Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

An electrophotographic photoreceptor, a process cartridge, and an image forming apparatus, the electrophotographic photoreceptor including a conductive substrate and a photosensitive layer disposed on the conductive substrate, the outermost layer containing first and second resins, a charge transporting material, and an antioxidant, at least one of the first resin and the second resin has a structural unit including biphenyl represented by formula (BPa), and at least one of the charge transport material and the antioxidant has, in the molecule, at least one of biphenyl represented by formula (BPa) and biphenyl represented by formula (BPb). When the number of biphenyl per unit molecular weight of each of the first resin, the second resin, the charge transport material, and the antioxidant is defined as BP1, BP2, BP3, and BP4, and the proportion of each of the biphenyl per unit molecular weight of each of the first resin, the second resin, the charge transport material, and the antioxidant is defined as MP1, MP2, MP3, and MP4, the relationship 0.0 < = (BP1 * MP1 + BP2 * MP2) / (BP3 * MP3 + BP4 * MP4) < = 3.0 is satisfied. [Chemical Formula 1] Formula (BPa) Formula (BPb)

Description

Technical Field

[0001] This invention relates to an electrophotographic photosensitive element, a processing cartridge, and an image forming apparatus. Background Technology

[0002] Patent Document 1 discloses an electrophotographic photosensitive material, which contains a polyester resin having a biphenyl structure as a repeating unit in the photosensitive layer.

[0003] Patent Document 2 discloses a photoreceptor containing at least one of a polyester resin having a charge transport layer having a structural unit holding an aromatic ring and a polycarbonate resin having a structural unit holding an aromatic ring.

[0004] Patent document 3 discloses an electrophotographic photosensitive material, wherein the charge transport layer contains a charge transport material, a polyester resin having a specified aromatic structure, and a polycarbonate resin.

[0005] Patent document 4 discloses a cleaning scraper, wherein the contact portion that contacts the part being cleaned contains a polyurethane rubber polymerized from a polyol component and a polyisocyanate component, and the ratio of 100% modulus M100 (MPa) to resilience modulus Re (%) M100 / Re is 0.25 or more, the resilience modulus Re is less than 25%, and the tensile stress at 200% strain is 15 MPa or more.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2001-265021

[0007] Patent Document 2: Japanese Patent Application Publication No. 2023-121553

[0008] Patent Document 3: Japanese Patent Application Publication No. 2024-011918

[0009] Patent Document 4: Japanese Patent Application Publication No. 2023-106209 Summary of the Invention

[0010] The objective of this invention is to provide an electrophotographic photosensitive material that is less prone to ghosting and uneven density in images.

[0011] Specific means for solving the aforementioned problem include the following methods. The formulas are the same as those numbered the same as those described below.

[0012] <1> An electrophotographic photosensitive material comprising a conductive substrate and a photosensitive layer disposed on the conductive substrate, wherein,

[0013] The outermost layer contains a first resin, a second resin, a charge transport material, and an antioxidant.

[0014] At least one of the first resin and the second resin has a structural unit comprising biphenyl represented by the following formula (BPa).

[0015] At least one of the charge transport material and the antioxidant has at least one of the following formulas: biphenyl represented by formula (BPa) and biphenyl represented by formula (BPb).

[0016] When the number of biphenyl molecules per unit molecular weight of the first resin, the second resin, the charge transport material, and the antioxidant is set as BP1, BP2, BP3, and BP4, and the respective proportions (mass%) of the first resin, the second resin, the charge transport material, and the antioxidant in the total amount are set as MP1, MP2, MP3, and MP4,

[0017] The relationship satisfies 0.0≤(BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4)≤3.0.

[0018] <2> According to the electrophotographic photosensitive material described in <1>, wherein,

[0019] The relationship satisfies 0.5≤(BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4)≤2.5.

[0020] <3> According to <1> or <2>, the electrophotographic photosensitive material, wherein,

[0021] The antioxidant contains hindered phenolic compounds.

[0022] <4> The electrophotographic photosensitive material according to any one of <1> to <3>, wherein,

[0023] The first resin is a polyarylate resin, and the second resin is a polycarbonate resin.

[0024] <5> According to the electrophotographic photosensitive material described in <4>, wherein,

[0025] The proportion of polyaryl ester resin in the total amount of polyaryl ester resin and polycarbonate resin contained in the outermost surface layer is more than 25% by mass and less than 75% by mass.

[0026] <6> According to <4> or <5>, the electrophotographic photosensitive material, wherein,

[0027] The polyaryl ester resin has 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), a dicarboxylic acid unit (A4) represented by formula (A4), and a dicarboxylic acid unit (A5) represented by formula (A5).

[0028] <7> The electrophotographic photosensitive material according to any one of <4> to <6>, wherein,

[0029] The polyaryl ester resin has at least one selected from the group consisting of a diol unit (B1) represented by formula (B1), a diol unit (B2) represented by formula (B2), a diol unit (B3) represented by formula (B3), a diol unit (B4) represented by formula (B4), a diol unit (B5) represented by formula (B5), a diol unit (B6) represented by formula (B6), a diol unit (B7) represented by formula (B7), and a diol unit (B8) represented by formula (B8).

[0030] <8> The electrophotographic photosensitive material according to any one of <1> to <7>, wherein,

[0031] The photosensitive layer has a charge generation layer and a charge transport layer, wherein the charge transport layer is the outermost layer.

[0032] <9> A processing box comprising the electrophotographic photosensitive element as described in any one of <1> to <8>,

[0033] The processing box is mounted and dismounted from the image forming apparatus.

[0034] <10> An image forming apparatus comprising:

[0035] Electrophotographic photosensitive material as described in any one of <1> to <8>;

[0036] A charging device is used to charge the surface of the electrophotographic photosensitive element.

[0037] An electrostatic latent image forming apparatus forms an electrostatic latent image on the surface of the charged electrophotographic photoreceptor;

[0038] A developing apparatus that develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor using a developing agent containing a toner to form a toner image; and

[0039] A transfer device transfers the toner image onto the surface of a recording medium.

[0040] <11> The image forming apparatus according to <10> further comprises:

[0041] A cleaning device having a cleaning scraper that contacts the surface of the electrophotographic photosensitive element and cleans the surface of the electrophotographic photosensitive element.

[0042] <12> The image forming apparatus according to <11>, wherein,

[0043] The contact portion of the cleaning scraper that contacts the electrophotographic photosensitive element is composed of the following components: a polyurethane rubber containing at least a polyol component and a polyisocyanate component polymerized together, wherein the ratio of 100% modulus M100 (MPa) to resilience modulus Re (%) M100 / Re is 0.25 or more, the resilience modulus Re is less than 25%, and the tensile stress at 200% strain is 15 MPa or more.

[0044] <13> The image forming apparatus according to <12>, wherein,

[0045] The ratio M100 / Re is 0.28 or higher and 1.0 or lower.

[0046] Invention Effects

[0047] According to <1>, <3>, <4>, <5>, <6>, <7> or <8>, an electrophotographic photoreceptor is provided that is less prone to ghosting and uneven density in images compared to electrophotographic photoreceptors with a value of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) exceeding 3.0.

[0048] According to <2>, an electrophotographic photoreceptor is provided that is less prone to ghosting and uneven density in images compared to an electrophotographic photoreceptor with a value of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) less than 0.5 or greater than 2.5.

[0049] According to <9>, a method is provided for (BP1×MP1+BP2×MP2) / of an electrophotographic photosensitive element.

[0050] Compared to cases where the value of (BP3×MP3+BP4×MP4) exceeds 3.0, processing boxes that are less prone to ghosting and uneven density in the image are less likely to produce such issues.

[0051] According to <10> or <11>, a (BP1×MP1+BP2×MP2) / method is provided for use with an electrophotographic photosensitive element.

[0052] Compared to image forming apparatuses where the value of (BP3×MP3+BP4×MP4) exceeds 3.0, this apparatus is less prone to producing ghosting and uneven density in images.

[0053] According to <12>, an image forming apparatus is provided that is less prone to ghosting and uneven density in images compared to an image forming apparatus with a ratio M100 / Re of less than 0.25, a spring modulus Re of more than 25%, or a tensile stress of less than 15 MPa.

[0054] According to <13>, an image forming apparatus is provided in which the ratio M100 / Re to the cleaning squeegee is less than 0.28 or greater than 1.0, and the image forming apparatus is less prone to ghosting and uneven density in the image. Attached Figure Description

[0055] The embodiments of the present invention will be described in detail with reference to the following figures.

[0056] Figure 1 This is a partial cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor according to the first embodiment;

[0057] Figure 2 This is a partial cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor according to the second embodiment;

[0058] Figure 3 This is a schematic structural diagram illustrating an example of the image forming apparatus according to this embodiment;

[0059] Figure 4 This is a schematic structural diagram showing another example of the image forming apparatus according to this embodiment;

[0060] Figure 5 This is a schematic structural diagram showing an example of the cleaning scraper in this embodiment;

[0061] Figure 6 This is a schematic structural diagram showing another example of the cleaning scraper in this embodiment;

[0062] Figure 7 This is a schematic structural diagram showing another example of the cleaning scraper in this embodiment.

[0063] Symbol Explanation

[0064] 1-Conductive substrate, 2-Undercoat layer, 3-Charge generation layer, 4-Charge transport layer, 5-Photosensitive layer, 10A-Photoreceptor, 10B-Photoreceptor.

[0065] 7-Electrophotographic photosensitive element, 8-Electrified 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 scraper, 132-Fiber-like component (roller-like), 133-Fiber-like component (flat brush-like), 300-Processing box.

[0066] 342A, 342B, 342C - Cleaning scraper, 3421B - First layer, 3422B - Second layer, 3421C - Contact component, 3422C - Back component, 31 - Photosensitive element. Detailed Implementation

[0067] The embodiments of the present invention will be described below. These descriptions and examples are illustrative and do not limit the scope of the embodiments.

[0068] In this invention, the numerical range represented by “~” indicates the range included by taking the values ​​recorded before and after “~” as the minimum and maximum values, respectively.

[0069] Within the numerical ranges described in stages in this invention, the upper or lower limit value described as a numerical range can be replaced with the upper or lower limit value of other numerical ranges described in stages. Furthermore, within the numerical ranges described in this invention, the upper or lower limit value of that numerical range can also be replaced with the values ​​shown in the embodiments.

[0070] In this invention, "A and / or B" has the same definition as "at least one of A and B". That is, "A and / or B" means that it can be only A, only B, or a combination of A and B.

[0071] In this invention, the term "process" is included not only in independent processes, but also in cases where it is impossible to clearly distinguish it from other processes, as long as the purpose of the process can be achieved.

[0072] In this invention, when describing embodiments with reference to the accompanying drawings, the structure of the embodiments is not limited to the structure shown in the drawings. Furthermore, the sizes of the components in the figures are conceptual, and the relative sizes of the components are not limited thereto.

[0073] In this invention, each component may also contain multiple corresponding substances. In this invention, when referring to the amount of each component in the composition, if multiple substances corresponding to each component are present in the composition, unless otherwise specified, it indicates the total amount of the multiple substances present in the composition.

[0074] In this invention, a variety of particles corresponding to each component may be included. When a variety of particles corresponding to each component are present in the composition, unless otherwise specified, the particle size of each component refers to the value for the mixture of the various particles present in the composition.

[0075] In this invention, unless otherwise specified, alkyl and alkylene groups include straight-chain, branched, and cyclic forms.

[0076] In this invention, regarding organic groups, aromatic rings, linking groups, alkyl groups, alkylene groups, aryl groups, aralkyl groups, alkoxy groups, aryl groups, etc., the hydrogen atoms in the groups can be replaced by halogen atoms.

[0077] In this invention, when a compound is represented by a structural formula, it is sometimes represented by a structural formula in which the symbols (C and H) representing the hydrocarbon group and / or the carbon and hydrogen atoms in the hydrocarbon chain are omitted.

[0078] In this invention, the “structural unit” of a copolymer or resin has the same meaning as the monomer unit.

[0079] <Electronic Photoreceptor>

[0080] The electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") according to this embodiment includes a conductive substrate and a photosensitive layer disposed on the conductive substrate.

[0081] In one embodiment of the photoreceptor, there is a stacked photoreceptor layer having a charge generation layer and a charge transport layer stacked on top of each other, the charge transport layer being the outermost layer and constituting the outer peripheral surface of the photoreceptor.

[0082] In another embodiment of the photoreceptor, a single-layer photosensitive layer is provided, which is the outermost layer and constitutes the outer peripheral surface of the photoreceptor.

[0083] Figure 1 This is a partial cross-sectional view that schematically illustrates an example of the layer structure of the photoreceptor involved in this embodiment. Figure 1 The photoreceptor 10A shown has a stacked photosensitive layer. The photoreceptor 10A has a structure in which a lower coating layer 2, a charge generation layer 3, and a charge transport layer 4 are sequentially stacked on a conductive substrate 1. The charge generation layer 3 and the charge transport layer 4 constitute the photosensitive layer 5 (a so-called functionally separated photosensitive layer). The photoreceptor 10A may have an intermediate layer (not shown) between the lower coating layer 2 and the charge generation layer 3. The lower coating layer 2 may or may not be present.

[0084] Figure 2 This is a partial cross-sectional view that schematically illustrates another example of the layer structure of the photoreceptor involved in this embodiment. Figure 2 The photoreceptor 10B shown has a single-layer photosensitive layer. The photoreceptor 10B has a structure in which a lower coating layer 2 and a photosensitive layer 5 are sequentially stacked on a conductive substrate 1. The photoreceptor 10B may have an intermediate layer (not shown) between the lower coating layer 2 and the photosensitive layer 5. The lower coating layer 2 may or may not be present.

[0085] In the photoreceptor of this embodiment, the outermost layer contains a first resin, a second resin, a charge transport material, and an antioxidant.

[0086] At least one of the first resin and the second resin has a biphenyl structural unit represented by the formula (BPa).

[0087] At least one of the charge transport materials and antioxidants has at least one of the biphenyl represented by formula (BPa) and biphenyl represented by formula (BPb) within its molecule.

[0088] Let BP1 be the number of biphenyls represented by formula (BPa) per unit molecular weight of the first resin.

[0089] Let BP2 be the number of biphenyl molecules represented by formula (BPa) per unit molecular weight of the second resin.

[0090] Let BP3 be the number of biphenyls represented by formula (BPa) and formula (BPb) per unit molecular weight of the charge transport material.

[0091] Let BP4 be the number of biphenyl molecules represented by formula (BPa) and formula (BPb) per unit molecular weight of the antioxidant.

[0092] When the respective proportions (mass%) of the first resin, second resin, charge transport material, and antioxidant in the total amount are set as MP1, MP2, MP3, and MP4,

[0093] The relationship satisfies 0.0≤(BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4)≤3.0.

[0094] [Chemical Formula 1]

[0095]

[0096] In the formula (BPa), j is an integer greater than or equal to 0 and less than or equal to 4, and j are R... 1 Each is independently methyl or ethyl, k is an integer greater than or equal to 0 and less than or equal to 4, and k R's are independent of each other. 2 Each methyl group can be independently methyl or ethyl. Multiple methyl groups and / or ethyl groups can bond together to form a ring.

[0097] In the formula (BPb), m is an integer greater than or equal to 0 and less than or equal to 4, and m are R's. 3 Each is independently methyl or ethyl, n is an integer greater than or less than 5, and n R 4 Each methyl group can be independently methyl or ethyl. Multiple methyl groups and / or ethyl groups can bond together to form a ring.

[0098] The first resin and the second resin are the two resins present in the outermost layer, with the highest content based on a mass standard. The outermost layer may also contain a different type of resin than the first resin and the second resin.

[0099] The number of biphenyls per unit molecular weight, either BP1 or BP2, can be 0 (zero). The number of biphenyls per unit molecular weight, either BP3 or BP4, can be 0 (zero).

[0100] The photoreceptor involved in this embodiment is less prone to ghosting and uneven density in images. The mechanism is speculated below.

[0101] To manufacture a photosensitive material with balanced properties such as wear resistance, crack resistance, oxidation resistance, and electrical properties, it is effective to use at least two types of adhesive resins in the outermost layer and to add an antioxidant. This outermost layer is also preferred from the viewpoint that it prevents charge retention and reduces ghosting in images. However, to prevent the outermost layer from becoming a cause of uneven concentration, it is required that the first resin, second resin, charge transport material, and antioxidant contained in the outermost layer be highly uniformly mixed. The inventors have discovered that the value of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) related to the four-component biphenyl structure serves as an indicator of the degree of mixing of the four components.

[0102] If the value of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) exceeds 3.0, uneven density is likely to occur in the image. From the viewpoint of suppressing uneven density in the image, the value of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) is 3.0 or less, preferably 2.5 or less, more preferably 2.3 or less, and even more preferably 2.1 or less.

[0103] The lower limit of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) is 0.0 or more. Even if at least one of the first resin and the second resin has a biphenyl structural unit represented by formula (BPa), the value of the above formula will be 0.0 when the amount of biphenyl is small. (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) is preferably 0.5 or more, more preferably 0.8 or more, and even more preferably 1.2 or more.

[0104] The number of biphenyl molecules per unit molecular weight (BP1, BP2, BP3, and BP4) was determined by NMR (nuclear magnetic resonance analysis). The number of molecules was calculated from the peak surface area of ​​the biphenyl structure, and then the number per unit molecular weight was determined. The molecular weight of each component is a chemical formula estimated based on NMR-based structural analysis. For resins, the chemical formula is based on the type and proportion of structural units.

[0105] The samples used for NMR are the materials that form the outermost layer, i.e., the components or the components taken from the outermost layer.

[0106] In the formula (BPa), j is an integer greater than or equal to 0 and less than or equal to 4, and j are R... 1 Each is independently methyl or ethyl, k is an integer greater than or equal to 0 and less than or equal to 4, and k R's are independent of each other. 2 Each can be methyl or ethyl, independently.

[0107] j is an integer greater than or equal to 0 and less than 4, preferably an integer greater than or equal to 0 and less than 3, more preferably an integer greater than or equal to 0 and less than 2, further preferably 0 or 1, and especially preferably 0.

[0108] When j is an integer greater than or equal to 1, j R 1 Each is independently methyl or ethyl, for example preferably methyl.

[0109] k is an integer greater than or equal to 0 and less than 4, preferably an integer greater than or equal to 0 and less than 3, more preferably an integer greater than or equal to 0 and less than 2, further preferably 0 or 1, and especially preferably 0.

[0110] When k is an integer greater than or equal to 1, k R 2 Each is independently methyl or ethyl, for example preferably methyl.

[0111] When a polyaryl ester resin or polycarbonate resin contains biphenyl represented by formula (BPa) in its resin molecule, the biphenyl represented by formula (BPa) can be the entire structure containing the biphenyl represented by formula (BPa) with the ester bond (-C(=O)O-) or carbonate bond (-OC(=O)O-) removed, or it can be a part of the structure. In other words, the right and left ends of the biphenyl represented by formula (BPa) can be directly bonded to the ester bond or carbonate bond independently, or they can be bonded to the ester bond or carbonate bond via other atoms or groups.

[0112] The biphenyl represented by formula (BP) is preferably linked at a 4,4'-biphenyl position in the main chain.

[0113] In the formula (BPb), m is an integer greater than or equal to 0 and less than or equal to 4, and m are R's. 3 Each is independently methyl or ethyl, n is an integer greater than or less than 5, and n R 4 Each can be methyl or ethyl, independently.

[0114] m is an integer greater than or equal to 0 and less than 4, preferably an integer greater than or equal to 0 and less than 3, more preferably an integer greater than or equal to 0 and less than 2, further preferably 0 or 1, and especially preferably 0.

[0115] When m is an integer greater than or equal to 1, there are m R's. 3 Each is independently methyl or ethyl, for example preferably methyl.

[0116] n is an integer greater than or equal to 0 and less than 4, preferably an integer greater than or equal to 0 and less than 3, more preferably an integer greater than or equal to 0 and less than 2, further preferably 0 or 1, and especially preferably 0.

[0117] When n is an integer greater than or equal to 1, n R 4 Each is independently methyl or ethyl, for example preferably methyl.

[0118] [Outermost layer]

[0119] The outermost layer of the photoreceptor contains at least a charge transport material, a first resin, a second resin, and an antioxidant.

[0120] As the charge transport material contained in the outermost layer, examples include compounds that are the same as those contained in the charge transport layers described later, and preferably the same compounds.

[0121] Examples of the first and second resins include polyarylate resins, polycarbonate resins, polyester resins other than polyarylate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenolic-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, and polysilanes. The first and second resins can be any combination of these resins.

[0122] The outermost layer may also contain a different type of resin than the first resin and the second resin. The first resin and the second resin are two resins whose content based on mass is the highest among the resins contained in the outermost layer. The total amount of the first resin and the second resin is preferably 80% or more by mass of the resin contained in the outermost layer, more preferably 90% or more by mass, even more preferably 95% or more by mass, and may also be 100% by mass.

[0123] From the viewpoint of wear resistance, the resin contained in the outermost layer preferably includes at least one of polyaryl ester resin and polycarbonate resin, with the first resin being polyaryl ester resin and the second resin being polycarbonate resin. The form in which the polyaryl ester resin and polycarbonate resin are contained is also preferred, for example, from the viewpoint of forming a fine phase-separated structure in the outermost layer.

[0124] When the first resin is a polyaryl ester resin and the second resin is a polycarbonate resin, from the viewpoint of forming a fine phase separation structure in the outermost layer, the proportion of the polyaryl ester resin in the total amount of the two resins contained in the outermost layer is preferably 20% by mass or more and 80% by mass or less, more preferably 25% by mass or more and 75% by mass or less, and even more preferably 30% by mass or more and 70% by mass or less.

[0125] Polyaryl ester resins improve the wear resistance of the outermost layer by stacking aromatic rings, which bind the resin molecules together through intermolecular forces. For example, condensation polymers of bisphenols and aromatic dicarboxylic acids are preferred as polyaryl ester resins. Examples of polyaryl ester resin forms include polyaryl ester resins (PA) described later.

[0126] As a polycarbonate resin, a polycarbonate resin having a continuous structure of aromatic rings is preferred, for example. This polycarbonate resin, through the stacking of aromatic rings, allows resin molecules to be bonded together by intermolecular forces, thereby improving the wear resistance of the outermost layer. For example, as a preferred form of polycarbonate resin, specifically, the polycarbonate resin disclosed in Japanese Patent Application Publication No. 2023-121553 can be cited. For example, as a more preferred form of polycarbonate resin, the polycarbonate resin used in the embodiments described later can be cited.

[0127] As a combination of polyarylate resin and polycarbonate resin, a combination of resins having a biphenyl structural unit represented by the formula (BPa) is preferred.

[0128] As a combination of polyaryl ester resin and polycarbonate resin, a combination of polyaryl ester resin having at least one of dicarboxylic acid unit (A2-3) and diol unit (B7-1) and polycarbonate resin having structural unit (Cb7-1) is particularly preferred.

[0129] [Chemical Formula 2]

[0130]

[0131] From the viewpoint of affinity with polyarylate resins and polycarbonate resins, phenolic antioxidants are preferred as the antioxidants contained in the outermost layer, and hindered phenolic compounds are more preferred. One antioxidant may be used alone, or two or more may be used simultaneously.

[0132] Hindered phenolic compounds are generally defined as compounds in which at least one of the ortho positions of the hydroxyl groups of a phenol is replaced by a bulky group, and are known to exert an oxidative inhibitory effect on the composition.

[0133] Examples of hindered phenolic compounds include the following.

[0134] Alkylated monophenol compounds and their derivatives: for example, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, octyl-3,5-di-tert-butyl-4-hydroxy-hydroxycinnamate.

[0135] Alkylated hydroquinone compounds and their derivatives: for example, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-pentylhydroquinone

[0136] Alkylthiomethylphenol compounds and their derivatives: for example, 2,4-dioctylthiomethyl-6-tert-butylphenol, 2,4-dioctylthiomethyl-6-methylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, 2,6-docodecylthiomethyl-4-nonylphenol

[0137] Alkylene bisphenol compounds and their derivatives: for example, 4,4'-butylenebis(6-tert-butyl-3-methylphenol), 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane

[0138] Commercially available hindered phenolic compounds include ADEKA CORPORATION's "ADKSTAB AO-80", "ADKSTAB AO-60", "ADKSTAB AO-50", "ADKSTAB AO-40", "ADKSTAB AO-30", "ADKSTAB AO-20", and "ADKSTAB AO-330"; BASF Japan Ltd.'s "Irganox 1010", "Irganox 245", "Irganox 1076", and "Irganox 1520"; and Sumitomo Chemical Co., Ltd.'s "Sumilizer GA-80", "Sumilizer GM", and "Sumilizer GS".

[0139] Hindered phenolic compounds can be used alone or in combination with two or more compounds.

[0140] From the viewpoint of suppressing the oxidative degradation of the outermost layer, the content of antioxidant contained in the outermost layer is preferably 0.1% by mass or more and 20% by mass or less relative to the total mass of the outermost layer, more preferably 0.5% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less.

[0141] In the outermost layer of the photoreceptor, the proportion of fluoropolymer particles in the layer is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass (i.e., it does not contain fluoropolymer particles).

[0142] Given the high likelihood of stricter restrictions on the manufacture and use of organofluorine compounds in the future, the content of fluoropolymer particles is preferably within the range described above.

[0143] The thickness of the outermost layer can be set according to the function of that layer.

[0144] When the charge transport layer is the outermost layer, the thickness of the outermost layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 45 μm or less, and even more preferably 10 μm or more and 40 μm or less.

[0145] When the single-layer photosensitive layer is the outermost layer, the thickness of the outermost layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 45 μm or less, and even more preferably 10 μm or more and 40 μm or less.

[0146] The method for forming the outermost layer is the same as the method for forming the charge transport layer and the method for forming the single-layer photosensitive layer, which will be described later.

[0147] [Polyaryl ester resin (PA)]

[0148] The polyaryl ester resin included in the outermost layer is preferably a polyaryl ester resin having at least a dicarboxylic acid unit (A) and a diol unit (B). In this invention, such a polyaryl ester resin is referred to as polyaryl ester resin (PA).

[0149] The dicarboxylic acid unit (A) is a collective term for the dicarboxylic acid unit (A1) represented by formula (A1), the dicarboxylic acid unit (A2) represented by formula (A2), the dicarboxylic acid unit (A3) represented by formula (A3), the dicarboxylic acid unit (A4) represented by formula (A4), and the dicarboxylic acid unit (A5) represented by formula (A5).

[0150] The dicarboxylic acid unit (A) more preferably includes at least one selected from the group consisting of dicarboxylic acid units (A2), dicarboxylic acid units (A3) and dicarboxylic acid units (A4), and even more preferably includes dicarboxylic acid unit (A2).

[0151] [Chemical Formula 3]

[0152]

[0153] In equation (A1), n 101 n is an integer greater than or equal to 0 and less than or equal to 4. 101Ra 101 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0154] n 101 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0155] [Chemical Formula 4]

[0156]

[0157] In equation (A2), n 201 and n 202 Each of the following is an independent integer greater than 0 and less than 4, n 201 Ra 201 and n 202 Ra 202 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0158] n 201 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0159] n 202 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0160] [Chemical Formula 5]

[0161]

[0162] In equation (A3), n 301 and n 302 Each of the following is an independent integer greater than 0 and less than 4, n 301 Ra 301 and n 302 Ra 302 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0163] n 301 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0164] n 302 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0165] [Chemical Formula 6]

[0166]

[0167] In equation (A4), n 401 n is an integer greater than or equal to 0 and less than or equal to 6. 401 Ra 401 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0168] n 401 For example, it is preferably an integer greater than or equal to 0 and less than or equal to 4, more preferably 0, 1 or 2, and even more preferably 0.

[0169] [Chemical Formula 7]

[0170]

[0171] In equation (A5), n 501 n 502 and n 503 Each of the following is an independent integer greater than 0 and less than 4, n 501 Ra 501 n 502 Ra 502 and n 503 Ra 503 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

[0172] n 501 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0173] n 502 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0174] n 503 For example, 0, 1 or 2 is preferred, more preferably 0 or 1, and even more preferably 0.

[0175] Ra of formula (A1) 101 Ra of formula (A2) 201 and Ra 202 Ra of formula (A3) 301 and Ra 302 Ra of formula (A4) 401 And Ra of formula (A5) 501 Ra 502 and Ra 503 The specific methods and preferred methods are the same, therefore, Ra will be discussed below. 101 Ra 201 Ra202 Ra 301 Ra 302 Ra 401 Ra 501 Ra 502 and Ra 503 We will refer to them collectively as "Ra" for explanation.

[0176] The alkyl group involved in Ra with 1 or more and 10 or less carbon atoms can be any of straight-chain, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less, and even more preferably 1 or 2.

[0177] Examples of straight-chain alkyl groups with 1 or more but less than 10 carbon atoms include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl.

[0178] Examples of branched alkyl groups with 3 or more but less than 10 carbon atoms include isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, sec-hexyl, tert-hexyl, isohexyl, sec-heptyl, tert-heptyl, isooctyl, sec-octyl, tert-octyl, isononyl, sec-nonyl, tert-nonyl, isodel, sec-decyl, and tert-decyl.

[0179] Examples of cyclic alkyl groups with 3 or more but less than 10 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl groups formed by linking these monocyclic alkyl groups.

[0180] The aryl group involved in Ra, which has 6 or more but less than 12 carbon atoms, can be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more but less than 10, and more preferably 6.

[0181] Examples of aryl groups with 6 or more but less than 12 carbon atoms include phenyl, biphenyl, 1-naphthyl, and 2-naphthyl.

[0182] The alkyl group in the alkoxy group involving Ra, which has 1 or more and 6 or less carbon atoms, can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group, which has 1 or more and 4 or less carbon atoms, is preferably 1 or more and 3 or less, and even more preferably 1 or 2.

[0183] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0184] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0185] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0186] Hereinafter, dicarboxylic acid units (A1-1) to (A1-9) are specifically shown as dicarboxylic acid units (A1). The dicarboxylic acid unit (A1) is not limited to this.

[0187] [Chemical Formula 8]

[0188]

[0189] The following examples of dicarboxylic acid units (A2-1) to (A2-3) are shown as specific examples of dicarboxylic acid units (A2). The dicarboxylic acid unit (A2) is not limited to these examples.

[0190] [Chemical Formula 9]

[0191]

[0192] Hereinafter, dicarboxylic acid units (A3-1) to (A3-2) are specifically shown as dicarboxylic acid units (A3). The dicarboxylic acid unit (A3) is not limited to these.

[0193] [Chemical Formula 10]

[0194]

[0195] Hereinafter, dicarboxylic acid units (A4-1) to (A4-3) are specifically shown as dicarboxylic acid units (A4). The dicarboxylic acid unit (A4) is not limited to these.

[0196] [Chemical Formula 11]

[0197]

[0198] Hereinafter, dicarboxylic acid units (A5-1) to (A5-4) are specifically shown as dicarboxylic acid units (A5). The dicarboxylic acid unit (A5) is not limited to these.

[0199] [Chemical Formula 12]

[0200]

[0201] As a dicarboxylic acid unit (A), it is preferred to include at least one selected from the group consisting of (A1-1), (A1-7), (A2-3), (A3-2) and (A4-3) of the above specific examples, more preferably to include at least one selected from the group consisting of (A2-3), (A3-2) and (A4-3), and even more preferably to include at least (A2-3).

[0202] The dicarboxylic acid unit (A) contained in polyaryl ester resin (PA) can be one or more.

[0203] The mass percentage of dicarboxylic acid unit (A) in polyarylate resin (PA) is preferably 15% by mass or more and 60% by mass or less.

[0204] If the mass percentage of dicarboxylic acid unit (A) is 15% by mass or more, the wear resistance of the outermost layer is good. From this point of view, the mass percentage of dicarboxylic acid unit (A) is more preferably 20% by mass or more, and even more preferably 25% by mass or more.

[0205] If the mass percentage of dicarboxylic acid unit (A) is 60% by mass or less, the peeling of the outermost layer can be suppressed. From this point of view, the mass percentage of dicarboxylic acid unit (A) is more preferably 55% by mass or less, and even more preferably 50% by mass or less.

[0206] Polyaryl ester resins (PA) may contain dicarboxylic acid units other than the dicarboxylic acid unit (A). Examples of other dicarboxylic acid units include, for instance, aliphatic dicarboxylic acid units (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citracic acid, itaconic acid, pentenic acid, succinic acid, alkenyl succinic acid, adipic acid, sebacic acid), alicyclic dicarboxylic acid units (e.g., cyclohexanedicarboxylic acid), and their lower (e.g., having 1 or more but less than 5 carbon atoms) alkyl ester units. The polyaryl ester resin (PA) may contain one or more of these dicarboxylic acid units.

[0207] Diol unit (B) is a collective term for the diol unit (B1) represented by formula (B1), the diol unit (B2) represented by formula (B2), the diol unit (B3) represented by formula (B3), the diol unit (B4) represented by formula (B4), the diol unit (B5) represented by formula (B5), the diol unit (B6) represented by formula (B6), the diol unit (B7) represented by formula (B7), and the diol unit (B8) represented by formula (B8).

[0208] The diol unit (B) more preferably comprises 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 (B4) represented by formula (B4), diol units (B5) represented by formula (B5), and diol units (B6) represented by formula (B6).

[0209] Further preferably, it comprises at least one selected from the group consisting of diol units (B1) represented by formula (B2), diol units (B5) represented by formula (B5), and diol units (B6) represented by formula (B6).

[0210] More preferably, it comprises at least one selected from the group consisting of diol units (B1) represented by formula (B1), diol units (B2) represented by formula (B2), and diol units (B6) represented by formula (B6).

[0211] Most preferably, it comprises at least one of the groups consisting of diol units (B1) and (B2) represented by the following formula (B1).

[0212] [Chemical Formula 13]

[0213]

[0214] In equation (B1), Rb 101 Branched alkyl groups with 4 or more but less than 20 carbon atoms, Rb 201 Rb is an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 401 、Rb 501 、Rb 801 and Rb 901 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0215] Rb 101 The branched alkyl group involving 4 or more and 20 or less carbon atoms preferably has 4 or more and 16 or less carbon atoms, more preferably 4 or more and 12 or less, and even more preferably 4 or more and 8 or less. As Rb 101 Specific examples include isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, sec-hexyl, tert-hexyl, isohexyl, sec-heptyl, tert-heptyl, isooctyl, sec-octyl, tert-octyl, isononyl, sec-nonyl, tert-nonyl, isodel, sec-decyl, tert-decyl, isododecyl, sec-dodecyl, tert-dodecyl, tert-tetradecyl, tert-pentadecanyl, etc.

[0216] [Chemical Formula 14]

[0217]

[0218] In equation (B2), Rb 102 Rb is a straight-chain alkyl group with 4 or more but less than 20 carbon atoms. 202 Rb is an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 402 、Rb 502 、Rb 802 and Rb 902 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0219] Rb 102 The linear alkyl group involving 4 or more and 20 carbon atoms preferably has 4 or more and 16 or less carbon atoms, more preferably 4 or more and 12 or less, and even more preferably 4 or more and 8 or less. As Rb 102 Specific examples include n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, tridecyl, n-tetradecyl, n-pentadecanyl, n-heptadecyl, n-octadecyl, n-nonadecanyl, n-eicosyl, etc.

[0220] [Chemical Formula 15]

[0221]

[0222] In equation (B3), Rb 113 and Rb 213 Each of the following is independently a hydrogen atom, a straight-chain alkyl group having 1 or more but less than 3 carbon atoms, an alkoxy group having 1 or more but less than 4 carbon atoms, or a halogen atom, where d is an integer between 7 and 15, and Rb 403 、Rb 503 、Rb 803 and Rb 903 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0223] Rb 113 and Rb 213 The number of carbon atoms in the straight-chain alkyl group involving 1 or more and 3 or less is preferably 1 or 2, more preferably 1. Specific examples of this group include methyl, ethyl, and n-propyl.

[0224] Rb 113 and Rb 213The alkyl group in the alkoxy group with 1 or more and 4 or fewer carbon atoms can be any of straight-chain, branched, or cyclic. The alkyl group in the alkoxy group with 1 or more and 4 or fewer carbon atoms preferably has 1 or more and 3 or fewer carbon atoms, more preferably 1 or 2, and even more preferably 1. Specific examples of this group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy.

[0225] As Rb 113 and Rb 213 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0226] [Chemical Formula 16]

[0227]

[0228] In equation (B4), Rb 104 and Rb 204 Each is independently an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms, Rb 404 、Rb 504 、Rb 804 and Rb 904 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0229] Rb 104 The alkyl group involving 1 to 3 carbon atoms can be linear, branched, or cyclic. The alkyl group preferably has 1 or 2 carbon atoms, more preferably 1. As Rb 104 Specific examples include methyl, ethyl, n-propyl, isopropyl, and cyclopropyl.

[0230] [Chemical Formula 17]

[0231]

[0232] In equation (B5), Ar 105 Rb is an aryl group having 6 or more but less than 12 carbon atoms, or an aralkyl group having 7 or more but less than 20 carbon atoms. 205 Rb is an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 405 、Rb 505 、Rb 805 and Rb 905 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0233] Ar 105The aryl group involving 6 or more but less than 12 carbon atoms can be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more but less than 10, and more preferably 6.

[0234] Ar 105 The alkyl group in the aralkyl group having 7 or more and 20 or fewer carbon atoms can be any of straight-chain, branched, or cyclic. The alkyl group in the aralkyl group having 7 or more and 20 or fewer carbon atoms preferably has 1 or more and 4 or fewer carbon atoms, more preferably 1 or more and 3 or fewer carbon atoms, and even more preferably 1 or 2 carbon atoms. 105 The aryl group in the aralkyl group with 7 or more and 20 or less carbon atoms can be either monocyclic or polycyclic. The number of carbon atoms in the aryl group is preferably 6 or more and 10 or less, more preferably 6. Examples of aralkyl groups with 7 or more and 20 or less carbon atoms include benzyl, phenylethyl, phenylpropyl, 4-phenylbutyl, phenylpentyl, phenylhexyl, phenylheptyl, phenyloctyl, phenylnonyl, naphthylmethyl, naphthylethyl, anthraceneylmethyl, and phenyl-cyclopentylmethyl.

[0235] [Chemical Formula 18]

[0236]

[0237] In equation (B6), Rb 116 and Rb 216 Each of the following is independently a hydrogen atom, a straight-chain alkyl group having 1 or more but less than 3 carbon atoms, an alkoxy group having 1 or more but less than 4 carbon atoms, or a halogen atom, where e is an integer of 4 or more but less than 6, and Rb 406 、Rb 506 、Rb 806 and Rb 906 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0238] Rb 116 and Rb 216 The number of carbon atoms in the straight-chain alkyl group involving 1 or more and 3 or less is preferably 1 or 2, more preferably 1. Specific examples of this group include methyl, ethyl, and n-propyl.

[0239] Rb 116 and Rb 216The alkyl group in the alkoxy group with 1 or more and 4 or fewer carbon atoms can be any of straight-chain, branched, or cyclic. The alkyl group in the alkoxy group with 1 or more and 4 or fewer carbon atoms preferably has 1 or more and 3 or fewer carbon atoms, more preferably 1 or 2, and even more preferably 1. Specific examples of this group include methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, cyclopropoxy, and cyclobutoxy.

[0240] As Rb 116 and Rb 216 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0241] [Chemical Formula 19]

[0242]

[0243] In equation (B7), Rb 407 、Rb 507 、Rb 807 and Rb 907 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0244] [Chemical Formula 20]

[0245]

[0246] In equation (B8), Rb 408 、Rb 508 、Rb 808 and Rb 908 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

[0247] Rb in equation (B1) 201 Rb in equation (B2) 202 Rb in equation (B4) 204 and Rb of formula (B5) 205 The specific form and preferred form are the same, therefore, Rb will be referred to below. 201 、Rb 202 、Rb 204 and Rb 205 Collectively referred to as "Rb" 200 To explain.

[0248] Rb 200 The alkyl group involved, having 1 or more but less than 3 carbon atoms, can be any of the following: straight-chain, branched, or cyclic. The number of carbon atoms in the alkyl group is preferably 1 or 2, and more preferably 1.

[0249] Examples of alkyl groups with 1 or more but less than 3 carbon atoms include methyl, ethyl, n-propyl, isopropyl, and cyclopropyl.

[0250] Rb in equation (B1) 401 Rb in equation (B2) 402 Rb in equation (B3) 403 Rb in equation (B4) 404 Rb in equation (B5) 405 Rb in equation (B6) 406 Rb in equation (B7) 407 and Rb of formula (B8) 408 The specific form and preferred form are the same, therefore, Rb will be referred to below. 401 、Rb 402 、Rb 403 、Rb 404 、Rb 405 、Rb 406 、Rb 407 and Rb 408 Collectively referred to as "Rb" 400 To explain.

[0251] Rb 400 The alkyl group involving 1 or more and 4 or less carbon atoms can be any of the following: straight-chain, branched, and cyclic. The alkyl group preferably has 1 or more and 3 or less carbon atoms, more preferably 1 or 2, and even more preferably 1.

[0252] Examples of straight-chain alkyl groups with 1 or more but less than 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl.

[0253] Examples of branched alkyl groups with 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl.

[0254] Examples of cyclic alkyl groups with 3 or 4 carbon atoms include cyclopropyl and cyclobutyl.

[0255] Rb 400 The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms preferably has 1 or more and 4 or less carbon atoms, more preferably 1 or more and 3 or less carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0256] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0257] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0258] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0259] As Rb 400 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0260] Rb in equation (B1) 501 Rb in equation (B2) 502 Rb in equation (B3) 503 Rb in equation (B4) 504 Rb in equation (B5) 505 Rb in equation (B6) 506 Rb in equation (B7) 507 and Rb of formula (B8) 508 The specific form and preferred form are the same, therefore, Rb will be referred to below. 501 、Rb 502 、Rb 503 、Rb 504 、Rb 505 、Rb 506 、Rb 507 and Rb 508 Collectively referred to as "Rb" 500 To explain.

[0261] Rb 500 The alkyl group involving 1 or more and 4 or less carbon atoms can be any of the following: straight-chain, branched, and cyclic. The alkyl group preferably has 1 or more and 3 or less carbon atoms, more preferably 1 or 2, and even more preferably 1.

[0262] Examples of straight-chain alkyl groups with 1 or more but less than 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl.

[0263] Examples of branched alkyl groups with 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl.

[0264] Examples of cyclic alkyl groups with 3 or 4 carbon atoms include cyclopropyl and cyclobutyl.

[0265] Rb 500The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms preferably has 1 or more and 4 or less carbon atoms, more preferably 1 or more and 3 or less carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0266] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0267] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0268] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0269] As Rb 500 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0270] Rb in equation (B1) 801 Rb in equation (B2) 802 Rb in equation (B3) 803 Rb in equation (B4) 804 Rb in equation (B5) 805 Rb in equation (B6) 806 Rb in equation (B7) 807 and Rb of formula (B8) 808 The specific form and preferred form are the same, therefore, Rb will be referred to below. 801 、Rb 802 、Rb 803 、Rb 804 、Rb 805 、Rb 806 、Rb 807 and Rb 808 Collectively referred to as "Rb" 800 To explain.

[0271] Rb 800 The alkyl group involving 1 or more and 4 or less carbon atoms can be any of the following: straight-chain, branched, and cyclic. The alkyl group preferably has 1 or more and 3 or less carbon atoms, more preferably 1 or 2, and even more preferably 1.

[0272] Examples of straight-chain alkyl groups with 1 or more but less than 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl.

[0273] Examples of branched alkyl groups with 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl.

[0274] Examples of cyclic alkyl groups with 3 or 4 carbon atoms include cyclopropyl and cyclobutyl.

[0275] Rb 800 The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms preferably has 1 or more and 4 or less carbon atoms, more preferably 1 or more and 3 or less carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0276] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0277] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0278] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0279] As Rb 800 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0280] Rb in equation (B1) 901 Rb in equation (B2) 902 Rb in equation (B3) 903 Rb in equation (B4) 904 Rb in equation (B5) 905 Rb in equation (B6) 906 Rb in equation (B7) 907 and Rb of formula (B8) 908 The specific form and preferred form are the same, therefore, Rb will be referred to below. 901 、Rb 902 、Rb 903 、Rb 904 、Rb 905 、Rb 906 、Rb 907 and Rb 908 Collectively referred to as "Rb" 900 To explain.

[0281] Rb 900The alkyl group involving 1 or more and 4 or less carbon atoms can be any of the following: straight-chain, branched, and cyclic. The alkyl group preferably has 1 or more and 3 or less carbon atoms, more preferably 1 or 2, and even more preferably 1.

[0282] Examples of straight-chain alkyl groups with 1 or more but less than 4 carbon atoms include methyl, ethyl, n-propyl, and n-butyl.

[0283] Examples of branched alkyl groups with 3 or 4 carbon atoms include isopropyl, isobutyl, sec-butyl, and tert-butyl.

[0284] Examples of cyclic alkyl groups with 3 or 4 carbon atoms include cyclopropyl and cyclobutyl.

[0285] Rb 900 The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms can be any of the straight-chain, branched, and cyclic forms. The alkyl group in the alkoxy group with 1 or more and 6 or less carbon atoms preferably has 1 or more and 4 or less carbon atoms, more preferably 1 or more and 3 or less carbon atoms, and even more preferably 1 or 2 carbon atoms.

[0286] Examples of straight-chain alkoxy groups with 1 or more but less than 6 carbon atoms include methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, and n-hexoxy.

[0287] Examples of branched alkoxy groups with 3 or more but less than 6 carbon atoms include isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentoxy, neopentoxy, tert-pentoxy, isohexoxy, sec-hexoxy, and tert-hexoxy.

[0288] Examples of cyclic alkoxy groups with 3 or more but less than 6 carbon atoms include cyclopropoxy, cyclobutoxy, cyclopentoxy, and cyclohexoxy.

[0289] As Rb 900 The halogen atoms involved can be fluorine, chlorine, bromine, and iodine.

[0290] Hereinafter, diol units (B1-1) to (B1-6) are specifically shown as diol units (B1). The diol unit (B1) is not limited to this.

[0291] [Chemical Formula 21]

[0292]

[0293] Hereinafter, diol units (B2-1) to (B2-11) are specifically shown as diol units (B2). The diol unit (B2) is not limited to these.

[0294] [Chemical Formula 22]

[0295]

[0296] Hereinafter, diol units (B3-1) to (B3-4) are specifically shown as diol units (B3). The diol unit (B3) is not limited to these.

[0297] [Chemical Formula 23]

[0298]

[0299] Hereinafter, diol units (B4-1) to (B4-7) are specifically shown as diol units (B4). The diol unit (B4) is not limited to this.

[0300] [Chemical Formula 24]

[0301]

[0302] Hereinafter, diol units (B5-1) to (B5-6) are specifically shown as diol units (B5). The diol unit (B5) is not limited to these.

[0303] [Chemical Formula 25]

[0304]

[0305] Hereinafter, diol units (B6-1) to (B6-4) are specifically shown as diol units (B6). The diol unit (B6) is not limited to these.

[0306] [Chemical Formula 26]

[0307]

[0308] Hereinafter, diol units (B7-1) to (B7-3) are specifically shown as diol units (B7). The diol unit (B7) is not limited to these.

[0309] [Chemical Formula 27]

[0310]

[0311] Hereinafter, diol units (B8-1) to (B8-3) are specifically shown as diol units (B8). The diol unit (B8) is not limited to these.

[0312] [Chemical Formula 28]

[0313]

[0314] The diol unit (B) contained in polyaryl ester resin (PA) can be one or more.

[0315] The mass percentage of the diol unit (B) in the polyaryl ester resin (PA) is preferably 25% by mass or more and 80% by mass or less.

[0316] If the mass percentage of the diol unit (B) is 25% by mass or more, the peeling of the outermost layer can be suppressed. From this point of view, the mass percentage of the diol unit (B) is more preferably 30% by mass or more, and even more preferably 35% by mass or more.

[0317] If the mass percentage of the diol unit (B) is 80% by mass or less, the solubility of the coating liquid used to form the outermost surface layer can be maintained, thereby improving wear resistance. From this point of view, the mass percentage of the diol unit (B) is more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0318] Polyaryl ester resins (PA) may contain diol units other than the diol unit (B). Examples of other diol units include, for instance, aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol) and alicyclic diols (e.g., cyclohexanediol, cyclohexanediol, hydrogenated bisphenol A). The polyaryl ester resin (PA) may contain one or more of these diol units.

[0319] The ends of polyarylate resins (PA) can be sealed or modified by end-capping agents or molecular weight regulators used during manufacturing. Examples of end-capping agents or molecular weight regulators include monohydric phenols, monohydric acyl chlorides, monohydric alcohols, and monohydric carboxylic acids.

[0320] 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, and o-methoxyphenol. Phenol, m-methoxyphenol, p-methoxyphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, 3,5-xylenol, 2-phenyl-2-(4-hydroxyphenyl)propane, 2-phenyl-2-(2-hydroxyphenyl)propane, 2-phenyl-2-(3-hydroxyphenyl)propane.

[0321] Examples of monoacyl chlorides include benzoyl chloride, methanesulfonyl chloride, phenyl chloroformate, acetyl chloride, butyryl chloride, octanoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, phenylphosphonic chloride, and their substituted derivatives, which are all functional acid acyl halides.

[0322] Examples of monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenylethanol.

[0323] Examples of monocarboxylic acids include acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, methylbenzoic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid.

[0324] The weight-average molecular weight of the polyaryl ester resin (PA) is preferably 30,000 or more and 300,000 or less, more preferably 40,000 or more and 250,000 or less, and even more preferably 50,000 or more and 200,000 or less.

[0325] The molecular weight of polyaryl ester resin (PA) is the molecular weight converted from polystyrene as determined by GPC (gel permeation chromatography). Tetrahydrofuran is used as the eluent in GPC.

[0326] Polyaryl ester resins (PA) are obtained by conventional methods involving the polycondensation of monomers containing dicarboxylic acid units (A), monomers containing diol units (B), and other monomers as needed. Examples of monomer polycondensation methods include interfacial polymerization, solution polymerization, and melt polymerization. Interfacial polymerization is a polymerization method that obtains polyesters by mixing a dicarboxyl halogen dissolved in a water-incompatible organic solvent and a diol dissolved in an alkaline aqueous solution. References related to interfacial polymerization include WMEARECKSON, J. Poly. Sci., XL399, 1959, Japanese Patent Publication No. 40-1959. Compared to solution polymerization, interfacial polymerization has a faster reaction rate, thus suppressing the hydrolysis of the dicarboxyl halogen, resulting in the production of high molecular weight polyaryl ester resins (PA).

[0327] The following is a detailed description of each layer of the photoreceptor.

[0328] [Conductive substrate]

[0329] Examples of conductive substrates include metal plates, metal drums, and metal strips containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Furthermore, examples of conductive substrates include conductive compounds (e.g., conductive polymers, indium oxide, etc.); paper coated, vapor-deposited, or laminated with metals (e.g., aluminum, palladium, gold, etc.) or alloys; resin films; and tapes. Here, "conductivity" refers to a volume resistivity of less than 1 × 10⁻⁶. 13 Ω·cm.

[0330] When an electrophotographic photosensitive material is used in a laser printer, the surface of the conductive substrate is preferably roughened to 0.04 μm or more and 0.5 μm or less, based on the centerline average roughness Ra, in order to suppress interference fringes generated when the laser beam is irradiated. When incoherent light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but suppressing the generation of defects caused by unevenness on the conductive substrate surface is beneficial for extending the lifespan.

[0331] Examples of roughening methods include wet grinding, which involves suspending an abrasive in water and spraying it onto a conductive substrate; centerless grinding, which involves pressing a conductive substrate onto a rotating grinding wheel and continuously grinding it; and anodizing.

[0332] As a roughening method, another example is a method in which conductive or semi-conductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate without roughening the surface of the conductive substrate, and roughening is achieved by the particles dispersed in the layer.

[0333] Anodizing-based roughening is a process in which anodizing is performed in an electrolyte solution using a conductive metallic substrate (e.g., aluminum) as the anode, thereby forming an oxide film on the surface of the conductive substrate. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active in its original state, easily contaminated, and exhibits significant resistance variations due to environmental factors. Therefore, it is preferable, for example, to perform a sealing treatment on the porous anodic oxide film, where the micropores of the oxide film are blocked by the volume expansion caused by water and reaction in pressurized steam or boiling water (with the addition of metal salts such as nickel), thereby changing it into a more stable hydrated oxide.

[0334] The thickness of the anodic oxide film is preferably 0.3 μm or more and 15 μm or less. If the film thickness is within the above range, there is a tendency for it to act as a barrier against implantation, and there is a tendency for the rise in residual potential caused by repeated use to be suppressed.

[0335] Conductive substrates can be treated with acidic solutions or boehmite.

[0336] The treatment based on the acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and fluoric acid is prepared. The proportions of phosphoric acid, chromic acid, and fluoric acid in the acidic treatment solution are, for example, phosphoric acid in the range of 10% by mass or more and 11% by mass or less, chromic acid in the range of 3% by mass or more and 5% by mass or less, and fluoric acid in the range of 0.5% by mass or more and 2% by mass or less. The concentration of their total acid content is preferably in the range of 13.5% by mass or more and 18% by mass or less. The treatment temperature is preferably, for example, 42°C or more and 48°C or less. The film thickness is preferably, for example, 0.3 μm or more and 15 μm or less.

[0337] Boehmite treatment can be performed, for example, by immersion in pure water at a temperature above 90°C and below 100°C for 5 to 60 minutes, or by contact in heated steam at a temperature above 90°C and below 120°C for 5 to 60 minutes. The film thickness is preferably, for example, 0.1 μm or more and 5 μm or less. Further anodizing can be performed using electrolyte solutions with low film solubility, such as adipic acid, boric acid, borates, phosphates, phthalates, maleates, benzoates, tartrates, and citrates.

[0338] [Undercoat]

[0339] The undercoat layer may be, for example, a layer containing inorganic particles and a binding resin.

[0340] As inorganic particles, for example, the resistance (volume resistivity) of powder is 1×10⁻⁶. 2 Ω·cm or more and 1×10 11 Inorganic particles below Ω·cm.

[0341] Among them, inorganic particles having the above-mentioned resistance values ​​are preferably metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, and zinc oxide particles are particularly preferred.

[0342] The specific surface area of ​​inorganic particles based on the BET method is preferably, for example, 10 m². 2 / g or more.

[0343] The volume average particle size of the inorganic particles is preferably 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

[0344] The content of inorganic particles, relative to the bonding resin, is preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less.

[0345] Inorganic particles can be used for surface treatment. Two or more types of inorganic particles with different surface treatments or different particle sizes can be mixed together.

[0346] Examples of surface treatment agents include silane coupling agents, titanate coupling agents, aluminum coupling agents, and surfactants. In particular, silane coupling agents are preferred, and silane coupling agents having an amino group are more preferred.

[0347] Examples of amino-containing silane coupling agents include 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, but are not limited to these.

[0348] Two or more silane coupling agents can be used in combination. For example, an amino-containing silane coupling agent can be used in combination with other silane coupling agents. Other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacryloyloxypropyl-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.

[0349] Surface treatment methods based on surface treatment agents can be any known method, including either dry or wet methods.

[0350] The amount of surface treatment agent relative to the inorganic particles is preferably 0.5% by mass or more and 10% by mass or less.

[0351] From the viewpoint of improving the long-term stability of electrical properties and carrier blocking properties, the lower coating preferably contains, for example, an electron acceptor compound (acceptor compound) along with the inorganic particles.

[0352] Examples of electron-accepting compounds include compounds with anthraquinone structures; quinones such as chloroquinone and tetrabromobenzoquinone; dimethyl tetracyanobenzodiquinone; fluorenones such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazoles such as 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthones; thiophene compounds; biphenylquinones such as 3,3',5,5'-tetra-tert-butylbiphenylquinone; benzophenones such as 4-hydroxybenzophenone and 2,3,4-trihydroxybenzophenone; and other electron-transporting substances.

[0353] Especially as electron-accepting compounds, compounds having an anthraquinone structure are preferred, for example. As compounds having an anthraquinone structure, hydroxyanthraquinone compounds, aminoanthraquinone compounds, aminohydroxyanthraquinone compounds, etc. are preferred, specifically, anthraquinones, alizarin, quinone alizarin, anthraquinone, rutin, 4-ethoxy-1,2-hydroxy-9,10-anthraquinones and their derivatives are preferred.

[0354] Electron-accepting compounds can be dispersed in the undercoat along with inorganic particles, or they can be contained in the undercoat in a state of being attached to the surface of inorganic particles.

[0355] Methods for attaching electron-accepting compounds to the surface of inorganic particles include, for example, dry or wet methods.

[0356] Dry methods include, for example, the direct addition of an electron-accepting compound or an electron-accepting compound dissolved in an organic solvent while stirring inorganic particles using a mixer with high shear force, and spraying this compound along with dry air or nitrogen, thereby allowing the electron-accepting compound to adhere to the surface of the inorganic particles. The addition or spraying of the electron-accepting compound is preferably performed, for example, at a temperature below the boiling point of the solvent. After the addition or spraying of the electron-accepting compound, sintering can be performed at a temperature above 100°C. There are no particular limitations on the temperature and time for sintering, as long as the electron photographic properties are obtained.

[0357] Wet processes, for example, involve dispersing inorganic particles in a solvent using a mixer, ultrasonic disperser, sand mill, grinder, or ball mill. An electron-accepting compound is added, and the mixture is stirred or dispersed. The solvent is then removed, allowing the electron-accepting compound to adhere to the surface of the inorganic particles. Solvent removal methods include filtration or evaporation. After solvent removal, sintering can be performed at temperatures above 100°C. The temperature and time for sintering are not particularly limited as long as the electron imaging properties are obtained. In wet processes, the moisture content of the inorganic particles can be removed before adding the electron-accepting compound. Examples include removing moisture while stirring and heating in the solvent, or removing it through azeotropic mixing with the solvent.

[0358] The attachment of electron-receiving compounds can be performed before or after surface treatment of inorganic particles using a surface treatment agent, or the attachment of electron-receiving compounds can be performed simultaneously with surface treatment using a surface treatment agent.

[0359] The content of the electron-accepting compound is preferably 0.01% by mass or more and 20% by mass or less, and more preferably 0.01% by mass or more and 10% by mass or less, relative to inorganic particles.

[0360] Examples of known polymeric compounds used as adhesive resins in the undercoat include acetal resins (such as polyvinyl butyral), polyvinyl alcohol resins, polyvinyl alcohol acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyester resins, unsaturated polyester resins, methacrylic acid resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenolic resins, phenolic-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organotitanium compounds; and silane coupling agents.

[0361] Examples of adhesive resins used in the undercoat include charge-transporting resins with charge-transporting groups and conductive resins (e.g., polyaniline).

[0362] The adhesive resin used in the lower coating layer is preferably a resin that is insoluble in the coating solvent, and more preferably a resin obtained by reacting a curing agent with at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenolic resin, phenolic-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin; polyamide resin, polyester resin, polyether resin, methacrylic resin, acrylic resin, polyvinyl alcohol resin, and polyvinyl alcohol acetal resin.

[0363] When using two or more adhesive resins in combination, the mixing ratio should be set as needed.

[0364] To improve electrical properties, environmental stability, and image quality, various additives can be included in the undercoat.

[0365] Examples of additives include polycyclic condensation pigments, azo pigments, zirconium chelates, titanium chelates, aluminum chelates, titanium alkoxides, organotitanium compounds, and silane coupling agents. As mentioned earlier, silane coupling agents are used for surface treatment of inorganic particles, but they can also be added as additives to undercoatings.

[0366] Examples of silane coupling agents used as additives include vinyltrimethoxysilane, 3-methacryloyloxypropyltris(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.

[0367] Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetoacetate, zirconium triethanolamine, zirconium acetylacetone butoxide, zirconium acetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium methacrylate butoxide, zirconium stearate butoxide, and zirconium isostearate butoxide.

[0368] Examples of titanium chelate compounds include tetraisopropyl titanate, tetrabutyl titanate, tetrabutyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetone, polyacetylacetone titanium, octanediol titanium, titanium ammonium lactate, titanium lactate, titanium ethyl lactate, titanium triethanolamine, and titanium polyhydroxystearate.

[0369] Examples of aluminum chelate compounds include aluminum isopropoxide, aluminum monobutoxydiisopropoxide, aluminum butoxide, aluminum diacetoacetate diisopropoxide, and aluminum triacetoacetate.

[0370] These additives can be used alone or as a mixture or condensation polymer of multiple compounds.

[0371] The undercoat is preferably coated with a Vickers hardness of 35 or higher.

[0372] To suppress interference ripples, the surface roughness (ten-point average roughness) of the lower coating is preferably adjusted to, for example, 1 / (4n) to 1 / 2 of the wavelength λ of the laser used for exposure (where n is the refractive index of the upper layer).

[0373] To adjust surface roughness, resin particles can be added to the undercoat. Examples of resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. Furthermore, to adjust surface roughness, the surface of the undercoat can be ground. Examples of grinding methods include polishing, sandblasting, wet grinding, and grinding.

[0374] There are no particular limitations on the formation of the undercoat, and known formation methods can be used. However, for example, the formation of the undercoat is carried out by adding the above-mentioned components to the solvent to form a coating film of the coating liquid, drying the coating film, and heating as needed.

[0375] As solvents used to prepare coating liquids for forming the undercoat, known organic solvents can be cited, such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketol solvents, ether solvents, ester solvents, etc.

[0376] Specifically, examples of these solvents include, for instance, methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, toluene, and other common organic solvents.

[0377] Methods for dispersing inorganic particles during the preparation of coating liquid for forming a lower coating include, for example, known methods such as roller mills, ball mills, vibratory ball mills, grinding mills, sand mills, colloid mills, and paint mixers.

[0378] Methods for applying a coating liquid for forming an undercoat onto a conductive substrate include, for example, scraper coating, wire rod coating, spraying, dip coating, bead coating, air knife coating, and curtain coating.

[0379] The thickness of the lower coating is preferably 15 μm or more, and more preferably set in the range of 20 μm or more and 50 μm or less.

[0380] [Middle Layer]

[0381] The intermediate layer may be, for example, a layer containing resin. Examples of resins used in the intermediate layer include acetal resins (such as polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic acid resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenolic-formaldehyde resins, melamine resins, and other polymeric compounds.

[0382] The intermediate layer can be a layer containing 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.

[0383] The compounds used in these intermediate layers can be used alone or as a mixture of multiple compounds or as condensation polymers.

[0384] The intermediate layer is preferably a layer containing an organometallic compound containing zirconium or silicon atoms.

[0385] There are no particular limitations on the formation of the intermediate layer, and known formation methods can be used. However, for example, the intermediate layer is formed by adding the above-mentioned components to the solvent to form a coating film of the coating liquid, drying the coating film, and heating as needed.

[0386] As a coating method for forming the intermediate layer, conventional methods such as dip coating, push coating, bar coating, spraying, scraper coating, air knife coating, and curtain coating can be used.

[0387] The thickness of the intermediate layer is preferably set in the range of 0.1 μm or more and 3 μm or less. The intermediate layer can be used as the lower coating layer.

[0388] [charge generation layer]

[0389] The charge generation layer is, for example, a layer comprising a charge generation material and a binding resin. Furthermore, the charge generation layer can be a vapor-deposited layer of the charge generation material. Vapor-deposited layers of charge generation material are suitable, for example, for use with incoherent light sources such as LED (Light Emitting Diode) and organic EL (Electro-Luminescence) image arrays.

[0390] Examples of charge-generating materials include azo pigments such as diazo and triazo; fused-ring aromatic pigments such as dibromoanthracene anthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0391] To cope with laser exposure in the near-infrared region, metal phthalocyanine pigments or metal-free phthalocyanine pigments are preferably used as charge-generating materials. Specifically, hydroxy gallium phthalocyanine, gallium chloride phthalocyanine, dichlorotin phthalocyanine, and titanium dioxide phthalocyanine are more preferred.

[0392] On the other hand, in order to cope with laser exposure in the near-ultraviolet region, the preferred charge-generating materials are, for example, fused-ring aromatic pigments such as dibromoanthracene; sulfur-indigo pigments; porphyrin compounds; zinc oxide; trigonal selenium; and diazo pigments.

[0393] The above-mentioned charge-generating materials can be used even when using incoherent light sources such as LEDs and organic EL image arrays with a center wavelength of light emission above 450nm and below 780nm.

[0394] When n-type semiconductors such as fused-ring aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark currents are less likely to be generated, and even when used as thin films, image defects known as black spots can be suppressed. The determination of n-type is based on the commonly used time-of-flight method and the polarity of the flowing photocurrent; semiconductors that flow more easily with electrons than holes are classified as n-type.

[0395] The adhesive resin used in the charge generation layer is selected from a wide range of insulating resins, and the adhesive resin can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinyl anthracene, polyvinylpyrene, and polysilane.

[0396] Examples of adhesive resins include polyvinyl butyral resin, polyarylate resins (condensates of bisphenols and aromatic dicarboxylic acids, etc.), 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, "insulation" refers to a volume resistivity of 1×10⁻⁶. 13 Ω·cm or higher. These adhesive resins can be used alone or in combination of two or more.

[0397] The ratio of the charge-generating material to the binder resin is preferably in the range of 10:1 to 1:10 by mass.

[0398] Other known additives may be included in the charge generation layer.

[0399] There are no particular limitations on the formation of the charge-generating layer, and known formation methods can be used. However, for example, it can be performed by forming a coating film of a charge-generating layer forming liquid by adding the above-mentioned components to a solvent, drying the coating film, and heating it as needed. The formation of the charge-generating layer can be performed by vapor deposition of a charge-generating material. The formation of the charge-generating layer based on vapor deposition is particularly suitable, for example, when using polycyclic aromatic pigments or perylene pigments as charge-generating materials.

[0400] Examples of solvents used in preparing coating solutions for forming charge-generating layers include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, and toluene. These solvents can be used alone or in combination of two or more.

[0401] As a method for dispersing particles (e.g., charge-generating materials) in a coating liquid for forming a charge-generating layer, media dispersers such as ball mills, vibratory ball mills, grinders, sand mills, and horizontal sand mills, or media-free dispersers such as mixers, ultrasonic dispersers, roller mills, and high-pressure homogenizers can be used. Examples of high-pressure homogenizers include collision methods that disperse the dispersion by liquid-liquid collisions or liquid-wall collisions under high pressure, and penetration methods that disperse the dispersion by penetrating fine flow paths under high pressure. During dispersion, it is effective to set the average particle size of the charge-generating material in the coating liquid for forming the charge-generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0402] Methods for applying a coating liquid for forming a charge generation layer onto an underlying layer (or an intermediate layer) include, for example, scraper coating, wire rod coating, spraying, dip coating, bead coating, air knife coating, curtain coating, and other common methods.

[0403] The thickness of the charge generation layer is preferably set in the range of 0.1 μm or more and 5.0 μm or less, and more preferably in the range of 0.2 μm or more and 2.0 μm or less.

[0404] [charge transport layer]

[0405] The charge transport layer may be, for example, a layer comprising a binding resin and a charge transport material. Alternatively, the charge transport layer may be a layer comprising a polymeric charge transport material.

[0406] Examples of charge-transporting materials include quinone compounds such as p-benzoquinone, chloroquinone, tetrabromobenzoquinone, and anthraquinone; dimethyl compounds such as tetracyano-p-benzodiquinone; fluorenone compounds such as 2,4,7-trinitrofluorenone; anthrone compounds; benzophenone compounds; cyanoethylene compounds; and ethylene compounds, all of which are electron-transporting compounds. Examples of hole-transporting compounds include triarylamine compounds, benzidine compounds, arylalkyl compounds, aryl-substituted ethylene compounds, piracene compounds, anthracene compounds, and hydrazone compounds, all of which are hole-transporting compounds. These charge-transporting materials can be used alone or in combination, but are not limited to this.

[0407] Examples of polymeric charge-transporting materials include well-known chemical substances with charge-transporting properties such as poly-N-vinylcarbazole and polysilane. Polyester-based polymeric charge-transporting materials are preferred, for example. These materials can be used alone or in combination with a binding resin.

[0408] 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, organopolysilane compounds, pyrazoline compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, cyanide compounds, benzofuran compounds, aniline compounds, butadiene compounds, and resins having groups derived from these substances. Specifically, examples include paragraphs 0078-0080 of Japanese Patent Application Publication No. 2021-117377, paragraphs 0046-0048 of Japanese Patent Application Publication No. 2019-035900, paragraphs 0052-0053 of Japanese Patent Application Publication No. 2019-012141, paragraphs 0122-0134 of Japanese Patent Application Publication No. 2021-071565, and paragraphs 0021-0 The compounds described in paragraphs 0101 to 0110 of Japanese Patent Application Publication No. 15223, paragraph 0116 of Japanese Patent Application Publication No. 2013-097300, paragraphs 0309 to 0316 of International Publication No. 2019 / 070003, paragraphs 0103 to 0107 of Japanese Patent Application Publication No. 2018-159087, and paragraphs 0102 to 0113 of Japanese Patent Application Publication No. 2021-148818.

[0409] From the viewpoint of charge mobility, the charge transport material preferably comprises at least one selected from the group consisting of a chemical substance (C1) represented by formula (C1), a chemical substance (C2) represented by formula (C2), a chemical substance (C3) represented by formula (C3), and a chemical substance (C4) represented by formula (C4).

[0410] [Chemical Formula 29]

[0411]

[0412] In equation (C1), Ar T1 Ar T2 and Ar T3 They are independently aryl and -C6H4-C(R) T4 )=C(R T5 (R) T6 ) or -C6H4-CH=CH-CH=C(R T7 (R) T8 R T4 R T5 R T6 R T7 and R T8 Each is independently a hydrogen atom, alkyl group, or aryl group. In R T5 and R T6 When it is aryl, the aryl groups can cross each other via -C(R) 51 (R) 52 - and / or -C(R) 61 )=C(R 62 The divalent group (R) is linked to the )- group. 51 R 52 R 61 and R 62 Each is independently an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms.

[0413] The groups in formula (C1) may be substituted by halogen atoms, alkyl groups having 1 or more but less than 5 carbon atoms, alkoxy groups having 1 or more but less than 5 carbon atoms, or substituted amino groups having 1 or more but less than 3 carbon atoms.

[0414] As a chemical substance (C1), from the viewpoint of charge mobility, it is preferred, for example, to have at least one aryl group or -C6H4-CH=CH-CH=C(R T7 (R) T8 The chemical substance is more preferably the chemical substance represented by the following formula (C'1).

[0415] [Chemical Formula 30]

[0416]

[0417] In equation (C'1), R T111 R T112 R T121 R T122 R T131 and R T132 Each of the following is independently a hydrogen atom, a halogen atom, an alkyl group (preferably an alkyl group having 1 or more and 3 or less carbon atoms), an alkoxy group (preferably an alkoxy group having 1 or more and 3 or less carbon atoms), a phenyl group, or a phenoxy group. Tj1, Tj2, Tj3, Tk1, Tk2, and Tk3 are independently 0, 1, or 2.

[0418] [Chemical Formula 31]

[0419]

[0420] In equation (C2), R T201 R T202 R T211 and R T212 Each of the following is independently a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, an alkoxy group having 1 or more but less than 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, or a -C(R) group. T21 )=C(R T22 (R) T23 ) or -CH=CH-CH=C(R T24 (R) T25 R T21 R T22 R T23 R T24 and R T25 Each can be independently a hydrogen atom, alkyl group, or aryl group. R T221 and R T222 Each of the following is independently a hydrogen atom, a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, or an alkoxy group having 1 or more but less than 5 carbon atoms. Tm1, Tm2, ​​Tn1, and Tn2 are independently 0, 1, or 2, respectively.

[0421] The groups in formula (C2) may be substituted by halogen atoms, alkyl groups having 1 or more but less than 5 carbon atoms, alkoxy groups having 1 or more but less than 5 carbon atoms, or substituted amino groups having 1 or more but less than 3 carbon atoms.

[0422] As a chemical substance (C2), from the viewpoint of charge mobility, it is preferred, for example, to have at least one alkyl, aryl, or -CH=CH-CH=C(R) group. T24 (R) T25 The chemical substance is preferably a compound having two alkyl groups, aryl groups, or -CH=CH-CH=C(R) T24 (R)T25 ) chemical substances.

[0423] [Chemical Formula 32]

[0424]

[0425] In equation (C3), R T301 R T302 R T311 and R T312 Each of the following is independently a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, an alkoxy group having 1 or more but less than 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, or a -C(R) group. T31 )=C(R T32 (R) T33 ) or -CH=CH-CH=C(R T34 (R) T35 R T31 R T32 R T33 R T34 and R T35 Each can be independently a hydrogen atom, alkyl group, or aryl group. R T321 R T322 and R T331 Each of the following is independently a hydrogen atom, a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, or an alkoxy group having 1 or more but less than 5 carbon atoms. To1, To2, Tp1, Tp2, Tq1, Tq2, and Tr1 are independently 0, 1, or 2, respectively.

[0426] The groups in formula (C3) may be substituted by halogen atoms, alkyl groups having 1 or more but less than 5 carbon atoms, alkoxy groups having 1 or more but less than 5 carbon atoms, or substituted amino groups having 1 or more but less than 3 carbon atoms.

[0427] [Chemical Formula 33]

[0428]

[0429] In equation (C4), R T401 R T402 R T411 and R T412 Each of the following is independently a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, an alkoxy group having 1 or more but less than 5 carbon atoms, an amino group substituted with an alkyl group having 1 or 2 carbon atoms, an aryl group, or a -C(R) group. T41 )=C(R T42 (R) T43 ) or -CH=CH-CH=C(R T44 (R) T45 R T41 RT42 R T43 R T44 and R T45 Each can be independently a hydrogen atom, alkyl group, or aryl group. R T421 R T422 and R T431 Each of the following is independently a hydrogen atom, a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, or an alkoxy group having 1 or more but less than 5 carbon atoms. Ts1, Ts2, Tt1, Tt2, Tu1, Tu2, and Tv1 are independently 0, 1, or 2, respectively.

[0430] The groups in formula (C4) may be substituted by halogen atoms, alkyl groups having 1 or more but less than 5 carbon atoms, alkoxy groups having 1 or more but less than 5 carbon atoms, or substituted amino groups having 1 or more but less than 3 carbon atoms.

[0431] Examples of binder resins used in the charge transport layer include polycarbonate resins, polyester resins, polyarylate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, and polysilanes. Among these, polycarbonate resins or polyarylate resins are preferred as binder resins. These binder resins may be used alone or in combination with two or more other resins.

[0432] The mass ratio of charge transport material to binder resin is preferably, for example, 10:1 to 1:5.

[0433] When the charge transport layer is the outermost layer of the photoreceptor, the charge transport layer contains at least a polyaryl ester resin (PA) and a polycarbonate resin. As a combination of polyaryl ester resin (PA) and polycarbonate resin, it is preferable that both are resins having a biphenyl structural unit represented by the inclusion formula (BP).

[0434] Other known additives may be included in the charge transport layer.

[0435] There are no particular limitations on the formation of the charge transport layer, and known formation methods can be used. For example, a coating film can be formed by adding the above-mentioned components to a solvent for forming a charge transport layer, the coating film can be dried, and heating can be applied as needed.

[0436] Examples of solvents used in preparing coating solutions for charge transport layer formation include aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, and vinyl chloride; and cyclic or linear ethers such as tetrahydrofuran and diethyl ether. These solvents can be used alone or in combination of two or more.

[0437] Common methods for applying a coating liquid for forming a charge transport layer onto a charge generation layer include scraper coating, wire rod coating, spraying, dip coating, bead coating, air knife coating, and curtain coating.

[0438] The thickness of the charge transport layer is preferably set in the range of 5 μm or more and 50 μm or less, more preferably in the range of 8 μm or more and 45 μm or less, and even more preferably in the range of 10 μm or more and 40 μm or less.

[0439] [Single-layer photosensitive layer]

[0440] A single-layer photosensitive layer (charge generating / charge transporting layer) is, for example, a layer comprising a charge generating material, a charge transporting material, and, if necessary, a binding resin and other known additives. These materials are the same as those described in the charge generating layer and the charge transporting layer.

[0441] In a single-layer photosensitive layer, the content of the charge-generating material relative to the total solid content is, for example, 0.1% by mass or more and 10% by mass or less, preferably 0.8% by mass or more and 5% by mass or less. Furthermore, in a single-layer photosensitive layer, the content of the charge-transporting material relative to the total solid content is, for example, 5% by mass or more and 50% by mass or less.

[0442] 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.

[0443] The thickness of the single-layer photosensitive layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 45 μm or less, and even more preferably 10 μm or more and 40 μm or less.

[0444] When the monolayer photosensitive layer is the outermost layer of the photoreceptor, the monolayer photosensitive layer contains at least a polyaryl ester resin (PA) and a polycarbonate resin. As a combination of polyaryl ester resin (PA) and polycarbonate resin, it is preferable that both are resins having a biphenyl structural unit represented by the inclusion formula (BP).

[0445] <Image forming apparatus, processing box>

[0446] The image forming apparatus according to this embodiment includes an electrophotographic photosensitive material, a charging device for charging the surface of the electrophotographic photosensitive material, an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive material, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive material using a developing agent containing a toner to form a toner image, and a transfer device for transferring the toner image onto the surface of a recording medium. Furthermore, the electrophotographic photosensitive material according to this embodiment is applicable as the electrophotographic photosensitive material.

[0447] One embodiment of the image forming apparatus according to this embodiment includes a cleaning device having a cleaning blade that contacts the surface of an electrophotographic photosensitive element and cleans the surface of the photosensitive element. The cleaning device cleans the surface of the photosensitive element after toner image transfer and before it is charged by the cleaning blade.

[0448] The image forming apparatus according to this embodiment is applicable to the following known image forming apparatuses: an apparatus having a fixing apparatus for fixing a toner image transferred to the surface of a recording medium; an apparatus for a direct transfer method that directly transfers a toner image formed on the surface of an electrophotographic photosensitive body to the recording medium; an apparatus for an intermediate transfer method that transfers a toner image formed on the surface of an electrophotographic photosensitive body to the surface of an intermediate transfer body in one step, and then transfers the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium in a second step; an apparatus having an antistatic apparatus for irradiating the surface of an electrophotographic photosensitive body with antistatic light after the toner image transfer but before it becomes charged to eliminate static electricity; and an apparatus having an electrophotographic photosensitive body heating member for raising the temperature of the electrophotographic photosensitive body and lowering the relative temperature, etc.

[0449] In the case of an intermediate transfer method apparatus, the transfer apparatus may have a structure that includes an intermediate transfer body for transferring a toner image onto a surface, a primary transfer apparatus for transferring a toner image formed on the surface of an electrophotographic photosensitive body to the surface of the intermediate transfer body in one step, and a secondary transfer apparatus for transferring the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium in a second step.

[0450] The image forming apparatus described in this embodiment can be either a dry developing image forming apparatus or a wet developing image forming apparatus (a developing method that utilizes liquid developer).

[0451] In the image forming apparatus according to this embodiment, for example, the portion including the electrophotographic photosensitive element can be a cassette structure (processing cassette) that is detachable from the image forming apparatus. As the processing cassette, for example, a processing cassette including the electrophotographic photosensitive element according to this embodiment is preferably used. In addition to the electrophotographic photosensitive element, the processing cassette may also include at least one selected from the group consisting of a charging device, an electrostatic latent image forming apparatus, a developing apparatus, and a transfer apparatus.

[0452] The following describes an example of the image forming apparatus according to this embodiment, but it is not limited thereto. The main parts shown in the figures will be described, while the description of other parts will be omitted.

[0453] Figure 3 This is a schematic structural diagram illustrating an example of the image forming apparatus according to this embodiment.

[0454] like Figure 3 As shown, the image forming apparatus 100 according to this embodiment includes a processing cartridge 300 having an electrophotographic photosensitive element 7, an exposure apparatus 9 (an example of an electrostatic latent image forming apparatus), a transfer apparatus 40 (a primary transfer apparatus), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure apparatus 9 is positioned to expose the electrophotographic photosensitive element 7 through the opening of the processing cartridge 300, and the transfer apparatus 40 is positioned opposite the electrophotographic photosensitive element 7 across the intermediate transfer body 50, with a portion of the intermediate transfer body 50 in contact with the electrophotographic photosensitive element 7. Although not shown, a secondary transfer apparatus is also included to transfer the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer apparatus 40 (a primary transfer apparatus), and the secondary transfer apparatus (not shown) are examples of transfer apparatuses.

[0455] Figure 3 The processing cartridge 300 integrally supports the electrophotographic photoreceptor 7, the charging device 8 (an example of the charging device), the developing device 11 (an example of the developing device), and the cleaning device 13 (an example of the cleaning device) within the housing. The cleaning device 13 has a cleaning blade (an example of a cleaning component) 131, which is configured to contact the surface of the electrophotographic photoreceptor 7. The cleaning component may be a conductive or insulating fibrous component instead of the cleaning blade 131, and may be used alone or in conjunction with the cleaning blade 131.

[0456] exist Figure 3 In the example shown, as an image forming apparatus, a fibrous component 132 (roller-shaped) is provided for supplying lubricant 14 to the surface of the electrophotographic photosensitive element 7, and a fibrous component 133 (flat brush-shaped) is provided for auxiliary cleaning, but they can be configured as needed.

[0457] The structure of the image forming apparatus according to this embodiment will be described below.

[0458] -Electrified devices-

[0459] The charging device 8 can be a contact-type charging device where the charged component is in contact with the peripheral surface of the photoreceptor, or a non-contact-type charging device where the charged component is not in contact with the peripheral surface of the photoreceptor. The effect of the image forming apparatus according to this embodiment (not easily contaminated by the charged component over a long period of time) is particularly significant in the contact-type charging device.

[0460] As the charging device 8, contact-type charging components that utilize conductive or semi-conductive materials, such as charging rollers, charging brushes, charging films, charging rubber scrapers, and charging hoses, can be used. Furthermore, non-contact roller belt chargers, grid corona tube belt chargers utilizing corona discharge, or corona tube belt chargers, and other known charging devices, can also be used.

[0461] -Exposure device-

[0462] Examples of exposure devices 9 include optical systems that expose semiconductor lasers, LED lights, liquid crystal shutter lights, etc., onto the surface of an electrophotographic photosensitive object 7 to form a predetermined pattern. The wavelength of the light source is set within the spectral sensitivity range of the electrophotographic photosensitive object. Near-infrared light with an oscillation wavelength around 780 nm is the most common wavelength for semiconductor lasers. However, it is not limited to this wavelength; lasers with an oscillation wavelength in the 600 nm band or blue lasers, or lasers with an oscillation wavelength in the range of 400 nm to 450 nm, can also be used. Furthermore, surface-emitting laser sources capable of outputting multiple beams for forming color images are also effective.

[0463] -Developing apparatus-

[0464] As a developing apparatus 11, examples include conventional developing apparatuses that develop by contact or non-contact with the developer. There are no particular limitations on the developing apparatus 11 as long as it has the aforementioned functions, and it can be selected according to the purpose. For example, known developing machines that use brushes, rollers, etc., to adhere single-component or two-component developers to the electrophotographic photosensitive element 7 can be cited. Among these, a developing machine that uses a developing roller to hold the developer on the surface is preferred, for example.

[0465] The developer used in the developing apparatus 11 can be a single-component developer containing only a toner, or a two-component developer containing both a toner and charge carriers. Furthermore, the developer can be magnetic or non-magnetic. Commonly known developers are acceptable.

[0466] -Cleaning Device-

[0467] The cleaning device 13 is a device that uses a cleaning scraper, specifically a cleaning scraper 131. Details regarding the cleaning scraper will be described later.

[0468] -Transfer Device-

[0469] As a transfer device 40, examples include contact transfer belt appliances that use belts, rollers, films, rubber squeegees, etc.; grid corona tube transfer belt appliances that utilize corona discharge; and corona tube transfer belt appliances, which are known in themselves.

[0470] -Intermediate Transfer Material-

[0471] As the intermediate transfer body 50, a strip-shaped transfer body (intermediate transfer tape) containing polyimide, polyamide-imide, polycarbonate, polyarylate, polyester, rubber, etc., which imparts semi-conductivity can be used. Furthermore, in addition to a strip shape, a drum-shaped transfer body can also be used as the intermediate transfer body.

[0472] Figure 4 This is a schematic structural diagram showing another example of the image forming apparatus according to this embodiment.

[0473] Figure 4 The image forming apparatus 120 shown is a multicolor image forming apparatus equipped with four processing cartridges 300 arranged in series. In the image forming apparatus 120, four processing cartridges 300 are arranged on the intermediate transfer body 50, and a structure is formed in which one electrophotographic photosensitive element is used for each color. Except for the series arrangement, the image forming apparatus 120 has the same structure as the image forming apparatus 100.

[0474] [Cleaning scraper]

[0475] The cleaning scraper of the cleaning device of the image forming apparatus according to this embodiment is preferably of the following form.

[0476] The cleaning squeegee contains, at least the contact portion (hereinafter referred to as the "contact portion") that comes into contact with the photoreceptor, and even the components constituting the contact portion (hereinafter referred to as the "contact components"), a polyurethane rubber polymerized from at least a polyol component and a polyisocyanate component.

[0477] In the cleaning scraper, at least the ratio of the 100% modulus M100 (MPa) to the resilient modulus Re (%) of the contact portion or even the contact component is 0.25 or more, the resilient modulus Re is less than 25%, and the tensile stress at 200% strain is 15 MPa or more.

[0478] The cleaning scraper that meets the above characteristics improves the scraper's energy absorption capacity by increasing the ratio M100 / Re while reducing the resilient modulus and increasing the tensile stress, thereby reducing the pressure variation (i.e., maximum pressure) of the scraper and stabilizing the scraper's movement.

[0479] In this invention, the 100% modulus, resilience modulus, and tensile stress of the cleaning scraper are values ​​measured using the contact component as a sample and by the following measurement method.

[0480] Regarding the 100% modulus, it was measured according to JIS K6251:2010 using a dumbbell-shaped No. 3 test piece at a temperature of 23°C and a tensile speed of 500 mm / min, and determined based on the stress at 100% strain. The measuring apparatus used was a STROGRAPH AE elastomer (manufactured by Toyo Seiki-Seisaku-syo, Ltd.).

[0481] Regarding the resilient modulus, it shall be determined using a Lubbock rebound tester at an environment of 23°C, in accordance with JIS K6255:1996.

[0482] The tensile stress was measured at 200% strain at a temperature of 23°C. Measurements were taken using a dumbbell-shaped No. 3 test piece at a tensile speed of 500 mm / min. The measuring apparatus used was made of STROGRAPH AE elastomer (manufactured by Toyo Seiki-Seisaku-syo, Ltd.).

[0483] The ratio M100 / Re of the contact portion and even the contact component is 0.25 or more, preferably 0.28 or more, and more preferably 0.3 or more. From the viewpoint of wear resistance, the upper limit of the ratio M100 / Re of the contact portion and even the contact component is preferably 1.0 or less, and more preferably 0.9 or less. The ratio M100 / Re of the contact portion and even the contact component is preferably 0.25 or more and 1.0 or less, more preferably 0.28 or more and 1.0 or less, and even more preferably 0.3 or more and 0.9 or less.

[0484] The spring modulus Re of the contact portion and even the contact component is less than 25%, preferably 22% or less, and more preferably 20% or less. From the viewpoint of suppressing scraper noise and improving wear resistance, the lower limit of the spring modulus Re of the contact portion and even the contact component is preferably 10% or more, and more preferably 13% or more. The spring modulus Re of the contact portion and even the contact component is preferably 10% or more and less than 25%, more preferably 10% or more and less than 22%, and even more preferably 13% or more and less than 20%.

[0485] From the viewpoint of satisfying the above characteristics, the 100% modulus M100 of the contact portion or even the contact component is preferably 4 MPa or more and 10 MPa or less, and more preferably 5 MPa or more and 9 MPa or less.

[0486] The tensile stress at 200% strain of the contact portion or even the contact component is 15 MPa or more, preferably 21 MPa or more, and more preferably 26 MPa or more. The upper limit of the tensile stress of the contact portion or even the contact component is preferably 40 MPa or less, more preferably 35 MPa or less. The tensile stress of the contact portion or even the contact component is preferably 15 MPa or more and 40 MPa or less, more preferably 21 MPa or more and 40 MPa or less, and even more preferably 26 MPa or more and 35 MPa or less.

[0487] Polyurethane rubber preferably has both hard and soft segments. The 100% modulus, resilience modulus, and tensile stress of the contact portion and even the contact component can be controlled by adjusting the ratio of hard to soft segments in the polyurethane rubber according to the type and amount of polymer components used and the manufacturing conditions.

[0488] From the viewpoint that it is easy to set the 100% modulus, spring modulus and tensile stress within the aforementioned range, the average diameter of the aggregate of hard segments is preferably 1 μm or more and 10 μm or less, more preferably 1 μm or more and 5 μm or less.

[0489] The average diameter of the aggregate of hard segments was determined by the following method.

[0490] Images were captured at 20x magnification using a polarizing microscope (BX51-P, manufactured by Olympus Corporation), and image processing was performed to binarize the images. The equivalent diameter of 500 aggregates (5 points per point, 5 points per slab) was measured using 20 cleaning blades, and the arithmetic mean of the 500 equivalent diameters was calculated. For image binarization, OLYMPUS Stream essentials image processing software (manufactured by Olympus Corporation) was used to adjust the hue / chroma / brightness thresholds so that crystalline regions and hard segments appeared black, while amorphous regions (equivalent to soft segments) appeared white.

[0491] The weight-average molecular weight of polyurethane rubber is preferably 1,000 or more and 4,000 or less, and more preferably 1,500 or more and 3,500 or less.

[0492] From the viewpoint of controlling the 100% modulus, resilience modulus, and tensile stress within the aforementioned ranges, the crosslinking density of the polyurethane rubber is preferably, for example, 0.93 × 10⁻⁶. -3mol / m 3 Above and 1.45×10 -3 mol / m 3 Hereinafter, 1.01 × 10 is more preferred. -3 mol / m 3 The above and 1.26×10 -3 mol / m 3 The following is a further preferred value of 1.07 × 10⁻⁶. -3 mol / m 3 Above and 1.22×10 - 3 mol / m 3 the following.

[0493] The following section describes the materials and composition of the contact parts and even the contact components.

[0494] The molecular weights of polyurethane rubber and its components are determined by gel permeation chromatography (GPC).

[0495] Polyurethane rubber is a polyurethane rubber formed by polymerizing at least a polyol component and a polyisocyanate component. Polyurethane rubber can also be a polyurethane rubber formed by further polymerizing a resin having functional groups that react with isocyanate groups, as needed.

[0496] • Polyol components

[0497] Polyols include both high-molecular-weight polyols and low-molecular-weight polyols.

[0498] Polyols with a number average molecular weight of 500 or higher are preferred. For example, polyols with a number average molecular weight of 5000 or lower are preferred. Examples of polyols with a number average molecular weight include: polyester polyols obtained by dehydration condensation of low molecular weight polyols with diacids; polycarbonate polyols obtained by reaction of low molecular weight polyols with alkyl carbonates; polycaprolactone polyols; polyether polyols; and other known polyols. Commercially available polyols with a number average molecular weight include, for example, PLACEL 205 and PLACEL 240 manufactured by Daicel Corporation. A single polyol may be used, or two or more may be used simultaneously.

[0499] The polymerization ratio of the polymeric polyol relative to all polymeric components of the polyurethane rubber is preferably 30 mol% or more and 50 mol% or less, more preferably 40 mol% or more and 50 mol% or less.

[0500] Low molecular weight polyols are polyols with a number average molecular weight of less than 500. Low molecular weight polyols are materials that function as chain extenders and crosslinking agents.

[0501] 1,4-Butanediol is an example of a low-molecular-weight polyol. The proportion of 1,4-butanediol relative to the total polyol content is preferably more than 50 mol% and less than 75 mol%, more preferably more than 52 mol% and less than 75 mol%, even more preferably more than 55 mol% and less than 75 mol%, and even more preferably more than 55 mol% and less than 60 mol%. The proportion of 1,4-butanediol relative to all low-molecular-weight polyols is preferably more than 80 mol%, more preferably more than 90 mol%, and even more preferably 100 mol%. Most preferably, all low-molecular-weight polyols are 1,4-butanediol.

[0502] In addition to 1,4-butanediol, other low-molecular-weight polyols known as chain extenders and crosslinking agents include diols (2-functional), triols (3-functional), and tetraols (4-functional). These polyols, except for 1,4-butanediol, can be used alone or in combination with two or more.

[0503] The polymerization ratio of low molecular weight polyols relative to the total polymerization content of polyurethane rubber is preferably more than 50 mol% and less than 75 mol%, more preferably more than 52 mol% and less than 75 mol%, even more preferably more than 55 mol% and less than 75 mol%, and even more preferably more than 55 mol% and less than 60 mol%.

[0504] Polyisocyanate component

[0505] Examples of polyisocyanate components include 4,4'-diphenylmethane diisocyanate (MDI), 2,6-toluene diisocyanate (TDI), 1,6-hexyl diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI), and 3,3'-dimethylbiphenyl-4,4'-diisocyanate (TODI). A single polyisocyanate component can be used, or two or more can be used simultaneously.

[0506] As a polyisocyanate component, 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI), and hexamethylene diisocyanate (HDI) are preferred, for example.

[0507] Relative to all polymeric components of polyurethane rubber, the polymerization ratio of the polyisocyanate component is preferably 5 mol% or more and 25 mol% or less, more preferably 10 mol% or more and 20 mol% or less. If the polymerization ratio of the polyisocyanate component is set within this range, it is easy to set the 100% modulus, resilience modulus, and tensile stress within the aforementioned range.

[0508] • Resins having functional groups that react with isocyanate groups (resins containing functional groups)

[0509] As a resin containing functional groups, a resin with flexibility is preferred, and an aliphatic resin with a linear structure is more preferred. Specific examples of resins containing functional groups include acrylic resins containing two or more hydroxyl groups, polybutadiene resins containing two or more hydroxyl groups, and epoxy resins having two or more epoxy groups.

[0510] Commercially available acrylic resins containing two or more hydroxyl groups include, for example, ACTFLOW UMB-2005B, UMB-2005P, UMB-2005, UME-2005, etc. (manufactured by Soken Chemical & Engineering Co., Ltd.).

[0511] Commercially available products containing two or more hydroxyl groups include, for example, R-45HT (manufactured by Idemitsu Kosan Co., Ltd.).

[0512] As for epoxy resins having two or more epoxy groups, epoxy resins that are more flexible and tougher than general epoxy resins are preferred. For example, epoxy resins with a flexible backbone in the main chain structure are preferred. Examples of flexible backbones include alkylene backbones, cycloalkane backbones, and polyoxyethylene backbones, with polyoxyethylene backbones being particularly preferred. Furthermore, epoxy resins with a low viscosity relative to their molecular weight are preferred. Specifically, epoxy resins with a weight-average molecular weight in the range of 900 ± 100 and a viscosity at 25°C in the range of 15000 ± 5000 mPa·s are preferred, and more preferably in the range of 15000 ± 3000 mPa·s are preferred. Commercially available epoxy resins with these characteristics include, for example, EPICLON EXA-4850-150 (manufactured by DICCorporation).

[0513] Manufacturing method of polyurethane rubber

[0514] In manufacturing polyurethane rubber, conventional manufacturing methods such as the prepolymer method and the one-shot method can be used. Polyurethane rubber is manufactured by forming the polyurethane rubber composition into sheets through centrifugal molding, extrusion molding, etc. Subsequently, the polyurethane rubber is cut and processed to manufacture contact parts.

[0515] Examples of catalysts used in the manufacture of polyurethane rubber include amine compounds such as tertiary amines, organometallic compounds such as quaternary ammonium salts and organotin compounds. A single catalyst can be used, or two or more catalysts can be used simultaneously.

[0516] Examples of tertiary amines include trialkylamines such as triethylamine; tetraalkyldiamines such as N,N,N',N'-tetramethyl-1,3-butanediamine; amino alcohols such as dimethylethanolamine; ester amines such as ethoxylated amines, ethoxylated diamines, and bis(diethylethanolamine) adipate; cyclohexylamine derivatives such as triethylenediamine (TEDA) and N,N-dimethylcyclohexylamine; morpholine derivatives such as N-methylmorpholine and N-(2-hydroxypropyl)-dimethylmorpholine; piperazine derivatives such as N,N'-diethyl-2-methylpiperazine and N,N'-bis-(2-hydroxypropyl)-2-methylpiperazine; and so on.

[0517] Examples of quaternary ammonium salts include 2-hydroxypropyltrimethylammonium octanoate, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) octanoate, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) octanoate, DBU oleate, DBU p-toluenesulfonate, DBU formate, and 2-hydroxypropyltrimethylammonium formate.

[0518] Examples of organotin compounds include dialkyltin compounds such as dibutyltin dilaurate and dibutyltin di(2-ethylhexanoate); stannous 2-ethylhexanoate and stannous oleate; etc.

[0519] From the viewpoint of hydrolysis resistance, triethylenediamine (TEDA), a tertiary ammonium salt, is preferred, for example; from the viewpoint of processability, a quaternary ammonium salt is preferred. Among the quaternary ammonium salts, highly reactive 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) octanoate, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) octanoate, and DBU formate are used.

[0520] The amount of catalyst added is preferably in the range of 0.0005% by mass or more and 0.03% by mass or less of the total amount of polyurethane rubber constituting the contact component, and more preferably 0.001% by mass or more and 0.01% by mass or less.

[0521] refer to Figures 5-7 The implementation method of the cleaning scraper is described.

[0522] Figure 5 This is a schematic diagram showing the cleaning scraper according to the first embodiment, and a diagram showing the state of contact with the surface of the photoreceptor.

[0523] Figure 6 This is a schematic diagram showing the cleaning scraper according to the second embodiment, and a diagram showing the state of contact with the surface of the photoreceptor.

[0524] Figure 7 This is a schematic diagram showing the cleaning scraper according to the third embodiment, and a diagram showing the state of contact with the surface of the photoreceptor.

[0525] like Figure 5 As shown, the cleaning scraper has a contact corner 3A, a front face 3B, a ventral face 3C, and a back face 3D.

[0526] The contact corner portion 3A is a contact portion that contacts the driven photoreceptor 31 and cleans the surface of the photoreceptor 31.

[0527] The front surface 3B is the surface with one edge formed by the contact corner portion 3A, and it is the upstream side facing the driving direction (arrow A direction) of the photoreceptor 31. The ventral surface 3C is the surface with one edge formed by the contact corner portion 3A, and it is the downstream side facing the driving direction (arrow A direction) of the photoreceptor 31. The back surface 3D is the surface that shares one edge with the front surface 3B, and it is the surface opposite to the ventral surface 3C.

[0528] A support member (not shown) is joined to the upper part (the side away from the photoreceptor 31) of the ventral side 3C or rear side 3D of the cleaning blade, and the cleaning blade is supported by the support member. The cleaning blade is pressed against the photoreceptor 31 by force from the support member. Examples of support members include metal parts such as aluminum and stainless steel. An adhesive layer may be present between the support member and the cleaning blade.

[0529] Figure 5 The cleaning scraper 342A shown is made entirely of a single material, including the contact corner 3A; that is, it is a form consisting only of contact parts.

[0530] Figure 6 The cleaning scraper 342B shown has a double-layer structure consisting of a first layer 3421B including contact corners and a second layer 3422B supporting the first layer. The second layer 3422B is made of a different material than the first layer 3421B.

[0531] Figure 7 The cleaning scraper 342C shown is a structure consisting of a contact member 3421C including contact corner portions and a back member 3422C supporting the contact member 3421C. The contact member 3421C has a shape that divides a cylinder into four parts, with the right-angled portion of a quarter circle forming the contact corner portion 3A. The contact member 3421C can be a square prism, a rectangular prism, or the like. The back member 3422C is made of a different material than the contact member 3421C.

[0532] Figure 5 The cleaning scraper 342A shown Figure 6 The first layer 3421B of the cleaning scraper 342B shown is... Figure 7 The contact part 3421C of the cleaning scraper 342C shown is composed of a part containing polyurethane rubber formed by polymerizing at least a polyol component and a polyisocyanate component.

[0533] Figure 5 The cleaning scraper 342A shown Figure 6 The first layer 3421B of the cleaning scraper 342B shown is... Figure 7 The cleaning scraper 342C shown has a 100% modulus M100 (MPa) to a resilient modulus Re (%) ratio M100 / Re of 0.25 or more, a resilient modulus Re of less than 25%, and a tensile stress of 15 MPa or more at 200% strain.

[0534] Figure 6 The second layer 3422B of the cleaning scraper 342B shown and Figure 7 The back part 3422C of the cleaning scraper 342C shown functions as a support for the contact parts. Examples of materials for these parts include polyurethane rubber, silicone rubber, fluororubber, neoprene rubber, and butadiene rubber. Polyurethane rubber is preferred, for example. Examples of polyurethane rubbers include ester-based polyurethanes and ether-based polyurethanes, with ester-based polyurethanes being the most preferred.

[0535] Figure 5 The cleaning scraper 342A shown is manufactured by cutting polyurethane rubber, etc.

[0536] Figure 6 The cleaning scraper 342B shown is manufactured by bonding the first layer 3421B and the second layer 3422B together with an adhesive or the like, or by allowing the rubber material to flow into the mold during polyurethane rubber molding at a time difference to manufacture the laminate.

[0537] Figure 7 The cleaning scraper 342C shown is, for example, manufactured as a polyurethane rubber component in which four scrapers are joined together with the contact member 3421C as the center, and is manufactured in four parts.

[0538] Example

[0539] The following describes the implementation of the invention in detail with reference to the embodiments, but the implementation of the invention is not limited to these embodiments in any way.

[0540] Unless otherwise specified, “parts” and “%” are quality standards in the following description.

[0541] Unless otherwise specified, the synthesis, processing, and manufacturing processes are carried out at room temperature (25℃±3℃).

[0542] <The Manufacturing of Photoreceptors>

[0543] The following resin, charge transport material, and antioxidant were prepared as materials to form the outermost surface layer (charge transport layer). • Polyarylate resin (PA1): Number of biphenyl molecules per unit molecular weight BP1 = 0.0020

[0544] • Polyaryl ester resin (PA2): Number of biphenyl molecules per unit molecular weight BP1 = 0.0020

[0545] • Polyaryl ester resin (PA3): Number of biphenyl molecules per unit molecular weight BP1 = 0.0020

[0546] • Polyaryl ester resin (PA4): Number of biphenyl molecules per unit molecular weight BP1 = 0.0019

[0547] • Polyarylate resin (PA5): Number of biphenyl molecules per unit molecular weight BP1 = 0

[0548] • Polyarylate resin (PA6): Number of biphenyl molecules per unit molecular weight BP1 = 0

[0549] • Polyaryl ester resin (PA7): Number of biphenyl molecules per unit molecular weight BP1 = 0.0004

[0550] • Polyarylate resin (PA8): Number of biphenyl molecules per unit molecular weight BP1 = 0

[0551] • Polyarylate resin (PA9): Number of biphenyl molecules per unit molecular weight BP1 = 0

[0552] • Polyarylate resin (PA10): Number of biphenyls per unit molecular weight BP1 = 0

[0553] The molar ratios of the structural units of polyarylate resins are shown in Table 1.

[0554] [Chemical Formula 34]

[0555]

[0556] [Chemical Formula 35]

[0557]

[0558] [Chemical Formula 36]

[0559]

[0560] • Polycarbonate resin (PC1): Number of biphenyls per unit molecular weight BP2 = 0.0009 • Polycarbonate resin (PC2): Number of biphenyls per unit molecular weight BP2 = 0.0018 The numbers marked on the structural units indicate the molar ratio.

[0561] [Chemical Formula 37]

[0562]

[0563] • Charge transport material CTM-1: Molecular weight 516.67: Number of biphenyl molecules per unit molecular weight BP3 = 1 / 516.67 = 0.0019

[0564] • Charge transport material CTM-2: Number of biphenyl molecules per unit molecular weight BP3 = 0

[0565] [Chemical Formula 38]

[0566]

[0567] • Antioxidant: ADKSTAB AO-80 (manufactured by ADEKA CORPORATION): Number of biphenyl molecules per unit molecular weight BP4 = 0

[0568] [Chemical Formula 39]

[0569]

[0570] <The Manufacturing of Photoreceptors>

[0571] [Example 1]

[0572] -Formation of the undercoat-

[0573] 3.5 parts of butyral resin (trade name: S-LEC BM-1, manufactured by SEKISUI CHEMICAL CO.,LTD.) and 41 parts of methyl ethyl ketone were mixed and dissolved. 10 parts of curing agent (blocked isocyanate, trade name: SUMIDUR 3175, manufactured by Sumitomo Bayer Urethane Co.,Ltd.), 45.5 parts of zinc oxide (trade name: SMZ-017N, manufactured by TAYCACORPORATION) surface-treated with silane coupling agent (trade name: KBM603, manufactured by Shin-Etsu Chemical Co.,Ltd.), and 0.27 parts of the following compound were added and stirred. The mixture was then dispersed using 1 mm diameter glass beads in a sand mill for 2 hours. Furthermore, 0.01 parts of dioctyltin dilaurate and 2 parts of silicone resin particles (trade name: TOSPEARL145, manufactured by GE Toshiba Silicones Co., Ltd.) were added and stirred to obtain a coating solution for forming the lower coating layer. The coating solution for forming the lower coating layer was applied to the outer peripheral surface of the conductive substrate by dip coating method, and dried and cured at 170°C for 40 minutes to form a lower coating layer with a thickness of 20 μm.

[0574] [Chemical Formula 40]

[0575]

[0576] -Formation of the charge generation layer-

[0577] A mixture consisting of 15 parts of hydroxygallium phthalocyanine (X-ray diffraction spectra using CuKα characteristic X-rays showing 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°) as the charge-generating material, 10 parts of vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, manufactured by Nippon Unicar Company Limited) as the binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill for 4 hours using glass beads with a diameter of 1 mm. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion, and the mixture was stirred to obtain a coating solution for forming a charge-generating layer. The coating solution for forming the charge-generating layer was impregnated onto a lower coating layer and dried at room temperature to form a charge-generating layer with a thickness of 0.25 μm.

[0578] -Formation of the charge transport layer-

[0579] • Resin: Polyarylate resin (PA1)……32.3 parts (95% of total resin)

[0580] • Resin: Polycarbonate resin (PC1)……1.7 parts (5% of total resin)

[0581] • Charge transport material: CTM-1……63.1 parts

[0582] • Antioxidant: ADEKA STAB AO-80……3.0 parts

[0583] Solvent: Tetrahydrofuran...500 parts

[0584] Solvent: Toluene...50 parts

[0585] The above materials were stirred and mixed to obtain a coating solution for forming a charge transport layer. The coating solution for forming a charge transport layer was then applied onto the charge generation layer and dried at 143°C for 30 minutes to form a charge transport layer with a thickness of 33 μm.

[0586] [Examples 2 to 19, Comparative Examples 1 to 3]

[0587] The same procedure as in Example 1 was followed, but the specifications of the charge transport layer were changed as shown in Tables 1 and 2, and each photoreceptor was manufactured.

[0588] The "Resin Ratio" shown in Table 1 is the mass ratio relative to the total mass of polyarylate resin and polycarbonate resin.

[0589] <Performance Evaluation>

[0590] [Double image]

[0591] The photoreceptors of each embodiment or comparative example were mounted on the image forming apparatus Versant 4100Press (manufactured by Xerox Corporation). The cleaning blades of each image forming apparatus were replaced with cleaning blades having the physical properties shown in Table 3.

[0592] Under conditions of 28°C and 85% relative humidity, 5000 character charts with an image density (area coverage) of 5% were printed on A3 plain paper. Subsequently, one black midtone image with an image density of 40% was printed on A3 plain paper. The black midtone image was observed visually and classified as follows.

[0593] A: The characters of the random chart are not visible on the black mid-tone image.

[0594] B: Characters of a random chart are faintly visible on a black mid-tone image.

[0595] C: The characters of the random chart are clearly visible on the black mid-tone image.

[0596] Uneven concentration

[0597] The photoreceptors of each embodiment or comparative example were mounted in the image forming apparatus AltaLink C8070 (manufactured by Xerox Corporation). The cleaning blades of each image forming apparatus were replaced with cleaning blades having the physical properties shown in Table 3.

[0598] Thirty black midtone images with a density of 40% were printed on A3 plain paper at an environment of 20°C and 40% relative humidity. The final output images were visually observed and categorized as follows.

[0599] A: There is no uneven concentration.

[0600] B: There is a slight unevenness in concentration.

[0601] C: There are uneven concentrations that are practically unusable.

[0602] In Comparative Example 1A, the same photoreceptor as in Comparative Example 1 was installed in an AltaLink C8100 image forming apparatus (manufactured by Xerox Corporation), and the cleaning blade was replaced with a cleaning blade having the physical properties shown in Table 3. Performance evaluation (ghosting and uneven density) was then performed.

[0603] In Example 3A, the same photoreceptor as in Example 3 was installed in an AltaLink C8100 image forming apparatus (manufactured by Xerox Corporation), and the cleaning blade was replaced with a cleaning blade having the physical properties shown in Table 3. Performance evaluation (ghosting and uneven density) was then performed.

[0604] [Table 1]

[0605]

[0606] [Table 2]

[0607]

[0608] [Table 3]

[0609]

[0610] The electrophotographic photosensitive element, processing cartridge, and image forming apparatus of the present invention include the following configurations. The same formulas as those with the same numbers as those described above.

[0611] (Postscript)

[0612] (1) An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer disposed on the conductive substrate, wherein,

[0613] The outermost layer contains a first resin, a second resin, a charge transport material, and an antioxidant.

[0614] At least one of the first resin and the second resin has a structural unit comprising biphenyl represented by the following formula (BPa).

[0615] At least one of the charge transport material and the antioxidant has at least one of the following formulas: biphenyl represented by formula (BPa) and biphenyl represented by formula (BPb).

[0616] When the number of biphenyl molecules per unit molecular weight of the first resin, the second resin, the charge transport material, and the antioxidant is set as BP1, BP2, BP3, and BP4, and the respective proportions (mass%) of the first resin, the second resin, the charge transport material, and the antioxidant in the total amount are set as MP1, MP2, MP3, and MP4,

[0617] The relationship satisfies 0.0≤(BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4)≤3.0.

[0618] (2) According to the electrophotographic photosensitive material described in (1), wherein,

[0619] The relationship satisfies 0.5≤(BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4)≤2.5.

[0620] (3) The electrophotographic photosensitive material according to (1) or (2), wherein,

[0621] The antioxidant contains hindered phenolic compounds.

[0622] (4) The electrophotographic photosensitive material according to any one of (1) to (3), wherein,

[0623] The first resin is a polyarylate resin, and the second resin is a polycarbonate resin.

[0624] (5) The electrophotographic photosensitive material according to (4), wherein,

[0625] The proportion of polyaryl ester resin in the total amount of polyaryl ester resin and polycarbonate resin contained in the outermost surface layer is more than 25% by mass and less than 75% by mass.

[0626] (6) The electrophotographic photosensitive material according to (4) or (5), wherein,

[0627] The polyaryl ester resin has 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), a dicarboxylic acid unit (A4) represented by formula (A4), and a dicarboxylic acid unit (A5) represented by formula (A5).

[0628] (7) The electrophotographic photosensitive material according to any one of (4) to (6), wherein,

[0629] The polyaryl ester resin has at least one selected from the group consisting of a diol unit (B1) represented by formula (B1), a diol unit (B2) represented by formula (B2), a diol unit (B3) represented by formula (B3), a diol unit (B4) represented by formula (B4), a diol unit (B5) represented by formula (B5), a diol unit (B6) represented by formula (B6), a diol unit (B7) represented by formula (B7), and a diol unit (B8) represented by formula (B8).

[0630] (8) The electrophotographic photosensitive material according to any one of (1) to (7), wherein,

[0631] The photosensitive layer has a charge generation layer and a charge transport layer, wherein the charge transport layer is the outermost layer.

[0632] (9) A processing box comprising the electrophotographic photosensitive element as described in any one of (1) to (8),

[0633] The processing box is mounted and dismounted from the image forming apparatus.

[0634] (10) An image forming apparatus comprising:

[0635] The electrophotographic photosensitive material as described in any one of (1) to (8);

[0636] A charging device is used to charge the surface of the electrophotographic photosensitive element.

[0637] An electrostatic latent image forming apparatus forms an electrostatic latent image on the surface of the charged electrophotographic photoreceptor;

[0638] A developing apparatus that develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor using a developing agent containing a toner to form a toner image; and

[0639] A transfer device transfers the toner image onto the surface of a recording medium.

[0640] (11) The image forming apparatus according to (10) further comprises:

[0641] A cleaning device having a cleaning scraper that contacts the surface of the electrophotographic photosensitive element and cleans the surface of the electrophotographic photosensitive element.

[0642] (12) The image forming apparatus according to (11), wherein,

[0643] The contact portion of the cleaning scraper that contacts the electrophotographic photosensitive element is composed of the following components: a polyurethane rubber containing at least a polyol component and a polyisocyanate component polymerized together, wherein the ratio of 100% modulus M100 (MPa) to resilience modulus Re (%) M100 / Re is 0.25 or more, the resilience modulus Re is less than 25%, and the tensile stress at 200% strain is 15 MPa or more.

[0644] (13) The image forming apparatus according to (12), wherein,

[0645] The ratio M100 / Re is 0.28 or higher and 1.0 or lower.

[0646] According to (1), (3), (4), (5), (6), (7) or (8), an electrophotographic photoreceptor is provided that is less prone to ghosting and uneven density in images compared with an electrophotographic photoreceptor whose value of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) exceeds 3.0.

[0647] According to (2), an electrophotographic photoreceptor is provided that is less prone to ghosting and uneven density in images compared to an electrophotographic photoreceptor with a value of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) less than 0.5 or more than 2.5.

[0648] According to (9), a processing box is provided that is less prone to ghosting and uneven density in images compared to cases where the value of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) of an electrophotographic photoreceptor exceeds 3.0.

[0649] According to (10) or (11), an image forming apparatus is provided that is less prone to ghosting and uneven density in the image compared to cases where the value of (BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4) of the electrophotographic photoreceptor exceeds 3.0.

[0650] According to (12), an image forming apparatus is provided that is less prone to ghosting and uneven density in images compared to an image forming apparatus with a ratio M100 / Re of less than 0.25, a spring modulus Re of more than 25%, or a tensile stress of less than 15 MPa.

[0651] According to (13), an image forming apparatus is provided in which the ratio M100 / Re to the cleaning squeegee is less than 0.28 or greater than 1.0, and the image forming apparatus is less prone to ghosting and uneven density in the image.

[0652] The embodiments of the present invention described above are provided for illustrative purposes. Furthermore, these embodiments do not encompass the entirety of the invention, nor do they limit the invention to the disclosed methods. It will be apparent to those skilled in the art that various modifications and variations will be readily understood. These embodiments were chosen and described to most readily explain the principles and applications of the invention. Thus, those skilled in the art can understand the invention through various modifications that are assumed to be optimized for specific uses of various embodiments. The scope of the invention is defined by the foregoing claims and their equivalents.

Claims

1. An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer disposed on the conductive substrate, wherein, The outermost layer contains a first resin, a second resin, a charge transport material, and an antioxidant. At least one of the first resin and the second resin has a structural unit comprising biphenyl represented by the following formula (BPa). At least one of the charge transport material and the antioxidant has at least one of the following formulas: biphenyl represented by formula (BPa) and biphenyl represented by formula (BPb). When the number of biphenyl molecules per unit molecular weight of the first resin, the second resin, the charge transport material, and the antioxidant is set as BP1, BP2, BP3, and BP4, and the respective proportions (mass%) of the first resin, the second resin, the charge transport material, and the antioxidant in the total amount are set as MP1, MP2, MP3, and MP4, The relationship 0.0 ≤ (BP1×MP1 + BP2×MP2) / (BP3×MP3 + BP4×MP4) ≤ 3.0 is satisfied. [Chemical Formula 1] Formula (BPa) Formula (BPb) In the formula (BPa), j is an integer greater than or equal to 0 and less than or equal to 4, and j are R... 1 Each is independently methyl or ethyl, k is an integer greater than or equal to 0 and less than or equal to 4, and k R's are independent of each other. 2 Each can be independently methyl or ethyl. Multiple methyl groups and / or ethyl groups can bond together to form a ring. In the formula (BPb), m is an integer greater than or equal to 0 and less than or equal to 4, and m are R's. 3 Each is independently methyl or ethyl, n is an integer greater than or less than 5, and n R 4 Each can be independently methyl or ethyl. Multiple methyl groups and / or ethyl groups can bond together to form a ring.

2. The electrophotographic photosensitive material according to claim 1, wherein, The relationship satisfies 0.5≤(BP1×MP1+BP2×MP2) / (BP3×MP3+BP4×MP4)≤2.

5.

3. The electrophotographic photosensitive material according to claim 1 or 2, wherein, The antioxidant contains hindered phenolic compounds.

4. The electrophotographic photosensitive material according to any one of claims 1 to 3, wherein, The first resin is a polyarylate resin, and the second resin is a polycarbonate resin.

5. The electrophotographic photosensitive material according to claim 4, wherein, The proportion of polyaryl ester resin in the total amount of polyaryl ester resin and polycarbonate resin contained in the outermost surface layer is more than 25% by mass and less than 75% by mass.

6. The electrophotographic photosensitive material according to claim 4 or 5, wherein, The polyaryl ester resin has at least one selected from the group consisting of dicarboxylic acid units (A1) represented by formula (A2), dicarboxylic acid units (A3), dicarboxylic acid units (A4), and dicarboxylic acid units (A5). [Chemical Formula 2] Equation (A1) Formula (A2) Formula (A3) Equation (A4) Formula (A5) In equation (A1), n 101 n is an integer greater than 0 and less than 4. 101 Ra 101 Each of the following can be independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms. In equation (A2), n 201 and n 202 Each of the following is an independent integer greater than 0 and less than 4, n 201 Ra 201 and n 202 Ra 202 Each of the following can be independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms. In equation (A3), n 301 and n 302 Each of the following is an independent integer greater than 0 and less than 4, n 301 Ra 301 and n 302 Ra 302 Each of the following can be independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms. In equation (A4), n 401 n is an integer greater than 0 and less than 6. 401 Ra 401 Each of the following can be independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms. In equation (A5), n 501 n 502 and n 503 Each of the following is an independent integer greater than 0 and less than 4, n 501 Ra 501 n 502 Ra 502 and n 503 Ra 503 Each is independently an alkyl group having 1 or more but less than 10 carbon atoms, an aryl group having 6 or more but less than 12 carbon atoms, or an alkoxy group having 1 or more but less than 6 carbon atoms.

7. The electrophotographic photosensitive material according to any one of claims 4 to 6, wherein, The polyaryl ester resin has 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). [Chemical Formula 3] Formula (B1) Formula (B2) Formula (B3) Equation (B4) [Chemical Formula 4] Formula (B5) Formula (B6) Formula (B7) Formula (B8) In equation (B1), Rb 101 Branched alkyl groups with 4 or more but less than 20 carbon atoms, Rb 201 Rb is an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 401 、Rb 501 、Rb 801 and Rb 901 Each of the following is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom. In equation (B2), Rb 102 Rb is a straight-chain alkyl group with 4 or more but less than 20 carbon atoms. 202 Rb is an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 402 、Rb 502 、Rb 802 and Rb 902 Each of the following is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom. In equation (B3), Rb 113 and Rb 213 Each of the following is independently a hydrogen atom, a straight-chain alkyl group having 1 or more but less than 3 carbon atoms, an alkoxy group having 1 or more but less than 4 carbon atoms, or a halogen atom, where d is an integer between 7 and 15, and Rb 403 、Rb 503 、Rb 803 and Rb 903 Each of the following is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom. In equation (B4), Rb 104 and Rb 204 Each is independently an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms, Rb 404 、Rb 504 、Rb 804 and Rb 904 Each of the following is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom. In equation (B5), Ar 105 Rb is an aryl group having 6 or more but less than 12 carbon atoms, or an aralkyl group having 7 or more but less than 20 carbon atoms. 205 Rb is an alkyl group having 1 or more hydrogen atoms and 3 or fewer carbon atoms. 405 、Rb 505 、Rb 805 and Rb 905 Each of the following is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom. In equation (B6), Rb 116 and Rb 216 Each of the following is independently a hydrogen atom, a straight-chain alkyl group having 1 or more but less than 3 carbon atoms, an alkoxy group having 1 or more but less than 4 carbon atoms, or a halogen atom, where e is an integer of 4 or more but less than 6, and Rb 406 、Rb 506 、Rb 806 and Rb 906 Each of the following is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom. In equation (B7), Rb 407 、Rb 507 、Rb 807 and Rb 907 Each of the following is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom. In equation (B8), Rb 408 、Rb 508 、Rb 808 and Rb 908 Each is independently a hydrogen atom, an alkyl group having 1 or more but less than 4 carbon atoms, an alkoxy group having 1 or more but less than 6 carbon atoms, or a halogen atom.

8. The electrophotographic photosensitive material according to any one of claims 1 to 7, wherein, The photosensitive layer has a charge generation layer and a charge transport layer, wherein the charge transport layer is the outermost layer.

9. A processing cartridge comprising the electrophotographic photosensitive element as described in any one of claims 1 to 8. The processing box is mounted and dismounted from the image forming apparatus.

10. An image forming apparatus comprising: Electrophotographic photoresist according to any one of claims 1 to 8; A charging device is used to charge the surface of the electrophotographic photosensitive element. An electrostatic latent image forming apparatus forms an electrostatic latent image on the surface of the charged electrophotographic photoreceptor; A developing apparatus that develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor using a developing agent containing a toner to form a toner image; and A transfer device transfers the toner image onto the surface of a recording medium.

11. The image forming apparatus according to claim 10, further comprising: A cleaning device having a cleaning scraper that contacts the surface of the electrophotographic photosensitive element and cleans the surface of the electrophotographic photosensitive element.

12. The image forming apparatus according to claim 11, wherein, The contact portion of the cleaning scraper that contacts the electrophotographic photosensitive element is composed of the following components: a polyurethane rubber containing at least a polyol component and a polyisocyanate component polymerized together, wherein the ratio of 100% modulus M100 (MPa) to resilience modulus Re (%) M100 / Re is 0.25 or more, the resilience modulus Re is less than 25%, and the tensile stress at 200% strain is 15 MPa or more.

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

Images