Image forming unit and image forming apparatus

Abstract

To provide an image forming unit that prevents wear of a photoreceptor.SOLUTION: An image forming unit comprises a photoreceptor, and an electrifying member that is in contact with a surface of the photoreceptor to electrify the photoreceptor. The photoreceptor has a conductive substrate, and a laminated photosensitive layer arranged on the conductive substrate and having a charge generating layer and a charge transport layer. The charge transport layer contains at least one of polyester resin having a constitutional unit having an aromatic ring and polycarbonate resin having a constitutional unit having an aromatic ring. The electrifying member has a support member and an elastic layer arranged on the support member. The elastic layer has a storage elastic modulus G' at a frequency of 100 Hz of 5.0 MPa or less in dynamic viscoelasticity measurement at a temperature of 24°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure provides an image forming unit and an image forming apparatus. [Background technology]

[0002] Patent Document 1 describes a photoreceptor having a surface layer containing a resin and a charge transport material, and a charging member that charges the photoreceptor, wherein the average value of the Martens hardness of the surface layer of the photoreceptor is 245 N / mm². 2 The above is the result, and the average value of the Martens hardness in the core portion of the surface of the charged member is 2 N / mm². 2 More than 20N / mm 2 A process cartridge is disclosed that is as follows and has an average viscosity of 70mV or less.

[0003] Patent Document 2 discloses a process cartridge comprising a charging member and a photoreceptor that is contact-charged by the charging member, wherein the surface layer of the charging member contains insulating hollow particles and a binder, the hollow particles form protrusions exposed on the surface of the surface layer, the average thickness of the shells of the hollow particles is 0.05 μm or more and 3.00 μm or less, and the average diameter of the hollow part of the hollow particles is 7 μm or more and 100 μm or less, and the surface layer of the photoreceptor contains a charge transport material and a polycarbonate resin having an aromatic ring or a polyester resin having an aromatic ring. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-95784 [Patent Document 2] Japanese Patent Publication No. 2019-95674 [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of this disclosure is to provide an image forming unit in which wear of the photoreceptor is suppressed compared to an image forming unit equipped with a charging member having an elastic layer whose storage modulus G' at a frequency of 100 Hz exceeds 5.0 MPa in dynamic viscoelastic measurement at a temperature of 24°C. [Means for solving the problem]

[0006] The following embodiments are included as specific means for solving the aforementioned problems. <1> Photoreceptor and The system comprises a charging member that contacts the surface of the photoreceptor and charges the photoreceptor, The photoreceptor comprises a conductive substrate and a multilayer photoreceptor having a charge generation layer and a charge transport layer disposed on the conductive substrate. The charge transport layer contains at least one of a polyester resin having a constituent unit having an aromatic ring and a polycarbonate resin having a constituent unit having an aromatic ring. The charging member comprises a support member and an elastic layer disposed on the support member. The elastic layer has a storage modulus G' of 5.0 MPa or less at a frequency of 100 Hz in a dynamic viscoelasticity measurement at a temperature of 24°C. Image forming unit. <2> Photoreceptor and The system comprises a charging member that contacts the surface of the photoreceptor and charges the photoreceptor, The photoreceptor comprises a conductive substrate and a single-layer photoreceptor disposed on the conductive substrate. The single-layer photosensitive layer contains at least one of a polyester resin having a structural unit having an aromatic ring and a polycarbonate resin having a structural unit having an aromatic ring. The charging member comprises a support member and an elastic layer disposed on the support member. The elastic layer has a storage modulus G' of 5.0 MPa or less at a frequency of 100 Hz in a dynamic viscoelasticity measurement at a temperature of 24°C. Image forming unit. <3> The elastic layer of the charging member has a storage modulus G' of 1.0 MPa or more. <1> or <2> The image forming unit described above. <4> The elastic layer of the charged member has a storage modulus G' of 1.0 MPa or more and 3.5 MPa or less. <1> ~ <3> An image forming unit as described in any one of the items. <5> The elastic layer of the charging member contains an elastic material, carbon black, and calcium carbonate, wherein the carbon black is contained in an amount of 1 to 10 parts by mass and the calcium carbonate in an amount of 10 to 40 parts by mass per 100 parts by mass of the elastic material. <1> ~ <4> An image forming unit as described in any one of the items. <6> The polyester resin having the aromatic ring constituent unit comprises a polyester resin (1) having a dicarboxylic acid unit (A) represented by formula (A) and a diol unit (B) represented by formula (B). <1> ~ <5> An image forming unit as described in any one of the items. <7> The dicarboxylic acid unit (A) represented by formula (A) includes at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by formula (A1), a dicarboxylic acid unit (A2) represented by formula (A2), a dicarboxylic acid unit (A3) represented by formula (A3), and a dicarboxylic acid unit (A4) represented by formula (A4). <6> The image forming unit described above. <8> The diol unit (B) represented by formula (B) includes at least one selected from the group consisting of diol units (B1) represented by formula (B1), diol units (B2) represented by formula (B2), diol units (B3) represented by formula (B3), diol units (B4) represented by formula (B4), diol units (B5) represented by formula (B5), diol units (B6) represented by formula (B6), diol units (B7) represented by formula (B7), and diol units (B8) represented by formula (B8). <6> or <7> The image forming unit described above. <9> The polycarbonate resin having the aromatic ring component includes a polycarbonate resin (1) having a component (C) represented by formula (C). <1> ~ <8> An image forming unit as described in any one of the items. <10> The constituent unit (C) represented by formula (C) includes at least one selected from the group consisting of constituent units (Ca1) represented by formula (Ca1), constituent units (Ca2) represented by formula (Ca2), constituent units (Ca3) represented by formula (Ca3), constituent units (Ca4) represented by formula (Ca4), constituent units (Cb1) represented by formula (Cb2), constituent units (Cb3) represented by formula (Cb4), constituent units (Cb5) represented by formula (Cb5), constituent units (Cb6) represented by formula (Cb7) represented by formula (Cb7) and constituent units (Cb8) represented by formula (Cb8). <9> The image forming unit described above. <11> <1> ~ <10> A process cartridge comprising an image forming unit as described in any one of the items, which can be attached to and detached from an image forming apparatus. <12> <1> ~ <10> An image forming unit as described in any one of the items, An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged photoreceptor, A developing means that develops the electrostatic latent image formed on the surface of the photoreceptor with a developer containing toner to form a toner image, An image forming apparatus comprising a transfer means for transferring the toner image onto the surface of a recording medium. [Effects of the Invention]

[0007] <1> , <2> , <4> , <6> , <7> , <8> , <9> , <10> or <11> According to the report, compared to an image forming unit equipped with a charging member having an elastic layer whose storage modulus G' at a frequency of 100 Hz exceeds 5.0 MPa in dynamic viscoelasticity measurements at a temperature of 24°C, an image forming unit is provided in which wear of the photoreceptor is suppressed. <3> According to the report, compared to an image forming unit equipped with a charged member having an elastic layer whose storage modulus G' at a frequency of 100 Hz is less than 1.0 MPa in dynamic viscoelasticity measurements at a temperature of 24°C, an image forming unit is provided in which contamination of the charged member is suppressed, thereby reducing the likelihood of image quality defects caused by contamination. <5> According to this, an image forming unit is provided in which wear of the photoreceptor is suppressed compared to an image forming unit equipped with a charging member having an elastic layer in which the carbon black content or calcium carbonate content falls outside the above range. <11> According to the report, a process cartridge is provided in which wear of the photoreceptor is suppressed compared to a process cartridge equipped with a charging member having an elastic layer whose storage modulus G' at a frequency of 100 Hz exceeds 5.0 MPa in dynamic viscoelasticity measurements at a temperature of 24°C. <12> According to the report, an image forming apparatus is provided that suppresses wear of the photoreceptor compared to an image forming apparatus equipped with a charged member having an elastic layer in which the storage modulus G' at a frequency of 100 Hz exceeds 5.0 MPa in dynamic viscoelasticity measurements at a temperature of 24°C. [Brief explanation of the drawing]

[0008] [Figure 1] This is a partial cross-sectional view showing an example of the layer configuration of the photoreceptor in the image forming unit according to the first embodiment. [Figure 2] This is a partial cross-sectional view showing an example of the layer configuration of the photoreceptor in the image forming unit according to the second embodiment. [Figure 3] This is a schematic perspective view showing an example of a charging member included in the image forming unit according to this embodiment. [Figure 4] This is a schematic diagram showing an example of an image forming apparatus according to this embodiment. [Figure 5] This is a schematic diagram showing another example of the image forming apparatus according to this embodiment. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure are described below. These descriptions and embodiments are illustrative and do not limit the scope of the embodiments.

[0010] In this disclosure, the numerical range indicated using "~" represents a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples.

[0011] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that their objectives are achieved.

[0012] When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto.

[0013] In this disclosure, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this disclosure, if there are multiple types of the substance corresponding to each component in the composition, it means the total amount of those multiple types of substances present in the composition unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified.

[0014] In this disclosure, alkyl groups include linear, branched, and cyclic types unless otherwise specified.

[0015] In this disclosure, organic groups, aromatic rings, linking groups, alkyl groups, aryl groups, aralkyl groups, alkoxy groups, and aryloxy groups may have hydrogen atoms substituted by halogen atoms.

[0016] <Image Forming Unit> The image forming unit according to this embodiment comprises a photoreceptor and a charging member (a so-called contact-type charging member) that contacts the surface of the photoreceptor and charges the photoreceptor. The charging member has a support member and an elastic layer disposed on the support member. The elastic layer has a storage modulus G' of 5.0 MPa or less at a frequency of 100 Hz in a dynamic viscoelasticity measurement at a temperature of 24°C.

[0017] The image forming unit according to this embodiment includes a first embodiment and a second embodiment.

[0018] The image forming unit according to the first embodiment comprises a photoreceptor comprising a conductive substrate and a stacked photoreceptor layer having a charge generation layer and a charge transport layer disposed on the conductive substrate. The charge transport layer of the photoreceptor according to the first embodiment contains at least one of a polyester resin having a constituent unit having an aromatic ring and a polycarbonate resin having a constituent unit having an aromatic ring. The photoreceptor according to the first embodiment may further include other layers besides the stacked photosensitive layer (for example, an undercoat layer, an intermediate layer). In the photoreceptor according to the first embodiment, it is preferable that the charge transport layer is the surface layer.

[0019] The image forming unit according to the second embodiment comprises a photoreceptor comprising a conductive substrate and a single-layer photoreceptor disposed on the conductive substrate. The single-layer photosensitive layer of the photoreceptor according to the second embodiment contains at least one of a polyester resin having a constituent unit having an aromatic ring and a polycarbonate resin having a constituent unit having an aromatic ring. The photoreceptor according to the second embodiment may further include other layers besides the single-layer photoreceptor (for example, an undercoat layer, an intermediate layer). In the photoreceptor according to the second embodiment, it is preferable that the single-layer photoreceptor is the surface layer.

[0020] Figure 1 is a schematic partial cross-sectional view showing an example of the layer configuration of a photoreceptor according to the first embodiment. The photoreceptor 10A shown in Figure 1 has a stacked photoreceptor layer. The photoreceptor 10A has a structure in which a base layer 2, a charge generation layer 3, and a charge transport layer 4 are stacked in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute the photoreceptor layer 5 (a so-called functionally separated photoreceptor layer). The photoreceptor 10A may have an intermediate layer (not shown) between the base layer 1 and the charge generation layer 3.

[0021] Figure 2 is a schematic partial cross-sectional view showing an example of the layer configuration of a photoreceptor according to the second embodiment. The photoreceptor 10B shown in Figure 2 has a single-layer photosensitive layer. The photoreceptor 10B has a structure in which an undercoat layer 2 and a photosensitive layer 5 are stacked in that order on a conductive substrate 1. The photoreceptor 10B may have an intermediate layer (not shown) between the undercoat layer 1 and the photosensitive layer 5.

[0022] Hereinafter, when describing matters common to the first and second embodiments, both embodiments will be collectively referred to as "this embodiment." When describing matters common to the charge transport layer and the single-layer photosensitive layer, both layers will be collectively referred to as the photosensitive layer. Unless otherwise specified, the value of the storage modulus G' is the value of the storage modulus G' measured at a temperature of 24°C and a frequency of 100 Hz.

[0023] The image forming unit according to this embodiment suppresses excessive wear of the photoreceptor. The mechanism is presumed to be as follows.

[0024] When a polyester resin or polycarbonate resin having a constituent unit with an aromatic ring is used as the binder resin for the photosensitive layer, the amount of discharge required from the charging member to charge the photosensitive layer is reduced because these resins have high dielectric properties. On the other hand, if the storage modulus G' of the elastic layer of the charged material is 5.0 MPa or less, the elastic layer of the charged material is easily deformed when it comes into contact with the photoreceptor. By combining a photoreceptor with the above-described properties and a charged component, localized large-volume discharges are less likely to occur between the photoreceptor and the charged component, and deterioration of the photoreceptor surface is suppressed. As a result, excessive wear of the photoreceptor by the cleaning blade or intermediate transfer material is suppressed.

[0025] In this embodiment, from the viewpoint of suppressing wear of the photoreceptor, the storage modulus G' of the elastic layer of the charging member of the image forming unit is preferably 5.0 MPa or less, preferably 4.0 MPa or less, and more preferably 3.5 MPa or less. In this embodiment, from the viewpoint of improving the contamination resistance of the charged member, the storage modulus G' of the elastic layer of the charged member is preferably 1.0 MPa or higher, more preferably 1.2 MPa or higher, and even more preferably 1.5 MPa or higher.

[0026] In this embodiment, the method for measuring the storage modulus G' of the elastic layer of the charged member is as follows. Prepare an elastic layer, which is the material used to manufacture the charged component, or prepare an elastic layer by peeling it off from the charged component. Cut the elastic layer to a length of 24 mm, a width of 2 mm, and a thickness of 0.5 mm, and use this as a test specimen. Align the longer side of the test specimen with the axial direction of the charged component. Prepare the test specimen at 5 locations in the axial direction of the charged component (i.e., evenly distributed from near one end to near the other end) and 2 locations in the rotational direction, for a total of 10 locations. Using a dynamic viscoelasticity measuring device (RHEOVIBRON, manufactured by Orientec Co., Ltd.), the storage modulus G' was measured under the following conditions: ambient temperature of 24°C, chuck distance of 20 mm, load of 10 gf, amplitude of 80 μm, and automatic sweep from frequency 0.1 Hz to 100 Hz. The storage modulus G' of 10 test specimens at a frequency of 100 Hz was then calculated using the arithmetic mean.

[0027] The following describes in detail the polyester resin having a constituent unit with an aromatic ring, the polycarbonate resin having a constituent unit with an aromatic ring, the photoreceptor, and the electrostatic member.

[0028] [Polyester resin having constituent units with aromatic rings] As the polyester resin having a structural unit with an aromatic ring, a polyester resin (1) having at least a dicarboxylic acid unit (A) and a diol unit (B) is preferable. The polyester resin (1) may contain other dicarboxylic acid units other than the dicarboxylic acid unit (A). The polyester resin (1) may contain other diol units other than the diol unit (B).

[0029] The dicarboxylic acid unit (A) is a structural unit represented by the following formula (A).

[0030]

Chemical formula

[0031] In formula (A), Ar A1 and Ar A2 are each independently an aromatic ring which may have a substituent, L A is a single bond or a divalent linking group, and n A1 is 0, 1 or 2.

[0032] The aromatic ring of Ar A1 may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferable.

[0033] The hydrogen atom on the aromatic ring of Ar A1 may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, etc. When the aromatic ring of Ar A1 is substituted, preferred substituents include an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms.

[0034] The aromatic ring of Ar A2 may be either a monocyclic or polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferable.

[0035] Ar A2 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. A2 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0036] L A When it is a divalent linking group, the divalent linking group can be, for example, an oxygen atom, a sulfur atom, -C(Ra 1 )(Ra 2 )- is one example. Here, Ra 1 and Ra 2 Each of these is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, Ra 1 and Ra 2 These may be bonded together to form a cyclic alkyl group.

[0037] Ra 1 and Ra 2 The alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 or 2.

[0038] Ra 1 and Ra 2 The aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0039] Ra 1 and Ra 2 The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Ra 1 and Ra 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0040] The dicarboxylic acid unit (A) preferably includes at least one selected from the group consisting of a dicarboxylic acid unit (A1) represented by the following formula (A1), a dicarboxylic acid unit (A2) represented by the following formula (A2), a dicarboxylic acid unit (A3) represented by the following formula (A3), and a dicarboxylic acid unit (A4) represented by the following formula (A4).

[0041] [ka]

[0042] In equation (A1), n 101 n is an integer between 0 and 4, and 101 Individual Ra 101 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 101 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0043] [ka]

[0044] In equation (A2), n 201 and n 202 Each of these is an independent integer between 0 and 4, and n 201 Individual Ra 201 and n 202 Individual Ra 202 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 201It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 202 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0045] [ka]

[0046] In equation (A3), n 301 and n 302 Each of these is an independent integer between 0 and 4, and n 301 Individual Ra 301 and n 302 Individual Ra 302 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 301 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. n 302 It is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0047] [ka]

[0048] In equation (A4), n 401 n is an integer between 0 and 6, and 401 Individual Ra 401 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. n 401 It is preferably an integer between 0 and 4, more preferably 0, 1, or 2, and even more preferably 0.

[0049] Ra in equation (A1)101 Ra in equation (A2) 201 and Ra 202 Ra of formula (A3) 301 and Ra 302 Also, Ra in formula (A4) 401 Since the specific form and preferred form are the same, hereinafter, Ra 101 Ra 201 Ra 202 Ra 301 Ra 302 and Ra 401 We will refer to them collectively as "Ra" and explain them accordingly.

[0050] The alkyl group having 1 to 10 carbon atoms related to Ra may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 or 2. Examples of linear alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups. Examples of branched alkyl groups having 3 to 10 carbon atoms include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, and the like. Examples of cyclic alkyl groups having 3 to 10 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl groups, as well as polycyclic alkyl groups (e.g., bicyclic, tricyclic, spirocyclic) formed by linking these monocyclic alkyl groups.

[0051] The aryl group with 6 to 12 carbon atoms related to Ra may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Examples of aryl groups having 6 to 12 carbon atoms include phenyl, biphenyl, 1-naphthyl, and 2-naphthyl groups.

[0052] The alkyl group in the alkoxy group having 1 to 6 carbon atoms related to Ra may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0053] Below are examples of dicarboxylic acid units (A1) (A1-1) to (A1-9). Dicarboxylic acid units (A1) are not limited to these examples.

[0054] [ka]

[0055] Below are examples of dicarboxylic acid units (A2) (A2-1) to (A2-3). Dicarboxylic acid units (A2) are not limited to these examples.

[0056] [ka]

[0057] The following are specific examples of dicarboxylic acid units (A3), namely (A3-1) and (A3-2). However, dicarboxylic acid units (A3) are not limited to these examples.

[0058] [ka]

[0059] Below are examples of dicarboxylic acid units (A4-1) to (A4-3). Dicarboxylic acid units (A4) are not limited to these examples.

[0060] [ka]

[0061] The dicarboxylic acid units (A) are preferably (A1-1), (A1-7), (A2-3), (A3-2), and (A4-3) as shown in the above examples, with (A2-3) being the most preferred.

[0062] The total mass percentage of dicarboxylic acid units (A1) to (A4) in the polyester resin (1) is preferably 15% by mass or more and 60% by mass or less. When the total mass percentage of dicarboxylic acid units (A1) to (A4) is 15% by mass or more, the abrasion resistance of the photosensitive layer is good. From this viewpoint, the total mass percentage of dicarboxylic acid units (A1) to (A4) is more preferably 20% by mass or more, and even more preferably 25% by mass or more. When the total mass percentage of dicarboxylic acid units (A1) to (A4) is 60% by mass or less, peeling of the photosensitive layer can be suppressed. From this viewpoint, the total mass percentage of dicarboxylic acid units (A1) to (A4) is more preferably 55% by mass or less, and even more preferably 50% by mass or less. The dicarboxylic acid units (A1) to (A4) contained in the polyester resin (1) may be one type or two or more types.

[0063] Other dicarboxylic acid units (A) besides dicarboxylic acid units (A1) to (A4) include, for example, aliphatic dicarboxylic acid units (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid), alicyclic dicarboxylic acid units (e.g., cyclohexanedicarboxylic acid), and their lower (e.g., C1 to C5) alkyl ester units. The polyester resin (1) may contain one or more of these dicarboxylic acid units.

[0064] The dicarboxylic acid unit (A) contained in the polyester resin (1) may be one type or two or more types.

[0065] The diol unit (B) is a constituent unit represented by the following formula (B).

[0066] [ka]

[0067] In equation (B), Ar B1 and Ar B2 Each of these is an aromatic ring which may independently have substituents, L B is a single bond, oxygen atom, sulfur atom or -C(Rb 1 )(Rb 2 )- and n B1 Rb is 0, 1, or 2. 1 and Rb 2 Each of these is independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 These may be bonded together to form a cyclic alkyl group.

[0068] Ar B1 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0069] Ar B1 The hydrogen atom on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, etc. Ar B1 When the aromatic ring of Ar is substituted, the substituents are preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms.

[0070] Ar B2 The aromatic ring of Ar may be either a monocyclic ring or a polycyclic ring. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring, with a benzene ring and a naphthalene ring being preferred.

[0071] Ar B2 The hydrogen atom on the aromatic ring of Ar may be substituted with an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, a halogen atom, etc. Ar B2 When the aromatic ring of Ar is substituted, the substituents are preferably an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms.

[0072] Rb 1 and Rb 2 The alkyl group having 1 to 20 carbon atoms related to Rb and Rb may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is preferably 1 to 18, more preferably 1 to 14, and still more preferably 1 to 10.

[0073] Rb 1 and Rb 2 The aryl group having 6 to 12 carbon atoms related to Rb and Rb may be either a monocyclic ring or a polycyclic ring. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6.

[0074] Rb 1 and Rb 2In the aralkyl group having 7 to 20 carbon atoms, the alkyl group may be linear, branched or cyclic. The number of carbon atoms of the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 or 2. Rb 1 and Rb 2 In the aralkyl group having 7 to 20 carbon atoms, the aryl group may be monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, and more preferably 6.

[0075] The diol unit (B) preferably contains at least one selected from the group consisting of a diol unit (B1) represented by the following formula (B1), a diol unit (B2) represented by the following formula (B2), a diol unit (B3) represented by the following formula (B3), a diol unit (B4) represented by the following formula (B4), a diol unit (B5) represented by the following formula (B5), a diol unit (B6) represented by the following formula (B6), a diol unit (B7) represented by the following formula (B7), and a diol unit (B8) represented by the following formula (B8).

[0076]

Chemical formula

[0077] In formula (B1), Rb 101 is a branched alkyl group having 4 to 20 carbon atoms, Rb 201 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, Rb 401 , Rb 501 , Rb 801 and Rb 901 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0078] Rb 101 The number of carbon atoms of the branched alkyl group having 4 to 20 carbon atoms in Rb 101Specific examples thereof include an isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, isohexyl group, sec-hexyl group, tert-hexyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, isooctyl group, sec-octyl group, tert-octyl group, isononyl group, sec-nonyl group, tert-nonyl group, isodecyl group, sec-decyl group, tert-decyl group, isododecyl group, sec-dodecyl group, tert-dodecyl group, tert-tetradecyl group, tert-pentadecyl group, and the like.

[0079]

Chem.

[0080] In formula (B2), Rb 102 is a linear alkyl group having 4 to 20 carbon atoms, Rb 202 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 402 , Rb 502 , Rb 802 and Rb 902 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0081] Rb 102 [[ID=3|0]]The number of carbon atoms of the linear alkyl group having 4 to 20 carbon atoms related to Rb is preferably 4 to 16, more preferably 4 to 12, and still more preferably 4 to 8. Specific examples of Rb 102 include an n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, tridecyl group, n-tetradecyl group, n-pentadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-icosyl group, and the like.

[0082] ]>

Chem.

[0083] In equation (B3), Rb 113 and Rb 213 Each of these is independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, d is an integer between 7 and 15, and Rb 403 , Rb 503 , Rb 803 and Rb 903 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0084] Rb 113 and Rb 213 The number of carbon atoms in the linear alkyl group having 1 to 3 carbon atoms is preferably 1 or 2, and more preferably 1. Specific examples of this group include a methyl group, an ethyl group, and an n-propyl group. Rb 113 and Rb 213 The alkyl group in the alkoxy group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 4 carbon atoms is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Specific examples of the group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy groups. Rb 113 and Rb 213 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0085] [ka]

[0086] In equation (B4), Rb 104 and Rb 204 Each is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 404 , Rb 504 , Rb804 and Rb 904 is each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0087] Rb 104 The alkyl group having 1 to 3 carbon atoms related to Rb may be linear, branched or cyclic. The number of carbon atoms of the alkyl group is preferably 1 or 2, more preferably 1. Rb 104 Specific examples of Rb include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a cyclopropyl group.

[0088]

Chemical formula

[0089] In formula (B5), Ar 105 is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, and Rb 205 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 405 Rb 505 Rb 805 and Rb 905 is each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0090] Ar 105 The aryl group having 6 to 12 carbon atoms related to Ar may be monocyclic or polycyclic. The number of carbon atoms of the aryl group is preferably 6 to 10, more preferably 6. Ar 105 The alkyl group in the aralkyl group having 7 to 20 carbon atoms related to Ar may be linear, branched or cyclic. The number of carbon atoms of the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, still more preferably 1 or 2. Ar 105The aryl group in the aralkyl group having 7 to 20 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6. Examples of aralkyl groups having 7 to 20 carbon atoms include benzyl group, phenylethyl group, phenylpropyl group, 4-phenylbutyl group, phenylpentyl group, phenylhexyl group, phenylheptyl group, phenyloctyl group, phenylnonyl group, naphthylmethyl group, naphthylethyl group, anthratilmethyl group, and phenylcyclopentylmethyl group.

[0091] [ka]

[0092] In equation (B6), Rb 116 and Rb 216 Each of these is independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, e is an integer between 4 and 6, and Rb 406 , Rb 506 , Rb 806 and Rb 906 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0093] Rb 116 and Rb 216 The number of carbon atoms in the linear alkyl group having 1 to 3 carbon atoms is preferably 1 or 2, and more preferably 1. Specific examples of this group include a methyl group, an ethyl group, and an n-propyl group. Rb 116 and Rb 216The alkyl group in the alkoxy group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 4 carbon atoms is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Specific examples of the group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy groups. Rb 116 and Rb 216 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0094] [ka]

[0095] In equation (B7), Rb 407 , Rb 507 , Rb 807 and Rb 907 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0096] [ka]

[0097] In equation (B8), Rb 408 , Rb 508 , Rb 808 and Rb 908 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

[0098] Rb of equation (B1) 201 Rb of formula (B2) 202 Rb in formula (B4) 204 and Rb of formula (B5) 205 Since the specific form and preferred form are the same, hereinafter referred to as Rb 201 , Rb202 , Rb 204 and Rb 205 to "Rb 200 They explain it collectively as "[...]."

[0099] Rb 200 The alkyl group having 1 to 3 carbon atoms may be linear, branched, or cyclic. The alkyl group preferably has 1 or 2 carbon atoms, and more preferably 1 carbon atom. Examples of alkyl groups having 1 to 3 carbon atoms include methyl, ethyl, n-propyl, isopropyl, and cyclopropyl groups.

[0100] Rb of equation (B1) 401 Rb of formula (B2) 402 Rb of formula (B3) 403 Rb in formula (B4) 404 Rb in formula (B5) 405 Rb in formula (B6) 406 Rb in equation (B7) 407 and Rb of formula (B8) 408 Since the specific form and preferred form are the same, hereinafter referred to as Rb 401 , Rb 402 , Rb 403 , Rb 404 , Rb 405 , Rb 406 , Rb 407 and Rb 408 to "Rb 400 They explain it collectively as "[...]."

[0101] Rb 400 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0102] Rb 400 The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0103] Rb 400 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0104] Rb of equation (B1) 501 Rb of formula (B2) 502 Rb of formula (B3) 503 Rb in formula (B4) 504 Rb in formula (B5) 505 Rb in formula (B6) 506 Rb in equation (B7) 507 and Rb of formula (B8) 508 Since the specific form and preferred form are the same, hereinafter referred to as Rb 501 , Rb 502 , Rb 503 , Rb 504 , Rb 505 , Rb 506 , Rb 507 and Rb 508 to "Rb 500 They explain it collectively as "[...]."

[0105] Rb 500 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0106] Rb 500 The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0107] Rb 500 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0108] Rb of equation (B1) 801 Rb of formula (B2)802 Rb of formula (B3) 803 Rb in formula (B4) 804 Rb in formula (B5) 805 Rb in formula (B6) 806 Rb in equation (B7) 807 and Rb of formula (B8) 808 Since the specific form and preferred form are the same, hereinafter referred to as Rb 801 , Rb 802 , Rb 803 , Rb 804 , Rb 805 , Rb 806 , Rb 807 and Rb 808 to "Rb 800 They explain it collectively as "[...]."

[0109] Rb 800 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0110] Rb 800 The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0111] Rb 800 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0112] Rb of equation (B1) 901 Rb of formula (B2) 902 Rb of formula (B3) 903 Rb in formula (B4) 904 Rb in formula (B5) 905 Rb in formula (B6) 906 Rb in equation (B7) 907 and Rb of formula (B8) 908 Since the specific form and preferred form are the same, hereinafter referred to as Rb 901 , Rb 902 , Rb 903 , Rb 904 , Rb 905 , Rb 906 , Rb 907 and Rb 908 to "Rb 900 They explain it collectively as "[...]."

[0113] Rb 900 The alkyl group having 1 to 4 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. Examples of linear alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl groups. Examples of branched alkyl groups having 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl groups. Examples of cyclic alkyl groups having 3 or 4 carbon atoms include the cyclopropyl group and the cyclobutyl group.

[0114] Rb 900 The alkyl group in the alkoxy group having 1 to 6 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the alkoxy group having 1 to 6 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Examples of linear alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, and n-hexyloxy groups. Examples of branched alkoxy groups having 3 to 6 carbon atoms include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, and tert-hexyloxy group. Examples of cyclic alkoxy groups having 3 to 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentyloxy, and cyclohexyloxy groups.

[0115] Rb 900 Examples of halogen atoms involved include fluorine, chlorine, bromine, and iodine atoms.

[0116] The following are specific examples of diol units (B1), specifically (B1-1) to (B1-6). Diol units (B1) are not limited to these examples.

[0117] [ka]

[0118] The following are specific examples of diol units (B2), specifically (B2-1) to (B2-11). Diol units (B2) are not limited to these examples.

[0119] [ka]

[0120] The following are specific examples of diol units (B3), namely (B3-1) to (B3-4). Diol units (B3) are not limited to these examples.

[0121] [ka]

[0122] The following are examples of diol units (B4-1) to (B4-7). Diol units (B4) are not limited to these examples.

[0123] [ka]

[0124] The following are examples of diol units (B5-1) to (B5-6). Diol units (B5) are not limited to these examples.

[0125] [ka]

[0126] The following are specific examples of diol units (B6), namely (B6-1) to (B6-4). Diol units (B6) are not limited to these examples.

[0127] [ka]

[0128] The following are examples of diol units (B7-1) to (B7-3). Diol units (B7) are not limited to these examples.

[0129] [ka]

[0130] The following are specific examples of diol units (B8), namely (B8-1) to (B8-3). Diol units (B8) are not limited to these examples.

[0131] [ka]

[0132] The diol units (B) contained in the polyester resin (1) may be one type or two or more types.

[0133] The mass percentage of diol units (B) in the polyester resin (1) is preferably 25% by mass or more and 80% by mass or less. When the mass percentage of diol units (B) is 25% by mass or more, peeling of the photosensitive layer can be suppressed. From this viewpoint, the mass percentage of diol units (B) is more preferably 30% by mass or more, and even more preferably 35% by mass or more. When the mass percentage of diol units (B) is 80% by mass or less, it is possible to maintain solubility in the coating solution for forming the photosensitive layer and improve abrasion resistance. From this viewpoint, the mass percentage of diol units (B) is more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0134] Other diol units besides diol unit (B) include, for example, aliphatic diol units (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) and alicyclic diol units (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A). The polyester resin (1) may contain one or more of these diol units.

[0135] The ends of the polyester resin (1) may be sealed or modified with an end-capping agent or molecular weight modifier used during manufacturing. Examples of end-capping agents or molecular weight modifiers include monohydric phenols, monohydric acid chlorides, monohydric alcohols, and monohydric carboxylic acids. Examples of monohydric phenols include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-propylphenol, m-propylphenol, p-propylphenol, o-tert-butylphenol, m-tert-butylphenol, p-tert-butylphenol, pentylphenol, hexylphenol, octylphenol, nonylphenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives, o-phenylphenol, m-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 monovalent acid chlorides include monofunctional acid halides such as benzoyl chloride, benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, acetate chloride, butyrate chloride, octic acid chloride, benzoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and their substituted derivatives. Examples of monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenethyl alcohol. Examples of monocarboxylic acids include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0136] The weight-average molecular weight of the polyester resin (1) is preferably 30,000 to 300,000, more preferably 40,000 to 250,000, and even more preferably 50,000 to 200,000. The molecular weight of the polyester resin (1) is the polystyrene-equivalent molecular weight measured by GPC (gel permeation chromatography). Tetrahydrofuran is used as the eluent for GPC.

[0137] Methods for producing polyester resin (1) include interfacial polymerization, solution polymerization, and melt polymerization.

[0138] [Polycarbonate resin having constituent units with aromatic rings] As a polycarbonate resin having a constituent unit having an aromatic ring, a polycarbonate resin (1) having a constituent unit (C) is preferred.

[0139] A constituent unit (C) is a constituent unit represented by the following formula (C).

[0140] [ka]

[0141] In equation (C), Ar C1 and Ar C2 Each of these is an aromatic ring which may independently have substituents, L C is a single bond or a divalent linking group, n C1 It is 0, 1, or 2.

[0142] Ar C1 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0143] Ar C1 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. C1 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0144] Ar C2 The aromatic ring may be monocyclic or polycyclic. Examples of aromatic rings include benzene rings, naphthalene rings, anthracene rings, and phenanthrene rings, with benzene rings and naphthalene rings being preferred.

[0145] Ar C2 The hydrogen atoms on the aromatic ring may be substituted with alkyl groups, aryl groups, aralkyl groups, alkoxy groups, aryloxy groups, halogen atoms, etc. C2 When the aromatic ring is substituted, preferred substituents are alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, and alkoxy groups having 1 to 6 carbon atoms.

[0146] L C When it is a divalent linking group, the divalent linking group can be, for example, an oxygen atom, a sulfur atom, or -C(Rc 1 )(Rc 2 )- is one example. Here, Rc 1 and Rc 2 Each of these is independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rc 1 and Rc 2 These may be bonded together to form a cyclic alkyl group.

[0147] Rc 1 and Rc 2The alkyl group having 1 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 to 18, more preferably 1 to 14, and even more preferably 1 to 10.

[0148] Rc 1 and Rc 2 The aryl group having 6 to 12 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0149] Rc 1 and Rc 2 The alkyl group in the aralkyl group having 7 to 20 carbon atoms may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group in the aralkyl group having 7 to 20 carbon atoms is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2. Rc 1 and Rc 2 The aryl group in the aralkyl group having 7 to 20 carbon atoms may be monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 to 10, and more preferably 6.

[0150] The constituent unit (C) preferably includes at least one selected from the group consisting of the constituent unit (Ca1) represented by the following formula (Ca1), the constituent unit (Ca2) represented by the following formula (Ca2), the constituent unit (Ca3) represented by the following formula (Ca3), the constituent unit (Ca4) represented by the following formula (Ca4), the constituent unit (Cb1) represented by the following formula (Cb1), the constituent unit (Cb2) represented by the following formula (Cb2), the constituent unit (Cb3) represented by the following formula (Cb3), the constituent unit (Cb4) represented by the following formula (Cb4), the constituent unit (Cb5) represented by the following formula (Cb5), the constituent unit (Cb6) represented by the following formula (Cb6), the constituent unit (Cb7) represented by the following formula (Cb7), and the constituent unit (Cb8) represented by the following formula (Cb8).

[0151] [ka]

[0152] In equation (Ca1), n 101 n is an integer between 0 and 4, and 101 Individual Ra 101 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. Ra in equation (Ca1) 101 and n 101 These represent Ra in equation (A1), respectively. 101 and n 101 It is synonymous with the same thing, and its specific form is also the same.

[0153] [ka]

[0154] In equation (Ca2), n 201 and n 202 Each of these is an independent integer between 0 and 4, and n 201 Individual Ra 201 and n 202 Individual Ra 202 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. Ra in equation (Ca2) 201 Ra 202 , n 201 and n 202 These represent Ra in equation (A2), respectively. 201 Ra 202 , n 201 and n 202 It is synonymous with the same thing, and its specific form is also the same.

[0155] [ka]

[0156] In equation (Ca3), n 301 and n 302 Each of these is an independent integer between 0 and 4, and n301 Individual Ra 301 and n 302 Individual Ra 302 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. Ra in equation (Ca3) 301 Ra 302 , n 301 and n 302 These represent Ra in equation (A3), respectively. 301 Ra 302 , n 301 and n 302 It is synonymous with the same thing, and its specific form is also the same.

[0157] [ka]

[0158] In equation (Ca4), n 401 n is an integer between 0 and 6, and 401 Individual Ra 401 Each of these is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. Ra in equation (Ca4) 401 and n 401 These represent Ra in equation (A4), respectively. 401 and n 401 It is synonymous with the same thing, and its specific form is also the same.

[0159] [ka]

[0160] In equation (Cb1), Rb 101 Rb is a branched alkyl group having 4 to 20 carbon atoms. 201 Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 401 , Rb 501 , Rb 801 and Rb 901Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. Rb in equation (Cb1) 101 , Rb 201 , Rb 401 , Rb 501 , Rb 801 and Rb 901 These are Rb in equation (B1), respectively. 101 , Rb 201 , Rb 401 , Rb 501 , Rb 801 and Rb 901 It is synonymous with the same thing, and its specific form is also the same.

[0161] [ka]

[0162] In equation (Cb2), Rb 102 Rb is a linear alkyl group having 4 to 20 carbon atoms. 202 Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 402 , Rb 502 , Rb 802 and Rb 902 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. Rb in equation (Cb2) 102 , Rb 202 , Rb 402 , Rb 502 , Rb 802 and Rb 902 These are Rb in equation (B2), respectively. 102 , Rb 202 , Rb 402 , Rb 502 , Rb 802 and Rb 902 It is synonymous with the same thing, and its specific form is also the same.

[0163] [ka]

[0164] In equation (Cb3), Rb 113 and Rb 213 Each of these is independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, d is an integer between 7 and 15, and Rb 403 , Rb 503 , Rb 803 and Rb 903 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. Rb in equation (Cb3) 113 , Rb 213 d, Rb 403 , Rb 503 , Rb 803 and Rb 903 These are Rb in equation (B3), respectively. 113 , Rb 213 d, Rb 403 , Rb 503 , Rb 803 and Rb 903 It is synonymous with the same thing, and its specific form is also the same.

[0165] [ka]

[0166] In equation (Cb4), Rb 104 and Rb 204 Each is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 404 , Rb 504 , Rb 804 and Rb 904 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. Rb in equation (Cb4) 104 , Rb 204 , Rb 404 , Rb 504 , Rb 804 and Rb 904 These are Rb in equation (B4), respectively.104 , Rb 204 , Rb 404 , Rb 504 , Rb 804 and Rb 904 It is synonymous with the same thing, and its specific form is also the same.

[0167] [ka]

[0168] In equation (Cb5), Ar 105 Rb is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms. 205 Rb is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. 405 , Rb 505 , Rb 805 and Rb 905 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. Ar in equation (Cb5) 105 , Rb 205 , Rb 405 , Rb 505 , Rb 805 and Rb 905 These are the Ar in equation (B5), respectively. 105 , Rb 205 , Rb 405 , Rb 505 , Rb 805 and Rb 905 It is synonymous with the same thing, and its specific form is also the same.

[0169] [ka]

[0170] In equation (Cb6), Rb 116 and Rb 216 Each of these is independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, e is an integer between 4 and 6, and Rb 406 , Rb 506, Rb 806 and Rb 906 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. Rb in equation (Cb6) 116 , Rb 216 , e, Rb 406 , Rb 506 , Rb 806 and Rb 906 These are Rb in equation (B6), respectively. 116 , Rb 216 , e, Rb 406 , Rb 506 , Rb 806 and Rb 906 It is synonymous with the same thing, and its specific form is also the same.

[0171] [ka]

[0172] In equation (Cb7), Rb 407 , Rb 507 , Rb 807 and Rb 907 Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. Rb in equation (Cb7) 407 , Rb 507 , Rb 807 and Rb 907 These are Rb in equation (B7), respectively. 407 , Rb 507 , Rb 807 and Rb 907 It is synonymous with the same thing, and its specific form is also the same.

[0173] [ka]

[0174] In equation (Cb8), Rb 408 , Rb 508 , Rb 808 and Rb 908Each of these is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. Rb in equation (Cb8) 408 , Rb 508 , Rb 808 and Rb 908 These are Rb in equation (B8), respectively. 408 , Rb 508 , Rb 808 and Rb 908 It is synonymous with the same thing, and its specific form is also the same.

[0175] The following are examples of constituent units (Ca1) from (Ca1-1) to (Ca1-9). Constituent units (Ca1) are not limited to these.

[0176] [ka]

[0177] The following are examples of constituent units (Ca2), specifically (Ca2-1) to (Ca2-3). The constituent units (Ca2) are not limited to these.

[0178] [ka]

[0179] The following are examples of constituent units (Ca3), specifically (Ca3-1) to (Ca3-2). The constituent units (Ca3) are not limited to these.

[0180] [ka]

[0181] The following are examples of constituent units (Ca4), specifically (Ca4-1) to (Ca4-3). The constituent units (Ca4) are not limited to these.

[0182] [ka]

[0183] The following are examples of constituent units (Cb1) (Cb1-1) to (Cb1-6). Constituent units (Cb1) are not limited to these.

[0184] [ka]

[0185] The following are examples of constituent units (Cb2-1) to (Cb2-11). Constituent units (Cb2) are not limited to these.

[0186] [ka]

[0187] The following are examples of constituent units (Cb3-1) to (Cb3-4). Constituent units (Cb3) are not limited to these.

[0188] [ka]

[0189] The following are examples of constituent units (Cb4-1) to (Cb4-7). Constituent units (Cb4) are not limited to these.

[0190] [ka]

[0191] The following are examples of constituent units (Cb5-1) to (Cb5-6). Constituent units (Cb5) are not limited to these.

[0192] [ka]

[0193] The following are examples of constituent units (Cb6-1) to (Cb6-4). The constituent units (Cb6) are not limited to these.

[0194] [ka]

[0195] The following are examples of constituent units (Cb7-1) to (Cb7-3). The constituent units (Cb7) are not limited to these.

[0196] [ka]

[0197] The following are examples of constituent units (Cb8-1) to (Cb8-3). The constituent units (Cb8) are not limited to these.

[0198] [ka]

[0199] The constituent units (C) contained in the polycarbonate resin (1) may be of one type or two or more types.

[0200] The polycarbonate resin (1) may have other constituent units besides constituent unit (C). Examples of other constituent units include constituent units derived from aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) and phosgene, and constituent units derived from alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A) and phosgene. The polycarbonate resin (1) may contain one or more of these constituent units.

[0201] The mass percentage of constituent units (C) in the polycarbonate resin (1) is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less.

[0202] The polycarbonate resin (1) preferably contains at least one selected from the group consisting of constituent units (Cb1), (Cb2), (Cb3), (Cb4), (Cb5), (Cb6), (Cb7), and (Cb8) as constituent units (C). The total mass percentage of constituent units (Cb1), (Cb2), (Cb3), (Cb4), (Cb5), (Cb6), (Cb7), and (Cb8) in the polycarbonate resin (1) is preferably 80% by mass or more and 100% by mass or less, more preferably 90% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less.

[0203] The weight-average molecular weight of the polycarbonate resin (1) is preferably 35,000 to 300,000, more preferably 40,000 to 250,000, and even more preferably 50,000 to 200,000. The molecular weight of the polycarbonate resin (1) is the polystyrene-equivalent molecular weight measured by GPC (gel permeation chromatography). Tetrahydrofuran is used as the eluent for GPC.

[0204] Methods for producing polycarbonate resin (1) include interfacial polymerization, solution polymerization, and melt polymerization.

[0205] [Photoreceptor] -Conductive substrate- Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Other examples of conductive substrates include paper, resin films, and belts coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys. Here, "conductive" refers to a volume resistivity of 1 × 10⁻⁶. 13 This refers to a value less than Ωcm.

[0206] When the photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center-line average roughness Ra of 0.04 μm to 0.5 μm in order to suppress interference fringes that occur when irradiated with laser light. When non-interfering light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for a longer lifespan because it suppresses the occurrence of defects due to irregularities on the surface of the conductive substrate.

[0207] Methods for roughening a surface include, for example, wet honing, which involves suspending an abrasive in water and spraying it onto a conductive substrate; centerless grinding, which involves pressing a conductive substrate against a rotating grinding wheel and continuously grinding it; and anodizing.

[0208] One method for roughening the surface is to disperse conductive or semiconductive powder in a resin without roughening the surface of the conductive substrate, to form a layer on the surface of the conductive substrate, and then roughen the surface with the particles dispersed in that layer.

[0209] Anodizing roughening treatment involves forming an oxide film on the surface of a conductive substrate (e.g., aluminum) by anodizing it in an electrolyte solution. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film to block the micropores of the oxide film by volume expansion due to a hydration reaction using pressurized steam or boiling water (metal salts such as nickel may be added), thereby converting it into a more stable hydrated oxide.

[0210] The thickness of the anodic oxide film is preferably, for example, 0.3 μm to 15 μm. When the film thickness is within this range, it tends to exhibit barrier properties against injection and tends to suppress the increase in residual potential due to repeated use.

[0211] The conductive substrate may be treated with an acidic treatment solution or with boehmite. Treatment with an acidic solution is carried out, for example, as follows: First, an acidic solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic solution is, for example, in the range of 10% to 11% by mass for phosphoric acid, 3% to 5% by mass for chromic acid, and 0.5% to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness is preferably 0.3 μm to 15 μm.

[0212] The boehmite treatment is carried out, for example, by immersing the material in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting it with heated steam at 90°C to 120°C for 5 to 60 minutes. The film thickness is preferably 0.1 μm to 5 μm. This can be further treated with anodic oxidation using an electrolyte solution with low film solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0213] -Sublayer- The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0214] As for inorganic particles, for example, powder resistance (volume resistivity) 1 × 10 2 Ωcm or more, 1 × 10 11 Examples include inorganic particles smaller than Ωcm. Among these, suitable inorganic particles having the above-mentioned resistance values ​​include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0215] The specific surface area of ​​inorganic particles using the BET method is, for example, 10 m². 2 A value of 1g or more is preferable. The volume-average particle size of the inorganic particles is preferably between 50 nm and 2000 nm (preferably between 60 nm and 1000 nm).

[0216] The inorganic particle content is preferably 10% by mass or more and 80% by mass or less relative to the binder resin, and more preferably 40% by mass or more and 80% by mass or less.

[0217] The inorganic particles may be surface-treated. Two or more types of inorganic particles with different surface treatments or particle sizes may be mixed and used.

[0218] Examples of surface treatment agents include silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, and surfactants. Silane coupling agents are particularly preferred, and silane coupling agents having an amino group are more preferred.

[0219] 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.

[0220] Silane coupling agents may be used in combination of two or more types. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0221] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry or wet method.

[0222] The amount of surface treatment agent applied is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0223] In this case, it is preferable for the underlayer to contain electron-accepting compounds (acceptor compounds) along with inorganic particles, from the viewpoint of improving the long-term stability of electrical properties and carrier blocking ability.

[0224] Examples of electron-accepting compounds include quinone compounds such as chloranil and bromonil; 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; and diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone; as well as other electron-transporting substances. In particular, compounds having an anthraquinone structure are preferred as electron-accepting compounds. Examples of compounds having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds, and specifically, for example, anthraquinone, alizarin, quinizalin, anthralphine, and purpurin are preferred.

[0225] The electron-accepting compound may be dispersed in the underlayer together with inorganic particles, or it may be present attached to the surface of the inorganic particles.

[0226] Methods for attaching electron-accepting compounds to the surface of inorganic particles include, for example, dry methods or wet methods.

[0227] The dry method involves, for example, adding an electron-accepting compound, either directly or dissolved in an organic solvent, dropwise while stirring inorganic particles with a mixer that has a high shear force, or spraying it with dry air or nitrogen gas, to adhere the electron-accepting compound to the surface of the inorganic particles. When adding or spraying the electron-accepting compound, it is preferable to do so at a temperature below the boiling point of the solvent. After adding or spraying the electron-accepting compound, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained.

[0228] The wet method involves dispersing inorganic particles in a solvent using methods such as stirring, ultrasound, sand milling, attritoring, and ball milling, while adding an electron-accepting compound. After stirring or dispersion, the solvent is removed to adhere the electron-accepting compound to the surface of the inorganic particles. Solvent removal methods include, for example, filtration or distillation. After solvent removal, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained. In the wet method, the water content of the inorganic particles may be removed before adding the electron-accepting compound. Examples of this include removing water while stirring and heating in the solvent, or removing water by azeotrope with the solvent.

[0229] The electron-accepting compound may be applied before or after surface treatment with a surface treatment agent to the inorganic particles, or it may be applied simultaneously with the surface treatment with the surface treatment agent.

[0230] The content of the electron-accepting compound is preferably, for example, 0.01% by mass or more and 20% by mass or less relative to the inorganic particles, and more preferably 0.01% by mass or more and 10% by mass or less.

[0231] Examples of known polymer compounds used as the binder resin for the undercoat include acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, unsaturated polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, alkyd resin, epoxy resin, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Examples of binder resins used in the undercoat include charge-transporting resins having charge-transporting groups, conductive resins (e.g., polyaniline), and the like.

[0232] Among these, a resin insoluble in the coating solvent of the upper layer is preferred as the binder resin used for the undercoat layer. In particular, a resin obtained by the reaction of a curing agent with at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin is preferred. When using two or more of these binder resins in combination, the mixing ratio is set as needed.

[0233] The undercoat may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of known additives include electron-transporting pigments such as polycyclic condensation and azo pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. As mentioned above, silane coupling agents are used for surface treatment of inorganic particles, but they may also be added to the undercoat as additives.

[0234] Examples of silane coupling agents used as additives include vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0235] Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0236] Examples of titanium chelate compounds include tetraisopropyl titanate, tetran-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0237] Examples of aluminum chelating compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0238] These additives may be used individually or as a mixture or polycondensate of multiple compounds.

[0239] The underlayer should ideally have a Vickers hardness of 35 or higher. The surface roughness (ten-point average roughness) of the undercoat layer should be adjusted to between 1 / (4n) (where n is the refractive index of the upper layer) and 1 / 2 of the exposure laser wavelength λ used, in order to suppress moiré patterns. Resin particles may be added to the undercoat to adjust the surface roughness. Examples of resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. The surface of the undercoat may also be polished to adjust the surface roughness. Polishing methods include buffing, sandblasting, wet honing, and grinding.

[0240] The formation of the undercoat is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of an undercoat-forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0241] Solvents for preparing the coating solution for forming the undercoat include known organic solvents such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellsolve, ethyl cellsolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0242] Known methods for dispersing inorganic particles when preparing a coating solution for forming an undercoat include, for example, roll mills, ball mills, vibrating ball mills, attritors, sand mills, colloid mills, and paint shakers.

[0243] Conventional methods for applying the undercoating solution onto a conductive substrate include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0244] The thickness of the undercoat is preferably set to a range of 15 μm or more, and more preferably 20 μm to 50 μm.

[0245] -Middle class- An intermediate layer may be further provided between the undercoat layer and the photosensitive layer. The intermediate layer is, for example, a layer containing a resin. Examples of resins used in the intermediate layer include polymer compounds such as acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, and melamine resin. The intermediate layer may contain an organometallic compound. Examples of organometallic compounds used in the intermediate layer include those containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in these intermediate layers may be used individually, as a mixture of multiple compounds, or as polycondensates.

[0246] Among these, the intermediate layer is preferably a layer containing an organometallic compound that contains zirconium atoms or silicon atoms.

[0247] The formation of the intermediate layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of an intermediate layer-forming coating solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary. Conventional methods such as immersion coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating are used to form the intermediate layer.

[0248] The thickness of the intermediate layer is preferably set to a range of 0.1 μm to 3 μm, for example. The intermediate layer may also be used as a base layer.

[0249] -Charge generation layer- The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Alternatively, the charge generation layer may be a vapor-deposited layer of the charge generation material. A vapor-deposited layer of the charge generation material is suitable when using non-coherent light sources such as LEDs (Light Emitting Diodes) or organic EL (Electro-Luminescence) image arrays.

[0250] Examples of charge-generating materials include azo pigments such as bisazo and trisazo; fused aromatic pigments such as dibromoanthonthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0251] Among these, in order to accommodate laser exposure in the near-infrared region, it is preferable to use a metallic phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material. Specifically, for example, hydroxygallium phthalocyanine disclosed in Japanese Patent Publication No. 5-263007, Japanese Patent Publication No. 5-279591, etc.; chlorogallium phthalocyanine disclosed in Japanese Patent Publication No. 5-98181, etc.; dichlorotin phthalocyanine disclosed in Japanese Patent Publication No. 5-140472, Japanese Patent Publication No. 5-140473, etc.; and titanyl phthalocyanine disclosed in Japanese Patent Publication No. 4-189873, etc. are more preferable.

[0252] On the other hand, in order to accommodate laser exposure in the near-ultraviolet region, preferred charge generating materials include fused aromatic pigments such as dibromoanthonthrone; thioindigo pigments; porphyrazine compounds; zinc oxide; trigonal selenium; and bisazo pigments disclosed in Japanese Patent Publication No. 2004-78147 and Japanese Patent Publication No. 2005-181992.

[0253] Even when using non-coherent light sources such as LEDs and organic EL image arrays with a central emission wavelength between 450 nm and 780 nm, the above charge generating materials may be used. However, from the viewpoint of resolution, when using a thin film of 20 μm or less for the photosensitive layer, the electric field strength in the photosensitive layer becomes high, making it easier for charge reduction due to charge injection from the substrate to occur, resulting in image defects known as black spots. This is particularly noticeable when using charge generating materials that are p-type semiconductors that easily generate dark current, such as trigonal selenium and phthalocyanine pigments.

[0254] In contrast, when n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge generating materials, dark currents are less likely to occur, and image defects called black spots can be suppressed even in thin films. Examples of n-type charge generating materials include, but are not limited to, the compounds (CG-1) to (CG-27) described in paragraphs 0288 to 0291 of Japanese Patent Application Publication No. 2012-155282. n-type is determined using the commonly used time-of-flight method, based on the polarity of the photocurrent that flows. Those that are more likely to carry electrons as carriers than holes are classified as n-type.

[0255] The binder resin used in the charge generation layer can be selected from a wide range of insulating resins, or it may be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (such as polycondensates of bisphenols and aromatic divalent carboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinylpyrrolidone resin. Here, "insulating properties" refer to a volume resistivity of 1 × 10⁻⁶. 13 This refers to a value of Ωcm or greater. These binder resins can be used individually or in combination of two or more types.

[0256] The mixing ratio of the charge-generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass ratio.

[0257] The charge generation layer may also contain other known additives.

[0258] The formation of the charge generation layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of a coating solution for forming a charge generation layer by adding the above components to a solvent, drying the coating film, and heating it as necessary. The charge generation layer may also be formed by vapor deposition of a charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when using fused ring aromatic pigments or perylene pigments as the charge generation material.

[0259] Solvents for preparing the coating solution for forming the charge generation layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellsolve, ethyl cellsolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene. These solvents may be used individually or in mixtures of two or more.

[0260] Methods for dispersing particles (e.g., charge-generating materials) in a coating solution for forming a charge-generating layer include, for example, media dispersers such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, as well as media-less dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include collision methods, which disperse the dispersion by causing liquid-liquid collisions or liquid-wall collisions under high pressure, and penetration methods, which disperse the dispersion by penetrating fine channels under high pressure. During this dispersion, it is effective to set the average particle size of the charge-generating material in the coating solution for forming the charge-generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0261] Conventional methods for applying the charge-generating layer forming coating solution onto the undercoat (or intermediate layer) include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0262] The thickness of the charge generation layer is preferably set to a range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0263] -Charge transport layer- The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may also be a layer containing a polymer charge transport material.

[0264] Examples of charge transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds, which are electron transport compounds. Other examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used individually or in combination of two or more, but are not limited to these.

[0265] Examples of polymeric charge transport materials include known compounds with charge transport properties such as poly-N-vinylcarbazole and polysilane. For example, polyester-based polymeric charge transport materials disclosed in Japanese Patent Publication No. 8-176293 and Japanese Patent Publication No. 8-208820 are preferred. The polymeric charge transport material may be used alone or in combination with a binder resin.

[0266] Examples of charge transport materials or polymeric charge transport materials include polycyclic aromatic compounds, aromatic nitro compounds, aromatic amine compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds (especially triphenylamine compounds), diamine compounds, oxadiazole compounds, carbazole compounds, organic polysilane compounds, pyrazoline compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, cyano compounds, benzofuran compounds, aniline compounds, butadiene compounds, and resins having groups derived from these substances. Specifically, paragraphs 0078-0080 of JP 2021-117377, paragraphs 0046-0048 of JP 2019-035900, paragraphs 0052-0053 of JP 2019-012141, paragraphs 0122-0134 of JP 2021-071565, and paragraph 0078-0080 of JP 2021-015223 Examples of compounds include those described in paragraphs 0101-0110, paragraph 0116 of Japanese Patent Publication No. 2013-097300, paragraphs 0309-0316 of International Publication No. 2019 / 070003, paragraphs 0103-0107 of Japanese Patent Publication No. 2018-159087, and paragraphs 0102-0113 of Japanese Patent Publication No. 2021-148818.

[0267] From the viewpoint of charge mobility, the charge transport material preferably contains at least one compound selected from the group consisting of a compound represented by the following formula (D1) (D1), a compound represented by the following formula (D2) (D2), a compound represented by the following formula (D3) (D3), and a compound represented by the following formula (D4) (D4).

[0268] [ka]

[0269] In equation (D1), Ar T1 Ar T2 and Ar T3 Each is independently an aryl group, -C6H4-C(R T4 )=C(RT5 )(R T6 ) or -C6H4-CH=CH-CH=C(R T7 )(R T8 ) is R T4 , R T5 , R T6 , R T7 and R T8 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T5 and R T6 When it is an aryl group, the aryl groups are -C(R 51 )(R 52 )-and / or-C(R 61 )=C(R 62 )- may be linked by a divalent group. R 51 , R 52 , R 61 and R 62 Each of these is independently either a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0270] The group in formula (D1) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0271] As for compound (D1), from the viewpoint of charge mobility, it is an aryl group or -C6H4-CH=CH-CH=C(R T7 )(R T8 A compound having at least one of the following is preferred, and a compound represented by the following formula (D'1) (D'1) is more preferred.

[0272] [ka]

[0273] In equation (D'1), R T111 , R T112 , R T121 , R T122 , R T131 and R T132Each of these is independently a hydrogen atom, a halogen atom, an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 3 carbon atoms), a phenyl group, or a phenoxy group. Tj1, Tj2, Tj3, Tk1, Tk2, and Tk3 are each independently 0, 1, or 2.

[0274] [ka]

[0275] In equation (D2), R T201 , R T202 , R T211 and R T212 Each of these is independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, and -C(R T21 )=C(R T22 )(R T23 ) or -CH=CH-CH=C(R T24 )(R T25 ) is R T21 , R T22 , R T23 , R T24 and R T25 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T221 and R T222 Each of these is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. Tm1, Tm2, ​​Tn1, and Tn2 are each independently 0, 1, or 2.

[0276] The group in formula (D2) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0277] As for compound (D2), from the viewpoint of charge mobility, it can be an alkyl group, an aryl group, or -CH=CH-CH=C(R T24 )(R T25A compound having at least one -CH=CH-CH=C(R) group is preferred, and is an alkyl group, an aryl group, or -CH=CH-CH=C(R) group. T24 )(R T25 Compounds having two of these are more preferable.

[0278] [ka]

[0279] In equation (D3), R T301 , R T302 , R T311 and R T312 Each of these is independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, and -C(R T31 )=C(R T32 )(R T33 ) or -CH=CH-CH=C(R T34 )(R T35 ) is R T31 , R T32 , R T33 , R T34 and R T35 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T321 , R T322 and R T331 Each of these is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. To1, To2, Tp1, Tp2, Tq1, Tq2, and Tr1 are each independently 0, 1, or 2.

[0280] The group in formula (D3) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0281] [ka]

[0282] In equation (D4), R T401 , R T402 , R T411 and R T412 Each of these is independently a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, and -C(R T41 )=C(R T42 )(R T43 ) or -CH=CH-CH=C(R T44 )(R T45 ) is R T41 , R T42 , R T43 , R T44 and R T45 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group. T421 , R T422 and R T431 Each of these is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 are each independently 0, 1, or 2.

[0283] The group in formula (D4) may be substituted with a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0284] The amount of charge transport material contained in the charge transport layer is preferably 20% by mass or more and 70% by mass or less, relative to the total mass of the charge transport layer.

[0285] The charge transport layer preferably contains at least polyester resin (1) and / or polycarbonate resin (1) as a binder resin. The total proportion of polyester resin (1) and polycarbonate resin (1) in the total amount of binder resin contained in the charge transport 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.

[0286] The charge transport layer may contain binder resins other than polyester resin (1) and polycarbonate resin (1). Examples of other binder resins include polyester resins other than polyester resin (1), polycarbonate resins other than polycarbonate resin (1), methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polysilane, etc. These binder resins may be used individually or in combination of two or more.

[0287] The charge transport layer may also contain other known additives. Examples of additives include antioxidants, leveling agents, defoamers, fillers, and viscosity modifiers.

[0288] The formation of the charge transport layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of a charge transport layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0289] Suitable solvents for preparing the coating solution for forming the charge transport layer include common organic solvents such as aromatic hydrocarbons like benzene, toluene, xylene, and chlorobenzene; ketones like acetone and 2-butanone; halogenated aliphatic hydrocarbons like methylene chloride, chloroform, and ethylene chloride; and cyclic or linear ethers like tetrahydrofuran and ethyl ether. These solvents can be used individually or in mixtures of two or more.

[0290] Conventional methods for applying a charge transport layer forming coating solution onto a charge generation layer include blade coating, wire bar coating, spray coating, immersion coating, bead coating, air knife coating, and curtain coating.

[0291] The average thickness of the charge transport layer is preferably 5 μm to 60 μm, more preferably 10 μm to 55 μm, and even more preferably 15 μm to 50 μm.

[0292] -Single-layer photosensitive layer- A single-layer photosensitive layer (charge generation / charge transport layer) is a layer comprising a charge generation material, a charge transport material, a binder resin, and other additives as needed. These materials are the same as those described for the charge generation layer and the charge transport layer.

[0293] The single-layer photosensitive layer preferably contains at least polyester resin (1) and / or polycarbonate resin (1) as a binder resin. The total proportion of polyester resin (1) and polycarbonate resin (1) in the total amount of binder resin 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.

[0294] In the single-layer photosensitive layer, the content of the charge-generating material is preferably 0.1% to 10% by mass, and more preferably 0.8% to 5% by mass, relative to the total solid content.

[0295] The amount of charge transport material contained in the single-layer photosensitive layer should be between 40% and 60% by mass relative to the total solid content.

[0296] The method for forming a single-layer photosensitive layer is the same as the method for forming a charge generation layer or a charge transport layer.

[0297] The average thickness of the single-layer photosensitive layer is preferably 5 μm to 60 μm, more preferably 10 μm to 55 μm, and even more preferably 15 μm to 50 μm.

[0298] -Protective layer- A protective layer is provided on the photosensitive layer as needed. The protective layer is provided, for example, to prevent chemical changes in the photosensitive layer during electrostatic charging, or to further improve the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a protective layer composed of a cured film (crosslinked film). Examples of such layers include those shown in 1) or 2) below.

[0299] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton within the same molecule (i.e., a layer containing a polymer or crosslinked form of the reactive group-containing charge transport material). 2) A layer composed of a cured film of a composition comprising a non-reactive charge transport material and a non-charge transport material containing reactive groups that does not have a charge transport skeleton but has reactive groups (i.e., a layer comprising a non-reactive charge transport material and a polymer or crosslinked form of the non-charge transport material containing reactive groups).

[0300] The reactive groups in the reactive group-containing charge transport material include chain polymerizable groups, epoxy groups, -OH, -OR [where R represents an alkyl group], -NH2, -SH, -COOH, and -SiR. Q1 3-Qn (OR Q2 ) Qn [However, R Q1 R represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group. Q2 Examples of known reactive groups include hydrogen atoms, alkyl groups, and trialkylsilyl groups. Qn represents an integer from 1 to 3.

[0301] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, for example, a functional group having at least one carbon double bond. Specifically, examples include groups containing at least one selected from vinyl groups, vinyl ether groups, vinyl thioether groups, phenyl vinyl groups, vinyl phenyl groups, acryloyl groups, methacryloyl groups, and their derivatives. Among these, the chain polymerizable group is preferably a group containing at least one selected from vinyl groups, phenyl vinyl groups, vinyl phenyl groups, acryloyl groups, methacryloyl groups, and their derivatives, due to its excellent reactivity.

[0302] The charge-transporting skeleton of the reactive group-containing charge-transporting material is not particularly limited as long as it is a known structure in photoreceptors. For example, a skeleton derived from nitrogen-containing hole-transporting compounds such as triarylamine compounds, benzidine compounds, and hydrazone compounds, in which the nitrogen atom is conjugated, can be cited. Among these, the triarylamine skeleton is preferred.

[0303] These reactive groups and charge-transporting skeletons can be selected from known materials to be used as reactive group-containing charge transport materials, non-reactive charge transport materials, and reactive group-containing non-charge transport materials.

[0304] The protective layer may also contain other known additives.

[0305] The formation of the protective layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of a protective layer-forming coating liquid obtained by adding the above components to a solvent, drying the coating film, and performing a curing treatment such as heating as necessary.

[0306] Solvents for preparing coating solutions for forming a protective layer include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; cellosolve solvents such as ethylene glycol monomethyl ether; and alcohol solvents such as isopropyl alcohol and butanol. These solvents can be used individually or in combination of two or more. The coating solution for forming the protective layer may be a solvent-free coating solution.

[0307] Conventional methods for applying a protective layer-forming coating solution onto a photosensitive layer (e.g., a charge transport layer) include immersion coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating.

[0308] The thickness of the protective layer is set, for example, preferably within the range of 1 μm to 20 μm, and more preferably within the range of 2 μm to 10 μm.

[0309] [Charging component] The charging member may be a charging member that is charged using a method in which only a direct current voltage is applied (DC charging method), a charging member that is charged using a method in which only an alternating current voltage is applied (AC charging method), or a charging member that is charged using a method in which a voltage obtained by superimposing an alternating current voltage on a direct current voltage is applied (AC / DC charging method).

[0310] The charging member contacts the surface of the photoreceptor to charge it. The charging member comprises a support member and an elastic layer provided on the support member. The charging member may further have a surface layer that protects the elastic layer. The charging member may be in the form of a roll or a belt.

[0311] Figure 3 is a schematic perspective view showing an example of a charged member. The charged member 30 shown in Figure 3 has a structure in which an elastic layer 34 and a surface layer 36 are laminated in that order on a support member 32.

[0312] -Support member- The support member is a conductive member that functions as an electrode and support for the charged member. The support member may be a hollow member or a non-hollow member, for example, a rod-shaped, cylindrical, or endless belt-shaped member.

[0313] Support members include metal members such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, and nickel; iron members plated with chromium, nickel, etc.; resin or ceramic members with plated outer surfaces; and resin or ceramic members containing conductive agents.

[0314] -Elastic layer- The elastic layer is conductive and has a volume resistivity of 1 × 10⁻⁶ 3 Ωcm or more, 1 × 10 14 It is preferable that the density is Ωcm or less.

[0315] The elastic layer may be a foamed elastic layer or a non-foamed elastic layer. The elastic layer may be directly placed on the outer surface of the support member, or it may be placed on the outer surface of the support member via an adhesive layer.

[0316] One embodiment of the elastic layer comprises an elastic material, a conductive agent, and other additives. Examples of other additives include fillers, vulcanizing agents, vulcanization accelerators, vulcanization accelerators, softeners, plasticizers, hardening agents, antioxidants, and coupling agents.

[0317] Examples of elastic materials include polyurethane, nitrile rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, epichlorohydrin rubber, epichlorohydrin-ethylene oxide rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, chlorinated polyisoprene, hydrogenated polybutadiene, butyl rubber, silicone rubber, fluororubber, natural rubber, and elastic materials made by mixing these. Among these elastic materials, polyurethane, silicone rubber, nitrile rubber, epichlorohydrin rubber, epichlorohydrin-ethylene oxide rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether rubber, ethylene-propylene-diene rubber, acrylonitrile-butadiene rubber, and elastic materials made by mixing these are preferred.

[0318] Examples of conductive agents include electronic conductive agents and ionic conductive agents. Examples of electronic conductive agents include powders such as carbon black such as furnace black, thermal black, channel black, Ketjen black, acetylene black, and color black; pyrolytic carbon; graphite; metals or alloys such as aluminum, copper, nickel, and stainless steel; metal oxides such as tin oxide, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution, and tin oxide-indium oxide solid solution; and materials whose insulating surfaces have been treated to become conductive. Examples of ionic conductive agents include perchlorates or chlorates such as tetraethylammonium, lauryltrimethylammonium, and benzyltrialkylammonium; and perchlorates or chlorates of alkali metals or alkaline earth metals such as lithium and magnesium. Conductive agents may be used individually or in combination of two or more types.

[0319] The total amount of conductive agent contained in the elastic layer is preferably set based on the volume resistivity of the elastic layer.

[0320] Carbon black is preferred as the conductive agent. The average primary particle size of the carbon black is preferably 1 nm to 500 nm, and more preferably 5 nm to 200 nm. The carbon black content is preferably 0.1 parts by mass to 20 parts by mass, and more preferably 1 part by mass to 10 parts by mass, per 100 parts by mass of the elastic material.

[0321] Examples of fillers include calcium carbonate, silica, and clay minerals. A single filler may be used, or two or more may be used in combination.

[0322] Calcium carbonate is preferred as a filler. The average primary particle size of calcium carbonate is preferably 1 nm to 500 nm, and more preferably 5 nm to 200 nm. The calcium carbonate content is preferably 1 part by mass to 50 parts by mass, and more preferably 10 parts by mass to 40 parts by mass, per 100 parts by mass of elastic material.

[0323] From the viewpoint of controlling the storage modulus G' of the elastic layer to a range of 1.0 MPa to 5.0 MPa, the elastic layer preferably contains an elastic material, carbon black, and calcium carbonate, with the carbon black content being 1 to 10 parts by mass per 100 parts by mass of the elastic material, and the calcium carbonate content being 10 to 40 parts by mass per 100 parts by mass of the elastic material. The mass ratio of carbon black content to calcium carbonate content is preferably carbon black:calcium carbonate = 100:200 to 100:5000, more preferably 100:300 to 100:4000, and even more preferably 100:500 to 100:3000.

[0324] The thickness of the elastic layer is preferably 1 mm to 10 mm, and more preferably 2 mm to 5 mm.

[0325] Methods for forming an elastic layer on a support member include, for example, extruding an elastic layer-forming composition, which is a mixture of an elastic material, a conductive agent, and other additives, and a cylindrical support member together from an extrusion molding machine to form a layer of the elastic layer-forming composition on the outer surface of the support member, and then heating the layer of the elastic layer-forming composition to cause a crosslinking reaction (including vulcanization) to form an elastic layer; and extruding an elastic layer-forming composition, which is a mixture of an elastic material, a conductive agent, and other additives, from an extrusion molding machine onto the outer surface of an endless belt-shaped support member to form a layer of the elastic layer-forming composition on the outer surface of the support member, and then heating the layer of the elastic layer-forming composition to cause a crosslinking reaction (including vulcanization) to form an elastic layer. The support member may have an adhesive layer on its outer surface.

[0326] -Adhesive layer- Examples of adhesive layers interposed between the elastic layer and the support member include resin layers, specifically, resin layers such as polyolefin, acrylic resin, epoxy resin, polyurethane, nitrile rubber, chlorine rubber, vinyl chloride resin, vinyl acetate resin, polyester, phenolic resin, and silicone resin. The adhesive layer may also contain a conductive agent (for example, the aforementioned electronic conductive agent or ionic conductive agent).

[0327] From the viewpoint of adhesion between the elastic layer and the support member, the thickness of the adhesive layer is preferably 1 μm to 80 μm, more preferably 2 μm to 50 μm, and even more preferably 5 μm to 20 μm.

[0328] -Surface layer- If the charged member has a surface layer, the surface layer constitutes the outermost surface of the charged member. The surface layer is conductive and has a volume resistivity of 1 × 10⁻⁶ 5 Ωcm or more, 1 × 10 8 It is preferable that the density is Ωcm or less.

[0329] One embodiment of the surface layer includes a binder resin, a conductive agent, and other additives.

[0330] Examples of binder resins for the surface layer include polyamide, polyimide, polyester, polyethylene, polyurethane, phenolic resin, silicone resin, acrylic resin, melamine resin, epoxy resin, polyvinylidene fluoride, tetrafluoroethylene copolymer, polyvinyl butyral, ethylene-tetrafluoroethylene copolymer, fluororubber, polycarbonate, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, ethylene vinyl acetate copolymer, cellulose, and the like. The binder resin may be used individually or in combination of two or more types.

[0331] The conductive agent included in the surface layer has a volume resistivity of 1 × 10⁻⁶. 9 Conductive particles with a conductivity of Ωcm or less are desirable. Examples of conductive particles include metal oxides such as tin oxide, titanium oxide, and zinc oxide; and carbon black.

[0332] From the viewpoint of excellent dispersibility in the binder resin, the conductive particles contained in the surface layer preferably have a primary particle size of 10 nm to 50 nm.

[0333] The content of conductive particles in the surface layer is preferably 5 to 50 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of the binder resin.

[0334] The surface layer may contain texture-forming particles for the purpose of having fine irregularities on its surface. Preferably, the surface layer contains texture-forming particles with a volume average particle size of 5 μm to 20 μm in amounts of 5 to 30 parts by mass per 100 parts by mass of the binder resin. Preferably, the texture-forming particles are resin particles such as polyamide particles, fluororesin particles, or silicone resin particles.

[0335] The thickness of the surface layer is preferably 1 μm to 20 μm, preferably 2 μm to 15 μm, and more preferably 3 μm to 10 μm.

[0336] One method for forming a surface layer on an elastic layer is to apply a surface layer forming composition, which is a mixture of a binder resin, a conductive agent, and other additives, to the outer surface of the elastic layer to form a layer of the surface layer forming composition, and then to dry the layer of the surface layer forming composition. Examples of methods for applying the surface layer forming composition to the outer surface of the elastic layer include immersion coating, roll coating, blade coating, wire bar coating, spray coating, bead coating, air knife coating, curtain coating, and the like.

[0337] <Image forming apparatus, process cartridge> The image forming apparatus according to this embodiment comprises a photoreceptor, a charging member that charges the surface of the photoreceptor, an electrostatic latent image forming means for forming an electrostatic latent image on the charged surface of the photoreceptor, a developing means for developing the electrostatic latent image formed on the surface of the photoreceptor with a developer containing toner to form a toner image, and a transfer means for transferring the toner image to the surface of a recording medium. The image forming unit according to this embodiment is used as the photoreceptor and the charging member.

[0338] The image forming apparatus according to this embodiment includes known image forming apparatuses such as: an apparatus equipped with fixing means for fixing a toner image transferred to the surface of a recording medium; a direct transfer apparatus that directly transfers a toner image formed on the surface of a photoreceptor to a recording medium; an intermediate transfer apparatus that first transfers a toner image formed on the surface of a photoreceptor to the surface of an intermediate transfer body, and then secondarily transfers the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium; an apparatus equipped with cleaning means for cleaning the surface of the photoreceptor after the transfer of the toner image and before it is charged; an apparatus equipped with static elimination means for irradiating the surface of the photoreceptor with static elimination light to eliminate static charge after the transfer of the toner image and before it is charged; and an apparatus equipped with a photoreceptor heating member for raising the temperature of the photoreceptor and reducing the relative temperature.

[0339] In the case of an intermediate transfer method apparatus, the transfer means may include, for example, an intermediate transfer body on which a toner image is transferred; a primary transfer means for primaryly transferring the toner image formed on the surface of the photoreceptor to the surface of the intermediate transfer body; and a secondary transfer means for secondary transferring the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium.

[0340] The image forming apparatus according to this embodiment may be either a dry developing type image forming apparatus or a wet developing type image forming apparatus (a developing method using a liquid developer).

[0341] In the image forming apparatus according to this embodiment, for example, the portion comprising the photoreceptor may be a cartridge structure (process cartridge) that can be attached to and detached from the image forming apparatus. As the process cartridge, for example, a process cartridge comprising the image forming unit according to this embodiment is preferably used. In addition to the photoreceptor and the charging member, the process cartridge may also comprise at least one selected from the group consisting of, for example, an electrostatic latent image forming means, a developing means, and a transfer means.

[0342] The following is an example of an image forming apparatus according to this embodiment, but it is not limited to this example. The main parts shown in the figure will be described, and the descriptions of other parts will be omitted.

[0343] Figure 4 is a schematic diagram showing an example of an image forming apparatus according to this embodiment. As shown in Figure 4, the image forming apparatus 100 according to this embodiment includes a process cartridge 300 equipped with a photoreceptor 7, an exposure device 9 (an example of electrostatic latent image forming means), a transfer device 40 (primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is positioned to expose the photoreceptor 7 from the opening of the process cartridge 300, and the transfer device 40 is positioned facing the photoreceptor 7 via the intermediate transfer body 50, with a portion of the intermediate transfer body 50 in contact with the photoreceptor 7. Although not shown, there is also a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) correspond to examples of transfer means.

[0344] In Figure 4, the process cartridge 300 integrally supports a photoreceptor 7, a charging device 8 (an example of a charging means equipped with a charging member), a developing device 11 (an example of a developing means), and a cleaning device 13 (an example of a cleaning means) within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is positioned to contact the surface of the photoreceptor 7. The cleaning member may be a conductive or insulating fibrous member, rather than a cleaning blade 131, and may be used alone or in combination with the cleaning blade 131. The image forming unit according to this embodiment is applied as the charging member of the photoreceptor 7 and the charging device 8.

[0345] Figure 4 shows an example of an image forming apparatus equipped with a fibrous member 132 (roll-shaped) for supplying lubricant 14 to the surface of the photoreceptor 7, and a fibrous member 133 (flat brush-shaped) for assisting cleaning. These can be arranged as needed.

[0346] The following describes each component other than the photoreceptor 7 and the charging device 8.

[0347] -Exposure equipment- Examples of exposure devices 9 include optical equipment that exposes the surface of a photoreceptor 7 to a predetermined image using light such as semiconductor laser light, LED light, or liquid crystal shutter light. The wavelength of the light source is within the spectral sensitivity range of the photoreceptor. As for semiconductor lasers, near-infrared lasers with an oscillation wavelength of around 780 nm are the mainstream. However, the wavelength is not limited to this, and lasers with oscillation wavelengths in the 600 nm range or blue lasers with oscillation wavelengths between 400 nm and 450 nm may also be used. Furthermore, for color image formation, surface-emitting laser light sources capable of outputting multiple beams are also effective.

[0348] -Developing equipment- Examples of developing devices 11 include general developing devices that develop by contacting or not contacting the developing agent. There are no particular restrictions on the developing device 11 as long as it has the above-described functions, and it can be selected according to the purpose. For example, known developing devices that have the function of applying a one-component or two-component developing agent to the photoreceptor 7 using a brush, roller, etc. Among these, those that use a developing roller that holds the developing agent on its surface are preferred.

[0349] The developer used in the developing device 11 may be a one-component developer consisting of toner alone, or a two-component developer containing toner and a carrier. Furthermore, the developer may be magnetic or non-magnetic. Known developers can be used.

[0350] -Cleaning device- The cleaning device 13 uses a cleaning blade system equipped with a cleaning blade 131. In addition to the cleaning blade system, a fur brush cleaning system or a developing and cleaning system may also be used.

[0351] -Transfer device- Examples of the transfer device 40 include contact-type transfer chargers using belts, rollers, films, rubber blades, etc., and transfer chargers that are known themselves, such as scorotron transfer chargers and corotron transfer chargers that utilize corona discharge.

[0352] -Intermediate Transcript- As the intermediate transfer body 50, a belt-shaped material (intermediate transfer belt) containing semiconducting polyimide, polyamide-imide, polycarbonate, polyarylate, polyester, rubber, etc. is used. In addition to the belt shape, a drum-shaped intermediate transfer body may also be used.

[0353] Figure 5 is a schematic diagram showing another example of the image forming apparatus according to this embodiment. The image forming apparatus 120 shown in Figure 5 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one photoreceptor is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem type. [Examples]

[0354] The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following explanation, unless otherwise specified, "parts" and "%" refer to mass. In the following descriptions, synthesis, processing, and manufacturing were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0355] <Manufacturing of electrostatic materials> [Charged Roll (1)] -Preparation of support members- A support member with a diameter of 8 mm was obtained by electroless nickel plating on a SUM23L base material and then treating it with hexavalent chromic acid.

[0356] -Formation of the adhesive layer- • Chlorinated polypropylene resin (chlorinated polypropylene resin with maleic anhydride, Supercron 930, manufactured by Nippon Paper Chemical Co., Ltd.): 100 units • Epoxy resin (EP4000, manufactured by ADEKA Corporation): 10 parts • Conductive agent (carbon black, Ketjenblack EC, manufactured by Ketjenblack International): 2.5 parts • Toluene or xylene: Amount to adjust viscosity The above materials were mixed in a ball mill for 1 hour, then brushed onto the surface of the support member to form an adhesive layer 10 μm thick.

[0357] -Formation of the elastic layer- • Epichlorohydrin-ethylene oxide-allyl glycidyl ether rubber (EPION301, manufactured by Osaka Soda Co., Ltd.): 100 units • Carbon black (3030B, manufactured by Mitsubishi Chemical Corporation): 2 parts • Calcium carbonate (Viscoexcel30, manufactured by Shiraishi Calcium Co., Ltd.): 28 parts • Ionic conductive agent (BTEAC, manufactured by Lion Corporation): 1.4 parts • Vulcanizing agent: Sulfur (Parnock®, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.): 1 part • Vulcanization accelerator: Zinc oxide: 1.5 parts • Vulcanization accelerator: Stearic acid (manufactured by NOF Corporation): 1 part The above materials were mixed and kneaded using a tangential pressure kneader, then passed through a strainer to prepare a rubber composition. The rubber composition was kneaded in an open roll and extruded from an extruder together with a support member having an adhesive layer to form a layer of rubber composition on the outer surface of the support member. Then, it was heated in a heating furnace at 170°C for 70 minutes to obtain a conductive elastic layer roll (diameter 12 mm, average thickness of conductive elastic layer 2 mm).

[0358] -Formation of the surface layer- • Binding resin: N-methoxymethylated nylon (product name: Fine Resin FR101, manufactured by Namari Co., Ltd.): 100 units • Conductive agent: Carbon black (volume average particle size 43nm, product name: MONAHRCH1000, manufactured by Cabot): 5 parts • Particles for creating uneven surfaces: Polyamide particles (volume-average particle size 5 μm, product name: Orgasol2001UDNat1, manufactured by Arkema): 25 parts The above materials were mixed, diluted with methanol, and dispersed in a bead mill (bead material: glass, bead diameter: 1.3 mm) at a propeller rotation speed of 2,000 rpm and a dispersion time of 60 minutes to obtain a surface layer forming composition. The surface layer forming composition was applied to the elastic layer of a conductive elastic layer roll by a blade coating method, and then heated and dried at 150°C for 30 minutes to form a surface layer. After that, the ends of the surface layer and the conductive elastic layer were cut off to obtain a charged member.

[0359] [Charging Rolls (2)~(7)] Charging rolls (2) to (7) were manufactured in the same manner as the manufacturing of the charging roll (1), except that the amount of carbon black used, the amount of calcium carbonate used, and the heating conditions in the heating furnace were changed as shown in Table 1 during the formation of the elastic layer.

[0360] [Table 1]

[0361] <Preparation of the photosensitive layer binder resin> [Polyester resin (1)] Polyester resins (PE1) to (PE7) were prepared as polyester resin (1). Tables 2 and 3 show the units and composition of the polyester resins. Tables 2 and 3 show the "composition units:composition ratio" (e.g., A2-3:50). The composition ratio is expressed in mol% for dicarboxylic acid units and diol units, respectively. A2-3, etc., listed in Tables 2 and 3, are specific examples of the dicarboxylic acid unit (A) described above. Tables 2 and 3 show B1-4, etc., which are specific examples of the diol unit (B) described above.

[0362] [Total aliphatic polyester resin] A total aliphatic polyester resin was prepared by condensation polymerization of oxalic acid and cyclohexanedicarboxylic acid.

[0363] [Polycarbonate resin (1)] Polycarbonate resins (PC1) to (PC5) were prepared as polycarbonate resin (1). Table 2 shows the units and composition of the polycarbonate resins. Table 2 shows the "constituent units:composition ratio" (e.g., Cb1-4:50). The composition ratio is expressed in mol% for each constituent unit. Table 2 shows Cb1-4, etc., as specific examples of the constituent unit (C) described above.

[0364] [Total aliphatic polycarbonate resin] A fully aliphatic polycarbonate resin was prepared by reacting ethylene glycol with phosgene.

[0365] <Manufacturing of photoreceptors with stacked photosensitive layers> [Photoconductor S1] -Formation of the lower layer- As a conductive substrate, an aluminum cylindrical tube with an outer diameter of 30 mm, a length of 250 mm, and a wall thickness of 1 mm was prepared.

[0366] Zinc oxide (average particle size 70 nm, specific surface area 15 m²) 2 100 parts of (Teika Co., Ltd.) were mixed with 500 parts of toluene and stirred. 1.3 parts of a silane coupling agent (product name: KBM603, Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) were added and the mixture was stirred for 2 hours. The toluene was then removed by distillation under reduced pressure, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent.

[0367] 110 parts of surface-treated zinc oxide was mixed with 500 parts of tetrahydrofuran by stirring. A solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added, and the mixture was stirred at 50°C for 5 hours. The solids were then filtered off by vacuum filtration, and the mixture was dried under reduced pressure at 60°C to obtain alizarin-treated zinc oxide.

[0368] 60 parts of alizarin-modified zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, trade name: Sumijule 3175, manufactured by Sumitomo Bayern Urethanes), and 15 parts of butyral resin (trade name: Esrec BM-1, manufactured by Sekisui Chemical Co., Ltd.) were dissolved in 68 parts of methyl ethyl ketone. 100 parts of this solution were mixed with 5 parts of methyl ethyl ketone, and the mixture was dispersed for 2 hours using a sand mill with 1 mmφ glass beads to obtain a dispersion. To the dispersion, 0.005 parts of dioctyl tin dilaurate as a catalyst and 4 parts of silicone resin particles (trade name: Tospar 145, manufactured by Momentive Performance Materials) were added to obtain a coating solution for forming the undercoat. The undercoat coating solution was applied to the outer surface of a conductive substrate by immersion coating, and dried and cured at 170°C for 40 minutes to form an undercoat. The average thickness of the undercoat was 25 μm.

[0369] -Formation of a charge generation layer- A mixture consisting of 15 parts of hydroxygallium phthalocyanine as a charge-generating material (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in its X-ray diffraction spectrum using Cukα characteristic X-rays), 10 parts of vinyl chloride / vinyl acetate copolymer resin (product name: VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed for 4 hours using glass beads with a diameter of 1 mm in a sand mill. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion and stirred to obtain a coating solution for forming the charge-generating layer. The coating solution for forming the charge-generating layer was immersed and coated onto the undercoat, and dried at room temperature (25℃±3℃) to form a charge-generating layer with an average thickness of 0.18 μm.

[0370] -Formation of a charge transport layer- A coating solution for forming a charge transport layer was obtained by dissolving 60 parts of polyester resin (PE1) as a binder resin and 40 parts of CTM-1 as a charge transport material in 270 parts of tetrahydrofuran and 30 parts of toluene. The coating solution for forming a charge transport layer was applied to a charge generating layer by immersion, and dried at 145°C for 30 minutes to form a charge transport layer with an average thickness of 40 μm.

[0371] [ka]

[0372] [Photoconductor S2~S16, Photoconductor SC1~SC2] Each photoreceptor was prepared in the same manner as photoreceptor S1, except that the type of polyester resin or polycarbonate resin and the type and amount of charge transport material were changed to the specifications shown in Table 2 during the formation of the charge transport layer. The charge transport materials CTM-2 to CTM-5 are the following compounds.

[0373] [ka]

[0374] <Manufacturing of photoreceptors with a single-layer photosensitive layer> [Photoconductor T1] -Formation of a single-layer photosensitive layer- A single-layer photosensitive coating solution was obtained by mixing 45.75 parts of polyester resin (PE1) as a binder resin, 1.25 parts of V-type hydroxygallium phthalocyanine as a charge generating material (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.3°, 16.0°, 24.9°, and 28.0° in the X-ray diffraction spectrum using Cukα characteristic X-rays), 9 parts of electron transport material ETM-1, 44 parts of charge transport material CTM-1, and 175 parts of tetrahydrofuran and 75 parts of toluene as solvents. The mixture was dispersed using 1 mm diameter glass beads in a sand mill for 4 hours. The obtained photosensitive coating solution was applied by immersion coating onto an aluminum substrate with an outer diameter of 30 mm, a length of 244.5 mm, and a wall thickness of 1 mm. Drying and curing was performed at a temperature of 110°C for 40 minutes to form a single-layer photosensitive layer with an average thickness of 36 μm.

[0375] [ka]

[0376] [Photoconductor T2~T7, Photoconductor TC1] Each photoreceptor was prepared in the same manner as photoreceptor T1, except that the type of polyester resin used in the formation of the single-layer photoreceptor was changed to the specifications shown in Table 3.

[0377] <Manufacturing of image forming units and image forming apparatus> [Examples 1-26, Comparative Examples 1-4] A Fujifilm Business Innovation "DocuCentre-VI C7771" image forming apparatus was prepared, and a photoreceptor equipped with a charged element and a stacked photosensitive layer was combined and loaded into the image forming apparatus as shown in Table 2. The following evaluations were performed on this image forming apparatus.

[0378] [Examples 27-38, Comparative Examples 5-6] A Fujifilm Business Innovation "DocuCentre-VI C7771" image forming apparatus was prepared, and a photoreceptor with a charged element and a single-layer photosensitive layer was combined and loaded into the image forming apparatus as shown in Table 3. The following evaluations were performed on this image forming apparatus.

[0379] <Performance evaluation of image forming apparatus> [Photoreceptor wear resistance] A photoreceptor was mounted in an electrophotographic image forming apparatus (DocuCentre-VI C7771, manufactured by Fujifilm Business Innovation Co., Ltd.), and 100,000 solid black images with 100% image density (area coverage) were formed on A3-sized plain paper under conditions of 24°C and 55% relative humidity. The average thickness of the charge transport layer (or single-layer photosensitive layer) was determined before and after the image formation, and the difference in average thickness before and after image formation was defined as the amount of wear (nm). A Permascope manufactured by Fischerscope was used as the film thickness measuring instrument. The wear amounts were classified as follows. The results are shown in Tables 2 and 3. A: Wear amount is less than 500 nm B: Wear amount is 500 nm or more, but less than 1000 nm C: Wear amount is 1000nm or more, but less than 1500nm D: Wear amount is 1500nm or more, but less than 2000nm E: Wear amount is 2000 nm or more

[0380] [Image quality defects caused by contamination of charged components] A photoreceptor was mounted in a modified electrophotographic image forming machine (Fujifilm Business Innovation Co., Ltd., DocuCentre-VI C7771), and 1000 solid black images with 100% image density (area coverage) were formed on A3-sized plain paper under conditions of 28°C and 85% relative humidity. Subsequently, one black image with 30% full-surface halftone was formed on A3-sized plain paper, and image quality defects (color streaks in the process direction) were visually evaluated. The levels of image quality abnormalities were classified as follows. The results are shown in Tables 2 and 3. A: No abnormalities in image quality. B: A single, slight streak of discoloration has appeared. C: Multiple minor streaks of color appear. D: One severe streak of discoloration has appeared. E: Multiple severe streaks of discoloration have appeared.

[0381] [Table 2]

[0382] [Table 3] [Explanation of symbols]

[0383] 1 Conductive substrate, 2 Undercoat layer, 3 Charge generation layer, 4 Charge transport layer, 5 Photosensitive layer, 10A photoreceptor, 10B photoreceptor

[0384] 30 Charging member, 32 Support member, 34 Elastic layer, 36 Surface layer

[0385] 7 Photoreceptor, 8 Charging device, 9 Exposure device, 11 Developing device, 13 Cleaning device, 14 Lubricant, 40 Transfer device, 50 Intermediate transfer body, 100 Image forming device, 120 Image forming device, 131 Cleaning blade, 132 Fibrous material (roll type), 133 Fibrous material (flat brush type), 300 Process cartridge

Claims

1. Photoreceptor and The system comprises a charging member that contacts the surface of the photoreceptor and charges the photoreceptor, The photoreceptor comprises a conductive substrate and a multilayer photoreceptor having a charge generation layer and a charge transport layer disposed on the conductive substrate. The charge transport layer contains at least one of a polyester resin having a constituent unit having an aromatic ring and a polycarbonate resin having a constituent unit having an aromatic ring. The charging member comprises a support member and an elastic layer disposed on the support member. The elastic layer has a storage modulus G' of 1.0 MPa or more and 3.5 MPa or less in dynamic viscoelasticity measurements at a temperature of 24°C at a frequency of 100 Hz. The polyester resin having the aromatic ring constituent unit comprises a polyester resin (1) having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by the following formula (B). The dicarboxylic acid unit (A) represented by formula (A) includes at least one selected from the group consisting of the dicarboxylic acid unit (A1) represented by the following formula (A1), the dicarboxylic acid unit (A2) represented by the following formula (A2), the dicarboxylic acid unit (A3) represented by the following formula (A3), and the dicarboxylic acid unit (A4) represented by the following formula (A4). The diol unit (B) represented by formula (B) includes at least one selected from the group consisting of the diol unit (B1) represented by the following formula (B1), the diol unit (B2) represented by the following formula (B2), the diol unit (B3) represented by the following formula (B3), the diol unit (B5) represented by the following formula (B5), and the diol unit (B6) represented by the following formula (B6). The polycarbonate resin having the aforementioned aromatic ring-containing structural unit includes a polycarbonate resin (1) having a structural unit (C) represented by the following formula (C), The constituent unit (C) represented by formula (C) includes at least two selected from the group consisting of the constituent unit (Ca2) represented by the following formula (Ca2), the constituent unit (Ca3) represented by the following formula (Ca3), the constituent unit (Cb1) represented by the following formula (Cb1), the constituent unit (Cb2) represented by the following formula (Cb2), and the constituent unit (Cb5) represented by the following formula (Cb5). Image forming unit. 【Chemistry 1】 In formula (A), Ar A1 and Ar A2 are each an aromatic ring which may have substituents, L A is a single bond or a divalent linking group, and n A1 is 0, 1, or 2. In formula (B), Ar B1 and Ar B2 are each independently aromatic rings which may have substituents, L B is a single bond, an oxygen atom, a sulfur atom, or -C(Rb 1)(Rb 2)-, and n B1 is 0, 1, or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may be bonded to form a cyclic alkyl group. 【Chemistry 2】 In formula (A1), n ​​101 is an integer between 0 and 4, and each of the n 101 Ra 101 groups is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A2), n 201 and n 202 are each an independent integer between 0 and 4, and n 201 Ra 201 and n 202 Ra 202 are each an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A3), n 301 and n 302 are each independently integers between 0 and 4, and n 301 Ra 301 and n 302 Ra 302 are each independently alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, or alkoxy groups having 1 to 6 carbon atoms. In formula (A4), n 401 is an integer between 0 and 6, and each of the n 401 Ra 401 groups is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. 【Transformation 3】 【Chemistry 4】 In formula (B1), Rb 101 is a branched alkyl group having 4 to 20 carbon atoms, Rb 201 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 401, Rb 501, Rb 801, and Rb 901 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B2), Rb 102 is a linear alkyl group having 4 to 20 carbon atoms, Rb 202 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 402, Rb 502, Rb 802, and Rb 902 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B3), Rb 113 and Rb 213 are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, d is an integer between 7 and 15, and Rb 403, Rb 503, Rb 803, and Rb 903 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B5), Ar 105 is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, Rb 205 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 405, Rb 505, Rb 805, and Rb 905 are each independently of water It is an elementary atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B6), Rb 116 and Rb 216 are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, e is an integer between 4 and 6, and Rb 406, Rb 506, Rb 806, and Rb 906 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. 【Transformation 5】 In formula (C), Ar C1 and Ar C2 are each an aromatic ring which may have substituents, L C is a single bond or a divalent linking group, and n C1 is 0, 1, or 2. 【Transformation 6】 【Transformation 7】 【Transformation 8】 In formula (Ca2), n 201 and n 202 are each an integer between 0 and 4, and n 201 Ra 201 and n 202 Ra 202 are each an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (Ca3), n 301 and n 302 are each independently integers between 0 and 4, and n 301 Ra 301 and n 302 Ra 302 are each independently alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, or alkoxy groups having 1 to 6 carbon atoms. In formula (Cb1), Rb 101 is a branched alkyl group having 4 to 20 carbon atoms, Rb 201 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 401, Rb 501, Rb 801, and Rb 901 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (Cb2), Rb 102 is a linear alkyl group having 4 to 20 carbon atoms, Rb 202 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 402, Rb 502, Rb 802, and Rb 902 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (Cb5), Ar 105 is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms; Rb 205 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; and Rb 405, Rb 505, Rb 805, and Rb 905 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

2. Photoreceptor and The system comprises a charging member that contacts the surface of the photoreceptor and charges the photoreceptor, The photoreceptor comprises a conductive substrate and a single-layer photoreceptor disposed on the conductive substrate. The aforementioned single-layer photosensitive layer contains a polyester resin having a constituent unit having an aromatic ring, The charging member comprises a support member and an elastic layer disposed on the support member. The elastic layer has a storage modulus G' of 1.0 MPa or more and 3.5 MPa or less in dynamic viscoelasticity measurements at a temperature of 24°C at a frequency of 100 Hz. The polyester resin having the aromatic ring constituent unit comprises a polyester resin (1) having a dicarboxylic acid unit (A) represented by the following formula (A) and a diol unit (B) represented by the following formula (B). The dicarboxylic acid unit (A) represented by formula (A) includes at least one selected from the group consisting of the dicarboxylic acid unit (A1) represented by the following formula (A1), the dicarboxylic acid unit (A2) represented by the following formula (A2), the dicarboxylic acid unit (A3) represented by the following formula (A3), and the dicarboxylic acid unit (A4) represented by the following formula (A4). The diol unit (B) represented by formula (B) includes at least one selected from the group consisting of the diol unit (B1) represented by the following formula (B1), the diol unit (B2) represented by the following formula (B2), the diol unit (B3) represented by the following formula (B3), the diol unit (B5) represented by the following formula (B5), and the diol unit (B6) represented by the following formula (B6). Image forming unit. 【Chemistry 9】 In formula (A), Ar A1 and Ar A2 are each an aromatic ring which may have substituents, L A is a single bond or a divalent linking group, and n A1 is 0, 1, or 2. In formula (B), Ar B1 and Ar B2 are each independently aromatic rings which may have substituents, L B is a single bond, an oxygen atom, a sulfur atom, or -C(Rb 1)(Rb 2)-, and n B1 is 0, 1, or 2. Rb 1 and Rb 2 are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms, and Rb 1 and Rb 2 may be bonded to form a cyclic alkyl group. 【Chemistry 10】 In formula (A1), n ​​101 is an integer between 0 and 4, and each of the n 101 Ra 101 groups is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A2), n 201 and n 202 are each an independent integer between 0 and 4, and n 201 Ra 201 and n 202 Ra 202 are each an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. In formula (A3), n 301 and n 302 are each independently integers between 0 and 4, and n 301 Ra 301 and n 302 Ra 302 are each independently alkyl groups having 1 to 10 carbon atoms, aryl groups having 6 to 12 carbon atoms, or alkoxy groups having 1 to 6 carbon atoms. In formula (A4), n 401 is an integer between 0 and 6, and each of the n 401 Ra 401 groups is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. 【Chemistry 11】 【Chemistry 12】 In formula (B1), Rb 101 is a branched alkyl group having 4 to 20 carbon atoms, Rb 201 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 401, Rb 501, Rb 801, and Rb 901 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B2), Rb 102 is a linear alkyl group having 4 to 20 carbon atoms, Rb 202 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 402, Rb 502, Rb 802, and Rb 902 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B3), Rb 113 and Rb 213 are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, d is an integer between 7 and 15, and Rb 403, Rb 503, Rb 803, and Rb 903 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B5), Ar 105 is an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 20 carbon atoms, Rb 205 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and Rb 405, Rb 505, Rb 805, and Rb 905 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. In formula (B6), Rb 116 and Rb 216 are each independently a hydrogen atom, a linear alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, e is an integer between 4 and 6, and Rb 406, Rb 506, Rb 806, and Rb 906 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom.

3. The image forming unit according to claim 1 or claim 2, wherein the elastic layer of the charging member has a storage modulus G' of 1.2 MPa or more and 3.5 MPa or less.

4. The image forming unit according to any one of claims 1 to 3, wherein the elastic layer of the charging member has a storage modulus G' of 1.5 MPa or more and 3.5 MPa or less.

5. The image forming unit according to any one of claims 1 to 4, wherein the elastic layer of the charging member contains an elastic material, carbon black, and calcium carbonate, and contains 1 to 10 parts by mass of carbon black and 10 to 40 parts by mass of calcium carbonate per 100 parts by mass of the elastic material.

6. The dicarboxylic acid unit (A) represented by formula (A) includes the dicarboxylic acid unit (A2) represented by formula (A2), The diol unit (B) represented by formula (B) includes the diol unit (B1) represented by formula (B1), The constituent unit (C) represented by formula (C) includes the constituent unit (Ca2) represented by formula (Ca2) and the constituent unit (Cb1) represented by formula (Cb1). The image forming unit according to claim 1.

7. The dicarboxylic acid unit (A) represented by formula (A) includes the dicarboxylic acid unit (A2) represented by formula (A2), The diol unit (B) represented by formula (B) includes the diol unit (B1) represented by formula (B1), The image forming unit according to claim 2.

8. The image forming unit comprises the image forming unit according to any one of claims 1 to 7, A process cartridge that is attached to and detached from an image forming apparatus.

9. An image forming unit according to any one of claims 1 to 7, An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged photoreceptor, A developing means that develops the electrostatic latent image formed on the surface of the photoreceptor with a developer containing toner to form a toner image, A transfer means for transferring the toner image onto the surface of a recording medium, An image forming apparatus equipped with the following features.

Images