Electrophotographic photoreceptor, method for manufacturing electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that forms an image with excellent granularity.SOLUTION: An electrophotographic photoreceptor comprises: a conductive substrate; an undercoat layer arranged on the conductive substrate; and a photosensitive layer arranged on the undercoat layer. In a power spectrum obtained through fast Fourier transformation of a roughness curve in an axial direction of an outer peripheral surface of the conductive substrate, an integrated value of the intensity of the range of period of 0.01 mm or more and 0.1 mm or less is 0.02 or more and 0.10 or less. The undercoat layer has a layer thickness of 10 μm or more or the undercoat layer contains metal oxide particles.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 discloses an electrophotographic photoreceptor having a photosensitive layer on a substrate, in which a coefficient of determination of a regression line of a data group having a relative cumulative frequency of 10% to 50%, in a relative cumulative frequency distribution curve obtained from a power spectrum derived by performing a fast Fourier transform on a data group showing the height of the surface roughness curve of the substrate, is 0.970 or more, the pitch at which the relative cumulative frequency is 90% is 200 μm or less, and the root-mean-square slope RΔq obtained from the roughness curve as defined in JIS B0601:2001 is 0.08 or more.

[0003] Patent Document 2 discloses a substrate for an electrophotographic photoreceptor, which is evaluated by a surface roughness evaluation method for parts for an image forming apparatus, in which a cross-sectional curve defined in JIS B0601 is determined for the surface condition of the part for an image forming apparatus, a multi-resolution analysis is performed on a position data string in the surface roughness direction at equally spaced positions on the cross-sectional curve, and the surface roughness condition is evaluated based at least on the result of the analysis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-095510 A [Patent Document 2] JP 2007-292772 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide an electrophotographic photoreceptor that has an undercoat layer with a thickness of less than 10 μm and that forms images with excellent graininess compared to an electrophotographic photoreceptor that does not contain metal oxide particles in the undercoat layer. [Means for solving the problem]

[0006] Specific means for solving the above problems include the following aspects. <1> A conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, In a power spectrum obtained by subjecting a roughness curve in an axial direction of the outer peripheral surface of the conductive substrate to a fast Fourier transform, an integrated value of intensity in a periodic range of 0.01 mm or more and 0.1 mm or less is 0.02 or more and 0.10 or less, The thickness of the undercoat layer is 10 μm or more. Electrophotographic photoreceptor. <2> The thickness of the undercoat layer is 20 μm or more. <1> The electrophotographic photoreceptor according to claim 1. <3> A conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, In a power spectrum obtained by subjecting a roughness curve in an axial direction of the outer peripheral surface of the conductive substrate to a fast Fourier transform, an integrated value of intensity in a periodic range of 0.01 mm or more and 0.1 mm or less is 0.02 or more and 0.10 or less, The undercoat layer contains metal oxide particles. Electrophotographic photoreceptor. <4> The metal oxide particles include at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, and tin oxide particles. <3> The electrophotographic photoreceptor according to claim 1. <5> The average particle size of the metal oxide particles is 10 nm or more and 80 nm or less. <3> or <4> The electrophotographic photoreceptor according to claim 1. <6> The mass ratio of the metal oxide particles in the undercoat layer is 60 mass% or more and 95 mass% or less. <3> ~ <5> 13. The electrophotographic photoreceptor according to claim 12, <7> <1> ~ <6> A method for producing the electrophotographic photoreceptor according to any one of the above items, removing all layers on the conductive substrate from a used electrophotographic photoreceptor by a water jet to regenerate the conductive substrate; forming an undercoat layer on the regenerated conductive substrate; forming a photosensitive layer on the undercoat layer; A method for manufacturing an electrophotographic photoreceptor. <7-1> <1> or <2> A method for producing the electrophotographic photoreceptor according to claim 1, The formation of the undercoat layer is to form an undercoat layer having a layer thickness of 10 μm or more. <7> 13. A method for producing an electrophotographic photoreceptor according to claim 12. <7-2> <3> ~ <6> A method for producing the electrophotographic photoreceptor according to any one of the above items, The formation of the undercoat layer is the formation of an undercoat layer containing metal oxide particles. <7> 13. A method for producing an electrophotographic photoreceptor according to claim 12. <7-3> The regeneration of the conductive substrate is to obtain a conductive substrate having a power spectrum obtained by fast Fourier transform of a roughness curve in the axial direction of the outer peripheral surface, in which an integrated value of intensity in a period range of 0.01 mm or more and 0.1 mm or less is 0.02 or more and 0.10 or less. <7> 7. The method for producing an electrophotographic photoreceptor according to any one of <7-1> and <7-2>. <8> <1> ~ <6> The electrophotographic photoreceptor according to any one of the above items is provided, A process cartridge that is detachably attached to an image forming apparatus. <9> <1> ~ <6> and an electrophotographic photoreceptor according to any one of the above items. a charging device for charging a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising: Effect of the Invention

[0007] <1> According to the present invention, there is provided an electrophotographic photoreceptor which forms images having excellent graininess as compared with an electrophotographic photoreceptor having an undercoat layer with a layer thickness of less than 10 μm and which does not contain metal oxide particles in the undercoat layer. <2> According to this, an electrophotographic photoreceptor is provided which forms images with excellent graininess, as compared with electrophotographic photoreceptors having an undercoat layer with a thickness of less than 20 μm. <3> , <4> , <5> or <6> According to the present invention, there is provided an electrophotographic photoreceptor which forms images having excellent graininess as compared with an electrophotographic photoreceptor having an undercoat layer with a layer thickness of less than 10 μm and which does not contain metal oxide particles in the undercoat layer. <7> According to the above, <7-1>, <7-2> or <7-3>, there is provided a method for producing an electrophotographic photoreceptor capable of forming an image excellent in graininess. <8> According to the present invention, a process cartridge is provided which forms images having excellent graininess, as compared with a process cartridge equipped with an electrophotographic photoreceptor in which the undercoat layer has a layer thickness of less than 10 μm and the undercoat layer does not contain metal oxide particles. <9> According to the present invention, an image forming apparatus is provided that forms images with excellent graininess, as compared with an image forming apparatus equipped with an electrophotographic photoreceptor in which the undercoat layer has a layer thickness of less than 10 μm and the undercoat layer does not contain metal oxide particles. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a partial cross-sectional view showing an example of a layer structure of the electrophotographic photoreceptor according to the present embodiment. [Diagram 2] FIG. 4 is a partial cross-sectional view showing another example of the layer structure of the electrophotographic photoreceptor according to the present embodiment. [Diagram 3] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples are merely illustrative of the embodiments, and are not intended to limit the scope of the embodiments.

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

[0011] In the present disclosure, the term "step" includes not only an independent step, but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0012] When an embodiment of the present disclosure is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the size of the members in each drawing is conceptual, and the relative relationship between the sizes of the members is not limited to this.

[0013] In the present disclosure, each component may contain multiple types of corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified. In the present disclosure, the particles corresponding to each component may include multiple types. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0014] In the present disclosure, unless otherwise specified, the alkyl group and the alkylene group include any of straight-chain, branched, and cyclic groups. In the present disclosure, a hydrogen atom in an organic group, an aromatic ring, a linking group, an alkyl group, an alkylene group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, and the like may be substituted with a halogen atom. In the present disclosure, when a compound is shown by a structural formula, the symbols (C and H) representing carbon atoms and hydrogen atoms in the hydrocarbon group and / or hydrocarbon chain may be omitted.

[0015] In the present disclosure, the term "structural unit" of a copolymer or resin is synonymous with a monomer unit.

[0016] In the present disclosure, the "axial direction" of an electrophotographic photosensitive member means the direction in which the rotation axis of the electrophotographic photosensitive member extends, and the "circumferential direction" of an electrophotographic photosensitive member means the rotation direction of the electrophotographic photosensitive member.

[0017] <Electrophotographic photoreceptor> The electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") according to this embodiment includes a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer.

[0018] FIG. 1 is a partial cross-sectional view showing an example of the layer structure of the photoreceptor according to the present embodiment. The photoreceptor 10A shown in FIG. 1 has a laminated photosensitive layer. The photoreceptor 10A has a structure in which an undercoat layer 2, a charge generation layer 3, and a charge transport layer 4 are laminated in this order on a conductive substrate 1, and the charge generation layer 3 and the charge transport layer 4 constitute a photosensitive layer 5 (so-called a function-separated photosensitive layer). The photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3. The photoreceptor 10A may have a protective layer (not shown) on the charge transport layer 4.

[0019] Fig. 2 is a partial cross-sectional view showing another example of the layer structure of the photoreceptor according to the present embodiment. The photoreceptor 10B shown in Fig. 2 has a single-layer type photosensitive layer. The photoreceptor 10B has a structure in which an undercoat layer 2 and a photosensitive layer 5 are laminated in this order on a conductive substrate 1. The photoreceptor 10B may have an intermediate layer (not shown) between the undercoat layer 2 and the photosensitive layer 5. The photoreceptor 10B may have a protective layer (not shown) on the photosensitive layer 5.

[0020] The conductive substrate provided in the photoreceptor according to this embodiment has a power spectrum obtained by fast Fourier transform of the axial roughness curve of the outer peripheral surface of the conductive substrate, in which the integrated value of intensity in a range of a period of 0.01 mm or more and 0.1 mm or less is 0.02 or more and 0.10 or less. In this disclosure, the integrated value of intensity in a period range of 0.01 mm or more and 0.1 mm or less in a power spectrum obtained by fast Fourier transform of the axial roughness curve of the outer peripheral surface of the conductive substrate is referred to as "integrated value S."

[0021] The integrated value S is calculated according to the following (1) to (4). (1) All layers are removed from the photoreceptor to expose the outer peripheral surface of the conductive substrate. Each layer of the photoreceptor is removed by immersing the photoreceptor in an organic solvent that dissolves the binder resin of each layer but does not corrode the conductive substrate. (2) Obtain the axial roughness curve of the outer peripheral surface of the conductive substrate. The roughness curve is the roughness curve specified in JIS B0601:2013. The roughness of the outer peripheral surface of the conductive substrate is measured using a contact surface roughness measuring instrument (Surfcom 1400A, Tokyo Seimitsu Co., Ltd.) in an environment with a temperature of 23°C and a relative humidity of 55%. The conductive substrate is scanned in the axial direction at a scanning speed of 0.3 mm / sec, a measurement length of 2.5 mm, and a cutoff value of 0.8 mm. The measuring probe is cone-shaped with an apex angle of 90°, a tip curvature radius of 5 μm, and the tip material is diamond. Three measurement points are measured: the center in the axial direction and both ends of the image formation area. A roughness curve is calculated from the measured values ​​at the three points. (3) The roughness curve is subjected to a fast Fourier transform to derive the power spectrum. Microsoft Excel is used as the analysis software. 4096 height direction parameters are extracted from the roughness curve at a pitch of 0.6 μm. The 4096 height data points are converted so that the average of the 4096 points is 0. The 4096 parameter values ​​are fast Fourier transformed to derive a power spectrum with the horizontal axis being the period (mm) and the vertical axis being the intensity. (4) The intensity in the power spectrum in the period range of 0.01 mm or more and 0.1 mm or less is integrated to obtain the integrated value S. The integrated value S is the integrated value of the power spectrum value in the period range of 0.01 mm or more and 0.1 mm or less.

[0022] This embodiment provides a way to regenerate a conductive substrate from a used photoreceptor and reuse the regenerated conductive substrate. As a result of the study by the inventors of the present disclosure, it was found that fine irregularities are formed on the surface of the conductive substrate in the process of removing all layers from a used photoreceptor, and that the fine irregularities on the surface of the conductive substrate cause deterioration in the graininess of the image (for example, a halftone image or a gradation image has a rough texture). It was speculated that this is because the irregularities on the surface of the conductive substrate are reflected on the outer peripheral surface of the photoreceptor, causing the irregularities to appear on the outer peripheral surface of the photoreceptor. As a result of further investigation, the inventors found that the integrated value S in the power spectrum obtained by fast Fourier transform of the roughness curve of the conductive substrate is an index of the surface properties of the conductive substrate that leads to deterioration of the graininess of the image, and that if the integrated value S is 0.02 or more, the graininess of the image deteriorates. The integrated value S is preferably 0.10 or less, and the smaller the value, the more preferable.

[0023] This embodiment provides a photoconductor according to a first embodiment and a photoconductor according to a second embodiment as a means for solving a problem (deterioration of image graininess) caused by a conductive substrate having an integrated value S of 0.02 or more and 0.10 or less. In this disclosure, when matters common to the first embodiment and the second embodiment are described, both forms are collectively referred to as this embodiment.

[0024] The photoreceptor according to the first embodiment comprises a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, and has an integrated value S of 0.02 or more and 0.10 or less, and a thickness of the undercoat layer of 10 μm or more. In the first embodiment, the thickness of the undercoat layer is 10 μm or more, so that the unevenness of the surface of the conductive substrate is unlikely to be reflected on the outer peripheral surface of the photoreceptor, and an image with excellent graininess is formed. From this viewpoint, the thickness of the undercoat layer is preferably 15 μm or more, more preferably 18 μm or more, and even more preferably 20 μm or more. In the first embodiment, the thickness of the undercoat layer is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less, from the viewpoint of suppressing residual charges.

[0025] The thickness of the undercoat layer is the arithmetic average of values ​​measured by an electromagnetic film thickness meter, and the measurement points are four points at 90° intervals in the circumferential direction from the center in the axial direction of the photoreceptor.

[0026] In the first embodiment, the undercoat layer may or may not contain a filler. When the undercoat layer in the first embodiment contains a filler, the filler is preferably an inorganic particle, more preferably a metal oxide particle, and further preferably at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, and tin oxide particles. The inorganic particles may be surface-treated with a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, or the like. An electron-accepting compound may be attached to the surface of the inorganic particles. Examples of the surface treatment agent and the electron-accepting compound are described below.

[0027] The photoreceptor according to the second embodiment comprises a conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, and has an integrated value S of 0.02 or more and 0.10 or less, and the undercoat layer contains metal oxide particles. In the second embodiment, the undercoat layer contains metal oxide particles, so that the irregularities on the surface of the conductive substrate are unlikely to be reflected on the outer peripheral surface of the photoreceptor, and an image with excellent graininess is formed.

[0028] Examples of the metal oxide particles include zinc oxide particles, titanium oxide particles, tin oxide particles, zirconium oxide particles, etc. The metal oxide particles contained in the undercoat layer may be of one type or of two or more types. From the viewpoint of the electrical properties of the photoreceptor, the metal oxide particles are preferably at least one type selected from the group consisting of zinc oxide particles, titanium oxide particles, and tin oxide particles, and zinc oxide particles are more preferable.

[0029] The metal oxide particles may be surface-treated with a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, etc. Preferred forms of the surface treatment agent are as described below. An electron-accepting compound may be attached to the surface of the metal oxide particles. Preferred forms of the electron-accepting compound and a method for attaching the electron-accepting compound to the surface of the metal oxide particles will be described later.

[0030] The average particle size of the metal oxide particles contained in the undercoat layer is preferably 5 nm or more and 100 nm or less, more preferably 10 nm or more and 80 nm or less, and even more preferably 20 nm or more and 50 nm or less, from the viewpoint of suppressing the reflection of the unevenness of the surface of the conductive substrate on the outer peripheral surface of the photoreceptor and forming an image with excellent graininess.

[0031] The average particle size of the metal oxide particles is determined by the following measurement method. The metal oxide particles are extracted from the undercoat layer. Methods for extracting the metal oxide particles from the undercoat layer include, for example, a method in which the undercoat layer peeled off from the photoreceptor is immersed in an organic solvent that dissolves the binder resin to dissolve the binder resin with the organic solvent and extract the metal oxide particles, and a method in which the undercoat layer peeled off from the photoreceptor is heated to about 800°C to eliminate the binder resin and extract the metal oxide particles. Metal oxide particles are observed under a scanning electron microscope, the circular equivalent diameters of 100 randomly selected primary particles are determined, and the arithmetic mean of the circular equivalent diameters is taken as the average particle size.

[0032] The mass proportion of the metal oxide particles in the undercoat layer is preferably 60% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and even more preferably 80% by mass or more and 90% by mass or less, from the viewpoint of suppressing the reflection of the unevenness of the surface of the conductive substrate on the outer peripheral surface of the photoreceptor and forming an image with excellent graininess.

[0033] In the second embodiment, the thickness of the undercoat layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, still more preferably 18 μm or more, and even more preferably 20 μm or more, from the viewpoint of obtaining better image graininess. In the second embodiment, the thickness of the undercoat layer is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 30 μm or less, from the viewpoint of suppressing residual charges.

[0034] Each layer of the photoreceptor will now be described in detail.

[0035] [Conductive substrate] Examples of conductive substrates include metal plates, metal rolls, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Examples of conductive substrates include paper, resin films, belts, etc. 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" means that the volume resistivity is less than 1×1013 Ωcm.

[0036] An example of the conductive substrate is a conductive substrate regenerated by removing all layers on the conductive substrate from a used photoreceptor. An example of a method for removing all or each layer on the conductive substrate is a water jet method (described in detail later). The used photoreceptor has the conductive substrate used in the manufacture of the photoreceptor, and this conductive substrate may be any of the known conductive substrates, which may be conductive substrates that have been subjected to wet honing, centerless grinding, anodizing, acid treatment, boehmite treatment, or the like.

[0037] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0038] For example, inorganic particles have a powder resistance (volume resistivity) of 1×10 2 Ωcm or more 1×10 11 Examples of such particles include inorganic particles with a particle size of Ωcm or less. Among these, examples of inorganic particles having the above-mentioned resistance value include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, and zinc oxide particles are particularly preferred.

[0039] The specific surface area of ​​inorganic particles by the BET method is, for example, 10 m 2 / g or higher is preferable. The volume average particle size of the inorganic particles is, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

[0040] When the undercoat layer contains inorganic particles, the content of the inorganic particles is preferably 60% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 95% by mass or less, and even more preferably 80% by mass or more and 90% by mass or less, based on the entire undercoat layer.

[0041] The inorganic particles may be surface-treated. Two or more types of inorganic particles having different surface treatments or different particle sizes may be used in combination.

[0042] Examples of the surface treatment agent include a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, etc. In particular, a silane coupling agent is preferable, and a silane coupling agent having an amino group is more preferable.

[0043] 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.

[0044] Silane coupling agents may be used in combination of two or more kinds. 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-methacryloxypropyl-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.

[0045] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

[0046] The amount of the surface treatment agent to be used is preferably, for example, 0.5% by mass or more and 10% by mass or less based on the inorganic particles.

[0047] Here, it is preferable that the undercoat layer contains an electron accepting compound (acceptor compound) together with the inorganic particles, from the viewpoints of improving the long-term stability of electrical properties and carrier blocking properties.

[0048] Examples of the electron-accepting compound include electron-transporting substances such as 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, the electron-accepting compound is preferably a compound having an anthraquinone structure. Examples of the compound having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds, and more specifically, anthraquinone, alizarin, quinizarin, anthrarufin, and purpurin.

[0049] The electron accepting compound may be contained in the undercoat layer in a dispersed state together with the inorganic particles, or may be contained in a state of being attached to the surfaces of the inorganic particles.

[0050] The method for attaching the electron accepting compound to the surface of the inorganic particles may be, for example, a dry method or a wet method.

[0051] The dry method is, for example, a method in which an electron-accepting compound is attached to the surface of inorganic particles by dropping an electron-accepting compound directly or dissolved in an organic solvent or spraying it together with dry air or nitrogen gas while stirring inorganic particles with a mixer or the like that exerts a large shearing force. The dropping or spraying of the electron-accepting compound is preferably performed at a temperature below the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be performed at 100° C. or higher. The temperature and time of baking are not particularly limited as long as electrophotographic properties can be obtained.

[0052] The wet method is a method in which, for example, an electron-accepting compound is added while dispersing inorganic particles in a solvent by stirring, ultrasonic waves, a sand mill, an attritor, a ball mill, etc., and the inorganic particles are stirred or dispersed, and then the solvent is removed to attach the electron-accepting compound to the surface of the inorganic particles. The solvent is removed, for example, by filtration or distillation. After the solvent is removed, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as electrophotographic properties are obtained. In the wet method, moisture contained in the inorganic particles may be removed before adding the electron-accepting compound, and examples of such methods include a method of removing the moisture while stirring and heating in a solvent, and a method of removing the moisture by azeotropy with the solvent.

[0053] The attachment of the electron accepting compound may be carried out before or after the inorganic particles are subjected to a surface treatment with a surface treatment agent, or the attachment of the electron accepting compound and the surface treatment with the surface treatment agent may be carried out simultaneously.

[0054] The content of the electron accepting compound is, for example, from 0.01% by mass to 20% by mass, and preferably from 0.01% by mass to 10% by mass, based on the inorganic particles.

[0055] Examples of the binder resin used in the undercoat layer include known materials such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; and silane coupling agents. Examples of the binder resin used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline, etc.), and the like.

[0056] Among these, the binder resin used in the undercoat layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and in particular, a resin obtained by reacting at least one resin selected from the group consisting of thermosetting resins such as urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins, with a curing agent is preferred. When two or more of these binder resins are used in combination, the mixing ratio is set as necessary.

[0057] The undercoat layer may contain various additives for improving electrical properties, environmental stability, and image quality. Examples of the additives include known materials such as polycyclic condensation and azo-based electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, silane coupling agents, etc. As described above, silane coupling agents are used for surface treatment of inorganic particles, and may also be added to the undercoat layer as an additive.

[0058] Examples of silane coupling agents as additives include vinyltrimethoxysilane, 3-methacryloxypropyl-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, 3-chloropropyltrimethoxysilane, and the like.

[0059] Examples of the zirconium chelate compound include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate 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.

[0060] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-n-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.

[0061] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0062] These additives may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0063] The undercoat layer preferably has a Vickers hardness of 35 or more. The surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to between 1 / (4n) (n is the refractive index of the upper layer) and 1 / 2 of the wavelength λ of the exposure laser used in order to suppress moire images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of the resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. The surface of the undercoat layer may be polished to adjust the surface roughness. Examples of the polishing method include buffing, sandblasting, wet honing, grinding, and the like.

[0064] The formation of the undercoat layer is not particularly limited, and a known formation method can be used. For example, the undercoat layer can be formed by forming a coating film of a coating solution for forming the undercoat layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary.

[0065] Examples of the solvent for preparing the coating liquid for forming the undercoat layer 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 ordinary 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.

[0066] Examples of the method for dispersing the inorganic particles when preparing the coating liquid for forming the undercoat layer include known methods such as those using a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0067] Examples of the method for applying the coating liquid for forming the undercoat layer onto the conductive substrate include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0068] The thickness of the undercoat layer is preferably within the range described above in each of the first and second embodiments.

[0069] [Middle layer] The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include polymer compounds such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, and melamine resins. The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used in the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in the intermediate layer may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0070] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0071] The formation of the intermediate layer is not particularly limited, and a known formation method can be used. For example, the intermediate layer can be formed by forming a coating film of a coating solution for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary. The intermediate layer can be formed by any of the usual coating methods, such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating and curtain coating.

[0072] The thickness of the intermediate layer is preferably set in the range of 0.1 μm to 3 μm. The intermediate layer may be used as an undercoat layer.

[0073] [Charge generation layer] The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. The charge generation layer may also be a vapor deposition layer of the charge generation material. The vapor deposition layer of the charge generation material is suitable for use with a non-coherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array.

[0074] Examples of the charge generating material include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0075] 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, or titanyl phthalocyanine.

[0076] On the other hand, in order to accommodate laser exposure in the near ultraviolet region, preferred charge generating materials include condensed aromatic pigments such as dibromoanthanthrone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and bisazo pigments.

[0077] The above charge generating materials may be used when using incoherent light sources such as LEDs and organic EL image arrays that emit light at a central wavelength of 450 nm to 780 nm, but from the viewpoint of resolution, when using a thin photosensitive layer of 20 μm or less, the electric field strength in the photosensitive layer becomes high, and a decrease in charging due to charge injection from the substrate, so-called black spots, is likely to occur as an image defect. This becomes more noticeable when using charge generating materials that are p-type semiconductors such as trigonal selenium and phthalocyanine pigments and are prone to generating dark current.

[0078] In contrast, when n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge generating materials, dark current is unlikely to occur, and image defects called black spots can be suppressed even in thin films. The n-type is determined by the polarity of the flowing photocurrent using the commonly used time-of-flight method, and those that are more likely to pass electrons as carriers than holes are considered to be n-type.

[0079] The binder resin used in the charge generating layer may be selected from a wide range of insulating resins, and may also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, polysilane, and the like. Examples of the binder resin include polyvinyl butyral resin, polyarylate resin (polycondensation product of bisphenols and aromatic dicarboxylic acid, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinylpyrrolidone resin, etc. Here, "insulating" means a material having a volume resistivity of 10 13These binder resins are used alone or in combination of two or more.

[0080] The compounding ratio of the charge generating material to the binder resin is preferably within a range of 10:1 to 1:10 by mass.

[0081] The charge generating layer may contain other known additives.

[0082] The formation of the charge generation layer is not particularly limited, and a known formation method is used, for example, by forming a coating film of a coating solution for forming the charge generation layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary. The formation of the charge generation layer may be performed by vapor deposition of the charge generation material. The formation of the charge generation layer by vapor deposition is particularly suitable when a condensed ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0083] Examples of the solvent for preparing the coating liquid for forming the charge generating 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, toluene, etc. These solvents may be used alone or in combination of two or more.

[0084] As a method for dispersing particles (e.g., charge generating material) in the coating liquid for forming a charge generating layer, for example, a media dispersing machine such as a ball mill, a vibration ball mill, an attritor, a sand mill, or a horizontal sand mill, or a media-less dispersing machine such as an agitator, an ultrasonic dispersing machine, a roll mill, or a high-pressure homogenizer, may be used. Examples of high-pressure homogenizers include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion is dispersed by penetrating a fine flow path under high pressure. During dispersion, it is effective to set the average particle size of the charge generating material in the coating liquid for forming a charge generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0085] Examples of a method for applying the coating liquid for forming the charge generating layer onto the undercoat layer (or onto the intermediate layer) include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0086] The thickness of the charge generating layer is preferably set within the range of 0.1 μm or more and 5.0 μm or less, and more preferably 0.2 μm or more and 2.0 μm or less.

[0087] [Charge transport layer] The charge transport layer is, for example, a layer containing a charge transport material and a binder resin, and may be a layer containing a polymer charge transport material.

[0088] Examples of the charge transport material include electron transporting compounds such as quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds. Examples of the charge transport material include hole transporting 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, but are not limited to these.

[0089] As the charge transport material, from the viewpoint of charge mobility, 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.

[0090] [ka]

[0091] In structural formula (a-1), Ar T1 , Ar T2 , and ArT3 each independently represents a substituted or unsubstituted aryl group, -C6H4-C(R T4 )=C(R T5 )(R T6 ), or -CH-CH=CH-CH=C(R T7 )(R T8 ) is shown. 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. Examples of the substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0092] [ka]

[0093] In structural formula (a-2), R T91 and R T92 R each 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 independently represents a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, an amino group substituted with an alkyl group having from 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ) and R T12 , R T13 , R T14 , R T15 and R T16each 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 of 0 or more and 2 or less. Examples of the substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0094] Among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), in particular, "-C6H4-CH=CH-CH=C(R T7 )(R T8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 ) is preferable from the viewpoint of charge mobility.

[0095] As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane are used. In particular, polyester polymer charge transport materials are particularly preferred. The polymer charge transport material may be used alone or in combination with a binder resin.

[0096] Examples of the binder resin 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, polysilane, etc. Among these, polycarbonate resin or polyarylate resin is suitable as the binder resin. These binder resins are used alone or in combination of two or more. The compounding ratio of the charge transport material to the binder resin is preferably from 10:1 to 1:5 by mass.

[0097] The charge transport layer may contain other known additives.

[0098] The formation of the charge transport layer is not particularly limited, and a known formation method can be used. For example, the charge transport layer can be formed by forming a coating film of a coating liquid for forming the charge transport layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0099] Examples of solvents for preparing the coating liquid for forming the charge transport layer include ordinary organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene, ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride, and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents may be used alone or in combination of two or more.

[0100] Examples of a coating method for coating the coating liquid for forming the charge transport layer on the charge generating layer include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating and curtain coating.

[0101] The thickness of the charge transport layer is set, for example, preferably in the range of 5 μm or more and 50 μm or less, and more preferably in the range of 10 μm or more and 30 μm or less.

[0102] [Protective layer] A protective layer is provided on the photosensitive layer as necessary for the purpose of, for example, preventing chemical changes in the photosensitive layer when the photosensitive layer is charged and further improving the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a layer composed of a cured film (crosslinked film) as the protective layer. Examples of such a layer include the following layers 1) and 2).

[0103] 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 in the same molecule (i.e., a layer containing a polymer or crosslinked product of the reactive group-containing charge transport material). 2) A layer composed of a cured film of a composition containing a non-reactive charge transport material and a reactive group-containing non-charge transport material that does not have a charge transport skeleton and has a reactive group (i.e., a layer containing a non-reactive charge transport material and a polymer or crosslinked body of the reactive group-containing non-charge transport material).

[0104] The reactive group of the reactive group-containing charge transport material may be a chain polymerizable group, an epoxy group, -OH, -OR (wherein R represents an alkyl group), -NH2, -SH, -COOH, or -SiR. Q1 3-Qn (OR Q2 ) Qn [However, R Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group; R Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group; Qn represents an integer of 1 to 3.

[0105] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, and is, for example, a functional group having a group containing at least a carbon double bond.Specific examples include a group containing at least one selected from a vinyl group, a vinyl ether group, a vinyl thioether group, a styryl group (vinyl phenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof.Among them, the chain polymerizable group is preferably a group containing at least one selected from a vinyl group, a styryl group (vinyl phenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof, because of its excellent reactivity.

[0106] 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, and examples thereof include a skeleton derived from a nitrogen-containing hole transporting compound such as a triarylamine compound, a benzidine compound, a hydrazone compound, etc., and a structure conjugated with a nitrogen atom. Among these, a triarylamine skeleton is preferred.

[0107] The reactive group-containing charge transport material having a reactive group and a charge transporting skeleton, the non-reactive charge transport material, and the reactive group-containing non-charge transport material may be selected from known materials.

[0108] The protective layer may contain other known additives.

[0109] The formation of the protective layer is not particularly limited, and a known formation method can be used. For example, the protective layer can be formed by forming a coating film of a coating liquid for forming a protective layer in which the above components are added to a solvent, drying the coating film, and, if necessary, subjecting it to a curing treatment such as heating.

[0110] Examples of solvents for preparing a coating solution 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 may be used alone or in combination of two or more. The coating liquid for forming the protective layer may be a solvent-free coating liquid.

[0111] Examples of a method for applying the protective layer-forming coating liquid onto a photosensitive layer (e.g., a charge transport layer) include conventional methods such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating.

[0112] The thickness of the protective layer is set, for example, preferably in the range of 1 μm or more and 20 μm or less, and more preferably in the range of 2 μm or more and 10 μm or less.

[0113] [Single-layer photosensitive layer] The single-layer type photosensitive layer (charge generation / charge transport layer) is, for example, a layer containing a charge generation material, a charge transport material, and, if necessary, a binder resin and other known additives. These materials are the same as those described for the charge generation layer and the charge transport layer.

[0114] In the single-layer photosensitive layer, the content of the charge generating material is preferably 0.1% by mass to 10% by mass, more preferably 0.8% by mass to 5% by mass, based on the total solid content. In the single-layer photosensitive layer, the content of the charge transport material is preferably 5% by mass to 50% by mass, based on the total solid content.

[0115] The method for forming the single-layer type photosensitive layer is the same as the method for forming the charge generating layer and the charge transport layer.

[0116] The thickness of the single-layer photosensitive layer is, for example, from 5 μm to 50 μm, and preferably from 10 μm to 40 μm.

[0117] <Method of Manufacturing Electrophotographic Photoreceptor> An example of a method for producing a photoconductor according to this embodiment is as follows: Removing all layers on the conductive substrate from the used photoreceptor to regenerate the conductive substrate (regenerating the conductive substrate); forming an undercoat layer on the regenerated conductive substrate (undercoat layer forming step); forming a photosensitive layer on the undercoat layer (photosensitive layer forming step). The method for producing a photoreceptor according to this embodiment may further include forming a protective layer on the photosensitive layer (protective layer forming step).

[0118] In one example of the method for producing the photoreceptor according to the present embodiment, a regenerated conductive substrate is used, in which the integrated value S is 0.02 or more and 0.10 or less.

[0119] [Conductive substrate recycling process] The regeneration step of the conductive substrate may involve removing all layers on the conductive substrate at once, or may involve removing each layer in sequence. Although the method for removing all or each layer on the conductive substrate is not limited, a water jet method in which high-speed water is collided with the photoreceptor to peel off all or each layer is preferred. Water jets are less likely to chemically modify or contaminate the surface of the conductive substrate.

[0120] The conductive substrate may have fine irregularities on its surface after all or each layer on the conductive substrate is peeled off by a water jet and regenerated. In one embodiment of the conductive substrate regenerated by the water jet method, the integrated value S is 0.02 or more and 0.10 or less.

[0121] The water pressure, water volume, and water temperature of the water jet are not limited and may be set according to the material of the conductive substrate, the composition and thickness of each layer to be peeled off, and the time and power required for peeling. The water pressure, water volume, and water temperature of the water jet are set so that the integrated value S of the regenerated conductive substrate is 0.10 or less. The water used for the water jet may contain a surfactant.

[0122] The water jet may be combined with other peeling means. For example, after a used photoreceptor is immersed in a solvent or after a used photoreceptor is heated, all or each of the softened layers may be peeled off by a water jet. Alternatively, for example, a part of a layer may be removed by air blasting, and then a water jet may be used for finishing.

[0123] The materials of the regenerated conductive substrate include, for example, metals such as aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.; alloys such as stainless steel; conductive polymers, conductive compounds such as indium oxide, etc.; paper or resin sheet coated, vapor-deposited, or laminated with a metal or alloy; etc. "Conductive" means a material with a volume resistivity of 1×10 13 This means that the resistance is less than Ωcm. The regenerated conductive substrate may be in the form of, for example, a roll, a belt, a drum, a sheet, a plate, or the like.

[0124] The regenerated conductive substrate may be subjected to an acid treatment or a boehmite treatment to form a coating.

[0125] [Undercoat layer formation process] The formation of the undercoat layer includes, for example, preparing a coating liquid for forming an undercoat layer, applying the coating liquid for forming an undercoat layer onto a conductive substrate to form a coating film, drying the coating film, and, if necessary, heating the coating film. The embodiments of each step are as described above for the undercoat layer.

[0126] When the photoreceptor according to the first embodiment is manufactured, an undercoat layer having a thickness of 10 μm or more is formed in the undercoat layer forming step. The preferred range of the thickness of the undercoat layer is as described above for the first embodiment.

[0127] When the photoconductor according to the second embodiment is manufactured, an undercoat layer containing metal oxide particles is formed in the undercoat layer forming step. The embodiment of the metal oxide particles is as described above for the second embodiment.

[0128] The embodiment of the photosensitive layer forming step is the same as that described above for the charge generating layer, the charge transport layer and the single-layer type photosensitive layer. The embodiment of the protective layer forming step is as described above for the protective layer.

[0129] <Image forming apparatus, process cartridge> The image forming apparatus according to the present embodiment includes an electrophotographic photoreceptor, a charging device that charges the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, and a transfer device that transfers the toner image to the surface of a recording medium. The electrophotographic photoreceptor according to the present embodiment is applied as the electrophotographic photoreceptor.

[0130] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as an apparatus including a fixing device that fixes a toner image transferred onto the surface of a recording medium; an apparatus of a direct transfer type that directly transfers a toner image formed on the surface of an electrophotographic photosensitive member onto a recording medium; an apparatus of an intermediate transfer type that primarily transfers a toner image formed on the surface of an electrophotographic photosensitive member onto the surface of an intermediate transfer member, and then secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium; an apparatus including a cleaning device that cleans the surface of an electrophotographic photosensitive member before charging after the transfer of a toner image; an apparatus including a static elimination device that irradiates the surface of an electrophotographic photosensitive member with static elimination light to eliminate static electricity before charging after the transfer of a toner image; and an apparatus including an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

[0131] In the case of an intermediate transfer type device, the transfer device is configured to have, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer device which primarily transfers the toner image formed on the surface of an electrophotographic photosensitive body onto the surface of the intermediate transfer body, and a secondary transfer device which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

[0132] The image forming apparatus according to the present embodiment may be either a dry development type image forming apparatus or a wet development type image forming apparatus (a development type using a liquid developer).

[0133] In the image forming apparatus according to the present embodiment, for example, a portion including an electrophotographic photosensitive member may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge including the electrophotographic photosensitive member according to the present embodiment is preferably used. The process cartridge may include, in addition to the electrophotographic photosensitive member, at least one selected from the group consisting of a charging device, an electrostatic latent image forming device, a developing device, and a transfer device.

[0134] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. Principal parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0135] FIG. 3 is a schematic diagram showing an example of an image forming apparatus according to the present embodiment. As shown in FIG. 3, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 via the intermediate transfer body 50, and the intermediate transfer body 50 is disposed with a part of it in contact with the electrophotographic photoreceptor 7. Although not shown, the image forming apparatus 100 also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown) correspond to an example of a transfer device.

[0136] 3 supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging device), a developing device 11 (an example of a developing device), and a cleaning device 13 (an example of a cleaning device) integrally within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is disposed so as to come into contact with the surface of the electrophotographic photoreceptor 7. The cleaning member may not be in the form of the cleaning blade 131, but may be a conductive or insulating fibrous member, which may be used alone or in combination with the cleaning blade 131.

[0137] FIG. 3 shows an example of an image forming apparatus including a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of the electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists in cleaning, which are arranged as needed.

[0138] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0139] -Charging device- As the charging device 8, for example, a contact type charger using a conductive or semiconductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. Also, a non-contact type roller charger, a scorotron charger or corotron charger that utilizes corona discharge, or other chargers known per se, can be used.

[0140] -Exposure equipment- The exposure device 9 may be, for example, an optical device that exposes the surface of the electrophotographic photoreceptor 7 with light such as semiconductor laser light, LED light, or liquid crystal shutter light in a predetermined image. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photoreceptor. The wavelength of the semiconductor laser is mainly near infrared light having an oscillation wavelength of about 780 nm. However, it is not limited to this wavelength, and a laser having an oscillation wavelength of 600 nm or a blue laser having an oscillation wavelength of 400 nm to 450 nm may also be used. In addition, a surface-emitting laser light source capable of outputting multiple beams is also effective for forming a color image.

[0141] -Developing device- The developing device 11 may be, for example, a general developing device that develops by contacting or non-contacting a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected according to the purpose. For example, it may be a known developing device that has a function of attaching a one-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, roller, or the like. Among them, it is preferable to use a developing roller that holds a developer on its surface.

[0142] The developer used in the developing device 11 may be a one-component developer containing only toner, or may be a two-component developer containing toner and a carrier. The developer may be magnetic or non-magnetic. Known developers are used.

[0143] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131. In addition to the cleaning blade type, a fur brush cleaning type or a simultaneous development and cleaning type may also be adopted.

[0144] -Transfer device- Examples of the transfer device 40 include known transfer chargers such as a contact type transfer charger using a belt, roller, film, rubber blade, etc., and a scorotron transfer charger or corotron transfer charger that utilizes corona discharge.

[0145] -Intermediate transfer body- A belt-like intermediate transfer belt containing semiconductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. is used as the intermediate transfer body 50. The intermediate transfer body may be in the form of a drum other than a belt.

[0146] FIG. 4 is a schematic diagram showing another example of the image forming apparatus according to the present embodiment. 4 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one electrophotographic photosensitive body is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem type. EXAMPLES

[0147] Hereinafter, the embodiments of the present invention will be described in detail with reference to examples, but the embodiments of the present invention are not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are by mass. In the following description, unless otherwise specified, synthesis, production, processing, measurement, etc. were carried out at room temperature (25°C ± 3°C).

[0148] <Regeneration of conductive substrates> A used photoconductor was prepared. This photoconductor was equipped with the aluminum cylindrical tube used in the manufacture of the photoconductor. The integrated value S of the new aluminum cylindrical tube used in the manufacture of the photoconductor was less than 0.02.

[0149] All layers were removed from a used photoreceptor using a water jet to regenerate the conductive substrate. By changing the water pressure of the water jet, conductive substrates (1) to (3) with different integrated values ​​S were obtained. The integrated values ​​S of the conductive substrates (1) to (3) are shown in Table 1. The conductive substrates (1) to (3) are cylindrical aluminum tubes having an outer diameter of 30 mm, a length of 250 mm, and a wall thickness of 1 mm.

[0150] First Embodiment <Example 1> [Formation of undercoat layer] 20 parts of blocked isocyanate (trade name: Sumidur BL3175, manufactured by Sumitomo Bayern Urethane Co., Ltd., solid content 75%) and 7.5 parts of butyral resin (polyvinyl butyral, S-LEC BL-1, manufactured by Sekisui Chemical Co., Ltd.) were dissolved in 150 parts of methyl ethyl ketone. 34 parts of a mixture (mass ratio 50:50) of perinone compound (1-1) and perinone compound (2-1) were mixed with this solution, and dispersed for 10 hours in a sand mill using glass beads with a diameter of 1 mm to obtain a dispersion. 0.005 parts of bismuth carboxylate (K-KAT XK-640, manufactured by King Industry Co., Ltd.) were added to this dispersion to obtain a coating liquid for forming an undercoat layer. This coating liquid was applied to the outer peripheral surface of the conductive substrate (1) by immersion coating, and dried and cured at 160°C for 60 minutes to form an undercoat layer. The layer thickness of the undercoat layer is as shown in Table 1.

[0151] [ka]

[0152] [Formation of charge generation layer] A mixture of 15 parts of hydroxygallium phthalocyanine (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in the X-ray diffraction spectrum using CuKα characteristic X-rays) as a charge generating material, 10 parts of vinyl chloride-vinyl acetate copolymer resin (product name: VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using glass beads with a diameter of 1 mm for 4 hours. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion and stirred to obtain a coating liquid for forming a charge generating layer. This coating liquid was dip-coated on the undercoat layer and dried at room temperature to form a charge generating layer with a layer thickness of 0.25 μm.

[0153] [Formation of charge transport layer] 60 parts of polycarbonate resin (1) (viscosity average molecular weight 40000, the numerical values ​​in the following structural formula are molar ratios) and 40 parts of CTM-1, a charge transport material, were dissolved in a mixed solvent of 270 parts of tetrahydrofuran and 30 parts of toluene to obtain a coating liquid for forming a charge transport layer. This coating liquid was dip-coated on the charge generation layer, and the coating film was dried at a temperature of 150°C for 30 minutes to form a charge transport layer with a thickness of 20 μm.

[0154] [ka]

[0155] <Examples 2 to 9> Each photoreceptor was prepared in the same manner as in Example 1, except that the type of conductive substrate and the thickness of the undercoat layer were changed to those shown in Table 1.

[0156] <Comparative Examples 1 to 3> Each photoreceptor was prepared in the same manner as in Example 1, except that the type of conductive substrate and the thickness of the undercoat layer were changed to those shown in Table 1.

[0157] Second Embodiment <Example 10> A photoreceptor was prepared in the same manner as in Example 1, except that the formation of the undercoat layer was changed as follows.

[0158] [Formation of undercoat layer] 100 parts of zinc oxide (average particle size 70 nm, manufactured by Teika Co., Ltd.) was mixed with 500 parts of toluene by stirring, and 1.3 parts of a silane coupling agent (product name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) was added and stirred for 2 hours. Next, the toluene was distilled off under reduced pressure, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent.

[0159] 110 parts of the surface-treated zinc oxide was mixed with 500 parts of tetrahydrofuran by stirring, and a solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added thereto, followed by stirring for 5 hours at 50° C. Next, the solid content was filtered off by reduced pressure filtration and dried under reduced pressure at 60° C. to obtain zinc oxide with alizarin added thereto.

[0160] 100 parts of a solution obtained by dissolving 60 parts of alizarin-added zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, trade name: Sumidur BL3175, manufactured by Sumitomo Bayern Urethane Co., Ltd., solid content 25% by mass), and 10 parts of a butyral resin (trade name: S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) in 68 parts of methyl ethyl ketone was mixed with 5 parts of methyl ethyl ketone, and the mixture was dispersed for 2 hours in a sand mill using glass beads having a diameter of 1 mm to obtain a dispersion. 0.005 parts of dioctyltin dilaurate was added to the dispersion as a catalyst to obtain a coating liquid for forming an undercoat layer. This coating liquid was applied to the outer peripheral surface of the conductive substrate (1) by dip coating, and the coating was dried and cured at 170°C for 40 minutes to form an undercoat layer. The layer thickness of the undercoat layer is as shown in Table 1.

[0161] <Examples 11 to 17> Each photoreceptor was prepared in the same manner as in Example 10, except that the type of conductive substrate, the thickness of the undercoat layer, and the type of metal oxide particles were changed to those shown in Table 1.

[0162] <Photoreceptor performance evaluation> [Image graininess] Under an environment of 23°C temperature and 55% relative humidity, cyan halftone images with image densities of 5% to 100% were printed in 5% increments on A3-sized plain paper, and the roughness was evaluated visually. The results are shown in Table 1. G1: No roughness is felt. G2: A slight sense of graininess is felt in low-density images. G3: A slight sense of grain is felt in low-density and medium-density images. G4: A sense of grain is felt from low density images to high density images.

[0163] [Table 1]

[0164] The electrophotographic photoreceptor, the method for producing the electrophotographic photoreceptor, the process cartridge, and the image forming apparatus of the present disclosure include the following aspects.

[0165] (((1))) A conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, In a power spectrum obtained by subjecting a roughness curve in an axial direction of the outer peripheral surface of the conductive substrate to a fast Fourier transform, an integrated value of intensity in a periodic range of 0.01 mm or more and 0.1 mm or less is 0.02 or more and 0.10 or less, The thickness of the undercoat layer is 10 μm or more. Electrophotographic photoreceptor. (((2))) The electrophotographic photoreceptor according to (((1))), wherein the undercoat layer has a thickness of 20 μm or more. (((3))) A conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, In a power spectrum obtained by subjecting a roughness curve in an axial direction of the outer peripheral surface of the conductive substrate to a fast Fourier transform, an integrated value of intensity in a periodic range of 0.01 mm or more and 0.1 mm or less is 0.02 or more and 0.10 or less, The undercoat layer contains metal oxide particles. Electrophotographic photoreceptor. (((4))) The electrophotographic photoreceptor according to (((3))), wherein the metal oxide particles include at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, and tin oxide particles. (((5))) The electrophotographic photoreceptor according to (((3))) or (((4))), wherein the average particle size of the metal oxide particles is 10 nm or more and 80 nm or less. (((6))) The electrophotographic photoreceptor according to any one of (((3))) to (((5))), wherein the mass ratio of the metal oxide particles in the undercoat layer is 60 mass % or more and 95 mass % or less. (((7))) A method for producing an electrophotographic photoreceptor according to any one of (((1))) to (((6))), comprising the steps of: removing all layers on the conductive substrate from a used electrophotographic photoreceptor by a water jet to regenerate the conductive substrate; forming an undercoat layer on the regenerated conductive substrate; forming a photosensitive layer on the undercoat layer; A method for manufacturing an electrophotographic photoreceptor. (((8))) An electrophotographic photoreceptor according to any one of (((1))) to (((6))), A process cartridge that is detachably attached to an image forming apparatus. (((9))) An electrophotographic photoreceptor according to any one of (((1))) to (((6))), a charging device for charging a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising:

[0166] According to (((1))), an electrophotographic photoreceptor is provided which has an undercoat layer with a layer thickness of less than 10 μm and which forms images with excellent graininess compared to an electrophotographic photoreceptor which does not contain metal oxide particles in the undercoat layer. According to (((2))), an electrophotographic photoreceptor is provided which forms images with excellent graininess, as compared with electrophotographic photoreceptors having an undercoat layer with a thickness of less than 20 μm. According to (((3))), (((4))), (((5))) or (((6))), an electrophotographic photoreceptor is provided which has an undercoat layer with a layer thickness of less than 10 μm and which forms images with excellent graininess as compared with an electrophotographic photoreceptor which does not contain metal oxide particles in the undercoat layer. According to ((7)), a method for producing an electrophotographic photoreceptor that forms an image with excellent graininess is provided. According to (((8))), a process cartridge is provided which forms images which are excellent in graininess compared to a process cartridge equipped with an electrophotographic photoreceptor in which the undercoat layer has a layer thickness of less than 10 μm and the undercoat layer does not contain metal oxide particles. According to (((9))), an image forming apparatus is provided which forms images having excellent graininess compared to an image forming apparatus including an electrophotographic photoreceptor in which the undercoat layer has a layer thickness of less than 10 μm and the undercoat layer does not contain metal oxide particles. [Explanation of symbols]

[0167] 1 Conductive substrate, 2 Undercoat layer, 3 Charge generation layer, 4 Charge transport layer, 5 Photosensitive layer, 10A photoreceptor, 10B photoreceptor

[0168] 7 electrophotographic photosensitive member, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 40 transfer device, 50 intermediate transfer body, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll-shaped), 133 fibrous member (flat brush-shaped), 300 process cartridge

Claims

1. A conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, a power spectrum obtained by subjecting a roughness curve in an axial direction of the outer peripheral surface of the conductive substrate to a fast Fourier transform has an integrated intensity value of 0.02 or more and 0.10 or less in a periodic range of 0.01 mm or more and 0.1 mm or less; The thickness of the undercoat layer is 10 μm or more. Electrophotographic photoreceptor.

2. 2. The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer has a thickness of 20 [mu]m or more.

3. A conductive substrate, an undercoat layer disposed on the conductive substrate, and a photosensitive layer disposed on the undercoat layer, a power spectrum obtained by subjecting a roughness curve in an axial direction of the outer peripheral surface of the conductive substrate to a fast Fourier transform has an integrated intensity value of 0.02 or more and 0.10 or less in a periodic range of 0.01 mm or more and 0.1 mm or less; The undercoat layer contains metal oxide particles. Electrophotographic photoreceptor.

4. The electrophotographic photoreceptor according to claim 3 , wherein the metal oxide particles include at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, and tin oxide particles.

5. The electrophotographic photoreceptor according to claim 3 , wherein the metal oxide particles have an average particle size of 10 nm or more and 80 nm or less.

6. The electrophotographic photoreceptor according to claim 3 , wherein a mass ratio of the metal oxide particles in the undercoat layer is from 60% by mass to 95% by mass.

7. A method for producing the electrophotographic photoreceptor according to any one of claims 1 to 6, comprising the steps of: removing all layers on the conductive substrate from a used electrophotographic photoreceptor by a water jet to regenerate the conductive substrate; forming an undercoat layer on the regenerated conductive substrate; forming a photosensitive layer on the undercoat layer; A method for manufacturing an electrophotographic photoreceptor.

8. The electrophotographic photoreceptor according to any one of claims 1 to 6 is provided, A process cartridge that is detachably attached to an image forming apparatus.

9. The electrophotographic photoreceptor according to any one of claims 1 to 6, a charging device for charging a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising:

Images