Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that prevents the generation of color points while reducing wear of a photosensitive layer.SOLUTION: An electrophotographic photoreceptor has a conductive substrate, and a single-layer photosensitive layer that is provided on the conductive substrate and contains a binder resin, a charge generating material, a hole transport material, and an electron transport material, in which an index A represented by the following formula (1) is within a range of -7.98 or more and -7.28 or less. Formula (1): A=(0.057×M)-(0.002×F)-(0.252×μ). In the formula (1), M represents the Martens hardness of the photosensitive layer, F the Young's modulus of the photosensitive layer, and μ the elastic deformation rate of the photosensitive layer.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In a conventional electrophotographic image forming apparatus, a toner image formed on the surface of an electrophotographic photoreceptor is transferred to a recording medium through processes of charging, electrostatic latent image formation, development, and transfer.

[0003] For example, Patent Document 1 discloses "a photoreceptor containing gallium phthalocyanine in a charge generation material and having a martensitic hardness of 170 N / mm 2 or more and 200 N / mm 2 or less".

[0004] Further, Patent Document 2 discloses "an electrophotographic photoreceptor having a conductive substrate and a single-layer type photosensitive layer provided on the conductive substrate, the photosensitive layer containing a binder resin, a charge generation material, a hole transport material, and a specific electron transport material, and having a photosensitive layer with an elastic deformation rate R of 0.340 or more and 0.360 or less".

[0005] Also, Patent Document 3 discloses "when testing the hardness of an electrophotographic photoreceptor using a Vickers square pyramid diamond indenter, the universal hardness value (HU) when pressed in with a load of 6 mN is 150 N / mm 2 or more and 220 N / mm 2 or less, and having an elastic deformation rate of 50% or more and 65% or less, and further having an insert inside the support".

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide an electrophotographic photoreceptor having a single-layer photosensitive layer containing a binder resin, a charge generation material, a hole transport material, and an electron transport material, which reduces wear of the photosensitive layer and suppresses the generation of color spots as compared with the case where the index A represented by the following formula (1) is less than -7.98 or more than -7.28.

Means for Solving the Problems

[0008] The means for solving the above problems include the following aspects. <1> A conductive substrate, A single-layer photosensitive layer provided on the conductive substrate, containing a binder resin, a charge generation material, a hole transport material, and an electron transport material, and having an index A represented by the following formula (1) in the range of -7.98 or more and -7.28 or less. An electrophotographic photoreceptor having the above. Formula (1): A = (0.057 × M) - (0.002 × F) - (0.252 × μ) In formula (1), M represents the Martens hardness of the photosensitive layer, F represents the Young's modulus of the photosensitive layer, and μ represents the elastic deformation rate of the photosensitive layer. <2> The electrophotographic photoreceptor according to <1>, wherein the index A is in the range of -7.80 or more and -7.34 or less. <3> The electrophotographic photoreceptor according to <1> or <2>, wherein the mass ratio of the hole transport material to the electron transport material (the hole transport material / the electron transport material) is 19 / 5 or more and 28 / 5 or less. <4> The electrophotographic photoreceptor according to <3>, wherein the content of the hole transport material with respect to the total solid content of the photosensitive layer is 38% by mass or more and 44% by mass or less. <5> The electrophotographic photoreceptor according to any one of <1> to <4>, wherein the hole transport material is a hole transport material having a benzidine skeleton. <6> The electrophotographic photoreceptor according to <5>, wherein the hole transport material having the benzidine skeleton is a hole transport material represented by the following general formula (HT1a).

Chemical formula

Chemical formula

Chemical formula

Advantages of the Invention

[0009] According to the invention according to <1>, in an electrophotographic photoreceptor having a single-layer photosensitive layer containing a binder resin, a charge generation material, a hole transport material, and an electron transport material, when the index A represented by the following formula (1) is less than -7.98 or more than -7.28, an electrophotographic photoreceptor is provided that reduces wear of the photosensitive layer and suppresses generation of color spots. According to the invention according to <2>, an electrophotographic photoreceptor is provided that reduces wear of the photosensitive layer and suppresses generation of color spots when the index A is less than -7.80 or more than -7.34. According to the invention according to <3>, an electrophotographic photoreceptor is provided that reduces wear of the photosensitive layer and suppresses generation of color spots when the mass ratio of the hole transport material to the electron transport material (hole transport material / electron transport material) is less than 19 / 5 or more than 28 / 5. According to the invention according to <4>, an electrophotographic photoreceptor is provided that reduces wear of the photosensitive layer and suppresses generation of color spots when the content of the hole transport material is less than 38% by mass or more than 44% by mass with respect to the photosensitive layer.

[0010] According to the invention according to <5> or <6>, an electrophotographic photoreceptor is provided that reduces wear of the photosensitive layer and suppresses generation of color spots when the hole transport material is a hole transport material that is HTM-B used in the comparative examples described later. According to the invention according to <7> or <8>, an electrophotographic photoreceptor is provided that reduces wear of the photosensitive layer and suppresses generation of color spots when the electron transport material is an electron transport material that is ETM-B or ETM-C used in the comparative examples described later.

[0011] According to the invention according to <9> or <10>, an electrophotographic photoreceptor is provided that reduces wear of the photosensitive layer and suppresses generation of color spots when the binder resin is a polyarylate resin.

[0012] According to the invention according to <11> or <13>, in an electrophotographic photoreceptor having a single-layer photosensitive layer containing a binder resin, a charge generation material, a hole transport material, and an electron transport material, compared with the case of providing an electrophotographic photoreceptor in which the index A represented by the following formula (1) is less than -7.98 or more than -7.28, a process cartridge or an image forming apparatus that reduces wear of the photosensitive layer and suppresses generation of color spots is provided.

[0013] According to the invention according to <12> or <14>, compared with the case where the difference (absolute value) in Young's modulus between the photosensitive layer of the electrophotographic photoreceptor and the surface of the developing roll is less than 3785 or more than 4675, a process cartridge or an image forming apparatus that reduces wear of the photosensitive layer and suppresses generation of color spots is provided.

Brief Description of Drawings

[0014]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments which are examples of the present invention will be described in detail.

[0016] In the numerical ranges described step by step in this specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical ranges described in other step-by-step descriptions. Further, in the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

[0017] In this specification, the term "step" includes not only an independent step but also this term if the intended purpose of the step is achieved even when it cannot be clearly distinguished from other steps. Each component may contain a plurality of corresponding substances. When referring to the amount of each component, if there are a plurality of substances corresponding to each component, unless otherwise specified, it means the total amount of the plurality of substances. An electrophotographic photoreceptor having a single-layer photosensitive layer is also referred to as a "single-layer photoreceptor". The single-layer photosensitive layer is a photosensitive layer having hole-transporting properties and electron-transporting properties in addition to charge-generation ability.

[0018] [Electrophotographic Photoreceptor] The electrophotographic photoreceptor according to the present embodiment has a conductive substrate and a single-layer photosensitive layer provided on the conductive substrate and containing a binder resin, a charge-generation material, a hole-transporting material, and an electron-transporting material. And the index A represented by the following formula (1) in the photosensitive layer is in the range of -7.98 or more and -7.28 or less. Formula (1): A = (0.057 × M) - (0.002 × F) - (0.252 × μ) In formula (1), M represents the Martens hardness of the photosensitive layer, F represents the Young's modulus of the photosensitive layer, and μ represents the elastic deformation rate of the photosensitive layer.

[0019] Here, in an electrophotographic photoreceptor, from the viewpoint of improving the lifespan, the abrasion resistance of the photosensitive layer is required. On the other hand, if paper dust or the like easily adheres to the photosensitive layer and the cleanability is low, color spots may occur due to the adhering substances.

[0020] In contrast, the electrophotographic photoreceptor according to the present embodiment improves the abrasion resistance by the index A of the photosensitive layer satisfying the above range. In addition, it is difficult for paper dust or the like to adhere to the photosensitive layer, and the cleanability of the photosensitive layer is improved. Therefore, the electrophotographic photoreceptor according to the present embodiment suppresses the generation of color spots while reducing the abrasion of the photosensitive layer.

[0021] Hereinafter, the electrophotographic photoreceptor according to the present embodiment will be described in detail.

[0022] In the electrophotographic photoreceptor according to this embodiment, the index A of the photosensitive layer is in the range of -7.98 or more and -7.28 or less. From the viewpoints of improving abrasion resistance and suppressing the generation of color spots, the range of -7.89 or more and -7.30 or less is preferable, and the range of -7.80 or more and -7.34 or less is more preferable.

[0023] To make the index A within the above range, for example, 1) The type of hole transport material (preferably using a hole transport material having a benzidine skeleton) 2) The type of electron transport material (preferably using an electron transport material having a diphenoquinone skeleton) 3) The type and molecular weight of the binder resin (preferably using a polycarbonate resin) and the like are controlled.

[0024] From the viewpoints of improving abrasion resistance and suppressing the generation of color spots, the Martens hardness M of the photosensitive layer is preferably 160 N / mm 2 or more and 240 N / mm 2 or less, more preferably 170 N / mm 2 or more and 230 N / mm 2 or less, and still more preferably 180 N / mm 2 or more and 225 N / mm 2 or less.

[0025] From the viewpoints of improving abrasion resistance and suppressing the generation of color spots, the Young's modulus F of the photosensitive layer is preferably 3500 MPa or more and 4900 MPa or less, more preferably 3700 MPa or more and 4800 MPa or less, and still more preferably 4000 MPa or more and 4700 MPa or less.

[0026] From the viewpoints of improving abrasion resistance and suppressing the generation of color spots, the elastic deformation rate μ of the photosensitive layer is preferably 35% or more and 50% or less, more preferably 38% or more and 48% or less, and still more preferably 40% or more and 45% or less.

[0027] Here, the Martens hardness, Young's modulus, and elastic deformation rate of the photosensitive layer are values measured when a indenter is pressed into the photoreceptor surface (photosensitive layer). The specific measurement method is as follows. First, a photoreceptor having a photosensitive layer to be measured is set in a measuring device (PICODENTOR HM500 manufactured by Fisher Instruments) in an environment of 23°C and 30% RH. Then, a load is continuously increased on the surface of the photoreceptor (i.e., the photosensitive layer) using a Vickers indenter, and each physical property (Martens hardness, Young's modulus, and elastic deformation rate) measured when it is pushed in by 0.5 μm is determined. The measurement locations are at positions 40 mm and 80 mm from both ends and five positions at the center, and the average value of the measurement values at these five positions is taken as each physical property value.

[0028] - Martens hardness of the photosensitive layer - The Martens hardness of the photosensitive layer is determined by dividing the test load by the surface area of the indenter when the indenter is pushed in under the above conditions.

[0029] - Young's modulus of the photosensitive layer - The Young's modulus of the photosensitive layer is determined by measuring the indentation depth - load curve when the indenter is pushed in under the above conditions, applying a load at a maximum indentation depth of 500 nm, and then unloading, and taking the slope of the unloading curve as the Young's modulus.

[0030] - Elastic deformation rate of the photosensitive layer - The elastic deformation rate of the photosensitive layer is determined by measuring the displacement amount up to the load peak and the displacement return amount after releasing the load when the indenter is pushed in under the above conditions, and taking the ratio as the elastic deformation rate of the photosensitive layer.

[0031] Next, while referring to the drawings, the electrophotographic photoreceptor according to this embodiment will be described in detail. FIG. 1 schematically shows a partial cross-section of the electrophotographic photoreceptor 7 according to this embodiment. The electrophotographic photoreceptor 7 shown in FIG. 1 includes, for example, a conductive substrate 3, and a single-layer photosensitive layer 2 is provided as the outermost layer on the conductive substrate 3. Note that other layers may be provided as necessary. Examples of other layers include an undercoat layer provided between the conductive substrate 3 and the single-layer photosensitive layer 2.

[0032] Hereinafter, each layer of the electrophotographic photoreceptor according to this embodiment will be described in detail. Note that reference numerals will be omitted in the description.

[0033] (Conductive substrate) Examples of the conductive substrate include a metal plate, a metal drum, and a metal belt containing a metal (such as aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or an alloy (such as stainless steel). Further, examples of the conductive substrate include paper, a resin film, a belt, etc. coated, vapor-deposited, or laminated with a conductive compound (such as a conductive polymer, indium oxide, etc.), a metal (such as aluminum, palladium, gold, etc.), or an alloy. Here, "conductive" means that the volume resistivity is less than 10 13 Ωcm.

[0034] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center line average roughness Ra of 0.04 μm or more and 0.5 μm or less for the purpose of suppressing interference fringes generated when irradiating laser light. When non-interference light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is more suitable for longer life in order to suppress the occurrence of defects due to the unevenness of the surface of the conductive substrate.

[0035] Examples of the roughening method include wet honing performed by suspending an abrasive in water and spraying it onto the support, centerless grinding in which the conductive substrate is pressed against a rotating grindstone and continuously ground, anodic oxidation treatment, etc.

[0036] Examples of the roughening method also include a method in which, without roughening the surface of the conductive substrate, a conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the layer is roughened by the particles dispersed therein.

[0037] The roughening treatment by anodic oxidation forms an oxide film on the surface of a conductive substrate made of metal (for example, made of aluminum) as an anode in an electrolyte solution by anodic oxidation. Examples of the electrolyte solution include a sulfuric acid solution and an oxalic acid solution. However, the porous anodic oxide film formed by anodic oxidation is chemically active in its original state, is easily contaminated, and has a large resistance variation due to the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film by blocking the micropores of the oxide film with volume expansion by a hydration reaction in pressurized steam or boiling water (a metal salt such as nickel may be added) to change it into a more stable hydrated oxide.

[0038] The film thickness of the anodic oxide film is preferably, for example, 0.3 μm or more and 15 μm or less. When the film thickness is within the above range, the barrier property against injection tends to be exhibited, and the increase in the residual potential due to repeated use tends to be suppressed.

[0039] The conductive substrate may be treated with an acidic treatment solution or boehmite treatment. The treatment with an acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The mixing ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution are, for example, in the range of 10% by mass or more and 11% by mass or less for phosphoric acid, 3% by mass or more and 5% by mass or less for chromic acid, and 0.5% by mass or more and 2% by mass or less for hydrofluoric acid, and the concentration of these acids as a whole 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 of the coating is preferably 0.3 μm or more and 15 μm or less.

[0040] The boehmite treatment is carried out, for example, by immersing in pure water at 90°C or more and 100°C or less for 5 to 60 minutes, or by bringing into contact with heated steam at 90°C or more and 120°C or less for 5 to 60 minutes. The film thickness of the coating is preferably 0.1 μm or more and 5 μm or less. This may be further subjected to anodic oxidation treatment using an electrolyte solution with low film solubility such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, citrate, etc.

[0041] (Single-layer photosensitive layer) The single-layer photosensitive layer contains a binder resin, a charge generation material, a hole transport material, and an electron transport material. The single-layer photosensitive layer may contain other additives as necessary. Hereinafter, each component contained in the single-layer photosensitive layer will be described in detail.

[0042] - Binder resin - The binder resin is not particularly limited. For example, it includes polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polysilane, and the like. These binder resins may be used alone or in combination of two or more.

[0043] Among the binder resins, from the viewpoints of improving abrasion resistance and suppressing the generation of color spots, polycarbonate resin is preferable, and in particular, a polycarbonate resin containing at least one of a structural unit represented by the following general formula (PCA) and a structural unit represented by the following general formula (PCB) is preferable.

[0044] [Chemical formula]

[0045] In the general formulas (PCA) and (PCB), R P1 , R P2 , R P3 , and R P4 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an aryl group having 6 to 12 carbon atoms. X P1represents a phenylene group, a biphenylene group, a naphthylene group, an alkylene group, or a cycloalkylene group.

[0046] In general formulas (PCA) and (PCB), R P1 , R P2 , R P3 , and R P4 Examples of the alkyl group represented by include linear or branched alkyl groups having 1 to 6 carbon atoms (preferably 1 to 3 carbon atoms). Specific examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, and the like. Specific examples of the branched alkyl group include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, and the like. Among these, lower alkyl groups such as a methyl group and an ethyl group are preferred as the alkyl group.

[0047] In general formulas (PCA) and (PCB), R P1 , R P2 , R P3 , and R P4 Examples of the cycloalkyl group represented by include cyclopentyl, cyclohexyl, and cycloheptyl.

[0048] In general formulas (PCA) and (PCB), R P1 , R P2 , R P3 , and R P4 Examples of the aryl group represented by include a phenyl group, a naphthyl group, a biphenylyl group, and the like.

[0049] In general formulas (PCA) and (PCB), the alkylene group represented by X P1 includes linear or branched alkylene groups having 1 to 12 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms). Specific examples of the linear alkylene group include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, an n-octylene group, an n-nonylene group, an n-decylene group, an n-undecylene group, an n-dodecylene group, and the like. Specific examples of the branched alkylene group include an isopropylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, an isopentylene group, a neopentylene group, a tert-pentylene group, an isohexylene group, a sec-hexylene group, a tert-hexylene group, an isoheptylene group, a sec-heptylene group, a tert-heptylene group, an isooctylene group, a sec-octylene group, a tert-octylene group, an isononylene group, a sec-nonylene group, a tert-nonylene group, an isodecylene group, a sec-decylene group, a tert-decylene group, an isoundecylene group, a sec-undecylene group, a tert-undecylene group, a neoundecylene group, an isododecylene group, a sec-dodecylene group, a tert-dodecylene group, a neododecylene group, and the like. Among these, as the alkylene group, lower alkyl groups such as a methylene group, an ethylene group, and a butylene group are preferable.

[0050] In the general formulas (PCA) and (PCB), X P1 Examples of the cycloalkylene group represented by include cycloalkylene groups having 3 to 12 carbon atoms (preferably 3 to 10 carbon atoms, more preferably 5 to 8 carbon atoms). Specific examples of the cycloalkylene group include a cyclopropylene group, a cyclopentylene group, a cyclohexylene group, a cyclooctylene group, a cyclododecanylene group, and the like. Among these, as the cycloalkylene group, a cyclohexylene group is preferable.

[0051] In the general formulas (PCA) and (PCB), R P1 , R P2 , R P3 , R P4 , and X P1Each of the above substituents represented by [has] further includes a group having a substituent. Examples of this substituent include, for example, a halogen atom (e.g., a fluorine atom, a chlorine atom), an alkyl group (e.g., an alkyl group having 1 to 6 carbon atoms), a cycloalkyl group (e.g., a cycloalkyl group having 5 to 7 carbon atoms), an alkoxy group (e.g., an alkoxy group having 1 to 4 carbon atoms), an aryl group (e.g., a phenyl group, a naphthyl group, a biphenylyl group, etc.).

[0052] In the general formula (PCA), R P1 , and R P2 preferably each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R P1 , and R P2 more preferably represents a hydrogen atom. In the general formula (PCB), R P3 , and R P4 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and X P1 preferably represents an alkylene group or a cycloalkylene group.

[0053] Specific examples of the structural unit represented by the general formula (PCA) and the structural unit represented by the general formula (PCB) include, for example, the following, but are not limited thereto.

[0054] JPEG0007711408000005.jpg83164

[0055] Furthermore, the binder resin is more preferably a polycarbonate resin containing both the structural unit represented by the general formula (PCA) and the structural unit represented by the general formula (PCB).

[0056] Specific examples of the polycarbonate resin containing both the structural unit represented by the general formula (PCA) and the structural unit represented by the general formula (PCB) include, for example, the following, but are not limited thereto. In the exemplified compounds, pm and pn indicate the copolymerization ratio.

[0057] [Chemical]

[0058] In a polycarbonate resin containing both a structural unit represented by general formula (PCA) and a structural unit represented by general formula (PCB), the content (copolymerization ratio) of the structural unit represented by general formula (PCA) is preferably in the range of 5 mol% or more and 95 mol% or less, more preferably 5 mol% or more and 50 mol% or less, and even more preferably 15 mol% or more and 30 mol% or less, based on all the structural units constituting the polycarbonate resin, from the viewpoint of enhancing the abrasion resistance of the photosensitive layer (charge transport layer). Specifically, among the above-exemplified compounds of the polycarbonate resin, pm and pn represent the copolymerization ratio (molar ratio), and examples of the range include pm:pn = 95:5 to 5:95, 50:50 to 5:95, and more preferably 15:85 to 30:70.

[0059] When a polycarbonate resin containing at least one of the structural unit represented by general formula (PCA) and the structural unit represented by general formula (PCB) is used in combination with another binder resin, the content of the other binder resin is preferably 10% by mass or less (more preferably 5% by mass or less) based on all the binder resins.

[0060] The content of the binder resin in the total solid content of the photosensitive layer is preferably 35% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 35% by mass or less.

[0061] From the viewpoints of improving abrasion resistance and suppressing the generation of color spots, the binder resin described above preferably has the following aspects. 1) An aspect in which a homopolymer-type polycarbonate resin having a weight average molecular weight of 20,000 or more and 70,000 or less and having only the structural unit represented by general formula (PCB) is contained in an amount of 40% by mass or more and 60% by mass or less with respect to the photosensitive layer 2) A mixture of a copolymer polycarbonate resin having a weight average molecular weight of 40,000 or more and 60,000 or less and containing both a structural unit represented by the general formula (PCA) and a structural unit represented by the general formula (PCB), and a homopolymer polycarbonate resin having a weight average molecular weight of 20,000 or more and 40,000 or less and having only a structural unit represented by the general formula (PCB), in a mass ratio (copolymer polycarbonate resin / homopolymer polycarbonate resin), and containing 40% by mass or more and 55% by mass or more with respect to the photosensitive layer

[0062] The weight average molecular weight is measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed using a Tosoh GPC·HLC-8120 as a measurement device, a Tosoh column·TSKgel SuperHM-M (15 cm), and a THF solvent. The weight average molecular weight and the number average molecular weight are calculated using a molecular weight calibration curve prepared from this measurement result with a monodisperse polystyrene standard sample.

[0063] - Charge generation material - Examples of the charge generation material include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthraquinone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; trigonal selenium, etc.

[0064] Among these, in order to correspond to laser exposure in the near-infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generation material. Specifically, for example, hydroxygallium phthalocyanine disclosed in JP-A-5-263007, chlorogallium phthalocyanine disclosed in JP-A-5-279591, etc.; dichlorotin phthalocyanine disclosed in JP-A-5-140472, JP-A-5-140473, etc.; titanyl phthalocyanine disclosed in JP-A-4-189873, etc. are more preferable.

[0065] On the one hand, in order to cope with near-ultraviolet laser exposure, as the charge generation material, condensed aromatic pigments such as dibromoanthraquinone; thioindigo-based pigments; porphyrazine compounds; zinc oxide; trigonal selenium; bisazo pigments disclosed in JP-A-2004-78147 and JP-A-2005-181992 are preferable.

[0066] That is, as the charge generation material, for example, when using a light source with an exposure wavelength of 380 nm or more and 500 nm, inorganic pigments are preferable, and when using a light source with an exposure wavelength of 700 nm or less and 800 nm, metal and metal-free phthalocyanine pigments are preferable.

[0067] Here, as the charge generation material, from the viewpoint of enhancing the sensitivity of the single-layer photoreceptor, at least one selected from hydroxygallium phthalocyanine pigment and chlorogallium phthalocyanine pigment is preferable, and hydroxygallium phthalocyanine pigment is more preferable.

[0068] The hydroxygallium phthalocyanine pigment is not particularly limited, but a V-type hydroxygallium phthalocyanine pigment is good. In particular, as the hydroxygallium phthalocyanine pigment, for example, in the spectral absorption spectrum in the wavelength range of 600 nm or more and 900 nm or less, a hydroxygallium phthalocyanine pigment having a maximum peak wavelength in the range of 810 nm or more and 839 nm or less is desirable from the viewpoint of obtaining better dispersibility. When used as a material for an electrophotographic photoreceptor, it is easier to obtain excellent dispersibility, sufficient sensitivity, chargeability, and dark decay characteristics.

[0069] Further, the hydroxygallium phthalocyanine pigment having a maximum peak wavelength in the range of 810 nm or more and 839 nm or less preferably has an average particle size in a specific range and a BET specific surface area in a specific range. Specifically, it is desirable that the average particle size is 0.20 μm or less, more preferably 0.01 μm or more and 0.15 μm or less. On the other hand, the BET specific surface area is preferably 45 m 2 / g or more, preferably 50 m 2It is more desirable that it be 55 m / g or more. 2 120 m / g or more and 55 m / g or less is particularly desirable. The average particle size is the value measured by a laser diffraction scattering type particle size distribution measuring device (LA-700, manufactured by Horiba, Ltd.) in terms of volume average particle size (d50 average particle size). Further, it is the value measured by the nitrogen substitution method using a BET type specific surface area measuring instrument (manufactured by Shimadzu Corporation: Flow-Sorb II 2300). 2 Here, when the average particle size is larger than 0.20 μm, or when the specific surface area value is less than 45 m / g, the pigment particles tend to be coarsened or aggregates of the pigment particles tend to be formed, and defects are likely to occur in properties such as dispersibility, sensitivity, chargeability, and dark attenuation characteristics, which may cause image quality defects. Here, when the average particle size is larger than 0.20 μm, or when the specific surface area value is less than 45 m / g, 2 Here, when the average particle size is larger than 0.20 μm, or when the specific surface area value is less than 45 m / g, the pigment particles tend to be coarsened or aggregates of the pigment particles tend to be formed, and defects are likely to occur in properties such as dispersibility, sensitivity, chargeability, and dark attenuation characteristics, which may cause image quality defects.

[0070] The maximum particle size (the maximum value of the primary particle size) of the hydroxygallium phthalocyanine pigment is desirably 1.2 μm or less, more desirably 1.0 μm or less, and even more desirably 0.3 μm or less. When such a maximum particle size exceeds the above range, black spots are likely to occur.

[0071] From the viewpoint of suppressing density unevenness caused by exposure of the photoreceptor to a fluorescent lamp or the like, the hydroxygallium phthalocyanine pigment has an average particle size of 0.2 μm or less, a maximum particle size of 1.2 μm or less, and a specific surface area value of 45 m / g or more. 2 is desirable.

[0072] The hydroxygallium phthalocyanine pigment is desirably of a V type having diffraction peaks at Bragg angles (2θ ± 0.2°) of at least 7.3°, 16.0°, 24.9°, and 28.0° in an X-ray diffraction spectrum using CuKα characteristic X-rays.

[0073] On the other hand, as the chlorogallium phthalocyanine pigment, for example, it is desirable that it has diffraction peaks at Bragg angles (2θ ± 0.2°) of 7.4°, 16.6°, 25.5°, and 28.3°, which provides excellent sensitivity as an electrophotographic photoreceptor material. The maximum peak wavelength, average particle size, maximum particle size, and specific surface area value of the preferred spectral absorption spectrum of chlorogallium phthalocyanine pigment are the same as those of hydroxygallium phthalocyanine pigment.

[0074] The content of the charge generation material with respect to the total solid content of the photosensitive layer is preferably 1% by mass or more and 5% by mass or less, more preferably 1.2% by mass or more and 4.5% by mass or less.

[0075] - Hole transport material - The hole transport material is not particularly limited. For example, oxadiazole derivatives such as 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole; pyrazoline derivatives such as 1,3,5-triphenyl-pyrazoline, 1-[pyridyl-(2)]-3-(p-diethylaminostyryl)-5-(p-diethylaminostyryl)pyrazoline; aromatic tertiary amino compounds such as triphenylamine, N,N′-bis(3,4-dimethylphenyl)biphenyl-4-amine, tri(p-methylphenyl)aminyl-4-amine, dibenzylaniline; aromatic tertiary diamino compounds such as N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine, 1,2,4-triazine derivatives such as 3-(4′-dimethylaminophenyl)-5,6-di-(4′-methoxyphenyl)-1,2,4-triazine; hydrazone derivatives such as 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone; quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline; benzofuran derivatives such as 6-hydroxy-2,3-di(p-methoxyphenyl)benzofuran; α-stilbene derivatives such as p-(2,2-diphenylvinyl)-N,N-diphenylaniline; enamine derivatives; carbazole derivatives such as N-ethylcarbazole; poly-N-vinylcarbazole and its derivatives; polymers having a group composed of the above-mentioned compounds in the main chain or side chain; and the like. These hole transport materials may be used alone or in combination of two or more.

[0076] Among these, as the hole transport material, the hole transport material represented by the following general formula (HT1) and the hole transport material represented by the following general formula (HT1a) are preferably mentioned. In particular, from the viewpoints of improving abrasion resistance and suppressing the generation of color spots, as the hole transport material, a hole transport material having a benzidine skeleton is preferable, and a hole transport material represented by the following general formula (HT1a) is more preferable.

[0077]

Chemical formula

[0078] In the general formula (HT1), Ar T1 , Ar T2 , and Ar T3 each independently represents an aryl group or -C6H4-C(R T4 )=C(R T5 )(R T6 ). R T4 , R T5 , and R T6 each independently represents a hydrogen atom, an alkyl group, or an aryl group. R T5 and R T6 may combine to form a hydrocarbon ring structure.

[0079] In the general formula (HT1), as the aryl group represented by Ar T1 , Ar T2 , and Ar T3 , an aryl group having 6 to 15 carbon atoms (preferably 6 to 9 carbon atoms, more preferably 6 to 8 carbon atoms) can be mentioned. Specific examples of the aryl group include a phenyl group, a naphthyl group, a fluorene group, etc. Among these, as the aryl group, a phenyl group is preferable.

[0080] In the general formula (HT1), as the alkyl group represented by R T4 , R T5 , and R T6 , in the general formula (HT1a) described later, R C21 , R C22 , and RC23 This is the same as the example of the alkyl group represented by it, and the preferable range is also the same.

[0081] In the general formula (HT1), R T4 , R T5 , and R T6 As the aryl group represented by, for example, Ar T1 , Ar T2 , and Ar T3 This is the same as the example of the aryl group represented by it, and the preferable range is also the same.

[0082] In addition, in the general formula (HT1), Ar T1 , Ar T2 , and Ar T3 , and also, R T4 , R T5 , and R T6 Each of the above substituents represented by further includes a group having a substituent. Examples of this substituent include a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an aryl group having 6 to 10 carbon atoms, and the like. In addition, examples of the substituent of each of the above substituents also include a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0083] The triarylamine-based hole transport material (HT1) may be used alone or in combination of two or more.

[0084] Here, from the viewpoint of charge mobility, among the triarylamine-based hole transport materials represented by the general formula (HT1), in particular, a triarylamine-based hole transport material having "-C6H4-C(R T4 )=C(R T5 )(R T6 )" is preferable. Among them, the triarylamine-based hole transport material represented by the specific example (HT1-4) of the triarylamine-based hole transport material (HT1) described later is preferable.

[0085]

Chemical Formula

[0086] In the general formula (HT1a), R C21 , R C22 , and R C23 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms.

[0087] In the general formula (HT1a), examples of the halogen atom represented by R C21 , R C22 , and R C23 include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. Among these, as the halogen atom, a fluorine atom and a chlorine atom are preferable, and a chlorine atom is more preferable.

[0088] In the general formula (HT1a), examples of the alkyl group represented by R C21 , R C22 , and R C23 include linear or branched alkyl groups having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms). Specific examples of the linear alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, etc. Specific examples of the branched alkyl group include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, etc. Among these, as the alkyl group, lower alkyl groups such as a methyl group, an ethyl group, and an isopropyl group are preferable.

[0089] In the general formula (HT1a), R C21 , R C22and R C23 Examples of the alkoxy group represented by R include linear or branched alkoxy groups having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms). Specific examples of the linear alkoxy group include methoxy group, ethoxy group, n-propoxy group, n-butoxy group, n-pentyloxy group, n-hexyloxy group, n-heptyloxy group, n-octyloxy group, n-nonyloxy group, n-decyloxy group, and the like. Specific examples of the branched alkoxy group include isopropoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, isopentyloxy group, neopentyloxy group, tert-pentyloxy group, isohexyloxy group, sec-hexyloxy group, tert-hexyloxy group, isoheptyloxy group, sec-heptyloxy group, tert-heptyloxy group, isooctyloxy group, sec-octyloxy group, tert-octyloxy group, isononyloxy group, sec-nonyloxy group, tert-nonyloxy group, isodecyloxy group, sec-decyloxy group, tert-decyloxy group, and the like. Among these, the methoxy group is preferred as the alkoxy group.

[0090] In the general formula (HT1a), R C21 , R C22 , and R C23 Examples of the aryl group represented by R include aryl groups having 6 to 10 carbon atoms (preferably 6 to 9 carbon atoms, more preferably 6 to 8 carbon atoms). Specific examples of the aryl group include phenyl group, naphthyl group, and the like. Among these, the phenyl group is preferred as the aryl group.

[0091] In the general formula (HT1a), R C21 , R C22 , and R C23Each of the above substituents represented by [substituent] further includes a group having a substituent. Examples of this substituent include the atoms and groups exemplified above (for example, a halogen atom, an alkyl group, an alkoxy group, an aryl group, etc.).

[0092] The triarylamine-based hole transport material represented by the general formula (HT1) may be used alone or in combination of two or more.

[0093] Hereinafter, specific examples (HT1-1) to (HT1-10) of the triarylamine-based hole transport material (HT1) and the benzidine-based hole transport material (HT1a) are shown, but the present invention is not limited thereto.

[0094]

Chemical formula

[0095]

Chemical formula

[0096]

Chemical formula

[0097]

Chemical formula

[0098] From the viewpoints of high photosensitivity and suppression of the generation of black spots, the content of the hole transport material with respect to the total solid content of the photosensitive layer is preferably 20% by mass or more and 45% by mass or less, more preferably 34% by mass or more and 44% by mass or less, still more preferably 38% by mass or more and 44% by mass or less, and even more preferably 38% by mass or more and 42% by mass or less.

[0099] Further, from the viewpoints of high photosensitivity and suppression of the generation of black spots, the mass ratio of the hole transport material to the electron transport material (hole transport material / electron transport material) is preferably 19 / 5 or more and 28 / 5 or less, more preferably 20 / 5 or more and 26 / 5 or less, and even more preferably 21 / 5 or more and 24 / 5 or less.

[0100] - Electron transport material - The electron transport material is not particularly limited. For example, quinone compounds such as chloranil and bromanil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, and octyl 9-dicyanomethylene-9-fluorenone-4-carboxylate; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)1,3,4-oxadiazole; xanthone compounds; thiophene compounds; dinaphthoquinone compounds such as 3,3'-di-tert-pentyl-dinaphthoquinone; diphenoquinone compounds such as 3,3'-di-tert-butyl-5,5'-dimethyl diphenoquinone and 3,3',5,5'-tetra-tert-butyl-4,4'-diphenoquinone; polymers having a group composed of the above-described compounds in the main chain or side chain; and the like. These electron transport materials may be used alone or in combination of two or more.

[0101] Among these, from the viewpoints of improving abrasion resistance and suppressing the generation of color spots, as the electron transport material, an electron transport material having a diphenoquinone skeleton is preferable, and an electron transport material represented by the following general formula (FK) is more preferable.

[0102]

Chemical formula

[0103] R k1 and R k3 are each independently preferably an alkyl group having 3 to 12 carbon atoms, an alkoxy group having 3 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group from the viewpoint of suppressing cracking of the photosensitive layer accompanying crystallization of the electron transport material, more preferably a branched alkyl group having 3 to 12 carbon atoms, a branched alkoxy group having 3 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group, still more preferably a branched alkyl group having 3 to 8 carbon atoms or a branched alkoxy group having 3 to 8 carbon atoms, and particularly preferably a t-butyl group. Also, R k1 and R k3 are preferably the same group.

[0104] R k2 and R k4 are each independently preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a linear alkoxy group having 1 to 4 carbon atoms, still more preferably a linear alkyl group having 1 to 3 carbon atoms or a linear alkoxy group having 1 to 3 carbon atoms, and particularly preferably a methyl group. Also, R k2 and R k4 are preferably the same group. Furthermore, R k1 and R k2 are preferably different groups, and also R k3 and R k4 are preferably different groups.

[0105] Examples of the electron transport material represented by the general formula (FK) are shown below, but are not limited thereto. The following example compound numbers are hereinafter denoted as "exemplary compound (1-number)". Specifically, for example, exemplary compound 5 is hereinafter denoted as "exemplary compound (1-5)".

[0106]

Chemical formula

[0107] In addition, the abbreviations and the like in the above exemplary compounds have the following meanings. ·t-C4H9: t-butyl group ·CH3O: methoxy group ·t-C4H9O: t-butoxy group ·c-C6H 12 : cyclohexyl group ·C6H5: phenyl group ·C6H5CH2: benzyl group

[0108] The content of the electron transport material with respect to the total solid content of the photosensitive layer is preferably 4% by mass or more and 20% by mass or less, more preferably 6% by mass or more and 18% by mass or less, and still more preferably 8% by mass or more and 16% by mass or less.

[0109] -Other additives- The single-layer photosensitive layer may contain well-known other additives such as antioxidants, light stabilizers, and heat stabilizers. Further, when the single-layer photosensitive layer is a surface layer, it may contain fluororesin particles, silicone oil, and the like.

[0110] -Formation of single-layer photosensitive layer- The single-layer photosensitive layer is formed using a coating solution for forming a photosensitive layer in which the above components are added to a solvent. Examples of the solvent include ordinary organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride; and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents can be used alone or in combination of two or more.

[0111] As a method for dispersing particles (for example, a charge generation material) in the coating liquid for forming the photosensitive layer, media dispersers such as a ball mill, a vibration ball mill, an attritor, a sand mill, and a horizontal sand mill, and media-less dispersers such as stirring, an ultrasonic disperser, a roll mill, and a high-pressure homogenizer are used. Examples of the high-pressure homogenizer include a collision method in which the dispersion liquid is dispersed by causing liquid-liquid collision or liquid-wall collision in a high-pressure state, and a penetration method in which the dispersion liquid is dispersed by passing through a fine flow path in a high-pressure state.

[0112] Examples of the method for applying the coating liquid for forming the photosensitive layer onto the undercoat layer include a dipping coating method, a pushing-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a knife coating method, and a curtain coating method.

[0113] The film thickness of the single-layer photosensitive layer is preferably set in the range of 5 μm or more and 60 μm or less, more preferably 5 μm or more and 50 μm or less, and still more preferably 10 μm or more and 40 μm or less.

[0114] [Image forming apparatus (and process cartridge)] The image forming apparatus according to the present embodiment includes an electrophotographic photoreceptor, a charging device that charges the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, and a transfer device that transfers the toner image onto the surface of a recording medium. And, as the electrophotographic photoreceptor, the electrophotographic photoreceptor according to the present embodiment is applied.

[0115] The image forming apparatus according to the present embodiment includes: an apparatus having a fixing device for fixing a toner image transferred onto the surface of a recording medium; an apparatus of a direct transfer method for directly transferring a toner image formed on the surface of an electrophotographic photoreceptor onto a recording medium; an apparatus of an intermediate transfer method for primarily transferring a toner image formed on the surface of an electrophotographic photoreceptor onto the surface of an intermediate transfer member and secondarily transferring the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium; an apparatus having a cleaning device for cleaning the surface of the electrophotographic photoreceptor after transfer of the toner image and before charging; an apparatus having a discharging device for discharging the surface of the electrophotographic photoreceptor by irradiating it with discharging light after transfer of the toner image and before charging; an apparatus having an electrophotographic photoreceptor heating member for raising the temperature of the electrophotographic photoreceptor and reducing the relative humidity, etc. Well-known image forming apparatuses are applicable.

[0116] In the case of an apparatus of the intermediate transfer method, the transfer device has, for example, a configuration including an intermediate transfer member onto which a toner image is transferred on the surface, a primary transfer device for primarily transferring a toner image formed on the surface of an electrophotographic photoreceptor onto the surface of the intermediate transfer member, and a secondary transfer device for secondarily transferring the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium.

[0117] The image forming apparatus according to the present embodiment may be either a dry developing method image forming apparatus or a wet developing method (developing method using a liquid developer) image forming apparatus.

[0118] In the image forming apparatus according to the present embodiment, for example, the portion including the electrophotographic photoreceptor may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photoreceptor according to the present embodiment is preferably used. Note that the process cartridge may include at least one selected from the group consisting of a charging device, an electrostatic latent image forming device, a developing device, and a transfer device, in addition to the electrophotographic photoreceptor.

[0119] Hereinafter, an example of the image forming apparatus according to the present embodiment is shown, but it is not necessarily limited thereto. Note that the main parts shown in the drawings are described, and the description of the others is omitted.

[0120] FIG. 2 is a schematic configuration diagram showing an example of the image forming apparatus according to the present embodiment. As shown in FIG. 2, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming device), and a transfer device 40 (an example of a transfer device). In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, and the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 via a recording medium conveyance belt 50.

[0121] The process cartridge 300 in FIG. 2 integrally supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging device), a developing device 11 (an example of a developing device), and a cleaning device 13 (an example of a cleaning device) in a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, and the cleaning blade 131 is disposed so as to contact the surface of the electrophotographic photoreceptor 7. Note that the cleaning member may be a conductive or insulating fibrous member or a cleaning roll made of a foamed resin instead of the form of the cleaning blade 131, and this may be used alone or in combination with the cleaning blade 131.

[0122] Note that FIG. 2 shows an example including a fibrous member 132 (roll shape) that supplies a lubricant 14 to the surface of the electrophotographic photoreceptor 7 and a fibrous member 133 (flat brush shape) that assists cleaning as the image forming apparatus, but these are disposed as necessary.

[0123] Hereinafter, each configuration of the image forming apparatus according to the present embodiment will be described.

[0124] - Charging device - As the charging device 8, for example, a contact charger using a conductive or semiconductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. is used. Further, a non-contact type roller charger, a known charger such as a scorotron charger or a corotron charger using corona discharge, etc. are also used.

[0125] -Exposure device- As the exposure device 9, for example, optical system devices that expose light such as semiconductor laser light, LED light, liquid crystal shutter light, etc. to the surface of the electrophotographic photoreceptor 7 in a defined image-like manner can be mentioned. The wavelength of the light source is within the spectral sensitivity region of the electrophotographic photoreceptor. As the wavelength of the semiconductor laser, near-infrared having an oscillation wavelength around 780 nm is the mainstream. However, it is not limited to this wavelength, and lasers with oscillation wavelengths in the 600 nm range or blue lasers with oscillation wavelengths of 400 nm or more and 450 nm or less may also be used. Further, for color image formation, a surface-emitting type laser light source of a type that can output multi-beams is also effective.

[0126] -Developing device- As the developing device 11, for example, general developing devices that develop by bringing the developer into contact or non-contact can be mentioned. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and is selected according to the purpose. For example, known developers having a function of attaching a one-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, a roller, etc. can be mentioned. Among these, the developing device 11 preferably has a developing roll that holds the developer and conveys it to the developing area (for example, the area facing the electrophotographic photoreceptor).

[0127] In particular, in the developing device 11, the difference (absolute value) in Young's modulus between the photosensitive layer of the electrophotographic photoreceptor and the surface of the developing roll is preferably 3000 or more and 6000 or less, more preferably 3500 or more and 5000 or less, and even more preferably 4000 or more and 4600 or less. When the difference (absolute value) in Young's modulus between the photosensitive layer (its surface) of the electrophotographic photoreceptor and the surface of the developing roll is 3785 or more and 4675 or less, the photosensitive layer is appropriately worn by the developing roll, and deposits (such as paper dust) are easily cleaned. While wear is suppressed, the generation of color spots is further suppressed.

[0128] From the viewpoint of improving wear resistance and suppressing the generation of color spots, the Young's modulus with respect to the surface of the developing roll is preferably 110 MPa or more and 210 MPa or less, and more preferably 150 MPa or more and 170 MPa or less. The developing roll has, for example, a cylindrical developing sleeve (such as a metal cylindrical tube, a ceramic cylindrical tube, a resin cylindrical tube, etc.) arranged rotatably, and a magnet roll arranged inside the developing sleeve. Further, it may have an elastic body layer made of oil-resistant rubber or the like on a metallic roller substrate, and a conductive layer on this elastic body layer. And the Young's modulus of the surface of the developing roll can be adjusted by the material of the outermost layer member. To make the Young's modulus of the surface of the developing roll within the above range, it is preferable to adopt a developing roll having an elastic body layer and a conductive layer on a metallic roller substrate. The Young's modulus of the surface of the developing roll is measured in the same manner as the measuring method of the Young's modulus of the photosensitive layer.

[0129] The developer used in the developing device 11 may be a one-component developer consisting of toner alone, or a two-component developer containing toner and carrier. Further, the developer may be magnetic or non-magnetic. Well-known ones are applicable to these developers.

[0130] - Cleaning device - As the cleaning device 13, a cleaning blade type device including a cleaning blade 131 is used. In addition to the cleaning blade method, a fur brush cleaning method or a simultaneous development and cleaning method may be adopted.

[0131] - Transfer device - Examples of the transfer device 40 include known transfer chargers such as contact transfer chargers using a belt, roller, film, rubber blade, etc., scorotron transfer chargers using corona discharge, and corotron transfer chargers.

[0132] - Recording medium conveyance belt - As the recording medium conveyance belt 50, a belt-shaped one (intermediate transfer belt) containing polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. with semiconductive properties is used.

[0133] FIG. 3 is a schematic configuration diagram showing another example of the image forming apparatus according to the present embodiment. The image forming apparatus 120 shown in FIG. 3 is a tandem type full-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, four process cartridges 300 are arranged in parallel on the intermediate transfer member 50, and one electrophotographic photoreceptor is used for each color. Note that the image forming apparatus 120 has the same configuration as the image forming apparatus 100 except that it is of the tandem type.

Examples

[0134] Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to the following examples at all. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass".

[0135] <Examples 1 to 21, Comparative Examples 1 to 6> - Production of coating liquid for forming photosensitive layer - A mixture of the binder resin shown in Table 1, the charge generation material shown in Table 1 ("CGM" in Table 1), the hole transport material shown in Table 1 ("HTM" in Table 1), the electron transport material shown in Table 1 ("ETM" in Table 1), and an amount of tetrahydrofuran corresponding to the solid content concentration shown in Table 1 was dispersed with a high-pressure homogenizer to obtain a coating liquid for forming a photosensitive layer.

[0136] - Formation of photosensitive layer - As a conductive substrate, an aluminum substrate with a diameter of 30 mm, a length of 244.5 mm, and a wall thickness of 0.75 mm was prepared. Next, under the photosensitive layer formation conditions shown in Table 1, the coating solution for forming the photosensitive layer was applied onto the aluminum substrate by the dip coating method, followed by drying and curing to form a single-layer photosensitive layer with a thickness of 35 μm on the aluminum substrate.

[0137] Thus, the photoreceptors of each example were obtained.

[0138] <Properties> Regarding the following properties of the photoreceptors of each example, measurements were carried out according to the methods described above. · Martens hardness of the photosensitive layer · Young's modulus of the photosensitive layer · Elastic deformation rate of the photosensitive layer

[0139] <Evaluation> Using the photoreceptors of each example, the following evaluations were carried out.

[0140] (Wear amount) The photoreceptors of each example were installed in the image forming apparatus "HL-L6400DW manufactured by Brother". However, the Young's modulus of the developing roll was made as shown in Table 1 by changing the material of the developing sleeve. Then, using the image forming apparatus, 20,000 sheets of 50% halftone images were printed on A4 paper. Then, using an eddy current type film thickness gauge, the film thickness of the photosensitive layer before installation and the film thickness of the photosensitive layer after printing were measured, and the difference was calculated as the wear amount. And when the wear amount was 3 μm or more, it was judged that the wear resistance was low.

[0141] (Color dots) -Image quality evaluation- The photoreceptors of each example printed in the above wear amount evaluation were installed in the image forming apparatus "HL-L6400DW manufactured by Brother", the 20,000th 50% halftone image was observed, and the occurrence status of color dots was evaluated according to the following criteria. Note that for the developing roll of the image forming apparatus, the developing roll with the Young's modulus of the surface shown in Table 1 was adopted. 5: Very good (no color dots) 4: Good (almost no color spots) 3: Normal (there are color spots but within an acceptable range) 2: Bad (there are color spots and it becomes a problem) 1: Very Bad (there are many color spots and it becomes a problem) Note that it is evaluated that there may be practical problems if the evaluation is 2 or less.

[0142]

Table 1-1

[0143]

Table 1-2

[0144] From the above results, it can be seen that the photoreceptor of this example can reduce the wear of the photosensitive layer and suppress the generation of color spots compared with the photoreceptor of the comparative example.

[0145] Note that the abbreviations in Table 1 represent the following compounds. -Binder resin- ·PCZ: Homopolymer polycarbonate resin represented by (P C- 1) (weight average molecular weight Mw = as described in the table) ·BPZ: Copolymer polycarbonate resin represented by (PCB-1) (pm: 25, pn: 75, weight average molecular weight Mw = as described in the table)

[0146] ·PA: Polyarylate resin having a structural unit represented by the following formula (weight average molecular weight Mw = as described in the table)

Chemical formula

[0147] -Charge generation material- · CGM-A: V-type hydroxygallium phthalocyanine. It has diffraction peaks at positions where the Bragg angles (2θ ± 0.2°) of the X-ray diffraction spectrum using CuKα characteristic X-rays are at least 7.3°, 16.0°, 24.9°, and 28.0°. The maximum peak wavelength in the spectral absorption spectrum in the wavelength range from 600 nm to 900 nm is 820 nm, the average particle size is 0.12 μm, the maximum particle size is 0.2 μm, and the BET specific surface area is 60 m 2 / g.

[0148] - Hole transport material - · HTM-A: A compound with the following structure, an exemplary compound (HT1-1) of the hole transport material represented by the general formula (HT1a), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1']biphenyl-4,4'-diamine

Chem.

Chem.

[0149] - Electron transport material - · ETM-A: A compound with the following structure, an exemplary compound (1-1) of the electron transport material represented by the general formula (FK), 3,3'-di-tert-butyl-5,5'-dimethyl diphenoquinone.

Chem.

[0150] · ETM-B: A compound with the following structure

Chem.

Chem.

Explanation of Symbols

[0151] 2 photosensitive layer, 3 conductive substrate, 7 electrophotographic photoreceptor, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 40 transfer device, 50 recording medium conveyance belt, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member, 133 fibrous member, 300 process cartridge

Claims

1. A conductive substrate, A single-layer photosensitive layer provided on the conductive substrate, containing a binder resin, a charge generation material, a hole transport material, and an electron transport material, and having an index A represented by the following formula (1) in the range of -7.98 or more and -7.28 or less, having, The binder resin is a polycarbonate resin, The polycarbonate resin is a copolymerized polycarbonate resin having a weight average molecular weight of 40,000 or more and 60,000 or less and containing both a structural unit represented by the following general formula (PCA) and a structural unit represented by the following general formula (PCB), and a homopolymerized polycarbonate resin having a weight average molecular weight of 20,000 or more and 30,000 or less and having only a structural unit represented by the following general formula (PCB), The electrophotographic photoreceptor, wherein the content of the mixture with respect to the total solid content of the photosensitive layer is 40% by mass or more and 55% by mass or less. 【Chemical 1】 (In the general formulas (PCA) and (PCB), R Ｐ１ , R Ｐ２ , R Ｐ３ , and R Ｐ４ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an aryl group having 6 to 12 carbon atoms. X Ｐ１ represents a phenylene group, a biphenylene group, a naphthylene group, an alkylene group, or a cycloalkylene group.) Formula (1): A = (0.057 × M) - (0.002 × F) - (0.252 × μ) In formula (1), M represents the Martens hardness (N / mm ２ ), F represents the Young's modulus (MPa) of the photosensitive layer, and μ represents the elastic deformation rate (%) of the photosensitive layer.

2. The electrophotographic photoreceptor according to claim 1, wherein the index A is in the range of -7.80 or more and -7.34 or less.

3. The electrophotographic photoreceptor according to claim 1 or claim 2, wherein the mass ratio of the hole transport material to the electron transport material (the hole transport material / the electron transport material) is 42 / 9 or more and 28 / 5 or less.

4. The electrophotographic photoreceptor according to claim 3, wherein the content of the hole transport material with respect to the total solid content of the photosensitive layer is 38% by mass or more and 44% by mass or less.

5. The electrophotographic photoreceptor according to any one of claims 1 to 4, wherein the hole transport material is a hole transport material having a benzidine skeleton.

6. The electrophotographic photoreceptor according to claim 5, wherein the hole transport material having a benzidine skeleton is a hole transport material represented by the following general formula (HT1a). [Chemical 2] (In the general formula (HT1a), R Ｃ２１ , R Ｃ２２ , and R Ｃ２３ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms.)

7. The electrophotographic photoreceptor according to any one of claims 1 to 6, wherein the electron transport material is an electron transport material having a diphenoquinone skeleton.

8. The electrophotographic photoreceptor according to claim 7, wherein the electron transport material having a diphenoquinone skeleton is an electron transport material represented by the following general formula (FK). 【Chemical Formula 3】 (In the general formula (FK), R ｋ１ to R ｋ４ each independently represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group.)

9. The electrophotographic photoreceptor according to any one of claims 1 to 8, wherein the mass ratio of the copolymerized polycarbonate resin to the homopolymerized polycarbonate resin (the copolymerized polycarbonate resin / the homopolymerized polycarbonate resin) is 3 / 7 or more and 7 / 3 or less.

10. The mass ratio of the copolymerized polycarbonate resin to the homopolymerized polycarbonate resin (the copolymerized polycarbonate resin / the homopolymerized polycarbonate resin) is 4 / 6 or more and 7 / 3 or less, and the electrophotographic photoreceptor according to any one of claims 1 to 9.

11. A process cartridge detachably attached to an image forming apparatus, comprising the electrophotographic photoreceptor according to any one of claims 1 to 10.

12. A developing device that develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, further comprising a developing roll that holds the developer and conveys it to a developing region. The process cartridge according to claim 11, wherein the difference (absolute value) in Young's modulus between the photosensitive layer of the electrophotographic photoreceptor and the surface of the developing roll is 3785 or more and 4675 or less.

13. The electrophotographic photoreceptor according to any one of claims 1 to 10, a charging device that charges the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing device that develops an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, a transfer device that transfers the toner image to the surface of a recording medium, and an image forming apparatus comprising the same.

14. The developing device has a developing roll that holds the developer and conveys it to a developing region, The image forming apparatus according to claim 13, wherein the difference (absolute value) in Young's modulus between the photosensitive layer of the electrophotographic photoreceptor and the surface of the developing roll is 3785 or more and 4675 or less.

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