Conductive substrate for electrophotographic photoreceptor, electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide a conductive substrate for electrophotographic photoreceptors that can produce electrophotographic photoreceptors with suppressed noise. [Solution] A conductive substrate for an electrophotographic photoreceptor, comprising a cylindrical body, a first stepped portion provided on the inner circumferential surface of one axial end of the cylindrical body, wherein the inner diameter of the cylindrical body at the axial end is larger than the inner diameter of the cylindrical body at the axial center, and a second stepped portion provided on the inner circumferential surface of the other axial end of the cylindrical body, wherein the inner diameter of the cylindrical body at the other axial end is larger than the inner diameter of the cylindrical body at the axial center, and the lengths of the first stepped portion and the second stepped portion are different.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses "an electrophotographic photoreceptor in which a photoconductive layer is formed on a drum-shaped substrate, wherein an inner surface of the drum-shaped substrate has, on an end portion side thereof, a plurality of stepped portions that are stepped so that an inner diameter thereof expands toward the end."

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a conductive substrate for an electrophotographic photoreceptor capable of obtaining an electrophotographic photoreceptor in which noise is suppressed as compared with a case where lengths of a first stepped portion and a second stepped portion provided on inner peripheral surfaces of both end portions of a cylindrical body are the same.

Means for Solving the Problems

[0005] Means for solving the above problems include the following aspects. <1> A cylindrical body, a first stepped portion provided on an inner peripheral surface of one axial end portion of the cylindrical body, wherein an inner diameter of the cylindrical body at the one axial end portion is larger than an inner diameter of the cylindrical body at an axial central portion, and a second stepped portion provided on an inner peripheral surface of the other axial end portion of the cylindrical body, wherein an inner diameter of the cylindrical body at the other axial end portion is larger than an inner diameter of the cylindrical body at an axial central portion, and having A conductive substrate for an electrophotographic photoreceptor, in which the lengths of the first stepped portion and the second stepped portion are different. <2> The conductive substrate for an electrophotographic photoreceptor according to <1>, in which the difference in length between the first stepped portion and the second stepped portion is 13 mm or more and 79 mm or less in absolute value. <3> The conductive substrate for an electrophotographic photoreceptor according to <2>, in which the difference in length between the first stepped portion and the second stepped portion is 13 mm or more and 53 mm or less in absolute value. <4> The conductive substrate for an electrophotographic photoreceptor according to any one of <1> to <3>, in which the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is 0.05 or more and 0.31 or less. <5> The conductive substrate for an electrophotographic photoreceptor according to <4>, in which the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is 0.15 or more and 0.21 or less. <6> An electrophotographic photoreceptor comprising a conductive substrate for an electrophotographic photoreceptor according to any one of <1> to <5>, and a photosensitive layer provided on the conductive substrate for an electrophotographic photoreceptor. An electrophotographic photoreceptor having the above components. <7> A process cartridge that is attached to and detached from an image forming apparatus and includes the electrophotographic photoreceptor according to <6>. An image forming apparatus comprising: <8> The electrophotographic photoreceptor according to <6>, a charging device that applies a current in which direct current is superimposed with alternating current to the surface of the electrophotographic photoreceptor to charge the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, a transfer device that transfers the toner image to the surface of a recording medium, and the above components. <9> When X is the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body, the value of X / (the frequency of the AC × 2) is greater than 0, i.e., 1.20 × 10 -4 The following is <8> The image forming apparatus described above. [Effects of the Invention]

[0006] <1> According to the present invention, a conductive substrate for an electrophotographic photoreceptor is provided that yields an electrophotographic photoreceptor in which noise is suppressed compared to the case where the lengths of the first stepped portion and the second stepped portion provided on the inner circumferential surface of both ends of the cylindrical body are the same. <2> According to the present invention, a conductive substrate for an electrophotographic photoreceptor is provided that yields an electrophotographic photoreceptor in which noise is suppressed compared to cases where the difference in length between the first stepped portion and the second stepped portion is less than 13 mm or greater than 79 mm in absolute value. <3> According to the present invention, a conductive substrate for an electrophotographic photoreceptor is provided that yields an electrophotographic photoreceptor with reduced noise compared to cases where the difference in length between the first stepped portion and the second stepped portion is less than 13 mm or greater than 53 mm in absolute value. <4> According to the present invention, a conductive substrate for an electrophotographic photoreceptor is provided that yields an electrophotographic photoreceptor with reduced noise compared to cases where the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is less than 0.05 or greater than 0.31. <5> According to the present invention, a conductive substrate for an electrophotographic photoreceptor is provided that yields an electrophotographic photoreceptor with reduced noise compared to cases where the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is less than 0.15 or greater than 0.21. <6> , <7> , or <8> According to the present invention, an electrophotographic photoreceptor, a process cartridge, or an image forming apparatus is provided that has a conductive substrate for an electrophotographic photoreceptor that provides an electrophotographic photoreceptor with suppressed noise compared to the case in which a conductive substrate for an electrophotographic photoreceptor is applied in which the lengths of the first stepped portion and the second stepped portion provided on the inner circumferential surface of both ends of the cylindrical body are the same. <9> According to the invention, the value of X / (AC frequency × 2) is 1.20 × 10 -4An image forming apparatus is provided that has an electrophotographic photoreceptor that suppresses noise compared to cases where the noise level exceeds a certain threshold. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to this embodiment. [Figure 2] This is a schematic cross-sectional view showing another example of the layer configuration of the electrophotographic photoreceptor according to this embodiment. [Figure 3] This is a schematic diagram showing an example of an image forming apparatus according to this embodiment. [Figure 4] This is a schematic cross-sectional view showing an example of a conductive substrate for an electrophotographic photoreceptor 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 embodiments.

[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.

[0010] 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.

[0011] In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that the purpose of the process is achieved.

[0012] 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.

[0013] 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 disclosure, if there are multiple types of the substance corresponding to each component in the composition, unless otherwise specified, it means the total amount of those multiple types of substances present in the composition.

[0014] In this specification, "electrophotographic photoreceptor" is also referred to as "photoreceptor." "Conductive substrate for electrophotographic photoreceptors" is also referred to as "conductive substrate."

[0015] <Conductive substrate for electrophotographic photoreceptor> The conductive substrate 110 according to this embodiment includes, for example, a cylindrical body 112, a first stepped portion 114A, and a second stepped portion 114B, as shown in Figure 4. The first stepped portion 114A is provided on the inner circumferential surface of one axial end 112A of the cylindrical body 112, and is a stepped portion in which the inner diameters φA1 and φA2 of the cylindrical body 112 at the axial end 112A are larger than the inner diameter φ1 of the cylindrical body 112 at the axial central portion 112C. The second stepped portion 114B is provided on the inner circumferential surface of the other axial end 112B of the cylindrical body 112, and is a stepped portion in which the inner diameters φB1 and φB2 of the cylindrical body 112 at the other axial end 112B are larger than the inner diameter φ1 of the cylindrical body 112 at the central axial portion 112C. Furthermore, the length LA1 of the first stepped section 114A and the length LB1 of the second stepped section 114B are different. In Figure 4, φ2 represents the outer diameter of the cylindrical body 112.

[0016] The conductive substrate 110 according to this embodiment, with the above configuration, provides an electrophotographic photoreceptor in which noise is suppressed. The reason for this is presumed to be as follows.

[0017] Conventionally, there are image forming apparatuses that use a charging device to apply a current, which is a combination of direct current and alternating current, to the surface of a photoreceptor, thereby charging the surface of the photoreceptor (hereinafter referred to as the "AC charging method"). Adopting an image forming apparatus using the AC charging method has the advantage of improving the stability of photoreceptor charging, resulting in improved image quality, stability, and faster operation of the apparatus.

[0018] However, in AC-charging image forming apparatuses, an electrostatic attraction force is generated by the alternating electric field between the charged component and the photoreceptor. As a result, noise at integer multiples of the frequency of the AC current applied by the charged component may be generated due to the resonance of the photoreceptor caused by the electrostatic attraction force. The frequency of the alternating current applied by the charged component depends on the image formation speed. Therefore, to suppress noise, a conductive substrate with a natural frequency that does not resonate at a specific alternating current frequency is effective. Conventional techniques adjusted the natural vibration of the photoreceptor by inserting cylindrical vibration damping materials of various materials or by increasing the thickness of the base material. In contrast, in this embodiment, the conductive substrate 110 in the photoreceptor is made such that the length LA1 of the first stepped portion 114A and the length LB1 of the second stepped portion 114B are different. In other words, the shape of the substrate is asymmetrical. This makes it possible to adjust the natural frequency of the photoreceptor for any frequency range of the AC current applied by the charged component. This is because the asymmetrical shape of the substrate is thought to suppress deformation of the photoreceptor due to vibration when AC current is applied. As a result, noise, especially harmonics (e.g., the second harmonic) of the AC frequency, is suppressed.

[0019] From the above, it is presumed that the conductive substrate according to this embodiment will yield an electrophotographic photoreceptor with suppressed noise.

[0020] The details of the conductive substrate according to this embodiment will be described below. Reference numerals will be omitted when describing the details of the conductive substrate.

[0021] (Cylindrical body> Examples of cylindrical bodies include conductive metal drums containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Here, "conductive" means having a volume resistivity of 10⁻¹⁰ 13 This refers to a value less than Ω·cm.

[0022] The axial length of the cylindrical body (see L1 in Figure 4) is, for example, 251.5 mm or more and 853 mm or less, preferably 253 mm or more and 342 mm or less. The thickness of the cylindrical body, excluding the first and second stepped portions (see T1 in Figure 4), is, for example, 0.7 mm or more and 1.8 mm or less, preferably 0.75 mm or more and 1.60 mm or less. In the cylindrical body, the inner diameter other than the first and second stepped sections (see φ1 in Figure 4), that is, the inner diameter of the cylindrical body in the axial center, shall be, for example, 26.8 mm or more and 28.4 mm or less. The axial length, thickness, and inner diameter of the cylindrical body are set according to the application of the photoreceptor.

[0023] (Stepped section) The first stepped portion is provided on the inner circumferential surface of one end of the cylindrical body in the axial direction. In the first stepped portion, the inner diameter of the cylindrical body at one end in the axial direction is larger than the inner diameter of the cylindrical body at the axial center. The second stepped portion is provided on the inner circumferential surface of the other end of the cylindrical body in the axial direction. In the second stepped portion, the inner diameter of the cylindrical body at the other end in the axial direction is larger than the inner diameter of the cylindrical body at the axial center.

[0024] The length of the first step (see LA1 in Figure 4) and the length of the second step (see LB1 in Figure 4) are different. By making the lengths of the first and second steps different, noise can be suppressed. Specifically, the difference in length between the first stepped section and the second stepped section (see difference LA1-LB1 in Figure 4) is preferably set within the range of 13 mm to 79 mm in absolute value, and more preferably within the range of 39 mm to 53 mm in absolute value. Noise is more easily suppressed when the difference in length between the first and second steps is 13 mm or more in absolute terms. Noise is more easily suppressed when the difference in length between the first and second steps is 79 mm or less in absolute value.

[0025] Here, the lengths of the first and second stepped sections are the lengths along the axial direction of the cylindrical body, and refer to the lengths from the starting point of the enlargement of the inner diameter of the cylindrical body to the axial end face of the cylindrical body.

[0026] The ratio of the absolute value of the difference in length between the first stepped section and the second stepped section to the axial length of the cylindrical body (see L1 in Figure 4) ((LA1-LB1) / L1) is preferably 0.05 or more and 0.31 or less, and more preferably 0.15 or more and 0.21 or less. By setting this ratio within the above range, it is believed that deformation due to vibration of the photoreceptor when AC current is applied can be suppressed. As a result, noise can be reduced. When the length of the first stepped section is longer than the length of the second stepped section, the ratio of the lengths of the first stepped section to the second stepped section (LA1 / LB1) is preferably 1.001 or more and 3.963 or less, and more preferably 1.900 or more and 3.000 or less. By setting the above ratio within the above range, it is believed that deformation due to vibration of the photoreceptor when AC current is applied can be suppressed. As a result, noise can be reduced.

[0027] The first and second stepped sections may be configured such that the inner diameter of the cylindrical body is enlarged in one step, or they may be configured such that the inner diameter of the cylindrical body is enlarged in two or more steps. In the conductive substrate shown in Figure 4, the first and second stepped sections are shown in a configuration where the inner diameter of the cylindrical body is enlarged in two steps. In Figure 4, LA11 indicates the first step where the inner diameter of the cylindrical body is enlarged in the first step from the axial center of the cylindrical body, and LA12 indicates the first step where the inner diameter of the cylindrical body is enlarged in the second step from the axial center of the cylindrical body. Then, φA1 indicates the inner diameter of the first step where the inner diameter of the cylindrical body is enlarged in the first step, and φA2 indicates the inner diameter of the first step where the inner diameter of the cylindrical body is enlarged in the second step. In Figure 4, LB11 indicates the second step portion where the inner diameter of the cylindrical body is expanded in the first step from the axial center of the cylindrical body, and LB12 indicates the second step portion where the inner diameter of the cylindrical body is expanded in the second step from the axial center of the cylindrical body. Then, φB1 indicates the inner diameter of the second step portion where the inner diameter of the cylindrical body is expanded in the first step, and φB2 indicates the inner diameter of the second step portion where the inner diameter of the cylindrical body is expanded in the second step.

[0028] The difference between the inner diameter of the cylindrical body at the first and second stepped sections (see φA1, φA2, φB1, and φB2 in Figure 4) and the inner diameter of the cylindrical body outside of the first and second stepped sections (see φ1 in Figure 4) is set according to the size of the flange fitting portion.

[0029] In this case, if the first and second stepped sections are configured such that the inner diameter of the cylindrical body is enlarged in two or more stages, the inner diameter and length of the cylindrical body at each stage are also set according to the size of the flange fitting portion.

[0030] Furthermore, it is preferable that the dimensions of the first and second stepped sections are the same except for the lengths of the first and second stepped sections.

[0031] (Modes of conductive substrates) When an electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate (i.e., a cylindrical body, hereafter the same) is preferably roughened to a center-line average roughness Ra of 0.04 μm or more and 0.5 μm or less in order to suppress interference fringes that occur when irradiated with laser light. Note that when non-interfering light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for extending the lifespan by suppressing the occurrence of defects due to surface irregularities of the conductive substrate.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] <Electrophotographic photoconductor> The photoreceptor according to this embodiment comprises a conductive substrate for an electrophotographic photoreceptor according to this embodiment, and a photosensitive layer provided on the conductive substrate for an electrophotographic photoreceptor.

[0039] The photosensitive layer may be a single-layer photosensitive layer that integrates the functions of a charge generating material and a charge transporting material within the same photosensitive layer, or it may be a multilayer photosensitive layer with separate functions for the charge generating layer and the charge transporting layer. When the photosensitive layer is a multilayer photosensitive layer, the order of the charge generation layer and the charge transport layer is not particularly limited, but it is preferable that the photoreceptor has a configuration in which the charge generation layer and the charge transport layer are arranged in this order on a conductive substrate. The photoreceptor may also contain layers other than these.

[0040] Figure 1 is a schematic cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor according to this embodiment. The photoreceptor 107A shown in Figure 1 has a structure in which a base layer 101 is provided on a conductive substrate 104, and a charge generation layer 102, a charge transport layer 103, and a protective layer 106 are sequentially formed thereon. In the photoreceptor 107A, a photosensitive layer 105 is configured in which the functions of the charge generation layer 102 and the charge transport layer 103 are separated.

[0041] Figure 2 is a schematic cross-sectional view showing another example of the layer configuration of an electrophotographic photoreceptor according to this embodiment. The photoreceptor 107B shown in Figure 2 has a structure in which an undercoat layer 101 is provided on a conductive substrate 104, and a photosensitive layer 105 and a protective layer 106 are formed sequentially. In the photoreceptor 107B, a single-layer photosensitive layer is constructed in which a charge generating material and a charge transporting material are contained in the same photosensitive layer 105 and their functions are integrated. In the electrophotographic photoreceptor according to this embodiment, the undercoat layer 101 and the protective layer 106 are provided as needed, and may or may not be provided.

[0042] The details of the photoreceptor in this embodiment will be described below, but reference numerals will be omitted.

[0043] (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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] (subbing layer) The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0052] 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 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.

[0053] 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).

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry or wet method.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Methods for attaching electron-accepting compounds to the surface of inorganic particles include, for example, dry methods or wet methods.

[0065] The dry method involves, for example, adding an electron-accepting compound, either directly or dissolved in an organic solvent, dropwise while stirring inorganic particles with a mixer that has a high shear force, or spraying it with dry air or nitrogen gas, to adhere the electron-accepting compound to the surface of the inorganic particles. When adding or spraying the electron-accepting compound, it is preferable to do so at a temperature below the boiling point of the solvent. After adding or spraying the electron-accepting compound, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] Examples of aluminum chelating compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0076] These additives may be used individually or as a mixture or polycondensate of multiple compounds.

[0077] 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.

[0078] There are no particular restrictions on the formation of the undercoat, 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.

[0079] Solvents for preparing the coating solution for forming the undercoat include known organic solvents such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] (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.

[0084] Among these, the intermediate layer is preferably a layer containing an organometallic compound that contains zirconium atoms or silicon atoms.

[0085] 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.

[0086] 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.

[0087] (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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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" refers to a volume resistivity of 10 13 This refers to a value of Ω·cm or greater. These binder resins can be used individually or in combination of two or more types.

[0094] 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.

[0095] The charge generation layer may also contain other well-known additives.

[0096] 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.

[0097] 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, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene. These solvents may be used individually or in mixtures of two or more.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] (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.

[0102] Examples of the charge transport material 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 electron transport compounds such as ethylene compounds. Examples of the charge transport material also 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 alone or in combination of two or more, but are not limited thereto.

[0103] From the viewpoint of charge mobility, as the charge transport material, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2) are preferable.

[0104] [Chemical formula]

[0105] In the structural formula (a-1), Ar T1 , Ar T2 , and Ar T3 each independently represents 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 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. 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.

[0106] [ka]

[0107] In structural formula (a-2), R T91 and R T92 Each of these independently represents 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. T101 , R T102 , R T111 and R T112 Each of these independently consists of 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, and -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ) shows R T12 , R T13 , R T14 , R T15 and R T16 Each 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.

[0108] 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.

[0109] 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. The polymer charge transport material may be used alone, or it may be used in combination with a binder resin.

[0110] 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.

[0111] The charge transport layer may also contain other well-known additives.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] The thickness of the charge transport layer is set, for example, preferably within the range of 5 μm to 50 μm, and more preferably within the range of 10 μm to 30 μm.

[0116] (protective layer) A protective layer is provided on the photosensitive layer as needed. The protective layer is provided, for example, to prevent chemical changes in the photosensitive layer during electrostatic charging, or to further improve the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a protective layer composed of a cured film (crosslinked film). Examples of such layers include those shown in 1) or 2) below.

[0117] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton within the same molecule (i.e., a layer containing a polymer or crosslinked form of the reactive group-containing charge transport material). 2) A layer composed of a cured film of a composition comprising a non-reactive charge transport material and a non-charge transport material containing reactive groups that does not have a charge transport skeleton but has reactive groups (i.e., a layer comprising a non-reactive charge transport material and a polymer or crosslinked form of the non-charge transport material containing reactive groups).

[0118] The reactive groups in the reactive group-containing charge transport material include chain polymerizable groups, epoxy groups, -OH, -OR [where R represents an alkyl group], -NH2, -SH, -COOH, and -SiR. Q1 3-Qn (OR Q2 ) Qn [However, R Q1 R represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group. Q2 Examples of well-known reactive groups include hydrogen atoms, alkyl groups, and trialkylsilyl groups. Qn represents an integer from 1 to 3.

[0119] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, for example, a functional group having at least one carbon double bond. Specifically, examples include groups containing at least one selected from vinyl groups, vinyl ether groups, vinyl thioether groups, styryl groups (vinyl phenyl groups), acryloyl groups, methacryloyl groups, and their derivatives. Among these, the chain polymerizable group is preferably a group containing at least one selected from vinyl groups, styryl groups (vinyl phenyl groups), acryloyl groups, methacryloyl groups, and their derivatives, due to its excellent reactivity.

[0120] The charge-transporting skeleton of the reactive group-containing charge-transporting material is not particularly limited as long as it is a known structure in electrophotographic photoreceptors. Examples include skeletons derived from nitrogen-containing hole-transporting compounds such as triarylamine compounds, benzidine compounds, and hydrazone compounds, in which the nitrogen atom is conjugated. Among these, the triarylamine skeleton is preferred.

[0121] These reactive groups and charge-transporting skeletons, including reactive group-containing charge transport materials, non-reactive charge transport materials, and reactive group-containing non-charge transport materials, can be selected from well-known materials.

[0122] The protective layer may also contain other well-known additives.

[0123] There are no particular restrictions on the formation of the protective layer, and well-known formation methods can be used. For example, it can be formed by adding the above components to a solvent to create a protective layer coating solution, drying the coating, and then performing a curing treatment such as heating as necessary.

[0124] Solvents for preparing coating solutions for forming a protective layer include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; cellosolve solvents such as ethylene glycol monomethyl ether; and alcohol solvents such as isopropyl alcohol and butanol. These solvents can be used individually or in combination of two or more. Furthermore, the coating solution for forming the protective layer may be a solvent-free coating solution.

[0125] Conventional methods for applying a protective layer-forming coating solution onto a photosensitive layer (e.g., a charge transport layer) include immersion coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating.

[0126] The thickness of the protective layer is set, for example, preferably within the range of 1 μm to 20 μm, and more preferably within the range of 2 μm to 10 μm.

[0127] (Single-layer photosensitive layer) A single-layer photosensitive layer (charge generation / charge transport layer) is, for example, a layer comprising a charge generation material, a charge transport material, and, if necessary, a binder resin and other well-known additives. These materials are the same as those described for the charge generation layer and the charge transport layer. Furthermore, the content of the charge-generating material in the single-layer photosensitive layer is preferably 0.1% to 10% by mass, and more preferably 0.8% to 5% by mass, relative to the total solid content. In addition, the content of the charge-transporting material in the single-layer photosensitive layer is preferably 5% to 50% by mass, relative to the total solid content. The method for forming a single-layer photosensitive layer is the same as the method for forming a charge generation layer or a charge transport layer. The thickness of the single-layer photosensitive layer is, for example, preferably 5 μm to 50 μm, and more preferably 10 μm to 40 μm.

[0128] [Image forming apparatus (and process cartridge)] The image forming apparatus according to this embodiment comprises an electrophotographic photoreceptor, a charging device, an electrostatic latent image forming device, a developing device, and a transfer device. A charging device is a device that charges the surface of an electrophotographic photoreceptor by applying an electric current, which is a combination of direct current and alternating current, to the surface of the electrophotographic photoreceptor. The electrostatic latent image forming apparatus is a device that forms an electrostatic latent image on the surface of the charged electrophotographic photoreceptor. A developing device is a device that uses a developer containing toner to develop the electrostatic latent image formed on the surface of an electrophotographic photoreceptor, thereby forming a toner image. A transfer device is a device that transfers a toner image onto the surface of a recording medium. Furthermore, the electrophotographic photoreceptor according to the present embodiment described above is used as the electrophotographic photoreceptor.

[0129] The image forming apparatus according to this embodiment includes a fixing device 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 device for cleaning the surface of the electrophotographic photoreceptor after the transfer of the toner image and before it is charged; a static elimination device 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.

[0130] In the case of an intermediate transfer method apparatus, the transfer apparatus may be configured to include, for example, an intermediate transfer body on which a toner image is transferred; a primary transfer apparatus that first transfers the toner image formed on the surface of an electrophotographic photoreceptor to the surface of the intermediate transfer body; and a secondary transfer apparatus that secondarily transfers the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium.

[0131] 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).

[0132] In the image forming apparatus according to this embodiment, for example, the part equipped with an 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 equipped with an 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 device, an electrostatic latent image forming device, a developing device, and a transfer device.

[0133] 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.

[0134] Figure 3 is a schematic diagram showing an example of an image forming apparatus according to this embodiment. As shown in Figure 3, the image forming apparatus 10 according to this embodiment is provided with, for example, a photoreceptor 12. The photoreceptor 12 is cylindrical and is connected to a drive unit 27 such as a motor via a drive force transmission member (not shown) such as a gear. The photoreceptor 12 is rotationally driven by the drive unit 27 around a rotation axis indicated by a black dot. In the example shown in Figure 3, it is rotationally driven in the direction of arrow A.

[0135] Around the photoreceptor 12, for example, a charging device 15 (an example of a charging device), an electrostatic image forming device 16 (an example of an electrostatic image forming device), a developing device 18 (an example of a developing device), a transfer device 31 (an example of a transfer device), a cleaning device 22 (an example of a cleaning device), and a static elimination device 24 are arranged in order along the rotational direction of the photoreceptor 12. The image forming apparatus 10 is also equipped with a fixing device 26 having a fixing member 26A and a pressurizing member 26B positioned in contact with the fixing member 26A. Furthermore, the image forming apparatus 10 has a control device 36 that controls the operation of each device (each part). The image forming unit includes the photoreceptor 12, the charging device 15, the electrostatic image forming device 16, the developing device 18, the transfer device 31, and the cleaning device 22.

[0136] In the image forming apparatus 10, at least the photoreceptor 12 may be provided as a process cartridge integrated with other devices.

[0137] The details of each device (part) of the image forming apparatus 10 will be described below.

[0138] [Charging device] The charging device 15 charges the surface of the photoreceptor 12. Specifically, it charges the surface of the photoreceptor 12 by applying a current which is a direct current superimposed on an alternating current. The charging device 15 includes, for example, a contact-type charging member 14 and a power supply 28. The charging member 14 is a contact-type charging member that is provided in contact with the surface of the photoreceptor 12 and charges the surface of the photoreceptor 12. The power supply 28 is a power supply that applies a voltage to the charged member 14, which is a DC voltage superimposed with an AC voltage. The power supply 28 is electrically connected to the charged element 14. The power supply 28 applies a voltage to the charging member 14 that is a combination of a DC voltage and an AC voltage. The charging member 14 then applies a current, which is a combination of a DC voltage and an AC voltage, to the surface of the photoreceptor 12. This charges the surface of the photoreceptor 12.

[0139] Examples of contact-type charging members 14 include contact-type chargers using conductive charging rolls, charging brushes, charging films, charging rubber blades, charging tubes, etc.

[0140] The DC voltage applied to the photoreceptor 12 should be between 400V and 600V (preferably between 450V and 550V). The peak voltage value V in the AC applied to the photoreceptor 12. pp The peak-to-peak voltage should be between 0V and 100V. The frequency of the alternating current applied to the photoreceptor 12 should be between 0 Hz and 3000 Hz (preferably between 1250 Hz and 1750 Hz).

[0141] Here, if X is the ratio of the absolute value of the difference in length between the first and second stepped sections to the axial length of the cylindrical body, then the value of X / (AC frequency × 2) is greater than 0, i.e., 1.20 × 10 -4 Preferably, it is 0.17 × 10 -4 The above is 0.83 × 10 -4 The following are preferable. Noise is further suppressed when the value of X / (AC frequency × 2) falls within the above range.

[0142] [Electrostatic image forming device] The electrostatic image forming apparatus 16 forms an electrostatic image on the surface of a charged photoreceptor 12. Specifically, for example, the electrostatic image forming apparatus 16 irradiates the surface of the photoreceptor 12, which has been charged by a charging member 14, with light L modulated based on the image information of the image to be formed. As a result, an electrostatic image corresponding to the image information is formed on the photoreceptor 12.

[0143] Examples of electrostatic image forming apparatus 16 include optical equipment having a light source that exposes an image-like object with light such as semiconductor laser light, LED light, or liquid crystal shutter light.

[0144] [Developing equipment] The developing device 18 is located, for example, downstream of the photoreceptor 12 in the rotational direction from the irradiation position of light L by the electrostatic image forming device 16. The developing device 18 has a storage section for containing the developer. This storage section contains an electrostatic image developer having toner. The toner is stored, for example, in a charged state within the developing device 18.

[0145] The developing apparatus 18 includes, for example, a developing member 18A and a power supply 32. The developing member 18A is a member that develops the electrostatic image formed on the surface of the photoreceptor 12 using a developer containing toner. The power supply 32 is a power supply that applies a developing voltage to the developing element 18A. The power supply 32 is electrically connected, for example, to the developing element 18A.

[0146] The developing element 18A of the developing device 18 is selected according to the type of developer, but an example is a developing roll having a developing sleeve with a magnet built in.

[0147] The developing device 18 (including the power supply 32) is electrically connected to, for example, a control device 36 provided in the image forming apparatus 10. The developing device 18 is driven and controlled by the control device 36 to apply a developing voltage to the developing member 18A. The developing member 18A, to which the developing voltage has been applied, is charged to a developing potential corresponding to the developing voltage. The developing member 18A, charged to the developing potential, then holds, for example, the developer contained in the developing device 18 on its surface. While holding the developer, the developing member 18A supplies the toner contained in the developer from inside the developing device 18 to the surface of the photoreceptor 12. On the surface of the photoreceptor 12 to which the toner has been supplied, the formed electrostatic charge image is developed as a toner image.

[0148] [Transfer device] The transfer device 31 is, for example, located downstream of the photoreceptor 12 in the rotational direction from the position where the developing member 18A is installed. The transfer device 31 includes, for example, a transfer member 20 and a power supply 30. The transfer member 20 is, for example, a member that transfers a toner image formed on the surface of the photoreceptor 12 to the recording medium 30A. The transfer member 20 is, for example, cylindrical in shape and transports the recording medium 30A between itself and the photoreceptor 12. The power supply 30 is a power source that applies a transfer voltage to the transfer member 20. The power supply 30 is electrically connected to the transfer member 20, for example.

[0149] Examples of the transfer member 20 include contact-type transfer chargers using belts, rollers, films, rubber cleaning blades, etc., and non-contact type transfer chargers that are known themselves, such as scorotron transfer chargers or corotron transfer chargers that utilize corona discharge.

[0150] The transfer device 31 (including the power supply 30) is electrically connected, for example, to a control device 36 provided in the image forming apparatus 10. The transfer device 31 is driven and controlled by the control device 36 to apply a transfer voltage to the transfer member 20. The transfer member 20, to which the transfer voltage has been applied, is charged to a transfer potential corresponding to the transfer voltage.

[0151] A transfer voltage with the opposite polarity to the toner that constitutes the toner image formed on the photoreceptor 12 is applied to the transfer member 20 from the power supply 30 of the transfer member 20. As a result, for example, in the region where the photoreceptor 12 and the transfer member 20 face each other (see transfer region 32A in Figure 3), a transfer electric field with an electric field strength that moves each toner that constitutes the toner image on the photoreceptor 12 from the photoreceptor 12 to the transfer member 20 side by electrostatic force is formed.

[0152] The recording medium 30A is housed in a housing (not shown), for example. The recording medium 30A is transported from the housing along a transport path 34 by a plurality of transport members (not shown). The recording medium 30A then reaches the transfer region 32A, which is the region where the photoreceptor 12 and the transfer member 20 face each other. In the example shown in Figure 3, it is transported in the direction of arrow B. Once the recording medium 30A reaches the transfer region 32A, the toner image on the photoreceptor 12 is transferred by the transfer electric field formed in the region, for example, when a transfer voltage is applied to the transfer member 20. That is, for example, the toner image is transferred onto the recording medium 30A by the movement of toner from the surface of the photoreceptor 12 to the recording medium 30A. The toner image on the photoreceptor 12 is then transferred onto the recording medium 30A by the transfer electric field.

[0153] [Cleaning device] The cleaning device 22 is located downstream of the transfer area 32A in the rotational direction of the photoreceptor 12. After the toner image has been transferred to the recording medium 30A, the cleaning device 22 cleans any residual toner adhering to the photoreceptor 12. In addition to residual toner, the cleaning device 22 also cleans any other adhering substances such as paper dust.

[0154] The cleaning device 22 has a cleaning blade 22A, and removes deposits from the surface of the photoreceptor 12 by bringing the tip of the cleaning blade 22A into contact with the photoreceptor 12 in a direction opposite to the rotation direction of the photoreceptor 12.

[0155] [Static eliminator] The static elimination device 24 is located, for example, downstream of the cleaning device 22 in the rotational direction of the photoreceptor 12. After transferring the toner image, the static elimination device 24 exposes the surface of the photoreceptor 12 to eliminate static electricity. Specifically, for example, the static elimination device 24 is electrically connected to a control device 36 provided in the image forming apparatus 10. The static elimination device 24 is driven and controlled by the control device 36 to expose the entire surface of the photoreceptor 12 (specifically, for example, the entire image forming area) to eliminate static electricity.

[0156] Examples of static elimination devices 24 include devices having a light source such as a tungsten lamp that emits white light or a light-emitting diode (LED) that emits red light.

[0157] [Fusing device] The fixing device 26 is provided, for example, downstream of the transfer area 32A in the transport direction of the transport path 34 of the recording medium 30A. The fixing device 26 includes a fixing member 26A and a pressurizing member 26B positioned in contact with the fixing member 26A. The fixing device 26 fixes the toner image transferred onto the recording medium 30A at the contact point between the fixing member 26A and the pressurizing member 26B. Specifically, for example, the fixing device 26 is electrically connected to a control device 36 provided in the image forming apparatus 10. The fixing device 26 is driven and controlled by the control device 36 to fix the toner image transferred onto the recording medium 30A to the recording medium 30A by heat and pressure.

[0158] Examples of the fixing device 26 include known fixing devices such as hot roller fixing devices and oven fixing devices. Specifically, for example, the fixing device 26 may be a well-known fixing device comprising a fixing roll or fixing belt as a fixing member 26A and a pressure roll or pressure belt as a pressure member 26B.

[0159] Here, the recording medium 30A onto which the toner image has been transferred is transported along the transport path 34. The recording medium 30A onto which the toner image has been transferred is transported along the transport path 34 by, for example, a transport member (not shown) to the installation position of the fixing device 26. Then, the toner image on the recording medium 30A is fixed.

[0160] The recording medium 30A, on which the image has been formed by fixing the toner image, is discharged to the outside of the image forming apparatus 10 by a plurality of transport members (not shown in the figure). The photoreceptor 12 is then discharged by the static elimination device 24 and then recharged to a charging potential by the charging device 15.

[0161] [Operation of the image forming apparatus] An example of the operation of the image forming apparatus 10 according to this embodiment will be described. Note that various operations of the image forming apparatus 10 are performed by a control program executed in the control device 36.

[0162] The image forming operation of the image forming apparatus 10 will be described. First, the surface of the photoreceptor 12 is charged by the charging device 15. The electrostatic image forming device 16 exposes the charged surface of the photoreceptor 12 based on image information. This forms an electrostatic image on the photoreceptor 12 corresponding to the image information. In the developing device 18, the electrostatic image formed on the surface of the photoreceptor 12 is developed with a developer containing toner. This forms a toner image on the surface of the photoreceptor 12. In the transfer device 31, the toner image formed on the surface of the photoreceptor 12 is transferred to the recording medium 30A. The toner image transferred to the recording medium 30A is fixed by the fuser device 26. Meanwhile, the surface of the photoreceptor 12 after the toner image has been transferred is cleaned by the cleaning blade 22A in the cleaning device 22, and then static electricity is removed by the static elimination device 24. [Examples]

[0163] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way to these examples. Unless otherwise specified, "parts" and "%" are based on mass.

[0164] <Examples 1-19, Comparative Examples 1-5> (Conductive substrate) First, a solid aluminum alloy (JIS A 3003 alloy) is extruded using an extrusion device, and then the aluminum alloy extruded by the extrusion device is drawn out using a drawing device to form an aluminum tube. Next, the ends of the obtained raw pipe were subjected to spigot processing (boring and face machining), the inner surface of the raw pipe was machined, and then the outer surface of the raw pipe was machined. In this manner, a conductive substrate consisting of a cylindrical body having stepped portions at both axial ends, as shown in Figure 4, was obtained.

[0165] The dimensions of each part of the conductive substrate are shown in Table 1. • Axial length L1 of the cylindrical body (indicated as "Length L1" in the cylindrical body column in Table 1) • Thickness T1 of the cylindrical body (indicated as "Thickness T1" in the cylindrical body column in Table 1) • Inner diameter φ1 in a cylindrical body, excluding the first and second stepped sections (indicated as "inner diameter φ1" in the cylindrical body column in Table 1)

[0166] • Length of the first step section LA1 (indicated as "Length LA1" in the column for the first step section in Table 1) • The length LA11 of the first step section where the inner diameter of the cylindrical body is enlarged in the first step, starting from the axial center of the cylindrical body (indicated as "First step length LA11" in the column for the first step section in Table 1). • The inner diameter φA1 of the first step section where the inner diameter of the cylindrical body is enlarged in the first step from the axial center side of the cylindrical body (indicated as "First step inner diameter φA1" in the column for the first step section in Table 1). • The length of the first step section where the inner diameter of the cylindrical body is enlarged in the second step from the axial center of the cylindrical body (indicated as "Second step length LA12" in the column for the first step section in Table 1). • The inner diameter φA2 of the first step section, where the inner diameter of the cylindrical body is enlarged in the second step from the axial center of the cylindrical body (indicated as "Second step inner diameter φA2" in the "First step section" column in Table 1).

[0167] • Length of the second step section LB1 (indicated as "Length LA1" in the column for the second step section in Table 1) • The length LB11 of the second step section where the inner diameter of the cylindrical body is enlarged in the first step, starting from the axial center of the cylindrical body (indicated as "First step length LB11" in the second step section column in Table 1). • The inner diameter φB1 of the second step section, where the inner diameter of the cylindrical body is enlarged in the first step from the axial center of the cylindrical body (indicated as "First step inner diameter φB1" in the second step section column in Table 1). • The length LB12 of the second step section where the inner diameter of the cylindrical body is enlarged in the second step from the axial center of the cylindrical body (indicated as "Second step length LB12" in the second step section column in Table 1). • The inner diameter φB2 of the second step section where the inner diameter of the cylindrical body is enlarged in the second step from the axial center of the cylindrical body (indicated as "Second step inner diameter φB2" in the second step section column in Table 1).

[0168] (Fabrication of the photosensitive material) Using the conductive substrates obtained from each example, electrophotographic photoreceptors were acquired. Specifically, a base layer, a charge generation layer, and a charge transport layer were formed on the conductive substrate in the following manner.

[0169] -Formation of the lower layer- 100 parts by mass of zinc oxide (product name: MZ300, manufactured by Teika Co., Ltd.) was stirred and mixed with 500 parts by mass of tetrahydrofuran, and 1.3 parts by mass of silane coupling agent (KBM503, manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred for 2 hours. Then, toluene 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.

[0170] 110 parts by mass of silane coupling-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. 60 parts by mass of alizarin-containing zinc oxide, 13.5 parts by mass of a curing agent (blocked isocyanate Sumijule 3175, manufactured by Sumitomo Bayern Urethanes), and 15 parts by mass of butyral resin (Eslec BM-1, manufactured by Sekisui Chemical Co., Ltd.) were mixed with 85 parts by mass of methyl ethyl ketone. 38 parts by mass of this mixture was then 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.

[0171] To the obtained dispersion, 0.005 parts by mass of dioctyltin dilaurate as a catalyst and 45 parts by mass of silicone resin particles (Tospar 145, manufactured by Momentive Performance Materials) were added to obtain a coating solution for forming the undercoat layer. Using this undercoating solution for forming the undercoat, it was applied to each of the above conductive substrates by immersion coating, followed by a wiping process of the inner surface of the lower end, and then dried and cured at 180°C for 30 minutes to obtain an undercoat layer with a thickness of 25 μm.

[0172] -Formation 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 charge generation layer formation solution was applied to the base layer by immersion, and dried at 100°C for 5 minutes to form a charge generation layer with a thickness of 0.20 μm.

[0173] -Formation of a charge transport layer- Next, 12 parts by mass of a charge transport material represented by the following structural formula (CT1A), 28 parts by mass of a charge transport material represented by the following structural formula (CT2A), and 60 parts by mass of bisphenol Z type polycarbonate resin (molecular weight 40,000) were dissolved in 340 parts by weight of tetrahydrofuran to obtain a coating solution for forming a charge transport layer. The obtained charge transport layer forming coating solution was applied to the charge generation layer by immersion, and a charge transport layer with a thickness of 34 μm was formed by drying at 150°C for 40 minutes.

[0174] [ka]

[0175] [ka]

[0176] Through the above process, an electrophotographic photoreceptor was obtained.

[0177] (Image forming apparatus) Flanges were attached to both ends of the conductive substrate of each obtained photoreceptor. Then, the photoreceptors with the flanges attached were mounted in an image forming apparatus (DocuPrint 3050, manufactured by Fujifilm Business Innovation Co., Ltd.). This image forming apparatus has a contact charging device that applies a current, which is a combination of direct current and alternating current, to the surface of a photoreceptor, thereby charging the surface of the photoreceptor. The DC voltage applied to the photoreceptor was set to 600V, the AC peak voltage Vpp to 50V, and the AC frequency to the values ​​shown in Table 1. In Table 1, in the value "X / (AC frequency × 2)", X represents "the ratio of the absolute value of the difference in length between the first stepped section and the second stepped section to the axial length of the cylindrical body". Also, the notation "aE+b" means "a×10 b The value is shown. The notation "aE-b" means "a × 10 -b The value is shown.

[0178] <Rating> The following evaluations were performed using the image forming apparatus in each example.

[0179] (quiet) Photoreceptors made from each substrate were placed in a "DocuPrint 3050" manufactured by Fujifilm Business Innovation Co., Ltd., and the resonant sound (high-pitched sound) was evaluated by sensory assessment when 100 consecutive halftone images with a density of 30% were printed. A sensory evaluation was conducted with 20 people, and the evaluation results were averaged from the results of all 20 people. . Furthermore, the frequency of the resonant sound was monitored using the sound-collecting microphone. The evaluation criteria were as follows: -1st harmonic- A: There are no high-pitched sounds. B: There's a high-pitched sound, but it's not noticeable at all (some people can't hear it). C: There is a high-pitched sound, but it is not bothersome (you can't hear it unless you listen carefully). D: There is a high-pitched sound, which may be bothersome to some people. E: The high-pitched sounds are too loud and everyone finds them unpleasant.

[0180] -2nd harmonic- A: There are no high-pitched sounds. B: There's a high-pitched sound, but it's not noticeable at all (some people can't hear it). C: There is a high-pitched sound, but it is not bothersome (you can't hear it unless you listen carefully). D: There is a high-pitched sound, which may be bothersome to some people. E: The high-pitched sounds are too loud and everyone finds them unpleasant.

[0181] [Table 1]

[0182] From the above results, it can be seen that the conductive substrate of this embodiment yields a photoreceptor with superior quietness compared to the conductive substrate of the comparative example. In other words, it can be seen that the conductive substrate of this embodiment suppresses noise compared to the conductive substrate of the comparative example.

[0183] This embodiment includes the following aspects. (((1))) A cylindrical body and A first stepped portion is provided on the inner circumferential surface of one axial end of the cylindrical body, wherein the inner diameter of the cylindrical body at one axial end is larger than the inner diameter of the cylindrical body at the axial center, A second stepped portion is provided on the inner circumferential surface of the other end of the cylindrical body in the axial direction, wherein the inner diameter of the cylindrical body at the other end in the axial direction is larger than the inner diameter of the cylindrical body at the central part in the axial direction. It has, A conductive substrate for an electrophotographic photoreceptor, wherein the lengths of the first stepped portion and the second stepped portion are different. (((2))) A conductive substrate for an electrophotographic photoreceptor as described in (((1))), wherein the difference in length between the first stepped portion and the second stepped portion is 13 mm or more and 79 mm or less in absolute value. (((3))) A conductive substrate for an electrophotographic photoreceptor as described in (((2))), wherein the difference in length between the first stepped portion and the second stepped portion is 13 mm or more and 53 mm or less in absolute value. (((4))) A conductive substrate for an electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is 0.05 or more and 0.31 or less. (((5))) The conductive substrate for an electrophotographic photoreceptor according to ((4)), wherein the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is 0.15 or more and 0.21 or less. (((6))) A conductive substrate for an electrophotographic photoreceptor as described in any one of items (((1))) to (((5))), The conductive substrate for the electrophotographic photoreceptor and the photosensitive layer provided thereon, An electrophotographic photoreceptor having a photoreceptor. (((7))) (((6))) comprises an electrophotographic photoreceptor as described in (((6))), A process cartridge that is attached to and detached from an image forming apparatus. (((8))) The electrophotographic photoreceptor described in (((6))) and A charging device that applies a current, which is a direct current superimposed on an alternating current, to the surface of the electrophotographic photoreceptor, thereby 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. (((9))) When X is the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body, the value of X / (the frequency of the AC × 2) is greater than 0, i.e., 1.20 × 10 -4 The image forming apparatus described below (8).

[0184] The effects of the above embodiment are as follows: According to the invention of (((1))), a conductive substrate for an electrophotographic photoreceptor is provided that yields an electrophotographic photoreceptor in which noise is suppressed compared to the case where the lengths of the first stepped portion and the second stepped portion provided on the inner circumferential surface of both ends of the cylindrical body are the same. According to the invention of (((2))), a conductive substrate for an electrophotographic photoreceptor is provided that can be obtained in which noise is suppressed compared to the case in which the difference in length between the first stepped portion and the second stepped portion is less than 13 mm or more than 79 mm in absolute value. According to the invention of (((3))), a conductive substrate for an electrophotographic photoreceptor is provided that yields an electrophotographic photoreceptor in which noise is suppressed compared to the case where the difference in length between the first stepped portion and the second stepped portion is less than 13 mm or greater than 53 mm in absolute value. According to the invention of (((4))), a conductive substrate for an electrophotographic photoreceptor is provided that yields an electrophotographic photoreceptor in which noise is suppressed compared to the case where the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is less than 0.05 or greater than 0.31. According to the invention of (((5))), a conductive substrate for an electrophotographic photoreceptor is provided that yields an electrophotographic photoreceptor in which noise is suppressed compared to the case where the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is less than 0.15 or greater than 0.21. According to the inventions of (((6))), (((7))), or (((8))), an electrophotographic photoreceptor, a process cartridge, or an image forming apparatus is provided that has a conductive substrate for an electrophotographic photoreceptor that provides an electrophotographic photoreceptor with suppressed noise compared to the case in which a conductive substrate for an electrophotographic photoreceptor is applied in which the lengths of the first stepped portion and the second stepped portion provided on the inner circumferential surface of both ends of the cylindrical body are the same. According to the invention of (((9))), the value of X / (AC frequency × 2) is 1.20 × 10 -4 An image forming apparatus is provided that has an electrophotographic photoreceptor that suppresses noise compared to cases where the noise level exceeds a certain threshold. [Explanation of Symbols]

[0185] 10 Image forming apparatus 12 Photoconductor 14 Charging member of contact type 15 Charging device 16 Electrostatic charge image forming device 18 Developing device [[ID=1十四]]20 Transfer member 22 Cleaning device 22A Cleaning blade 24 Discharging device 26 Fixing device 30A Recording medium 31 Transfer device 36 Control device 101 Undercoat layer 102 Charge generation layer 103 Charge transport layer 104 Conductive substrate 105 Photosensitive layer 106 Protective layer 107A, 107B Electro-photographic photoreceptor 110 Conductive substrate 112 Cylindrical body 1第14A Step difference part 1第14B Step difference part

Claims

1. A cylindrical body and A first stepped portion is provided on the inner circumferential surface of one axial end of the cylindrical body, wherein the inner diameter of the cylindrical body at one axial end is larger than the inner diameter of the cylindrical body at the axial center, A second stepped portion is provided on the inner circumferential surface of the other end of the cylindrical body in the axial direction, wherein the inner diameter of the cylindrical body at the other end in the axial direction is larger than the inner diameter of the cylindrical body at the central part in the axial direction. It has, A conductive substrate for an electrophotographic photoreceptor, wherein the lengths of the first stepped portion and the second stepped portion are different.

2. The conductive substrate for an electrophotographic photoreceptor according to claim 1, wherein the difference in length between the first stepped portion and the second stepped portion is 13 mm or more and 79 mm or less in absolute value.

3. The conductive substrate for an electrophotographic photoreceptor according to claim 2, wherein the difference in length between the first stepped portion and the second stepped portion is 13 mm or more and 53 mm or less in absolute value.

4. The conductive substrate for an electrophotographic photoreceptor according to claim 1, wherein the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is 0.05 or more and 0.31 or less.

5. The conductive substrate for an electrophotographic photoreceptor according to claim 4, wherein the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body is 0.15 or more and 0.21 or less.

6. A conductive substrate for an electrophotographic photoreceptor according to any one of claims 1 to 5, The conductive substrate for the electrophotographic photoreceptor and the photosensitive layer provided thereon, An electrophotographic photoreceptor having a photoreceptor.

7. The electrophotographic photoreceptor described in claim 6 comprises A process cartridge that is attached to and detached from an image forming apparatus.

8. The electrophotographic photoreceptor according to claim 6, A charging device that applies a current, which is a direct current superimposed on an alternating current, to the surface of the electrophotographic photoreceptor, thereby 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.

9. When X is the ratio of the absolute value of the difference in length between the first stepped portion and the second stepped portion to the axial length of the cylindrical body, the value of X / (the frequency of the AC × 2) is greater than 0, i.e., 1.20 × 10 -４ The image forming apparatus according to claim 8, which is as follows:

Images