Positive charge type electrophotographic photoreceptor, process cartridge and image formation device

Abstract

To provide a positive charge type electrophotographic photoreceptor excellent in controllability in color point generation caused by corrosion and wear resistance.SOLUTION: A positive charge type electrophotographic photoreceptor includes a monolayer type photosensitive layer including a hole transport material, an electron transport material, a charge generating material and a binder resin. The binder resin includes a resin A having an elastic deformation rate of 53.0% or more and a resin B in which a difference between the elastic deformation rates of the resin A and the resin B is 12% or more and 17% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a positively charged electrophotographic photoreceptor comprising a conductive support and a single-layer photosensitive layer provided on the conductive support, the single-layer photosensitive layer containing a charge generating material, a hole transport material, an electron transport material, and a binder resin, wherein the charge generating material contains at least titanyl phthalocyanine, and the contact angle between the surface of the outermost layer and water is in the range of 81° to 87°.

[0003] Patent Document 2 discloses a single-layer electrophotographic photoreceptor for use in an image forming apparatus equipped with a roller cleaning system, which comprises a substrate having no anodized oxide film and a photosensitive layer containing at least a charge generating material, a hole transport agent, an electron transport agent, and a binder resin, the binder resin being a polycarbonate resin having a viscosity average molecular weight in the range of 10,000 to 40,000, the photosensitive layer having a thickness in the range of 20 to 45 μm, and the absolute value of the positive and negative withstand voltages of the single-layer electrophotographic photoreceptor measured in accordance with JIS C 2110 being 6 kV or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 154740 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-237555 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide a positively charged electrophotographic photoreceptor that is superior in suppression of the occurrence of color spots caused by corrosion and in abrasion resistance compared to a case where the binder resin in the single-layer photosensitive layer contains resin A having an elastic deformation rate of 53.0% or more and resin B having an elastic deformation rate difference from resin A of less than 12% or more than 17%. [Means for solving the problem]

[0006] Means for solving the above problems include the following aspects. <1> A positively charged electrophotographic photoreceptor has a single-layer photosensitive layer containing a hole transport material, an electron transport material, a charge generating material, and a binder resin, wherein the binder resin contains a resin A having an elastic deformation rate of 53.0% or more and a resin B having an elastic deformation rate difference from that of the resin A of 12% or more and 17% or less. <2> The mass ratio MA / MB of the content MA of the resin A to the content MB of the resin B is 0.25 or more and 4 or less. <1> 1. The positively charged electrophotographic photoreceptor according to claim 1. <3> The mass ratio MA / MB of the content MA of the resin A to the content MB of the resin B is 0.4 or more and 2.5 or less. <2> 1. The positively charged electrophotographic photoreceptor according to claim 1. <4> The difference in elastic deformation rate between the resin B and the resin A is 13% or more and 16% or less. <1> ~ <3> 10. The positively charged electrophotographic photoreceptor according to claim 9, wherein the positively charged electrophotographic photoreceptor is a photoreceptor having a thickness of 100 nm or less. <5> The elastic deformation rate of the resin B is smaller than the elastic deformation rate of the resin A by 12% or more and 17% or less. <1> ~ <4> 10. The positively charged electrophotographic photoreceptor according to claim 9, wherein the positively charged electrophotographic photoreceptor is a photoreceptor having a thickness of 100 nm or less. <6> The resin A is a polyarylate resin. <1> ~ <5> 10. The positively charged electrophotographic photoreceptor according to claim 9, wherein the positively charged electrophotographic photoreceptor is a photoreceptor having a thickness of 100 nm or less. <7> The resin B is a polycarbonate resin. <1> ~ <6> 10. The positively charged electrophotographic photoreceptor according to claim 9, wherein the positively charged electrophotographic photoreceptor is a photoreceptor having a thickness of 100 nm or less. <8> The resin A has a biphenyl structure. <1> ~ <7> 10. The positively charged electrophotographic photoreceptor according to claim 9, wherein the positively charged electrophotographic photoreceptor is a photoreceptor having a thickness of 100 nm or less. <9> The resin B has a biphenyl structure. <1> ~ <8> 10. The positively charged electrophotographic photoreceptor according to claim 9, wherein the positively charged electrophotographic photoreceptor is a photoreceptor having a thickness of 100 nm or less. <10> <1> ~ <9> 10. A process cartridge comprising the positively charged electrophotographic photosensitive member according to any one of claims 1 to 9, which is detachably mountable to an image forming apparatus. <11> <1> ~ <9> an electrostatic latent image forming device that forms 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; and a transfer device that transfers the toner image to the surface of a recording medium, wherein the charging device is a positive charging type charging device. [Effects of the Invention]

[0007] <1> According to the invention, a positively charged electrophotographic photoreceptor is provided which is superior in suppression of the occurrence of color spots caused by corrosion and in abrasion resistance, compared to when the binder resin in the single-layer photosensitive layer contains resin A having an elastic deformation rate of 53.0% or more and resin B having an elastic deformation rate difference from resin A of less than 12% or more than 17%. <2> According to the invention, a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion compared to when the mass ratio MA / MB of the content MA of the resin A to the content MB of the resin B is less than 0.25 or more than 4. <3> According to the invention, a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion compared to when the mass ratio MA / MB of the content MA of the resin A to the content MB of the resin B is less than 0.4 or exceeds 2.5. <4> According to the invention, a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion compared to when the difference in elastic deformation rate between the resin B and the resin A is less than 13% or more than 16%. <5> According to the invention, a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion compared to when the elastic deformation rate of the resin B is 12% or more and 17% or less higher than the elastic deformation rate of the resin A. <6> According to the present invention, a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion and in abrasion resistance compared to when the resin A is a polyester resin other than a polyarylate resin. <7> According to the invention, there is provided a positively charged electrophotographic photoreceptor which is superior in abrasion resistance and suppresses the occurrence of color spots caused by corrosion, compared to when the resin B is a polyester resin. <8> According to the invention, there is provided a positively charged electrophotographic photoreceptor in which the resin A has superior abrasion resistance and superior suppression of the occurrence of color spots caused by corrosion, compared to when the resin A does not have a biphenyl structure. <9> According to the invention, there is provided a positively charged electrophotographic photoreceptor in which the resin B has superior abrasion resistance and superior suppression of the occurrence of color spots caused by corrosion, compared to when the resin B does not have a biphenyl structure. <10> or <11> According to the invention, a process cartridge or an image forming apparatus is provided which is superior in the ability to suppress the occurrence of color spots caused by corrosion in a positively charged electrophotographic photosensitive member and in the abrasion resistance, compared to when the binder resin in the single-layer photosensitive layer of the positively charged electrophotographic photosensitive member contains resin A having an elastic deformation rate of 53.0% or more and resin B having an elastic deformation rate difference from resin A of less than 12% or more than 17%. [Brief explanation of the drawings]

[0008] [Figure 1] 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 2] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 3] 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

[0009] Hereinafter, an embodiment of the present invention will be described in detail. In this specification, 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 present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples. In this specification, 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. When embodiments are described in this specification 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. In this specification, each component may contain multiple types of corresponding substances. When referring to the amount of each component in the composition in this embodiment, if multiple types of substances corresponding to each component are present in the composition, the total amount of the multiple types of substances present in the composition is used unless otherwise specified. In this specification, the particles corresponding to each component may include multiple types. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified. In this specification, alkyl groups and alkylene groups include any of straight-chain, branched and cyclic groups, unless otherwise specified. In this specification, a hydrogen atom in an organic group, aromatic ring, linking group, alkyl group, alkylene group, aryl group, aralkyl group, alkoxy group, aryloxy group, etc. may be substituted with a halogen atom. When compounds are represented by structural formulas in this specification, the symbols (C and H) representing carbon atoms and hydrogen atoms in the hydrocarbon group and / or hydrocarbon chain may be omitted. In this specification, the term "structural unit" of a copolymer or resin has the same meaning as a monomer unit. In this specification, ppm is an abbreviation for parts per million, and is based on mass.

[0010] <Positively charged electrophotographic photoreceptor> The positively charged electrophotographic photoreceptor according to this embodiment has a single-layer photosensitive layer containing a hole transport material, an electron transport material, a charge generation material, and a binder resin, and the binder resin contains a resin A having an elastic deformation rate of 53.0% or more and a resin B having an elastic deformation rate difference from that of the resin A of 12% to 17%.

[0011] The positively charged electrophotographic photoreceptor according to this embodiment preferably includes a conductive substrate and a single-layer photosensitive layer disposed on the conductive substrate. The positively charged electrophotographic photoreceptor according to this embodiment may further include other layers (for example, an undercoat layer, an intermediate layer).

[0012] FIG. 1 is a partial cross-sectional view schematically illustrating an example of the layer structure of a positively charged electrophotographic photoreceptor according to this embodiment. Photoreceptor 10B shown in FIG. 1 has a single-layer photosensitive layer. 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. 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.

[0013] In principle, the electrical characteristics of conventional single-layer electrophotographic photoreceptors are determined by the electron mobility rate, and therefore, a positive charging method capable of shortening the electron transport distance is generally adopted. However, in a positive charging type image forming apparatus, when the apparatus is operated for a long period of time under high temperature and high humidity, leakage current occurs at the electrical singular points of the photosensitive layer, causing the photosensitive layer to corrode and develop into color spots. In the positively charged electrophotographic photosensitive member according to the present embodiment, the binder resin of the single-layer photosensitive layer contains resin A having an elastic deformation rate of 53.0% or more and resin B having an elastic deformation rate difference of 12% to 17% from resin A. As the binder resin contains resin A having an elastic deformation rate of 53.0% or more and high durability, and resin B having an elastic deformation rate difference of 12% to 17% from resin A, physical irregularities occur on the surface of the single-layer photosensitive layer during actual running due to the difference in durability between resin A and resin B. It is estimated that the current flowing through the recesses formed on the surface of the single-layer photosensitive layer inhibits corrosion of the single-layer photosensitive layer, providing excellent suppression of color spots caused by corrosion.It is also estimated that the inclusion of Resin A, which has high durability with an elastic deformation rate of 53.0% or more, provides excellent abrasion resistance.

[0014] In the following description, the positively charged electrophotographic photosensitive member may be simply referred to as the "electrophotographic photosensitive member."

[0015] (single-layer photosensitive layer) The positively charged electrophotographic photoreceptor according to this embodiment has a single-layer photosensitive layer containing a hole transport material, an electron transport material, a charge generating material, and a binder resin.

[0016] [Binder resin] In the positively charged electrophotographic photoreceptor according to this embodiment, the binder resin in the single-layer photosensitive layer contains a resin A having an elastic deformation rate of 53.0% or more and a resin B having an elastic deformation rate difference from that of the resin A of 12% or more and 17% or less. From the viewpoint of suppressing the occurrence of color spots due to corrosion (hereinafter also simply referred to as "suppression of color spots"), it is preferable that resin A and resin B are not compatible with each other. In the single-layer photosensitive layer, from the viewpoint of suppressing the occurrence of color spots, it is preferable that Resin A and Resin B form an interpenetrating polymer network structure or a sea-island structure depending on the mixing ratio thereof, and it is more preferable that they form an interpenetrating polymer network structure.

[0017] -Elastic deformation rate of resin A- The elastic deformation rate of resin A is 53.0% or more, and from the viewpoints of abrasion resistance and suppression of color spot occurrence, it is preferably 53.0% or more and 75.0% or less, more preferably 54.0% or more and 70.0% or less, and particularly preferably 56.0% or more and 65.0% or less.

[0018] -Elastic deformation rate of resin B- From the viewpoints of abrasion resistance and suppression of color spot occurrence, the elastic deformation rate of Resin B is preferably 36.0% or more and less than 53.0%, more preferably 40.0% or more and 50.0% or less, and particularly preferably 42.0% or more and 48.0% or less.

[0019] -Difference in elastic deformation rate between resin B and resin A- The difference in elastic deformation rate between resin B and resin A is 12% or more and 17% or less, and from the viewpoint of suppressing the occurrence of color spots, it is preferably 12% or more and 16% or less, more preferably 12% or more and 15% or less, and particularly preferably 12.5% or more and 14.5% or less. Moreover, from the viewpoint of suppressing the occurrence of color spots, the elastic deformation rate of resin B is preferably smaller than the elastic deformation rate of resin A by 12% or more and 17% or less.

[0020] In this embodiment, the elastic deformation rate of the resin is measured as follows. The elastic deformation rate of the resin is determined as follows. The elastic deformation rate is defined as the total deformation rate when a load is applied to the photosensitive layer, divided into elastic deformation and plastic deformation, and is calculated as elastic deformation rate / total deformation rate. Specifically, it is calculated by measuring the indentation depth and the indentation depth-stress curve using an MTS Nanoindenter SA2, a DCM head, and a diamond equilateral triangular pyramidal indenter. Specifically, the measurement conditions are a temperature of 24°C, a humidity of 50%, and an indentation depth of 500 nm. The indentation depth Dmax (nm) is the indentation depth when the photosensitive layer is completely unloaded. The elastic deformation rate R is calculated using the following formula: [Formula] Elastic deformation rate = (Dmax - D1) / Dmax

[0021] -The mass ratio (MA / MB) of resin A to resin B- From the viewpoint of suppressing the occurrence of color spots, the mass ratio MA / MB of the content MA of resin A to the content MB of resin B in the single-layer photosensitive layer is preferably 0.1 or more and 10 or less, more preferably 0.25 or more and 4 or less, even more preferably 0.4 or more and 2.5 or less, and particularly preferably 0.5 or more and 2.0 or less. Furthermore, from the viewpoint of abrasion resistance, the mass ratio MA / MB of the content MA of resin A to the content MB of resin B in the single-layer photosensitive layer is preferably 0.4 or more and 10 or less, more preferably 0.5 or more and 10 or less, and particularly preferably 0.75 or more and 9 or less.

[0022] Examples of binder resins used in the single-layer photosensitive layer include polycarbonate resins, polyester 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, and polysilanes.

[0023] From the viewpoints of abrasion resistance and suppression of color dot formation, the resin A is preferably a polyester resin or a polycarbonate resin, and more preferably a polyester resin. Furthermore, from the viewpoints of abrasion resistance and suppression of color dot generation, it is particularly preferable that the resin A is a polyarylate resin among polyester resins. Examples of polyarylate resins include polycondensates of bisphenols and aromatic dicarboxylic acids. Furthermore, from the viewpoints of abrasion resistance and suppression of color dot formation, it is preferable that Resin A has a biphenyl structure.

[0024] The weight average molecular weight (Mw) of the resin A is preferably from 30,000 to 300,000, more preferably from 40,000 to 250,000, and even more preferably from 50,000 to 200,000. The weight-average molecular weight of the resin is the weight-average molecular weight in terms of polystyrene measured by GPC (gel permeation chromatography), which uses tetrahydrofuran as the eluent.

[0025] Resin B is preferably a polyester resin or a polycarbonate resin, more preferably a polycarbonate resin, from the viewpoints of abrasion resistance and suppression of color dot formation. Furthermore, from the viewpoints of abrasion resistance and suppression of color dot formation, it is preferable that Resin B has a biphenyl structure.

[0026] From the viewpoint of suppressing color spot generation, the viscosity average molecular weight of Resin B is preferably 50,000 or less, more preferably 45,000 or less, and even more preferably 40,000 or less. From the viewpoint of abrasion resistance, the viscosity average molecular weight of Resin B is preferably 20,000 or more.

[0027] In the present embodiment, the viscosity average molecular weight of the resin is measured by the following single-point measurement method. First, the single-layer photosensitive layer to be measured is exposed from the photoreceptor, and a portion of the single-layer photosensitive layer is cut out to prepare a measurement sample. Next, extract the resin from the measurement sample. 1 g of the extracted resin is dissolved in 100 cm of methylene chloride. 3 The specific viscosity ηsp is measured using an Ubbelohde viscometer at a temperature of 25°C. Then, ηsp / c = [η] + 0.45 [η] 2 c relation (where c is the concentration (g / cm 3 ) from the intrinsic viscosity [η] (cm 3 / g) and calculate the value of [η] = 1.23 × 10 -4 Mv 0.83 The viscosity average molecular weight Mv is calculated from the following equation.

[0028] -Polyarylate resin- As the polyarylate resin, the following are preferably used.

[0029] The polyarylate resin preferably has at least dicarboxylic acid units (A) represented by formula (A) and diol units (B) represented by formula (B). The polyarylate resin may contain dicarboxylic acid units other than the dicarboxylic acid units (A). The polyarylate resin may contain diol units other than the diol units (B).

[0030] The dicarboxylic acid unit (A) is a structural unit represented by the following formula (A).

[0031] [ka]

[0032] In formula (A), n 1 is 1, 2 or 3, and n 1 m 1 are each independently 0, 1, 2, 3 or 4, and m 1 Ra 1 are each independently an alkyl group having 1 to 10 carbon atoms (also referred to as "number of carbon atoms"), an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0033] In formula (A), n 1 is 1, 2 or 3, with 2 being preferred. n 1 When is 2, the two benzene rings in formula (A) are separated by m 1 and Ra 1 may be the same benzene ring or different benzene rings. n 1 When is 3, the three benzene rings in formula (A) are separated by m 1 and Ra 1 may be the same benzene ring or different benzene rings.

[0034] In formula (A), n 1When is 2 or 3, the linking position between the benzene rings may be any of ortho, meta and para, and meta or para is preferred.

[0035] In formula (A), m 1 is 0, 1, 2, 3 or 4, preferably 0, 1 or 2, more preferably 0 or 1, and even more preferably 0. m 1 When is 2, two Ra bonds to the same benzene ring 1 may be the same type of group or different types of groups. m 1 When is 3, three Ra bonds to the same benzene ring 1 may be the same type of group or different types of groups. m 1 When is 4, four Ra bonds to the same benzene ring 1 may be the same type of group or different types of groups.

[0036] In formula (A), 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. In formula (A), the aryl group having 6 to 12 carbon atoms may be either monocyclic or polycyclic. The aryl group preferably has 6 to 10 carbon atoms, more preferably 6 to 9 carbon atoms. In formula (A), 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.

[0037] In formula (A), 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.

[0038] In the formula (A), 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.

[0039] In the formula (A), 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. In formula (A), examples of the branched alkoxy group having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. In the formula (A), 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.

[0040] In formula (A), m 1 When is 1, 2, 3 or 4, Ra 1is preferably a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 3 to 6 carbon atoms, more preferably a linear alkyl group having 1 to 4 carbon atoms or a branched alkyl group having 3 or 4 carbon atoms, and more preferably a methyl group or an ethyl group.

[0041] Specific examples of the dicarboxylic acid unit (A) include dicarboxylic acid units (A-1) to (A-13), but the dicarboxylic acid unit (A) is not limited thereto.

[0042] [ka]

[0043] [ka]

[0044] As the dicarboxylic acid unit (A), the above specific examples (A-1), (A-7), and (A-10) to (A-13) are preferred, (A-10) to (A-12) are more preferred, and (A-12) is particularly preferred.

[0045] The dicarboxylic acid unit (A) contained in the polyarylate resin may be of one type or two or more types.

[0046] The diol unit (B) is a structural unit represented by the following formula (B).

[0047] [ka]

[0048] In formula (B), 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 3 , Rb 4 , Rb 5 , Rb6 , Rb 7 , Rb 8 , Rb 9 and Rb 10 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms; Rb 1 and Rb 2 may be bonded to form a cyclic alkyl group.

[0049] In formula (B), 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 15 carbon atoms, more preferably 1 to 12 carbon atoms, and even more preferably 1 to 10 carbon atoms. In formula (B), 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 to 9. In formula (B), Rb 1 and Rb 2 The aryl group in the aralkyl group having from 7 to 20 carbon atoms may be either monocyclic or polycyclic, and the alkyl group in the aralkyl group having from 7 to 20 carbon atoms may be either linear, branched, or cyclic. The number of carbon atoms in the aryl group is preferably from 6 to 10, and more preferably from 6 to 9. The number of carbon atoms in the alkyl group is preferably from 1 to 6, more preferably from 1 to 5, and even more preferably from 1 to 4. In formula (B), Rb 1 and Rb 2 The number of carbon atoms in the cyclic alkyl group that may be formed by bonding with is preferably 5 or more and 15 or less, and more preferably 6 or more and 12 or less.

[0050] In formula (B), Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7, Rb 8 , Rb 9 and Rb 10 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. In formula (B), Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7 , Rb 8 , Rb 9 and Rb 10 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 to 9. In formula (B), Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7 , Rb 8 , Rb 9 and Rb 10 The aryl group in the aralkyl group having from 7 to 20 carbon atoms may be either monocyclic or polycyclic, and the alkyl group in the aralkyl group having from 7 to 20 carbon atoms may be either linear, branched, or cyclic. The number of carbon atoms in the aryl group is preferably from 6 to 10, and more preferably from 6 to 9. The number of carbon atoms in the alkyl group is preferably from 1 to 6, more preferably from 1 to 5, and even more preferably from 1 to 4. In formula (B), Rb 3 , Rb 4 , Rb 5 , Rb 6 , Rb 7 , Rb 8 , Rb 9 and Rb 10 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.

[0051] In formula (B), examples of the linear alkyl group having 1 to 20 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, 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. Examples of branched alkyl groups having 3 to 20 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, a tert-decyl group, an isododecyl group, a sec-dodecyl group, a tert-dodecyl group, a tert-tetradecyl group, and a tert-pentadecyl group. Examples of the cyclic alkyl group having 3 to 20 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 the like, as well as polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl groups formed by linking these monocyclic alkyl groups.

[0052] In the formula (B), 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.

[0053] In formula (B), 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.

[0054] In the formula (B), 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. In formula (B), examples of the branched alkoxy group having 3 to 6 carbon atoms include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, and a tert-hexyloxy group. In the formula (B), 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.

[0055] In formula (B), Rb 1 and Rb 2 are each independently a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms, or Rb 1 and Rb 2 and preferably bond to form a cyclic alkyl group having 5 to 12 carbon atoms. In formula (B), Rb 1 and Rb 2 are each independently a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, or a branched alkyl group having 1 to 10 carbon atoms, or Rb 1 and Rb 2 and more preferably bond to form a cyclic alkyl group having 5 to 12 carbon atoms. In formula (B), Rb 1 and Rb 2 It is more preferable that each of the is independently a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, or a branched alkyl group having 1 to 10 carbon atoms.

[0056] In formula (B), Rb 1 and Rb 2at least one of Rb is a linear alkyl group having 4 to 10 carbon atoms, a branched alkyl group having 4 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms, 1 and Rb 2 and preferably bond to form a cyclic alkyl group having 5 to 12 carbon atoms. In formula (B), Rb 1 and Rb 2 It is more preferable that at least one of them is a linear alkyl group having 4 to 10 carbon atoms or a branched alkyl group having 4 to 10 carbon atoms. Rb 1 and Rb 2 When at least one of the above is 1 and Rb 2 The other is preferably a hydrogen atom or a linear alkyl group having 1 to 3 carbon atoms.

[0057] The diol unit (B) is preferably a constituent unit represented by the following formula (B').

[0058] [ka]

[0059] Rb in formula (B') 1 , Rb 2 , Rb 4 and Rb 9 are Rb in formula (B), respectively. 1 , Rb 2 , Rb 4 and Rb 9 The same definition and preferred form are also the same.

[0060] The diol unit (B) is, in the formula (B'), Rb 1 is a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, or a branched alkyl group having 3 carbon atoms, and Rb 2is a linear alkyl group having from 4 to 10 carbon atoms, a branched alkyl group having from 4 to 10 carbon atoms, an aryl group having from 6 to 10 carbon atoms, or an aralkyl group having from 7 to 10 carbon atoms, and Rb 4 and Rb 9 are each independently a hydrogen atom or a methyl group; Rb 1 is a hydrogen atom or a methyl group, and Rb 2 is a linear alkyl group having 4 to 10 carbon atoms or a branched alkyl group having 4 to 10 carbon atoms, and Rb 4 and Rb 9 are each independently a hydrogen atom or a methyl group.

[0061] Specific examples of the diol unit (B) include diol units (B-1) to (B-38), but the diol unit (B) is not limited thereto.

[0062] [ka]

[0063] [ka]

[0064] [ka]

[0065] [ka]

[0066] [ka]

[0067] Among these, (B-19) is preferred as the diol unit (B).

[0068] The diol unit (B) contained in the polyarylate resin may be of one type or two or more types.

[0069] The mass proportion of the dicarboxylic acid unit (A) in the polyarylate resin is preferably 15 mass % or more and 60 mass % or less. When the mass proportion of the dicarboxylic acid units (A) is 15 mass% or more, the photosensitive layer has good abrasion resistance. From this viewpoint, the mass proportion of the dicarboxylic acid units (A) is more preferably 20 mass% or more, and even more preferably 25 mass% or more. When the mass proportion of the dicarboxylic acid unit (A) is 60 mass% or less, peeling of the photosensitive layer is further suppressed. From this viewpoint, the mass proportion of the dicarboxylic acid unit (A) is more preferably 55 mass% or less, and even more preferably 50 mass% or less.

[0070] The mass proportion of the diol units (B) in the polyarylate resin is preferably 25 mass % or more and 60 mass % or less. When the mass proportion of the diol units (B) is 25 mass% or more, peeling of the photosensitive layer is further 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 60 mass% or less, the solubility in the coating solution for forming the photosensitive layer is maintained and the abrasion resistance is improved. From this viewpoint, the mass proportion of the diol unit (B) is more preferably 55 mass% or less, and even more preferably 50 mass% or less.

[0071] The polyarylate resin may contain dicarboxylic acid units other than the dicarboxylic acid units (A).

[0072] Examples of the other dicarboxylic acid units include dicarboxylic acid units (C) represented by the following formula (C).

[0073] [ka]

[0074] In formula (C), Rc 1 , Rc 2 , Rc 3 , Rc 4 , Rc 5 and Rc 6 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 alkoxy group having 1 to 6 carbon atoms.

[0075] In formula (C), 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. In formula (C), the aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The aryl group preferably has 6 to 10 carbon atoms, more preferably 6 to 9 carbon atoms. In formula (C), 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.

[0076] Examples of the alkyl group, aryl group and alkoxy group in formula (C) include the same groups as those listed for formula (A).

[0077] In formula (C), Rc 1 , Rc 2 , Rc 3 , Rc 4 , Rc 5 and Rc 6 are each independently preferably a hydrogen atom, a linear alkyl group having from 1 to 6 carbon atoms, or a branched alkyl group having from 1 to 6 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having from 1 to 4 carbon atoms, or a branched alkyl group having from 1 to 4 carbon atoms, still more preferably a hydrogen atom, a linear alkyl group having from 1 to 3 carbon atoms, or a branched alkyl group having from 1 to 3 carbon atoms, and particularly preferably a hydrogen atom.

[0078] As the dicarboxylic acid unit (C), a 2,6-naphthalenedicarboxylic acid unit (the following unit (C-1)) is particularly preferred.

[0079] [ka]

[0080] The dicarboxylic acid unit (C) contained in the polyarylate resin may be of one type or two or more types.

[0081] When the polyarylate resin has dicarboxylic acid units (C), the mass proportion of the dicarboxylic acid units (C) in the polyarylate resin is preferably 1 mass % or more and 20 mass % or less.

[0082] Examples of the other dicarboxylic acid units include dicarboxylic acid units (D) represented by the following formula (D).

[0083] [ka]

[0084] In formula (D), Rd 1 , Rd 2 , Rd 3 , Rd 4 , Rd 5 , Rd 6 , Rd 7 and Rd 8 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 alkoxy group having 1 to 6 carbon atoms.

[0085] In formula (D), 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. In formula (D), the aryl group having 6 to 12 carbon atoms may be either monocyclic or polycyclic. The aryl group preferably has 6 to 10 carbon atoms, more preferably 6 to 9 carbon atoms. In formula (D), 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.

[0086] Examples of the alkyl group, aryl group and alkoxy group in formula (D) include the same groups as those listed for formula (A).

[0087] In formula (D), Rd 1 , Rd 2 , Rd 3 , Rd 4 , Rd 5 , Rd 6 , Rd 7 and Rd 8 are each independently preferably a hydrogen atom, a linear alkyl group having from 1 to 6 carbon atoms, or a branched alkyl group having from 1 to 6 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having from 1 to 4 carbon atoms, or a branched alkyl group having from 1 to 4 carbon atoms, still more preferably a hydrogen atom, a linear alkyl group having from 1 to 3 carbon atoms, or a branched alkyl group having from 1 to 3 carbon atoms, and particularly preferably a hydrogen atom.

[0088] The dicarboxylic acid unit (D) is preferably a structural unit represented by the following formula (D').

[0089] [ka]

[0090] Rd in formula (D') 1 , Rd 2 , Rd 3 and Rd 4 are Rd in formula (D), respectively. 1 , Rd2 , Rd 3 and Rd 4 The same definition and preferred form are also the same.

[0091] As the dicarboxylic acid unit (D), a diphenyl ether-4,4'-dicarboxylic acid unit (the following unit (D-1)) is particularly preferred.

[0092] [ka]

[0093] The dicarboxylic acid unit (D) contained in the polyarylate resin may be of one type or two or more types.

[0094] When the polyarylate resin has dicarboxylic acid units (D), the mass proportion of the dicarboxylic acid units (D) in the polyarylate resin is preferably 1 mass % or more and 20 mass % or less.

[0095] Examples of other dicarboxylic acid units include aliphatic dicarboxylic acid units (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, 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 polyarylate resin may contain one or more types of these dicarboxylic acid units.

[0096] The polyarylate resin may contain diol units other than the diol units (B).

[0097] Examples of the other diol units include diol units (E) represented by the following formula (E).

[0098] [ka]

[0099] In formula (E), Re 1 ,Re 2 ,Re 3 ,Re 4 ,Re 5 ,Re 6 ,Re 7 and Re 8 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0100] In formula (E), 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. In formula (E), the aryl group having 6 to 12 carbon atoms may be either a monocyclic or polycyclic ring. The aryl group preferably has 6 to 10 carbon atoms, more preferably 6 to 9 carbon atoms. In formula (E), the aryl group in the aralkyl group having from 7 to 20 carbon atoms may be either monocyclic or polycyclic, and the alkyl group in the aralkyl group having from 7 to 20 carbon atoms may be either linear, branched, or cyclic. The number of carbon atoms in the aryl group is preferably from 6 to 10, and more preferably from 6 to 9. The number of carbon atoms in the alkyl group is preferably from 1 to 6, more preferably from 1 to 5, and even more preferably from 1 to 4. In formula (E), 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.

[0101] Examples of the alkyl group, aryl group, aralkyl group and alkoxy group in formula (E) include the same groups as those listed for formula (B).

[0102] In formula (E), Re 1 ,Re 2 ,Re 3,Re 4 ,Re 5 ,Re 6 ,Re 7 and Re 8 are each independently preferably a hydrogen atom, a linear alkyl group having from 1 to 6 carbon atoms, or a branched alkyl group having from 1 to 6 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having from 1 to 4 carbon atoms, or a branched alkyl group having from 1 to 4 carbon atoms, still more preferably a hydrogen atom, a linear alkyl group having from 1 to 3 carbon atoms, or a branched alkyl group having from 1 to 3 carbon atoms, and particularly preferably a hydrogen atom or a methyl group.

[0103] The diol unit (E) is preferably a structural unit represented by the following formula (E').

[0104] [ka]

[0105] Re in formula (E') 1 ,Re 2 ,Re 3 and Re 4 are the Re in Eq. (E), respectively. 1 ,Re 2 ,Re 3 and Re 4 The same definition and preferred form are also the same.

[0106] As the diol unit (E), any one of the following units (E-1), (E-2) and (E-3) is particularly preferred.

[0107] [ka]

[0108] The diol unit (E) contained in the polyarylate resin may be of one type or two or more types.

[0109] When the polyarylate resin has diol units (E), the mass proportion of the diol units (E) in the polyarylate resin is preferably 1 mass % or more and 20 mass % or less.

[0110] Examples of the other diol units include diol units (F) represented by the following formula (F).

[0111] [ka]

[0112] In formula (F), Rf 1 , Rf 2 , Rf 3 , Rf 4 , Rf 5 , Rf 6 , Rf 7 and Rf 8 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0113] In formula (F), 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. In formula (F), the aryl group having 6 to 12 carbon atoms may be either monocyclic or polycyclic. The aryl group preferably has 6 to 10 carbon atoms, more preferably 6 to 9 carbon atoms. In formula (F), the aryl group in the aralkyl group having from 7 to 20 carbon atoms may be either monocyclic or polycyclic, and the alkyl group in the aralkyl group having from 7 to 20 carbon atoms may be either linear, branched, or cyclic. The number of carbon atoms in the aryl group is preferably from 6 to 10, and more preferably from 6 to 9. The number of carbon atoms in the alkyl group is preferably from 1 to 6, more preferably from 1 to 5, and even more preferably from 1 to 4. In formula (F), 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.

[0114] Examples of the alkyl group, aryl group, aralkyl group and alkoxy group in formula (F) include the same groups as those listed for formula (B).

[0115] In formula (F), Rf 1 , Rf 2 , Rf 3 , Rf 4 , Rf 5 , Rf 6 , Rf 7 and Rf 8 are each independently preferably a hydrogen atom, a linear alkyl group having from 1 to 6 carbon atoms, or a branched alkyl group having from 1 to 6 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having from 1 to 4 carbon atoms, or a branched alkyl group having from 1 to 4 carbon atoms, still more preferably a hydrogen atom, a linear alkyl group having from 1 to 3 carbon atoms, or a branched alkyl group having from 1 to 3 carbon atoms, and particularly preferably a hydrogen atom or a methyl group.

[0116] The diol unit (F) is preferably a structural unit represented by the following formula (F').

[0117] [ka]

[0118] Rf in formula (F') 1 , Rf 2 , Rf 3 and Rf 4 are Rf in formula (F), respectively. 1 , Rf 2 , Rf 3 and Rf 4 The same definition and preferred form are also the same.

[0119] As the diol unit (F), a bis(4-hydroxyphenyl) ether unit (the following unit (F-1)) is particularly preferred.

[0120] [ka]

[0121] The diol unit (F) contained in the polyarylate resin may be of one type or two or more types.

[0122] When the polyarylate resin has diol units (F), the mass proportion of the diol units (F) in the polyarylate resin is preferably 1 mass % or more and 20 mass % or less.

[0123] Examples of other diol units include aliphatic diol units (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, and neopentyl glycol) and alicyclic diol units (e.g., cyclohexanediol, cyclohexanedimethanol, and hydrogenated bisphenol A). The polyarylate resin may contain one or more types of these diol units.

[0124] Polyester resins, including polyarylate resins, are obtained by conventional polycondensation of a monomer that provides a dicarboxylic acid unit, a monomer that provides a diol unit, and, if necessary, 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 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 a high molecular weight polyester resin.

[0125] The terminals of the polyester resin including the polyarylate resin may be blocked or modified with a terminal blocking agent or a molecular weight modifier used during production. Examples of the terminal blocking agent or the molecular weight modifier include a monohydric phenol, a monovalent acid chloride, a monohydric alcohol, and a monovalent carboxylic acid. Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m-phenylphenol, p-phenylphenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, and 2-phenyl-2-(3-hydroxyphenyl)propane. Examples of the monovalent acid chloride include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetic acid chloride, butyric acid chloride, octylic acid chloride, benzoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and substituted versions 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.

[0126] -Polycarbonate resin- As the polycarbonate resin, known polycarbonate resins can be used, and a suitable example is a polycarbonate resin containing a structural unit having at least one of a biphenyl skeleton and a bisphenol skeleton (hereinafter also referred to as "BP polycarbonate resin"). Examples of BP polycarbonate resins include homopolymers composed of structural units having a biphenyl skeleton, homopolymers composed of structural units having a bisphenol skeleton, and copolymers composed of at least one of structural units having a biphenyl skeleton and structural units having a bisphenol skeleton. Among these, homopolymers composed of structural units having a biphenyl skeleton are preferred from the viewpoint of abrasion resistance. Examples of the bisphenol skeleton include a bisphenol A skeleton, a bisphenol B skeleton, a bisphenol BP skeleton, a bisphenol C skeleton, a bisphenol F skeleton, and a bisphenol Z skeleton.

[0127] Specific examples of BP polycarbonate resins include homopolymers of dihydroxybiphenyl compounds, homopolymers of dihydroxybisphenol compounds, and copolymers thereof. These polymers can be obtained, for example, by using the above compounds as raw materials and subjecting them to polycondensation with a carbonate-forming compound such as phosgene or transesterification with a bisarylcarbonate.

[0128] A dihydroxybiphenyl compound has a biphenyl skeleton and has one hydroxyl group on each of the two benzene rings of the biphenyl skeleton. Examples of the dihydroxybiphenyl compound include 4,4'-dihydroxybiphenyl, 4,4'-dihydroxy-3,3'-dimethylbiphenyl, 4,4'-dihydroxy-2,2'-dimethylbiphenyl, 4,4'-dihydroxy-3,3'-dicyclohexylbiphenyl, 3,3'-difluoro-4,4'-dihydroxybiphenyl, and 4,4'-dihydroxy-3,3'-diphenylbiphenyl. These dihydroxybiphenyl compounds may be used alone or in combination.

[0129] Dihydroxybisphenol compounds have a bisphenol skeleton, and each of the two benzene rings of the bisphenol skeleton has one hydroxyl group. Examples of dihydroxybisphenol compounds include bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 1,2-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, 4,4-bis(4-hydroxyphenyl)heptane, 1,1-bis(4-hydroxyphenyl)methane, 1,2-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, 4,4-bis(4-hydroxyphenyl)heptane, 1,1-bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 1,2-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane ... (4-hydroxyphenyl)-1,1-diphenylmethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,1-bis(4-hydroxyphenyl)-1-phenylmethane, bis(4-hydroxyphenyl)ether, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxyphenyl)sulfone, 1,1-bis(4-hydroxyphenyl)cyclopentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(3-methyl-4-hydroxyphenyl) bis(3-methyl-4-hydroxyphenyl)propane, 2-(3-methyl-4-hydroxyphenyl)-2-(4-hydroxyphenyl)-1-phenylethane, bis(3-methyl-4-hydroxyphenyl)sulfide, bis(3-methyl-4-hydroxyphenyl)sulfone, bis(3-methyl-4-hydroxyphenyl)methane, 1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane, 2,2-bis(2-methyl-4-hydroxyphenyl)propane, 1,1-bis(2-butyl-4-hydroxyphenyl) -5-methylphenyl)butane, 1,1-bis(2-tert-butyl-4-hydroxy-3-methylphenyl)ethane, 1,1-bis(2-tert-butyl-4-hydroxy-5-methylphenyl)propane, 1,1-bis(2-tert-butyl-4-hydroxy-5-methylphenyl)butane, 1,1-bis(2-tert-butyl-4-hydroxy-5-methylphenyl)isobutane, 1,1-bis(2-tert-butyl-4-hydroxy-5-methylphenyl)heptane, 1,1-bis(2-tert-butyl-4-hydroxy-5-methylphenyl)-1-phenylmethane, 1,1-bis(2-tert-amyl-4-hydroxy-5-methylphenyl)butane, bis(3-chloro-4-hydroxyphenyl)methane, bis(3,5-dibromo-4-hydroxyphenyl)methane, 2,2-bis(3-chloro-4-hydroxyphenyl)propane, 2,2-bis(3-fluoro-4-hydroxyphenyl)propane, 2,2-bis(3-bromo-4-hydroxyphenyl)propane, 2,2-bis(3,5-difluoro-4-hydroxyphenyl)propane, 2,2-bis(3,5-difluoro-4-hydroxyphenyl)propane, Examples include bis(3,5-dichloro-4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 2,2-bis(3-bromo-4-hydroxy-5-chlorophenyl)propane, 2,2-bis(3,5-dichloro-4-hydroxyphenyl)butane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)butane, 1-phenyl-1,1-bis(3-fluoro-4-hydroxyphenyl)ethane, bis(3-fluoro-4-hydroxyphenyl)ether, and 1,1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclohexane. These bisphenol compounds may be used alone or in combination.

[0130] Among these, from the viewpoint of abrasion resistance, the BP polycarbonate resin is preferably a polycarbonate resin containing at least one of the structural units represented by the following formula (PCA) and the structural units represented by the following formula (PCB). That is, preferred BP polycarbonate resins include homopolymers composed of structural units represented by the following formula (PCA), homopolymers composed of structural units represented by the following formula (PCB), and copolymers thereof. Among these, from the viewpoint of abrasion resistance, polycarbonate resins containing a structural unit represented by the following formula (PCA) are more preferred.

[0131] [ka]

[0132] In the formulas (PCA) and (PCB), R P1 , R P2 , R P3 , and R P4 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an aryl group having 6 to 12 carbon atoms. P1 represents a phenylene group, a biphenylylene group, a naphthylene group, an alkylene group, or a cycloalkylene group.

[0133] In the formulas (PCA) and (PCB), R P1 , R P2 , R P3 , and R P4 The alkyl group represented by the formula (I) includes a linear or branched alkyl group having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms). Specific examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and an n-hexyl group. Specific examples of branched alkyl groups 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, and a tert-hexyl group. Among these, lower alkyl groups such as methyl and ethyl are preferred as the alkyl group.

[0134] In the formulas (PCA) and (PCB), R P1 , R P2 , R P3 , and R P4 Examples of the cycloalkyl group represented by include cyclopentyl, cyclohexyl, and cycloheptyl.

[0135] In the formulas (PCA) and (PCB), R P1 , R P2 , R P3 , and R P4Examples of the aryl group represented by include a phenyl group, a naphthyl group, and a biphenylyl group.

[0136] In the formulas (PCA) and (PCB), X P1 The alkylene group represented by the formula (I) includes a linear or branched alkylene group having 1 to 12 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms). Specific examples of the linear alkylene group include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, an n-octylene group, an n-nonylene group, an n-decylene group, an n-undecylene group, and an n-dodecylene group. Specific examples of branched alkylene groups include an isopropylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, an isopentylene group, a neopentylene group, a tert-pentylene group, an isohexylene group, a sec-hexylene group, a tert-hexylene group, an isoheptylene group, a sec-heptylene group, a tert-heptylene group, an isooctylene group, a sec-octylene group, a tert-octylene group, an isonylene group, a sec-nonylene group, a tert-nonylene group, an isodecylene group, a sec-decylene group, a tert-decylene group, an isoundecylene group, a sec-undecylene group, a tert-undecylene group, a neoundecylene group, an isododecylene group, a sec-dodecylene group, a tert-dodecylene group, and a neododecylene group. Among these, the alkylene group is preferably a lower alkyl group such as a methylene group, an ethylene group, or a butylene group.

[0137] In the formulas (PCA) and (PCB), X P1 Examples of the cycloalkylene group represented by include cycloalkylene groups having 3 to 12 carbon atoms (preferably 3 to 10 carbon atoms, more preferably 5 to 8 carbon atoms). Specific examples of the cycloalkylene group include a cyclopropylene group, a cyclopentylene group, a cyclohexylene group, a cyclooctylene group, and a cyclododecanylene group. Among these, the cycloalkylene group is preferably a cyclohexylene group.

[0138] In the formulas (PCA) and (PCB), R P1 , R P2 , R P3 , R P4 , and X P1 Each of the above substituents represented by the formula (I) also includes a group having a further substituent. Examples of the substituent include a halogen atom (e.g., a fluorine atom, a chlorine atom), an alkyl group (e.g., an alkyl group having 1 to 6 carbon atoms), a cycloalkyl group (e.g., a cycloalkyl group having 5 to 7 carbon atoms), an alkoxy group (e.g., an alkoxy group having 1 to 4 carbon atoms), and an aryl group (e.g., a phenyl group, a naphthyl group, a biphenylyl group, etc.).

[0139] In the formula (PCA), R P1 , and R P2 each independently preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R P1 , and R P2 More preferably, represents a hydrogen atom. In the formula (PCB), R P3 , and R P4 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; X P1 Preferably, represents an alkylene group or a cycloalkylene group.

[0140] Specific examples of BP polycarbonate resins include, but are not limited to, the following: In the example compounds, pm and pn represent copolymerization ratios.

[0141] [ka]

[0142] [ka]

[0143] [ka]

[0144] [ka]

[0145] [ka]

[0146] Here, in the polycarbonate resin, the content (copolymerization ratio) of the structural unit represented by formula (PCA) is preferably in the range of 5 mol % or more and 95 mol % or less, more preferably in the range of 5 mol % or more and 50 mol % or less, and even more preferably in the range of 15 mol % or more and 30 mol % or less, based on all structural units constituting the polycarbonate resin, from the viewpoint of abrasion resistance. Specifically, in the above-mentioned exemplary compounds of polycarbonate resin, pm and pn indicate the copolymerization ratio (molar ratio), and pm:pn is preferably in the range of 95:5 to 5:95, more preferably 50:50 to 5:95, and even more preferably 15:85 to 30:70.

[0147] The single-layer photosensitive layer contains, as binder resins, resin A and resin B. The total content of resin A and resin B in the total content of binder resins contained in the single-layer photosensitive layer is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

[0148] [Hole transport material] The single-layer photosensitive layer contains a hole transport material. Examples of hole-transporting materials include electron-transporting compounds such as quinone-based compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane-based compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone-based compounds; benzophenone-based compounds; cyanovinyl-based compounds; and ethylene-based compounds. Examples of hole-transporting materials include triarylamine-based compounds, benzidine-based compounds, arylalkane-based compounds, aryl-substituted ethylene-based compounds, stilbene-based compounds, anthracene-based compounds, and hydrazone-based compounds. These hole-transporting materials may be used alone or in combination, but are not limited to these.

[0149] Examples of polymeric hole transport materials include known compounds having charge transport properties, such as poly-N-vinylcarbazole and polysilane. For example, polyester-based polymeric charge transport materials are preferred. The polymeric hole transport material may be used alone or in combination with a binder resin.

[0150] Examples of hole transport materials or polymeric hole transport materials 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, pyrazolyl compounds, and the like. Examples of the compounds include triazole compounds, cyano compounds, benzofuran compounds, aniline compounds, butadiene compounds, and resins having groups derived from these substances. Specifically, see paragraphs 0078 to 0080 of JP 2021-117377 A, paragraphs 0046 to 0048 of JP 2019-035900 A, paragraphs 0052 to 0053 of JP 2019-012141 A, paragraphs 0122 to 0134 of JP 2021-071565 A, and paragraphs 0122 to 0134 of JP 2021-015223 A. Examples of the compounds include those described in paragraphs 0101 to 0110 of JP 2013-097300 A, 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.

[0151] From the viewpoint of charge mobility, the hole transport material preferably contains at least one selected from the group consisting of a compound (G1) represented by the following formula (G1), a compound (G2) represented by the following formula (G2), a compound (G3) represented by the following formula (G3), and a compound (G4) represented by the following formula (G4).

[0152] [ka]

[0153] In formula (G1), Ar T1 , Ar T2 and Ar T3 are each independently an aryl group, -C6H4-C(R T4 )=C(R T5 )(R T6 ) or -C6H4-CH=CH-CH=C( R T7 )(R T8 ) is R T4 , R T5 , R T6 , R T7 and R T8 are each independently R is a hydrogen atom, an alkyl group, or an aryl group. T5 and R T6When 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.

[0154] The group in formula (G1) 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.

[0155] From the viewpoint of charge mobility, the compound (G1) is preferably an aryl group or -CH-CH=CH-CH=C(R T7 )(R T8 ) is preferred, and a compound (G'1) represented by the following formula (G'1) is more preferred.

[0156] [ka]

[0157] In formula (G'1), R T111 , R T112 , R T121 , R T122 , R T131 and R T132 are 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.

[0158] [ka]

[0159] In formula (G2), 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 ) is 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.

[0160] The group in formula (G2) 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.

[0161] From the viewpoint of charge mobility, the compound (G2) 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.

[0162] [ka]

[0163] In formula (G3), 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.

[0164] The group in formula (G3) 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.

[0165] [ka]

[0166] In formula (G4), 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 , RT42 , 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.

[0167] The group in formula (G4) 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.

[0168] The content of the hole transport material in the single-layer photosensitive layer is preferably 5% by mass or more and 50% by mass or less with respect to the total mass of the single-layer photosensitive layer.

[0169] [Electron transport material] The single-layer photosensitive layer contains an electron transport material. Examples of electron transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds. One type of electron transport material may be used alone, or two or more types may be used in combination.

[0170] From the viewpoints of sensitivity and suppressing the occurrence of color spots, the electron transport material preferably contains a compound represented by the following formula, and more preferably is a compound represented by the following formula (3).

[0171] [ka]

[0172] R t1~R t4 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a cycloalkyl group, an aryl group, or an aralkyl group.

[0173] R t1 ~R t4 are each preferably independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group. Also, R t1 is R t2 ~R t4 It is preferable that the group is different from at least one of the above.

[0174] R t1 and R t3 are each independently, from the viewpoints of sensitivity and suppression of color spot occurrence, preferably an alkyl group having from 3 to 12 carbon atoms, an alkoxy group having from 3 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group; more preferably a branched alkyl group having from 3 to 12 carbon atoms, a branched alkoxy group having from 3 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group; still more preferably a branched alkyl group having from 3 to 8 carbon atoms or a branched alkoxy group having from 3 to 8 carbon atoms; and particularly preferably a t-butyl group. In addition, from the viewpoint of sensitivity and suppression of color dots, R t1 and R t3 are preferably the same group.

[0175] R t2 and R t4 are each independently, from the viewpoints of sensitivity and suppression of color spot occurrence, preferably a hydrogen atom, an alkyl group having from 1 to 8 carbon atoms, or an alkoxy group having from 1 to 8 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having from 1 to 4 carbon atoms, or a linear alkoxy group having from 1 to 4 carbon atoms, even more preferably a linear alkyl group having from 1 to 3 carbon atoms or a linear alkoxy group having from 1 to 3 carbon atoms, and particularly preferably a methyl group. In addition, from the viewpoint of sensitivity and suppression of color dots, R t2and R t4 are preferably the same group. Furthermore, from the viewpoint of sensitivity and suppression of color dots, R t1 and R t2 are preferably different groups, and R t3 and R t4 It is preferable that the group is different from the group

[0176] The compound represented by the formula (3) is preferably a compound represented by the following formula (3-1) from the viewpoints of sensitivity and suppression of color dot generation.

[0177] [ka]

[0178] In formula (3-1), R t5 ~R t8 each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group; and R t5 is R t6 ~R t8 is a group different from at least one of the above.

[0179] R in formula (3-1) t5 ~R t8 A preferred embodiment of R t5 ~R t8 The number of carbon atoms in the alkyl group and alkoxy group in R is 1 or more and 12 or less, and R t5 is R t6 ~R t8 Each of R in formula (3) is a group different from at least one of t1 ~R t4 This is the same as the preferred embodiment of the above.

[0180] Exemplary compounds of the electron transport material represented by formula (3) are shown below, but the present invention is not limited to these. From the viewpoints of sensitivity and suppressing the occurrence of color dots, the electron transport material preferably contains the following exemplary compounds 1 to 6, more preferably contains the following exemplary compound 1, and particularly preferably is the following exemplary compound 1.

[0181] [ka]

[0182] The abbreviations in the above exemplary compounds have the following meanings. t-C4H9: t-butyl group CH3O: methoxy group t-C4H9O: t-butoxy group c-C6H 11 : Cyclohexyl group C6H5: Phenyl group C6H5CH2: benzyl group

[0183] When the compound represented by formula (3) is used, it may be used in combination with an electron transport material other than the compound represented by formula (3). When the compound represented by formula (3) is used in combination with an electron transport material other than the compound represented by formula (3), it is preferable that the amount of the compound represented by formula (3) is 90 mass % or more based on the total amount of the electron transport material.

[0184] As the electron transport material, from the viewpoint of increasing the sensitivity of the photosensitive layer, a fluorenone compound is preferred, and among the fluorenone compounds, a compound represented by formula (F2) is preferred.

[0185] [ka]

[0186] In formula (F2), R f11 , R f12 , R f13 , R f14 , R f15 , R f16 and R f17each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryl group, or an aralkyl group; R f18 is an alkyl group, an aryl group, an aralkyl group or -L f19 -OR f20 (However, L f19 represents an alkylene group, and R f20 represents an alkyl group.

[0187] In formula (F2), R f11 ~R f17 Examples of the halogen atom represented by include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom and a chlorine atom being preferred, and a chlorine atom being more preferred.

[0188] In formula (F2), R f11 ~R f17Examples of the alkyl group represented by include a linear or branched alkyl group having 1 to 20 carbon atoms (preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 3). Examples of the linear alkyl group 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, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, and an n-icosyl group. Examples of branched alkyl groups 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, a tert-decyl group, an isoundecyl group, a sec-undecyl group, a tert-undecyl group, a neoundecyl group, an isododecyl group, a sec-dodecyl group, a tert-dodecyl group, a neododecyl group, an isotridecyl group, a sec-tridecyl group, a tert-tridecyl group, a neotridecyl group, an isotetradecyl group, Examples of such an alkyl group include a sec-tetradecyl group, a tert-tetradecyl group, a neotetradecyl group, a 1-isobutyl-4-ethyloctyl group, an isopentadecyl group, a sec-pentadecyl group, a tert-pentadecyl group, a neopentadecyl group, an isohexadecyl group, a sec-hexadecyl group, a tert-hexadecyl group, a neohexadecyl group, a 1-methylpentadecyl group, an isoheptadecyl group, a sec-heptadecyl group, a tert-heptadecyl group, a neoheptadecyl group, an isooctadecyl group, a sec-octadecyl group, a tert-octadecyl group, a neooctadecyl group, an isononadecyl group, a sec-nonadecyl group, a tert-nonadecyl group, a neononadecyl group, a 1-methyloctyl group, an isoicosyl group, a sec-icosyl group, a tert-icosyl group, and a neoicosyl group. Of these, the alkyl group is preferably a methyl group or an ethyl group.

[0189] In formula (F2), R f11 ~R f17Examples of the alkoxy group represented by include linear or branched alkoxy groups having 1 to 20 carbon atoms (preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 3). Examples of the linear alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, an n-octyloxy group, an n-nonyloxy group, an n-decyloxy group, an n-undecyloxy group, an n-dodecyloxy group, an n-tridecyloxy group, an n-tetradecyloxy group, an n-pentadecyloxy group, an n-hexadecyloxy group, an n-heptadecyloxy group, an n-octadecyloxy group, an n-nonadecyloxy group, and an n-icosyloxy group.Examples of branched alkoxy groups 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, a tert-hexyloxy group, an isoheptyloxy group, a sec-heptyloxy group, a tert-heptyloxy group, an isooctyloxy group, a sec-octyloxy group, a tert-octyloxy group, an isononyloxy group, and a sec-no nyloxy group, tert-nonyloxy group, isodecyloxy group, sec-decyloxy group, tert-decyloxy group, isoundecyloxy group, sec-undecyloxy group, tert-undecyloxy group, neoundecyloxy group, isododecyloxy group, sec-dodecyloxy group, tert-dodecyloxy group, neododecyloxy group, isotridecyloxy group, sec-tridecyloxy group, tert-tridecyloxy group, neotridecyloxy group, isotetradecyloxy group oxy group, sec-tetradecyloxy group, tert-tetradecyloxy group, neotetradecyloxy group, 1-isobutyl-4-ethyloctyloxy group, isopentadecyloxy group, sec-pentadecyloxy group, tert-pentadecyloxy group, neopentadecyloxy group, isohexadecyloxy group, sec-hexadecyloxy group, tert-hexadecyloxy group, neohexadecyloxy group, 1-methylpentadecyloxy group, isoheptadecyloxy group, sec-hexadecyloxy group Examples of alkoxy groups include butadecyloxy group, tert-heptadecyloxy group, neoheptadecyloxy group, isooctadecyloxy group, sec-octadecyloxy group, tert-octadecyloxy group, neooctadecyloxy group, isononadecyloxy group, sec-nonadecyloxy group, tert-nonadecyloxy group, neononadecyloxy group, 1-methyloctyloxy group, isoicosyloxy group, sec-icosyloxy group, tert-icosyloxy group, neoicosyloxy group, etc. Among these, the alkoxy group is preferably a methoxy group.

[0190] In formula (F2), R f11 ~R f17Examples of the aryl group represented by the formula (I) include aryl groups having 6 to 30 carbon atoms (preferably 6 to 20, more preferably 6 to 16). Specific examples include a phenyl group, a biphenylyl group, a naphthyl group, and a phenanthryl group, with a phenyl group and a naphthyl group being preferred. These aryl groups may have 1 to 5 (preferably 1 or 2) substituents, and examples of the substituents include a linear or branched alkyl group having 1 to 4 carbon atoms (e.g., a methyl group, an ethyl group), a linear or branched alkoxy group having 1 to 4 carbon atoms (e.g., a methoxy group, an ethoxy group), and a halogen atom (e.g., a fluorine atom, a chlorine atom).

[0191] In formula (F2), R f11 ~R f17 Examples of the aralkyl group represented by the formula (I) include a group in which a phenyl group, a biphenylyl group, a naphthyl group, or the like is bonded to a linear or branched alkylene group having from 1 to 6 carbon atoms (e.g., a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, a pentylene group, or a hexylene group), and a benzyl group or a phenethyl group is preferred. The benzene ring of these aralkyl groups may have one to five (preferably one or two) substituents, and examples of the substituents include a linear or branched alkyl group having from 1 to 4 carbon atoms (e.g., a methyl group, an ethyl group), a linear or branched alkoxy group having from 1 to 4 carbon atoms (e.g., a methoxy group, an ethoxy group), and a halogen atom (e.g., a fluorine atom, a chlorine atom).

[0192] In formula (F2), R f18 The alkyl group represented by R f11 ~R f17 The alkyl group represented by R f18 The alkyl group represented by is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 4 to 10 carbon atoms, and even more preferably a branched alkyl group having 5 to 10 carbon atoms.

[0193] In formula (F2), R f18 The aryl group represented by Rf11 ~R f17 The same groups as the aryl group represented by R f18 From the viewpoint of solubility in organic solvents, the aryl group represented by R is preferably an alkyl-substituted aryl group substituted with an alkyl group. f18 The aryl group represented by is preferably a phenyl group, a methylphenyl group, a dimethylphenyl group or an ethylphenyl group.

[0194] In formula (F2), R f18 The aralkyl group represented by R 11 ~R 17 The same groups as the aralkyl group represented by R f18 From the viewpoint of solubility in organic solvents, the aralkyl group represented by R is preferably an alkyl-substituted aralkyl group substituted with an alkyl group. f18 The aralkyl group represented by is preferably a benzyl group, a methylbenzyl group, a dimethylbenzyl group or a phenethyl group.

[0195] In formula (F2), R f18 Represents -L f19 -OR 20 (However, L f19 represents an alkylene group, and R f20 represents an alkyl group. f19 Examples of R include linear or branched alkylene groups having 1 to 6 carbon atoms (e.g., methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, sec-butylene, tert-butylene, pentylene, and hexylene groups), and R f20 As for R f11 ~R f17 Examples of the alkyl group include the same groups as those represented by the alkyl group represented by the formula:

[0196] From the viewpoint of increasing the sensitivity of the photosensitive layer, the compound represented by formula (F2) is preferably R f11 ~R f17 are each independently a hydrogen atom, a halogen atom, or an alkyl group, and R f18 is an alkyl group having 4 to 10 carbon atoms.

[0197] Exemplary compounds of the compound represented by formula (F2) are shown below: The compound represented by formula (F2) is not limited to these.

[0198] [ka]

[0199] The electron transport material may be used alone or in combination of two or more. The content of the electron transport material is preferably 5 to 20 parts by mass, more preferably 10 to 25 parts by mass, and even more preferably 15 to 20 parts by mass, based on the total mass of the photosensitive layer.

[0200] [Charge-Generating Material] The single-layer photosensitive layer contains a charge generating material. 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.

[0201] 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, and more specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine are more preferable.

[0202] 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.

[0203] The above charge-generating materials may also be used when using incoherent light sources such as LEDs and organic EL image arrays that emit light at a central wavelength of 450 nm to 780 nm. However, from the viewpoint of resolution, when using a thin photosensitive layer of 20 μm or less, the electric field strength in the photosensitive layer becomes high, and charge injection from the substrate can easily cause a decrease in charging, resulting in image defects known as black spots. This problem becomes more pronounced when using charge-generating materials that are p-type semiconductors, such as trigonal selenium and phthalocyanine pigments, that are prone to generating dark current.

[0204] 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.

[0205] 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.

[0206] The single-layer photosensitive layer may contain other known additives, such as antioxidants, leveling agents, antifoaming agents, fillers, and viscosity modifiers.

[0207] The formation of the single-layer type photosensitive layer is not particularly limited, and a well-known formation method can be used. For example, the single-layer type photosensitive layer can be formed by forming a coating film of a coating liquid for forming a single-layer type photosensitive layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0208] Examples of solvents for preparing a coating solution for forming a single-layer photosensitive layer include common 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.

[0209] Examples of the coating method for applying the coating solution for forming a single-layer type photosensitive layer include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0210] The average thickness of the single-layer photosensitive layer is preferably from 20 μm to 50 μm, more preferably from 25 μm to 45 μm, and even more preferably from 30 μm to 40 μm.

[0211] (Conductive substrate) The positively charged electrophotographic photoreceptor according to this embodiment preferably includes a conductive substrate and a single-layer photosensitive layer disposed on the 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 Ωcm.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] (subbing layer) The positively charged electrophotographic photoreceptor according to this embodiment may have an undercoat layer between the conductive substrate and the single-layer photosensitive layer. The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0220] For example, inorganic particles have a powder resistance (volume resistivity) of 1×10 2 Ωcm or more 1×10 11 Examples include inorganic particles with a particle size of Ωcm 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.

[0221] 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).

[0222] 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.

[0223] The inorganic particles may be surface-treated. The inorganic particles may be different in surface treatment, or Two or more kinds of particles having different particle sizes may be mixed and used.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] The electron-accepting compound can be attached to the surface of inorganic particles by, for example, a dry method or and wet methods.

[0233] 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.

[0234] The wet method involves dispersing inorganic particles in a solvent using, for example, stirring, ultrasonic waves, a sand mill, an attritor, or a ball mill, while adding an electron-accepting compound. The mixture is stirred or dispersed, 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 of removing the moisture by stirring and heating in a solvent, and a method of removing the moisture by azeotropy with the solvent.

[0235] 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.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] The undercoat layer may contain various additives to improve electrical properties, environmental stability, and image quality. Additives include electron transport pigments such as polycyclic condensation pigments and azo pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, and titanium alkoxides. Examples of the silane coupling agent include known materials such as titanium compounds, organic titanium compounds, and silane coupling agents. The silane coupling agent is used for the surface treatment of the inorganic particles as described above, and may also be added to the undercoat layer as an additive.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, ethyl acetoacetate aluminum diisopropylate, and aluminum tris(ethyl acetoacetate).

[0244] These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] 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.

[0249] 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.

[0250] The thickness of the undercoat layer is set, for example, preferably at least 15 μm, more preferably in the range of from 20 μm to 50 μm.

[0251] (middle class) The positively charged electrophotographic photoreceptor according to this exemplary embodiment may further include an intermediate layer between the undercoat layer and the single-layer 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.

[0252] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0253] 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.

[0254] 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.

[0255] (protective layer) A protective layer may be provided on the single-layer 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 single-layer 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).

[0256] 1) A layer composed of a cured film of a composition containing a reactive group-containing hole transport material having a reactive group and a hole transport skeleton in the same molecule (i.e., a layer containing a polymer or crosslinked product of the reactive group-containing hole transport material). 2) A layer composed of a cured film of a composition containing a non-reactive hole transport material and a reactive group-containing non-hole transport material that does not have a hole transport skeleton and has a reactive group (i.e., a layer containing a non-reactive hole transport material and a polymer or crosslinked product of the reactive group-containing non-hole transport material).

[0257] Examples of the reactive group of the reactive group-containing hole transport material include a chain polymerizable group, an epoxy group, -OH, -OR (wherein R represents an alkyl group), -NH2, -SH, -COOH, and -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.

[0258] 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.

[0259] The hole transport skeleton of the reactive group-containing hole 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.

[0260] The reactive group-containing hole transport material having a reactive group and a hole transporting skeleton, the non-reactive hole transport material, and the reactive group-containing non-hole transport material may be selected from known materials.

[0261] The protective layer may also contain other known additives.

[0262] 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.

[0263] 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.

[0264] 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.

[0265] 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.

[0266] <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, wherein the charging device is a positive charging type charging device.The positive charging type electrophotographic photosensitive member according to the present embodiment is used as the electrophotographic photosensitive member.

[0267] 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.

[0268] 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.

[0269] 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).

[0270] 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.

[0271] 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.

[0272] FIG. 2 is a schematic diagram showing an example of the configuration of an image forming apparatus according to this embodiment. As shown in FIG. 2, the image forming apparatus 100 according to this 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.

[0273] 2 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.

[0274] FIG. 2 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.

[0275] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0276] -Charging device- The charging device 8 is a positive charging type charging device. The charging device 8 may be any charging device capable of positive charging, and 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.

[0277] -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.

[0278] -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.

[0279] 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.

[0280] -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.

[0281] -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.

[0282] -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.

[0283] FIG. 3 is a schematic diagram showing another example of the configuration of the image forming apparatus according to the present embodiment. 3 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer 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]

[0284] 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.

[0285] The elastic deformation rate of the resin was measured by the following method. The elastic deformation rate of the resin was calculated using the following formula. Elastic deformation rate = (Dmax-D1) / Dmax Here, the elastic deformation rate is defined as follows: when a load is applied to the photosensitive layer, the total deformation amount is divided into the elastic deformation amount and the plastic deformation amount, and the elastic deformation rate is defined as elastic deformation amount / total deformation amount. The elastic deformation rate was measured in an environment of 24°C and 50%RH using a Nanoindenter SA2 manufactured by MTS, in which a diamond equilateral triangular pyramid indenter was used to indent the exposed surface of each resin in the photosensitive layer to a depth of 0.5µm at an indentation speed of 0.025µm / s. In this measurement, the strain depth was determined as the amount of deformation that did not recover under load, and the deformation amount (depth) of the resin at the end of the measurement was obtained. The maximum indentation depth was 0.5µm, which is the indentation depth of the diamond equilateral triangular pyramid indenter.

[0286] <Preparation of polyarylate resin PA1> A reaction vessel equipped with a stirrer was charged with 12.7220 g of 2,2'-dimethyl-4,4'-(1,3-dimethylbutylidene)diphenol, 0.1233 g of 4-t-butylphenol, 0.0632 g of sodium hydrosulfite, and 240 mL of water to form a suspension. To this suspension, 4.8392 g of sodium hydroxide, 0.1981 g of benzyltributylammonium chloride, and 160 mL of water were added with stirring at 20°C, and the mixture was stirred for 30 minutes under a nitrogen atmosphere. 220 mL of o-dichlorobenzene was added to the resulting solution, and the mixture was stirred for 30 minutes under a nitrogen atmosphere. 12.0000 g of 4,4'-biphenyldicarbonyl chloride (powder) was then added. After the addition was complete, the mixture was stirred at 20°C under a nitrogen atmosphere for 4 hours to allow the reaction to proceed. The polymerized solution was diluted with 300 mL of o-dichlorobenzene, and the aqueous layer was removed. After washing with a dilute acetic acid solution and ion-exchanged water, the polymer was precipitated by pouring it into methanol, and the precipitated polymer was filtered off and dried at 50°C. The resulting polymer was post-treated as follows to obtain a final product. The polymer was redissolved in 900 mL of tetrahydrofuran and poured into methanol to precipitate the polymer. The precipitated polymer was filtered, washed with methanol, and dried at 50°C. This procedure was repeated three times to obtain 17.5 g of polyarylate resin PA1, which is a white polymer.

[0287] [ka]

[0288] <Polycarbonate resins PB1 to PB3> The following polycarbonate resins PB1 to PB3 were prepared.

[0289] [ka]

[0290] The numbers in the parentheses at the bottom right of PA1 and PB1 to PB3 represent the molar ratio.

[0291] <Polyester resin PB4> The polyester resin PB4 prepared contained 50 mol % of the dicarboxylic acid unit (A-12) described above, 37.5 mol % of the diol unit (B-2) described above, and 12.5 mol % of the diol unit (B-4) described above.

[0292] (Examples 1 to 15 and Comparative Examples 1 to 4) A total of 52.75 parts of Resin A and Resin B listed in Table 1 in the mass ratio listed in Table 1, 1.25 parts of V-type hydroxygallium phthalocyanine (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.3°, 16.0°, 24.9°, and 28.0° in an X-ray diffraction spectrum using CuKα characteristic X-rays) as a charge generating material, 7.8 parts of the above-mentioned Exemplary Compound 2-2 as an electron transporting material, 38.2 parts of the following Compound CTM-1 represented by Formula (G2) as a hole transporting material (mass ratio of electron transporting material (Formula 2-2) to hole transporting material CTM-1: 17:83), and 175 parts of tetrahydrofuran and 75 parts of toluene as solvents were mixed, and the mixture was dispersed for 4 hours in a sand mill using 1 mm diameter glass beads to obtain a coating solution for forming a single-layer photosensitive layer. The photosensitive layer-forming coating liquid was applied onto an aluminum substrate having an outer diameter of 30 mm, a length of 244.5 mm, and a thickness of 1 mm by a dip coating method, and then dried and cured at a temperature of 110°C for 40 minutes to form a single-layer photosensitive layer having an average thickness of 37 μm, thereby obtaining a positively charged electrophotographic photoreceptor.

[0293] [ka]

[0294] <Evaluation> [Prevents the occurrence of color spots caused by corrosion] To evaluate color spots caused by corrosion, a modified Brother HL5340D equipped with a photoreceptor was used to print 2,000 sheets of halftone 50% at a charging voltage of +800V in a high temperature and high humidity environment of 28°C and 85%RH. The printer was then stopped overnight, and the following morning, blank paper was transported through the printer and the number of color spots that appeared on the paper was counted and evaluated according to the following criteria. A: No color spots occurred. B: Color points are 1 to 9. C: 10 or more color points.

[0295] [Wear resistance] To evaluate abrasion resistance, the photoreceptor film thickness was measured using an eddy current film thickness measuring device (manufactured by Fisher Instruments) before and after printing 10,000 A4 sheets of halftone images with an image density of 30% using the modified machine, and the film thickness reduction rate was calculated by dividing the amount of film thickness reduction by the number of test cycles.The evaluation criteria are as follows. A: 5nm / kcy or less B: Over 5nm / kcy and up to 10nm / kcy C: Over 10nm / kcy and up to 20nm / kcy D: Over 20nm / kcy

[0296] [Table 1]

[0297] As shown in Table 1, the positively charged electrophotographic photoreceptors of Examples 1 to 15 were superior to the positively charged electrophotographic photoreceptors of Comparative Examples 1 to 4 in both the ability to suppress the occurrence of color spots due to corrosion and the abrasion resistance.

[0298] (((1))) A positively charged electrophotographic photoreceptor having a single-layer photosensitive layer containing a hole transport material, an electron transport material, a charge generating material, and a binder resin, wherein the binder resin contains a resin A having an elastic deformation rate of 53.0% or more and a resin B having an elastic deformation rate difference from that of the resin A of 12% or more and 17% or less. (((2))) The positively charged electrophotographic photoreceptor according to (((1))), wherein the mass ratio MA / MB of the content MA of the resin A to the content MB of the resin B is 0.25 or more and 4 or less. (((3))) The positively charged electrophotographic photoreceptor according to (((2))), wherein the mass ratio MA / MB of the content MA of the resin A to the content MB of the resin B is 0.4 or more and 2.5 or less. (((4))) The positively charged electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the difference in elastic deformation rate between the resin B and the resin A is 13% or more and 16% or less. (((5))) The positively charged electrophotographic photoreceptor according to any one of (((1))) to (((4))), wherein the elastic deformation rate of the resin B is 12% or more and 17% or less than the elastic deformation rate of the resin A. (((6))) The positively charged electrophotographic photoreceptor according to any one of (((1))) to (((5))), wherein the resin A is a polyarylate resin. (((7))) The positively charged electrophotographic photoreceptor according to any one of (((1))) to (((6))), wherein the resin B is a polycarbonate resin. (((8))) The positively charged electrophotographic photoreceptor according to any one of (((1))) to (((7))), wherein the resin A has a biphenyl structure. (((9))) The positively charged electrophotographic photoreceptor according to any one of (((1))) to (((8))), wherein the resin B has a biphenyl structure. (((10))) A process cartridge detachably mounted on an image forming apparatus, comprising the positively charged electrophotographic photosensitive member according to any one of (((1))) to (((9))). (((11))) An image forming apparatus comprising: a positively charged electrophotographic photosensitive member according to any one of (((1))) to (((9))); 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 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; and a transfer device that transfers the toner image to the surface of a recording medium, wherein the charging device is a positively charged charging device.

[0299] According to the invention related to (((1))), a positively charged electrophotographic photoreceptor is provided which is superior in the ability to suppress the occurrence of color spots caused by corrosion and in the abrasion resistance, compared to when the binder resin in the single-layer photosensitive layer contains resin A having an elastic deformation rate of 53.0% or more and resin B having an elastic deformation rate difference from resin A of less than 12% or more than 17%. According to the invention related to (((2))), a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion compared to when the mass ratio MA / MB of the content MA of the resin A to the content MB of the resin B is less than 0.25 or more than 4. According to the invention related to (((3))), a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion compared to when the mass ratio MA / MB of the content MA of the resin A to the content MB of the resin B is less than 0.25 or more than 4. According to the invention related to (((4))), a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion, compared to when the difference in elastic deformation rate between the resin B and the resin A is less than 13% or more than 16%. According to the invention related to (((5))), a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion compared to when the elastic deformation rate of the resin B is 12% or more and 17% or less than the elastic deformation rate of the resin A. According to the invention related to (((6))), a positively charged electrophotographic photoreceptor is provided which is superior in suppressing the occurrence of color spots caused by corrosion and in abrasion resistance compared to when the resin A is a polyester resin other than a polyarylate resin. According to the invention related to (((7))), a positively charged electrophotographic photoreceptor is provided which has superior abrasion resistance and superior suppression of the occurrence of color spots caused by corrosion, compared to when the resin B is a polyester resin. According to the invention related to (((8))), a positively charged electrophotographic photoreceptor is provided in which the resin A has superior abrasion resistance and superior suppression of the occurrence of color spots caused by corrosion, compared to when the resin A does not have a biphenyl structure. According to the invention related to (((9))), a positively charged electrophotographic photoreceptor is provided which is superior in abrasion resistance and in suppressing the occurrence of color spots caused by corrosion, compared to when the resin B does not have a biphenyl structure. According to the invention of (((10))) or (((11))), there is provided a process cartridge or an image forming apparatus which is superior in the ability to suppress the occurrence of color spots caused by corrosion in a positively charged electrophotographic photosensitive member and in the abrasion resistance, compared to when the binder resin in the single-layer photosensitive layer of the positively charged electrophotographic photosensitive member contains resin A having an elastic deformation rate of 53.0% or more and resin B having an elastic deformation rate difference from resin A of less than 12% or more than 17%. [Explanation of symbols]

[0300] 1 conductive substrate, 2 undercoat layer, 5 single-layer photosensitive layer, 10B positively charged electrophotographic photosensitive member, 7 (positively charged type) 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 single-layer photosensitive layer including a hole transport material, an electron transport material, a charge generating material, and a binder resin; The binder resin includes a resin A having an elastic deformation rate of 53.0% or more and a resin B having an elastic deformation rate difference from that of the resin A of 12% to 17%. Positively charged electrophotographic photoreceptor.

2. 2. The positively charged electrophotographic photoreceptor according to claim 1, wherein a mass ratio MA / MB of a content MA of the resin A to a content MB of the resin B is 0.25 or more and 4 or less.

3. 3. The positively charged electrophotographic photoreceptor according to claim 2, wherein a mass ratio MA / MB of the content MA of the resin A to the content MB of the resin B is 0.4 or more and 2.5 or less.

4. 2. The positively charged electrophotographic photoreceptor according to claim 1, wherein the difference in elastic deformation rate between said resin B and said resin A is 13% or more and 16% or less.

5. 2. The positively charged electrophotographic photoreceptor according to claim 1, wherein the elastic deformation rate of said resin B is smaller than the elastic deformation rate of said resin A by 12% to 17%.

6. 2. The positively charged electrophotographic photoreceptor according to claim 1, wherein the resin A is a polyarylate resin.

7. 2. The positively charged electrophotographic photoreceptor according to claim 1, wherein the resin B is a polycarbonate resin.

8. 2. The positively charged electrophotographic photoreceptor according to claim 1, wherein the resin A has a biphenyl structure.

9. 2. The positively charged electrophotographic photoreceptor according to claim 1, wherein the resin B has a biphenyl structure.

10. A positively charged electrophotographic photoreceptor according to any one of claims 1 to 9, A process cartridge that is detachably attached to an image forming apparatus.

11. The positively charged electrophotographic photoreceptor according to any one of claims 1 to 9, 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; Equipped with The charging device is a positive charging device. Image forming device.

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