Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that is excellent in uniformity of electric potential distribution on a surface, and prevents the occurrence of an image defect even if it is dropped or left standing for a long period in a high temperature and high humidity environment.SOLUTION: An electrophotographic photoreceptor comprises a laminated photosensitive layer having a charge generating layer and a charge transport layer. The charge transport layer contains a charge transport material, and a polyester resin (1) having a dicarboxylic acid unit (A) and a diol unit (B). A molecular weight distribution curve of the polyester resin (1) included in the charge transport layer has at least two peaks. When the molecular weight of the maximum point of the peak with the minimum molecular weight is defined as Mmin, the molecular weight of the maximum point of the peak with the maximum molecular weight as Mmax, and the weight average molecular weight of the polyester resin (1) included in the charge transport layer as Mw, 50,000≤Mw≤200,000, and 0.4≤(Mmax-Mmin) / Mw≤5.0 are satisfied.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an electrophotographic photoreceptor comprising a conductive substrate and a laminated photosensitive layer having a charge generation layer and a charge transport layer, wherein the charge transport layer contains a polyester resin (1) having dicarboxylic acid units (A) represented by a predetermined formula (A) and diol units (B) represented by a predetermined formula (B), and a charge transport material, wherein the weight-average molecular weight Mw of the polyester resin (1) contained in the charge transport layer is A (10,000), the ratio M1 / M2 of the mass M1 of the charge transport material contained in the charge transport layer to the mass M2 of the charge transport layer is Cs, and the average thickness of the charge transport layer is Ds (μm), satisfying the following conditions: 5≦A≦40, 0.28≦Cs≦0.55, 27≦Ds≦50, and 2.5≦(A×Ds) / (Cs×100)≦70.0.

[0003] Patent Document 2 discloses an electrophotographic photoreceptor that includes a conductive substrate, an undercoat layer disposed on the conductive substrate, and a laminated photosensitive layer having a charge generation layer and a charge transport layer disposed on the undercoat layer, wherein the charge transport layer contains a charge transport material and a polyester resin, and where As (μm) is the average thickness of the charge transport layer and Bs (μm) is the average thickness of the undercoat layer, the relationships satisfying 27≦As≦50, 10≦Bs≦40, and 0.70≦As / Bs≦4.80. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-047285 [Patent Document 2] Japanese Patent Application Publication No. 2023-130296 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to provide an electrophotographic photoreceptor that has excellent uniformity in the potential distribution on its surface, is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time. [Means for solving the problem]

[0006] Specific means for solving the above problems include the following aspects: Each formula is the same as the formula with the same number described below.

[0007] <1> a conductive substrate; and a laminated photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate; the charge transport layer contains a charge transport material and a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B), The molecular weight distribution curve of the polyester resin (1) contained in the charge transport layer has at least two peaks, and when the molecular weight at the maximum point of the peak with the smallest molecular weight is defined as Mmin, the molecular weight at the maximum point of the peak with the largest molecular weight is defined as Mmax, and the weight average molecular weight of the polyester resin (1) contained in the charge transport layer is defined as Mw, the ranges of 50,000≦Mw≦200,000 and 0.4≦(Mmax−Mmin) / Mw≦5.0 are satisfied. Electrophotographic photoreceptor. <2> 0.5≦(Mmax-Mmin) / Mw≦4.5 is satisfied, <1> The electrophotographic photoreceptor according to claim 1. <3> Meets 80,000≦Mw≦150,000 <1> or <2> The electrophotographic photoreceptor according to claim 1. <4> The dicarboxylic acid unit (A) 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). <1> ~ <3> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <5> the dicarboxylic acid unit (A) contains at least one selected from the group consisting of the dicarboxylic acid unit (A2), the dicarboxylic acid unit (A3), and the dicarboxylic acid unit (A4); <4> The electrophotographic photoreceptor according to claim 1. <6> The diol unit (B) 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). <1> ~ <5> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <7> the diol unit (B) includes at least one selected from the group consisting of the diol unit (B1), the diol unit (B2), the diol unit (B5), and the diol unit (B6); <6> The electrophotographic photoreceptor according to claim 1. <8> A conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate, the single-layer photosensitive layer contains a charge transport material and a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B), the molecular weight distribution curve of the polyester resin (1) contained in the single-layer photosensitive layer has at least two peaks, the molecular weight at the maximum point of the peak with the smallest molecular weight is defined as Mmin, the molecular weight at the maximum point of the peak with the largest molecular weight is defined as Mmax, and the weight average molecular weight of the polyester resin (1) contained in the single-layer photosensitive layer is defined as Mw, and the ranges of 50,000≦Mw≦200,000 and 0.4≦(Mmax−Mmin) / Mw≦5.0 are satisfied; Electrophotographic photoreceptor. <9> 0.5≦(Mmax-Mmin) / Mw≦4.5 is satisfied, <8> The electrophotographic photoreceptor according to claim 1. <10> Meets 80,000≦Mw≦150,000 <8> or <9> The electrophotographic photoreceptor according to claim 1. <11> The dicarboxylic acid unit (A) 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> ~ <10> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <12> the dicarboxylic acid unit (A) contains at least one selected from the group consisting of the dicarboxylic acid unit (A2), the dicarboxylic acid unit (A3), and the dicarboxylic acid unit (A4); <11> The electrophotographic photoreceptor according to claim 1. <13> The diol unit (B) 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). <8> ~ <12> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <14> the diol unit (B) includes at least one selected from the group consisting of the diol unit (B1), the diol unit (B2), the diol unit (B5), and the diol unit (B6); <13> The electrophotographic photoreceptor according to claim 1. <15> <1> ~ <14> The electrophotographic photoreceptor according to any one of the above items is provided, Attaching to and detaching from the image forming device Process cartridge. <16> <1> ~ <14> an electrophotographic photoreceptor according to any one of the above items; a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; Image forming device. [Effects of the Invention]

[0008] <1> , <4> , <5> , <6> or <7> According to the present invention, an electrophotographic photoreceptor is provided which is provided with a laminated photosensitive layer, and which has excellent uniformity of surface potential distribution, and is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time, compared to an electrophotographic photoreceptor in which the polyester resin (1) contained in the charge transport layer has an Mw of less than 50,000 or more than 200,000, or (Mmax-Mmin) / Mw of less than 0.4 or more than 5.0. <2> According to the present invention, an electrophotographic photoreceptor is provided which is provided with a laminated photosensitive layer, and which has excellent uniformity of surface potential distribution, and is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time, compared to an electrophotographic photoreceptor in which the (Mmax-Mmin) / Mw of the polyester resin (1) contained in the charge transport layer is less than 0.5 or more than 4.5. <3> According to the present invention, an electrophotographic photoreceptor is provided which is provided with a laminated photosensitive layer, and which has excellent uniformity of surface potential distribution compared to an electrophotographic photoreceptor in which the polyester resin (1) contained in the charge transport layer has an Mw of less than 80,000 or more than 150,000, and which is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and which is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time. <8> , <11> , <12> , <13> or <14> According to the present invention, an electrophotographic photoreceptor is provided which is provided with a single-layer photosensitive layer, and which has excellent uniformity of surface potential distribution, and is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time, compared to an electrophotographic photoreceptor in which the Mw of the polyester resin (1) contained in the single-layer photosensitive layer is less than 50,000 or more than 200,000, or (Mmax-Mmin) / Mw is less than 0.4 or more than 5.0. <9> According to the present invention, an electrophotographic photoreceptor is provided which has a single-layer photosensitive layer, and which has excellent uniformity of surface potential distribution, and is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time, compared to an electrophotographic photoreceptor in which the (Mmax-Mmin) / Mw of the polyester resin (1) contained in the single-layer photosensitive layer is less than 0.5 or more than 4.5. <10> According to the present invention, an electrophotographic photoreceptor is provided which is provided with a single-layer photosensitive layer, and which has excellent uniformity of surface potential distribution compared to an electrophotographic photoreceptor in which the Mw of the polyester resin (1) contained in the single-layer photosensitive layer is less than 80,000 or more than 150,000, and which is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and which is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time. <15> According to the invention, a process cartridge is provided that has an electrophotographic photosensitive member that has excellent uniformity in the surface potential distribution, is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time. <16> According to the present invention, an image forming apparatus is provided that includes an electrophotographic photosensitive member that has excellent uniformity in the surface potential distribution, is less likely to produce image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to produce image defects even when left in a high-temperature, high-humidity environment for a long period of time. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a partial cross-sectional view showing an example of a layer structure of the electrophotographic photosensitive member according to the first embodiment. [Figure 2]FIG. 6 is a partial cross-sectional view showing an example of a layer structure of an electrophotographic photosensitive member according to a second embodiment. [Figure 3] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 4] FIG. 10 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010]

[0023] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

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

[0012] In the present disclosure, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B.

[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 embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these.

[0015] In the present disclosure, each component may contain multiple 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 composition may contain multiple types of particles corresponding to each component. 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, alkyl groups and alkylene groups include any of linear, branched and cyclic groups, unless otherwise specified. In the present disclosure, a hydrogen atom in an organic group, aromatic ring, linking group, alkyl group, alkylene group, aryl group, aralkyl group, alkoxy group, aryloxy group, or the like may be substituted with a halogen atom.

[0017] In the present disclosure, when a compound is represented 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.

[0018] In the present disclosure, the term "structural unit" of a copolymer or resin has the same meaning as a monomer unit.

[0019] <Electrophotographic photoreceptor> The present disclosure provides a first embodiment and a second embodiment of an electrophotographic photoreceptor (hereinafter also referred to as a "photoreceptor").

[0020] The photoreceptor according to the first embodiment includes a conductive substrate and a laminated photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate. The photoreceptor according to the first embodiment may further include other layers (for example, an undercoat layer, an intermediate layer). In the photoreceptor according to the first embodiment, it is preferable that the charge transport layer is a surface layer.

[0021] The photoreceptor according to the second embodiment includes a conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate. The photoreceptor according to the second embodiment may further include other layers (for example, an undercoat layer, an intermediate layer). In the photoreceptor according to the second embodiment, the single-layer photosensitive layer is preferably the surface layer.

[0022] FIG. 1 is a partial cross-sectional view schematically illustrating an example of the layer structure of a photoreceptor according to the first embodiment. Photoreceptor 10A shown in FIG. 1 has a laminated photosensitive layer. Photoreceptor 10A 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 form a photosensitive layer 5 (a so-called function-separated photosensitive layer). 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] Fig. 2 is a partial cross-sectional view schematically illustrating an example of the layer structure of a photoreceptor according to the second embodiment. The photoreceptor 10B shown in Fig. 2 has a single-layer photosensitive layer. The photoreceptor 10B has a structure in which an undercoat layer 2 and a photosensitive layer 5 are laminated in this order on a conductive substrate 1. The photoreceptor 10B may have an intermediate layer (not shown) between the undercoat layer 2 and the photosensitive layer 5. The undercoat layer 2 may or may not be present.

[0024] In the photoreceptor according to the first embodiment, the charge transport layer of the laminated photosensitive layer contains a charge transport material and a polyester resin (1), and the molecular weight distribution curve of the polyester resin (1) contained in the charge transport layer has at least two peaks, where Mmin is the molecular weight at the maximum point of the peak with the smallest molecular weight, Mmax is the molecular weight at the maximum point of the peak with the largest molecular weight, and Mw is the weight average molecular weight of the polyester resin (1) contained in the charge transport layer, the relationships 50,000≦Mw≦200,000 and 0.4≦(Mmax-Mmin) / Mw≦5.0 are satisfied.

[0025] In the photoreceptor according to the second embodiment, the single-layer photosensitive layer contains a charge transport material and a polyester resin (1), and the molecular weight distribution curve of the polyester resin (1) contained in the single-layer photosensitive layer has at least two peaks, where Mmin is the molecular weight at the maximum point of the peak with the smallest molecular weight, Mmax is the molecular weight at the maximum point of the peak with the largest molecular weight, and Mw is the weight-average molecular weight of the polyester resin (1) contained in the single-layer photosensitive layer, the relationships 50,000≦Mw≦200,000 and 0.4≦(Mmax−Mmin) / Mw≦5.0 are satisfied.

[0026] Hereinafter, when matters common to the first embodiment and the second embodiment are described, both embodiments will be collectively referred to as the present embodiment. When matters common to the charge transport layer and the single-layer type photosensitive layer are described, both layers will be collectively referred to as the photosensitive layer.

[0027] The photosensitive layer of the photoreceptor according to this embodiment contains a polyester resin (1). The polyester resin (1) has aromatic ring stacking that bonds resin molecules together through intermolecular forces, improving the abrasion resistance of the photosensitive layer.

[0028] In the photoreceptor according to this embodiment, the molecular weight distribution curve of the polyester resin (1) contained in the photosensitive layer has at least two peaks, and when the molecular weight at the maximum point of the peak with the smallest molecular weight is defined as Mmin, the molecular weight at the maximum point of the peak with the largest molecular weight is defined as Mmax, and the weight average molecular weight of the polyester resin (1) contained in the photosensitive layer is defined as Mw, the relationships 50,000≦Mw≦200,000 and 0.4≦(Mmax−Mmin) / Mw≦5.0 are satisfied. The photoreceptor according to this embodiment has the above-described configuration, and therefore has excellent uniformity of the potential distribution on the surface of the photoreceptor, and is less likely to produce image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to produce image defects even when left in a high-temperature, high-humidity environment for a long period of time.

[0029] The relatively low molecular weight polyester resin (1) is easily mixed with the charge transport material when preparing the coating solution for forming the photosensitive layer. By using the relatively low molecular weight polyester resin (1) to form the photosensitive layer, the dispersibility of the charge transport material in the photosensitive layer can be improved. As a result, the uniformity of the potential distribution on the surface of the photoreceptor is excellent. The photosensitive layer containing the polyester resin (1) having a relatively high molecular weight is less likely to soften even in a high-temperature, high-humidity environment (for example, a temperature of 40°C and a relative humidity of 85%), and therefore is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time. The photosensitive layer of the photoreceptor according to this embodiment exhibits the above-mentioned effects by containing both the polyester resin (1) having a relatively low molecular weight and the polyester resin (1) having a relatively high molecular weight.

[0030] The polyester resin (1) contained in the photosensitive layer has a molecular weight distribution curve with at least two peaks. A polyester resin (1) with a molecular weight distribution curve with only one peak is difficult to achieve both "uniformity of potential distribution" and "image quality after dropping and storage in a high-temperature, high-humidity environment."

[0031] If the Mw of the polyester resin (1) contained in the photosensitive layer is less than 50,000, the film tends to soften and flow at high temperatures, resulting in a deterioration in image quality after dropping or storage in a high-temperature, high-humidity environment. From the viewpoint of suppressing this phenomenon, the Mw of the polyester resin (1) contained in the photosensitive layer is 50,000 or more, preferably 80,000 or more, and more preferably 90,000 or more. If the Mw of the polyester resin (1) contained in the photosensitive layer exceeds 200,000, the dispersibility of the charge transport material decreases, and the uniformity of the potential distribution decreases. From the viewpoint of suppressing this phenomenon, the Mw of the polyester resin (1) contained in the photosensitive layer is 200,000 or less, preferably 150,000 or less, and more preferably 130,000 or less.

[0032] If the (Mmax-Mmin) / Mw of the polyester resin (1) contained in the photosensitive layer is less than 0.4, the low molecular weight component and the high molecular weight component are unlikely to exhibit their respective desirable functions, making it difficult to achieve both "uniformity of potential distribution" and "image quality after dropping and storage in a high-temperature, high-humidity environment." From the viewpoint of achieving both "uniformity of potential distribution" and "image quality after dropping and storage in a high-temperature, high-humidity environment," the (Mmax-Mmin) / Mw of the polyester resin (1) contained in the photosensitive layer is 0.4 or more, preferably 0.5 or more, and more preferably 0.6 or more.

[0033] If the (Mmax-Mmin) / Mw of the polyester resin (1) contained in the photosensitive layer exceeds 5.0, the disadvantages of the low-molecular-weight component and the high-molecular-weight component are emphasized (low-molecular-weight component: prone to softening and flow, high-molecular-weight component: poor dispersibility of the charge transport material), making it difficult to achieve both "uniformity of potential distribution" and "image quality after dropping and storage in a high-temperature, high-humidity environment." From the viewpoint of achieving both "uniformity of potential distribution" and "image quality after dropping and storage in a high-temperature, high-humidity environment," the (Mmax-Mmin) / Mw of the polyester resin (1) contained in the photosensitive layer is 5.0 or less, preferably 4.5 or less, and more preferably 4.0 or less.

[0034] In this embodiment, the molecular weight distribution curve, Mmin, Mmax, and weight average molecular weight Mw of the polyester resin (1) contained in the photosensitive layer (which is the charge transport layer of the multi-layer photosensitive layer in the first embodiment and the single-layer photosensitive layer in the second embodiment) are determined as follows. The photoreceptor is immersed in various solvents (which may be mixed solvents) to determine the solvent in which the photosensitive layer dissolves. The photoreceptor is immersed in a solvent in which the photosensitive layer dissolves to extract the constituent materials of the photosensitive layer. The solution from which the constituent materials of the photosensitive layer have been extracted is added dropwise to a poor solvent for polyester resin (1) (for example, a non-polar solvent such as hexane or toluene, or a lower alcohol such as methanol or isopropanol. The poor solvent may also be a mixed solvent) to reprecipitate the resin. If necessary, the reprecipitation process is repeated twice, and the reprecipitate is vacuum dried to obtain polyester resin (1). The molecular weight of the polyester resin (1) obtained by the above treatment is measured by GPC (gel permeation chromatography). The GPC apparatus is, for example, HLC-8120 (Tosoh Corporation), the column is, for example, TSKgel GMHHR-M + TSKgel GMHHR-M (7.8 mm I.D. × 30 cm) (Tosoh Corporation), and the solvent is tetrahydrofuran. Molecular weight calibration is performed using a monodisperse polystyrene standard sample, and the molecular weight Mmin at the maximum point of the peak with the minimum molecular weight, the molecular weight Mmax at the maximum point of the peak with the maximum molecular weight, and the weight average molecular weight Mw are determined.

[0035] The molecular weight distribution curve of the polyester resin (1) contained in the photosensitive layer can have at least two peaks by mixing two or more polyester resins (1) having different weight-average molecular weights and using the mixed polyester resin (1) to form the photosensitive layer. The two or more polyester resins (1) to be mixed may be the same or different in the type of constituent unit. When the weight average molecular weights of the polyester resins (1) to be mixed are resin a, resin b, resin c, ..., resin n, respectively, are Mw(a), Mw(b), Mw(c), ..., Mw(n), and the mass proportions of each are W(a), W(b), W(c), ..., W(n), the weight average molecular weight Mw(Mix) of the polyester resin (1) after mixing is Mw(Mix) = Σ(Mw(n) × W(n)). When two or more kinds of polyester resins (1) having different weight average molecular weights are mixed, they are mixed so that Mw(Mix) satisfies the relationship 50,000≦Mw(Mix)≦200,000. Furthermore, when two or more polyester resins (1) having different weight average molecular weights are mixed, they are mixed so that the difference ΔMw between the minimum and maximum values ​​of Mw(a), Mw(b), Mw(c), ..., Mw(n) and Mw(Mix) satisfy the relationship 0.4 × Mw(Mix) ≦ ΔMw ≦ 5.0 × Mw(Mix).

[0036] In the above, the two or more polyester resins (1) to be mixed may be the same or different in the type of structural unit. From the viewpoint of improving the dispersion uniformity of the charge transport material in the photosensitive layer, it is preferable that the two or more polyester resins (1) to be mixed have the same type of structural unit. In other words, it is preferable that the photosensitive layer contains one type of polyester resin (1) in the type of structural unit.

[0037] The polyester resin (1) contained in the photosensitive layer and each layer of the photoreceptor will be described in detail below.

[0038] [Polyester resin (1)] The photosensitive layer contains, as a binder resin, a polyester resin (1) having at least a dicarboxylic acid unit (A) and a diol unit (B). The polyester resin (1) may contain a dicarboxylic acid unit other than the dicarboxylic acid unit (A). The polyester resin (1) may contain a diol unit other than the diol unit (B).

[0039] The dicarboxylic acid unit (A) is a structural unit represented by the following formula (A).

[0040] [ka]

[0041] In formula (A), Ar A1 and Ar A2 each independently represents an aromatic ring which may have a substituent, and L A is a single bond or a divalent linking group, and n A1 is 0, 1 or 2.

[0042] 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, with a benzene ring and a naphthalene ring being preferred.

[0043] Ar A1The hydrogen atoms on the aromatic ring of Ar 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.

[0044] 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, with a benzene ring and a naphthalene ring being preferred.

[0045] Ar A2 The hydrogen atoms on the aromatic ring of Ar 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.

[0046] 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.

[0047] 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.

[0048] 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 in the aryl group is preferably 6 to 10, and more preferably 6.

[0049] 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.

[0050] The dicarboxylic acid unit (A) preferably 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 formula (A2), a dicarboxylic acid unit (A3) represented by the formula (A3), and a dicarboxylic acid unit (A4) represented by the formula (A4). The dicarboxylic acid unit (A) more preferably contains at least one selected from the group consisting of the dicarboxylic acid unit (A2), the dicarboxylic acid unit (A3), and the dicarboxylic acid unit (A4), and further preferably contains the dicarboxylic acid unit (A2).

[0051] [ka]

[0052] In formula (A1), n 101 is an integer between 0 and 4, and n 101 Ra 101 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 101is preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0.

[0053] [ka]

[0054] 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 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 201 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.

[0055] [ka]

[0056] 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 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 301 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.

[0057] [ka]

[0058] In formula (A4), n 401 is an integer between 0 and 6, and n 401 Ra 401 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 401 is preferably an integer of 0 or more and 4 or less, more preferably 0, 1 or 2, and even more preferably 0.

[0059] 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 Ra are the same as those of 101 , Ra 201 , Ra 202 , Ra 301 , Ra 302 and Ra 401 These will be collectively referred to as "Ra".

[0060] The alkyl group having 1 to 10 carbon atoms represented by Ra 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. 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 branched alkyl groups 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 groups formed by linking these monocyclic alkyl groups.

[0061] The aryl group having 6 to 12 carbon atoms for Ra may be either a monocyclic or polycyclic ring. The number of carbon atoms in 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.

[0062] The alkyl group in the alkoxy group having 1 to 6 carbon atoms, represented by 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 branched alkoxy groups 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.

[0063] Specific examples of the dicarboxylic acid unit (A1) include dicarboxylic acid units (A1-1) to (A1-9), but the dicarboxylic acid unit (A1) is not limited thereto.

[0064] [ka]

[0065] Specific examples of the dicarboxylic acid unit (A2) include dicarboxylic acid units (A2-1) to (A2-3), but the dicarboxylic acid unit (A2) is not limited thereto.

[0066] [ka]

[0067] Specific examples of the dicarboxylic acid unit (A3) include dicarboxylic acid units (A3-1) and (A3-2), but the dicarboxylic acid unit (A3) is not limited thereto.

[0068] [ka]

[0069] Specific examples of the dicarboxylic acid unit (A4) include dicarboxylic acid units (A4-1) to (A4-3), but the dicarboxylic acid unit (A4) is not limited thereto.

[0070] [ka]

[0071] 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), and even more preferably contains at least (A2-3).

[0072] The total mass proportion of the dicarboxylic acid units (A1) to (A4) in the polyester 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% by mass or more, the abrasion resistance of the photosensitive layer is good. From this viewpoint, the total mass proportion of the dicarboxylic acid units (A1) to (A4) is more preferably 20% by mass or more, and even more preferably 25% by 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 even more preferably 50 mass% or less. The dicarboxylic acid units (A1) to (A4) contained in the polyester resin (1) may be of one type or two or more types.

[0073] Examples of the dicarboxylic acid units (A) other than the dicarboxylic acid units (A1) to (A4) include aliphatic dicarboxylic acid units (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acid units (e.g., cyclohexanedicarboxylic acid), and lower alkyl ester units thereof (e.g., having 1 to 5 carbon atoms). The polyester resin (1) may contain one or more types of these dicarboxylic acid units.

[0074] The dicarboxylic acid unit (A) contained in the polyester resin (1) may be of one type or of two or more types.

[0075] The diol unit (B) is a structural unit represented by the following formula (B).

[0076] [ka]

[0077] In formula (B), Ar B1 and Ar B2 each independently represents an aromatic ring which may have a substituent, and L B is a single bond, an oxygen atom, a sulfur atom, or -C(Rb 1 )(Rb 2 )- and n B1 is 0, 1 or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may be bonded to form a cyclic alkyl group.

[0078] 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, with a benzene ring and a naphthalene ring being preferred.

[0079] Ar B1 The hydrogen atoms on the aromatic ring of Ar 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.

[0080] 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, with a benzene ring and a naphthalene ring being preferred.

[0081] Ar B2 The hydrogen atoms on the aromatic ring of Ar 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.

[0082] 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.

[0083] 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 in the aryl group is preferably 6 to 10, and more preferably 6.

[0084] 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.

[0085] 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).

[0086] It is more preferable that the diol unit (B) 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 (B4) represented by the formula (B4), a diol unit (B5) represented by the formula (B5), and a diol unit (B6) represented by the formula (B6): It is more preferable that the diol unit (B1) 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 (B5) represented by the following formula (B5), and a diol unit (B6) represented by the following formula (B6): It is even more preferable that the diol unit (B1) contains at least one selected from the group consisting of a diol unit (B2) represented by the following formula (B1), a diol unit (B2) represented by the following formula (B2), and a diol unit (B6) represented by the following formula (B6): It is most preferable that the diol unit (B1) 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).

[0087] [ka]

[0088] 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 , Rb801 and Rb 901 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0089] Rb 101 The branched alkyl group having 4 to 20 carbon atoms in Rb preferably has 4 to 16 carbon atoms, more preferably 4 to 12 carbon atoms, and even more preferably 4 to 8 carbon atoms. 101 Specific 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.

[0090] [ka]

[0091] 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0092] 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. 102Specific examples of the alkyl 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.

[0093] [ka]

[0094] 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0095] 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 from 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 from 1 to 4 carbon atoms is preferably from 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 213Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0096] [ka]

[0097] 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 , Rb 804 and Rb 904 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0098] Rb 104 The alkyl group having 1 to 3 carbon atoms in the formula (Rb) may be linear, branched, or cyclic. The alkyl group preferably has 1 or 2 carbon atoms, and more preferably has 1 carbon atom. 104 Specific examples of the group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

[0099] [ka]

[0100] In formula (B5), Ar 105 is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 205 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 405 , Rb 505 , Rb 805 and Rb 905 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0101] Ar 105The aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The number of carbon atoms in 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 105 The aryl group in the aralkyl group having 7 to 20 carbon atoms according to the above formula may be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and 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 anthracenylmethyl group, and a phenyl-cyclopentylmethyl group.

[0102] [ka]

[0103] 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0104] 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 216 The alkyl group in the alkoxy group having from 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 from 1 to 4 carbon atoms is preferably from 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.

[0105] [ka]

[0106] In formula (B7), Rb 407 , Rb 507 , Rb 807 and Rb 907 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0107] [ka]

[0108] In formula (B8), Rb 408 , Rb 508 , Rb 808 and Rb 908 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0109] Rb in formula (B1) 201 , Rb in formula (B2) 202 , Rb in formula (B4) 204 and Rb of formula (B5) 205Since the specific and preferred embodiments of Rb are the same as those of Rb, 201 , Rb 202 , Rb 204 and Rb 205 "Rb 200 " is collectively referred to as ".

[0110] Rb 200 The alkyl group having 1 to 3 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 or 2 carbon atoms, and more preferably 1 carbon atom. Examples of 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.

[0111] 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 embodiments of Rb are the same as those of Rb, 401 , Rb 402 , Rb 403 , Rb 404 , Rb 405 , Rb 406 , Rb 407 and Rb 408 "Rb 400 " is collectively referred to as ".

[0112] 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.

[0113] Rb 400 The alkyl group in the alkoxy group having from 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 from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 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 branched alkoxy groups 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.

[0114] Rb 400 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0115] 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 embodiments of Rb are the same as those of Rb, 501 , Rb 502 , Rb 503 , Rb 504 , Rb 505 , Rb 506 , Rb 507 and Rb508 "Rb 500 " is collectively referred to as ".

[0116] 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.

[0117] Rb 500 The alkyl group in the alkoxy group having from 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 from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 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 branched alkoxy groups 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.

[0118] Rb 500 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0119] 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 embodiments of Rb are the same as those of Rb, 801 , Rb 802 , Rb 803 , Rb 804 , Rb 805 , Rb 806 , Rb 807 and Rb 808 "Rb 800 " is collectively referred to as ".

[0120] 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.

[0121] Rb 800 The alkyl group in the alkoxy group having from 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 from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 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 branched alkoxy groups 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.

[0122] Rb 800 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0123] 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 embodiments of Rb are the same as those of Rb, 901 , Rb 902 , Rb 903 , Rb 904 , Rb 905 , Rb 906 , Rb 907 and Rb 908 "Rb 900 " is collectively referred to as ".

[0124] 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.

[0125] Rb 900 The alkyl group in the alkoxy group having from 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 from 1 to 6 carbon atoms is preferably from 1 to 4, more preferably from 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 branched alkoxy groups 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.

[0126] Rb 900 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0127] Specific examples of the diol unit (B1) include diol units (B1-1) to (B1-6), but the diol unit (B1) is not limited thereto.

[0128] [ka]

[0129] Specific examples of the diol unit (B2) include diol units (B2-1) to (B2-11), but the diol unit (B2) is not limited thereto.

[0130] [ka]

[0131] Specific examples of the diol unit (B3) include diol units (B3-1) to (B3-4), but the diol unit (B3) is not limited thereto.

[0132] [ka]

[0133] Specific examples of the diol unit (B4) include diol units (B4-1) to (B4-7), but the diol unit (B4) is not limited thereto.

[0134] [ka]

[0135] Specific examples of the diol unit (B5) include diol units (B5-1) to (B5-6), but the diol unit (B5) is not limited thereto.

[0136] [ka]

[0137] Specific examples of the diol unit (B6) include diol units (B6-1) to (B6-4), but the diol unit (B6) is not limited thereto.

[0138] [ka]

[0139] Specific examples of the diol unit (B7) include diol units (B7-1) to (B7-3), but the diol unit (B7) is not limited thereto.

[0140] [ka]

[0141] Specific examples of the diol unit (B8) include diol units (B8-1) to (B8-3), but the diol unit (B8) is not limited thereto.

[0142] [ka]

[0143] The diol unit (B) contained in the polyester resin (1) may be one type or two or more types.

[0144] The mass proportion of the diol units (B) in the polyester resin (1) is preferably 25 mass % or more and 80 mass % or less. When the mass proportion of the diol units (B) is 25 mass% or more, peeling of the photosensitive layer can be suppressed. From this viewpoint, the mass proportion of the diol units (B) is more preferably 30 mass% or more, and even more 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 even more preferably 70 mass% or less.

[0145] Examples of 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 polyester resin (1) may contain one or more types of these diol units.

[0146] The ends of the polyester resin (1) may be capped or modified with a terminal capping agent or a molecular weight modifier used during production. Examples of the terminal capping agent or molecular weight modifier include monohydric phenols, monohydric acid chlorides, monohydric alcohols, and monocarboxylic acids. Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m Examples include o-phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, and 2-phenyl-2-(3-hydroxyphenyl)propane. Examples of monovalent acid chlorides include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetic acid chloride, butyric acid chloride, octylic acid chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and substituted versions thereof. 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 monocarboxylic acid include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0147] When two or more polyester resins (1) having different weight-average molecular weights are mixed and the mixed polyester resin (1) is used to form a photosensitive layer, the weight-average molecular weight of each of the polyester resins (1) before mixing is preferably 30,000 or more and 300,000 or less, more preferably 40,000 or more and 250,000 or less, and even more preferably 50,000 or more and 200,000 or less. The molecular weight of the polyester resin (1) is a polystyrene-equivalent molecular weight measured by GPC (gel permeation chromatography), which uses tetrahydrofuran as an eluent.

[0148] The polyester resin (1) can be obtained by conventional polycondensation of a monomer that provides the dicarboxylic acid unit (A) and a monomer that provides the diol unit (B), optionally with other monomers. Examples of methods for polycondensation of monomers include interfacial polymerization, solution polymerization, and melt polymerization. Interfacial polymerization is a polymerization method for obtaining a polyester by mixing a dicarboxylic acid halide dissolved in a water-immiscible organic solvent with a dihydric alcohol dissolved in an alkaline aqueous solution. Literature related to interfacial polymerization includes WMA Reckson, J. Poly. Sci., XL399, 1959, and Japanese Patent Publication No. 1965-1959. Because interfacial polymerization has a faster reaction rate than solution polymerization, it can suppress hydrolysis of the dicarboxylic acid halide, resulting in the production of a high-molecular-weight polyester resin.

[0149] [Conductive substrate] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Other examples of conductive substrates include paper, resin films, 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 Ω·cm.

[0150] 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 inclusive in order to suppress interference fringes that occur when irradiated with laser light. When incoherent 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 by suppressing defects caused by surface irregularities.

[0151] Examples of methods for roughening the surface include wet honing, which involves spraying an abrasive suspended in water onto the conductive substrate; centerless grinding, which involves pressing the conductive substrate against a rotating grinding wheel and continuously grinding the substrate; and anodizing.

[0152] As a method for roughening the surface, there may be mentioned a method in which, without roughening the surface of the conductive substrate, 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.

[0153] Anodizing is a surface roughening treatment that uses a metallic (e.g., aluminum) conductive substrate as the anode and anodizes it in an electrolyte solution to form an oxide film on the surface of the conductive substrate. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active in its original state, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film, in which the micropores of the oxide film are sealed by volume expansion caused by hydration in pressurized steam or boiling water (with the addition of a metal salt such as nickel), converting the film into a more stable hydrated oxide.

[0154] The thickness of the anodic oxide film is preferably, for example, from 0.3 μm to 15 μm, inclusive, and within this range, the film tends to exhibit barrier properties against injection and also tends to suppress an increase in residual potential due to repeated use.

[0155] The conductive substrate may be subjected to a treatment with an acidic treatment solution or a boehmite treatment. Treatment with an acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The compounding ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution 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, with the total concentration of these acids 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.

[0156] The boehmite treatment is carried out, for example, by immersing the steel sheet in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting the steel sheet with heated steam at 90°C to 120°C for 5 to 60 minutes. The coating film preferably has a thickness of 0.1 μm to 5 μm. This may be further anodized using an electrolyte solution with low coating solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0157] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0158] For example, inorganic particles have a powder resistance (volume resistivity) of 1×10 2 Ω cm or more 1×10 11 Examples include inorganic particles with a particle size of Ω·cm or less. Among these, inorganic particles having the above resistance value are preferably metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0159] The specific surface area of ​​inorganic particles measured by the BET method is, for example, 10 m 2 / g or more is preferable. The volume average particle size of the inorganic particles is, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

[0160] The content of the inorganic particles is, for example, preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, relative to the binder resin.

[0161] The inorganic particles may be surface-treated, and two or more types of inorganic particles having different surface treatments or different particle sizes may be used in combination.

[0162] Examples of the surface treatment agent include a silane coupling agent, a titanate-based coupling agent, an aluminum-based 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.

[0163] 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.

[0164] Two or more silane coupling agents may be used in combination. 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.

[0165] 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.

[0166] 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 relative to the inorganic particles.

[0167] Here, it is preferable that the undercoat layer contains an electron-accepting compound (acceptor compound) together with the inorganic particles, from the viewpoint of improving the long-term stability of the electrical properties and the carrier blocking property.

[0168] 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, such as a hydroxyanthraquinone compound, an aminoanthraquinone compound, or an aminohydroxyanthraquinone compound, and specifically, for example, anthraquinone, alizarin, quinizarin, anthrarphine, or purpurin.

[0169] 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.

[0170] The electron-accepting compound can be attached to the surface of the inorganic particles by, for example, a dry method or a wet method.

[0171] The dry method is a method in which, while stirring inorganic particles using a mixer or the like with high shear force, an electron-accepting compound is added dropwise, either directly or dissolved in an organic solvent, or sprayed together with dry air or nitrogen gas to adhere the electron-accepting compound to the surface of the inorganic particles. The electron-accepting compound is preferably added dropwise or sprayed at a temperature below the boiling point of the solvent. After the electron-accepting compound has been added dropwise or sprayed, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as they achieve electrophotographic properties.

[0172] The wet method is a method in which inorganic particles are dispersed in a solvent using, for example, a stirrer, ultrasonic disperser, sand mill, attritor, or ball mill, while an electron-accepting compound is added, followed by stirring or dispersion, and then the solvent is removed to adhere the electron-accepting compound to the surfaces of the inorganic particles. The solvent can be removed, for example, by filtration or distillation. After solvent removal, 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. Examples of such methods include a method in which the inorganic particles are removed by stirring and heating in a solvent, and a method in which the inorganic particles are removed by azeotropy with the solvent.

[0173] The attachment of the electron-accepting compound may be carried out before or after the inorganic particles are surface-treated with a surface-treating agent, or the attachment of the electron-accepting compound and the surface treatment with a surface-treating agent may be carried out simultaneously.

[0174] The content of the electron-accepting compound is, for example, 0.01% by mass or more and 20% by mass or less, and preferably 0.01% by mass or more and 10% by mass or less, based on the inorganic particles.

[0175] Examples of binder resins used in the undercoat layer include known 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, 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, phenolic 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 binder resins used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline), and the like.

[0176] 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, phenolic resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins, and polyamide resins, polyester resins, polyether resins, methacrylic resins, acrylic resins, polyvinyl alcohol resins, and polyvinyl acetal 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.

[0177] The undercoat layer may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of additives include known materials such as polycyclic condensation and azo electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Silane coupling agents are used for the surface treatment of inorganic particles as described above, and may also be added to the undercoat layer as an additive.

[0178] 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, and 3-chloropropyltrimethoxysilane.

[0179] Examples of zirconium chelate compounds 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.

[0180] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-normal-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.

[0181] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0182] These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0183] 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 to suppress moire images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of 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 polishing methods include buffing, sandblasting, wet honing, and grinding.

[0184] 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 liquid for forming an undercoat layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0185] Examples of solvents 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.

[0186] Examples of a method for dispersing inorganic particles when preparing a coating liquid for forming an undercoat layer include known methods such as using a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0187] Examples of a method for applying the coating liquid for forming the undercoat layer onto the conductive substrate include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0188] The thickness of the undercoat layer is set, for example, preferably at least 15 μm, more preferably in the range of 20 μm to 50 μm.

[0189] [Middle layer] An intermediate layer may be further 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 (such as polyvinyl butyral), 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.

[0190] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0191] 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 liquid for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it if 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, air knife coating, and curtain coating.

[0192] The thickness of the intermediate layer is preferably set in the range of, for example, 0.1 μm to 3 μm, and the intermediate layer may also be used as an undercoat layer.

[0193] [Charge generation layer] The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Alternatively, the charge generation layer may be a vapor-deposited layer of the charge generation material. A vapor-deposited layer of the charge generation material is suitable for use with an incoherent light source such as an LED (Light Emitting Diode) or an organic EL (Electroluminescence) image array.

[0194] Examples of the charge generating material include azo pigments such as bisazo and trisazo; fused-ring aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0195] Among these, in order to be compatible with laser exposure in the near-infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material, specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, titanyl phthalocyanine, etc.

[0196] On the other hand, in order to accommodate laser exposure in the near ultraviolet region, preferred charge generating materials include fused ring aromatic pigments such as dibromoanthanthrone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and bisazo pigments.

[0197] The above charge generating material may also be used when an incoherent light source such as an LED or organic EL image array having a central emission wavelength of 450 nm or more and 780 nm or less is used.

[0198] In contrast, when n-type semiconductors such as fused-ring aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark current is less likely to occur, and image defects known as black spots can be suppressed even in thin films. The n-type is determined by the polarity of the photocurrent that flows using the commonly used time-of-flight method, and materials that more easily pass electrons as carriers than holes are considered n-type.

[0199] 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, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (e.g., polycondensation product of bisphenols and aromatic dicarboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinylpyrrolidone resin, etc. Here, "insulating" means a material having a volume resistivity of 1×1013 This means that the resistance is Ω·cm or more. These binder resins may be used alone or in combination of two or more.

[0200] The compounding ratio of the charge generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass.

[0201] The charge generating layer may contain other known additives.

[0202] The formation of the charge generation layer is not particularly limited, and a known formation method can be used. For example, the charge generation layer can be formed by forming a coating film of a coating liquid for forming the charge generation layer by adding the above components to a solvent, drying the coating film, and heating it as necessary. The charge generation layer can also be formed by vapor deposition of the charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when a fused ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0203] Examples of solvents 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.

[0204] Methods for dispersing particles (e.g., charge generating material) in the coating liquid for forming the charge generating layer include, for example, 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 passing through 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.

[0205] 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 blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0206] The thickness of the charge generating layer is set, for example, preferably in the range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0207] [Charge transport layer] The charge transport layer is a layer containing a charge transport material and a binder resin.

[0208] Examples of charge transport materials include electron transport 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 charge transport materials also include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination, but are not limited to these.

[0209] The charge transport material may be a polymer charge transport material, such as poly-N-vinylcarbazole, polysilane, or other known compounds having charge transport properties, and among these, polyester polymer charge transport materials are preferred.

[0210] Examples of the charge transport material or polymeric 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 Japanese Patent Application Laid-Open No. 2021-117377, paragraphs 0046 to 0048 of Japanese Patent Application Laid-Open No. 2019-035900, paragraphs 0052 to 0053 of Japanese Patent Application Laid-Open No. 2019-012141, paragraphs 0122 to 0134 of Japanese Patent Application Laid-Open No. 2021-071565, and paragraphs 0122 to 0134 of Japanese Patent Application Laid-Open No. 2021-015223 Examples of the compounds include those described in paragraphs 0101 to 0110 of JP 2013-097300 A, paragraph 0116, paragraphs 0309 to 0316 of WO 2019 / 070003 A, paragraphs 0103 to 0107 of JP 2018-159087 A, and paragraphs 0102 to 0113 of JP 2021-148818 A.

[0211] 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).

[0212] [ka]

[0213] 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 51 , R 52 , R 61 and R 62 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0214] The group in formula (C1) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0215] 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 the compound (C'1) represented by the following formula (C'1) is more preferred.

[0216] [ka]

[0217] 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.

[0218] [ka]

[0219] In formula (C2), R T201 , R T202 , R T211 and R T212 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, -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 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. Tm1, Tm2, ​​Tn1, and Tn2 are each independently 0, 1, or 2.

[0220] 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.

[0221] From the viewpoint of charge mobility, the compound (C2) is preferably an alkyl group, an aryl group, or -CH=CH-CH=C(R T24 )(R T25) is preferred, and the compound having at least one alkyl group, aryl group, or -CH=CH-CH=C(R T24 )(R T25 ) is more preferred.

[0222] [ka]

[0223] In formula (C3), R T301 , R T302 , R T311 and R T312 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, -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.

[0224] 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.

[0225] [ka]

[0226] In formula (C4), R T401 , R T402 , R T411 and R T412 are each independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, -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 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. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 are each independently 0, 1, or 2.

[0227] 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.

[0228] 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, more preferably 25% by mass or more and 65% by mass or less, and even more preferably 30% by mass or more and 60% by mass or less, based on the total mass of the charge transport layer.

[0229] The charge transport layer contains at least a polyester resin (1) as a binder resin. The proportion of the polyester resin (1) in the total amount of binder resins contained in the charge transport layer is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and particularly preferably 55% by mass or more. When the polyester resin (1) is used in combination with another resin, the other resin to be used in combination is preferably a polycarbonate resin.

[0230] The charge transport layer may contain a binder resin other than the polyester resin (1). Examples of the binder resin include polyester resins other than the polyester resin (1), polycarbonate 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 may be used alone or in combination of two or more.

[0231] The charge transport layer may contain other known additives, such as antioxidants, leveling agents, antifoaming agents, fillers, and viscosity modifiers.

[0232] 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 if necessary.

[0233] Examples of solvents for preparing the coating solution 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.

[0234] Examples of a coating method for applying the coating liquid for forming the charge transport layer onto the charge generating layer include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0235] The thickness of the charge transport layer is, for example, 5 μm or more and 50 μm or less. From the viewpoints of the photosensitivity and wear life of the photoreceptor, it is preferably 20 μm or more, more preferably 22 μm or more, and even more preferably 25 μm or more. From the viewpoint of the residual potential, it is preferably 50 μm or less, more preferably 47 μm or less, and even more preferably 45 μm or less.

[0236] [Single-layer photosensitive layer] The single-layer photosensitive layer (charge generation / charge transport layer) is a layer containing a charge generation material, a charge transport material, a binder resin, and, if necessary, other additives. These materials are the same as those described for the charge generation layer and the charge transport layer.

[0237] The single-layer photosensitive layer contains at least a polyester resin (1) as a binder resin. The proportion of the polyester resin (1) in the total amount of binder resins contained in the single-layer photosensitive layer is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and particularly preferably 55% by mass or more. When the polyester resin (1) is used in combination with another resin, the other resin to be used in combination is preferably a polycarbonate resin.

[0238] The content of the charge generating material in the single-layer photosensitive layer is preferably 0.1% by mass to 10% by mass, more preferably 0.8% by mass to 5% by mass, based on the total mass of the single-layer photosensitive layer.

[0239] The content of the charge transport material contained in the single-layer photosensitive layer is preferably 25% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 65% by mass or less, and even more preferably 40% by mass or more and 60% by mass or less, based on the total mass of the single-layer photosensitive layer.

[0240] The method for forming the single-layer photosensitive layer is the same as the method for forming the charge generating layer and the charge transport layer.

[0241] The film thickness of the single-layer photosensitive layer is, for example, 5 μm or more and 50 μm or less. From the viewpoints of the photosensitivity and wear life of the photoreceptor, it is preferably 10 μm or more, more preferably 12 μm or more, and even more preferably 15 μm or more. From the viewpoint of the residual potential, it is preferably 50 μm or less, more preferably 47 μm or less, even more preferably 45 μm or less, and even more preferably 40 μm or less.

[0242] [Protective layer] A protective layer may be provided on the photosensitive layer as needed, for example, to prevent chemical changes in the photosensitive layer when charged, or to further improve the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a layer made of a cured film (crosslinked film) as the protective layer. Examples of such a layer include the following layers 1) and 2).

[0243] 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 product of the reactive group-containing non-charge transport material).

[0244] 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, and R Q2 represents a hydrogen atom, an alkyl group or a trialkylsilyl group, and Qn represents an integer of 1 to 3.

[0245] 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 groups 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 these, 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 is preferred as the chain polymerizable group because of its excellent reactivity.

[0246] The charge transport skeleton of the reactive group-containing charge transport material is not particularly limited as long as it has a known structure in electrophotographic photoreceptors, and examples thereof include a skeleton derived from a nitrogen-containing hole transport compound such as a triarylamine compound, a benzidine compound, or a hydrazone compound, and having a conjugated structure with a nitrogen atom. Among these, a triarylamine skeleton is preferred.

[0247] 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.

[0248] The protective layer may also contain other known additives.

[0249] 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 liquid for forming the 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.

[0250] Examples of solvents for preparing the coating liquid for forming the 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. The coating liquid for forming the protective layer may be a solvent-free coating liquid.

[0251] 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, air knife coating, and curtain coating.

[0252] The thickness of the protective layer is set, for example, preferably in the range of 1 μm or more and 20 μm or less, more preferably 2 μm or more and 10 μm or less.

[0253] <Image forming apparatus, process cartridge> The image forming apparatus according to the present embodiment includes an electrophotographic photosensitive member, a charging device that charges the surface of the electrophotographic photosensitive member, an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member 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 photosensitive member according to the present embodiment is used as the electrophotographic photosensitive member.

[0254] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as an apparatus equipped with 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 equipped with a cleaning device that cleans the surface of an electrophotographic photosensitive member after transfer of a toner image but before charging; an apparatus equipped with a static elimination device that irradiates the surface of an electrophotographic photosensitive member with static elimination light to eliminate static electricity after transfer of a toner image but before charging; and an apparatus equipped with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

[0255] 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 that performs primary transfer of the toner image formed on the surface of the electrophotographic photosensitive body onto the surface of the intermediate transfer body, and a secondary transfer device that performs secondarily transfer of the toner image transferred onto the surface of the intermediate transfer body onto the surface of the recording medium.

[0256] The image forming apparatus according to this 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).

[0257] 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. In addition to the electrophotographic photosensitive member, the process cartridge may include, for example, 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.

[0258] 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. The main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0259] FIG. 3 is a schematic diagram showing an example of the configuration of an image forming apparatus according to this embodiment. As shown in FIG. 3 , the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 having an electrophotographic photosensitive member 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 member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photosensitive member 7 through the opening of the process cartridge 300, and the transfer device 40 is disposed at a position facing the electrophotographic photosensitive member 7 via the intermediate transfer member 50, with a portion of the intermediate transfer member 50 being in contact with the electrophotographic photosensitive member 7. Although not shown, the image forming apparatus 100 also includes a secondary transfer device that transfers the toner image transferred onto the intermediate transfer member 50 onto a recording medium (e.g., paper). The intermediate transfer member 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown) correspond to examples of transfer devices.

[0260] 3 integrally supports an electrophotographic photosensitive member 7, a charging device 8 (an example of a charging device), a developing device 11 (an example of a developing device), and a cleaning device 13 (an example of a cleaning device) within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is disposed so as to come into contact with the surface of the electrophotographic photosensitive member 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.

[0261] FIG. 3 shows an example of an image forming apparatus equipped with a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists cleaning, which may be arranged as needed.

[0262] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0263] -Charging device- The charging device 8 may be, for example, a contact-type charger using a conductive or semi-conductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. Also usable are non-contact type roller chargers, scorotron chargers and corotron chargers that utilize corona discharge, and other known chargers.

[0264] -Exposure equipment- The exposure device 9 may be, for example, an optical system that exposes the surface of the electrophotographic photosensitive member 7 to 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 photosensitive member. The wavelength of semiconductor lasers is mainly near-infrared, with an oscillation wavelength around 780 nm. However, this wavelength is not limited to this, and lasers with an oscillation wavelength in the 600 nm range or blue lasers with an oscillation wavelength of 400 nm to 450 nm may also be used. Furthermore, for color image formation, a surface-emitting laser light source capable of outputting multiple beams is also effective.

[0265] -Developing device- The developing device 11 may be, for example, a general developing device that develops by contact or non-contact application of a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected depending on the purpose. For example, it may be a known developing device that has a function of applying a one-component developer or a two-component developer to the electrophotographic photosensitive member 7 using a brush, roller, or the like. Among these, a developing roller that holds a developer on its surface is preferred.

[0266] The developer used in the developing device 11 may be a one-component developer containing only toner, or a two-component developer containing toner and a carrier. The developer may be magnetic or non-magnetic. Known developers are used.

[0267] -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 cleaning type may also be used.

[0268] -Transfer device- Examples of the transfer device 40 include a contact type transfer charger using a belt, roller, film, rubber blade, etc., and a known transfer charger such as a scorotron transfer charger or corotron transfer charger that utilizes corona discharge.

[0269] -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.

[0270] FIG. 4 is a schematic diagram showing another example of the configuration of the image forming apparatus according to the present embodiment. The image forming apparatus 120 shown in Fig. 4 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer member 50, and one electrophotographic photosensitive member is used per color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem-type apparatus. [Example]

[0271] 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 any way. In the following description, unless otherwise specified, "parts" and "%" are by mass. In the following description, syntheses, treatments, manufacturing, etc. were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0272] <Preparation of Polyester Resin> For each of the Examples and Comparative Examples shown in Tables 1 and 2, at least two polyester resins having the same type of structural unit but different weight-average molecular weights were synthesized and mixed to prepare the polyester resin of each example. In synthesizing all of the polyester resins, polymerization was carried out in the presence of an end-capping agent, 2,3,5-trimethylphenol, to cap the resin ends. In Comparative Examples S1 and T1, one type of monodisperse polyester resin was used. Tables 1 and 2 show the units that make up the polyester resin. A2-3 and the like shown in Tables 1 and 2 are specific examples of the dicarboxylic acid unit (A) already described. B1-4 and the like shown in Tables 1 and 2 are specific examples of the diol unit (B) already described.

[0273] In Example S13, two types of dicarboxylic acid units (A) were used in the synthesis of the polyester resin, and the molar ratio of the two types of dicarboxylic acid units (A) was (A1-1):(A1-7)=1:1. In Example S22, two types of diol acid units (B) were used in the synthesis of the polyester resin, and the molar ratio of the two types of diol units (B) was (B1-2):(B7-2)=2:3. In Example S23, two types of dicarboxylic acid units (A) were used in the synthesis of the polyester resin, and the molar ratio of the two types of dicarboxylic acid units (A) was (A3-2):(A4-3)=4:1.

[0274] <Production of a photoreceptor having a laminated photosensitive layer> [Example S1] - Formation of undercoat layer - As a conductive substrate, an aluminum cylindrical tube having an outer diameter of 30 mm, a length of 365 mm, and a wall thickness of 1.6 mm was prepared.

[0275] Zinc oxide (average particle size 70 nm, specific surface area 15 m 2100 parts of a silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed with 500 parts of toluene by stirring, and 1.3 parts of a silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) was added 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.

[0276] 110 parts of the surface-treated zinc oxide was mixed with 500 parts of tetrahydrofuran and stirred, and a solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added, followed by stirring for 5 hours at 50° C. The solid content was then filtered off under reduced pressure and dried under reduced pressure at 60° C. to obtain zinc oxide with alizarin added thereto.

[0277] A solution of 60 parts alizarin-modified zinc oxide, 13.5 parts blocked isocyanate (product name: Sumidur 3175, Sumitomo Bayer Urethane Co., Ltd.), and 15 parts butyral resin (product name: S-LEC BM-1, Sekisui Chemical Co., Ltd.) dissolved in 68 parts methyl ethyl ketone was mixed with 5 parts methyl ethyl ketone and dispersed in a sand mill using 1 mm diameter glass beads for 2 hours to obtain a dispersion. To the dispersion, 0.005 parts dioctyltin dilaurate as a catalyst and 4 parts silicone resin particles (product name: Tospearl 145, Momentive Performance Materials Japan, LLC) were added to obtain a coating solution for forming an undercoat layer. The coating solution for forming the undercoat layer was applied to the outer surface of a conductive substrate by dip coating and dried and cured at 185°C for 35 minutes to form an undercoat layer with an average thickness of 25 μm.

[0278] - Formation of charge generation layer - A mixture consisting of 15 parts of hydroxygallium phthalocyanine (CGL) as a charge-generating material (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), 10 parts of vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using 1 mm diameter glass beads 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. The coating solution for forming the charge-generating layer was dip-coated onto the undercoat layer and dried at room temperature (25°C±3°C) to form a charge-generating layer with an average thickness of 0.25 μm.

[0279] - Formation of charge transport layer - Binder resin: 60 parts polyester resin ·Charge transport material: CTM-1 40 parts 270 parts tetrahydrofuran 30 parts toluene The structural units, weight average molecular weight and molecular weight distribution of the polyester resin used in this example are as shown in Table 1. The above materials were mixed by stirring to obtain a coating solution for forming a charge transport layer. The coating solution for forming a charge transport layer was dip-coated onto the charge generation layer and dried at 145°C for 30 minutes to form a charge transport layer with an average thickness of 40 μm.

[0280] [Examples S2 to S24 and Comparative Examples S1 to S5] Each photoreceptor was prepared in the same manner as in Example S1, except that the type of binder resin in the charge transport layer was changed as shown in Table 1.

[0281] [Example S25] A photoreceptor was prepared in the same manner as in Example S1, except that the binder resin in the charge transport layer was changed to 30 parts polyester resin and 30 parts polycarbonate resin. The structural units, weight average molecular weight, and molecular weight distribution of the polyester resin used in this example are as shown in Table 1. The polycarbonate resin used in this example is a polycarbonate resin consisting of the following repeating units, and is referred to as polycarbonate resin (PC-1).

[0282] [ka]

[0283] [Examples S26 to S29] Each photoreceptor was fabricated in the same manner as in Example S1, except that the type of binder resin in the charge transport layer and the type of charge transport material were changed as shown in Table 1. In Example 28, 20 parts of CTM-1 and 20 parts of CTM-3 were used.

[0284] The chemical structures of the charge transport materials CTM-1 to CTM-4 are shown below.

[0285] [ka]

[0286] <Production of a photoreceptor having a single-layer photosensitive layer> [Example T1] - Formation of undercoat layer - As a conductive substrate, an aluminum cylindrical tube having an outer diameter of 30 mm, a length of 365 mm, and a wall thickness of 1.6 mm was prepared.

[0287] Zinc oxide (average particle size 70 nm, specific surface area 15 m 2 100 parts of a silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed with 500 parts of toluene by stirring, and 1.3 parts of a silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) was added 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.

[0288] 110 parts of the surface-treated zinc oxide was mixed with 500 parts of tetrahydrofuran and stirred, and a solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added, followed by stirring for 5 hours at 50° C. The solid content was then filtered off under reduced pressure and dried under reduced pressure at 60° C. to obtain zinc oxide with alizarin added thereto.

[0289] A solution of 60 parts alizarin-modified zinc oxide, 13.5 parts blocked isocyanate (product name: Sumidur 3175, Sumitomo Bayer Urethane Co., Ltd.), and 15 parts butyral resin (product name: S-LEC BM-1, Sekisui Chemical Co., Ltd.) dissolved in 68 parts methyl ethyl ketone was mixed with 5 parts methyl ethyl ketone and dispersed in a sand mill using 1 mm diameter glass beads for 2 hours to obtain a dispersion. To the dispersion, 0.005 parts dioctyltin dilaurate as a catalyst and 4 parts silicone resin particles (product name: Tospearl 145, Momentive Performance Materials Japan, LLC) were added to obtain a coating solution for forming an undercoat layer. The coating solution for forming the undercoat layer was applied to the outer surface of a conductive substrate by dip coating and dried and cured at 185°C for 35 minutes to form an undercoat layer with an average thickness of 25 μm.

[0290] - Formation of a single-layer photosensitive layer - Binder resin: Polyester resin 52.75 parts Charge generating material: V-type hydroxygallium phthalocyanine 1.25 parts (The Bragg angle (2θ±0.2°) of the X-ray diffraction spectrum using CuKα characteristic X-rays has diffraction peaks at at least 7.3°, 16.0°, 24.9°, and 28.0°.) ·Charge transport material: ETM-1 7.8 parts ·Charge transport material: CTM-1 38.2 parts (The mass ratio of ETM-1 to CTM-1 is 17:83) 175 parts tetrahydrofuran 75 parts toluene The structural units, weight average molecular weight and molecular weight distribution of the polyester resin used in this example are as shown in Table 2. The above materials were mixed and dispersed in a sand mill using 1 mm diameter glass beads for 4 hours to obtain a coating solution for forming a photosensitive layer. The coating solution for forming a photosensitive layer was dip-coated onto the undercoat layer and dried and cured at 110°C for 40 minutes to form a single-layer photosensitive layer with an average thickness of 34 μm.

[0291] [ka]

[0292] [Examples T2 to T11, T13, and T14 and Comparative Examples T1 to T5] Each photoreceptor was produced in the same manner as in Example T1, except that the type of binder resin in the single-layer photosensitive layer was changed to the type shown in Table 2.

[0293] [Example T12] A photoreceptor was prepared in the same manner as in Example T1, except that the binder resin in the single-layer photosensitive layer was changed to 26.75 parts polyester resin and 26 parts polycarbonate resin. The structural units, weight-average molecular weight, and molecular weight distribution of the polyester resin used in this example are as shown in Table 2. The polycarbonate resin used in this example was polycarbonate resin (PC-1).

[0294] <Photoreceptor performance evaluation> [Potential distribution] The photoreceptor of each example or comparative example was mounted on an image forming apparatus Apeos C7070 (FUJIFILM Business Innovation Co., Ltd.). To measure the surface potential of the photoreceptor, a probe connected to a surface potential meter (Trek 334, Trek Japan Co., Ltd.) was placed at the axial center of the photoreceptor, 1 mm away from the surface. The charging and exposure conditions were adjusted so that the surface potential after charging was −650 V and the surface potential after exposure was −300 V in an environment of 20°C temperature and 40% relative humidity. The probes connected to the surface potential meter were placed at 11 locations: the center of the photoreceptor in the axial direction, and at positions 2 cm, 4 cm, 6 cm, 8 cm, and 10 cm from the center of the axial direction toward both ends. The surface potential of the photoreceptor was measured at these 11 locations, and the difference between the maximum and minimum values ​​was calculated and classified as follows:

[0295] A+: Difference is 5V or less A: Difference is greater than 5V and less than 10V B: Difference is over 10V and 20V or less C: Difference is over 20V

[0296] [Image quality after the fall] -Normal environment- The following operations were carried out in an environment with a temperature of 20°C and a relative humidity of 40%. The photosensitive member of each example or comparative example was combined with other necessary components to form a process cartridge 300 as shown in Figure 3. To record the contact position between the photosensitive member and the cleaning blade, marks were made with oil-based ink at both ends of the axial direction of the photosensitive member at the contact position. When an image is formed, the areas on the photosensitive member surface marked with oil-based ink have a different amount of toner attached than areas not marked with oil-based ink, making it possible to identify the contact position. The process cartridge was then dropped from a height of 30 cm onto a horizontal concrete platform with the axial direction of the photoreceptor aligned horizontally. This free drop was repeated four times, rotating the photoreceptor 90° in the circumferential direction (i.e., shifting the contact point with the cleaning blade 90° in the circumferential direction). Next, the process cartridge was mounted in an image forming apparatus Apeos C7070, and 10 black images with an image density (area coverage) of 30% were continuously output onto A3-sized plain paper. The 10 images were visually inspected. The color density difference and the presence or absence of image defects were visually inspected at the position corresponding to the contact point between the photosensitive member and the cleaning blade when the process cartridge was allowed to fall freely, compared with other positions. The color density difference and the presence or absence of image defects were classified as follows:

[0297] A+: No image defects or color density differences are observed. A: No image defects are observed. Slight differences in color density are observed, but they disappear within 10 sheets. B: Minor image defects are seen in places along the axial direction. C: A clear image defect is observed across the axial direction.

[0298] -High temperature and humidity- The photosensitive member of each example or comparative example was combined with other necessary components to form the process cartridge 300 shown in Figure 3, which was then marked with oil-based ink in the same manner as above and placed in an environment at a temperature of 40°C and a relative humidity of 85% for three days. Next, a free fall test similar to that described above was carried out in an environment of a temperature of 40°C and a relative humidity of 85%. Next, the process cartridge was placed in an environment at a temperature of 20° C. and a relative humidity of 40% for 10 hours, and then an image formation test similar to that described above was carried out in an environment at a temperature of 20° C. and a relative humidity of 40%.

[0299] [Storage stability] -Normal environment- The following operations were carried out in an environment with a temperature of 20°C and a relative humidity of 40%. The photoreceptor of each example or comparative example was combined with other necessary components to form a process cartridge 300 as shown in Figure 3. A 1 cm square urethane sponge (Scotch-Brite from 3M Japan Ltd., molded into a 1 cm cube) was sandwiched between the cleaning blade contact area at the axial center of the photoreceptor, and the cleaning blade contact area at both ends of the photoreceptor in the axial direction was marked with oil-based ink to record the position. When an image is formed, the areas marked with oil-based ink on the photoreceptor surface have a different amount of toner attached than areas not marked with oil-based ink, making the position identifiable. Next, with the urethane sponge still sandwiched between the cartridges, the process cartridges were placed in an environment at a temperature of 20° C. and a relative humidity of 40% for 3 days. Next, the urethane sponge was removed from the process cartridge, and the process cartridge was mounted in an image forming apparatus Apeos C7070, and 10 black images with an image density (area coverage) of 30% were continuously printed on A3-sized plain paper. Ten images were visually inspected. The areas that had been in contact with the urethane sponge during the three-day storage period were compared with other areas to visually inspect for differences in color density and the presence or absence of image defects. The presence or absence of color density differences and image defects was classified as follows:

[0300] A+: No image defects or color density differences are observed. A: No image defects are observed. Slight differences in color density are observed, but they disappear within 10 sheets. B: Minor image defects are seen in places along the axial direction. C: A clear image defect is observed across the axial direction.

[0301] -High temperature and humidity- The photosensitive member of each example or comparative example was combined with other necessary components to form the process cartridge 300 shown in Figure 3, and a urethane sponge was placed between the cartridges as described above, and the cartridge was placed in an environment with a temperature of 40°C and a relative humidity of 85% for three days. Next, the urethane sponge was removed from the process cartridge, and the process cartridge was placed in an environment of 20°C and 40% relative humidity for 10 hours, after which an image formation test similar to that described above was carried out in an environment of 20°C and 40% relative humidity.

[0302] [Table 1]

[0303] [Table 2]

[0304] The electrophotographic photoreceptor, process cartridge, and image forming apparatus of the present disclosure include the following aspects: Each formula is the same as the formula with the same number described above.

[0305] (((1))) a conductive substrate; and a laminated photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate; the charge transport layer contains a charge transport material and a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B), The molecular weight distribution curve of the polyester resin (1) contained in the charge transport layer has at least two peaks, and when the molecular weight at the maximum point of the peak with the smallest molecular weight is defined as Mmin, the molecular weight at the maximum point of the peak with the largest molecular weight is defined as Mmax, and the weight average molecular weight of the polyester resin (1) contained in the charge transport layer is defined as Mw, the ranges of 50,000≦Mw≦200,000 and 0.4≦(Mmax−Mmin) / Mw≦5.0 are satisfied. Electrophotographic photoreceptor. (((2))) The electrophotographic photoreceptor according to (((1))), which satisfies 0.5≦(Mmax−Mmin) / Mw≦4.5. (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), which satisfies 80,000≦Mw≦150,000. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the dicarboxylic acid unit (A) comprises 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). (((5))) The electrophotographic photoreceptor according to (((4))), wherein the dicarboxylic acid unit (A) comprises at least one selected from the group consisting of the dicarboxylic acid unit (A2), the dicarboxylic acid unit (A3), and the dicarboxylic acid unit (A4). (((6))) The electrophotographic photoreceptor according to any one of (((1))) to (((5))), wherein the diol unit (B) 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). (((7))) The electrophotographic photoreceptor according to (((6))), wherein the diol unit (B) includes at least one selected from the group consisting of the diol unit (B1), the diol unit (B2), the diol unit (B5), and the diol unit (B6). (((8))) A conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate, the single-layer photosensitive layer contains a charge transport material and a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B), the molecular weight distribution curve of the polyester resin (1) contained in the single-layer photosensitive layer has at least two peaks, the molecular weight at the maximum point of the peak with the smallest molecular weight is defined as Mmin, the molecular weight at the maximum point of the peak with the largest molecular weight is defined as Mmax, and the weight average molecular weight of the polyester resin (1) contained in the single-layer photosensitive layer is defined as Mw, and the ranges of 50,000≦Mw≦200,000 and 0.4≦(Mmax−Mmin) / Mw≦5.0 are satisfied; Electrophotographic photoreceptor. (((9))) The electrophotographic photoreceptor according to (((8))), which satisfies 0.5≦(Mmax−Mmin) / Mw≦4.5. (((10))) The electrophotographic photoreceptor according to (((8))) or (((9))), which satisfies 80,000≦Mw≦150,000. (((11))) The electrophotographic photoreceptor according to any one of (((8))) to (((10))), wherein the dicarboxylic acid unit (A) comprises 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). (((12))) The electrophotographic photoreceptor according to (((11))), wherein the dicarboxylic acid unit (A) comprises at least one selected from the group consisting of the dicarboxylic acid unit (A2), the dicarboxylic acid unit (A3), and the dicarboxylic acid unit (A4). (((13))) The electrophotographic photoreceptor according to any one of (((8))) to (((12))), wherein the diol unit (B) 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). (((14))) The electrophotographic photoreceptor according to (((13))), wherein the diol unit (B) comprises at least one selected from the group consisting of the diol unit (B1), the diol unit (B2), the diol unit (B5), and the diol unit (B6). (((15))) An electrophotographic photoreceptor according to any one of (((1))) to (((14))), Attaching to and detaching from the image forming device Process cartridge. (((16))) an electrophotographic photoreceptor according to any one of (((1))) to (((14))); a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; Image forming device.

[0306] According to (((1))), (((4))), (((5))), (((6))) or (((7))), there is provided an electrophotographic photoreceptor having a laminated photosensitive layer, which has excellent uniformity of surface potential distribution and is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time, compared to an electrophotographic photoreceptor in which the polyester resin (1) contained in the charge transport layer has an Mw of less than 50,000 or more than 200,000, or (Mmax-Mmin) / Mw of less than 0.4 or more than 5.0. According to (((2))), an electrophotographic photoreceptor is provided which is provided with a laminated photosensitive layer, and which has excellent uniformity of surface potential distribution, is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time, compared to an electrophotographic photoreceptor in which the (Mmax-Mmin) / Mw of the polyester resin (1) contained in the charge transport layer is less than 0.5 or more than 4.5. According to (((3))), an electrophotographic photoreceptor is provided which is provided with a laminated photosensitive layer, and which has excellent uniformity of surface potential distribution compared to an electrophotographic photoreceptor in which the polyester resin (1) contained in the charge transport layer has an Mw of less than 80,000 or more than 150,000, and which is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and which is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time. According to (((8))), (((11))), (((12))), (((13))) or (((14))), there is provided an electrophotographic photoreceptor having a single-layer type photosensitive layer, which has excellent uniformity of surface potential distribution and is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time, compared to an electrophotographic photoreceptor in which the Mw of the polyester resin (1) contained in the single-layer type photosensitive layer is less than 50,000 or more than 200,000, or (Mmax-Mmin) / Mw is less than 0.4 or more than 5.0. According to (((9))), an electrophotographic photoreceptor is provided which is provided with a single-layer photosensitive layer, and which has excellent uniformity of surface potential distribution, is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time, compared to an electrophotographic photoreceptor in which the (Mmax-Mmin) / Mw of the polyester resin (1) contained in the single-layer photosensitive layer is less than 0.5 or more than 4.5. According to (((10))), an electrophotographic photoreceptor is provided which is provided with a single-layer photosensitive layer, and which has excellent uniformity of surface potential distribution compared to an electrophotographic photoreceptor in which the Mw of the polyester resin (1) contained in the single-layer photosensitive layer is less than 80,000 or more than 150,000, and which is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and which is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time. According to the invention (((15))), there is provided a process cartridge equipped with an electrophotographic photosensitive member which has excellent uniformity in the surface potential distribution, is less likely to cause image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to cause image defects even when left in a high-temperature, high-humidity environment for a long period of time. According to the invention (((16))), an image forming apparatus is provided that includes an electrophotographic photoreceptor that has excellent uniformity in the potential distribution on its surface, is less likely to produce image defects even when dropped in a high-temperature, high-humidity environment, and is less likely to produce image defects even when left in a high-temperature, high-humidity environment for a long period of time. [Explanation of symbols]

[0307] 1 Conductive substrate, 2 Undercoat layer, 3 Charge generation layer, 4 Charge transport layer, 5 Photosensitive layer, 10A photoreceptor, 10B photoreceptor

[0308] 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 laminated photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate; the charge transport layer contains a charge transport material and a polyester 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), the molecular weight distribution curve of the polyester resin (1) contained in the charge transport layer has at least two peaks, the molecular weight at the maximum point of the peak with the smallest molecular weight is defined as Mmin, the molecular weight at the maximum point of the peak with the largest molecular weight is defined as Mmax, and the weight average molecular weight of the polyester resin (1) contained in the charge transport layer is defined as Mw, and the relationships of 50,000≦Mw≦200,000 and 0.4≦(Mmax−Mmin) / Mw≦5.0 are satisfied; Electrophotographic photoreceptor. 【Chemical 1】 In formula (A), Ar Ａ１ and Ar Ａ２ each independently represents an aromatic ring which may have a substituent, and 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, and L Ｂ is a single bond, an oxygen atom, a sulfur atom, or -C(Rb １ )(Rb ２ )- and n Ｂ１ is 0, 1 or 2. １ and Rb ２ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb １ and Rb ２ may be bonded to form a cyclic alkyl group.

2. 2. The electrophotographic photoreceptor according to claim 1, wherein 0.5≦(Mmax−Mmin) / Mw≦4.5 is satisfied.

3. 2. The electrophotographic photoreceptor according to claim 1, wherein Mw satisfies 80,000≦Mw≦150,000.

4. 2. The electrophotographic photoreceptor according to claim 1, wherein the dicarboxylic acid unit (A) comprises 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 are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A2), n ２０１ and n ２０２ are each independently an integer of 0 to 4, ２０１ Ra ２０１ and n ２０２ Ra ２０２ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A3), n ３０１ and n ３０２ are each independently an integer of 0 to 4, ３０１ Ra ３０１ and n ３０２ Ra ３０２ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A4), n ４０１ is an integer of 0 to 6, ４０１ Ra ４０１ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

5. 5. The electrophotographic photoreceptor according to claim 4, wherein the dicarboxylic acid unit (A) comprises at least one selected from the group consisting of the dicarboxylic acid unit (A2), the dicarboxylic acid unit (A3), and the dicarboxylic acid unit (A4).

6. 2. The electrophotographic photoreceptor according to claim 1, wherein the diol unit (B) comprises 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). 【Chemistry 3】 【Chemistry 4】 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. 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 , Rb ８０４ and Rb ９０４ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B5), Ar １０５ is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb ２０５ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０５ , Rb ５０５ , Rb ８０５ and Rb ９０５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B7), Rb ４０７ , Rb ５０７ , Rb ８０７ and Rb ９０７ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B8), Rb ４０８ , Rb ５０８ , Rb ８０８ and Rb ９０８ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

7. 7. The electrophotographic photoreceptor according to claim 6, wherein the diol unit (B) comprises at least one selected from the group consisting of the diol unit (B1), the diol unit (B2), the diol unit (B5), and the diol unit (B6).

8. A conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate, the single-layer photosensitive layer contains a charge transport material and a polyester 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), the molecular weight distribution curve of the polyester resin (1) contained in the single-layer photosensitive layer has at least two peaks, the molecular weight at the maximum point of the peak with the smallest molecular weight is defined as Mmin, the molecular weight at the maximum point of the peak with the largest molecular weight is defined as Mmax, and the weight average molecular weight of the polyester resin (1) contained in the single-layer photosensitive layer is defined as Mw, and the relationships 50,000≦Mw≦200,000 and 0.4≦(Mmax−Mmin) / Mw≦5.0 are satisfied; Electrophotographic photoreceptor. 【Chemistry 5】 In formula (A), Ar Ａ１ and Ar Ａ２ each independently represents an aromatic ring which may have a substituent, and 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, and L Ｂ is a single bond, an oxygen atom, a sulfur atom, or -C(Rb １ )(Rb ２ )- and n Ｂ１ is 0, 1 or 2. １ and Rb ２ are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb １ and Rb ２ may be bonded to form a cyclic alkyl group.

9. 9. The electrophotographic photoreceptor according to claim 8, which satisfies 0.5≦(Mmax−Mmin) / Mw≦4.

5.

10. The electrophotographic photoreceptor according to claim 8 , wherein Mw satisfies 80,000≦Mw≦150,000.

11. 9. The electrophotographic photoreceptor according to claim 8, wherein the dicarboxylic acid unit (A) comprises 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 6】 In formula (A1), n １０１ is an integer of 0 to 4, １０１ Ra １０１ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A2), n ２０１ and n ２０２ are each independently an integer of 0 to 4, ２０１ Ra ２０１ and n ２０２ Ra ２０２ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A3), n ３０１ and n ３０２ are each independently an integer of 0 to 4, ３０１ Ra ３０１ and n ３０２ Ra ３０２ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A4), n ４０１ is an integer of 0 to 6, ４０１ Ra ４０１ are each independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

12. 12. The electrophotographic photoreceptor according to claim 11, wherein the dicarboxylic acid unit (A) comprises at least one selected from the group consisting of the dicarboxylic acid unit (A2), the dicarboxylic acid unit (A3), and the dicarboxylic acid unit (A4).

13. 9. The electrophotographic photoreceptor according to claim 8, wherein the diol unit (B) comprises 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). 【Chemistry 7】 【Chemistry 8】 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. 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 , Rb ８０４ and Rb ９０４ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B5), Ar １０５ is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb ２０５ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb ４０５ , Rb ５０５ , Rb ８０５ and Rb ９０５ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. 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 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B7), Rb ４０７ , Rb ５０７ , Rb ８０７ and Rb ９０７ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B8), Rb ４０８ , Rb ５０８ , Rb ８０８ and Rb ９０８ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

14. 14. The electrophotographic photoreceptor according to claim 13, wherein the diol unit (B) comprises at least one selected from the group consisting of the diol unit (B1), the diol unit (B2), the diol unit (B5), and the diol unit (B6).

15. An electrophotographic photoreceptor according to any one of claims 1 to 14, Attaching to and detaching from the image forming device Process cartridge.

16. The electrophotographic photoreceptor according to any one of claims 1 to 14, a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing 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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