Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that suppresses a decrease in charging potential and has excellent dot reproducibility. 【Solution means】 It includes a conductive substrate, a charge generation layer disposed on the conductive substrate, a charge transport layer disposed on the charge generation layer, and an inorganic protective layer disposed on the charge transport layer. The capacitance per unit area (X1) of the charge transport layer is 0.90×10 -4 , 2 , -5 , 2 , -6 , 2 , 2 (F / m 2 ) or more and 1.90×10 -6 (F / m 2 ) or less, and the capacitance per unit area (X2) of the inorganic protective layer is 2.40×10 -5 (F / m 2 ) or more and 1.10×10 -4 (F / m 2 ) or less. An electrophotographic photoreceptor.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses "an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate containing at least one of an organic charge generating substance, an organic charge transporting substance, and an organic binder resin, wherein when the capacitance of the photosensitive layer is C (pF / cm2) and the film thickness is d (μm), the product of C and d is 3100 or more, and the film thickness of the photosensitive layer is 12 μm or more and 18 μm or less." [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2002-303994 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The object of the present invention is an electrophotographic photoreceptor comprising a conductive substrate, a charge generation layer disposed on the conductive substrate, a charge transport layer disposed on the charge generation layer, and an inorganic protective layer disposed on the charge transport layer, wherein the capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10 -6 (F / m 2 ) less than, or 1.90 × 10 -6 (F / m 2 ) or the capacitance per unit area of ​​the inorganic protective layer (X2) is 2.40 × 10 -5 (F / m 2 ) less than, or 1.10 × 10 -4 (F / m 2 The objective is to provide an electrophotographic photoreceptor that suppresses the decrease in chargeability and exhibits excellent dot reproducibility, compared to cases where the value exceeds the limit. [Means for solving the problem]

[0005] The means for solving the above problems include the following aspects. <1> A conductive substrate, a charge generation layer disposed on the conductive substrate, a charge transport layer disposed on the charge generation layer, and an inorganic protective layer disposed on the charge transport layer, wherein the capacitance per unit area (X1) of the charge transport layer is 0.90×10 -6 (F / m 2 ) or more and 1.90×10 -6 (F / m 2 ) or less, and the capacitance per unit area (X2) of the inorganic protective layer is 2.40×10 -5 (F / m 2 ) or more and 1.10×10 -4 (F / m 2 ) or less. An electrophotographic photoreceptor. <2> The capacitance per unit area (X1) of the charge transport layer is 0.90×10 -6 (F / m 2 ) or more and 1.46×10 -6 (F / m 2 ) or less, and the capacitance per unit area (X2) of the inorganic protective layer is 2.40×10 -5 (F / m 2 ) or more and 5.30×10 -5 (F / m 2 ) or less. The electrophotographic photoreceptor according to <1>. <3> The ratio (X1 / X2) of the capacitance per unit area (X1) of the charge transport layer to the capacitance per unit area (X2) of the inorganic protective layer is 0.010 or more and 0.070 or less. The electrophotographic photoreceptor according to <1> or <2>. <4> The inorganic protective layer is an inorganic protective layer containing oxygen and a Group 13 element. The electrophotographic photoreceptor according to any one of <1> to <3>. <5> The elemental composition ratio (oxygen / group 13 element) of oxygen and the group 13 element in the inorganic protective layer is 1.4 or more and 1.5 or less. The electrophotographic photoreceptor according to any one of <1> to <4>. <6> The charge transport layer contains metal oxide particles, <1> ~ <5> An electrophotographic photoreceptor as described in any one of the items. <7> The aforementioned metal oxide particles are silica particles. <6> The electrophotographic photoreceptor described above. <8> The content of the metal oxide particles in the charge transport layer is 40% by volume or more and 60% by volume or less. <7> The electrophotographic photoreceptor described above. <9> The degree of hydrophobicity of the metal oxide particles in the charge transport layer is 60% or more. <6> The electrophotographic photoreceptor described above <10> The thickness of the charge transport layer is 16 μm or more and 30 μm or less. <1> ~ <9> An electrophotographic photoreceptor as described in any one of the items. <11> The thickness of the inorganic protective layer is 1.0 μm or more and 4.0 μm or less. <1> ~ <10> An electrophotographic photoreceptor as described in any one of the items. <12> <1> ~ <11> A process cartridge comprising an electrophotographic photoreceptor as described in any one of the items, which is attached to and detached from an image forming apparatus. <13> <1> ~ <11> An image forming apparatus comprising: an electrophotographic photoreceptor as described in any one of the above; a charging device for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing 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 for transferring the toner image to the surface of a recording medium. [Effects of the Invention]

[0006] <1> According to the invention, an electrophotographic photobody comprising a conductive substrate, a charge generation layer disposed on the conductive substrate, a charge transport layer disposed on the charge generation layer, and an inorganic protective layer disposed on the charge transport layer, wherein the capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10 -6 (F / m 2 ) less than, or 1.90 × 10-6 (F / m 2 ) or the capacitance per unit area of ​​the inorganic protective layer (X2) is 2.40 × 10 -5 (F / m 2 ) less than, or 1.10 × 10 -4 (F / m 2 Compared to cases where the value exceeds the limit, this provides an electrophotographic photoreceptor that suppresses the decrease in chargeability and has excellent dot reproducibility. <2> According to the invention, the capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10 -6 (F / m 2 ) less than, or 1.46 × 10 -6 (F / m 2 ) or the capacitance per unit area of ​​the inorganic protective layer (X2) is 2.40 × 10 -5 (F / m 2 ) less than, or 5.30 × 10 -5 (F / m 2 Compared to cases where the value exceeds the limit, this provides an electrophotographic photoreceptor that suppresses the decrease in chargeability and has excellent dot reproducibility. <3> According to the present invention, compared to cases where the ratio (X1 / X2) of the capacitance per unit area of ​​the charge transport layer (X1) to the capacitance per unit area of ​​the inorganic protective layer (X2) is less than 0.010 or greater than 0.070, an electrophotographic photoreceptor is provided that suppresses the decrease in chargeability and has excellent dot reproducibility. <4> According to the invention, compared to cases where the inorganic protective layer is not an inorganic protective layer containing oxygen and group 13 elements, an electrophotographic photoreceptor is provided that suppresses a decrease in chargeability and has excellent dot reproducibility. <5> According to the invention, compared to cases where the elemental composition ratio (oxygen / group 13 element) of oxygen and group 13 elements in the inorganic protective layer is less than 1.4 or greater than 1.5, an electrophotographic photoreceptor is provided that suppresses the decrease in chargeability and has excellent dot reproducibility. <6> According to the invention, an electrophotographic photoreceptor is provided that suppresses the decrease in chargeability and exhibits excellent dot reproducibility compared to a case where the charge transport layer does not contain metal oxide particles. <7> According to the invention, compared to the case where the metal oxide particles are titanium oxide particles, an electrophotographic photoreceptor is provided that suppresses the decrease in chargeability and has excellent dot reproducibility. <8> According to the invention, compared to cases where the content of metal oxide particles in the charge transport layer is less than 40 volume% or more than 60 volume%, an electrophotographic photoreceptor is provided that suppresses the decrease in chargeability and has excellent dot reproducibility. <9> According to the invention, compared to the case where the degree of hydrophobicity of the metal oxide particles is less than 60%, an electrophotographic photoreceptor is provided that suppresses the decrease in chargeability and has excellent dot reproducibility. <10> According to the invention, an electrophotographic photoreceptor is provided that suppresses the decrease in chargeability and has excellent dot reproducibility compared to cases where the thickness of the charge transport layer is less than 16 μm or more than 30 μm. <11> According to the invention, compared to cases where the thickness of the inorganic protective layer is less than 1 μm or more than 4 μm, an electrophotographic photoreceptor is provided that suppresses the decrease in chargeability and has excellent dot reproducibility. <12> , or <13> According to the invention, the present invention comprises a conductive substrate, a charge generation layer disposed on the conductive substrate, a charge transport layer disposed on the charge generation layer, and an inorganic protective layer disposed on the charge transport layer, wherein the capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10 -6 (F / m 2 ) less than, or 1.90 × 10 -6 (F / m 2 ) or the capacitance per unit area of ​​the inorganic protective layer (X2) is 2.40 × 10 -5 (F / m 2 ) less than, or 1.10 × 10 -4 (F / m 2 Compared to cases where the value exceeds the limit, a process cartridge or image forming apparatus is provided that has an electrophotographic photoreceptor that suppresses the decrease in chargeability and has excellent dot reproducibility. [Brief explanation of the drawing]

[0007] [Figure 1] This is a partial cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to this embodiment. [Figure 2]This is a schematic diagram showing an example of a film deposition apparatus used to form an inorganic protective layer on an electrophotographic photoreceptor in this embodiment. [Figure 3] This is a schematic diagram showing an example of a plasma generator used for forming the inorganic protective layer of the electrophotographic photoreceptor in this embodiment. [Figure 4] This is a schematic diagram showing an example of an image forming apparatus according to this embodiment. [Figure 5] This is a schematic diagram showing another example of the image forming apparatus according to this embodiment. [Modes for carrying out the invention]

[0008] The following describes an example of the present invention. These descriptions and examples are illustrative and do not limit the scope of the present invention.

[0009] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise within this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described within this specification, the upper or lower limit of that range may be replaced with the values ​​shown in the examples.

[0010] In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that their objective is achieved. When embodiments are described herein with reference to the drawings, the configuration of such embodiments is not limited to that shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto.

[0011] In this specification, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this specification, if there are multiple types of the substance corresponding to that component in the composition, unless otherwise specified, it means the total amount of those multiple types of substances present in the composition.

[0012] In this specification, each component may contain multiple types of particles. When multiple types of particles corresponding to each component are present in a composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified.

[0013] In this specification, the "axial direction" of an electrophotographic photoreceptor means the direction in which the axis of rotation of the electrophotographic photoreceptor extends, and the "circumferential direction" of an electrophotographic photoreceptor means the direction of rotation of the electrophotographic photoreceptor.

[0014] <Electrophotographic photoconductor> The electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") according to this embodiment comprises a conductive substrate, a charge generation layer, a charge transport layer, and an inorganic protective layer. The charge generation layer is provided on a conductive substrate. The charge transport layer comprises a binder resin, a charge transport material, and metal oxide particles. The inorganic protective layer is placed on top of the charge transport layer. Furthermore, the capacitance per unit area of ​​the charge transport layer (X1) is 0.90 × 10⁻⁶. -6 (F / m 2 ) 1.90 × 10 -6 (F / m 2 ) and the capacitance per unit area of ​​the inorganic protective layer (X2) is 2.40 × 10 -5 (F / m 2 ) Above 1.10 × 10 -4 (F / m 2 ) are as follows:

[0015] The photoreceptor according to this embodiment, with the above configuration, suppresses the decrease in chargeability and becomes a photoreceptor with excellent dot reproducibility. The reason for this is presumed to be as follows.

[0016] In a laminated photoreceptor equipped with an inorganic protective layer, when the negative charge developed on the photoreceptor moves to the developing element side, the charging potential of the charge transport layer decreases. As a result, the dot edges of the electrostatic latent image become unstable in the inorganic protective layer, causing lateral flow of the electrostatic latent image and reducing dot reproducibility. This, in turn, reduces granularity. Here, the movement of the negative charge developed onto the photoreceptor to the developing element is suppressed by increasing the capacitance of the charge transport layer and the inorganic protective layer.

[0017] However, if the capacitance of the charge transport layer is increased too much, the charging ability decreases. Also, if the capacitance of the inorganic protective layer is increased too much, the electrostatic attraction between the toner particles and the latent image charge decreases. The toner image on the drum surface is easily distorted by the AC electric field during development, which again reduces dot reproducibility due to lateral flow of the latent image.

[0018] Therefore, in this embodiment, the photoreceptor has a capacitance (X1) per unit area of ​​the charge transport layer, as described above, of 0.90 × 10 -6 (F / m 2 ) 1.90 × 10 -6 (F / m 2 ) or less, and the capacitance per unit area of ​​the inorganic protective layer (X2) is 2.40 × 10 -5 (F / m 2 ) Above 1.10 × 10 -4 (F / m 2 The following conditions should be met. This will suppress the decrease in charge and the decrease in dot reproducibility due to lateral flow of latent images.

[0019] For the reasons stated above, it is presumed that the photoreceptor according to this embodiment will suppress the decrease in chargeability and become an electrophotographic photoreceptor with excellent dot reproducibility.

[0020] The details of the photoreceptor according to this embodiment will be described below.

[0021] Figure 1 is a schematic partial cross-sectional view showing an example of the layer structure of a photoreceptor according to this embodiment. The photoreceptor 10A shown in Figure 1 has a stacked photoreceptor layer. The photoreceptor 10A has a structure in which a base layer 2, a charge generation layer 3, a charge transport layer 4, and an inorganic protective layer 6 are stacked in this order on a conductive substrate 1, with the charge generation layer 3 and the charge transport layer 4 constituting the photosensitive layer 5 (a so-called functionally separated photosensitive layer). The photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3. The undercoat layer 2 may or may not be present.

[0022] The following describes each layer of the photoreceptor in detail. However, the symbols will be omitted, and the individual layers of the photoreceptor will be described accordingly.

[0023] [Conductive substrate] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Other examples of conductive substrates include paper, resin films, and belts coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys. Here, "conductive" refers to a volume resistivity of 10⁻¹⁰. 13 This refers to a value less than Ω·cm.

[0024] When an electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center-line average roughness Ra of 0.04 μm to 0.5 μm in order to suppress interference fringes that occur when irradiated with laser light. While roughening to prevent interference fringes is not particularly necessary when using non-interfering light as the light source, it is beneficial for extending the lifespan by suppressing the occurrence of defects due to surface irregularities of the conductive substrate.

[0025] Methods for roughening a surface include, for example, wet honing, which involves suspending an abrasive in water and spraying it onto a conductive substrate; centerless grinding, which involves pressing a conductive substrate against a rotating grinding wheel and continuously grinding it; and anodizing.

[0026] One method for roughening the surface is to disperse conductive or semiconductive powder in a resin without roughening the surface of the conductive substrate, to form a layer on the surface of the conductive substrate, and then roughen the surface with the particles dispersed in that layer.

[0027] Anodizing roughening treatment involves forming an oxide film on the surface of a conductive substrate (e.g., aluminum) by anodizing it in an electrolyte solution. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film to block the micropores of the oxide film by volume expansion due to a hydration reaction using pressurized steam or boiling water (metal salts such as nickel may be added), thereby converting it into a more stable hydrated oxide.

[0028] The thickness of the anodic oxide film is preferably, for example, 0.3 μm to 15 μm. When the film thickness is within this range, it tends to exhibit barrier properties against injection and tends to suppress the increase in residual potential due to repeated use.

[0029] The conductive substrate may be treated with an acidic treatment solution or with boehmite. Treatment with an acidic solution is carried out, for example, as follows: First, an acidic solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic solution is, for example, in the range of 10% to 11% by mass for phosphoric acid, 3% to 5% by mass for chromic acid, and 0.5% to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness is preferably 0.3 μm to 15 μm.

[0030] The boehmite treatment is carried out, for example, by immersing the material in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting it with heated steam at 90°C to 120°C for 5 to 60 minutes. The film thickness is preferably 0.1 μm to 5 μm. This can be further treated with anodic oxidation using an electrolyte solution with low film solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0031] (subbing layer) The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0032] As for inorganic particles, for example, powder resistance (volume resistivity) 10 2 Ω cm or more 10 11 Examples include inorganic particles with a size of Ω·cm or less. Among these, suitable inorganic particles having the above-mentioned resistance values ​​include, for example, metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0033] The specific surface area of ​​inorganic particles using the BET method is, for example, 10 m². 2 A value of 1g or more is preferable. The volume-average particle size of the inorganic particles is preferably between 50 nm and 2000 nm (preferably between 60 nm and 1000 nm).

[0034] The inorganic particle content is preferably 10% by mass or more and 80% by mass or less relative to the binder resin, and more preferably 40% by mass or more and 80% by mass or less.

[0035] The inorganic particles may be surface-treated. Two or more types of inorganic particles with different surface treatments or particle sizes may be mixed and used.

[0036] Examples of surface treatment agents include silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, and surfactants. Silane coupling agents are particularly preferred, and silane coupling agents having an amino group are more preferred.

[0037] Examples of silane coupling agents having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0038] Silane coupling agents may be used in combination of two or more types. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0039] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry or wet method.

[0040] The amount of surface treatment agent applied is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0041] In this case, it is preferable for the underlayer to contain electron-accepting compounds (acceptor compounds) along with inorganic particles, from the viewpoint of improving the long-term stability of electrical properties and carrier blocking ability.

[0042] Examples of electron-accepting compounds include electron-transporting substances such as compounds having anthraquinone structures; quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone; and benzophenone compounds. In particular, compounds having an anthraquinone structure are preferred as electron-accepting compounds. Examples of compounds having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds. Specifically, examples of preferred compounds include anthraquinone, alizarin, quinizalin, anthralphine, purpurin, and their derivatives.

[0043] The electron-accepting compound may be dispersed in the underlayer together with inorganic particles, or it may be present attached to the surface of the inorganic particles.

[0044] Methods for attaching electron-accepting compounds to the surface of inorganic particles include, for example, dry methods or wet methods.

[0045] The dry method involves, for example, adding an electron-accepting compound, either directly or dissolved in an organic solvent, dropwise while stirring inorganic particles with a mixer that has a high shear force, or spraying it with dry air or nitrogen gas, to adhere the electron-accepting compound to the surface of the inorganic particles. When adding or spraying the electron-accepting compound, it is preferable to do so at a temperature below the boiling point of the solvent. After adding or spraying the electron-accepting compound, further exposure may be performed at a temperature of 100°C or higher. The exposure time is not particularly limited as long as the temperature and duration are such that electrophotographic characteristics can be obtained.

[0046] The wet method involves dispersing inorganic particles in a solvent using, for example, a stirrer, ultrasonic disperser, sand mill, attritor, or ball mill, while adding an electron-accepting compound. After stirring or dispersion, the solvent is removed, and the electron-accepting compound adheres to the surface of the inorganic particles. Solvent removal methods include, for example, filtration or distillation. After solvent removal, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained. In the wet method, the water content of the inorganic particles may be removed before adding the electron-accepting compound. Examples of this include removing water while stirring and heating in the solvent, or removing water by azeotrope with the solvent.

[0047] Furthermore, the attachment of the electron-accepting compound may be performed before or after surface treatment with a surface treatment agent on the inorganic particles, or it may be performed simultaneously with the attachment of the electron-accepting compound and surface treatment with the surface treatment agent.

[0048] The content of the electron-accepting compound is preferably, for example, 0.01% by mass or more and 20% by mass or less relative to the inorganic particles, and more preferably 0.01% by mass or more and 10% by mass or less.

[0049] Examples of known polymer compounds used as the binder resin for the undercoat include acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, unsaturated polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, alkyd resin, epoxy resin, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Examples of binder resins used in the undercoat include charge-transporting resins having charge-transporting groups, conductive resins (e.g., polyaniline), and the like.

[0050] Among these, a resin insoluble in the coating solvent of the upper layer is preferred as the binder resin used for the undercoat layer. In particular, a resin obtained by the reaction of a curing agent with at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin is preferred. When using two or more of these binder resins in combination, the mixing ratio is set as needed.

[0051] The undercoat may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of known additives include electron-transporting pigments such as polycyclic condensation and azo pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. As mentioned above, silane coupling agents are used for surface treatment of inorganic particles, but they may also be added to the undercoat as additives.

[0052] Examples of silane coupling agents used as additives include vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0053] Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0054] Examples of titanium chelate compounds include tetraisopropyl titanate, tetran-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0055] Examples of aluminum chelating compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0056] These additives may be used individually or as a mixture or polycondensate of multiple compounds.

[0057] The underlayer should ideally have a Vickers hardness of 35 or higher. The surface roughness (ten-point average roughness) of the undercoat layer should be adjusted to between 1 / (4n) (where n is the refractive index of the upper layer) and 1 / 2 of the exposure laser wavelength λ used, in order to suppress moiré patterns. Resin particles may be added to the undercoat to adjust the surface roughness. Examples of resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. The surface of the undercoat may also be polished to adjust the surface roughness. Polishing methods include buffing, sandblasting, wet honing, and grinding.

[0058] There are no particular restrictions on the formation of the undercoat layer, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of an undercoat-forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0059] Solvents for preparing the coating solution for forming the undercoat include known organic solvents such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0060] Known methods for dispersing inorganic particles when preparing a coating solution for forming an undercoat include, for example, roll mills, ball mills, vibrating ball mills, attritors, sand mills, colloid mills, and paint shakers.

[0061] Conventional methods for applying the undercoating solution onto a conductive substrate include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0062] The thickness of the undercoat layer is preferably set to a range of 15 μm or more, and more preferably 20 μm to 50 μm.

[0063] (Middle class) Although not shown in the diagram, an intermediate layer may be further provided between the undercoat layer and the photosensitive layer. The intermediate layer is, for example, a layer containing a resin. Examples of resins used in the intermediate layer include polymer compounds such as acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, and melamine resin. The intermediate layer may contain an organometallic compound. Examples of organometallic compounds used in the intermediate layer include those containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in these intermediate layers may be used individually, as a mixture of multiple compounds, or as polycondensates.

[0064] Among these, the intermediate layer is preferably a layer containing an organometallic compound that contains zirconium atoms or silicon atoms.

[0065] There are no particular restrictions on the formation of the intermediate layer, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of an intermediate layer-forming coating solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary. Conventional methods such as immersion coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating are used to form the intermediate layer.

[0066] The thickness of the intermediate layer is preferably set to a range of 0.1 μm to 3 μm, for example. The intermediate layer may also be used as a base layer.

[0067] (Charge generation layer) The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Alternatively, the charge generation layer may be a vapor-deposited layer of the charge generation material. A vapor-deposited layer of the charge generation material is suitable when using non-coherent light sources such as LEDs (Light Emitting Diodes) or organic EL (Electro-Luminescence) image arrays.

[0068] Examples of charge-generating materials include azo pigments such as bisazo and trisazo; fused aromatic pigments such as dibromoanthonthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0069] Among these, in order to accommodate laser exposure in the near-infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material. Specifically, for example, hydroxygallium phthalocyanine; chlorogallium phthalocyanine; dichlorotin phthalocyanine; and titanyl phthalocyanine are more preferable.

[0070] On the other hand, to accommodate laser exposure in the near-ultraviolet region, preferred charge-generating materials include fused aromatic pigments such as dibromoanthoten; thioindigo pigments; porphyrazine compounds; zinc oxide; trigonal selenium; and bisazo pigments.

[0071] The above charge generating material may also be used when using non-coherent light sources such as LEDs and organic EL image arrays, which have a central emission wavelength between 450 nm and 780 nm.

[0072] When n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark currents are less likely to occur, and image defects called black spots can be suppressed even in thin films. Furthermore, the n-type is determined using the commonly used time-of-flight method, based on the polarity of the photocurrent that flows. Those that are more likely to carry electrons as carriers than holes are classified as n-type.

[0073] The binder resin used in the charge generation layer can be selected from a wide range of insulating resins, or it may be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (such as polycondensates of bisphenols and aromatic divalent carboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinylpyrrolidone resin. Here, "insulating properties" refer to a volume resistivity of 10¹³ Ω·cm or higher. These binder resins can be used individually or in combination of two or more types.

[0074] Furthermore, the mixing ratio of the charge-generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass ratio.

[0075] The charge generation layer may also contain other well-known additives.

[0076] The formation of the charge generation layer is not particularly limited, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of a charge generation layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it as necessary. The charge generation layer may also be formed by vapor deposition of the charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when using fused aromatic pigments or perylene pigments as the charge generation material.

[0077] Solvents for preparing the coating solution for forming the charge generation layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene. These solvents can be used individually or in mixtures of two or more.

[0078] Methods for dispersing particles (e.g., charge-generating materials) in a coating solution for forming a charge-generating layer include, for example, media dispersers such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, as well as media-less dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include collision methods, which disperse the dispersion by causing liquid-liquid collisions or liquid-wall collisions under high pressure, and penetration methods, which disperse the dispersion by penetrating fine channels under high pressure. Furthermore, during this dispersion, it is effective to set the average particle size of the charge-generating material in the coating solution for forming the charge-generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0079] Conventional methods for applying the charge-generating layer forming coating solution onto the undercoat (or intermediate layer) include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0080] The thickness of the charge generation layer is preferably set to a range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0081] [Charge transport layer] The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may also be a layer containing a polymer charge transport material.

[0082] -Capacitance- In this embodiment, the photoreceptor has a capacitance (X1) per unit area of ​​the charge transport layer of 0.90 × 10 -6 (F / m 2 ) 1.90 × 10 -6 (F / m 2 ) are as follows: The capacitance per unit area (X1) is 0.90 × 10⁻⁶ -6 (F / m 2 ) 1.50 × 10 -6 (F / m 2 ) More preferably, and even more preferably, 0.90 × 10 -6 (F / m 2 ) 1.20 × 10 -6 (F / m 2 It is preferable that it be less than or equal to the following: The capacitance per unit area (X1) is 0.90 × 10 -6 (F / m 2 If the value is less than ), the negative charge on the photoreceptor moves to the developing element, reducing its chargeability. As a result, dot lateral movement occurs, and dot reproducibility decreases. The capacitance per unit area (X1) is 1.90 × 10⁻⁶ -6 (F / m 2 If the charge level exceeds a certain value, the electrostatic properties decrease, making it difficult to reach the target charge potential, resulting in variations in the charge potential.

[0083] By ensuring that the capacitance (X1) per unit area of ​​the charge transport layer satisfies the above range, the photoreceptor is less prone to a decrease in chargeability and its dot reproducibility improves.

[0084] One method for ensuring that the capacitance (X1) per unit area of ​​the charge transport layer satisfies the above range is to adjust the relative permittivity and film thickness of the charge transport layer, as described later. Methods for adjusting the relative permittivity of the charge transport layer include adjusting the type and amount of metal oxide particles, and adjusting the degree of hydrophobicity of the metal oxide particles through surface treatment.

[0085] -Capacitance ratio- Preferably, the capacitance per unit area of ​​the charge transport layer (X1) is such that the ratio (X1 / X2) of the capacitance per unit area of ​​the inorganic protective layer (X2), as described later, is 0.010 or more and 0.070 or less.

[0086] The ratio (X1 / X2) of the capacitance per unit area of ​​the charge transport layer (X1) to the capacitance per unit area of ​​the inorganic protective layer (X2) is more preferably 0.020 or more and 0.060 or less, and even more preferably 0.030 or more and 0.040 or less.

[0087] When the ratio (X1 / X2) of the capacitance per unit area of ​​the charge transport layer (X1) to the capacitance per unit area of ​​the inorganic protective layer (X2) is between 0.010 and 0.070, the inflow of charge to the developing element is suppressed, making it less likely for latent images to flow laterally. This improves dot reproduction and also prevents a decrease in charge resistance.

[0088] Therefore, by ensuring that the ratio (X1 / X2) of the capacitance per unit area of ​​the charge transport layer (X1) to the capacitance per unit area of ​​the inorganic protective layer (X2) satisfies the above range, the electrostatic properties are less likely to decrease, and dot reproducibility is improved.

[0089] The capacitance C of the charge transport layer per unit area in an electrophotographic photoreceptor is calculated from the relative permittivity and film thickness, as described later, using the formula: C = ε / d (ε: permittivity, d: film thickness). Permittivity (ε) = Relative permittivity × Permittivity of vacuum (ε0) The permittivity of vacuum (ε0) = 8.854 × 10⁻⁴ -12

[0090] (metal oxide particles) In this embodiment, the photoreceptor preferably contains metal oxide particles in the charge transport layer. Examples of metal oxide particles used in the charge transport layer include silica particles, alumina particles, and titanium oxide particles.

[0091] Among these, from the viewpoint of suppressing the deterioration of the photoreceptor's electrical properties, silica particles are more preferable as the metal oxide particles. The content of metal oxide particles is preferably 40% by volume or more and 60% by volume or less. More preferably, the amount is 50% by volume or more and 60% by volume or less, and even more preferably 55% by volume or more and 60% by volume or less. When the metal oxide particle content exceeds 40% by volume, both the dielectric constant and capacitance increase. As a result, dot reproducibility tends to improve. When the metal oxide particle content is 60% by volume or less, the excessive increase in capacitance along with the dielectric constant is suppressed. As a result, the decrease in chargeability is more easily suppressed.

[0092] By ensuring that the amount of metal oxide particles contained in the charge transport layer meets the above range, the photoreceptor's chargeability is less likely to decrease, resulting in improved dot reproduction.

[0093] -Silica particles- Examples of silica particles include dry silica particles and wet silica particles.

[0094] Examples of dry silica particles include fumed silica and deflagration silica. Fumed silica is obtained by burning silane compounds. Deflagration silica is obtained by explosively burning metallic silicon powder.

[0095] Examples of wet silica particles include sedimentation silica, gel silica, colloidal silica (silica sol particles), and sol-gel silica.

[0096] Precipitated silica and gel-processed silica particles are obtained by the neutralization reaction of sodium silicate and mineral acid. Silica synthesized and aggregated under alkaline conditions is called precipitated silica, while silica synthesized and aggregated under acidic conditions is called gel-processed silica particles.

[0097] Colloidal silica particles (silica sol particles) are obtained by polymerizing acidic silicic acid in an alkaline state.

[0098] Sol-gel silica particles are obtained by hydrolysis of organosilane compounds (e.g., alkoxysilanes).

[0099] It is preferable that the silica particles have their surfaces treated with a hydrophobic treatment agent. This reduces the number of silanol groups on the surface of the silica particles, making it easier to suppress the generation of residual potential. Examples of hydrophobic treatment agents include well-known silane compounds such as chlorosilanes, alkoxysilanes, and silazanes. Among these, silane compounds having a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group are preferable as hydrophobic treatment agents, from the viewpoint of easily suppressing the generation of residual potential. In other words, it is preferable for the surface of silica particles to have a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group. Examples of silane compounds containing a trimethylsilyl group include trimethylchlorosilane, trimethylmethoxysilane, and 1,1,1,3,3,3-hexamethyldisilazane. Examples of silane compounds containing a decylsilyl group include decyltrichlorosilane, decyldimethylchlorosilane, and decyltrimethoxysilane. Examples of silane compounds containing a phenyl group include triphenylmethoxysilane and triphenylchlorosilane.

[0100] -Amount of OH groups in metal oxides- In the photoreceptor according to this embodiment, if the charge transport layer contains metal oxide particles with an appropriate amount of residual OH groups, the capacitance, along with the relative permittivity, becomes easier to control within the above range. Therefore, the degree of hydrophobicity of the metal oxide particles in the charge transport layer is preferably 60% or more, more preferably 62% or more, and even more preferably 65% ​​or more. When the degree of hydrophobicity of metal oxide particles in the charge transport layer is 60% or higher, it becomes easier to suppress an excessive increase in capacitance along with relative permittivity in the charge transport layer. As a result, the decrease in chargeability becomes easier to suppress. Therefore, by ensuring that the degree of hydrophobicity of the metal oxide particles contained in the charge transport layer satisfies the above range, the charging properties of the photoreceptor do not deteriorate easily, and dot reproducibility improves.

[0101] The degree of hydrophobicity of metal oxide particles is calculated using the following method. Add 5g of metal oxide particles to 100mL of water, and add methanol dropwise at a rate of 1mL, allowing the metal oxide particles to settle. Calculate the ratio of the volume of the added methanol to the total volume of the solution using the following formula, and define this as the degree of hydrophobicity. Formula: [(Volume of methanol added) / {(Volume of methanol added)+(Volume of water)}] ×100 One method for separating metal oxide particles from the charge transport layer is to dissolve the charge transport layer, which has been detached from the substrate, in an organic solvent and then sift the solution to separate the metal oxide particles that are not dissolved in the organic solvent. -Relative permittivity- The relative permittivity of the charge transport layer is preferably, for example, 3.20 or more and 3.40 or less. By ensuring the relative permittivity of the charge transport layer meets the above range, it becomes easier to adjust the capacitance to the desired level. As a result, the photoreceptor's chargeability is less likely to decrease, and dot reproducibility improves. The relative permittivity of the charge transport layer is more preferably set within the range of 3.20 to 3.35, and even more preferably within the range of 3.20 to 3.30.

[0102] The method for measuring the relative permittivity of the charge transport layer is as follows: The charge transport layer is peeled off from the photoreceptor to obtain a sample. The sample is placed in the sample holder of an impedance analyzer (Toyo Technica), and measured at an AC voltage of 1V and a frequency of 100Hz. The capacitance is then calculated using CR parallel fitting. Furthermore, the film thickness is measured using a reflection spectroscopic film thickness analyzer at 10 points evenly spaced along the axial direction of the photoreceptor and at 90° intervals in the circumferential direction, for a total of 40 points, and the arithmetic mean is obtained. The relative permittivity is then calculated using the capacitance calculation formula.

[0103] -film thickness- The thickness of the charge transport layer is preferably, for example, 16 μm or more and 30 μm or less. By ensuring the charge transport layer thickness meets the above range, it becomes easier to adjust the capacitance to the desired level. As a result, the photoreceptor's chargeability is less likely to decrease, and dot reproducibility improves. The thickness of the charge transport layer is more preferably set within the range of 18 μm to 25 μm, and even more preferably within the range of 20 μm to 23 μm.

[0104] The thickness of the charge transport layer is the arithmetic mean of the measurements taken with an electromagnetic film thickness gauge. The measurements were taken at four points in the circumferential direction at 90° intervals, centered in the axial direction of the photoreceptor.

[0105] (charge transport material) Examples of charge transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds, which are electron transport compounds. Other examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used individually or in combination of two or more, but are not limited to these.

[0106] As charge transport materials, from the viewpoint of charge mobility, the triarylamine derivative shown in the following structural formula (a-1) and the benzidine derivative shown in the following structural formula (a-2) are preferred.

[0107] [ka]

[0108] In structural formula (a-1), Ar T1 Ar T2 , and Ar T3is each independently a substituted or unsubstituted aryl group, -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 independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Examples of the substituents of each of the above groups include a halogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Further, examples of the substituents of each of the above groups also include a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0109]

Chemical formula

[0110] In structural formula (a-2), R T91 and R T92 each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. R T101 , R T102 , R T111 and R T112 each independently represent a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ), and R T12 , R T13 , R T14 , R T15 and R T16Each of these independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, ​​Tn1, and Tn2 each independently represent an integer between 0 and 2. Substituents for each of the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. Furthermore, substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms are also examples of substituents for each of the above groups.

[0111] Here, among the triarylamine derivative represented by structural formula (a-1) and the benzidine derivative represented by structural formula (a-2), in particular, "-C6H4-CH=CH-CH=C(R T7 )(R T8 Triarylamine derivatives having ")" and "-CH=CH-CH=C(R T15 )(R T16 A benzidine derivative having ) is preferred from the viewpoint of charge mobility.

[0112] As polymer charge transport materials, known charge transport materials such as poly-N-vinylcarbazole and polysilane can be used. Polyester-based polymer charge transport materials are particularly preferred. Polymer charge transport materials may be used alone or in combination with a binder resin.

[0113] (Binding resin) Examples of binder resins used in the charge transport layer include 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, and polysilane. Among these, polycarbonate resin or polyarylate resin is preferred as the binder resin. These binder resins can be used individually or in combination of two or more. The preferred mixing ratio of the charge transport material to the binder resin is between 10:1 and 1:5 by mass.

[0114] The charge transport layer may also contain other well-known additives.

[0115] The formation of the charge transport layer is not particularly limited, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of a charge transport layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0116] Suitable solvents for preparing the coating solution for forming the charge transport layer include common organic solvents such as aromatic hydrocarbons like benzene, toluene, xylene, and chlorobenzene; ketones like acetone and 2-butanone; halogenated aliphatic hydrocarbons like methylene chloride, chloroform, and ethylene chloride; and cyclic or linear ethers like tetrahydrofuran and ethyl ether. These solvents can be used individually or in mixtures of two or more.

[0117] Conventional methods for applying a charge transport layer forming coating solution onto a charge generation layer include blade coating, wire bar coating, spray coating, immersion coating, bead coating, air knife coating, and curtain coating.

[0118] [Inorganic protective layer] The inorganic protective layer is provided, for example, to prevent chemical changes in the photosensitive layer when charged, or to further improve the mechanical strength of the photosensitive layer.

[0119] -Capacitance- In the photoreceptor of this embodiment, the capacitance (X2) per unit area of ​​the inorganic protective layer is 2.40 × 10 -5 (F / m 2 ) Above 1.10 × 10 -4 (F / m 2 ) are as follows: The capacitance per unit area (X²) is 2.40 × 10⁻⁶ -5 (F / m 2 ) 5.30 x 10-5 (F / m 2 ) More preferably, and even more preferably, 2.80 × 10 -5 (F / m 2 ) 3.50 x 10 -5 (F / m 2 It is preferable that it be less than or equal to the following: The capacitance per unit area (X2) is 2.40 × 10 -5 (F / m 2 If the charge level is below a certain value, the negative charge on the photoreceptor moves to the developing element, causing the charge potential to decrease. As a result, dot lateral movement occurs, reducing dot reproducibility and decreasing granularity. The capacitance per unit area (X2) is 1.10 × 10 -4 (F / m 2 If the resolution exceeds 50°, lateral flow of the latent image occurs, reducing dot reproducibility. Furthermore, granularity decreases.

[0120] By ensuring that the capacitance per unit area (X2) of the inorganic protective layer satisfies the above range, the photoreceptor's charge resistance is less likely to decrease, resulting in improved dot reproduction. One method for ensuring that the capacitance (X2) per unit area of ​​the inorganic protective layer satisfies the above range is to adjust the relative permittivity and film thickness of the inorganic protective layer, as described later. The dielectric constant of the inorganic protective layer can be adjusted by methods such as adjusting the elemental composition ratio (oxygen / group 13 elements) of oxygen and group 13 elements in the inorganic protective layer. Furthermore, one method for adjusting the elemental composition ratio (oxygen / Group 13 elements) is to adjust the flow rate ratio of oxygen gas and Group 13 element-containing compound gas in the method for forming the inorganic protective layer.

[0121] Here, the capacitance per unit area of ​​the inorganic protective layer (X2) is equivalent to the capacitance per unit area of ​​the charge transport layer (X1), and is calculated by the following method. The capacitance C of the inorganic protective layer per unit area in an electrophotographic photoreceptor is calculated using the same formula as the capacitance of the charge transport layer: C = ε / d (ε: dielectric constant, d: film thickness). Permittivity (ε) = Relative permittivity × Permittivity of vacuum (ε0) ε0 = 8.854 × 10 -12

[0122] -Relative permittivity- The relative permittivity of the inorganic protective layer is preferably, for example, 11.0 to 12.0. By ensuring the dielectric constant of the inorganic protective layer meets the above range, it becomes easier to adjust the capacitance to the desired level. As a result, dot reproducibility improves. The dielectric constant of the inorganic protective layer is more preferably set within the range of 11.0 to 11.5, and even more preferably within the range of 11.0 to 11.3.

[0123] The method for measuring the relative permittivity of the inorganic protective layer is as follows: The charge transport layer is peeled off from the photoreceptor to obtain a sample. The sample is placed in the sample holder of an impedance analyzer (Toyo Technica), and measured at an AC voltage of 1V and a frequency of 100Hz. The capacitance is then calculated using CR parallel fitting. Furthermore, the film thickness is determined by performing layer thickness analysis at 10 points evenly spaced along the axial direction of the photoreceptor and at 90° intervals in the circumferential direction, for a total of 40 points, using a reflection spectroscopic film thickness analyzer, and taking the arithmetic mean value. The relative permittivity is then calculated using the above formula. -film thickness-

[0124] The thickness of the inorganic protective layer is preferably, for example, 1.0 μm or more and 4.0 μm or less. By ensuring the inorganic protective layer thickness meets the above range, it becomes easier to adjust the capacitance to the desired level. As a result, dot reproducibility improves. The thickness of the inorganic protective layer is more preferably set within the range of 2.0 μm to 3.5 μm, and even more preferably within the range of 2.5 μm to 3.0 μm.

[0125] The thickness of the inorganic protective layer is the arithmetic mean of the measurements taken with an electromagnetic film thickness gauge. The measurements were taken at four points in the circumferential direction at 90° intervals, centered in the axial direction of the photoreceptor.

[0126] -Composition of the inorganic protective layer- The inorganic protective layer is an inorganic material layer. Examples of inorganic materials include metal oxides such as gallium oxide, aluminum oxide, zinc oxide, titanium oxide, indium oxide, tin oxide, and boron oxide; metal nitrides such as gallium nitride, aluminum nitride, zinc nitride, titanium nitride, indium nitride, tin nitride, and boron nitride; carbon-based and silicon-based inorganic materials such as diamond-like carbon, amorphous carbon, hydrogenated amorphous carbon, hydrogenated / fluorinated amorphous carbon, amorphous silicon carbide, hydrogenated amorphous silicon carbide, amorphous silicon, and hydrogenated amorphous silicon; and mixed crystals thereof.

[0127] The inorganic protective layer is preferably a layer containing a metal oxide, more preferably a layer containing a group 13 element and an oxygen element, and even more preferably a layer containing gallium oxide or aluminum oxide, from the viewpoint of the photoreceptor's abrasion resistance and electrical properties. The inorganic protective layer may contain one or more metal oxides.

[0128] The inorganic protective layer preferably contains oxygen and a Group 13 element. The inorganic protective layer is often composed of at least a Group 13 element (especially gallium) and oxygen, and may also contain hydrogen as needed. The inclusion of hydrogen makes it easier to control the various properties of the inorganic protective layer composed of at least a Group 13 element (especially gallium) and oxygen. For example, in an inorganic protective layer containing gallium, oxygen, and hydrogen (for example, an inorganic protective layer composed of gallium oxide containing hydrogen), by changing the composition ratio [O] / [Ga] from 1.0 to 1.5, 10 9 Ω cm or more 10 14 This makes it easier to control the volume resistivity within the range of Ω·cm.

[0129] Here, if the inorganic protective layer is composed of gallium, oxygen, and optionally hydrogen, the preferred elemental composition ratios are as follows, from the viewpoint of maintaining the light transmittance of the inorganic protective layer and suppressing charge transfer during development. The elemental composition ratio of gallium is preferably between 40 and 43 atomic percent, more preferably between 40 and 42 atomic percent, and more preferably between 40 and 41 atomic percent, relative to the total constituent elements of the inorganic protective layer. The elemental composition ratio of oxygen is preferably between 57 and 60 atomic percent, more preferably between 58 and 60 atomic percent, and more preferably between 59 and 60 atomic percent, relative to the total constituent elements of the inorganic protective layer.

[0130] The elemental composition ratio (oxygen / group 13 element) of oxygen and group 13 elements in the inorganic protective layer is preferably 1.40 or more and 1.50 or less. The elemental composition ratio (oxygen / group 13 element) of oxygen and group 13 elements in the inorganic protective layer is more preferably within the range of 1.45 to 1.50, and even more preferably within the range of 1.48 to 1.50. If the elemental composition ratio of oxygen and group 13 elements in the inorganic protective layer (oxygen / group 13 elements) is between 1.40 and 1.50, the dielectric constant can be easily adjusted, and the capacitance can be controlled within the above range.

[0131] Here, the elemental composition ratio of each element in the inorganic protective layer is determined by Rutherford back scattering (hereinafter referred to as "RBS"). The RBS (Revolutionary Beam Synchronization) will utilize NEC's 3SDH Pelletron as the accelerator, CE&A's RBS-400 as the end station, and 3S-R10 as the system. CE&A's HYPRA program and other software will be used for analysis. The measurement conditions for RBS are as follows: He++ ion beam energy of 2.275 eV, detection angle of 160°, and grazing angle of approximately 109° relative to the incident beam.

[0132] RBS measurement is performed as follows: First, He ++An ion beam is incident perpendicularly on the sample, and the detector is set at 160° to the ion beam. The signal of backscattered He is then measured. The composition ratio is determined from the detected energy and intensity of He. To improve the accuracy of determining the composition ratio, spectra may be measured at two different detection angles. Accuracy can be improved by measuring at two detection angles with different depth resolution and backscatter dynamics and cross-checking the results. The number of He atoms backscattered by a target atom is determined by only three factors: 1) the atomic number of the target atom, 2) the energy of the He atoms before scattering, and 3) the scattering angle.

[0133] By ensuring that the elemental composition ratio of oxygen and Group 13 elements in the inorganic protective layer (oxygen / Group 13 elements) meets the above range, the photoreceptor's chargeability is less likely to decrease, and dot reproduction quality improves.

[0134] The volume resistivity of the inorganic protective layer is 1.0 × 10⁻⁶ from the viewpoint of maintaining the electrostatic latent image. 10 It is preferable that the density be Ω·cm or greater, and 1.0 × 10 11 A value of Ω·cm or greater is more preferable.

[0135] The method for measuring the volume resistivity of the inorganic protective layer is as follows: The inorganic protective layer is peeled off from the photoreceptor to prepare the sample. The sample is placed in the sample holder of an impedance analyzer (Toyo Technica), and the resistance value is measured at an AC voltage of 1V and a frequency of 100Hz. The resistance is then calculated based on the electrode area and the thickness of the sample.

[0136] -Formation of an inorganic protective layer- Known vapor deposition methods such as plasma CVD (Chemical Vapor Deposition), organometallic vapor deposition, molecular beam epitaxy, evaporation, and sputtering can be used to form the inorganic protective layer. For example, the plasma CVD deposition apparatus and deposition conditions described in Japanese Patent Application Publication No. 2014-191179 can be used to form the inorganic protective layer.

[0137] The following explanation describes the formation of inorganic surface layers, illustrating this with specific examples and illustrating an example of a film deposition apparatus in the drawings. While the following explanation focuses on the formation of an inorganic surface layer composed of gallium, oxygen, and hydrogen, it is not limited to this method; any known formation method should be applied depending on the desired composition of the inorganic surface layer.

[0138] Figure 2 is a schematic diagram showing an example of a film deposition apparatus used for forming an inorganic surface layer of an electrophotographic photoreceptor according to this embodiment. Figure 2(A) shows a schematic cross-sectional view of the film deposition apparatus viewed from the side, and Figure 2(B) shows a schematic cross-sectional view between A1 and A2 of the film deposition apparatus shown in Figure 2(A). In Figure 2, 210 is the film deposition chamber, 211 is the exhaust port, 212 is the substrate rotation section, 213 is the substrate support member, 214 is the substrate, 215 is the gas introduction pipe, 216 is the shower nozzle having an opening for injecting the gas introduced from the gas introduction pipe 215, 217 is the plasma diffusion section, 218 is the high-frequency power supply section, 219 is the flat plate electrode, 220 is the gas introduction pipe, and 221 is the high-frequency discharge tube section.

[0139] In the film deposition apparatus shown in Figure 2, an exhaust port 211 connected to a vacuum exhaust device (not shown) is provided at one end of the film deposition chamber 210, and a plasma generator consisting of a high-frequency power supply unit 218, a flat plate electrode 219, and a high-frequency discharge tube unit 221 is provided on the side of the film deposition chamber 210 opposite to the side with the exhaust port 211. This plasma generator comprises a high-frequency discharge tube section 221 and a section located inside the high-frequency discharge tube section 221. It consists of a flat plate electrode 219 with its discharge surface facing the exhaust port 211, and a high-frequency power supply unit 218 positioned outside the high-frequency discharge tube section 221 and connected to the side of the flat plate electrode 219 opposite to the discharge surface. A gas introduction pipe 220 for supplying gas into the high-frequency discharge tube section 221 is connected to the high-frequency discharge tube section 221, and the other end of this gas introduction pipe 220 is connected to a first gas supply source (not shown).

[0140] Alternatively, the plasma generator shown in Figure 3 may be used instead of the plasma generator provided in the film deposition apparatus shown in Figure 2. Figure 3 is a schematic diagram showing another example of a plasma generator used in the film deposition apparatus shown in Figure 2, and is a side view of the plasma generator. In Figure 3, 222 represents a high-frequency coil, 223 represents a quartz tube, and 220 is the same as that shown in Figure 2. This plasma generator consists of a quartz tube 223 and a high-frequency coil 222 provided along the outer surface of the quartz tube 223, with one end of the quartz tube 223 connected to a film deposition chamber 210 (not shown in Figure 3). The other end of the quartz tube 223 is connected to a gas introduction pipe 220 for introducing gas into the quartz tube 223.

[0141] In Figure 2, a rod-shaped shower nozzle 216 extending along the discharge surface is connected to the discharge surface side of the flat electrode 219. One end of the shower nozzle 216 is connected to a gas introduction pipe 215, which is connected to a second gas supply source (not shown) located outside the film deposition chamber 210. Furthermore, a substrate rotation section 212 is provided within the film deposition chamber 210, and a cylindrical substrate 214 is attached to the substrate rotation section 212 via a substrate support member 213 so that the longitudinal direction of the shower nozzle 216 and the axial direction of the substrate 214 face each other. During film deposition, the substrate rotation section 212 rotates, causing the substrate 214 to rotate in the circumferential direction. For example, a photoreceptor with an organic photosensitive layer already laminated is used as the substrate 214.

[0142] The inorganic surface layer can be formed, for example, as follows: First, oxygen gas (or helium (He) diluted oxygen gas), helium (He) gas, and hydrogen (H2) gas as needed are introduced into the high-frequency discharge tube section 221 from the gas introduction tube 220, and a 13.56 MHz radio wave is supplied to the flat electrode 219 from the high-frequency power supply section 218. At this time, a plasma diffusion section 217 is formed so as to spread radially from the discharge surface side of the flat electrode 219 toward the exhaust port 211 side. Here, the gas introduced from the gas introduction tube 220 flows through the film deposition chamber 210 from the flat electrode 219 side toward the exhaust port 211 side. The flat electrode 219 may also be surrounded by an earth shield.

[0143] Next, trimethylgallium gas is introduced into the deposition chamber 210 via the gas introduction tube 215 and the shower nozzle 216 located downstream of the plate electrode 219, which is an activation device, thereby depositing a non-single-crystal film containing gallium, oxygen, and hydrogen on the surface of the substrate 214. As the substrate 214, for example, a substrate on which an organic photosensitive layer is formed is used.

[0144] The temperature of the substrate 214 surface during film formation of the inorganic surface layer is preferably 150°C or lower, more preferably 100°C or lower, and particularly preferably between 30°C and 100°C, since an organic photoreceptor having an organic photosensitive layer is used. Even if the surface temperature of the substrate 214 is below 150°C at the start of film deposition, if it rises above 150°C due to the influence of plasma, the organic photosensitive layer may be damaged by heat. Therefore, it is desirable to control the surface temperature of the substrate 214 taking this effect into consideration. The surface temperature of the substrate 214 may be controlled by at least one of a heating device and a cooling device (not shown in the figure), or it may be left to the natural temperature rise during discharge. When heating the substrate 214, the heater may be installed on the outside or inside of the substrate 214. When cooling the substrate 214, a cooling gas or liquid may be circulated inside the substrate 214. To avoid a temperature rise on the substrate 214 surface due to electrical discharge, it is effective to adjust the high-energy gas flow hitting the substrate 214 surface. In this case, conditions such as gas flow rate, discharge output, and pressure are adjusted to achieve the desired temperature.

[0145] Alternatively, instead of trimethylgallium gas, organometallic compounds containing aluminum or hydrides such as diborane can be used, and two or more of these may be mixed. For example, by introducing trimethylindium into the deposition chamber 210 via the gas introduction tube 215 and shower nozzle 216 during the initial stages of inorganic surface layer formation, a film containing nitrogen and indium is deposited on the substrate 214. This film absorbs ultraviolet light that is generated during continuous deposition and degrades the organic photosensitive layer. Therefore, damage to the organic photosensitive layer caused by ultraviolet light during deposition is suppressed.

[0146] Furthermore, for dopant doping during film formation, SiH3 and SnH4 are used in gaseous form for n-type films, and biscyclopentadienylmagnesium, dimethylcalcium, dimethylstrontium, etc., are used in gaseous form for p-type films. In addition, known methods such as thermal diffusion and ion implantation may be used to dopant elements into the surface layer. Specifically, for example, a conductive inorganic surface layer of the n-type, p-type, etc., is obtained by introducing a gas containing at least one dopant element into the deposition chamber 210 via a gas introduction pipe 215 and a shower nozzle 216.

[0147] In the film deposition apparatus described using Figures 2 and 3, the activated nitrogen or activated hydrogen formed by the discharge energy may be independently controlled by providing multiple activation devices, or a gas containing both nitrogen and hydrogen atoms, such as NH3, may be used. Furthermore, H2 may be added. Alternatively, conditions that allow for the liberation and generation of activated hydrogen from organometallic compounds may be used. In this way, activated carbon atoms, gallium atoms, nitrogen atoms, hydrogen atoms, etc., exist in a controlled state on the surface of substrate 214. The activated hydrogen atoms have the effect of removing hydrogen molecules from hydrocarbon groups such as methyl and ethyl groups that constitute organometallic compounds. Therefore, a hard film (inorganic surface layer) that constitutes a three-dimensional bond is formed.

[0148] The plasma generator in the film deposition apparatus shown in Figures 2 and 3 uses a high-frequency oscillator, but is not limited to this. For example, a microwave oscillator may be used, or an electrocyclotron resonance or helicon plasma system may be used. In the case of a high-frequency oscillator, it may be either an inductive or capacitive type. Furthermore, two or more types of these devices may be used in combination, or two or more devices of the same type may be used. A high-frequency oscillator is desirable to suppress the temperature rise of the substrate 214 surface due to plasma irradiation, but a device to suppress heat irradiation may also be provided.

[0149] When using two or more different plasma generators, it is desirable to ensure that discharges occur simultaneously at the same pressure. Alternatively, a pressure difference may be provided between the discharge region and the film deposition region (the area where the substrate is placed). These devices may be arranged in series with respect to the gas flow formed within the deposition apparatus from the gas introduction area to the gas discharge area, or each device may be arranged facing the film deposition surface of the substrate.

[0150] For example, when two types of plasma generators are installed in series with respect to the gas flow, taking the film deposition apparatus shown in Figure 2 as an example, the shower nozzle 216 is used as an electrode to cause a discharge in the film deposition chamber 210. In this case, for example, a high-frequency voltage is applied to the shower nozzle 216 via the gas introduction pipe 215 to cause a discharge in the film deposition chamber 210 using the shower nozzle 216 as an electrode. Alternatively, the shower nozzle 216 can be used as an electrode. Instead of using it, a cylindrical electrode is placed between the substrate 214 and the flat electrode 219 in the film deposition chamber 210, and this cylindrical electrode is used to generate a discharge inside the film deposition chamber 210. Furthermore, when using two different types of plasma generators under the same pressure, for example, a microwave oscillator and a high-frequency oscillator, the excitation energy of the excited species can be significantly varied, which is effective for controlling the film quality. Also, the discharge may be performed near atmospheric pressure (70,000 Pa to 110,000 Pa). When performing the discharge near atmospheric pressure, it is desirable to use He as the carrier gas.

[0151] For example, the inorganic surface layer is formed by placing a substrate 214, on which an organic photosensitive layer has been formed, in a film deposition chamber 210, and introducing mixed gases with different compositions to form the inorganic surface layer.

[0152] Furthermore, regarding film deposition conditions, for example, when using high-frequency discharge, it is desirable to set the frequency in the range of 10 kHz to 50 MHz in order to deposit a high-quality film at low temperatures. Also, although the output depends on the size of the substrate 214, it is 0.01 W / cm² relative to the surface area of ​​the substrate. 2 More than 0.2W / cm 2 The following range is desirable: The rotational speed of the base 214 should preferably be in the range of 0.1 rpm to 500 rpm.

[0153] In addition to the inorganic material mentioned above, the inorganic protective layer may contain, for example, one or more elements selected from C, Si, Ge, and Sn in the case of n-type materials, to control the conductivity type. Alternatively, for example, in the case of p-type materials, it may contain one or more elements selected from N, Be, Mg, Ca, and Sr.

[0154] The film thickness of each layer of the photosensitive material is the arithmetic mean of the measurements taken with an electromagnetic film thickness gauge. The measurements were taken at four points in the circumferential direction at 90° intervals, centered in the axial direction of the photosensitive material.

[0155] <Image forming apparatus (and process cartridge)> The image forming apparatus according to this embodiment comprises an electrophotographic photoreceptor, a charging means for charging the surface of the electrophotographic photoreceptor, an electrostatic latent image forming means for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing means for developing 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 means for transferring the toner image to the surface of a recording medium. The electrophotographic photoreceptor according to this embodiment is used as the electrophotographic photoreceptor.

[0156] The image forming apparatus according to this embodiment includes a fixing means for fixing a toner image transferred to the surface of a recording medium; a direct transfer method apparatus for directly transferring a toner image formed on the surface of an electrophotographic photoreceptor to a recording medium; an intermediate transfer method apparatus for first transferring a toner image formed on the surface of an electrophotographic photoreceptor to the surface of an intermediate transfer body, and secondarily transferring the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium; a cleaning means for cleaning the surface of the electrophotographic photoreceptor after the transfer of the toner image and before it is charged; a static elimination means for irradiating the surface of the electrophotographic photoreceptor with static elimination light to eliminate static charge after the transfer of the toner image and before it is charged; and a well-known image forming apparatus such as an electrophotographic photoreceptor heating member for raising the temperature of the electrophotographic photoreceptor and reducing the relative temperature.

[0157] In the case of an intermediate transfer method apparatus, the transfer means may include, for example, an intermediate transfer body on which a toner image is transferred; a primary transfer means for primaryly transferring the toner image formed on the surface of an electrophotographic photoreceptor to the surface of the intermediate transfer body; and a secondary transfer means for secondary transferring the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium.

[0158] The image forming apparatus according to this embodiment may be either a dry developing type image forming apparatus or a wet developing type image forming apparatus (a developing method using a liquid developer).

[0159] In the image forming apparatus according to this embodiment, for example, the portion comprising the electrophotographic photoreceptor may be a cartridge structure (process cartridge) that can be attached to and detached from the image forming apparatus. As the process cartridge, for example, a process cartridge comprising the electrophotographic photoreceptor according to this embodiment is preferably used. In addition to the electrophotographic photoreceptor, the process cartridge may also include at least one selected from the group consisting of, for example, a charging means, an electrostatic latent image forming means, a developing means, and a transfer means.

[0160] The following is an example of an image forming apparatus according to this embodiment, but it is not limited to this example. The main parts shown in the figure will be described, and other parts will be omitted from the explanation.

[0161] Figure 4 is a schematic diagram showing an example of an image forming apparatus according to this embodiment. As shown in Figure 4, the image forming apparatus 100 according to this embodiment includes a process cartridge 300 equipped with an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming means), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is positioned to expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, and the transfer device 40 is positioned facing the electrophotographic photoreceptor 7 via the intermediate transfer body 50, with a portion of the intermediate transfer body 50 in contact with the electrophotographic photoreceptor 7. Although not shown, the apparatus also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (primary transfer device), and the secondary transfer device (not shown) are examples of transfer means. In the image forming apparatus 100, the control device 60 (an example of a control means) is a device that controls the operation of each device and component within the image forming apparatus 100, and is arranged in connection with each device and component.

[0162] In Figure 4, the process cartridge 300 integrally supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging means), a developing device 11 (an example of a developing means), and a cleaning device 13 (an example of a cleaning means) within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is positioned to contact the surface of the electrophotographic photoreceptor 7. The cleaning member may be a conductive or insulating fibrous member, rather than a cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

[0163] Figure 4 shows an example of an image forming apparatus equipped with a fibrous member 132 (roll-shaped) for supplying lubricant 14 to the surface of the electrophotographic photoreceptor 7, and a fibrous member 133 (flat brush-shaped) for assisting cleaning. These can be arranged as needed.

[0164] The following describes the various components of the image forming apparatus according to this embodiment.

[0165] [Charging device] As the charging device 8, for example, a contact-type charger using conductive or semiconductive charging rollers, charging brushes, charging films, charging rubber blades, charging tubes, etc. may be used. Non-contact roller chargers, known chargers such as scorotron chargers and corotron chargers that utilize corona discharge may also be used.

[0166] [Synthesis equipment] Examples of exposure devices 9 include optical equipment that exposes the surface of an electrophotographic photoreceptor 7 to a predetermined image using light such as semiconductor laser light, LED light, or liquid crystal shutter light. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photoreceptor. As for the wavelength of the semiconductor laser, near-infrared lasers with an oscillation wavelength of around 780 nm are the mainstream. However, the wavelength is not limited to this, and lasers with oscillation wavelengths in the 600 nm range or blue lasers with oscillation wavelengths between 400 nm and 450 nm may also be used. Furthermore, for color image formation, surface-emitting laser light sources capable of outputting multiple beams are also effective.

[0167] [Developing equipment] Examples of developing devices 11 include general developing devices that develop by contacting or not contacting the developing agent. There are no particular restrictions on the developing device 11 as long as it has the above-described functions, and it can be selected according to the purpose. For example, known developing devices that have the function of applying a one-component or two-component developing agent to the electrophotographic photoreceptor 7 using a brush, roller, etc. Among these, those that use a developing roller that holds the developing agent on its surface are preferred.

[0168] The developer used in the developing device 11 may be a one-component developer consisting of toner alone, or a two-component developer containing toner and a carrier. Furthermore, the developer may be magnetic or non-magnetic. Well-known developers are applicable.

[0169] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131. In addition to the cleaning blade method, a fur brush cleaning method or a developing-simultaneous cleaning method may also be used.

[0170] [Transfer device] Examples of the transfer charger 40 include known transfer chargers such as a contact type transfer charger using a belt, roller, film, rubber blade, etc., a scorotron transfer charger using corona discharge, and a corotron transfer charger.

[0171] [Intermediate transfer member] As the intermediate transfer member 50, a belt-shaped member (intermediate transfer belt) containing a polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. with semiconductive properties is used. Also, as the form of the intermediate transfer member, a drum-shaped member may be used in addition to the belt-shaped one.

[0172] [Control device] The control device 60 is configured as a computer that controls the entire device and performs various calculations. Specifically, the control device 60 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores various programs, a RAM (Random Access Memory) used as a work area during program execution, a non-volatile memory that stores various information, and an input / output interface (I / O). Each of the CPU, ROM, RAM, non-volatile memory, and I / O is connected via a bus. And to the I / O, each part of the image forming apparatus 100 such as the electrophotographic photoreceptor 7 (including the drive motor 30), the charging device 8, the exposure device 9, the developing device 11, the transfer charger 40, etc. is connected.

[0173] The CPU executes, for example, a control program of a program (such as an image forming sequence or a recovery sequence) stored in the ROM or non-volatile memory, and controls the operations of each part of the image forming apparatus 100. The RAM is used as a work memory. In the ROM and non-volatile memory, for example, programs executed by the CPU and data necessary for the CPU's processing are stored. Note that the control program and various data may be stored in other storage devices such as a storage unit, or may be acquired from the outside via a communication unit.

[0174] Furthermore, various drives may be connected to the control device 60. Examples of such drives include devices that read data from or write data to computer-readable portable recording media such as flexible disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and USB (Universal Serial Bus) memory. If various drives are provided, a control program may be recorded on a portable recording media and then read and executed by the corresponding drive.

[0175] Figure 5 is a schematic diagram showing another example of the image forming apparatus according to this embodiment. The image forming apparatus 120 shown in Figure 5 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one electrophotographic photoreceptor is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem type.

[0176] The image forming apparatus 100 according to this embodiment is not limited to the above configuration. For example, a first static elimination device may be provided around the electrophotographic photoreceptor 7, downstream of the transfer device 40 in the rotational direction of the electrophotographic photoreceptor 7 and upstream of the cleaning device 13 in the rotational direction of the electrophotographic photoreceptor, to align the polarity of residual toner and make it easier to remove with a cleaning brush. Alternatively, a second static elimination device may be provided downstream of the cleaning device 13 in the rotational direction of the electrophotographic photoreceptor and upstream of the charging device 8 in the rotational direction of the electrophotographic photoreceptor, to eliminate static electricity from the surface of the electrophotographic photoreceptor 7.

[0177] Furthermore, the image forming apparatus 100 according to this embodiment is not limited to the above configuration, and may employ a well-known configuration, for example, an image forming apparatus of the direct transfer type that directly transfers the toner image formed on the electrophotographic photoreceptor 7 to a recording medium. [Examples]

[0178] The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following explanation, unless otherwise specified, "parts" and "%" refer to mass. In the following descriptions, unless otherwise specified, synthesis, manufacturing, processing, and measurement were performed at room temperature (25°C ± 3°C).

[0179] <Example 1> -Formation of the lower layer- Zinc oxide: (Average particle size 70nm: Manufactured by Teika Co., Ltd.: Specific surface area value 15m²) 2 100 parts by mass of (g) was mixed with 500 parts by mass of tetrahydrofuran and stirred. 1.3 parts by mass of silane coupling agent (KBM503: manufactured by Shin-Etsu Chemical Co., Ltd.) was added and the mixture was stirred for 2 hours. Subsequently, the tetrahydrofuran was removed by vacuum distillation, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with silane coupling agent.

[0180] 110 parts by mass of the surface-treated zinc oxide (silane coupling agent surface-treated zinc oxide) was stirred and mixed with 500 parts by mass of tetrahydrofuran. A solution of 0.6 parts by mass of alizarin dissolved in 50 parts by mass of tetrahydrofuran was added, and the mixture was stirred at 50°C for 5 hours. Subsequently, the zinc oxide to which alizarin had been added was filtered off by vacuum filtration, and the mixture was further dried under vacuum at 60°C to obtain alizarin-added zinc oxide.

[0181] A mixture was obtained by mixing 60 parts by mass of alizarin-modified zinc oxide, 13.5 parts by mass of a curing agent (blocked isocyanate Sumijule 3175, manufactured by Sumitomo Bayern Urethanes), 15 parts by mass of butyral resin (Eslec BM-1, manufactured by Sekisui Chemical Co., Ltd.), and 85 parts by mass of methyl ethyl ketone. 38 parts by mass of this mixture was mixed with 25 parts by mass of methyl ethyl ketone, and the mixture was dispersed for 2 hours using a sand mill with 1 mmφ glass beads to obtain a dispersion.

[0182] To the obtained dispersion, 0.005 parts by mass of dioctyltin dilaurate and 40 parts by mass of silicone resin particles (Tospar 145, manufactured by Momentive Performance Materials) were added as catalysts to obtain a coating solution for forming an undercoat. This coating solution was applied by immersion coating onto an aluminum substrate with a diameter of 60 mm, a length of 357 mm, and a wall thickness of 1 mm, and dried and cured at 170°C for 40 minutes to obtain an undercoat with a thickness of 19 μm.

[0183] -Fabrication of a charge generation layer- A mixture consisting of 15 parts by mass of hydroxygallium phthalocyanine, which has diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.3°, 16.0°, 24.9°, and 28.0° in its X-ray diffraction spectrum using Cukα characteristic X-rays as a charge-generating material, 10 parts by mass of vinyl chloride / vinyl acetate copolymer (VMCH, manufactured by NUC Corporation) as a binder resin, and 200 parts by mass of n-butyl acetate was dispersed for 4 hours using glass beads with a diameter of 1 mmφ in a sand mill. To the obtained dispersion, 175 parts by mass of n-butyl acetate and 180 parts by mass of methyl ethyl ketone were added and stirred to obtain a coating solution for forming a charge-generating layer. This coating solution for forming a charge-generating layer was immersed and coated onto a base layer, and dried at room temperature (25°C) to form a charge-generating layer with a film thickness of 0.2 μm.

[0184] -Fabrication of a charge transport layer- First, untreated (hydrophilic) silica particles "Product name: OX50 (Manufactured by Nippon Aerosil Co., Ltd.), specific surface area: 50m²" 2 To 100 parts by mass of " / gnm", 300 parts by mass of a trimethylsilane compound (1,1,1,3,3,3-hexamethyldisilazane (manufactured by Tokyo Chemical Industry Co., Ltd.)) was added as a hydrophobic treatment agent, and the mixture was reacted for 24 hours. The mixture was then filtered to obtain hydrophobic silica particles. These were designated as silica particles (1).

[0185] Next, as the metal oxide particles, 250 parts by mass of tetrahydrofuran was added to 50 parts by mass of silica particles (1), and while maintaining the liquid temperature at 20°C, 25 parts by mass of 4-(2,2-diphenyl ethyl)-4’,4’’-dimethyl-triphenylamine as a charge transport material and 25 parts by mass of bisphenol Z type polycarbonate resin (viscosity average molecular weight: 30000) as a binder resin were added, and they were stirred and mixed for 12 hours to obtain a coating solution for forming a charge transport layer.

[0186] This coating solution for forming a charge transport layer was applied onto the charge generation layer and dried at 135°C for 40 minutes to form a charge transport layer with a film thickness of 30 μm, and an organic photoreceptor (1) was obtained.

[0187] Through the above steps, an organic photoreceptor (1) was obtained in which an undercoat layer, a charge generation layer, and a charge transport layer were laminated in this order on an aluminum substrate.

[0188] - Formation of Inorganic Protection Layer - Next, an inorganic protection layer composed of gallium oxide containing hydrogen was formed on the surface of the organic photoreceptor (1). The formation of this inorganic protection layer was carried out using a film forming apparatus having the configuration shown in FIG. 2.

[0189] First, the organic photoreceptor (1) was placed on the substrate support member 213 in the film forming chamber 210 of the film forming apparatus, and the inside of the film forming chamber 210 was evacuated through the exhaust port 211 until the pressure reached 0.1 Pa. Next, 40% He-diluted oxygen gas (flow rate 1.6 sccm) and hydrogen gas (flow rate 50 sccm) were introduced into the high-frequency discharge tube portion 221 provided with a flat plate electrode 219 having a diameter of 85 mm from the gas introduction tube 220, and a radio wave of 13.56 MHz was set to an output of 150 W by the high-frequency power supply unit 218 and a matching circuit (not shown in FIG. 2), and matching was performed with a tuner to generate a discharge from the flat plate electrode 219. The reflected wave at this time was 0 W. ​​In this state, the organic photoreceptor (1) was rotated at a speed of 500 rpm for 68 minutes to deposit a film, forming an inorganic protective layer with a thickness of 1.5 μm on the surface of the charge transport layer of the organic photoreceptor (1). The surface roughness Ra of the outer surface of the inorganic protective layer was 1.9 nm.

[0190] The elemental composition ratio (oxygen / gallium) of oxygen to gallium in the inorganic protective layer was 1.5.

[0191] Through the above process, an electrophotographic photoreceptor was obtained in which an undercoat layer, a charge generation layer, a charge transport layer, and an inorganic protective layer were sequentially formed on a conductive substrate.

[0192] <Examples 2-31, Comparative Examples 1-4> A photoreceptor was obtained in the same manner as in Example 1, except that the following items were changed according to Table 1. However, in Example 12, TMA (trimethylaluminum gas) was used instead of TMG (trimethylgallium gas). In Table 1, the "O / Ga ratio" for Example 12 refers to the "O / Al ratio". • Film thickness of the charge transport layer • Types and content of metal oxide particles in the charge transport layer • Film thickness of inorganic protective layer • Flow rate ratio of oxygen gas and trimethylgallium gas during inorganic protective layer formation

[0193] <Various Measurements> The following items were measured using the method described above. • Relative permittivity of the charge transport layer and inorganic protective layer • Capacitance of charge transport layer and inorganic protective layer: Indicated as "X1, X2" in Table 1 • Ratio of capacitance between charge transport layer and inorganic protective layer: Indicated as "X1 / X2" in Table 1. • Amount of OH groups in metal oxide particles in the charge transport layer • Composition ratio of oxygen / Group 13 elements (expressed as O / Ga ratio) in the inorganic protective layer

[0194] <Evaluation of photoreceptor performance> [Electrifiable] The chargeability of the photoreceptor in each example was evaluated as follows. The photoreceptors of each example and comparative example were mounted in an image forming apparatus (DocuCentre-V C7775, manufactured by Fujifilm Business Innovation Co., Ltd.). The potential decay of the photoreceptor after charging was monitored at two points evenly spaced along the axial direction of the photoreceptor and classified as follows. The results are shown in Table 1. G1: Uniformly charged to the target charging potential. G2: Approximately charged to the target charging potential. G3: Variation is observed in the charging potential. G4: Does not charge to the target charging potential.

[0195] [Dot reproducibility evaluation] The dot reproducibility of each example was evaluated as follows. The photoreceptors of each example and comparative example were mounted in an image forming apparatus (DocuCentre-V C7775, manufactured by Fujifilm Business Innovation Co., Ltd.) and their dot reproducibility was evaluated according to the following procedure. Specifically, we used 50% halftone images to observe the shape of the dots and evaluated whether there was any dot variation or size variation due to lateral dot flow. G1: No dot variation G2: There is some variation in the dots. G3: Dot variation present G4: Large variation in dot size

[0196] [comprehensive evaluation] Based on the evaluation results for each example of the photoreceptor, the following overall evaluation was made. Based on the evaluation results of chargeability and dot reproducibility, the photoreceptors of each example and each comparative example were classified as follows. A: Excellent in both electrostatic properties and dot reproduction. B: Either the electrostatic properties or the dot reproducibility will decrease, but this is acceptable for practical use. C: Both electrostatic properties and dot reproduction quality are reduced, but this is acceptable for practical use. D: Both electrostatic properties and dot reproducibility are reduced, making it unacceptable for practical use.

[0197] Note that in Table 1, the notation "(Value A)E-(Value B)" means Value A × 10 -(数値B) It means...

[0198] [Table 1]

[0199] The abbreviations listed in Table 1 refer to the following compounds. ·Metal oxide particles Silica particles (1) Hydrophobicity rate 65% Product name: OX50 (Manufactured by Nippon Aerosil Co., Ltd.) Reaction time: 24 hours Silica particles (2) Hydrophobicity 60% Product name: OX50 (Manufactured by Nippon Aerosil Co., Ltd.) Reaction time: 20 hours Silica particles (3) Hydrophobicity rate 55% Product name: OX50 (Manufactured by Nippon Aerosil Co., Ltd.) Reaction time: 15 hours Other than silica: Titanium oxide

[0200] From the above results, it can be seen that the photoreceptor of the example is superior to the photoreceptor of the comparative example in both chargeability and dot reproducibility.

[0201] This embodiment includes the following aspects. (((1))) The device comprises a conductive substrate, a charge generation layer disposed on the conductive substrate, a charge transport layer disposed on the charge generation layer, and an inorganic protective layer disposed on the charge transport layer, wherein the capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10⁻⁶. -6 (F / m 2 ) 1.90 × 10 -6 (F / m 2 ) or less, and the capacitance (X2) per unit area of ​​the inorganic protective layer is 2.40 × 10 -5 (F / m 2 ) Above 1.10 × 10 -4 (F / m 2 ) an electrophotographic photoreceptor. (((2))) The capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10 -6 (F / m 2 ) Above 1.46 × 10 -6 (F / m 2 ) or less, and the capacitance (X2) per unit area of ​​the inorganic protective layer is 2.40 × 10 -5 (F / m 2 ) 5.30 x 10 -5 (F / m 2 The following is the electrophotographic photoreceptor described in (((1))). (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), wherein the ratio (X1 / X2) of the capacitance per unit area of ​​the charge transport layer (X1) to the capacitance per unit area of ​​the inorganic protective layer (X2) is 0.010 or more and 0.070 or less. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the inorganic protective layer is an inorganic protective layer containing oxygen and a group 13 element. (((5))) The electrophotographic photoreceptor according to ((4)), wherein the elemental composition ratio (oxygen / group 13 element) of the inorganic protective layer is 1.4 or more and 1.5 or less. (((6))) The electrophotographic photoreceptor according to any one of (((1))) to (((5))) wherein the charge transport layer contains metal oxide particles. (((7))) The electrophotographic photoreceptor according to (((6))), wherein the metal oxide particles are silica particles. (((8))) The electrophotographic photoreceptor according to (((7))), wherein the content of the metal oxide particles in the charge transport layer is 40% by volume or more and 60% by volume or less. (((9))) The electrophotographic photoreceptor according to (((6))), wherein the hydrophobicity rate of the metal oxide particles in the charge transport layer is 60% or more. (((10))) The electrophotographic photoreceptor according to any one of (((1))) to (((9))), wherein the thickness of the charge transport layer is 16 μm or more and 30 μm or less. (((11))) The electrophotographic photoreceptor according to any one of (((1))) to (((10))), wherein the thickness of the inorganic protective layer is 1.0 μm or more and 4.0 μm or less. (((12))) A process cartridge for attaching to and detaching from an image forming apparatus, comprising an electrophotographic photoreceptor as described in any one of items (((1))) to (((11))). (((13))) An image forming apparatus comprising: an electrophotographic photoreceptor as described in any one of (((1))) to (((11))); a charging device for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing 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 for transferring the toner image to the surface of a recording medium.

[0202] The effects of the above embodiment are as follows: According to the invention of (((1))), the invention comprises a conductive substrate, a charge generation layer disposed on the conductive substrate, a charge transport layer disposed on the charge generation layer, and an inorganic protective layer disposed on the charge transport layer, wherein the capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10 -6 (F / m 2 ) less than, or 1.90 × 10 -6 (F / m 2 ) or the capacitance per unit area of ​​the inorganic protective layer (X2) is 2.40 × 10 -5 (F / m 2 ) less than 1.10 × 10 -4 (F / m 2 Compared to cases where the value exceeds the specified limit, this provides an electrophotographic photoreceptor that suppresses the decrease in charge potential and exhibits excellent dot reproducibility. According to the invention of (((2))), the capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10 -6 (F / m 2 ) less than 1.46 × 10-6 (F / m 2 ) or the capacitance per unit area of ​​the inorganic protective layer (X2) is 2.40 × 10 -5 (F / m 2 ) less than, or 5.30 × 10 -5 (F / m 2 Compared to cases where the value exceeds the specified limit, this provides an electrophotographic photoreceptor that suppresses the decrease in charge potential and exhibits excellent dot reproducibility. According to the invention of (((3))), compared to cases where the ratio (X1 / X2) of the capacitance per unit area of ​​the charge transport layer (X1) to the capacitance per unit area of ​​the inorganic protective layer (X2) is less than 0.010 or greater than 0.070, an electrophotographic photoreceptor is provided that suppresses the decrease in charging potential and has excellent dot reproducibility. According to the invention of (((4))), compared to the case where the inorganic protective layer is not an inorganic protective layer containing oxygen and group 13 elements, an electrophotographic photoreceptor is provided that suppresses the decrease in charge potential and has excellent dot reproducibility. According to the invention of (((5))), compared to cases where the elemental composition ratio (oxygen / group 13 elements) of oxygen and group 13 elements in the inorganic protective layer is less than 1.4 or greater than 1.5, an electrophotographic photoreceptor is provided that suppresses the decrease in charging potential and has excellent dot reproducibility. According to the invention of (((6))), an electrophotographic photoreceptor is provided that suppresses the decrease in charging potential and exhibits excellent dot reproducibility compared to the case in which the charge transport layer does not contain metal oxide particles. According to the invention of (((7))), compared to the case where the metal oxide particles are titanium oxide particles, an electrophotographic photoreceptor is provided that suppresses the decrease in charge potential and has excellent dot reproducibility. According to the invention of (((8))), compared to cases where the content of metal oxide particles in the charge transport layer is less than 40 volume% or more than 60 volume%, an electrophotographic photoreceptor is provided that suppresses the decrease in charging potential and has excellent dot reproducibility. According to the invention of (((9))), compared to the case where the hydrophobicity rate of metal oxide particles in the charge transport layer is less than 60%, a decrease in the charging potential is suppressed and an electrophotographic photoreceptor with excellent dot reproducibility is provided. According to the invention of (((10))), compared to cases where the thickness of the charge transport layer is less than 16 μm or more than 30 μm, an electrophotographic photoreceptor is provided that suppresses the decrease in charging potential and has excellent dot reproducibility. According to the invention of (((11))), compared to cases where the thickness of the inorganic protective layer is less than 1.0 μm or greater than 4.0 μm, an electrophotographic photoreceptor is provided that suppresses the decrease in charging potential and has excellent dot reproducibility. According to the invention of (((12))) or (((13))), the invention comprises a conductive substrate, a charge generation layer disposed on the conductive substrate, a charge transport layer disposed on the charge generation layer, and an inorganic protective layer disposed on the charge transport layer, wherein the capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10 -6 (F / m 2 ) less than, or 1.90 × 10 -6 (F / m 2 ) or the capacitance per unit area of ​​the inorganic protective layer (X2) is 2.40 × 10 -5 (F / m 2 ) less than 1.10 × 10 -4 (F / m 2 Compared to cases where the charge potential exceeds a certain value, a process cartridge or image forming apparatus is provided that has an electrophotographic photoreceptor that suppresses the decrease in charge potential and has excellent dot reproducibility. [Explanation of symbols]

[0203] 1. Conductive substrate 2 Undercoat layer 3. Charge generation layer 4 Charge transport layer 5 Photosensitive layer 6 Inorganic protective layer 7. Electrophotographic photoreceptor 8. Charging device 9. Exposure apparatus 10A photoreceptor 11. Developing device 13 Cleaning device 14 Lubricant 40 Transfer device 50 Intermediate Transfer 100 Image forming apparatus 120 Image forming apparatus 131 Cleaning Blade 132. Fibrous material (rolled) 133. Fibrous member (flat brush shape) 300 Process Cartridges 210 Deposition chamber 211 Exhaust port 212 Base Rotating Section 213 Base support member 214 Base 215 Gas inlet pipe 216 Shower Nozzle 217 Plasma Diffusion Section 218 High-frequency power supply unit 219 Flat electrode 220 Gas inlet pipe 221 High-frequency discharge tube section 222 High-Frequency Coil 223 Quartz tube

Claims

1. A conductive substrate, A charge generation layer disposed on the conductive substrate, A charge transport layer disposed on the charge generation layer, An inorganic protective layer disposed on the charge transport layer, Equipped with, The capacitance (X1) per unit area of ​​the charge transport layer is 0.90 × 10 －６ (F / m) ２ ) Above 1.90 x 10 －６ (F / m) ２ ) or less, and the capacitance (X2) per unit area of ​​the inorganic protective layer is 2.40 × 10 －５ (F / m) ２ ) Above 1.10 × 10 －４ (F / m) ２ ) an electrophotographic photoreceptor.

2. The capacitance per unit area (X1) of the charge transport layer is 0.90 × 10 －６ (F / m ２ ) or more and 1.46 × 10 －６ (F / m ２ ) or less, and the capacitance per unit area (X2) of the inorganic protective layer is 2.40 × 10 －５ (F / m ２ ) or more and 5.30 × 10 －５ (F / m ２ ) or less. The electrophotographic photoreceptor according to claim 1.

3. The electrophotographic photoreceptor according to claim 1, wherein the ratio (X1 / X2) of the capacitance per unit area of ​​the charge transport layer (X1) to the capacitance per unit area of ​​the inorganic protective layer (X2) is 0.010 or more and 0.070 or less.

4. The electrophotographic photoreceptor according to claim 1, wherein the inorganic protective layer is an inorganic protective layer containing oxygen and a group 13 element.

5. The electrophotographic photoreceptor according to claim 4, wherein the elemental composition ratio (oxygen / group 13 element) of the inorganic protective layer is 1.4 or more and 1.5 or less.

6. The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer contains metal oxide particles.

7. The electrophotographic photoreceptor according to claim 6, wherein the metal oxide particles are silica particles.

8. The electrophotographic photoreceptor according to claim 7, wherein the content of the metal oxide particles in the charge transport layer is 40% by volume or more and 60% by volume or less.

9. The electrophotographic photoreceptor according to claim 6, wherein the degree of hydrophobicity of the metal oxide particles in the charge transport layer is 60% or more.

10. The electrophotographic photoreceptor according to claim 1, wherein the thickness of the charge transport layer is 16 μm or more and 30 μm or less.

11. The electrophotographic photoreceptor according to claim 1, wherein the thickness of the inorganic protective layer is 1.0 μm or more and 4.0 μm or less.

12. The electrophotographic photoreceptor is provided according to any one of claims 1 to 11. A process cartridge that is attached to and detached from an image forming apparatus.

13. An electrophotographic photoreceptor according to any one of claims 1 to 11, A charging device for charging the surface of the electrophotographic photoreceptor, An electrostatic latent image forming apparatus for forming 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 an electrophotographic photoreceptor using a developer containing toner to form a toner image, A transfer device for transferring the toner image onto the surface of a recording medium, An image forming apparatus equipped with the following features.

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