Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that is excellent in wear resistance and reduces occurrence of charging unevenness.SOLUTION: An electrophotographic photoreceptor comprises a conductive substrate, and a photosensitive layer having a charge generating layer and a charge transport layer. An average thickness of the charge transport layer is 30 μm or more. The charge transport layer contains a polyarylate resin. An absorption spectrum measured by peeling off the photosensitive layer and dissolving the same in tetrahydrofuran satisfies a formula (1) and a formula (2). Formula (1): Iu≤0.95×Im. Formula (2): 1.05×Im≤Il. When a total length in an axial direction of the electrophotographic photoreceptor is defined as L, Im is absorbance at a wavelength of 678 nn related to the photosensitive layer peeled off from a center in the axial direction of the electrophotographic photoreceptor, Iu is absorbance at a wavelength of 678 nn related to the photosensitive layer peeled off from a position of 0.40 L toward one end from the center in the axial direction of the electrophotographic photoreceptor, and Il is absorbance at a wavelength of 678 nn related to the photosensitive layer peeled off from a position of 0.40 L toward the other end from the center in the axial direction of the electrophotographic photoreceptor.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses an electrophotographic photoreceptor having a support, an undercoat layer, a charge generation layer, and a charge transport layer, wherein the charge generation layer contains at least one of a titanyl phthalocyanine pigment and a gallium phthalocyanine pigment, the charge transport layer contains at least one of a polycarbonate resin and a polyarylate resin, and has a region α in a non-image forming region where the film thickness of the charge generation layer is thinner than that of the charge generation layer in the image forming region.

[0003] Patent Document 2 discloses an electrophotographic photoreceptor having a cylindrical support, a charge generation layer, and a charge transport layer. For the charge generation layer, a region from the central position of the image forming region in the axial direction of the cylindrical support to the end position of the image forming region is divided into five equal parts, and when the average values of the film thicknesses of the charge generation layer in each divided region are d11, d12, d13, d14, and d15 in order from the central position of the image forming region to the end position of the image forming region, the film thickness of the charge generation layer satisfies the relationship d11 < d12 < d13 < d14 < d15. For the charge transport layer, a region from the central position of the image forming region in the axial direction of the cylindrical support to the end position of the image forming region is divided into five equal parts, and when the average values of the film thicknesses of the charge transport layer in each divided region are d21, d22, d23, d24, and d25 in order from the central position of the image forming region to the end position of the image forming region, the film thickness of the charge transport layer satisfies the relationship d21 > d22 > d23 > d24 > d25.

[0004] Patent document 3 discloses a method for forming a charge generating layer on a photoconductive drum, the method including preparing a dispersion having a charge generating composition, immersing an elongated support element in the dispersion, withdrawing a first portion of the elongated support element from the dispersion at a first speed and coating the charge generating composition on the first portion to a first thickness, and withdrawing a second portion of the elongated support element from the dispersion at a second speed faster than the first speed and coating the charge generating composition on the second portion to a second thickness thicker than the first thickness. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-031517 A [Patent Document 2] JP 2021-004948 A [Patent Document 3] US Patent Application Publication No. 2021 / 0124277 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide an electrophotographic photoreceptor which is more excellent in abrasion resistance and less prone to uneven charging, as compared with an electrophotographic photoreceptor which does not satisfy one or both of formulae (1) and (2). [Means for solving the problem]

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

[0008] <1> A conductive substrate; and a photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate, The charge transport layer has an average thickness of 30 μm or more, the charge transport layer contains a polyarylate resin, The absorption spectrum of the photosensitive layer measured after peeling it off and dissolving it in tetrahydrofuran satisfies the following formulas (1) and (2): Electrophotographic photoreceptor; Formula (1): Iu≦0.95×Im Formula (2): 1.05×Im≦Il When the total length of the electrophotographic photosensitive member in the axial direction is L, Im is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from the center in the axial direction of the electrophotographic photosensitive member, Iu is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward one end in the axial direction of the electrophotographic photosensitive member, Il is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward the other end in the axial direction of the electrophotographic photosensitive member. <2> 2. The electrophotographic photoreceptor according to claim 1, wherein the absorption spectrum measured by peeling off the photosensitive layer and dissolving it in tetrahydrofuran satisfies the following formulas (1-3) and (2-3): Formula (1-3): 0.75×Im <Iu≦0.95×Im Formula (2-3): 1.05×Im≦Il<1.25×Im When the total length of the electrophotographic photosensitive member in the axial direction is L, Im is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from the center in the axial direction of the electrophotographic photosensitive member, Iu is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward one end in the axial direction of the electrophotographic photosensitive member, Il is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward the other end in the axial direction of the electrophotographic photosensitive member. <3> The charge generating layer contains hydroxygallium phthalocyanine. <1> or <2> The electrophotographic photoreceptor according to claim 1. <4> The weight average molecular weight of the polyarylate resin contained in the charge transport layer is 80,000 or more. <1> ~ <3> 13. The electrophotographic photoreceptor according to claim 12, <5> the charge transport layer further contains a polycarbonate resin; <1> ~ <4> 13. The electrophotographic photoreceptor according to claim 12, <6> The polyarylate resin contains a polyarylate resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B). <1> ~ <5> 13. The electrophotographic photoreceptor according to claim 12, <7> The polyarylate resin (1) contains at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by formula (A1), a dicarboxylic acid unit (A2) represented by formula (A2), a dicarboxylic acid unit (A3) represented by formula (A3), and a dicarboxylic acid unit (A4) represented by formula (A4). <6> The electrophotographic photoreceptor according to claim 1. <8> The polyarylate resin (1) contains at least one selected from the group consisting of a diol unit (B1) represented by formula (B1), a diol unit (B2) represented by formula (B2), a diol unit (B3) represented by formula (B3), a diol unit (B4) represented by formula (B4), a diol unit (B5) represented by formula (B5), a diol unit (B6) represented by formula (B6), a diol unit (B7) represented by formula (B7), and a diol unit (B8) represented by formula (B8). <6> or <7> The electrophotographic photoreceptor according to claim 1. <9> The polyarylate resin (1) contains at least one selected from the group consisting of a dicarboxylic acid unit (A2) represented by formula (A2) and a dicarboxylic acid unit (A4) represented by formula (A4), <6> ~ <8> 13. The electrophotographic photoreceptor according to claim 12, <10> The polyarylate resin (1) contains at least one selected from the group consisting of a diol unit (B1) represented by formula (B1) and a diol unit (B2) represented by formula (B2), <6> ~ <9> 13. The electrophotographic photoreceptor according to claim 12, <11> <1> ~ <10> The electrophotographic photoreceptor according to any one of the above items is provided, A process cartridge that is detachably attached to an image forming apparatus. <12> <1> ~ <10> and an electrophotographic photoreceptor according to any one of the above items. a charging device for charging a 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 an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; A transfer device that transfers the toner image onto a surface of a recording medium. Image forming device. Effect of the Invention

[0009] <1> , <3> , <5> , <6> , <7> , <8> , <9> or <10> According to the present invention, there is provided an electrophotographic photoreceptor which is excellent in wear resistance and which is less susceptible to charging unevenness, as compared with an electrophotographic photoreceptor which does not satisfy either or both of formula (1) and formula (2). <2> According to the present invention, there is provided an electrophotographic photoreceptor which is excellent in wear resistance and which is less susceptible to charging unevenness, as compared with an electrophotographic photoreceptor which does not satisfy either or both of formula (1-3) and formula (2-3). <4> According to the present invention, an electrophotographic photoreceptor having excellent abrasion resistance is provided, as compared with a case in which the weight-average molecular weight of the polyarylate resin is less than 80,000. <11> According to the invention, there is provided a process cartridge in which the electrophotographic photosensitive member is excellent in wear resistance and is less susceptible to uneven charging, compared to a process cartridge equipped with an electrophotographic photosensitive member that does not satisfy one or both of formulas (1) and (2). <12> According to the present invention, there is provided an image forming apparatus in which the abrasion resistance of the electrophotographic photosensitive member is excellent and charging unevenness is less likely to occur, compared to an image forming apparatus including an electrophotographic photosensitive member that does not satisfy one or both of formulas (1) and (2). [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a partial cross-sectional view showing an example of a layer structure of the electrophotographic photoreceptor according to the present embodiment. [Diagram 2] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples are merely illustrative of the embodiments, and are not intended to limit the scope of the embodiments.

[0012] In the present disclosure, a numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples.

[0013] In the present disclosure, the term "step" includes not only an independent step, but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0014] When an embodiment of the present disclosure is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the size of the members in each drawing is conceptual, and the relative relationship between the sizes of the members is not limited to this.

[0015] In the present disclosure, each component may contain multiple types of corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified. In the present disclosure, the particles corresponding to each component may include multiple types. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0016] In the present disclosure, unless otherwise specified, the alkyl group and the alkylene group include any of straight-chain, branched, and cyclic groups.

[0017] In the present disclosure, a hydrogen atom in an organic group, an aromatic ring, a linking group, an alkyl group, an alkylene group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, and the like may be substituted with a halogen atom.

[0018] In the present disclosure, when a compound is shown by a structural formula, the symbols (C and H) representing carbon atoms and hydrogen atoms in the hydrocarbon group and / or hydrocarbon chain may be omitted.

[0019] In the present disclosure, the term "structural unit" of a copolymer or resin is synonymous with a monomer unit.

[0020] In the present disclosure, the "axial direction" of an electrophotographic photosensitive member means the direction in which the rotation axis of the electrophotographic photosensitive member extends, and the "circumferential direction" of an electrophotographic photosensitive member means the rotation direction of the electrophotographic photosensitive member.

[0021] <Electrophotographic photoreceptor> The electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") according to this embodiment includes a conductive substrate and a photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate.

[0022] Fig. 1 is a partial cross-sectional view showing an example of the layer structure of the photoreceptor according to the present embodiment. The photoreceptor 10A shown in Fig. 1 has a structure in which an undercoat layer 2, a charge generation layer 3, and a charge transport layer 4 are laminated in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute a photosensitive layer 5 (a so-called function-separated photosensitive layer). The photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3. The undercoat layer 2 may or may not be present.

[0023] The photoreceptor according to this embodiment is The charge transport layer has an average thickness of 30 μm or more, the charge transport layer contains a polyarylate resin; The photosensitive layer was peeled off and dissolved in tetrahydrofuran, and the absorption spectrum measured satisfied the following formulas (1) and (2).

[0024] Formula (1): Iu≦0.95×Im Formula (2): 1.05×Im≦Il When the total axial length of the photoconductor is L, Im is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from the center in the axial direction of the photoconductor, Iu is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position 0.40L from the center toward one end in the axial direction of the photoconductor, Il is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from the position of 0.40L from the center toward the other end in the axial direction of the photosensitive member.

[0025] The photoconductor according to the present embodiment has the above-mentioned configuration, and is therefore excellent in wear resistance and is less susceptible to uneven charging. The mechanism behind this is believed to be as follows.

[0026] The photosensitive layer is preferably thicker in order to extend the life of the photoreceptor, and the charge transport layer is preferably 30 μm or more. From the viewpoint of the abrasion resistance of the photosensitive layer, it is preferable to use a polyarylate resin as the binder resin of the charge transport layer. The larger the molecular weight of the polyarylate resin, the more advantageous it is in terms of abrasion resistance. Incidentally, photosensitive layers are generally formed by dipping the conductive substrate in a coating solution with the axial direction of the conductive substrate aligned in the direction of gravity. Polyarylate resin is a resin that tends to become viscous due to its molecular structure (stacking of aromatic rings), and the larger the molecular weight, the more viscous it tends to become. In order to ensure the coatability of the coating solution, the polyarylate resin concentration in the coating solution is made relatively low. However, a coating solution with a relatively low polyarylate resin concentration tends to flow in the direction of gravity and takes a relatively long time to dry. Therefore, the charge transport layer formed by dip coating tends to be thin at the top and thick at the bottom, and this tendency is more pronounced the thicker the charge transport layer is made. Uneven thickness of the charge transport layer in the axial direction of the photoconductor causes uneven charging of the photoconductor.

[0027] In order to solve the above problems, the photoreceptor according to this embodiment has a charge generating layer below the charge transport layer that is thinner at one end and thicker at the other end than at the center. When forming a charge transport layer on a charge generation layer by dip coating, it is presumed that the uniformity of the thickness of the charge transport layer is improved by the following mechanism when the dip coating is performed with the thinner end of the charge generation layer above the direction of gravity and the thicker end of the charge generation layer below the direction of gravity. When the thickness of the upper end of the charge generating layer is thinner than that of the central portion, the thinner upper end is more dry, so the coating liquid for forming the charge transport layer is more likely to adhere to the upper end, and the coating liquid is prevented from flowing down from the upper end, which is thought to suppress the charge transport layer at the upper end from becoming thinner. In addition, the fact that the thickness of the upper end of the charge generating layer is thinner than that of the central portion itself is thought to make the coating liquid for forming the charge transport layer more likely to remain at the upper end, which is thought to suppress the charge transport layer at the upper end from becoming thinner. When the thickness of the upper end of the charge generating layer is the same as or thicker than that of the central portion, the coating liquid for forming the charge transport layer is more likely to flow down in the direction of gravity, which is thought to suppress the charge transport layer at the upper end from becoming thinner. If the thickness of the lower end of the charge generating layer is thicker than that of the central portion, the thicker lower end has a lower degree of dryness, so that the coating liquid for forming the charge transport layer is less likely to adhere to the lower end, and the coating liquid flows down from the lower end, which is thought to suppress the thickening of the charge transport layer at the lower end. Also, the fact that the thickness of the lower end of the charge generating layer is thicker than that of the central portion itself is thought to suppress the thickening of the charge transport layer at the lower end. If the thickness of the lower end of the charge generating layer is the same as or thinner than that of the central portion, it is thought that the coating liquid for forming the charge transport layer accumulates thickly at the lower end, which is thought to make it easier for the charge transport layer at the lower end to thicken. Due to the above mechanism, it is believed that the charge generating layer being thin at one end and thick at the other end increases the uniformity of the layer thickness of the charge transport layer, and as a result, it is believed that charging unevenness is less likely to occur on the photoconductor.

[0028] However, the charge generating layer is originally a thin layer. The thickness of the charge generating layer is generally less than 1 μm, and is at most a few μm. Therefore, the difference in the thickness of the charge generating layer in the axial direction is minute, and it may be difficult to detect the difference in the layer thickness. Therefore, the photoconductor according to this embodiment employs the absorbance at wavelength 678nn in the absorption spectrum of the photosensitive layer as an index of the thickness of the charge generation layer. Charge generation materials having absorption at wavelength 678nn are often used as the charge generation material of the charge generation layer. It can be considered that the higher the absorbance at wavelength 678nn, the thicker the charge generation layer is, and the lower the absorbance at wavelength 678nn, the thinner the charge generation layer is. By comparing the absorbance at wavelength 678nn at the center of the photoconductor, one end, and the other end, the thickness of the charge generation layer can be known. The absorption spectrum of the photosensitive layer is measured as follows.

[0029] The photosensitive layer is peeled off, and the photosensitive layer is cut into squares of axial direction x circumferential direction = 1 cm x 1 cm from positions (M), (U), and (L). The position (M) is the axial center of the photoreceptor. The position (U) is a position 0.40L away from the center toward one end in the axial direction of the photoconductor, where L is the entire length of the photoconductor in the axial direction. The position (L) is a position 0.40L away from the center of the photoconductor in the axial direction toward the other end, where L is the total length of the photoconductor in the axial direction. The photosensitive layer is cut out from four positions at 90° intervals in the circumferential direction at positions (M), (U), and (L), respectively. Therefore, four square membranes of 1 cm x 1 cm are obtained at positions (M), (U), and (L), respectively. Four membranes are immersed in 100 mL of tetrahydrofuran for each position to prepare a solution. This solution is used as a sample to measure the absorption spectrum using a UV-Vis spectrophotometer (e.g., Hitachi U2000) to detect the absorbance at a wavelength of 678 nN. The absorbance at wavelength 678nn of the photosensitive layer at position (M) is called Im. The absorbance at a wavelength of 678nn relating to the photosensitive layer at position (U) is called Iu. The absorbance at a wavelength of 678nn for the photosensitive layer at position (L) is called Il.

[0030] In the photoconductor according to this embodiment, Iu and Im have the relationship of formula (1): Iu≦0.95×Im. If Iu exceeds 0.95×Im, one end of the charge generating layer (the upper end when the charge transport layer is formed by dip coating) is not as thin as desired, and the charge transport layer is likely to become thin at this portion. From the viewpoint of preventing the charge transport layer from becoming thin at this portion, Iu and Im have a relationship represented by formula (1), preferably a relationship represented by formula (1-1), more preferably a relationship represented by formula (1-2), and even more preferably a relationship represented by formula (1-3). Equation (1): Iu≦0.95×Im Formula (1-1): 0.70×Im <Iu≦0.95×Im Formula (1-2): 0.75×Im≦Iu≦0.95×Im Formula (1-3): 0.75×Im <Iu≦0.95×Im

[0031] In the photoconductor according to this embodiment, Il and Im have a relationship of formula (2): 1.05×Im≦Il. If Il is less than 1.05×Im, the other end of the charge generating layer (the lower end when the charge transport layer is formed by dip coating) is not as thick as desired, and the charge transport layer is likely to thicken at this location. From the viewpoint of suppressing the charge transport layer from thickening at this location, Il and Im have the relationship of formula (2), preferably the relationship of formula (2-1), more preferably the relationship of formula (2-2), and further preferably the relationship of formula (2-3). Equation (2): 1.05×Im≦Il Formula (2-1): 1.05×Im≦Il<1.30×Im Formula (2-2): 1.05×Im≦Il≦1.25×Im Formula (2-3): 1.05×Im≦Il<1.25×Im

[0032] The following means can be used to make the thickness of the charge generating layer thinner at one end portion and thicker at the other end portion than at the central portion so as to satisfy formulas (1) and (2). When the charge generation layer is formed by a dip coating method, the speed at which the conductive substrate is pulled upward in the direction of gravity from the coating liquid for forming the charge generation layer is controlled so that the pulling speed at the upper end is less than the pulling speed at the central part and less than the pulling speed at the lower end. When the charge generating layer is formed by a blade coating method, the blade pressure against the conductive substrate is controlled so that the blade pressure at one end>the blade pressure at the center>the blade pressure at the other end. When the charge generating layer is formed by spray coating, the amount of the coating liquid sprayed is controlled so that the amount at one end is smaller than the amount at the center and smaller than the amount at the other end. In each of the above means, the "center portion" is preferably a region that occupies 60% to 80% of the total axial length L of the photoconductor. In the center portion, the lifting speed, blade pressure, or spray amount is preferably constant.

[0033] The polyarylate resin contained in the charge transport layer and each layer of the photoreceptor will be described in detail below.

[0034] [Polyarylate resin (1)] The polyarylate resin, which is the binder resin of the charge transport layer, is preferably a polyarylate resin (1) having at least a dicarboxylic acid unit (A) and a diol unit (B). The polyarylate resin (1) may contain a dicarboxylic acid unit other than the dicarboxylic acid unit (A). The polyarylate resin (1) may contain a diol unit other than the diol unit (B).

[0035] The dicarboxylic acid unit (A) is a structural unit represented by the following formula (A).

[0036] [ka]

[0037] In formula (A), Ar A1 and Ar A2 each independently represents an aromatic ring which may have a substituent; L A is a single bond or a divalent linking group, n A1 is 0, 1 or 2.

[0038] Ar A1 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, and the benzene ring and the naphthalene ring are preferred.

[0039] Ar A1 The hydrogen atoms on the aromatic ring of may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. A1 When the aromatic ring is substituted, the substituent is preferably 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.

[0040] Ar A2 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, and the benzene ring and the naphthalene ring are preferred.

[0041] Ar A2 The hydrogen atoms on the aromatic ring of may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. A2 When the aromatic ring is substituted, the substituent is preferably 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.

[0042] L A When is a divalent linking group, examples of the divalent linking group include an oxygen atom, a sulfur atom, -C(Ra 1 )(Ra 2 )-, where Ra 1 and Ra 2 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms; 1 and Ra 2 may be bonded to form a cyclic alkyl group.

[0043] Ra 1 and Ra 2 The alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0044] Ra 1 and Ra 2 The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6.

[0045] 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 either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, more preferably 6.

[0046] The dicarboxylic acid unit (A) preferably contains at least one selected from the group consisting of dicarboxylic acid units (A1) represented by the following formula (A1), dicarboxylic acid units (A2) represented by the following formula (A2), dicarboxylic acid units (A3) represented by the following formula (A3), and dicarboxylic acid units (A4) represented by the following formula (A4). The dicarboxylic acid unit (A) preferably contains at least one selected from the group consisting of dicarboxylic acid units (A2), dicarboxylic acid units (A3) and dicarboxylic acid units (A4), more preferably contains at least one selected from the group consisting of dicarboxylic acid units (A2) and dicarboxylic acid units (A4), and even more preferably contains dicarboxylic acid units (A2).

[0047] [ka]

[0048] In formula (A1), n 101 is an integer between 0 and 4, and n 101 Ra 101 each independently represents 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 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0049] [ka]

[0050] In formula (A2), n 201 and n 202are each independently an integer of 0 to 4, 201 Ra 201 and n 202 Ra 202 each independently represents 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 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. n 202 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0051] [ka]

[0052] In formula (A3), n 301 and n 302 are each independently an integer of 0 to 4, 301 Ra 301 and n 302 Ra 302 each independently represents 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 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. n 302 is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0053] [ka]

[0054] In formula (A4), n 401 is an integer between 0 and 6, and n 401 Ra 401each independently represents 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 is preferably an integer of 0 or more and 4 or less, more preferably 0, 1 or 2, and even more preferably 0.

[0055] Ra in formula (A1) 101 , Ra in formula (A2) 201 and Ra 202 , Ra in formula (A3) 301 and Ra 302 And Ra in formula (A4) 401 Since the specific and preferred embodiments of are the same, hereinafter, Ra 101 , Ra 201 , Ra 202 , Ra 301 , Ra 302 and Ra 401 These will be collectively referred to as "Ra".

[0056] The alkyl group having 1 to 10 carbon atoms related to Ra 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. Examples of the linear alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group. Examples of the branched alkyl group having 3 to 10 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group. Examples of the cyclic alkyl group having 3 to 10 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl group formed by linking these monocyclic alkyl groups.

[0057] The aryl group having 6 to 12 carbon atoms related to Ra may be either a monocyclic or polycyclic ring. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a biphenyl group, a 1-naphthyl group, and a 2-naphthyl group.

[0058] 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 the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of the branched alkoxy group having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0059] Specific examples of the dicarboxylic acid unit (A1) include the following dicarboxylic acid units (A1-1) to (A1-9), but the dicarboxylic acid unit (A1) is not limited thereto.

[0060] [ka]

[0061] Specific examples of the dicarboxylic acid unit (A2) include the following dicarboxylic acid units (A2-1) to (A2-3), but the dicarboxylic acid unit (A2) is not limited thereto.

[0062] [ka]

[0063] Specific examples of the dicarboxylic acid unit (A3) include the dicarboxylic acid units (A3-1) and (A3-2), but the dicarboxylic acid unit (A3) is not limited thereto.

[0064] [ka]

[0065] Specific examples of the dicarboxylic acid unit (A4) include the following dicarboxylic acid units (A4-1) to (A4-3), but the dicarboxylic acid unit (A4) is not limited thereto.

[0066] [ka]

[0067] The dicarboxylic acid unit (A) preferably contains at least one selected from the group consisting of the above specific examples (A1-1), (A1-7), (A2-3), (A3-2) and (A4-3), more preferably contains at least one selected from the group consisting of (A2-3), (A3-2) and (A4-3), even more preferably contains at least one selected from the group consisting of (A2-3) and (A4-3), and most preferably contains at least (A2-3).

[0068] The total mass proportion of the dicarboxylic acid units (A1) to (A4) in the polyarylate resin (1) is preferably 15 mass % or more and 60 mass % or less. When the total mass proportion of the dicarboxylic acid units (A1) to (A4) is 15 mass% or more, the photosensitive layer has good abrasion resistance. From this viewpoint, the total mass proportion of the dicarboxylic acid units (A1) to (A4) is more preferably 20 mass% or more, and further preferably 25 mass% or more. When the total mass proportion of the dicarboxylic acid units (A1) to (A4) is 60 mass% or less, peeling of the photosensitive layer can be suppressed. From this viewpoint, the total mass proportion of the dicarboxylic acid units (A1) to (A4) is more preferably 55 mass% or less, and further preferably 50 mass% or less. The dicarboxylic acid units (A1) to (A4) contained in the polyarylate resin (1) may be of one type or of two or more types.

[0069] Examples of the dicarboxylic acid units (A) other than the dicarboxylic acid units (A1) to (A4) include aliphatic dicarboxylic acid (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid) units, alicyclic dicarboxylic acid (e.g., cyclohexanedicarboxylic acid) units, and lower alkyl ester units thereof (e.g., having 1 to 5 carbon atoms). The polyarylate resin (1) may contain one or more types of dicarboxylic acid units.

[0070] The dicarboxylic acid unit (A) contained in the polyarylate resin (1) may be of one type or of two or more types.

[0071] The diol unit (B) is a structural unit represented by the following formula (B).

[0072] [ka]

[0073] In formula (B), Ar B1 and Ar B2each independently represents 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 )-, and n B1 is 0, 1 or 2. Rb 1 and Rb 2 each independently represents 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; Rb 1 and Rb 2 may be bonded to form a cyclic alkyl group.

[0074] Ar B1 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, and the benzene ring and the naphthalene ring are preferred.

[0075] Ar B1 The hydrogen atoms on the aromatic ring of may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. B1 When the aromatic ring is substituted, the substituent is preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0076] Ar B2 The aromatic ring may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, and the benzene ring and the naphthalene ring are preferred.

[0077] Ar B2 The hydrogen atoms on the aromatic ring of may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, or the like. B2 When the aromatic ring is substituted, the substituent is preferably 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.

[0078] Rb 1 and Rb 2 The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 18 carbon atoms, more preferably 1 to 14 carbon atoms, and even more preferably 1 to 10 carbon atoms.

[0079] Rb 1 and Rb 2 The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6.

[0080] Rb 1 and Rb 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. Rb 1 and Rb 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, more preferably 6.

[0081] The diol unit (B) preferably contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the formula (B2), a diol unit (B3) represented by the formula (B3), a diol unit (B4) represented by the formula (B4), a diol unit (B5) represented by the formula (B5), a diol unit (B6) represented by the formula (B6), a diol unit (B7) represented by the formula (B7), and a diol unit (B8) represented by the formula (B8). The diol unit (B) more preferably contains at least one selected from the group consisting of diol units (B1), diol units (B2), diol units (B4), diol units (B5) and diol units (B6), even more preferably contains at least one selected from the group consisting of diol units (B1), diol units (B2), diol units (B5) and diol units (B6), even more preferably contains at least one selected from the group consisting of diol units (B1), diol units (B2) and diol units (B6), and most preferably contains at least one selected from the group consisting of diol units (B1) and diol units (B2).

[0082] [ka]

[0083] In formula (B1), Rb 101 is a branched alkyl group having 4 to 20 carbon atoms, and Rb 201 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 401 , Rb 501 , Rb 801 and Rb 901 each independently represents 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.

[0084] Rb 101 The carbon number of the branched alkyl group having 4 to 20 carbon atoms in the formula Rb is preferably 4 to 16, more preferably 4 to 12, and even more preferably 4 to 8. 101Specific examples of the aryl group include an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, an isododecyl group, a sec-dodecyl group, a tert-dodecyl group, a tert-tetradecyl group, and a tert-pentadecyl group.

[0085] [ka]

[0086] In formula (B2), Rb 102 is a linear alkyl group having 4 to 20 carbon atoms, and Rb 202 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 402 , Rb 502 , Rb 802 and Rb 902 each independently represents 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.

[0087] Rb 102 The carbon number of the linear alkyl group having 4 to 20 carbon atoms in the formula Rb is preferably 4 to 16, more preferably 4 to 12, and even more preferably 4 to 8. 102 Specific examples of the aryl group include an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, a tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, and an n-icosyl group.

[0088] [ka]

[0089] In formula (B3), Rb 113 and Rb 213 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; d is an integer of 7 to 15; Rb 403 , Rb 503 , Rb 803 and Rb 903 each independently represents 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.

[0090] 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 such groups 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 such groups include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a cyclopropoxy group, and a cyclobutoxy group. Rb 113 and Rb 213 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0091] [ka]

[0092] In formula (B4), Rb 104 and Rb 204 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 404 , Rb 504 , Rb804 and Rb 904 each independently represents 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.

[0093] 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. 104 Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

[0094] [ka]

[0095] 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, 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 each independently represents 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.

[0096] Ar 105 The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6. Ar 105 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. Ar 105The aryl group in the aralkyl group having 7 to 20 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in the aryl group is preferably 6 to 10, more preferably 6. Examples of the aralkyl group having 7 to 20 carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, a 4-phenylbutyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, a phenylnonyl group, a naphthylmethyl group, a naphthylethyl group, an anthrathylmethyl group, and a phenyl-cyclopentylmethyl group.

[0097] [ka]

[0098] 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; Rb 406 , Rb 506 , Rb 806 and Rb 906 each independently represents 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.

[0099] 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 such groups include a methyl group, an ethyl group, and an n-propyl group. Rb 116 and Rb 216The 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 such groups include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a cyclopropoxy group, and a cyclobutoxy group. Rb 116 and Rb 216 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0100] [ka]

[0101] In formula (B7), Rb 407 , Rb 507 , Rb 807 and Rb 907 each independently represents 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.

[0102] [ka]

[0103] In formula (B8), Rb 408 , Rb 508 , Rb 808 and Rb 908 each independently represents 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.

[0104] Rb in formula (B1) 201 , Rb in formula (B2) 202 , Rb in formula (B4) 204 and Rb of formula (B5) 205 Since the specific and preferred forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 201 , Rb202 , Rb 204 and Rb 205 "Rb 200 " is collectively described as such.

[0105] 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 has 1 carbon atom. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

[0106] Rb in formula (B1) 401 , Rb in formula (B2) 402 , Rb in formula (B3) 403 , Rb in formula (B4) 404 , Rb in formula (B5) 405 , Rb in formula (B6) 406 , Rb in formula (B7) 407 and Rb of formula (B8) 408 Since the specific and preferred forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 401 , Rb 402 , Rb 403 , Rb 404 , Rb 405 , Rb 406 , Rb 407 and Rb 408 "Rb 400 " is collectively described as such.

[0107] Rb 400 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0108] 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 the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of the branched alkoxy group having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0109] Rb 400 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0110] Rb in formula (B1) 501 , Rb in formula (B2) 502 , Rb in formula (B3) 503 , Rb in formula (B4) 504 , Rb in formula (B5) 505 , Rb in formula (B6) 506 , Rb in formula (B7) 507 and Rb of formula (B8) 508 Since the specific and preferred forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 501 , Rb 502 , Rb 503 , Rb 504 , Rb 505 , Rb 506 , Rb 507 and Rb 508 "Rb 500 " is collectively referred to as ".

[0111] Rb 500 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0112] 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 the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of the branched alkoxy group having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0113] Rb 500 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0114] Rb in formula (B1) 801 , Rb in formula (B2)802 , Rb in formula (B3) 803 , Rb in formula (B4) 804 , Rb in formula (B5) 805 , Rb in formula (B6) 806 , Rb in formula (B7) 807 and Rb of formula (B8) 808 Since the specific and preferred forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 801 , Rb 802 , Rb 803 , Rb 804 , Rb 805 , Rb 806 , Rb 807 and Rb 808 "Rb 800 " is collectively referred to as ".

[0115] Rb 800 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0116] 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 the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of the branched alkoxy group having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0117] Rb 800 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0118] Rb in formula (B1) 901 , Rb in formula (B2) 902 , Rb in formula (B3) 903 , Rb in formula (B4) 904 , Rb in formula (B5) 905 , Rb in formula (B6) 906 , Rb in formula (B7) 907 and Rb of formula (B8) 908 Since the specific and preferred forms of Rb are the same as those of Rb, Rb will be referred to as Rb in the following. 901 , Rb 902 , Rb 903 , Rb 904 , Rb 905 , Rb 906 , Rb 907 and Rb 908 "Rb 900 " is collectively described as such.

[0119] Rb 900 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 to 3 carbon atoms, more preferably 1 or 2, and even more preferably 1. Examples of the linear alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the branched alkyl group having 3 or 4 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Examples of the cyclic alkyl group having 3 or 4 carbon atoms include a cyclopropyl group and a cyclobutyl group.

[0120] 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 the linear alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, and an n-hexyloxy group. Examples of the branched alkoxy group having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. Examples of the cyclic alkoxy group having 3 to 6 carbon atoms include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, and a cyclohexyloxy group.

[0121] Rb 900 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0122] Specific examples of the diol unit (B1) include diol units (B1-1) to (B1-6), but the diol unit (B1) is not limited thereto.

[0123] [ka]

[0124] Specific examples of the diol unit (B2) include the diol units (B2-1) to (B2-11), but the diol unit (B2) is not limited thereto.

[0125] [ka]

[0126] Specific examples of the diol unit (B3) include diol units (B3-1) to (B3-4), but the diol unit (B3) is not limited thereto.

[0127] [ka]

[0128] Specific examples of the diol unit (B4) include the diol units (B4-1) to (B4-7), but the diol unit (B4) is not limited thereto.

[0129] [ka]

[0130] Specific examples of the diol unit (B5) include the diol units (B5-1) to (B5-6), but the diol unit (B5) is not limited thereto.

[0131] [ka]

[0132] Specific examples of the diol unit (B6) include the diol units (B6-1) to (B6-4), but the diol unit (B6) is not limited thereto.

[0133] [ka]

[0134] Specific examples of the diol unit (B7) include diol units (B7-1) to (B7-3), but the diol unit (B7) is not limited thereto.

[0135] [ka]

[0136] Specific examples of the diol unit (B8) include the diol units (B8-1) to (B8-3), but the diol unit (B8) is not limited thereto.

[0137] [ka]

[0138] The diol unit (B) contained in the polyarylate resin (1) may be of one type or of two or more types.

[0139] The mass proportion of the diol units (B) in the polyarylate resin (1) is preferably 25 mass % or more and 80 mass % or less. When the mass proportion of the diol unit (B) is 25 mass% or more, peeling of the photosensitive layer can be suppressed. From this viewpoint, the mass proportion of the diol unit (B) is more preferably 30 mass% or more, and further preferably 35 mass% or more. When the mass proportion of the diol unit (B) is 80 mass% or less, the solubility in the coating solution for forming the photosensitive layer can be maintained and the abrasion resistance can be improved. From this viewpoint, the mass proportion of the diol unit (B) is more preferably 75 mass% or less, and further preferably 70 mass% or less.

[0140] Examples of the diol units other than the diol units (B) include aliphatic diol units (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, and neopentyl glycol) and alicyclic diol units (e.g., cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A). The polyarylate resin (1) may contain one or more types of these diol units.

[0141] The terminals of the polyarylate resin (1) may be capped or modified with a terminal capping agent or a molecular weight regulator used during production. Examples of the terminal capping agent or the molecular weight regulator include a monohydric phenol, a monovalent acid chloride, a monohydric alcohol, and a monovalent carboxylic acid. 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 -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 the monovalent acid chloride include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetic acid chloride, butyric acid chloride, octylic acid chloride, benzoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and substituted versions of these. 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 the monovalent carboxylic acid include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0142] The weight average molecular weight of the polyarylate resin and the polyarylate resin (1) is preferably 50,000 or more, more preferably 80,000 or more, and even more preferably 100,000 or more, from the viewpoint of the abrasion resistance of the charge transport layer. The weight average molecular weight of the polyarylate resin and the polyarylate resin (1) is preferably 300,000 or less, more preferably 250,000 or less, and even more preferably 200,000 or less, from the viewpoint of achieving a certain level of polyarylate resin concentration in the coating liquid for forming the charge transport layer. The molecular weights of the polyarylate resin and the polyarylate resin (1) are polystyrene-equivalent molecular weights measured by gel permeation chromatography (GPC), which uses tetrahydrofuran as an eluent.

[0143] The polyarylate resin (1) can be obtained by polycondensing a monomer that gives the dicarboxylic acid unit (A) and a monomer that gives the diol unit (B) with other monomers as required, in a conventional manner. Examples of the method for polycondensing the monomers include interfacial polymerization, solution polymerization, and melt polymerization. The interfacial polymerization is a polymerization method for obtaining a polyester by mixing a divalent carboxylic acid halide dissolved in an organic solvent that is not compatible with water with a divalent alcohol dissolved in an aqueous alkali solution. Examples of literature related to the interfacial polymerization include WME ARECSON, J. Poly. Sci., XL399, 1959, and JP-B-1959. The interfacial polymerization has a faster reaction rate than the solution polymerization, and therefore can suppress hydrolysis of the divalent carboxylic acid halide, resulting in a high molecular weight polyarylate resin.

[0144] [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.). Examples of conductive substrates include paper, resin films, belts, etc. 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 material having a volume resistivity of 1×10 13 This means that the resistance is less than Ωcm.

[0145] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center line average roughness Ra of 0.04 μm to 0.5 μm in order to suppress interference fringes that occur when irradiating 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 extending the life of the conductive substrate since it suppresses the occurrence of defects due to unevenness on the surface.

[0146] Examples of methods for roughening the surface include wet honing, which involves spraying an abrasive suspended in water onto the conductive substrate; centerless grinding, in which the conductive substrate is pressed against a rotating grindstone and continuously ground; and anodizing.

[0147] As a method for roughening the surface, there can be mentioned a method in which, without roughening the surface of the conductive substrate, a conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the surface is roughened by the particles dispersed in the layer.

[0148] In the roughening treatment by anodization, an oxide film is formed on the surface of a conductive substrate made of metal (e.g., aluminum) by anodizing the substrate in an electrolyte solution using the substrate as the anode. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodization is chemically active in its original state, easily contaminated, and has a large resistance variation depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film, in which the micropores of the oxide film are filled by volume expansion caused by hydration reaction in pressurized steam or boiling water (metal salts such as nickel may be added) to change the film into a more stable hydrated oxide.

[0149] The thickness of the anodic oxide film is preferably, for example, from 0.3 μm to 15 μm. If the thickness is within this range, the film tends to exhibit a barrier property against injection and tends to suppress an increase in residual potential due to repeated use.

[0150] The conductive substrate may be subjected to a treatment with an acidic treatment solution or a boehmite treatment. Treatment with an acid treatment liquid is carried out, for example, as follows. First, an acid treatment liquid containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The compounding ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acid treatment liquid are, for example, in the range of 10% by mass to 11% by mass for phosphoric acid, 3% by mass to 5% by mass for chromic acid, and 0.5% by mass to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% by mass to 18% by mass. The treatment temperature is preferably, for example, 42° C. to 48° C. The film thickness of the coating is preferably 0.3 μm to 15 μm.

[0151] 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 the material with heated steam at 90°C to 120°C for 5 to 60 minutes. The thickness of the coating is preferably 0.1 μm to 5 μm. This may be further anodized using an electrolyte solution having low coating solubility, such as adipic acid, boric acid, borates, phosphates, phthalates, maleates, benzoates, tartrates, or citrates.

[0152] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0153] For example, inorganic particles have a powder resistance (volume resistivity) of 1×10 2 Ωcm or more 1×10 11 Examples of such particles include inorganic particles with a particle size of Ωcm or less. Among these, examples of inorganic particles having the above-mentioned resistance value include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, and zinc oxide particles are particularly preferred.

[0154] The specific surface area of ​​inorganic particles by the BET method is, for example, 10 m 2 / g or higher is preferable. The volume average particle size of the inorganic particles is, for example, from 50 nm to 2000 nm (preferably from 60 nm to 1000 nm).

[0155] The content of the inorganic particles is, for example, preferably from 10% by mass to 80% by mass, more preferably from 40% by mass to 80% by mass, based on the binder resin.

[0156] The inorganic particles may be surface-treated. Two or more types of inorganic particles having different surface treatments or different particle sizes may be used in combination.

[0157] Examples of the surface treatment agent include a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, etc. In particular, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

[0158] 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.

[0159] Silane coupling agents may be used in combination of two or more kinds. 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-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0160] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

[0161] The amount of the surface treatment agent to be used is preferably, for example, 0.5% by mass or more and 10% by mass or less based on the inorganic particles.

[0162] Here, it is preferable that the undercoat layer contains an electron accepting compound (acceptor compound) together with the inorganic particles, from the viewpoints of improving the long-term stability of electrical properties and carrier blocking properties.

[0163] Examples of the electron-accepting compound include electron-transporting substances such as 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. In particular, the electron-accepting compound is preferably a compound having an anthraquinone structure. Examples of the compound having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds, and more specifically, anthraquinone, alizarin, quinizarin, anthrarufin, and purpurin.

[0164] The electron accepting compound may be contained in the undercoat layer in a dispersed state together with the inorganic particles, or may be contained in a state of being attached to the surfaces of the inorganic particles.

[0165] The method for attaching the electron accepting compound to the surface of the inorganic particles may be, for example, a dry method or a wet method.

[0166] The dry method is, for example, a method in which an electron-accepting compound is attached to the surface of inorganic particles by dropping an electron-accepting compound directly or dissolved in an organic solvent or spraying it together with dry air or nitrogen gas while stirring inorganic particles with a mixer or the like that exerts a large shearing force. The dropping or spraying of the electron-accepting compound is preferably performed at a temperature below the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be performed at 100° C. or higher. The temperature and time of baking are not particularly limited as long as electrophotographic properties can be obtained.

[0167] The wet method is a method in which, for example, an electron-accepting compound is added while dispersing inorganic particles in a solvent by stirring, ultrasonic waves, a sand mill, an attritor, a ball mill, etc., and the inorganic particles are stirred or dispersed, and then the solvent is removed to attach the electron-accepting compound to the surface of the inorganic particles. The solvent is removed, for example, by filtration or distillation. After the solvent is removed, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as electrophotographic properties are obtained. In the wet method, moisture contained in the inorganic particles may be removed before adding the electron-accepting compound, and examples of such methods include a method of removing the moisture while stirring and heating in a solvent, and a method of removing the moisture by azeotropy with the solvent.

[0168] The attachment of the electron accepting compound may be carried out before or after the inorganic particles are subjected to a surface treatment with a surface treatment agent, or the attachment of the electron accepting compound and the surface treatment with the surface treatment agent may be carried out simultaneously.

[0169] The content of the electron accepting compound is, for example, from 0.01% by mass to 20% by mass, and preferably from 0.01% by mass to 10% by mass, based on the inorganic particles.

[0170] Examples of the binder resin used in the undercoat layer include known materials such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; and silane coupling agents. Examples of the binder resin used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline, etc.), and the like.

[0171] Among these, the binder resin used in the undercoat layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and in particular, a resin obtained by reacting at least one resin selected from the group consisting of thermosetting resins such as urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins, with a curing agent is preferred. When two or more of these binder resins are used in combination, the mixing ratio is set as necessary.

[0172] The undercoat layer may contain various additives for improving electrical properties, environmental stability, and image quality. Examples of the additives include known materials such as polycyclic condensation and azo-based electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, silane coupling agents, etc. As described above, silane coupling agents are used for surface treatment of inorganic particles, and may also be added to the undercoat layer as an additive.

[0173] Examples of silane coupling agents as additives include vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, and the like.

[0174] Examples of the zirconium chelate compound include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate 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.

[0175] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-n-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.

[0176] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0177] These additives may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0178] The undercoat layer preferably has a Vickers hardness of 35 or more. The surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to between 1 / (4n) (n is the refractive index of the upper layer) and 1 / 2 of the wavelength λ of the exposure laser used in order to suppress moire images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of the resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. The surface of the undercoat layer may be polished to adjust the surface roughness. Examples of the polishing method include buffing, sandblasting, wet honing, grinding, and the like.

[0179] The formation of the undercoat layer is not particularly limited, and a known formation method can be used. For example, the undercoat layer can be formed by forming a coating film of a coating solution for forming the undercoat layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary.

[0180] Examples of the solvent for preparing the coating liquid for forming the undercoat layer include known organic solvents, such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include ordinary organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0181] Examples of the method for dispersing the inorganic particles when preparing the coating liquid for forming the undercoat layer include known methods such as those using a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0182] Examples of the method for applying the coating liquid for forming the undercoat layer onto the conductive substrate include conventional methods such as dip coating, blade coating, wire bar coating, spray coating, bead coating, air knife coating, and curtain coating.

[0183] The average thickness of the undercoat layer is preferably from 10 μm to 40 μm, more preferably from 14 μm to 36 μm, even more preferably from 18 μm to 32 μm, and even more preferably from 20 μm to 30 μm.

[0184] [Middle layer] An intermediate layer may further be provided between the undercoat layer and the photosensitive layer. The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include polymer compounds such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, and melamine resins. The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used in the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in the intermediate layer may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0185] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0186] The formation of the intermediate layer is not particularly limited, and a known formation method can be used. For example, the intermediate layer can be formed by forming a coating film of a coating solution for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary. The intermediate layer can be formed by any of the usual coating methods, such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating and curtain coating.

[0187] The thickness of the intermediate layer is preferably set in the range of, for example, 0.1 μm to 3 μm The intermediate layer may be used as an undercoat layer.

[0188] [Charge generation layer] The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. The charge generation layer may also be a vapor deposition layer of the charge generation material. The vapor deposition layer of the charge generation material is suitable for use with a non-coherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array.

[0189] Examples of the charge generating material include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0190] Among these, in order to correspond to the 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, at least one selected from the group consisting of hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine and titanyl phthalocyanine is preferable, hydroxygallium phthalocyanine and / or chlorogallium phthalocyanine is more preferable, and hydroxygallium phthalocyanine is even more preferable. Hydroxygallium phthalocyanine has an absorption peak at a wavelength of 678nn.

[0191] In order to accommodate laser exposure in the near ultraviolet region, preferred charge generating materials include condensed aromatic pigments such as dibromoanthanthrone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and bisazo pigments.

[0192] The above charge generating materials may be used when using incoherent light sources such as LEDs and organic EL image arrays that emit light at a central wavelength of 450 nm to 780 nm, but from the viewpoint of resolution, when using a thin photosensitive layer of 20 μm or less, the electric field strength in the photosensitive layer becomes high, and a decrease in charging due to charge injection from the substrate, so-called black spots, is likely to occur as an image defect. This becomes more noticeable when using charge generating materials that are p-type semiconductors such as trigonal selenium and phthalocyanine pigments and are prone to generating dark current.

[0193] In contrast, when n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge generating materials, dark current is unlikely to occur, and image defects called black spots can be suppressed even in thin films. The n-type is determined by the polarity of the flowing photocurrent using the commonly used time-of-flight method, and those that are more likely to pass electrons as carriers than holes are considered to be n-type.

[0194] The binder resin used in the charge generating layer may be selected from a wide range of insulating resins, and may also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, polysilane, and the like. Examples of binder resins include polyvinyl butyral resins, polyarylate resins (polycondensates of bisphenols and aromatic dicarboxylic acids, etc.), polycarbonate resins, polyester resins, phenoxy resins, vinyl chloride-vinyl acetate copolymers, polyamide resins, acrylic resins, polyacrylamide resins, polyvinylpyridine resins, cellulose resins, urethane resins, epoxy resins, casein, polyvinyl alcohol resins, polyvinylpyrrolidone resins, etc. Here, "insulating" refers to a material having a volume resistivity of 1×10 13 This means that the resistance is Ωcm or more. These binder resins may be used alone or in combination of two or more.

[0195] The compounding ratio of the charge generating material to the binder resin is preferably within a range of 10:1 to 1:10 by mass.

[0196] The charge generating layer may contain other known additives.

[0197] The formation of the charge generation layer is not particularly limited, and a known formation method is used, for example, by forming a coating film of a coating solution for forming the charge generation layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary. The formation of the charge generation layer may be performed by vapor deposition of the charge generation material. The formation of the charge generation layer by vapor deposition is particularly suitable when a condensed ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0198] Examples of the solvent for preparing the coating liquid for forming the charge generating layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene, etc. These solvents may be used alone or in combination of two or more.

[0199] Examples of methods for dispersing particles (e.g., charge generating material) in the coating liquid for forming a charge generating layer include media dispersers such as ball mills, vibration ball mills, attritors, sand mills, and horizontal sand mills, and medialess dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion liquid is dispersed by penetrating a fine flow path under high pressure. During this dispersion, it is effective to adjust the average particle size of the charge generating material in the coating liquid 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.

[0200] Examples of methods for applying the coating liquid for forming the charge generating layer onto the undercoat layer (or onto the intermediate layer) include conventional methods such as dip coating, blade coating, wire bar coating, spray coating, bead coating, air knife coating, and curtain coating. The method for forming the charge generating layer is preferably a dip coating method from the viewpoint of productivity in continuously forming the charge generating layer and the charge transport layer.

[0201] The average thickness of the charge generating layer is set in the range of, for example, 0.05 μm or more and 5.0 μm or less, 0.10 μm or more and 2.0 μm or less, or 0.15 μm or more and 1.0 μm or less.

[0202] [Charge transport layer] The charge transport layer is, for example, a layer containing a charge transport material and a binder resin, and may be a layer containing a polymer charge transport material.

[0203] Examples of the charge transport material include electron transporting compounds such as 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. Examples of the charge transport material include hole transporting compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination, but are not limited to these.

[0204] Examples of the polymer charge transport material include known chemical substances having charge transport properties, such as poly-N-vinylcarbazole and polysilane. For example, a polyester-based polymer charge transport material is preferred. The polymer charge transport material may be used alone or in combination with a binder resin.

[0205] Examples of the charge transport material or polymer charge transport material include polycyclic aromatic compounds, aromatic nitro compounds, aromatic amine compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds (particularly 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 to 0080 of JP 2021-117377 A, paragraphs 0046 to 0048 of JP 2019-035900 A, paragraphs 0052 to 0053 of JP 2019-012141 A, paragraphs 0122 to 0134 of JP 2021-071565 A, and paragraphs 0122 to 0134 of JP 2021-015223 A Examples of the compounds include those described in paragraphs 0101 to 0110 of JP 2013-097300 A, paragraphs 0116 of WO 2019 / 070003 A, paragraphs 0103 to 0107 of JP 2018-159087 A, and paragraphs 0102 to 0113 of JP 2021-148818 A.

[0206] From the viewpoint of charge mobility, the charge transport material preferably contains at least one selected from the group consisting of a compound (C1) represented by the following formula (C1), a compound (C2) represented by the following formula (C2), a compound (C3) represented by the following formula (C3), and a compound (C4) represented by the following formula (C4).

[0207] [ka]

[0208] In formula (C1), Ar T1 , Ar T2 and Ar T3 are each independently an aryl group, -C6H4-C(R T4 )=C(R T5)(R T6 ) or -CH-CH=CH-CH=C(R T7 )(R T8 ) R T4 , R T5 , R T6 , R T7 and R T8 R is independently a hydrogen atom, an alkyl group, or an aryl group. T5 and R T6 When is an aryl group, the aryl groups are connected to each other by -C(R 51 )(R 52 )- and / or -C(R 61 )=C(R 62 R may be linked to the ring via a divalent group represented by the formula: 51 , R 52 , R 61 and R 62 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0209] The group in formula (C1) may be substituted with a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0210] From the viewpoint of charge mobility, the compound (C1) is preferably an aryl group or -CH-CH=CH-CH=C(R T7 )(R T8 ) is preferred, and a compound (C'1) represented by the following formula (C'1) is more preferred.

[0211] [ka]

[0212] In formula (C'1), R T111 , R T112 , R T121 , R T122 , R T131 and R T132are each 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.

[0213] [ka]

[0214] In formula (C2), R T201 , R T202 , R T211 and R T212 each independently represents 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, -C(R T21 )=C(R T22 )(R T23 ) or -CH=CH-CH=C(R T24 )(R T25 ) R T21 , R T22 , R T23 , R T24 and R T25 R is independently a hydrogen atom, an alkyl group, or an aryl group. T221 and R T222 are each independently a hydrogen atom, a halogen atom, an alkyl group having from 1 to 5 carbon atoms, or an alkoxy group having from 1 to 5 carbon atoms. Tm1, Tm2, ​​Tn1, and Tn2 are each independently 0, 1, or 2.

[0215] The group in formula (C2) may be substituted with a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0216] From the viewpoint of charge mobility, the compound (C2) is preferably an alkyl group, an aryl group, or a -CH=CH-CH=C(R T24 )(R T25) is preferred, and an alkyl group, an aryl group, or a -CH=CH-CH=C(R T24 )(R T25 ) is more preferred.

[0217] [ka]

[0218] In formula (C3), R T301 , R T302 , R T311 and R T312 each independently represents 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, -C(R T31 )=C(R T32 )(R T33 ) or -CH=CH-CH=C(R T34 )(R T35 ) R T31 , R T32 , R T33 , R T34 and R T35 R is independently a hydrogen atom, an alkyl group, or an aryl group. T321 , R T322 and R T331 are each 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.

[0219] The group in formula (C3) may be substituted with a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0220] [ka]

[0221] In formula (C4), R T401 , R T402 , R T411 and R T412 each independently represents 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, -C(R T41 )=C(R T42 )(R T43 ) or -CH=CH-CH=C(R T44 )(R T45 ) R T41 , R T42 , R T43 , R T44 and R T45 R is independently a hydrogen atom, an alkyl group, or an aryl group. T421 , R T422 and R T431 each independently represents a hydrogen atom, a halogen atom, an alkyl group having from 1 to 5 carbon atoms, or an alkoxy group having from 1 to 5 carbon atoms. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 each independently represent 0, 1, or 2.

[0222] The group in formula (C4) may be substituted with a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0223] The content of the charge transport material in the charge transport layer is preferably 20% by mass or more and 70% by mass or less based on the total mass of the charge transport layer.

[0224] The charge transport layer contains at least a polyarylate resin as a binder resin, and preferably contains at least the polyarylate resin (1). The proportion of the polyarylate resin in the total amount of the binder resin contained in the charge transport layer is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more. The proportion of the polyarylate resin (1) in the total amount of the binder resin contained in the charge transport layer is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0225] An example of an embodiment of the charge transport layer contains polyarylate resin and polycarbonate resin as binder resins, and in this case, the mass ratio of the two resins, polyarylate resin:polycarbonate resin, is preferably 95:5 to 40:60. When the polyarylate resin (1) and the polycarbonate resin are used in combination, the mass ratio of the two resins, polyarylate resin (1):polycarbonate resin, is preferably 95:5 to 40:60.

[0226] The polycarbonate resin is preferably a polycarbonate resin having continuous structural units having an aromatic ring, and specific examples thereof include the polycarbonate resins used in the examples described below.

[0227] The charge transport layer may contain other binder resins other than polyarylate resin and polycarbonate resin. Examples of other binder resins include polyester resins other than polyarylate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, polysilanes, etc. These binder resins are used alone or in combination of two or more.

[0228] The charge transport layer may contain other known additives, such as an antioxidant, a leveling agent, a defoaming agent, a filler, and a viscosity modifier.

[0229] The formation of the charge transport layer is not particularly limited, and a known formation method can be used. For example, the charge transport layer can be formed by forming a coating film of a coating liquid for forming the charge transport layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0230] Examples of solvents for preparing the coating liquid for forming the charge transport layer include ordinary organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene, ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride, and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents may be used alone or in combination of two or more.

[0231] Examples of the coating method for applying the coating liquid for forming the charge transport layer onto the charge generating layer include conventional methods such as dip coating, blade coating, wire bar coating, spray coating, bead coating, air knife coating and curtain coating. The method for forming the charge transport layer is preferably a dip coating method from the viewpoint of productivity of the photoreceptor.

[0232] The average thickness of the charge transport layer is 30 μm or more, preferably 34 μm or more, and more preferably 38 μm or more, from the viewpoint of extending the life of the photoreceptor. The average thickness of the charge transport layer is preferably 50 μm or less, more preferably 47 μm or less, and even more preferably 45 μm or less, from the viewpoint of suppressing unevenness in the layer thickness. The average thickness of the charge transport layer is the arithmetic mean of the values ​​measured using an optical interference film thickness meter, and the measurements were taken at 12 locations in total, at 90° intervals around the circumference, at positions (M), (U), and (L).

[0233] [Protective layer] A protective layer is provided on the photosensitive layer as necessary for the purpose of, for example, preventing chemical changes in the photosensitive layer when the photosensitive layer is charged and further improving the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a layer composed of a cured film (crosslinked film) as the protective layer. Examples of such a layer include the following layers 1) and 2).

[0234] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton in the same molecule (i.e., a layer containing a polymer or crosslinked product of the reactive group-containing charge transport material). 2) A layer composed of a cured film of a composition containing a non-reactive charge transport material and a reactive group-containing non-charge transport material that does not have a charge transport skeleton and has a reactive group (i.e., a layer containing a non-reactive charge transport material and a polymer or crosslinked body of the reactive group-containing non-charge transport material).

[0235] The reactive group of the reactive group-containing charge transport material may be a chain polymerizable group, an epoxy group, -OH, -OR (wherein R represents an alkyl group), -NH2, -SH, -COOH, or -SiR. Q1 3-Qn (OR Q2 ) Qn [However, R Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group; R Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group; Qn represents an integer of 1 to 3.

[0236] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, and is, for example, a functional group having a group containing at least a carbon double bond.Specific examples include a group containing at least one selected from a vinyl group, a vinyl ether group, a vinyl thioether group, a phenylvinyl group, a vinylphenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof.Among them, the chain polymerizable group is preferably a group containing at least one selected from a vinyl group, a phenylvinyl group, a vinylphenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof, because of its excellent reactivity.

[0237] The charge transporting skeleton of the reactive group-containing charge transporting material is not particularly limited as long as it is a known structure in electrophotographic photoreceptors, and examples thereof include a skeleton derived from a nitrogen-containing hole transporting compound such as a triarylamine compound, a benzidine compound, a hydrazone compound, etc., and a structure conjugated with a nitrogen atom. Among these, a triarylamine skeleton is preferred.

[0238] The reactive group-containing charge transport material having a reactive group and a charge transporting skeleton, the non-reactive charge transport material, and the reactive group-containing non-charge transport material may be selected from known materials.

[0239] The protective layer may contain other known additives.

[0240] The formation of the protective layer is not particularly limited, and a known formation method can be used. For example, the protective layer can be formed by forming a coating film of a coating solution for forming a protective layer in which the above components are added to a solvent, drying the coating film, and, if necessary, subjecting it to a curing treatment such as heating.

[0241] Examples of solvents for preparing a coating solution for forming a protective layer include aromatic solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, ether solvents such as tetrahydrofuran and dioxane, cellosolve solvents such as ethylene glycol monomethyl ether, and alcohol solvents such as isopropyl alcohol and butanol. These solvents may be used alone or in combination of two or more. The coating liquid for forming the protective layer may be a solvent-free coating liquid.

[0242] Examples of a method for applying the protective layer-forming coating liquid onto a photosensitive layer (e.g., a charge transport layer) include conventional methods such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating.

[0243] The thickness of the protective layer is set, for example, preferably in the range of 1 μm or more and 20 μm or less, and more preferably in the range of 2 μm or more and 10 μm or less.

[0244] <Image forming apparatus, process cartridge> The image forming apparatus according to the present embodiment includes an electrophotographic photoreceptor, a charging device that charges the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, and a transfer device that transfers the toner image to the surface of a recording medium. The electrophotographic photoreceptor according to the present embodiment is applied as the electrophotographic photoreceptor.

[0245] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as an apparatus including a fixing device that fixes a toner image transferred onto the surface of a recording medium; an apparatus of a direct transfer type that directly transfers a toner image formed on the surface of an electrophotographic photosensitive member onto a recording medium; an apparatus of an intermediate transfer type that primarily transfers a toner image formed on the surface of an electrophotographic photosensitive member onto the surface of an intermediate transfer member, and then secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium; an apparatus including a cleaning device that cleans the surface of an electrophotographic photosensitive member before charging after the transfer of a toner image; an apparatus including a static elimination device that irradiates the surface of an electrophotographic photosensitive member with static elimination light to eliminate static electricity before charging after the transfer of a toner image; and an apparatus including an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

[0246] In the case of an intermediate transfer type device, the transfer device is configured to have, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer device which primarily transfers the toner image formed on the surface of an electrophotographic photosensitive body onto the surface of the intermediate transfer body, and a secondary transfer device which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

[0247] The image forming apparatus according to the present embodiment may be either a dry development type image forming apparatus or a wet development type image forming apparatus (a development type using a liquid developer).

[0248] In the image forming apparatus according to the present embodiment, for example, a portion including an electrophotographic photosensitive member may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member according to the present embodiment is preferably used. The process cartridge may include, in addition to the electrophotographic photosensitive member, at least one selected from the group consisting of a charging device, an electrostatic latent image forming device, a developing device, and a transfer device.

[0249] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. Principal parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0250] FIG. 2 is a schematic diagram showing an example of the image forming apparatus according to the present embodiment. As shown in FIG. 2, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 via the intermediate transfer body 50, and the intermediate transfer body 50 is disposed with a part of it in contact with the electrophotographic photoreceptor 7. Although not shown, the image forming apparatus 100 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 (a primary transfer device), and the secondary transfer device (not shown) correspond to an example of a transfer device.

[0251] 2 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) integrally within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is disposed so as to come into contact with the surface of the electrophotographic photoreceptor 7. The cleaning member may not be in the form of the cleaning blade 131, but may be a conductive or insulating fibrous member, which may be used alone or in combination with the cleaning blade 131.

[0252] FIG. 2 shows an example of an image forming apparatus including a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of the electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists in cleaning, which are arranged as needed.

[0253] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0254] -Charging device- As the charging device 8, for example, a contact type charger using a conductive or semiconductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. Also, a non-contact type roller charger, a scorotron charger or corotron charger that utilizes corona discharge, or other chargers known per se, can be used.

[0255] -Exposure equipment- The exposure device 9 may be, for example, an optical device that exposes the surface of the electrophotographic photoreceptor 7 with light such as semiconductor laser light, LED light, or liquid crystal shutter light in a predetermined image. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photoreceptor. The wavelength of the semiconductor laser is mainly near infrared light having an oscillation wavelength of about 780 nm. However, it is not limited to this wavelength, and a laser having an oscillation wavelength of 600 nm or a blue laser having an oscillation wavelength of 400 nm to 450 nm may also be used. In addition, a surface-emitting laser light source capable of outputting multiple beams is also effective for forming a color image.

[0256] -Developing device- The developing device 11 may be, for example, a general developing device that develops by contacting or non-contacting a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected according to the purpose. For example, it may be a known developing device that has a function of attaching a one-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, roller, or the like. Among them, it is preferable to use a developing roller that holds a developer on its surface.

[0257] The developer used in the developing device 11 may be a one-component developer containing only toner, or may be a two-component developer containing toner and a carrier. The developer may be magnetic or non-magnetic. Known developers are used.

[0258] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131. In addition to the cleaning blade type, a fur brush cleaning type or a simultaneous development and cleaning type may also be adopted.

[0259] -Transfer device- Examples of the transfer device 40 include known transfer chargers such as a contact type transfer charger using a belt, roller, film, rubber blade, etc., and a scorotron transfer charger or corotron transfer charger that utilizes corona discharge.

[0260] -Intermediate transfer body- A belt-like intermediate transfer belt containing semiconductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. is used as the intermediate transfer body 50. The intermediate transfer body may be in the form of a drum other than a belt.

[0261] FIG. 3 is a schematic diagram showing another example of the image forming apparatus according to the present embodiment. 3 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 photosensitive body 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. EXAMPLES

[0262] Hereinafter, the embodiments of the present invention will be described in detail with reference to examples, but the embodiments of the present invention are not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are by mass. In the following description, unless otherwise specified, synthesis, production, processing, measurement, etc. were carried out at room temperature (25° C.±3° C.).

[0263] <Synthesis of polyarylate resin (1)> Polyarylate resins (1-1) to (1-3) shown in Table 1 were synthesized. A2-3 in Table 1 is a specific example of the dicarboxylic acid unit (A) described above. B1-4 and the like shown in Table 1 are specific examples of the diol unit (B) described above.

[0264] [Table 1]

[0265] <Production of photoconductors> [Example 1] - Formation of undercoat layer - As a conductive substrate, an aluminum cylindrical tube having an outer diameter of 30 mm, a length of 250 mm, and a wall thickness of 1 mm was prepared.

[0266] Zinc oxide (average particle size 70 nm, specific surface area 15 m 2 100 parts of a silane coupling agent (trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) was added to the mixture and stirred for 2 hours. The toluene was then distilled off under reduced pressure, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent.

[0267] 110 parts of the surface-treated zinc oxide was mixed with 500 parts of tetrahydrofuran by stirring, and a solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added thereto, followed by stirring for 5 hours at 50° C. Thereafter, the solid content was filtered off by reduced pressure filtration and dried under reduced pressure at 60° C. to obtain zinc oxide with alizarin added thereto.

[0268] 100 parts of a solution of 60 parts of alizarin-added zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, product name: Sumidur 3175, manufactured by Sumitomo Bayern Urethane Co., Ltd.), and 15 parts of butyral resin (product name: S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) dissolved in 68 parts of methyl ethyl ketone was mixed with 5 parts of methyl ethyl ketone, and the mixture was dispersed for 2 hours in a sand mill using glass beads of 1 mm diameter to obtain a dispersion. 0.005 parts of dioctyltin dilaurate as a catalyst and 4 parts of silicone resin particles (product name: Tospearl 145, manufactured by Momentive Performance Materials Co., Ltd.) were added to the dispersion to obtain a coating liquid for forming an undercoat layer. The coating liquid for forming the undercoat layer was applied to the outer peripheral surface of a conductive substrate by a dip coating method, and the coating was dried and cured at 170°C for 40 minutes to form an undercoat layer with an average thickness of 20 μm.

[0269] - Formation of charge generation layer - A mixture 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 the X-ray diffraction spectrum using CuKα characteristic X-rays) as a charge generating material, 10 parts of vinyl chloride-vinyl acetate copolymer resin (product name: VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using glass beads with a diameter of 1 mm for 4 hours. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion and stirred to obtain a coating solution for forming a charge generating layer. When the conductive substrate having the undercoat layer was immersed in the coating liquid and pulled up from the coating liquid in the direction of gravity, the pulling speed was controlled so as to obtain the absorbance ratio shown in Table 2, with the pulling speed at the top end being slower than that at the center, and the pulling speed at the bottom end being faster than that at the center. The "center" here was defined as a region occupying 50% of the total length L of the photoconductor in the axial direction.

[0270] - Formation of charge transport layer - 60 parts of polyarylate resin (1-1) as a binder resin and 40 parts of CTM-1 as a charge transport material were dissolved in 270 parts of tetrahydrofuran and 30 parts of toluene to obtain a coating liquid for forming a charge transport layer. The coating liquid for forming a charge transport layer was dip-coated on the charge generation layer. Then, the coating was dried at 145°C for 30 minutes to form a charge transport layer. The average thickness of the charge transport layer is as shown in Table 2.

[0271] [ka]

[0272] [Examples 2 to 5 and Comparative Example 1] A photoreceptor was prepared in the same manner as in Example 1, except that the speed ratio of the speed at which the charge generating layer was withdrawn from the coating solution when the charge generating layer was dip-coated was changed.

[0273] [Examples 6 to 7] Each photoreceptor was prepared in the same manner as in Example 1, except that the type of polyarylate resin used in forming the charge transport layer was changed to the type shown in Table 2.

[0274] [Examples 8 to 9] Each photoreceptor was prepared in the same manner as in Example 1, except that in forming the charge transport layer, part of the polyarylate resin was replaced with a polycarbonate resin. The structures of the polycarbonate resins (1) and (2) are as follows.

[0275] [ka]

[0276] <Photoreceptor performance evaluation> The photoreceptor of each of the examples and comparative examples was mounted in an electrophotographic image forming apparatus DocuCentre-V C7775 (FUJIFILM Business Innovation Co., Ltd.).

[0277] [Wear resistance] In a low-temperature, low-humidity environment with a temperature of 10°C and a relative humidity of 15%, full-page halftone images with a density of 30% were continuously printed on A3-sized plain paper, 10,000 sheets each for yellow, magenta, cyan, and black, for a total of 40,000 sheets. The average thickness (nm) of the charge transport layer was measured before and after this image formation, and the difference in the average thickness before and after image formation was taken as the amount of wear (nm). A Fisher Instruments Permascope was used as the film thickness measurement device. The amount of wear was classified as follows. The results are shown in Table 2. A: Abrasion amount is less than 800 nm B: Abrasion amount is 800nm ​​or more and less than 1600nm C: Abrasion amount is 1600nm or more and less than 2400nm D: Abrasion amount is 2400 nm or more

[0278] [Uneven charging] A surface potential probe connected to a surface potential meter (Trek 334, manufactured by Trek Corporation) was placed at positions corresponding to positions (U) and (L) and 1 mm away from the surface of the photoreceptor. In an environment with a temperature of 24°C and a relative humidity of 55%, 10 sheets of A3-sized plain paper were printed with a full-surface halftone image with an image density of 30%. When the image was formed on the last sheet, the charge potential of the photoconductor was measured, and the difference between the charge potential at position (U) and the charge potential at position (L) was calculated and classified as follows. The results are shown in Table 2. A: The difference in charged potential is less than 10V B: The difference in charged potential is 10V or more and less than 20V C: The difference in charged potential is 20V or more

[0279] In Table 2, "Iu / Im / Il" is a relative value when the value of Im is set to 1.

[0280] [Table 2]

[0281] The electrophotographic photoreceptor, process cartridge, and image forming apparatus of the present disclosure include the following aspects: Each formula representing a compound is the same as the formula with the same number described above.

[0282] (((1))) A conductive substrate; and a photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate, The charge transport layer has an average thickness of 30 μm or more, the charge transport layer contains a polyarylate resin, The absorption spectrum of the photosensitive layer measured after peeling it off and dissolving it in tetrahydrofuran satisfies the following formulas (1) and (2): Electrophotographic photoreceptor; Formula (1): Iu≦0.95×Im Formula (2): 1.05×Im≦Il When the total length of the electrophotographic photosensitive member in the axial direction is L, Im is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from the center in the axial direction of the electrophotographic photosensitive member, Iu is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward one end in the axial direction of the electrophotographic photosensitive member, Il is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward the other end in the axial direction of the electrophotographic photosensitive member. (((2))) 2. The electrophotographic photoreceptor according to claim 1, wherein the absorption spectrum measured by peeling off the photosensitive layer and dissolving it in tetrahydrofuran satisfies the following formulas (1-3) and (2-3): Formula (1-3): 0.75×Im <Iu≦0.95×Im Formula (2-3): 1.05×Im≦Il<1.25×Im When the total length of the electrophotographic photosensitive member in the axial direction is L, Im is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from the center in the axial direction of the electrophotographic photosensitive member, Iu is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward one end in the axial direction of the electrophotographic photosensitive member, Il is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward the other end in the axial direction of the electrophotographic photosensitive member. (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), wherein the charge generating layer contains hydroxygallium phthalocyanine. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the polyarylate resin contained in the charge transport layer has a weight average molecular weight of 80,000 or more. (((5))) The electrophotographic photoreceptor according to any one of (((1))) to (((4))), wherein the charge transport layer further contains a polycarbonate resin. (((6))) The electrophotographic photoreceptor according to any one of (((1))) to (((5))), wherein the polyarylate resin comprises a polyarylate resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B). (((7))) The electrophotographic photoreceptor according to (((6))), wherein the polyarylate resin (1) contains at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by formula (A1), a dicarboxylic acid unit (A2) represented by formula (A2), a dicarboxylic acid unit (A3) represented by formula (A3), and a dicarboxylic acid unit (A4) represented by formula (A4). (((8))) The electrophotographic photoreceptor according to (((6))) or (((7))), wherein the polyarylate resin (1) comprises at least one selected from the group consisting of a diol unit (B1) represented by formula (B1), a diol unit (B2) represented by formula (B2), a diol unit (B3) represented by formula (B3), a diol unit (B4) represented by formula (B4), a diol unit (B5) represented by formula (B5), a diol unit (B6) represented by formula (B6), a diol unit (B7) represented by formula (B7), and a diol unit (B8) represented by formula (B8). (((9))) The electrophotographic photoreceptor according to any one of (((6))) to (((8))), wherein the polyarylate resin (1) contains at least one selected from the group consisting of a dicarboxylic acid unit (A2) represented by formula (A2) and a dicarboxylic acid unit (A4) represented by formula (A4). (((10))) The electrophotographic photoreceptor according to any one of (((6))) to (((9))), wherein the polyarylate resin (1) contains at least one selected from the group consisting of a diol unit (B1) represented by formula (B1) and a diol unit (B2) represented by formula (B2). (((11))) An electrophotographic photoreceptor according to any one of (((1))) to (((10))), A process cartridge that is detachably attached to an image forming apparatus. (((12))) An electrophotographic photoreceptor according to any one of (((1))) to (((10))); a charging device for charging a 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 an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; A transfer device that transfers the toner image onto a surface of a recording medium. Image forming device.

[0283] (((1))) According to the invention related to (((1)), (((3))), (((5)), (((6)), (((7)), (((8)), (((9))) or (((10)), an electrophotographic photoreceptor which is excellent in wear resistance and which is less susceptible to uneven charging, as compared with an electrophotographic photoreceptor which does not satisfy one or both of formulas (1) and (2), is provided. According to the invention related to (((2))), there is provided an electrophotographic photoreceptor which is excellent in wear resistance and which is less susceptible to charging unevenness, as compared with an electrophotographic photoreceptor which does not satisfy one or both of formula (1-3) and formula (2-3). According to the invention related to (((4))), an electrophotographic photoreceptor having excellent abrasion resistance is provided, as compared with a case in which the weight-average molecular weight of the polyarylate resin is less than 80,000. According to the invention related to (((11))), there is provided a process cartridge in which the electrophotographic photosensitive member is excellent in wear resistance and is less susceptible to uneven charging, as compared with a process cartridge including an electrophotographic photosensitive member that does not satisfy one or both of formulas (1) and (2). According to the invention related to (((12))), there is provided an image forming apparatus in which the abrasion resistance of the electrophotographic photosensitive member is excellent and charging unevenness is less likely to occur, compared to an image forming apparatus including an electrophotographic photosensitive member that does not satisfy one or both of formulas (1) and (2). [Explanation of symbols]

[0284] 1 conductive substrate, 2 subbing layer, 3 charge generation layer, 4 charge transport layer, 5 photosensitive layer, 10A photoreceptor

[0285] 7 electrophotographic photosensitive member, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 40 transfer device, 50 intermediate transfer body, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll-shaped), 133 fibrous member (flat brush-shaped), 300 process cartridge

Claims

1. A conductive substrate; and a photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate, The charge transport layer has an average thickness of 30 μm or more, the charge transport layer contains a polyarylate resin, The absorption spectrum measured by peeling off the photosensitive layer and dissolving it in tetrahydrofuran satisfies the following formulas (1) and (2): Electrophotographic photoreceptor; Formula (1): Iu≦0.95×Im Formula (2): 1.05×Im≦Il When the total length of the electrophotographic photosensitive member in the axial direction is L, Im is the absorbance at a wavelength of 678 nn of the photosensitive layer peeled off from the center in the axial direction of the electrophotographic photosensitive member, Iu is the absorbance at a wavelength of 678 nn of the photosensitive layer peeled off from a position 0.40 L from the center toward one end in the axial direction of the electrophotographic photosensitive member, Il is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward the other end in the axial direction of the electrophotographic photosensitive member.

2. 2. The electrophotographic photoreceptor according to claim 1, wherein the absorption spectrum measured by peeling off the photosensitive layer and dissolving it in tetrahydrofuran satisfies the following formulas (1-3) and (2-3): Formula (1-3): 0.75×Im<Iu≦0.95×Im Formula (2-3): 1.05×Im≦Il<1.25×Im When the total length of the electrophotographic photosensitive member in the axial direction is L, Im is the absorbance at a wavelength of 678 nn of the photosensitive layer peeled off from the center in the axial direction of the electrophotographic photosensitive member, Iu is the absorbance at a wavelength of 678 nn of the photosensitive layer peeled off from a position 0.40 L from the center toward one end in the axial direction of the electrophotographic photosensitive member, Il is the absorbance at a wavelength of 678nn of the photosensitive layer peeled off from a position of 0.40L from the center toward the other end in the axial direction of the electrophotographic photosensitive member.

3. 2. The electrophotographic photoreceptor according to claim 1, wherein the charge generating layer comprises hydroxygallium phthalocyanine.

4. 2. The electrophotographic photoreceptor according to claim 1, wherein the polyarylate resin contained in the charge transport layer has a weight average molecular weight of 80,000 or more.

5. 2. The electrophotographic photoreceptor of claim 1, wherein the charge transport layer further comprises a polycarbonate resin.

6. 2. The electrophotographic photoreceptor according to claim 1, wherein the polyarylate resin comprises a polyarylate resin (1) having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by the following formula (B): 【Chemistry 1】 In formula (A), Ar Ａ１ and Ar Ａ２ each independently represents an aromatic ring which may have a substituent; L Ａ is a single bond or a divalent linking group, n Ａ１ is 0, 1 or 2. In formula (B), Ar Ｂ１ and Ar Ｂ２ each independently represents 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. １ and Rb ２ each independently represents 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; Rb １ and Rb ２ may be bonded to form a cyclic alkyl group.

7. 7. The electrophotographic photoreceptor according to claim 6, wherein the polyarylate resin (1) contains at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by the following formula (A1), a dicarboxylic acid unit (A2) represented by the following formula (A2), a dicarboxylic acid unit (A3) represented by the following formula (A3), and a dicarboxylic acid unit (A4) represented by the following formula (A4). 【Chemistry 2】 In formula (A1), n １０１ is an integer of 0 to 4, １０１ Ra １０１ each independently represents an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A2), n ２０１ and n ２０２ are each independently an integer of 0 to 4, ２０１ Ra ２０１ and n ２０２ Ra ２０２ each independently represents an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A3), n ３０１ and n ３０２ are each independently an integer of 0 to 4, ３０１ Ra ３０１ and n ３０２ Ra ３０２ each independently represents an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A4), n ４０１ is an integer of 0 to 6, ４０１ Ra ４０１ each independently represents 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.

8. 7. The electrophotographic photoreceptor according to claim 6, wherein the polyarylate resin (1) contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the following formula (B2), a diol unit (B3) represented by the following formula (B3), a diol unit (B4) represented by the following formula (B4), a diol unit (B5) represented by the following formula (B5), a diol unit (B6) represented by the following formula (B6), a diol unit (B7) represented by the following formula (B7), and a diol unit (B8) represented by the following formula (B8). 【Chemistry 3】 【Chemistry 4】 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 each independently represents 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 (B2), Rb １０２ is a linear alkyl group having 4 to 20 carbon atoms; Rb ２０２ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; Rb ４０２ , Rb ５０２ , Rb ８０２ and Rb ９０２ each independently represents 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 (B3), Rb １１３ and Rb ２１３ 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; d is an integer of 7 to 15; ４０３ , Rb ５０３ , Rb ８０３ and Rb ９０３ each independently represents 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 (B4), Rb １０４ and Rb ２０４ each independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; ４０４ , Rb ５０４ , Rb ８０４ and Rb ９０４ each independently represents 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 is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, Rb ２０５ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; Rb ４０５ , Rb ５０５ , Rb ８０５ and Rb ９０５ each independently represents 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 (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; Rb ４０６ , Rb ５０６ , Rb ８０６ and Rb ９０６ each independently represents 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 (B7), Rb ４０７ , Rb ５０７ , Rb ８０７ and Rb ９０７ each independently represents 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 (B8), Rb ４０８ , Rb ５０８ , Rb ８０８ and Rb ９０８ each independently represents 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.

9. 7. The electrophotographic photoreceptor according to claim 6, wherein the polyarylate resin (1) contains at least one selected from the group consisting of a dicarboxylic acid unit (A2) represented by the following formula (A2) and a dicarboxylic acid unit (A4) represented by the following formula (A4): 【Chemistry 5】 In formula (A2), n ２０１ and n ２０２ are each independently an integer of 0 to 4, ２０１ Ra ２０１ and n ２０２ Ra ２０２ each independently represents an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A4), n ４０１ is an integer of 0 to 6, ４０１ Ra ４０１ each independently represents 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.

10. 7. The electrophotographic photoreceptor according to claim 6, wherein the polyarylate resin (1) contains 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 the following formula (B2): 【Chemistry 6】 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 each independently represents 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 (B2), Rb １０２ is a linear alkyl group having 4 to 20 carbon atoms; Rb ２０２ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; Rb ４０２ , Rb ５０２ , Rb ８０２ and Rb ９０２ each independently represents 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.

11. The electrophotographic photoreceptor according to any one of claims 1 to 10 is provided, A process cartridge that is detachably attached to an image forming apparatus.

12. An electrophotographic photoreceptor according to any one of claims 1 to 10, a charging device for charging a 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 an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; A transfer device that transfers the toner image onto a surface of a recording medium. Image forming device.

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