unit represented by the following formula (B).

[0096] [ka]

[0097] In equation (B), Ar B1 and Ar B2 Each of these is an aromatic ring which may independently have substituents, L B is a single bond, oxygen atom, sulfur atom or -C(Rb 1 )(Rb 2 )- and n B1 Rb is 0, 1, or 2. 1 and Rb 2 Each of these is independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 These may be bonded together to form a cyclic alkyl group.

[0098] Ar B1 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0099] Ar B1The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. B1 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0100] Ar B2 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0101] Ar B2 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. B2 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0102] Rb 1 and Rb 2 The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 18, more preferably 1 to 14, and even more preferably 1 to 10.

[0103] Rb 1 and Rb 2 The aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0104] Rb 1 and Rb 2The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Rb 1 and Rb 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0105] The diol unit (B) preferably includes at least one selected from the group consisting of the diol unit (B1) represented by formula (B1), the diol unit (B2) represented by formula (B2), the diol unit (B3) represented by formula (B3), the diol unit (B4) represented by formula (B4), the diol unit (B5) represented by formula (B5), the diol unit (B6) represented by formula (B6), the diol unit (B7) represented by formula (B7), and the diol unit (B8) represented by formula (B8).

[0106] The diol unit (B) more preferably includes at least one selected from the group consisting of the diol unit (B1) represented by the following formula (B1), the diol unit (B2) represented by the formula (B2), the diol unit (B4) represented by the formula (B4), the diol unit (B5) represented by the formula (B5), and the diol unit (B6) represented by the formula (B6). It is even more preferable to include at least one selected from the group consisting of a diol unit represented by the following formula (B1), a diol unit represented by the following formula (B2), a diol unit represented by the following formula (B5), and a diol unit represented by the following formula (B6): It is even more preferable to include at least one selected from the group consisting of a diol unit represented by the following formula (B1), a diol unit represented by the following formula (B2), and a diol unit represented by the following formula (B6): It is most preferable to contain at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1) and a diol unit (B2) represented by formula (B2).

[0107]

Chemical formula

[0108] In formula (B1), Rb 101 is a branched alkyl group having 4 to 20 carbon atoms, Rb 201 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, Rb 401 , Rb 501 , Rb 801 and Rb 901 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or a halogen atom.

[0109] Rb 101 The number of carbon atoms of the branched alkyl group having 4 to 20 carbon atoms related to is preferably 4 to 16, more preferably 4 to 12, and still more preferably 4 to 8. Specific examples of Rb 101 include isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, isododecyl group, sec-dodecyl group, tert-dodecyl group, tert-tetradecyl group, tert-pentadecyl group, etc.

[0110]

Chemical formula

[0111] In formula (B2), Rb 102Rb is a linear alkyl group having 4 to 20 carbon atoms. 202 Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 402 , Rb 502 , Rb 802 and Rb 902 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0112] Rb 102 The number of carbon atoms in the linear alkyl group having 4 to 20 carbon atoms is preferably 4 to 16, more preferably 4 to 12, and even more preferably 4 to 8. 102 Specific examples include n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, tridecyl group, n-tetradecyl group, n-pentadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-icosyl group, and the like.

[0113] [ka]

[0114] In equation (B3), Rb 113 and Rb 213 Each of these is independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, d is an integer between 7 and 15, and Rb 403 , Rb 503 , Rb 803 and Rb 903 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0115] Rb 113 and Rb 213 The number of carbon atoms in the linear alkyl group having 1 to 3 carbon atoms is preferably 1 or 2, and more preferably 1. Specific examples of this group include a methyl group, an ethyl group, and an n-propyl group. Rb 113 and Rb 213 The alkyl group in the alkoxy group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 4 carbon atoms is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Specific examples of the group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy groups. Rb 113 and Rb 213 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0116] [ka]

[0117] In equation (B4), Rb 104 and Rb 204 Each is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 404 , Rb 504 , Rb 804 and Rb 904 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0118] Rb 104 The alkyl group having 1 to 3 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or 2, and more preferably 1. Rb 104 Specific examples include methyl groups, ethyl groups, n-propyl groups, isopropyl groups, and cyclopropyl groups.

[0119] [ka]

[0120] In formula (B5), Ar 105 is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 205 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 405 , Rb 505 , Rb 805 and Rb 905 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or a halogen atom.

[0121] The aryl group having 6 to 12 carbon atoms related to Ar 105 may be either monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, more preferably 6. The alkyl group in the aralkyl group having 7 to 20 carbon atoms related to Ar 105 may be linear, branched or cyclic. The number of carbon atoms of the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 or 2. The aryl group in the aralkyl group having 7 to 20 carbon atoms related to Ar 105 may be either monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, more preferably 6. Examples of the aralkyl group having 7 to 20 carbon atoms include benzyl group, phenylethyl group, phenylpropyl group, 4-phenylbutyl group, phenylpentyl group, phenylhexyl group, phenylheptyl group, phenyloctyl group, phenylnonyl group, naphthylmethyl group, naphthylethyl group, anthracenylmethyl group, phenyl-cyclopentylmethyl group and the like.

[0122]

Chemical formula

[0123] In formula (B6), Rb 116 and Rb 216 are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or a halogen atom, e is an integer of 4 to 6, and Rb406 , Rb 506 , Rb 806 and Rb 906 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0124] Rb 116 and Rb 216 The number of carbon atoms in the linear alkyl group having 1 to 3 carbon atoms is preferably 1 or 2, and more preferably 1. Specific examples of this group include a methyl group, an ethyl group, and an n-propyl group. Rb 116 and Rb 216 The alkyl group in the alkoxy group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 4 carbon atoms is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Specific examples of the group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy groups. Rb 116 and Rb 216 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0125] [ka]

[0126] In equation (B7), Rb 407 , Rb 507 , Rb 807 and Rb 907 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0127] [ka]

[0128] In equation (B8), Rb 408 , Rb 508 , Rb 808 and Rb 908 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0129] Rb of equation (B1) 201 Rb of formula (B2) 202 Rb in formula (B4) 204 and Rb of formula (B5) 205 Since the specific form and preferred form are the same, hereinafter referred to as Rb 201 , Rb 202 , Rb 204 and Rb 205 to "Rb 200 They explain it collectively as "[...]."

[0130] Rb 200 The alkyl group having 1 to 3 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 or 2 carbon atoms, and more preferably 1 carbon atom. Examples of alkyl groups having 1 to 3 carbon atoms include methyl, ethyl, n-propyl, isopropyl, and cyclopropyl groups.

[0131] Rb of equation (B1) 401 Rb of formula (B2) 402 Rb of formula (B3) 403 Rb in formula (B4) 404 Rb in formula (B5) 405 Rb in formula (B6) 406 Rb in equation (B7) 407 and Rb of formula (B8) 408 Since the specific form and preferred form are the same, hereinafter referred to as Rb 401 , Rb 402 , Rb 403 , Rb 404 , Rb 405 , Rb 406 , Rb 407 and Rb 408 to "Rb 400 They explain it collectively as "[...]."

[0132] Rb 400 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0133] Rb 400 The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0134] Rb 400 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0135] Rb of equation (B1) 501 Rb of formula (B2) 502Rb of formula (B3) 503 Rb in formula (B4) 504 Rb in formula (B5) 505 Rb in formula (B6) 506 Rb in equation (B7) 507 and Rb of formula (B8) 508 Since the specific form and preferred form are the same, hereinafter referred to as Rb 501 , Rb 502 , Rb 503 , Rb 504 , Rb 505 , Rb 506 , Rb 507 and Rb 508 to "Rb 500 They explain it collectively as "[...]."

[0136] Rb 500 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0137] Rb 500 The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0138] Rb 500 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0139] Rb of equation (B1) 801 Rb of formula (B2) 802 Rb of formula (B3) 803 Rb in formula (B4) 804 Rb in formula (B5) 805 Rb in formula (B6) 806 Rb in equation (B7) 807 and Rb of formula (B8) 808 Since the specific form and preferred form are the same, hereinafter referred to as Rb 801 , Rb 802 , Rb 803 , Rb 804 , Rb 805 , Rb 806 , Rb 807 and Rb 808 to "Rb 800 They explain it collectively as "[...]."

[0140] Rb 800 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0141] Rb 800 The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0142] Rb 800 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0143] Rb of equation (B1) 901 Rb of formula (B2) 902 Rb of formula (B3) 903 Rb in formula (B4) 904 Rb in formula (B5) 905 Rb in formula (B6) 906 Rb in equation (B7) 907 and Rb of formula (B8) 908 Since the specific form and preferred form are the same, hereinafter referred to as Rb 901 , Rb 902 , Rb 903 , Rb 904 , Rb 905 , Rb 906 , Rb907 and Rb 908 to "Rb 900 They explain it collectively as "[...]."

[0144] Rb 900 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0145] Rb 900 The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0146] Rb 900 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0147] The following are specific examples of diol units (B1), specifically (B1-1) to (B1-6). Diol units (B1) are not limited to these examples.

[0148] [ka]

[0149] The following are specific examples of diol units (B2), specifically (B2-1) to (B2-11). Diol units (B2) are not limited to these examples.

[0150] [ka]

[0151] The following are specific examples of diol units (B3), namely (B3-1) to (B3-4). Diol units (B3) are not limited to these examples.

[0152] [ka]

[0153] The following are examples of diol units (B4-1) to (B4-7). Diol units (B4) are not limited to these examples.

[0154] [ka]

[0155] The following are examples of diol units (B5-1) to (B5-6). Diol units (B5) are not limited to these examples.

[0156] [ka]

[0157] The following are specific examples of diol units (B6), namely (B6-1) to (B6-4). Diol units (B6) are not limited to these examples.

[0158] [ka]

[0159] The following are examples of diol units (B7-1) to (B7-3). Diol units (B7) are not limited to these examples.

[0160] [ka]

[0161] The following are specific examples of diol units (B8), namely (B8-1) to (B8-3). Diol units (B8) are not limited to these examples.

[0162] [ka]

[0163] The diol units (B) contained in the polyarylate resin (PA) may be one type or two or more types.

[0164] The mass percentage of diol units (B) in the polyarylate resin (PA) is preferably 25% by mass or more and 80% by mass or less. When the mass percentage of diol units (B) is 25% by mass or more, peeling of the outermost layer can be suppressed. From this viewpoint, a mass percentage of diol units (B) of 30% by mass or more is more preferable, and 35% by mass or more is even more preferable. When the mass percentage of diol units (B) is 80% by mass or less, it is possible to maintain solubility in the coating solution for forming the outermost layer and improve wear resistance. From this viewpoint, the mass percentage of diol units (B) is more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0165] Polyarylate resin (PA) may contain other diol units besides diol unit (B). Examples of other diol units include aliphatic diol units (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) and alicyclic diol units (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A). The polyarylate resin (PA) may contain one or more of these diol units.

[0166] The ends of the polyarylate resin (PA) may be sealed or modified with end-capping agents or molecular weight modifiers used during manufacturing. Examples of end-capping agents or molecular weight modifiers include monohydric phenols, monohydric acid chlorides, monohydric alcohols, and monohydric carboxylic acids. Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m Examples include -phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, and 2-phenyl-2-(3-hydroxyphenyl)propane. Examples of monovalent acid chlorides include monofunctional acid halides such as benzoyl chloride, methanesulfonyl chloride, phenyl chloroformate, acetate chloride, butyrate chloride, octylate chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and their substituted derivatives. Examples of monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenethyl alcohol. Examples of monocarboxylic acids include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0167] The weight-average molecular weight of the polyarylate resin (PA) is preferably 30,000 to 300,000, more preferably 40,000 to 250,000, and even more preferably 50,000 to 200,000. The molecular weight of polyarylate resin (PA) is the molecular weight in polystyrene equivalent, measured by GPC (gel permeation chromatography). Tetrahydrofuran is used as the eluent in GPC.

[0168] Polyarylate resins (PA) can be obtained by polycondensation of monomers that give dicarboxylic acid units (A) and monomers that give diol units (B), along with other monomers as needed, using conventional methods. Methods for the polycondensation of monomers include interfacial polymerization, solution polymerization, and melt polymerization. Interfacial polymerization is a polymerization method that obtains polyester by mixing a divalent carboxylic acid halide dissolved in an organic solvent immiscible with water with a divalent alcohol dissolved in an alkaline aqueous solution. Literature on interfacial polymerization includes WMERECKSON, J. Poly. Sci., XL399, 1959, and Japanese Patent Publication No. 40-1959. Because interfacial polymerization is faster than solution polymerization, it can suppress the hydrolysis of divalent carboxylic acid halides, resulting in the acquisition of high molecular weight polyarylate resins (PA).

[0169] The following provides a detailed explanation of each layer of the photoreceptor.

[0170] [Conductive substrate] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Other examples of conductive substrates include paper, resin films, and belts coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys. Here, "conductive" refers to a volume resistivity of 1 × 10⁻⁶. 13 This refers to a value less than Ω·cm.

[0171] When an electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center-line average roughness Ra of 0.04 μm to 0.5 μm in order to suppress interference fringes that occur when irradiated with laser light. When non-interfering light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for a longer lifespan because it suppresses the occurrence of defects due to surface irregularities of the conductive substrate.

[0172] Methods for roughening a surface include, for example, wet honing, which involves suspending an abrasive in water and spraying it onto a conductive substrate; centerless grinding, which involves pressing a conductive substrate against a rotating grinding wheel and continuously grinding it; and anodizing.

[0173] One method for roughening the surface is to disperse conductive or semiconductive powder in a resin without roughening the surface of the conductive substrate, to form a layer on the surface of the conductive substrate, and then roughen the surface with the particles dispersed in that layer.

[0174] Anodizing roughening treatment involves forming an oxide film on the surface of a conductive substrate (e.g., aluminum) by anodizing it in an electrolyte solution. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film to block the micropores of the oxide film by volume expansion due to a hydration reaction using pressurized steam or boiling water (metal salts such as nickel may be added), thereby converting it into a more stable hydrated oxide.

[0175] The thickness of the anodic oxide film is preferably, for example, 0.3 μm to 15 μm. When the film thickness is within this range, it tends to exhibit barrier properties against injection and tends to suppress the increase in residual potential due to repeated use.

[0176] The conductive substrate may be treated with an acidic treatment solution or with boehmite. Treatment with an acidic solution is carried out, for example, as follows: First, an acidic solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic solution is, for example, in the range of 10% to 11% by mass for phosphoric acid, 3% to 5% by mass for chromic acid, and 0.5% to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness is preferably 0.3 μm to 15 μm.

[0177] The boehmite treatment is carried out, for example, by immersing the material in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting it with heated steam at 90°C to 120°C for 5 to 60 minutes. The film thickness is preferably 0.1 μm to 5 μm. This can be further treated with anodic oxidation using an electrolyte solution with low film solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0178] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0179] As for inorganic particles, for example, powder resistance (volume resistivity) 1 × 10 2 Ω cm or more 1×10 11 Examples include inorganic particles with a size of Ω·cm or less. Among these, suitable inorganic particles having the above-mentioned resistance values ​​include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0180] The specific surface area of ​​inorganic particles using the BET method is, for example, 10 m². 2 A value of 1g or more is preferable. The volume-average particle size of the inorganic particles is preferably between 50 nm and 2000 nm (preferably between 60 nm and 1000 nm).

[0181] The inorganic particle content is preferably 10% by mass or more and 80% by mass or less relative to the binder resin, and more preferably 40% by mass or more and 80% by mass or less.

[0182] The inorganic particles may be surface-treated. Two or more types of inorganic particles with different surface treatments or particle sizes may be mixed and used.

[0183] Examples of surface treatment agents include silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, and surfactants. Silane coupling agents are particularly preferred, and silane coupling agents having an amino group are more preferred.

[0184] Examples of silane coupling agents having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0185] Silane coupling agents may be used in combination of two or more types. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0186] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry or wet method.

[0187] The amount of surface treatment agent applied is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0188] In this case, it is preferable for the underlayer to contain electron-accepting compounds (acceptor compounds) along with inorganic particles, from the viewpoint of improving the long-term stability of electrical properties and carrier blocking ability.

[0189] Examples of electron-accepting compounds include electron-transporting substances such as: compounds having an anthraquinone structure; quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone; and benzophenone compounds such as 4-hydroxybenzophenone and 2,3,4-trihydroxybenzophenone. In particular, compounds having an anthraquinone structure are preferred as electron-accepting compounds. Examples of compounds having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds. Specifically, examples of preferred compounds include anthraquinone, alizarin, quinizarin, anthralphine, purpurin, 4-ethoxy-1,2-hydroxy-9,10-anthraquinone, and their derivatives.

[0190] The electron-accepting compound may be dispersed in the underlayer together with inorganic particles, or it may be present attached to the surface of the inorganic particles.

[0191] Methods for attaching electron-accepting compounds to the surface of inorganic particles include, for example, dry methods or wet methods.

[0192] The dry method involves, for example, adding an electron-accepting compound, either directly or dissolved in an organic solvent, dropwise while stirring inorganic particles with a mixer that has a high shear force, or spraying it with dry air or nitrogen gas, to adhere the electron-accepting compound to the surface of the inorganic particles. When adding or spraying the electron-accepting compound, it is preferable to do so at a temperature below the boiling point of the solvent. After adding or spraying the electron-accepting compound, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained.

[0193] The wet method involves dispersing inorganic particles in a solvent using, for example, a stirrer, ultrasonic disperser, sand mill, attritor, or ball mill, while adding an electron-accepting compound. After stirring or dispersion, the solvent is removed, and the electron-accepting compound adheres to the surface of the inorganic particles. Solvent removal methods include, for example, filtration or distillation. After solvent removal, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained. In the wet method, the water content of the inorganic particles may be removed before adding the electron-accepting compound. Examples of this include removing water while stirring and heating in the solvent, or removing water by azeotrope with the solvent.

[0194] The electron-accepting compound may be applied before or after surface treatment with a surface treatment agent to the inorganic particles, or it may be applied simultaneously with the surface treatment with the surface treatment agent.

[0195] The content of the electron-accepting compound is preferably, for example, 0.01% by mass or more and 20% by mass or less relative to the inorganic particles, and more preferably 0.01% by mass or more and 10% by mass or less.

[0196] Examples of known polymer compounds used as the binder resin for the undercoat include acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, unsaturated polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, alkyd resin, epoxy resin, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Examples of binder resins used in the undercoat include charge-transporting resins having charge-transporting groups, conductive resins (e.g., polyaniline), and the like.

[0197] Among these, a resin insoluble in the coating solvent of the upper layer is preferred as the binder resin used for the undercoat layer. In particular, a resin obtained by the reaction of a curing agent with at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin is preferred. When using two or more of these binder resins in combination, the mixing ratio is set as needed.

[0198] The undercoat may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of known additives include electron-transporting pigments such as polycyclic condensation and azo pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. As mentioned above, silane coupling agents are used for surface treatment of inorganic particles, but they may also be added to the undercoat as additives.

[0199] Examples of silane coupling agents used as additives include vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0200] Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0201] Examples of titanium chelate compounds include tetraisopropyl titanate, tetran-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0202] Examples of aluminum chelating compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0203] These additives may be used individually or as a mixture or polycondensate of multiple compounds.

[0204] The underlayer should ideally have a Vickers hardness of 35 or higher. The surface roughness (ten-point average roughness) of the undercoat layer should be adjusted to between 1 / (4n) (where n is the refractive index of the upper layer) and 1 / 2 of the exposure laser wavelength λ used, in order to suppress moiré patterns. Resin particles may be added to the undercoat to adjust the surface roughness. Examples of resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. The surface of the undercoat may also be polished to adjust the surface roughness. Polishing methods include buffing, sandblasting, wet honing, and grinding.

[0205] The formation of the undercoat is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of an undercoat-forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0206] Solvents for preparing the coating solution for forming the undercoat include known organic solvents such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0207] Known methods for dispersing inorganic particles when preparing a coating solution for forming an undercoat include, for example, roll mills, ball mills, vibrating ball mills, attritors, sand mills, colloid mills, and paint shakers.

[0208] Conventional methods for applying the undercoating solution onto a conductive substrate include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0209] The thickness of the undercoat layer is preferably set to a range of 15 μm or more, and more preferably within the range of 20 μm to 50 μm.

[0210] [Middle class] The intermediate layer is, for example, a layer containing a resin. Examples of resins used in the intermediate layer include polymer compounds such as acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, and melamine resin. The intermediate layer may contain an organometallic compound. Examples of organometallic compounds used in the intermediate layer include those containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in these intermediate layers may be used individually, as a mixture of multiple compounds, or as polycondensates.

[0211] Among these, the intermediate layer is preferably a layer containing an organometallic compound that contains zirconium atoms or silicon atoms.

[0212] The formation of the intermediate layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of an intermediate layer-forming coating solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary. Conventional methods such as immersion coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating are used to form the intermediate layer.

[0213] The thickness of the intermediate layer is preferably set in the range of 0.1 μm to 3 μm. The intermediate layer may also be used as a base layer.

[0214] [Charge generation layer] The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Alternatively, the charge generation layer may be a vapor-deposited layer of the charge generation material. A vapor-deposited layer of the charge generation material is suitable when using non-coherent light sources such as LEDs (Light Emitting Diodes) or organic EL (Electro-Luminescence) image arrays.

[0215] Examples of charge-generating materials include azo pigments such as bisazo and trisazo; fused aromatic pigments such as dibromoanthonthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0216] Among these, in order to accommodate laser exposure in the near-infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material. Specifically, for example, hydroxygallium phthalocyanine; chlorogallium phthalocyanine; dichlorotin phthalocyanine; and titanyl phthalocyanine are more preferable.

[0217] On the other hand, to accommodate laser exposure in the near-ultraviolet region, preferred charge-generating materials include fused aromatic pigments such as dibromoanthoten; thioindigo pigments; porphyrazine compounds; zinc oxide; trigonal selenium; and bisazo pigments.

[0218] The above charge generating material may also be used when using non-coherent light sources such as LEDs and organic EL image arrays, which have a central emission wavelength between 450 nm and 780 nm.

[0219] When n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark currents are less likely to be generated, and image defects called black spots can be suppressed even in thin films. The n-type is determined using the commonly used time-of-flight method, which is determined by the polarity of the photocurrent that flows, and materials that readily carry electrons as carriers rather than holes are classified as n-type.

[0220] The binder resin used in the charge generation layer can be selected from a wide range of insulating resins, or it may be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (such as polycondensates of bisphenols and aromatic divalent carboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinylpyrrolidone resin. Here, "insulating properties" refer to a volume resistivity of 1 × 10⁻⁶. 13This refers to a density of Ω·cm or greater. These binder resins can be used individually or in mixtures of two or more types.

[0221] The mixing ratio of the charge-generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass ratio.

[0222] The charge generation layer may also contain other known additives.

[0223] The formation of the charge generation layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of a coating solution for forming a charge generation layer by adding the above components to a solvent, drying the coating film, and heating it as necessary. The charge generation layer may also be formed by vapor deposition of a charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when using fused ring aromatic pigments or perylene pigments as the charge generation material.

[0224] Solvents for preparing the coating solution for forming the charge generation layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene. These solvents may be used individually or in mixtures of two or more.

[0225] Methods for dispersing particles (e.g., charge-generating material) in a coating solution for forming a charge-generating layer include, for example, media dispersers such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, as well as media-less dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include collision methods, in which the dispersion is dispersed by liquid-liquid collisions or liquid-wall collisions under high pressure, and penetration methods, in which the dispersion is dispersed by penetrating fine channels under high pressure. During dispersion, it is effective to set the average particle size of the charge-generating material in the coating solution for forming the charge-generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0226] Conventional methods for applying the charge-generating layer forming coating solution onto the undercoat (or intermediate layer) include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0227] The thickness of the charge generation layer is preferably set within the range of 0.1 μm to 5.0 μm, and more preferably within the range of 0.2 μm to 2.0 μm.

[0228] [Charge transport layer] The charge transport layer is, for example, a layer containing a binder resin and a charge transport material. The charge transport layer may also be a layer containing a polymer charge transport material.

[0229] Examples of charge transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds, which are electron transport compounds. Other examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used individually or in combination of two or more, but are not limited to these.

[0230] Examples of polymeric charge transport materials include known chemical substances with charge transport properties such as poly-N-vinylcarbazole and polysilane. For example, polyester-based polymeric charge transport materials are preferred. Polymeric charge transport materials may be used alone or in combination with a binder resin.

[0231] Examples of charge transport materials or polymeric charge transport materials include polycyclic aromatic compounds, aromatic nitro compounds, aromatic amine compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds (especially triphenylamine compounds), diamine compounds, oxadiazole compounds, carbazole compounds, organic polysilane compounds, pyrazoline compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, cyano compounds, benzofuran compounds, aniline compounds, butadiene compounds, and resins having groups derived from these substances. Specifically, paragraphs 0078-0080 of JP 2021-117377, paragraphs 0046-0048 of JP 2019-035900, paragraphs 0052-0053 of JP 2019-012141, paragraphs 0122-0134 of JP 2021-071565, and paragraph 0078-0080 of JP 2021-015223 Examples of compounds include those described in paragraphs 0101-0110, paragraph 0116 of Japanese Patent Publication No. 2013-097300, paragraphs 0309-0316 of International Publication No. 2019 / 070003, paragraphs 0103-0107 of Japanese Patent Publication No. 2018-159087, and paragraphs 0102-0113 of Japanese Patent Publication No. 2021-148818.

[0232] From the viewpoint of charge mobility, the charge transport material preferably contains at least one selected from the group consisting of a chemical substance (C1) represented by the following formula (C1), a chemical substance (C2) represented by the formula (C2), a chemical substance (C3) represented by the formula (C3), and a chemical substance (C4) represented by the formula (C4).

[0233] [ka]

[0234] In equation (C1), Ar T1 Ar T2 and Ar T3 Each is independently an aryl group, -C6H4-C(R T4 )=C(RT5 )(R T6 ) or -C6H4-CH=CH-CH=C(R T7 )(R T8 ) is R T4 , R T5 , R T6 , R T7 and R T8 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T5 and R T6 When it is an aryl group, the aryl groups are -C(R 51 )(R 52 )-and / or-C(R 61 )=C(R 62 )- may be linked by a divalent group. R 51 , R 52 , R 61 and R 62 Each of these is independently either a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0235] The group in formula (C1) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0236] As for the chemical substance (C1), from the viewpoint of charge mobility, it is an aryl group or -C6H4-CH=CH-CH=C(R T7 )(R T8 A chemical substance having at least one of the following is preferred, and a chemical substance (C'1) represented by the following formula (C'1) is more preferred.

[0237] [ka]

[0238] In equation (C'1), R T111 , R T112 , R T121 , R T122 , R T131 and R T132Each of these is independently a hydrogen atom, a halogen atom, an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 3 carbon atoms), a phenyl group, or a phenoxy group. Tj1, Tj2, Tj3, Tk1, Tk2, and Tk3 are each independently 0, 1, or 2.

[0239] [ka]

[0240] In equation (C2), R T201 , R T202 , R T211 and R T212 Each of these is independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, and -C(R T21 )=C(R T22 )(R T23 ) or -CH=CH-CH=C(R T24 )(R T25 ) is R T21 , R T22 , R T23 , R T24 and R T25 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T221 and R T222 Each of these is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. Tm1, Tm2, ​​Tn1, and Tn2 are each independently 0, 1, or 2.

[0241] The group in formula (C2) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0242] As for the chemical substance (C2), from the viewpoint of charge mobility, alkyl groups, aryl groups, or -CH=CH-CH=C(R T24 )(R T25A chemical substance having at least one alkyl group, aryl group, or -CH=CH-CH=C(R T24 )(R T25 A chemical substance having two of these is more preferable.

[0243] [ka]

[0244] In equation (C3), R T301 , R T302 , R T311 and R T312 Each of these is independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, and -C(R T31 )=C(R T32 )(R T33 ) or -CH=CH-CH=C(R T34 )(R T35 ) is R T31 , R T32 , R T33 , R T34 and R T35 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T321 , R T322 and R T331 Each of these is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. To1, To2, Tp1, Tp2, Tq1, Tq2, and Tr1 are each independently 0, 1, or 2.

[0245] The group in formula (C3) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0246] [ka]

[0247] In equation (C4), R T401 , R T402 , R T411 and R T412 Each of these is independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, and -C(R T41 )=C(R T42 )(R T43 ) or -CH=CH-CH=C(R T44 )(R T45 ) is R T41 , R T42 , R T43 , R T44 and R T45 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T421 , R T422 and R T431 Each of these is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 are each independently 0, 1, or 2.

[0248] The group in formula (C4) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0249] Examples of binder resins used in the charge transport layer include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, and polysilane. Among these, polycarbonate resin or polyarylate resin is preferred as the binder resin. These binder resins can be used individually or in combination of two or more. The preferred mixing ratio of the charge transport material to the binder resin is between 10:1 and 1:5 by mass.

[0250] When the charge transport layer is the outermost layer of the photoreceptor, the charge transport layer contains at least a polyarylate resin (PA) and a polycarbonate resin. Preferably, the combination of polyarylate resin (PA) and polycarbonate resin is one in which both resins have a structural unit containing biphenyl represented by formula (BP).

[0251] When the charge transport layer is the outermost layer of the photoreceptor, the charge transport layer contains a phenol compound having three or fewer phenolic functional groups and a molecular weight of 300 or more. The preferred form of the phenol compound is as described above.

[0252] The charge transport layer may also contain other known additives.

[0253] The formation of the charge transport layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of a charge transport layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0254] Suitable solvents for preparing the coating solution for forming the charge transport layer include common organic solvents such as aromatic hydrocarbons like benzene, toluene, xylene, and chlorobenzene; ketones like acetone and 2-butanone; halogenated aliphatic hydrocarbons like methylene chloride, chloroform, and ethylene chloride; and cyclic or linear ethers like tetrahydrofuran and ethyl ether. These solvents can be used individually or in mixtures of two or more.

[0255] Conventional methods for applying a charge transport layer forming coating solution onto a charge generation layer include blade coating, wire bar coating, spray coating, immersion coating, bead coating, air knife coating, and curtain coating.

[0256] The thickness of the charge transport layer is preferably set within the range of 5 μm to 50 μm, more preferably 8 μm to 45 μm, and even more preferably 10 μm to 40 μm.

[0257] [Single-layer photosensitive layer] A single-layer photosensitive layer (charge generation / charge transport layer) is, for example, a layer comprising a charge generation material, a charge transport material, and optionally a binder resin and other known additives. These materials are the same as those described for the charge generation layer and the charge transport layer. In the single-layer photosensitive layer, the content of the charge-generating material is preferably 0.1% to 10% by mass relative to the total solid content, and more preferably 0.8% to 5% by mass. In addition, the content of the charge-transporting material in the single-layer photosensitive layer is preferably 5% to 50% by mass relative to the total solid content. The method for forming a single-layer photosensitive layer is the same as the method for forming a charge generation layer or a charge transport layer. The thickness of the single-layer photosensitive layer is preferably set within the range of 5 μm to 50 μm, more preferably 8 μm to 45 μm, and even more preferably 10 μm to 40 μm.

[0258] When the single-layer photosensitive layer is the outermost layer of the photoreceptor, the single-layer photosensitive layer contains at least a polyarylate resin (PA) and a polycarbonate resin. Preferably, the combination of polyarylate resin (PA) and polycarbonate resin is one in which both resins have a structural unit containing biphenyl represented by formula (BP).

[0259] When the single-layer photosensitive layer is the outermost layer of the photoreceptor, the single-layer photosensitive layer contains a phenol compound having three or fewer phenolic functional groups and a molecular weight of 300 or more. The preferred form of the phenol compound is as described above.

[0260] <Image forming apparatus, process cartridge> The image forming apparatus according to this embodiment comprises an electrophotographic photoreceptor, a charging device for charging the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, and a transfer device for transferring the toner image to the surface of a recording medium. The electrophotographic photoreceptor according to this embodiment is used as the electrophotographic photoreceptor.

[0261] One example of an embodiment of the image forming apparatus according to this embodiment includes a cleaning device that has a cleaning blade that contacts the surface of an electrophotographic photoreceptor and cleans the surface of the electrophotographic photoreceptor. The cleaning device cleans the surface of the photoreceptor with the cleaning blade after the toner image has been transferred and before it has been charged.

[0262] The image forming apparatus according to this embodiment includes known image forming apparatuses such as: an apparatus equipped with a fixing device for fixing a toner image transferred to the surface of a recording medium; a direct transfer apparatus for directly transferring a toner image formed on the surface of an electrophotographic photoreceptor to a recording medium; an intermediate transfer apparatus for first transferring a toner image formed on the surface of an electrophotographic photoreceptor to the surface of an intermediate transfer body, and secondarily transferring the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium; an apparatus equipped with a static elimination device for irradiating the surface of the electrophotographic photoreceptor with static elimination light to eliminate static charge after the transfer of the toner image and before charging; and an apparatus equipped with an electrophotographic photoreceptor heating member for raising the temperature of the electrophotographic photoreceptor and reducing the relative temperature.

[0263] In the case of an intermediate transfer method apparatus, the transfer apparatus may be configured to include, for example, an intermediate transfer body on which a toner image is transferred; a primary transfer apparatus that first transfers the toner image formed on the surface of an electrophotographic photoreceptor to the surface of the intermediate transfer body; and a secondary transfer apparatus that secondarily transfers the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium.

[0264] The image forming apparatus according to this embodiment may be either a dry developing type image forming apparatus or a wet developing type image forming apparatus (a developing method using a liquid developer).

[0265] In the image forming apparatus according to this embodiment, for example, the portion comprising the electrophotographic photoreceptor may be a cartridge structure (process cartridge) that can be attached to and detached from the image forming apparatus. As the process cartridge, for example, a process cartridge comprising the electrophotographic photoreceptor according to this embodiment is preferably used. In addition to the electrophotographic photoreceptor, the process cartridge may also include at least one selected from the group consisting of, for example, a charging device, an electrostatic latent image forming device, a developing device, and a transfer device.

[0266] The following is an example of an image forming apparatus according to this embodiment, but it is not limited to this example. The main parts shown in the figure will be described, and the descriptions of other parts will be omitted.

[0267] Figure 3 is a schematic diagram showing an example of an image forming apparatus according to this embodiment. As shown in Figure 3, the image forming apparatus 100 according to this embodiment includes a process cartridge 300 equipped with an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming apparatus), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is positioned to expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, and the transfer device 40 is positioned facing the electrophotographic photoreceptor 7 via the intermediate transfer body 50, with a portion of the intermediate transfer body 50 in contact with the electrophotographic photoreceptor 7. Although not shown, the apparatus also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) are examples of transfer devices.

[0268] In Figure 3, the process cartridge 300 integrally supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging device), a developing device 11 (an example of a developing device), and a cleaning device 13 (an example of a cleaning device) within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is positioned to contact the surface of the electrophotographic photoreceptor 7. The cleaning member may be a conductive or insulating fibrous member, rather than a cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

[0269] Figure 3 shows an example of an image forming apparatus that includes a fibrous member 132 (roll-shaped) for supplying lubricant 14 to the surface of the electrophotographic photoreceptor 7, and a fibrous member 133 (flat brush-shaped) for assisting cleaning. These can be arranged as needed.

[0270] The following describes the various components of the image forming apparatus according to this embodiment.

[0271] -Charging device- The charging device 8 may be a contact-type charging device in which the charging member contacts the outer surface of the photoreceptor, or a non-contact-type charging device in which the charging member does not contact the outer surface of the photoreceptor. The effect of the image forming apparatus according to this embodiment (less likely to cause contamination of the charging member over a long period of time) is particularly pronounced in the contact-type charging device.

[0272] As the charging device 8, for example, contact-type charging members using conductive or semiconductive charging rollers, charging brushes, charging films, charging rubber blades, charging tubes, etc. are used. Non-contact roller chargers, known chargers such as scorotron chargers and corotron chargers that utilize corona discharge are also used.

[0273] -Exposure equipment- Examples of exposure devices 9 include optical equipment that exposes the surface of an electrophotographic photoreceptor 7 to a predetermined image using light such as semiconductor laser light, LED light, or liquid crystal shutter light. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photoreceptor. As for the wavelength of the semiconductor laser, near-infrared lasers with an oscillation wavelength of around 780 nm are the mainstream. However, the wavelength is not limited to this, and lasers with oscillation wavelengths in the 600 nm range or blue lasers with oscillation wavelengths between 400 nm and 450 nm may also be used. Furthermore, for color image formation, surface-emitting laser light sources capable of outputting multiple beams are also effective.

[0274] -Developing equipment- Examples of developing devices 11 include general developing devices that develop by contacting or not contacting the developing agent. There are no particular restrictions on the developing device 11 as long as it has the above-described functions, and it can be selected according to the purpose. For example, known developing devices that have the function of applying a one-component or two-component developing agent to the electrophotographic photoreceptor 7 using a brush, roller, etc. Among these, those that use a developing roller that holds the developing agent on its surface are preferred.

[0275] The developer used in the developing device 11 may be a one-component developer consisting of toner alone, or a two-component developer containing toner and a carrier. Furthermore, the developer may be magnetic or non-magnetic. Known developers can be used.

[0276] -Cleaning device- The cleaning device 13 uses a cleaning blade type device equipped with a cleaning blade 131. Details of the cleaning blade will be described later.

[0277] -Transfer device- Examples of the transfer device 40 include contact-type transfer chargers using belts, rollers, films, rubber blades, etc., and transfer chargers that are known themselves, such as scorotron transfer chargers and corotron transfer chargers that utilize corona discharge.

[0278] -Intermediate Transcript- As the intermediate transfer body 50, a belt-shaped material (intermediate transfer belt) containing semiconducting polyimide, polyamide-imide, polycarbonate, polyarylate, polyester, rubber, etc. is used. In addition to the belt shape, a drum-shaped intermediate transfer body may also be used.

[0279] Figure 4 is a schematic diagram showing another example of an image forming apparatus according to this embodiment. The image forming apparatus 120 shown in Figure 4 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one electrophotographic photoreceptor is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem type.

[0280] [Cleaning Blade] The cleaning blade of the cleaning device of the image forming apparatus according to this embodiment is preferably of the following form.

[0281] The cleaning blade contains polyurethane rubber, which is polymerized from at least a polyol component and a polyisocyanate component, in at least the contact portion (hereinafter referred to as the "contact portion") that comes into contact with the photoreceptor, or the component constituting the contact portion (hereinafter referred to as the "contact component"). The cleaning blade has at least a contact portion or contact member that has a ratio of 0.25 or more between the 100% modulus M100 (MPa) and the rebound modulus Re (%), a rebound modulus Re of less than 25%, and a tensile stress of 15 MPa or more at 200% strain.

[0282] A cleaning blade that satisfies the above characteristics has a high M100 / Re ratio, a low rebound modulus, and high tensile stress, thereby reducing pressure fluctuations (i.e., maximum pressure) in the blade, improving the blade's energy absorption capacity, and stabilizing the blade's behavior.

[0283] In this disclosure, the 100% modulus, rebound modulus, and tensile stress of the cleaning blade are values ​​measured using the contact member as a sample by the following measurement method.

[0284] The 100% modulus is determined in accordance with JIS K6251:2010, using a dumbbell-shaped No. 3 test specimen, at a temperature of 23°C and a tensile speed of 500 mm / min, and calculated from the stress at 100% strain. A Strograph AE Elastomer (Toyo Seiki Seisakusho Co., Ltd.) is used as the measuring device.

[0285] The rebound modulus is measured in accordance with JIS K6255:1996, using a Lübke rebound modulus tester at a temperature of 23°C.

[0286] The tensile stress is the tensile stress at 200% strain measured at a temperature of 23°C. It is measured using a dumbbell-shaped specimen (Type 3) at a tensile speed of 500 mm / min. A Strograph AE Elastomer (Toyo Seiki Seisakusho Co., Ltd.) is used as the measuring device.

[0287] The ratio M100 / Re of the contact portion or contact member is 0.25 or higher, preferably 0.28 or higher, and more preferably 0.3 or higher. From the viewpoint of wear resistance, the upper limit of the ratio M100 / Re of the contact portion or contact member is preferably 1.0 or lower, and more preferably 0.9 or lower. The ratio M100 / Re of the contact portion or contact member is preferably 0.25 or higher and 1.0 or lower, more preferably 0.28 or higher and 1.0 or lower, and even more preferably 0.3 or higher and 0.9 or lower.

[0288] The rebound modulus Re of the contact portion or contact member is less than 25%, preferably 22% or less, and more preferably 20% or less. The lower limit of the rebound modulus Re of the contact portion or contact member is preferably 10% or more, and more preferably 13% or more, from the viewpoint of suppressing blade noise and wear resistance. The rebound modulus Re of the contact portion or contact member is preferably 10% or more and less than 25%, more preferably 10% or more and 22% or less, and even more preferably 13% or more and 20% or less.

[0289] From the viewpoint of satisfying the above characteristics, the 100% modulus M100 of the contact portion or contact member is preferably 4 MPa to 10 MPa, and more preferably 5 MPa to 9 MPa.

[0290] The tensile stress of the contact portion or contact member at 200% strain is 15 MPa or more, preferably 21 MPa or more, and more preferably 26 MPa or more. The upper limit of the tensile stress of the contact portion or contact member is preferably 40 MPa or less, and more preferably 35 MPa or less. The tensile stress of the contact portion or contact member is preferably 15 MPa or more and 40 MPa or less, more preferably 21 MPa or more and 40 MPa or less, and even more preferably 26 MPa or more and 35 MPa or less.

[0291] It is preferable that the polyurethane rubber has hard segments and soft segments. The 100% modulus, rebound modulus, and tensile stress of the contact portion or contact member can be controlled by adjusting the ratio of hard segments to soft segments contained in the polyurethane rubber, depending on the type and amount of polymerization components used and the manufacturing conditions.

[0292] From the viewpoint of easily setting the 100% modulus, rebound modulus, and tensile stress within the aforementioned ranges, the average diameter of the hard segment aggregate is preferably 1 μm to 10 μm, and more preferably 1 μm to 5 μm.

[0293] The average diameter of the hard segment aggregates is measured by the following method. Using a polarizing microscope (BX51-P, Olympus Corporation), images were captured at 20x magnification and then binarized through image processing. The equivalent circle diameter of 500 aggregates (5 points per cleaning blade, 5 aggregates per point) was measured using 20 cleaning blades, and the arithmetic mean of these 500 equivalent circle diameters was calculated. Image binarization was performed using the image processing software OLYMPUS Stream essentials (Olympus Corporation), adjusting the hue / saturation / luminance thresholds so that crystalline and hard segment aggregates appeared black and amorphous parts (corresponding to soft segments) appeared white.

[0294] The weight-average molecular weight of polyurethane rubber is preferably between 1000 and 4000, and more preferably between 1500 and 3500.

[0295] The crosslinking density of polyurethane rubber is 0.93 × 10⁻¹⁰, from the viewpoint of controlling the 100% modulus, rebound modulus, and tensile stress within the aforementioned ranges. -3 mol / m 3 The above 1.45 × 10 -3 mol / m 3 The following is preferable: 1.01 × 10 -3 mol / m 3 The above 1.26 × 10 -3 mol / m 3 The following is more preferable: 1.07 × 10 -3 mol / m 3 The above is 1.22 × 10 -3 mol / m 3 The following is even more preferable.

[0296] The materials and composition of the contact portion or contact member are described below. The molecular weights of polyurethane rubber and its components are measured using gel permeation chromatography (GPC).

[0297] Polyurethane rubber is a polyurethane rubber obtained by polymerizing at least a polyol component and a polyisocyanate component. The polyurethane rubber may also be a polyurethane rubber obtained by further polymerizing a resin having a functional group that reacts with isocyanate groups, if necessary.

[0298] • Polyol components Polyol components include high molecular weight polyols and low molecular weight polyols.

[0299] High molecular weight polyols are polyols with a number average molecular weight of 500 or more. Preferably, high molecular weight polyols have a number average molecular weight of 5000 or less. Examples of high molecular weight polyols include polyester polyols obtained by dehydration condensation of low molecular weight polyols and dibasic acids; polycarbonate polyols obtained by reaction of low molecular weight polyols and alkyl carbonates; polycaprolactone polyols, polyether polyols, and other known polyols. Examples of commercially available high molecular weight polyols include Praxel 205 and Praxel 240 from Daicel Corporation. High molecular weight polyols may be used individually or in combination of two or more types.

[0300] The polymerization ratio of the polymer polyol is preferably 30 mol% to 50 mol%, and more preferably 40 mol% to 50 mol%, relative to the total polymerization components of the polyurethane rubber.

[0301] Low molecular weight polyols are polyols with a number-average molecular weight of less than 500. Low molecular weight polyols are materials that function as chain length extenders and crosslinking agents.

[0302] 1,4-butanediol is a suitable low molecular weight polyol. The proportion of 1,4-butanediol is preferably more than 50 mol% and 75 mol% or less, more preferably 52 mol% to 75 mol%, even more preferably 55 mol% to 75 mol%, and even more preferably 55 mol% to 60 mol% or less, relative to the total polyol components. The proportion of 1,4-butanediol relative to the total low molecular weight polyol is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol%. It is most preferable that the entire low molecular weight polyol is 1,4-butanediol.

[0303] In addition to 1,4-butanediol, other low molecular weight polyols include diols (bifunctional), triols (trifunctional), and tetraols (tetrafunctional), which are known as chain length extenders and crosslinking agents. These polyols other than 1,4-butanediol may be used individually or in combination of two or more.

[0304] The polymerization ratio of the low molecular weight polyol is preferably more than 50 mol% and 75 mol% or less, more preferably 52 mol% to 75 mol%, even more preferably 55 mol% to 75 mol%, and even more preferably 55 mol% to 60 mol% or less, relative to the total polymerization components of the polyurethane rubber.

[0305] • Polyisocyanate components Examples of polyisocyanate components include 4,4'-diphenylmethane diisocyanate (MDI), 2,6-toluene diisocyanate (TDI), 1,6-hexane diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI), and 3,3-dimethylbiphenyl-4,4'-diisocyanate (TODI). One polyisocyanate component may be used alone, or two or more may be used in combination. Preferred polyisocyanate components include 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI), and hexamethylene diisocyanate (HDI).

[0306] The polymerization ratio of the polyisocyanate component is preferably 5 mol% to 25 mol%, and more preferably 10 mol% to 20 mol%, relative to the total polymerization components of the polyurethane rubber. Setting the polymerization ratio of the polyisocyanate component within this range makes it easier to set the 100% modulus, rebound modulus, and tensile stress within the aforementioned ranges.

[0307] • Resins having functional groups that react with isocyanate groups (functional group-containing resins) As functional group-containing resins, flexible resins are preferred, and aliphatic resins having a linear structure are preferred. Specific examples of functional group-containing resins include acrylic resins containing two or more hydroxyl groups, polybutadiene resins containing two or more hydroxyl groups, and epoxy resins having two or more epoxy groups.

[0308] Examples of commercially available acrylic resins containing two or more hydroxyl groups include Actflow UMB-2005B, UMB-2005P, UMB-2005, UME-2005, etc. (Sohken Chemical Co., Ltd.). Examples of commercially available polybutadiene resins containing two or more hydroxyl groups include R-45HT (Idemitsu Kosan Co., Ltd.).

[0309] As an epoxy resin having two or more epoxy groups, an epoxy resin that is more flexible and tougher than general epoxy resins is preferred. For example, an epoxy resin having a flexible skeleton in its main chain structure is preferred, and examples of flexible skeletons include alkylene skeletons, cycloalkane skeletons, and polyoxyalkylene skeletons, with polyoxyalkylene skeletons being particularly preferred. Furthermore, an epoxy resin with low viscosity relative to its molecular weight is preferred. Specifically, a weight-average molecular weight is preferably in the range of 900 ± 100, and a viscosity at 25°C is preferably in the range of 15000 ± 5000 mPa·s, and more preferably in the range of 15000 ± 3000 mPa·s. An example of a commercially available epoxy resin having these characteristics is EPLICON EXA-4850-150 (DIC Corporation).

[0310] • Manufacturing method of polyurethane rubber For the manufacture of polyurethane rubber, general manufacturing methods such as the prepolymer method and the one-shot method may be applied. The polyurethane rubber composition is formed into a sheet by centrifugal molding, extrusion molding, etc., to produce the polyurethane rubber. Furthermore, contact members are manufactured by cutting or other processing of the polyurethane rubber.

[0311] Examples of catalysts used in the manufacture of polyurethane rubber include amine compounds such as tertiary amines, quaternary ammonium salts, and organometallic compounds such as organotin compounds. A single catalyst may be used, or two or more catalysts may be used in combination.

[0312] Examples of tertiary amines include trialkylamines such as triethylamine; tetraalkyldiamines such as N,N,N',N'-tetramethyl-1,3-butanediamine; amino alcohols such as dimethylethanolamine; esteramines such as ethoxylated amines, ethoxylated diamines, bis(diethylethanolamine) adipate, cyclohexylamine derivatives such as triethylenediamine (TEDA) and N,N-dimethylcyclohexylamine; morpholine derivatives such as N-methylmorpholine and N-(2-hydroxypropyl)-dimethylmorpholine; and piperazine derivatives such as N,N'-diethyl-2-methylpiperazine and N,N'-bis-(2-hydroxypropyl)-2-methylpiperazine. Examples of quaternary ammonium salts include 2-hydroxypropyltrimethylammonium octylate, 1,5-diazabicyclo[4.3.0]nonene-5(DBN)octylate, 1,8-diazabicyclo[5.4.0]undecene-7(DBU)octylate, DBU oleate, DBU-p-toluenesulfonate, DBU formate, and 2-hydroxypropyltrimethylammonium formate. Examples of organotin compounds include dialkyltin compounds such as dibutyltin dilaurate and dibutyltin di(2-ethylhexoate); stannous 2-ethylcaproate and stannous oleate. From the viewpoint of hydrolysis resistance, the tertiary ammonium salt triethylenediamine (TEDA) is preferred, and from the viewpoint of processability, the quaternary ammonium salt is preferred. Among the quaternary ammonium salts, 1,5-diazabicyclo[4.3.0]nonene-5(DBN)·octylate, 1,8-diazabicyclo[5.4.0]undecene-7(DBU)-octylate, and DBU-formate are preferably used due to their high reaction activity.

[0313] The amount of catalyst added is preferably in the range of 0.0005% by mass or more and 0.03% by mass or less of the total polyurethane rubber constituting the contact member, and particularly preferably 0.001% by mass or more and 0.01% by mass or less.

[0314] An embodiment of the cleaning blade will be described with reference to Figures 5 to 7. Figure 5 is a schematic diagram showing a cleaning blade according to the first embodiment, and illustrates the state in which it is in contact with the surface of the photoreceptor. Figure 6 is a schematic diagram showing a cleaning blade according to the second embodiment, and is a diagram showing the blade in contact with the surface of the photoreceptor. Figure 7 is a schematic diagram showing a cleaning blade according to the third embodiment, and illustrates the state in which it is in contact with the surface of the photoreceptor.

[0315] As shown in Figure 5, the cleaning blade has a contact angle portion 3A, a tip surface 3B, a ventral surface 3C, and a back surface 3D. The contact corner portion 3A is a contact portion that comes into contact with the driven photoreceptor 31 and cleans the surface of the photoreceptor 31. The front surface 3B is the surface on which the contact angle portion 3A forms one side, and it faces upstream in the direction of the photoreceptor 31's drive (direction of arrow A). The back surface 3C is the surface on which the contact angle portion 3A forms one side, and it faces downstream in the direction of the photoreceptor 31's drive (direction of arrow A). The back surface 3D is the surface on which the front surface 3B shares one side, and it faces the back surface 3C. The cleaning blade is supported by a support member (not shown) attached to the upper part (the side furthest from the photoreceptor 31) of its ventral surface 3C or ventral surface 3D. The cleaning blade is pressed against the photoreceptor 31 by the force from the support member. Examples of support members include metal members such as aluminum and stainless steel. An adhesive layer may be present between the support member and the cleaning blade.

[0316] The cleaning blade 342A shown in Figure 5 is composed entirely of a single material, including the contact angle 3A, meaning it consists only of contact members. The cleaning blade 342B shown in Figure 6 has a two-layer structure consisting of a first layer 3421B including the contact corner and a second layer 3422B that supports the first layer. The second layer 3422B is made of a different material than the first layer 3421B. The cleaning blade 342C shown in Figure 7 has a structure consisting of a contact member 3421C including a contact angle and a back member 3422C that supports the contact member 3421C. The contact member 3421C has a shape obtained by dividing a cylinder into four parts, and the right-angle portions of the quadrants form the contact angle 3A. The contact member 3421C may be a square quadrangular prism, a rectangular quadrangular prism, etc. The back member 3422C is made of a different material from the contact member 3421C.

[0317] The cleaning blade 342A shown in Figure 5, the first layer 3421B of the cleaning blade 342B shown in Figure 6, and the contact member 3421C of the cleaning blade 342C shown in Figure 7 are all made of a material containing polyurethane rubber polymerized from at least a polyol component and a polyisocyanate component. The cleaning blade 342A shown in Figure 5, the first layer 3421B of the cleaning blade 342B shown in Figure 6, and the contact member 3421C of the cleaning blade 342C shown in Figure 7 all have a 100% modulus M100 (MPa) to rebound modulus Re (%) ratio M100 / Re of 0.25 or higher, a rebound modulus Re of less than 25%, and a tensile stress of 15 MPa or higher at 200% strain.

[0318] The second layer 3422B of the cleaning blade 342B shown in Figure 6 and the back member 3422C of the cleaning blade 342C shown in Figure 7 have the function of supporting the contact member. Examples of materials for these members include polyurethane rubber, silicone rubber, fluororubber, chloroprene rubber, and butadiene rubber. Polyurethane rubber is preferred as the material for these members. Examples of polyurethane rubber include ester-based polyurethane and ether-based polyurethane, with ester-based polyurethane being preferred.

[0319] The cleaning blade 342A shown in Figure 5 is manufactured by cutting and processing polyurethane rubber. The cleaning blade 342B shown in Figure 6 is manufactured by bonding the first layer 3421B and the second layer 3422B together with an adhesive, or by pouring the rubber material into the mold with a time difference during polyurethane rubber molding to produce a laminate. The cleaning blade 342C shown in Figure 7 is manufactured, for example, by creating a polyurethane rubber member in which four of the blades are joined together with a contact member 3421C in the center, and then dividing this into four parts. [Examples]

[0320] The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following explanation, unless otherwise specified, "parts" and "%" refer to mass. In the following descriptions, synthesis, processing, and manufacturing were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0321] <Synthesis of polyarylate resin> Polyarylate resins (PA1) to (PA4) were synthesized. Table 1 shows the units and composition of polyarylate resin. A2-3 and others listed in Table 1 are specific examples of the dicarboxylic acid unit (A) described above. Table 1 shows examples of B1-2, etc., which are specific examples of the diol unit (B) described above.

[0322] [Table 1]

[0323] <Manufacturing of photoreceptors> The following materials were prepared to form the outermost layer (charge transport layer). ·Charge transport material: CTM-1 ·Charge transport material: CTM-2

[0324] [ka]

[0325] • Polycarbonate resin (PC1), viscosity-average molecular weight 50,000 • Polycarbonate resin (PC3), viscosity-average molecular weight 40,000 The numbers accompanying the constituent units in the structural formulas below represent the molar ratio.

[0326] [ka]

[0327] • Phenolic compound: ADEKA Stab AO-30, ADEKA Corporation • Phenolic compounds: ADEKA stab AO-60, ADEKA Corporation • Phenol compounds: ADEKA stab AO-80, ADEKA Corporation • Phenolic compounds: ADEKA stab AO-330, ADEKA Corporation

[0328] [Example 1] -Formation of the lower layer- 3.5 parts of butyral resin (product name: S-Rec BM-1, Sekisui Chemical Co., Ltd.) and 41 parts of methyl ethyl ketone were mixed and dissolved. 10 parts of a curing agent (blocked isocyanate, product name: Sumijoule 3175, Sumitomo Bayer Urethane Co., Ltd.), 45.5 parts of zinc oxide (product name: SMZ-017N, Teika Co., Ltd.) surface-treated with a silane coupling agent (product name: KBM603, Shin-Etsu Chemical Co., Ltd.), and 0.27 parts of a compound represented by the following structural formula were added and stirred. The mixture was then dispersed for 2 hours using 1 mm diameter glass beads in a sand mill. Furthermore, 0.01 parts of dioctyl tin dilaurate and 2 parts of silicone resin particles (product name: Tospearl 145, GE Toshiba Silicone Co., Ltd.) were added and stirred to obtain a coating solution for forming the undercoat layer. A coating solution for forming the undercoat layer was applied to the outer surface of the conductive substrate by immersion coating, and drying and curing was performed at 170°C for 40 minutes to form an undercoat layer with a thickness of 20 μm.

[0329] [ka]

[0330] -Formation of a charge generation layer- A mixture consisting of 15 parts of hydroxygallium phthalocyanine (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in its X-ray diffraction spectrum using CuKα characteristic X-rays), 10 parts of vinyl chloride / vinyl acetate copolymer resin (product name: VMCH, Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed for 4 hours using glass beads with a diameter of 1 mm in a sand mill. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion and stirred to obtain a coating solution for forming the charge generation layer. The coating solution for forming the charge generation layer was immersed and coated onto the undercoat, and dried at room temperature to form a charge generation layer with a thickness of 0.25 μm.

[0331] -Formation of a charge transport layer- • Resin: Polyarylate resin (PA2) ... 20 parts (20% of total resin) • Resin: Polycarbonate resin (PC3) ... 80 parts (80% of total resin) ·Charge transport material: CTM-1 ··· 67 parts • Phenol compounds: Adekastab AO-30... 5 parts • Solvent: Tetrahydrofuran • 570 parts • Solvent: Toluene • 57 copies The above materials were stirred and mixed to obtain a coating solution for forming a charge transport layer. The coating solution for forming a charge transport layer was applied to the charge generating layer by immersion, and dried at 143°C for 30 minutes to form a charge transport layer with a thickness of 33 μm.

[0332] [Examples 2-19, Comparative Examples 1-7] Each photoreceptor was manufactured in the same manner as in Example 1, except that the specifications of the charge transport layer were changed as shown in Tables 2 and 3. When CTM-1 and CTM-2 were used as charge transport materials, 47 parts of CTM-1 and 20 parts of CTM-2 were used.

[0333] The resin percentages shown in Tables 2 and 3 represent the mass ratio of the total polyarylate resin and polycarbonate resin. The phenol compound content shown in Tables 2 and 3 represents the mass ratio of the total mass of the charge transport layer. The symbols "+" and "-" for the charge transport material indicate the presence and absence of additives, respectively.

[0334] <Performance Evaluation> The photoreceptor of each example or comparative example was mounted in an electrophotographic image forming apparatus (models are shown in Tables 2 and 3; all manufactured by Xerox Corporation). In Examples 13-19 and Comparative Example 7, the cleaning blade of the image forming apparatus was replaced with a cleaning blade in which the contact portion that comes into contact with the photoreceptor contains polyurethane rubber polymerized from at least a polyol component and a polyisocyanate component, and has the physical properties shown in Table 4.

[0335] The following image formation procedures (1), (2), (3), and (4) were performed in this order. (1) Ten image charts were formed on A4 plain paper in an environment with a temperature of 20°C and a relative humidity of 40%. (2) 100,000 image charts were formed on A4 plain paper in an environment with a temperature of 28°C and a relative humidity of 85%. (3) 100,000 image charts were formed on A4 plain paper in an environment with a temperature of 10°C and a relative humidity of 15%. (4) Ten image charts were formed on A4 plain paper in an environment with a temperature of 20°C and a relative humidity of 40%.

[0336] The ten images in (1) were observed with the naked eye and with a magnifying glass (×25) and classified as follows. The results are shown in "Initial Image Quality" in Tables 2 and 3. The ten images in (4) were observed with the naked eye and with a magnifying glass (×25) and classified as follows. The results are shown in "Image Quality at the End Stage" in Tables 2 and 3.

[0337] A: No image defects were observed across the entire area of ​​any of the 10 images. B+: Minor image defects are observed in only a portion of the image in one or two images. B: Minor image defects are observed in only certain areas of three or four images. B-: Minor image defects are observed in only certain areas of 5 or 6 images. C+: Image defects are visible in only a portion of the image, across 1 to 3 images. C: Image defects are visible in only certain areas across 4 to 6 images. C-: Image defects are observed in only certain areas of 7 or more images. D: In all 10 images, there is clear image loss in less than 1 / 4 of the entire area. E: In all 10 images, there is clear image loss in an area of ​​more than 1 / 4 but less than 1 / 2 of the entire image. F: In all 10 images, more than half of the image area is clearly missing. G: All 10 images clearly have missing parts across the entire surface.

[0338] The abbreviations in Tables 2 and 3 have the following meanings. • PAR: Polyarylate resin PC: Polycarbonate resin

[0339] [Table 2]

[0340] [Table 3]

[0341] [Table 4]

[0342] The electrophotographic photoreceptor, process cartridge, and image forming apparatus of this disclosure include the following embodiments. Each formula is identical to the formula of the same number described above.

[0343] (Note) (((1))) The device comprises a conductive substrate and a photosensitive layer disposed on the conductive substrate, The outermost layer contains a charge transport material, a polyarylate resin having dicarboxylic acid units represented by formula (A) and diol units represented by formula (B), a polycarbonate resin, and a phenol compound having three or fewer phenolic functional groups and a molecular weight of 300 or more. The dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is 0.50 or less. Electrophotographic photoreceptor. (((2))) The electrophotographic photoreceptor according to (((1))), wherein the value of the dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is 0.40 or less. (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), wherein the phenol compound comprises a phenol compound having two or fewer phenolic functional groups and a molecular weight of 350 or more. (((4))) An electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the dicarboxylic acid unit represented by formula (A) includes at least one selected from the group consisting of a dicarboxylic acid unit represented by formula (A1) (A1), a dicarboxylic acid unit represented by formula (A2) (A2), a dicarboxylic acid unit represented by formula (A3) (A3), a dicarboxylic acid unit represented by formula (A4) (A4), and a dicarboxylic acid unit represented by formula (A5) (A5). (((5))) An electrophotographic photoreceptor according to any one of (((1))) to (((4))), wherein the diol unit represented by formula (B) includes at least one selected from the group consisting of a diol unit represented by formula (B1) (B1), a diol unit represented by formula (B2) (B2), a diol unit represented by formula (B3) (B3), a diol unit represented by formula (B4) (B4), a diol unit represented by formula (B5) (B5), a diol unit represented by formula (B6) (B6), a diol unit represented by formula (B7) (B7), and a diol unit represented by formula (B8) (B8). (((6))) The electrophotographic photoreceptor according to any one of (((1))) to (((5))), wherein the polyarylate resin and the polycarbonate resin each have a constituent unit containing biphenyl represented by formula (BP). (((7))) An electrophotographic photoreceptor according to any one of (((1))) to (((6))), wherein the proportion of polyarylate resin in the total amount of polyarylate resin and polycarbonate resin contained in the outermost layer is 25% by mass or more and 75% by mass or less. (((8))) The electrophotographic photoreceptor according to any one of (((1))) to (((7))), wherein the photosensitive layer has a charge generating layer and a charge transport layer, and the charge transport layer is the outermost layer. (((9))) The electrophotographic photoreceptor is provided as described in any one of (((1))) to (((8))), To be attached to and detached from the image forming apparatus, Process cartridge. (((10))) An electrophotographic photoreceptor described in any one of (((1))) to (((8))), A charging device for charging the surface of the electrophotographic photoreceptor, An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, A developing apparatus that develops an electrostatic latent image formed on the surface of an electrophotographic photoreceptor using a developer containing toner to form a toner image, The system includes a transfer device for transferring the toner image onto the surface of a recording medium. Image forming apparatus. (((11))) The device further comprises a cleaning device having a cleaning blade that contacts the surface of the electrophotographic photoreceptor, for cleaning the surface of the electrophotographic photoreceptor. The image forming apparatus described in (((10))). (((12))) The contact portion of the cleaning blade that contacts the electrophotographic photoreceptor is made of a material containing polyurethane rubber polymerized from at least a polyol component and a polyisocyanate component, having a 100% modulus M100 (MPa) to rebound modulus Re (%) ratio M100 / Re of 0.25 or more, a rebound modulus Re of less than 25%, and a tensile stress of 15 MPa or more at 200% strain. The image forming apparatus described in (((11))). (((13))) The image forming apparatus according to (((12))), wherein the ratio M100 / Re is 0.28 or more and 1.0 or less.

[0344] According to (((1))), (((4))), (((5))), (((6))), (((7))), or (((8))), an electrophotographic photoreceptor is provided that is less prone to image defects even when used under high stress conditions, until the end of its lifespan, compared to cases where the outermost layer does not contain phenol compounds with three or fewer phenol functional groups but contains phenol compounds with four phenol functional groups, or where the value of the dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is greater than 0.50. According to (((2))), compared to the case where the dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is greater than 0.40, an electrophotographic photoreceptor is provided that is less prone to image defects even when used under high stress conditions until the end of its lifespan. According to (((3))), compared to the case where the outermost layer does not contain a phenol compound with two phenol functional groups but contains a phenol compound with three phenol functional groups, an electrophotographic photoreceptor is provided that is less prone to image defects even when used under high stress conditions until the end of its lifespan. According to (((9))), a process cartridge is provided in which image defects are less likely to occur until the end of its lifespan, even when used under high stress conditions, compared to cases where the outermost surface layer of the electrophotographic photoreceptor does not contain phenol compounds with three or fewer phenol functional groups but contains phenol compounds with four phenol functional groups, or where the value of the dielectric loss tangent tanδ of the outermost surface layer of the electrophotographic photoreceptor at a frequency of 1 Hz is greater than 0.50. According to (((10))) or (((11))), compared to the case where the outermost layer of the electrophotographic photoreceptor does not contain phenol compounds with three or fewer phenol functional groups but contains phenol compounds with four phenol functional groups, or the case where the dielectric loss tangent tanδ of the outermost layer of the electrophotographic photoreceptor at a frequency of 1 Hz is greater than 0.50, an image forming apparatus is provided in which image defects are less likely to occur until the end of its lifespan even when used under high stress conditions. According to (((12))), compared to image forming apparatuses with a ratio M100 / Re of less than 0.25, a rebound modulus Re of 25% or more, or a tensile stress of less than 15 MPa, an image forming apparatus is provided that is less prone to image defects even when used under high stress conditions until the end of its lifespan. According to (((13))), compared to image forming apparatuses with a ratio M100 / Re of less than 0.28 or greater than 1.0, an image forming apparatus is provided that is less prone to image defects even when used under high stress conditions, until the end of its lifespan. [Explanation of Symbols]

[0345] 1 Conductive substrate, 2 Undercoat layer, 3 Charge generation layer, 4 Charge transport layer, 5 Photosensitive layer, 10A photoreceptor, 10B photoreceptor

[0346] 7 Electrophotographic photoreceptor, 8 Charging device, 9 Exposure device, 11 Developing device, 13 Cleaning device, 14 Lubricant, 40 Transfer device, 50 Intermediate transfer body, 100 Image forming device, 120 Image forming device, 131 Cleaning blade, 132 Fibrous material (roll type), 133 Fibrous material (flat brush type), 300 Process cartridge

[0347] 342A, 342B, 342C Cleaning blade, 3421B First layer, 3422B Second layer, 3421C Contact member, 3422C Back member, 31 Photoreceptor

Claims

1. The device comprises a conductive substrate and a photosensitive layer disposed on the conductive substrate, The outermost layer contains a charge transport material, a polyarylate resin having dicarboxylic acid units represented by formula (A) and diol units represented by formula (B) below, a polycarbonate resin, and a phenol compound having three or fewer phenolic functional groups and a molecular weight of 300 or more. The dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is 0.50 or less. Electrophotographic photoreceptor. 【Chemistry 1】 In equation (A), Ar Ａ１ and Ar Ａ２ Each of these is an aromatic ring which may independently have substituents, L Ａ is a single bond or a divalent linking group, n Ａ１ It is 0, 1, or 2. In formula (B), Ar Ｂ１ and Ar Ｂ２ are each independently an aromatic ring which may have a substituent, L Ｂ is a single bond, an oxygen atom, a sulfur atom or -C(Rb １ )(Rb ２ )-, n Ｂ１ is 0, 1 or 2. Rb １ and Rb ２ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb １ and Rb ２ may combine to form a cyclic alkyl group.

2. The electrophotographic photoreceptor according to claim 1, wherein the value of the dielectric loss tangent tanδ of the outermost layer at a frequency of 1 Hz is 0.40 or less.

3. The electrophotographic photoreceptor according to claim 1, wherein the phenol compound comprises a phenol compound having two or fewer phenolic functional groups and a molecular weight of 350 or more.

4. The electrophotographic photoreceptor according to claim 1, wherein the dicarboxylic acid unit represented by formula (A) includes at least one selected from the group consisting of a dicarboxylic acid unit represented by formula (A1) (A1), a dicarboxylic acid unit represented by formula (A2) (A2), a dicarboxylic acid unit represented by formula (A3) (A3), a dicarboxylic acid unit represented by formula (A4) (A4), and a dicarboxylic acid unit represented by formula (A5) (A5). 【Chemistry 2】 In equation (A1), n １０１ n is an integer between 0 and 4, and １０１ Individual Ra １０１ Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In equation (A2), n ２０１ and n ２０２ Each of these is an independent integer between 0 and 4, and n ２０１ Individual Ra ２０１ and n ２０２ Individual Ra ２０２ Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In equation (A3), n ３０１ and n ３０２ Each of these is an independent integer between 0 and 4, and n ３０１ Individual Ra ３０１ and n ３０２ Individual Ra ３０２ Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In equation (A4), n ４０１ n is an integer between 0 and 6, and ４０１ Individual Ra ４０１ Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In equation (A5), n ５０１ , n ５０２ and n ５０３ Each of these is an independent integer between 0 and 4, and n ５０１ Individual Ra ５０１ , n ５０２ Individual Ra ５０２ and n ５０３ Individual Ra ５０３ Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

5. The electrophotographic photoreceptor according to claim 1, wherein the diol unit represented by formula (B) includes at least one selected from the group consisting of the diol unit represented by formula (B1) (B1), the diol unit represented by formula (B2) (B2), the diol unit represented by formula (B3) (B3), the diol unit represented by formula (B4) (B4), the diol unit represented by formula (B5) (B5), the diol unit represented by formula (B6) (B6), the diol unit represented by formula (B7) (B7), and the diol unit represented by formula (B8) (B8). 【Transformation 3】 【Chemistry 4】 In equation (B1), Rb １０１ Rb is a branched alkyl group having 4 to 20 carbon atoms. ２０１ Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ４０１ , Rb ５０１ , Rb ８０１ and Rb ９０１ Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In equation (B2), Rb １０２ Rb is a linear alkyl group having 4 to 20 carbon atoms. ２０２ Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ４０２ , Rb ５０２ , Rb ８０２ and Rb ９０２ Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In equation (B3), Rb １１３ and Rb ２１３ Each of these is independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, d is an integer between 7 and 15, and Rb ４０３ , Rb ５０３ , Rb ８０３ and Rb ９０３ Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In equation (B4), Rb １０４ and Rb ２０４ Each is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０４ , Rb ５０４ , Rb ８０４ and Rb ９０４ Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B5), Ar １０５ Rb is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms. ２０５ Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ４０５ , Rb ５０５ , Rb ８０５ and Rb ９０５ Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In equation (B6), Rb １１６ and Rb ２１６ Each of these is independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, e is an integer between 4 and 6, and Rb ４０６ , Rb ５０６ , Rb ８０６ and Rb ９０６ Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In equation (B7), Rb ４０７ , Rb ５０７ , Rb ８０７ and Rb ９０７ Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In equation (B8), Rb ４０８ , Rb ５０８ , Rb ８０８ and Rb ９０８ Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

6. The electrophotographic photoreceptor according to claim 1, wherein the polyarylate resin and the polycarbonate resin each have a structural unit containing biphenyl represented by the following formula (BP). 【Transformation 5】 In equation (BP), j is an integer between 0 and 4, and j R １ Each is independently either a methyl group or an ethyl group, k is an integer between 0 and 4, and there are k R ２ These are independently either a methyl group or an ethyl group.

7. The electrophotographic photoreceptor according to claim 1, wherein the proportion of polyarylate resin in the total amount of polyarylate resin and polycarbonate resin contained in the outermost layer is 25% by mass or more and 75% by mass or less.

8. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a charge generating layer and a charge transport layer, and the charge transport layer is the outermost layer.

9. The electrophotographic photoreceptor is provided according to any one of claims 1 to 8, To be attached to and detached from the image forming apparatus, Process cartridge.

10. An electrophotographic photoreceptor according to any one of claims 1 to 8, A charging device for charging the surface of the electrophotographic photoreceptor, An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, A developing apparatus that develops an electrostatic latent image formed on the surface of an electrophotographic photoreceptor using a developer containing toner to form a toner image, The system includes a transfer device for transferring the toner image onto the surface of a recording medium. Image forming apparatus.

11. The device further comprises a cleaning device having a cleaning blade that contacts the surface of the electrophotographic photoreceptor, for cleaning the surface of the electrophotographic photoreceptor. The image forming apparatus according to claim 10.

12. The contact portion of the cleaning blade that contacts the electrophotographic photoreceptor is made of a polyurethane rubber polymerized from at least a polyol component and a polyisocyanate component, with a 100% modulus M100 (MPa) to rebound modulus Re (%) ratio M100 / Re of 0.25 or more, a rebound modulus Re of less than 25%, and a tensile stress of 15 MPa or more at 200% strain. The image forming apparatus according to claim 11.

13. The image forming apparatus according to claim 12, wherein the ratio M100 / Re is 0.28 or more and 1.0 or less.

Images