Electrophotographic photoreceptor, process cartridge, and image forming device

Abstract

To provide an electrophotographic photoreceptor which is less susceptible to charge leakage, and to fogging when continuously forming images.SOLUTION: An electrophotographic photoreceptor is provided, comprising a conductive base, a charge generating layer arranged on the conductive base, a charge transport layer arranged on the charge generating layer, and a protective layer arranged on the charge transport layer, where a ratio L / ε of a total thickness L (μm) of the charge transport layer and the protective layer to a composite permittivity ε(F / m) of the entirety of the charge transport layer and the protective layer in a thickness direction is in a range of 3 to 6, inclusive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an image forming apparatus that does not have a discharging means, and in which image forming units including an electrophotographic photosensitive member and charging, exposing and developing devices are arranged along a transfer material transport path, the electrophotographic photosensitive member is charged by applying only a DC voltage to a charging member arranged in contact with the electrophotographic photosensitive member, and an image is formed by directly transferring a toner image developed on the electrophotographic photosensitive member to a transported transfer material, the image forming apparatus having a dark decay of 15 V or less after one minute when the surface of the electrophotographic photosensitive member is charged to +500 V in an environment of 23°C / 55% RH, and the film thickness d of the charge transport layer of the electrophotographic photosensitive member, the relative dielectric constant ε of the binder resin of the charge transport layer, and the absolute value V of the dark potential of the photosensitive member satisfy the relationship of equation (1) d÷ε×V≧3000.

[0003] Patent Document 2 discloses an image forming apparatus including: an electrophotographic photoreceptor having a conductive substrate and a photosensitive layer provided on the conductive substrate, the outermost surface layer being constituted by a cured film of a composition containing a reactive charge transport material; charging means arranged in contact with or close to the surface of the electrophotographic photoreceptor and charging the surface of the electrophotographic photoreceptor; electrostatic latent image forming means for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; developing means that contains a developer containing a toner having toner particles and inorganic particles with a volume average particle size of 1 μm or less and develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with the developer to form a toner image; transfer means that transfers the toner image to the surface of a recording medium; and cleaning means that has a cleaning blade that contacts the surface of the electrophotographic photoreceptor and cleans the surface of the electrophotographic photoreceptor, the cleaning blade having at least a portion in contact with the electrophotographic photoreceptor being constituted by a rubber-modified portion into which plasma ions have been injected.

[0004] Patent Document 3 discloses an electrophotographic photoreceptor comprising a conductive substrate having a thickness of 3 mm or more, a photosensitive layer provided on the conductive substrate, and a surface protective layer provided on the photosensitive layer, wherein the surface protective layer is a layer constituted by 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, or a cured film of a composition containing a non-reactive charge transport material and a reactive group-containing non-charge transport material having no charge transport skeleton and a reactive group, and wherein the ratio of the degree of curing of the surface on the conductive substrate side to the degree of curing of the surface on the outer peripheral surface side is 75% or more.

[0005] Patent Document 4 describes a photosensitive member having a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer, and a roll-shaped charging member that contacts the photosensitive member to charge it, and the charge required to charge the photosensitive member is 1.65 μC / (m 2 ·V) or more is disclosed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-300742 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-142916 [Patent Document 3] Japanese Patent Publication No. 2023-120986 [Patent Document 4] Japanese Patent Application Publication No. 2023-142267 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present disclosure is to provide an electrophotographic photoreceptor that is less likely to suffer from charge leakage (local charge leakage that occurs when an electrophotographic photoreceptor is charged) than an electrophotographic photoreceptor having a ratio L / ε of less than 3, where L is the total thickness L (μm) of the charge transport layer and protective layer, and ε is the dielectric constant ε (F / m) of the charge transport layer and protective layer in the overall thickness direction, and is less likely to suffer from fogging (a phenomenon in which toner adheres to non-image areas of a recording medium) during continuous image formation than an electrophotographic photoreceptor having a ratio L / ε of more than 6. [Means for solving the problem]

[0008] Specific means for solving the above problems include the following aspects. <1> a conductive substrate; a charge generating layer disposed on the conductive substrate; a charge transport layer disposed on the charge generating layer; a protective layer disposed on the charge transport layer, a ratio L / ε of a total thickness L (μm) of the charge transport layer and the protective layer to a dielectric constant ε (F / m) of the entire charge transport layer and the protective layer in the thickness direction is 3 or more and 6 or less; Electrophotographic photoreceptor. <2> The value of the ratio L / ε is 4.5 or more and 5.5 or less. <1> The electrophotographic photoreceptor according to claim 1. <3> the protective layer is a cured or crosslinked film of a composition containing a reactive charge transport material; <1> or <2> The electrophotographic photoreceptor according to claim 1. <4> The total thickness L is 10 μm or more and 20 μm or less, <1> ~ <3> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <5> a ratio L2 / L1 of a thickness L1 of the charge transport layer to a thickness L2 of the protective layer is 0.1 or more and 1 or less; <1> ~ <4> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <6> a charging device for charging a surface of an electrophotographic photosensitive member, the charging device having a charging member in contact with the electrophotographic photosensitive member and applying only a DC voltage to the charging member; a static elimination device that irradiates a static elimination light onto the surface of the electrophotographic photosensitive member to eliminate static electricity after the toner image is transferred onto the surface of the recording medium; For use in an image forming apparatus having <1> ~ <5> 10. The electrophotographic photoreceptor according to claim 9, wherein the first and second electrodes are electrically connected to the first and second electrodes. <7> <1> ~ <5> 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. <8> a static elimination device that irradiates the surface of the electrophotographic photosensitive member with static elimination light to eliminate static electricity after the toner image is transferred to the surface of the recording medium; <7> The process cartridge according to claim 1. <9> a charging device for charging the surface of the electrophotographic photosensitive member, the charging device having a charging member in contact with the electrophotographic photosensitive member and applying only a DC voltage to the charging member; <7> or <8> The process cartridge according to claim 1. <10> <1> ~ <5> an electrophotographic photoreceptor according to any one of the above items; a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; a static elimination device that irradiates a static elimination light onto the surface of the electrophotographic photosensitive member to eliminate static electricity after the toner image is transferred onto the surface of the recording medium; An image forming apparatus comprising: <11> the charging device has a charging member that contacts the electrophotographic photosensitive member, and applies only a DC voltage to the charging member; <10> 2. The image forming apparatus according to claim 1 . [Effects of the Invention]

[0009] <1> , <3> or <6> According to the above, an electrophotographic photosensitive member is provided which is less likely to cause charge leakage than an electrophotographic photosensitive member having a ratio L / ε value of less than 3, and an electrophotographic photosensitive member is provided which is less likely to cause fogging during continuous image formation than an electrophotographic photosensitive member having a ratio L / ε value of more than 6. <2> According to the above, an electrophotographic photosensitive member is provided which is less likely to cause charge leakage than an electrophotographic photosensitive member having a ratio L / ε value of less than 4.5, and an electrophotographic photosensitive member is provided which is less likely to cause fogging during continuous image formation than an electrophotographic photosensitive member having a ratio L / ε value of more than 5.5. <4> According to the present invention, an electrophotographic photoreceptor is provided which is less susceptible to charge leakage compared to an electrophotographic photoreceptor in which the total thickness L of the charge transport layer and the protective layer is less than 10 μm, and an electrophotographic photoreceptor is provided which is less susceptible to fogging during continuous image formation compared to an electrophotographic photoreceptor in which the total thickness L of the charge transport layer and the protective layer is more than 20 μm. <5> According to this, an electrophotographic photoreceptor is provided which is less susceptible to charge leakage than an electrophotographic photoreceptor in which the ratio L2 / L1 of the layer thickness L1 of the charge transport layer to the layer thickness L2 of the protective layer is less than 0.1. <7> , <8> or <9> According to the present invention, a process cartridge is provided which is less susceptible to charge leakage than a process cartridge in which the ratio L / ε of the electrophotographic photosensitive member is less than 3, and a process cartridge is provided which is less susceptible to fogging during continuous image formation than a process cartridge in which the ratio L / ε of the electrophotographic photosensitive member is more than 6. <10> or <11> According to the present invention, an image forming apparatus is provided which is less likely to cause charge leakage than an image forming apparatus in which the value of the ratio L / ε of the electrophotographic photosensitive member is less than 3, and an image forming apparatus is provided which is less likely to cause fogging when continuously forming images than an image forming apparatus in which the value of the ratio L / ε of the electrophotographic photosensitive member is more than 6. [Brief explanation of the drawings]

[0010] [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 exemplary embodiment. [Figure 2]1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 3] FIG. 10 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011]

[0023] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0012] In the present disclosure, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B.

[0013] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, 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. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0014] 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.

[0015] When embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these.

[0016] In the present disclosure, each component may contain multiple 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 composition may contain multiple types of particles corresponding to each component. 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.

[0017] In the present disclosure, when a compound is represented 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. In the present disclosure, alkyl groups and alkylene groups include any of linear, branched and cyclic groups, unless otherwise specified. In the present disclosure, a hydrogen atom in an organic group, aromatic ring, linking group, alkyl group, alkylene group, aryl group, aralkyl group, alkoxy group, aryloxy group, or the like may be substituted with a halogen atom. In the present disclosure, "(meth)acrylic" is an expression that includes both acrylic and methacrylic, and "(meth)acrylate" is an expression that includes both acrylate and methacrylate. In the present disclosure, the term "structural unit" of a copolymer or resin has the same meaning as a monomer unit.

[0018] 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.

[0019] <Electrophotographic photoreceptor> The electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") according to this embodiment has a conductive substrate, a charge generation layer disposed on the conductive substrate, a charge transport layer disposed on the charge generation layer, and a protective layer disposed on the charge transport layer. The charge generation layer and the charge transport layer are photosensitive layers (so-called laminated photosensitive layers or function-separated photosensitive layers). The photoreceptor according to this embodiment may further include layers other than the charge generating layer, the charge transport layer, and the protective layer (for example, an undercoat layer, an intermediate layer).

[0020] Fig. 1 is a partial cross-sectional view schematically illustrating an example of the layer structure of a photoreceptor according to this embodiment. Photoreceptor 10A shown in Fig. 1 has a structure in which an undercoat layer 2, a charge generation layer 3, a charge transport layer 4, and a protective layer 6 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. Photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3. The undercoat layer 2 may or may not be present.

[0021] The photoreceptor according to this embodiment has a ratio L / ε of the total thickness L (μm) of the charge transport layer and protective layer to the dielectric constant ε (F / m) of the charge transport layer and protective layer in the overall thickness direction, which is between 3 and 6. The photoreceptor according to this embodiment is less likely to suffer from charge leakage (localized charge leakage that occurs when the photoreceptor is charged), and is less likely to suffer from fogging (the phenomenon in which toner adheres to non-image areas of a recording medium) during continuous image formation. The mechanism behind this is presumed to be as follows.

[0022] When continuously forming images using an image forming apparatus equipped with a photoreceptor having a protective layer on its surface, fogging sometimes occurs. This phenomenon is likely to occur in image forming apparatuses equipped with a static eliminator that irradiates the surface of the photoreceptor with static elimination light to eliminate static electricity. It is believed that the cause is that charges generated in the charge generation layer by the irradiation of static elimination light gradually accumulate in the charge transport layer and protective layer, causing a gradual decrease in the surface potential of the photoreceptor. Furthermore, the above phenomenon was even more likely to occur in an image forming apparatus equipped with a charging device (hereinafter also referred to as a "contact-type DC charging device") that has a charging member in contact with the photosensitive member and applies only a DC voltage to the charging member. It was speculated that charges generated in the charge generating layer by irradiation with static elimination light were accumulated in the charge transport layer and protective layer, and the accumulated charges were transferred to the surface of the photosensitive member by charging with the contact-type DC charging device, which made it easier for the surface potential of the photosensitive member to decrease. The photoreceptor according to this embodiment prevents charge accumulation in the charge transport layer and the protective layer by balancing the total thickness L (μm) of the charge transport layer and the protective layer with the dielectric constant ε (F / m) of the charge transport layer and the protective layer in the overall thickness direction, thereby preventing a decrease in the surface potential of the photoreceptor and the occurrence of fogging.

[0023] In the photoreceptor according to this embodiment, the ratio L / ε of the total thickness L (μm) of the charge transport layer and the protective layer to the dielectric constant ε (F / m) of the entire charge transport layer and the protective layer in the thickness direction is 3 or more and 6 or less. If the ratio L / ε exceeds 6, the total thickness L of the charge transport layer and the protective layer is too thick compared to the value of the dielectric constant ε, and the charges generated in the charge generation layer by irradiation with static elimination light tend to accumulate in the charge transport layer and the protective layer, resulting in a decrease in the surface potential of the photoreceptor and the occurrence of fogging. If the ratio L / ε is less than 3, the total thickness L of the charge transport layer and the protective layer is small, and local charge leakage (charge leakage) is likely to occur when the photosensitive member is charged. In order to suppress the above-mentioned phenomenon, the value of the ratio L / ε is 3 or more and 6 or less, more preferably 4 or more and 6 or less, even more preferably 4.5 or more and 5.8 or less, and even more preferably 4.5 or more and 5.5 or less.

[0024] In the photoreceptor according to this embodiment, the total thickness L of the charge transport layer and the protective layer is preferably 10 μm or more and 20 μm or less. If the total thickness L is 20 μm or less, the charges generated in the charge generating layer by irradiation with static eliminating light are less likely to accumulate in the charge transport layer and the protective layer. From this viewpoint, the total thickness L is more preferably 18 μm or less. When the total thickness L is 10 μm or more, charge leakage is unlikely to occur. From this viewpoint, the total thickness L is more preferably 12 μm or more.

[0025] In the photoreceptor according to this embodiment, the ratio L2 / L1 of the thickness L1 of the charge transport layer to the thickness L2 of the protective layer is preferably 0.1 or more and 1 or less. When the ratio L2 / L1 is 1 or less, the charge transport layer is not too thin, which is preferable in terms of the electrical properties of the photoreceptor. From this viewpoint, the ratio L2 / L1 is more preferably 0.9 or less, and even more preferably 0.8 or less. When the ratio L2 / L1 is 0.1 or more, charge leakage is unlikely to occur. From this viewpoint, the total thickness L is more preferably 0.3 or more, and further preferably 0.5 or more.

[0026] In this embodiment, the thickness L1 of the charge transport layer, the thickness L2 of the protective layer, and the total thickness L of the charge transport layer and the protective layer have the following physical property values. The thickness L1 of the charge transport layer is the arithmetic average of the thicknesses of the charge transport layer measured using an eddy current film thickness meter at 10 locations evenly spaced along the axial direction of the photosensitive member and at four equal locations (at 90° intervals) around the circumference, for a total of 40 locations. The thickness L2 of the protective layer is the arithmetic average of the thicknesses of the protective layer measured using an eddy current film thickness meter at 10 locations evenly spaced along the axial direction of the photosensitive member and at four equal locations (at 90° intervals) around the circumference, for a total of 40 locations. The total thickness L of the charge transport layer and the protective layer is the sum of the layer thickness L1 and the layer thickness L2.

[0027] The dielectric constant ε (F / m) in the thickness direction of the entire charge transport layer and protective layer was measured as follows.

[0028] -Preparation of samples for capacitance measurement- The surface of the photoreceptor is cut using a single-edged razor, and the charge transport layer and protective layer are peeled off with tweezers. Gold electrodes are formed on both sides of the peeled film (a laminate of the charge transport layer and protective layer) by vacuum deposition or sputtering, to obtain a sample for capacitance measurement.

[0029] -Capacitance measurement using AC impedance method- The measurement device and measurement conditions are as follows. ·Power supply: SI1287 electrochemical interface (Solartron Analytical) ·Ammeter: SI1260 inpedance / gain phase analyzer (Solartron Analytical) Current amplifier: 1296 dielectric interface (Solartron Analytical) AC voltage: 1Vp-p Measurement frequency: Apply from the high frequency side from 1MHz to 1mHz. Measurement environment: Temperature 22°C, relative humidity 55% The sample is sandwiched between an aluminum plate (cathode) and a gold electrode (anode), and the AC impedance is measured using the above-mentioned measuring device and conditions. The capacitance is calculated by fitting the Cole-Cole plot to an RC parallel equivalent circuit. The dielectric constant ε is calculated based on the formula: capacitance C = dielectric constant ε × S / L (S: electrode area, L: sample thickness).

[0030] The dielectric constant ε (F / m) of the charge transport layer and the protective layer in the overall thickness direction is preferably 3.0 to 4.0, more preferably 3.1 to 3.8, and even more preferably 3.2 to 3.5. The dielectric constant ε (F / m) of the charge transport layer in the thickness direction is preferably 2.5 to 3.8, more preferably 2.8 to 3.5, and even more preferably 3.0 to 3.3. The value of the dielectric constant ε (F / m) in the thickness direction of the protective layer is preferably 3.2 or more and 4.5 or less, more preferably 3.4 or more and 4.2 or less, and even more preferably 3.6 or more and 4.0 or less.

[0031] The method for measuring the dielectric constant ε in the thickness direction of the charge transport layer and the dielectric constant ε in the thickness direction of the protective layer is the same as the method for measuring the dielectric constant ε in the thickness direction of the entire charge transport layer and the protective layer.

[0032] The dielectric constant ε (F / m) of the charge transport layer and the protective layer in the thickness direction can be controlled by the content of the charge transport material in each layer. The higher the content of the charge transport material, the smaller the dielectric constant ε.

[0033] The photoreceptor according to this embodiment is suitable as a photoreceptor for use in an image forming apparatus having a charging device that has a charging member in contact with the photoreceptor and applies only a DC voltage to the charging member, and a discharging device that transfers a toner image to the surface of a recording medium and then irradiates the surface of the photoreceptor with discharging light to dissipate electricity.

[0034] Hereinafter, each layer of the electrophotographic photoreceptor according to this embodiment will be described in detail.

[0035] [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, 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" refers to a material having a volume resistivity of 1×10 13 This means that the resistance is less than Ω·cm.

[0036] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center line average roughness Ra of 0.04 μm to 0.5 μm inclusive in order to suppress interference fringes that occur when irradiated with laser light. When incoherent light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for extending the life of the conductive substrate by suppressing defects caused by surface irregularities.

[0037] Examples of methods for roughening the surface include wet honing, which involves spraying an abrasive suspended in water onto the conductive substrate; centerless grinding, which involves pressing the conductive substrate against a rotating grinding wheel and continuously grinding the substrate; and anodizing.

[0038] As a method for roughening the surface, there may be mentioned a method in which, without roughening the surface of the conductive substrate, conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the surface is roughened by the particles dispersed in the layer.

[0039] Anodizing is a surface roughening treatment that uses a metallic (e.g., aluminum) conductive substrate as the anode and anodizes it in an electrolyte solution to form an oxide film on the surface of the conductive substrate. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active in its original state, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film, in which the micropores of the oxide film are sealed by volume expansion caused by hydration in pressurized steam or boiling water (with the addition of a metal salt such as nickel), converting the film into a more stable hydrated oxide.

[0040] The thickness of the anodic oxide film is preferably, for example, from 0.3 μm to 15 μm, inclusive, and within this range, the film tends to exhibit barrier properties against injection and also tends to suppress an increase in residual potential due to repeated use.

[0041] The conductive substrate may be subjected to a treatment with an acidic treatment solution or a boehmite treatment. Treatment with an acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The compounding ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution are, for example, in the range of 10% by mass to 11% by mass for phosphoric acid, 3% by mass to 5% by mass for chromic acid, and 0.5% by mass to 2% by mass for hydrofluoric acid, with the total concentration of these acids preferably in the range of 13.5% by mass to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness of the coating is preferably 0.3 μm to 15 μm.

[0042] The boehmite treatment is carried out, for example, by immersing the steel sheet in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting the steel sheet with heated steam at 90°C to 120°C for 5 to 60 minutes. The coating film preferably has a thickness of 0.1 μm to 5 μm. This may be further anodized using an electrolyte solution with low coating solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0043] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0044] For example, inorganic particles have a powder resistance (volume resistivity) of 1×10 2 Ω cm or more 1×10 11 Examples include inorganic particles with a particle size of Ω·cm or less. Among these, inorganic particles having the above resistance value are preferably 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.

[0045] The specific surface area of ​​inorganic particles measured by the BET method is, for example, 10 m 2 / g or more 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).

[0046] The content of the inorganic particles is, for example, preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less, relative to the binder resin.

[0047] The inorganic particles may be surface-treated, and two or more types of inorganic particles having different surface treatments or different particle sizes may be used in combination.

[0048] Examples of the surface treatment agent include a silane coupling agent, a titanate-based coupling agent, an aluminum-based coupling agent, a surfactant, etc. In particular, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

[0049] 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.

[0050] Two or more silane coupling agents may be used in combination. 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.

[0051] 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.

[0052] 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 relative to the inorganic particles.

[0053] Here, it is preferable that the undercoat layer contains an electron-accepting compound (acceptor compound) together with the inorganic particles, from the viewpoint of improving the long-term stability of the electrical properties and the carrier blocking property.

[0054] Examples of electron-accepting compounds include 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, such as a hydroxyanthraquinone compound, an aminoanthraquinone compound, or an aminohydroxyanthraquinone compound, and specifically, for example, anthraquinone, alizarin, quinizarin, anthrarphine, or purpurin.

[0055] 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 surface of the inorganic particles.

[0056] The electron-accepting compound can be attached to the surface of the inorganic particles by, for example, a dry method or a wet method.

[0057] The dry method is a method in which, while stirring inorganic particles using a mixer or the like with high shear force, an electron-accepting compound is added dropwise, either directly or dissolved in an organic solvent, or sprayed together with dry air or nitrogen gas to adhere the electron-accepting compound to the surface of the inorganic particles. The electron-accepting compound is preferably added dropwise or sprayed at a temperature below the boiling point of the solvent. After the electron-accepting compound has been added dropwise or sprayed, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as they achieve electrophotographic properties.

[0058] The wet method involves dispersing inorganic particles in a solvent using, for example, stirring, ultrasonic waves, a sand mill, an attritor, or a ball mill, while adding an electron-accepting compound. The mixture is stirred or dispersed, and then the solvent is removed to adhere the electron-accepting compound to the surfaces of the inorganic particles. The solvent can be removed, for example, by filtration or distillation. After solvent removal, 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. Examples of such methods include a method of removing the moisture by stirring and heating in a solvent, and a method of removing the moisture by azeotropy with the solvent.

[0059] The attachment of the electron-accepting compound may be carried out before or after the inorganic particles are surface-treated with a surface-treating agent, or the attachment of the electron-accepting compound and the surface treatment with a surface-treating agent may be carried out simultaneously.

[0060] The content of the electron-accepting compound is, for example, 0.01% by mass or more and 20% by mass or less, and preferably 0.01% by mass or more and 10% by mass or less, based on the inorganic particles.

[0061] Examples of binder resins used in the undercoat layer include known 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, 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, phenolic 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 binder resins used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline), and the like.

[0062] 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, phenolic resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins, and polyamide resins, polyester resins, polyether resins, methacrylic resins, acrylic resins, polyvinyl alcohol resins, and polyvinyl acetal 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.

[0063] The undercoat layer may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of additives include known materials such as polycyclic condensation and azo electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Silane coupling agents are used for the surface treatment of inorganic particles as described above, and may also be added to the undercoat layer as an additive.

[0064] 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, and 3-chloropropyltrimethoxysilane.

[0065] Examples of zirconium chelate compounds 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.

[0066] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-normal-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.

[0067] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, ethyl acetoacetate aluminum diisopropylate, and aluminum tris(ethyl acetoacetate).

[0068] These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0069] 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 to suppress moire images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of 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 polishing methods include buffing, sandblasting, wet honing, and grinding.

[0070] 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 liquid for forming an undercoat layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0071] Examples of solvents 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.

[0072] Examples of a method for dispersing inorganic particles when preparing a coating liquid for forming an undercoat layer include known methods such as using a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0073] Examples of methods for applying the coating liquid for forming the undercoat layer onto the conductive substrate include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0074] The thickness of the undercoat layer is set, for example, preferably at least 15 μm, more preferably in the range of from 20 μm to 50 μm.

[0075] [Middle layer] 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 the resin used in the intermediate layer include polymer compounds such as acetal resins (such as polyvinyl butyral), 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.

[0076] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0077] 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 liquid for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it if 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, air knife coating, and curtain coating.

[0078] The thickness of the intermediate layer is preferably set in the range of, for example, 0.1 μm to 3 μm, and the intermediate layer may also be used as an undercoat layer.

[0079] [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 for use with an incoherent light source such as an LED (Light Emitting Diode) or an organic EL (Electroluminescence) image array.

[0080] Examples of the charge generating material include azo pigments such as bisazo and trisazo; fused-ring aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0081] Among these, in order to be compatible with 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, and more specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine are more preferable.

[0082] On the other hand, in order to accommodate laser exposure in the near ultraviolet region, preferred charge generating materials include fused ring aromatic pigments such as dibromoanthanthrone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and bisazo pigments.

[0083] The above charge generating material may also be used when an incoherent light source such as an LED or organic EL image array having a central emission wavelength of 450 nm or more and 780 nm or less is used.

[0084] In contrast, when n-type semiconductors such as fused-ring aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark current is less likely to occur, and image defects known as black spots can be suppressed even in thin films. The n-type is determined by the polarity of the photocurrent that flows using the commonly used time-of-flight method, and materials that more easily pass electrons as carriers than holes are considered n-type.

[0085] 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, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (e.g., polycondensation product of bisphenols and aromatic dicarboxylic 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, polyvinylpyrrolidone resin, etc. Here, "insulating" means a material having a volume resistivity of 1×10 13 This means that the resistance is Ω·cm or more. These binder resins may be used alone or in combination of two or more.

[0086] The compounding ratio of the charge generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass.

[0087] The charge generating layer may contain other known additives.

[0088] The formation of the charge generation layer is not particularly limited, and a known formation method can be used. For example, the charge generation layer can be formed by forming a coating film of a coating liquid for forming the charge generation layer by adding the above components to a solvent, drying the coating film, and heating it as necessary. The charge generation layer can also be formed by vapor deposition of the charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when a fused ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0089] Examples of solvents 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.

[0090] Methods for dispersing particles (e.g., charge generating material) in the coating liquid for forming the charge generating layer include, for example, media dispersers such as ball mills, vibration ball mills, attritors, sand mills, and horizontal sand mills, and medialess dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. 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 liquid is dispersed by passing through a fine flow path under high pressure. During this dispersion, it is effective to adjust the average particle size of the charge generating material in the coating liquid for forming the charge generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0091] Examples of methods 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.

[0092] The thickness of the charge generating layer is set, for example, preferably in the range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0093] [Charge transport layer] The charge transport layer is, for example, a layer containing a charge transport material and a binder resin, or may be a layer containing a polymer charge transport material.

[0094] Examples of charge transport materials include electron transport 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 charge transport materials 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, but are not limited to these.

[0095] As the charge transport material, triarylamine derivatives represented by the following structural formula (a-1) and benzidine derivatives represented by the following structural formula (a-2) are preferred from the viewpoint of charge mobility.

[0096] [ka]

[0097] In 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 ) indicates 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. Examples of the substituents on the above groups include halogen atoms, alkyl groups having from 1 to 5 carbon atoms, and alkoxy groups having from 1 to 5 carbon atoms. Examples of the substituents on the above groups also include substituted amino groups substituted with alkyl groups having from 1 to 3 carbon atoms.

[0098] [ka]

[0099] 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 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ) and R T12 , R T13 , R T14 , R T15 and R T16 each 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 substituents on the above groups include halogen atoms, alkyl groups having from 1 to 5 carbon atoms, and alkoxy groups having from 1 to 5 carbon atoms. Examples of the substituents on the above groups also include substituted amino groups substituted with alkyl groups having from 1 to 3 carbon atoms.

[0100] Among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), "-C6H4-CH=CH-CH=C(R T7 )(RT8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 ) is preferred from the viewpoint of charge mobility.

[0101] Examples of polymer charge transport materials include known materials having charge transport properties, such as poly-N-vinylcarbazole and polysilane. Among these, polyester polymer charge transport materials are preferred. The polymer charge transport material may be used alone or in combination with a binder resin.

[0102] Examples of binder resins used in the charge transport layer include polycarbonate resins, polyester resins, polyarylate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, and polysilanes. These binder resins can be used alone or in combination. The blending ratio of the charge transport material to the binder resin is preferably 10:1 to 1:5 by mass. From the viewpoint of durability of the charge transport layer, the binder resin is preferably at least one selected from the group consisting of polycarbonate resins and polyarylate resins. The polycarbonate resin and polyarylate resin may be used alone or alone, or may be a mixture of the polycarbonate resin and the polyarylate resin.

[0103] The charge transport layer may contain other known additives, such as antioxidants, leveling agents, antifoaming agents, fillers, and viscosity modifiers.

[0104] 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.

[0105] Examples of solvents for preparing the coating solution 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.

[0106] Examples of a coating method for applying the coating liquid for forming the charge transport layer onto the charge generating layer include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0107] The thickness of the charge transport layer is preferably from 5 μm to 30 μm, more preferably from 8 μm to 20 μm, and even more preferably from 10 μm to 15 μm. When the thickness of the charge transport layer is 30 μm or less, the charges generated in the charge generation layer by irradiation with static elimination light are less likely to accumulate in the charge transport layer, and as a result, fogging is less likely to occur in the image. From this viewpoint, the thickness of the charge transport layer is more preferably 20 μm or less, and even more preferably 15 μm or less. A charge transport layer thickness of 5 μm or more is preferable in terms of the electrical properties of the photoreceptor, and from this viewpoint, the thickness of the charge transport layer is more preferably 8 μm or more, and even more preferably 10 μm or more.

[0108] [Protective layer] The protective layer is provided on the photosensitive layer. The protective layer is the outermost layer of the photoreceptor. The protective layer is provided, for example, for the purposes of suppressing chemical changes in the photosensitive layer when it is charged and for the purposes of improving the mechanical strength of the photosensitive layer.

[0109] The protective layer is preferably a cured or crosslinked film layer, and specifically, the following form (1) or form (2) is preferred. According to the following form (1) or form (2), chemical changes in the photosensitive layer during charging are suppressed, and the abrasion resistance of the protective layer is further improved.

[0110] Form (1): A cured or crosslinked film of a composition containing a reactive charge transport material having a reactive group and a charge transport skeleton in the same molecule. That is, a layer containing a polymer or crosslinked product of a reactive charge transport material. The layer may also contain a polymer or crosslinked product of a reactive non-charge transport material having a reactive group in the molecule but not a charge transport skeleton. The layer may also contain a polymer or crosslinked product of a reactive charge transport material and a reactive non-charge transport material. The layer may also contain a non-reactive charge transport material not having a reactive group in the molecule.

[0111] Form (2): A cured or crosslinked film of a composition containing a non-reactive charge transport material having no reactive groups in the molecule and a reactive non-charge transport material having reactive groups in the molecule but no charge transport skeleton, i.e., a layer containing a polymer or crosslinked product of the non-reactive charge transport material and the reactive non-charge transport material.

[0112] The protective layer is preferably in form (1) of form (1) and form (2). Compared to form (2), form (1) has a higher hardness and is more excellent in abrasion resistance.

[0113] The reactive charge transport material, non-reactive charge transport material, and reactive non-charge transport material may be selected from known materials. Preferred embodiments of the reactive charge transport material, non-reactive charge transport material, and reactive non-charge transport material will be described below.

[0114] The reactive group of the reactive charge transport material may be a chain polymerizable group, an epoxy group, -OH, -OR (where R represents an alkyl group), -NH2, -SH, -COOH, or -SiR. a 3-n (OR b ) n [R arepresents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group, and R b represents a hydrogen atom, an alkyl group, or a trialkylsilyl group. n represents an integer of 1 or more and 3 or less.]. The reactive group in the reactive non-charge transport material may also be the above-mentioned reactive groups.

[0115] The chain polymerizable group may be any functional group capable of radical polymerization, such as a functional group having a carbon double bond. Specific examples include groups having at least one selected from a vinyl group, a vinyl ether group, a vinyl thioether group, a styryl group (phenylvinyl group), a vinylphenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof. From the viewpoint of excellent reactivity, the chain polymerizable group is preferably a group having at least one selected from a vinyl group, a styryl group (phenylvinyl group), a vinylphenyl group, an acryloyl group, a methacryloyl group, and derivatives thereof.

[0116] Examples of the charge transporting skeleton of the reactive charge transporting material include a skeleton derived from a nitrogen-containing hole transporting compound, such as a triarylamine compound (a compound having a triarylamine skeleton), a benzidine compound (a compound having a benzidine skeleton), or a hydrazone compound (a compound having a hydrazone skeleton), and having a structure conjugated with a nitrogen atom. As the charge transporting skeleton of the reactive charge transporting material, a triarylamine skeleton is preferred.

[0117] The reactive charge transport material may be used alone or in combination of two or more kinds.

[0118] As the reactive charge transport material, a compound represented by the following formula (A) is preferred from the viewpoint of excellent charge transport properties.

[0119] [ka]

[0120] In formula (A), Ar1 , Ar 2 , Ar 3 and Ar 4 each independently represents a substituted or unsubstituted aryl group, Ar 5 represents a substituted or unsubstituted aryl group or a substituted or unsubstituted arylene group, D represents a chain polymerizable group, an epoxy group, -OH, -OR [R represents an alkyl group], -NH2, -SH, -COOH, or -SiR a 3-n (OR b ) n [R a represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group, and R b represents a hydrogen atom, an alkyl group, or a trialkylsilyl group. n represents an integer of 1 or more and 3 or less.], n1, n2, n3, n4, and n5 each independently represent an integer of 0 or more and 2 or less, m represents 0 or 1, and the total number of Ds is 1 or more and 8 or less.

[0121] From the viewpoint of obtaining a protective layer with higher strength, the total number of Ds is preferably 2 or more, and more preferably 4 or more. From the viewpoint of reducing the proportion of unreacted reactive groups, the total number of Ds is preferably 7 or less, and more preferably 6 or less.

[0122] In formula (A), Ar 1 , Ar 2 , Ar 3 and Ar 4 each independently represents a substituted or unsubstituted aryl group. 1 , Ar 2 , Ar 3 and Ar 4 may be the same as or different from each other. Examples of the substituent in the substituted aryl group other than D include an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 10 carbon atoms.

[0123] -Ar in formula (A) 1 -(D) n1 , -Ar2 -(D) n2 , -Ar 3 -(D) n3 and -Ar 4 -(D) n4 are preferably each independently any one of the following formulas (1) to (7): In the following formulas (1) to (7), Ar 1 , Ar 2 , Ar 3 and Ar 4 Connect to each of the following - (D) n1 , -(D) n2 , -(D) n3 and -(D) n4 Comprehensively - (D) n It is expressed as:

[0124] [ka]

[0125] In formulas (1) to (7), D has the same meaning as "D" in formula (A), and n represents 1 or 2. In formula (1), R 1 represents a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, or a phenyl group substituted with an alkyl group having from 1 to 4 carbon atoms or an alkoxy group having from 1 to 4 carbon atoms. In equation (2), R 2 and R 3 each independently represents a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, a phenyl group substituted with an alkyl group having from 1 to 4 carbon atoms or an alkoxy group having from 1 to 4 carbon atoms, or a halogen atom. In equation (3), R 4 represents an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, a phenyl group substituted with an alkyl group having from 1 to 4 carbon atoms or an alkoxy group having from 1 to 4 carbon atoms, or a halogen atom, and a represents an integer of from 0 to 4. In formula (7), two Ar each independently represent a substituted or unsubstituted arylene group; Z represents a divalent organic linking group; and b represents 0 or 1.

[0126] Ar in formula (7) is preferably an arylene group represented by the following formula (8) or (9).

[0127] [ka]

[0128] In equation (8), R 5 represents an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, a phenyl group substituted with an alkyl group having from 1 to 4 carbon atoms or an alkoxy group having from 1 to 4 carbon atoms, or a halogen atom, and d represents an integer of from 0 to 4. In equation (9), R 6 and R 7 each independently represents an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, a phenyl group substituted with an alkyl group having from 1 to 4 carbon atoms or an alkoxy group having from 1 to 4 carbon atoms, or a halogen atom; and e and f each independently represent an integer of from 0 to 4.

[0129] Z in formula (7) is preferably any one of a divalent linking group represented by the following formula (10), a divalent linking group represented by formula (11), a divalent linking group represented by formula (12), a divalent linking group represented by formula (13), a divalent linking group represented by formula (14), a divalent linking group represented by formula (15), a divalent linking group represented by formula (16), and a divalent linking group represented by formula (17), or a combination thereof.

[0130] [ka]

[0131] In formula (10), p represents an integer of 1 or more and 10 or less. In formula (11), q represents an integer of 1 or more and 10 or less. In equation (16), R 8 represents an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, a phenyl group substituted with an alkyl group having from 1 to 4 carbon atoms or an alkoxy group having from 1 to 4 carbon atoms, or a halogen atom; s represents an integer of from 0 to 4; and W represents a divalent linking group. In equation (17), R 9 represents an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, a phenyl group substituted with an alkyl group having from 1 to 4 carbon atoms or an alkoxy group having from 1 to 4 carbon atoms, or a halogen atom; t represents an integer of from 0 to 4; and W represents a divalent linking group.

[0132] W in formula (16) and formula (17) is preferably any one of a divalent linking group represented by the following formula (18), a divalent linking group represented by formula (19), a divalent linking group represented by formula (20), a divalent linking group represented by formula (21), a divalent linking group represented by formula (22), a divalent linking group represented by formula (23), a divalent linking group represented by formula (24), a divalent linking group represented by formula (25), and a divalent linking group represented by formula (26).

[0133] [ka]

[0134] In formula (25), u represents an integer of 0 or more and 3 or less.

[0135] In formula (A), when m is 0, Ar 5 is a substituted or unsubstituted aryl group. 5 The aryl group in the formula (I) is Ar 1 The above-described aryl groups are preferred examples. In formula (A), when m is 1, Ar 5 is a substituted or unsubstituted arylene group. 5The arylene group according to the formula (I) is Ar 1 From the above aryl group explained as a preferred embodiment, -N(Ar 3 -(D) n3 )(Ar 4 -(D) n4 ) is substituted.

[0136] Examples of reactive charge transport materials include the following CTM(R1) to CTM(R4) and CTM(CP1) to CTM(CP4).

[0137] [ka]

[0138] [ka]

[0139] [ka]

[0140] [ka]

[0141] [ka]

[0142] [ka]

[0143] [ka]

[0144] The content of the reactive charge transport material is preferably 30% by mass to 100% by mass, more preferably 40% by mass to 100% by mass, and even more preferably 50% by mass to 100% by mass, based on the solid content of the composition for forming the protective layer (e.g., the coating liquid for forming the protective layer). By having the content of the reactive charge transport material in the above range, the protective layer can be made relatively thick, and therefore charge leakage is less likely to occur on the surface of the photoreceptor.

[0145] When a chain-polymerizable charge transport material is used as the reactive charge transport material, the content of the chain-polymerizable charge transport material is preferably 30% by mass to 100% by mass, more preferably 40% by mass to 100% by mass, and even more preferably 50% by mass to 100% by mass, based on the solid content of the composition for forming the protective layer (e.g., a coating liquid for forming the protective layer). By using a chain-polymerizable charge transport material in the above range, the protective layer can be made relatively thick, and therefore charge leakage is less likely to occur on the surface of the photoreceptor.

[0146] Examples of non-reactive charge transport materials include electron transport 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 non-reactive charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. One type of non-reactive charge transport material may be used alone, or two or more types may be used in combination.

[0147] An example of a non-reactive charge transport material is CTM(NR1) shown below.

[0148] [ka]

[0149] Examples of the reactive non-charge transporting material include a thermosetting resin, a curing agent, etc. One type of reactive non-charge transporting material may be used alone, or two or more types may be used in combination. Examples of the thermosetting resin include guanamine resin, melamine resin, phenol resin, urea resin, and alkyd resin. Examples of the curing agent include a compound having a guanamine structure (hereinafter also referred to as a "guanamine compound") and a compound having a melamine structure (hereinafter also referred to as a "melamine compound").

[0150] An example of the protective layer is a cured or crosslinked film containing a polymer or crosslinked product of a reactive charge transport material and at least one selected from the group consisting of a guanamine resin, a melamine resin, a guanamine compound, and a melamine compound. The protective layer, which is a cured or crosslinked film, is preferred from the viewpoint of superior abrasion resistance.

[0151] The protective layer may contain fluororesin particles. A protective layer containing fluororesin particles has unevenness formed on the outer peripheral surface of the protective layer, and is therefore more excellent in abrasion resistance.

[0152] Examples of fluororesins constituting the fluororesin particles include polytetrafluoroethylene (PTFE, also known as tetrafluoroethylene resin), perfluoroalkoxy fluororesin, polychlorotrifluoroethylene, polyvinylidene fluoride, polydichlorodifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer. From the viewpoint of the abrasion resistance and cleaning properties of the protective layer, the fluororesin constituting the fluororesin particles is preferably polytetrafluoroethylene or a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene. One type of fluororesin particle may be used alone, or two or more types may be used in combination.

[0153] The weight average molecular weight of the fluororesin constituting the fluororesin particles is preferably 3,000 or more and 5,000,000 or less.

[0154] The average primary particle size of the fluororesin particles is preferably 0.05 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 5 μm or less. The average primary particle size of fluororesin particles refers to the value measured using a laser diffraction / scattering particle size distribution measuring device at a refractive index of 1.35 in a dispersion liquid in which the fluororesin particles are dispersed.

[0155] The mass proportion of the fluororesin particles in the protective layer is preferably from 5% to 15% by mass, and more preferably from 7% to 12% by mass.

[0156] The protective layer is formed, for example, by preparing a coating solution for forming the protective layer containing the above-mentioned components and a solvent or dispersion medium, applying the coating solution for forming the protective layer on the photosensitive layer to form a coating film, and drying the coating film. If necessary, the coating film is subjected to a curing treatment such as heating.

[0157] Examples of solvents or dispersion media for preparing the coating liquid for forming the 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.

[0158] Examples of methods for applying the protective layer-forming coating solution onto the photosensitive layer include ordinary methods such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating.

[0159] The thickness of the protective layer is preferably from 2 μm to 10 μm, more preferably from 3 μm to 9 μm, and even more preferably from 4 μm to 8 μm. When the thickness of the protective layer is 10 μm or less, the charge generated in the charge generating layer by irradiation with static elimination light is less likely to accumulate in the protective layer, and as a result, fogging is less likely to occur in the image. From this viewpoint, the thickness of the protective layer is more preferably 9 μm or less, and even more preferably 8 μm or less. When the thickness of the protective layer is 2 μm or more, charge leakage is less likely to occur on the surface of the photoreceptor. From this viewpoint, the thickness of the protective layer is more preferably 3 μm or more, and even more preferably 4 μm or more.

[0160] <Image forming apparatus, process cartridge> The image forming apparatus according to the present embodiment includes an electrophotographic photosensitive member, a charging device that charges the surface of the electrophotographic photosensitive member, an electrostatic latent image forming device that forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member 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 a static eliminator that irradiates the surface of the electrophotographic photosensitive member with static elimination light to eliminate static after the toner image has been transferred to the surface of the recording medium.The electrophotographic photosensitive member according to the present embodiment is used as the electrophotographic photosensitive member.

[0161] The image forming apparatus according to the present embodiment is equipped with a static eliminator. Image forming apparatuses equipped with static eliminators tend to be prone to fogging during continuous image formation. By applying the electrophotographic photoreceptor according to the present embodiment to an image forming apparatus equipped with a static eliminator, the occurrence of fogging during continuous image formation can be suppressed.

[0162] The charging device provided in the image forming apparatus according to this embodiment may be a charging device of a type in which the charging member contacts the surface of the electrophotographic photosensitive member (contact type), or a charging device of a type in which the charging member does not contact the surface of the electrophotographic photosensitive member (non-contact type). The charging device provided in the image forming apparatus according to this embodiment may be any of the following: a charging device of a type that applies only a DC voltage to the charging member (DC charging type); a charging device of a type that applies only an AC voltage to the charging member (AC charging type); or a charging device of a type that applies a voltage that is a DC voltage superimposed on an AC voltage to the charging member (AC / DC charging type). Image forming apparatuses equipped with a contact-type DC charging device tend to easily cause fogging when continuously forming images. By applying the electrophotographic photoreceptor according to this embodiment to an image forming apparatus equipped with a contact-type DC charging device, the occurrence of fogging when continuously forming images can be suppressed.

[0163] The image forming apparatus according to the present embodiment may be any known image forming apparatus, such as an apparatus equipped with 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 equipped with a cleaning device that cleans the surface of the electrophotographic photosensitive member before charging after the transfer of the toner image; or an apparatus equipped with an electrophotographic photosensitive member heating member that increases the temperature of the electrophotographic photosensitive member and reduces the relative temperature thereof.

[0164] 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 that performs primary transfer of the toner image formed on the surface of the electrophotographic photosensitive body onto the surface of the intermediate transfer body, and a secondary transfer device that performs secondarily transfer of the toner image transferred onto the surface of the intermediate transfer body onto the surface of the recording medium.

[0165] The image forming apparatus according to this 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).

[0166] 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. In addition to the electrophotographic photosensitive member, the process cartridge may include, for example, 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.

[0167] 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. The main parts shown in the drawings will be described, and the description of the rest will be omitted.

[0168] FIG. 2 is a schematic diagram showing an example of the configuration of an image forming apparatus according to this embodiment. As shown in FIG. 2, the image forming apparatus 100 according to this embodiment includes a process cartridge 300 having an electrophotographic photosensitive member 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 member 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photosensitive member 7 through the opening of the process cartridge 300, and the transfer device 40 is disposed at a position facing the electrophotographic photosensitive member 7 via the intermediate transfer member 50, with a portion of the intermediate transfer member 50 being in contact with the electrophotographic photosensitive member 7. Although not shown, the image forming apparatus 100 also includes a secondary transfer device that transfers the toner image transferred onto the intermediate transfer member 50 onto a recording medium (e.g., paper). The intermediate transfer member 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown) correspond to examples of transfer devices.

[0169] 2 integrally supports an electrophotographic photosensitive member 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) 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 photosensitive member 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.

[0170] FIG. 2 shows an example of an image forming apparatus equipped with a fibrous member 132 (in the form of a roll) that supplies the lubricant 14 to the surface of the electrophotographic photosensitive member 7, but the fibrous member 132 may be disposed as needed.

[0171] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0172] -Charging device- The charging device 8 may be a contact type charger using, for example, a conductive or semi-conductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. Publicly known chargers such as a non-contact type roller charger, a scorotron charger or a corotron charger that utilizes corona discharge, etc. may also be used. The charging device 8 may be either a contact type charging device or a non-contact type charging device. The charging device 8 may be either a DC charging type charging device, an AC charging type charging device, or an AC / DC charging type charging device. An example embodiment of the charging device 8 is a contact type and a DC charging type charging device.

[0173] -Exposure equipment- The exposure device 9 may be, for example, an optical system that exposes the surface of the electrophotographic photosensitive member 7 to 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 photosensitive member. The wavelength of semiconductor lasers is mainly near-infrared, with an oscillation wavelength around 780 nm. However, this wavelength is not limited to this, and lasers with an oscillation wavelength in the 600 nm range or blue lasers with an oscillation wavelength of 400 nm to 450 nm may also be used. Furthermore, for color image formation, a surface-emitting laser light source capable of outputting multiple beams is also effective.

[0174] -Developing device- The developing device 11 may be, for example, a general developing device that develops by contact or non-contact application of a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected depending on the purpose. For example, it may be a known developing device that has a function of applying a one-component developer or a two-component developer to the electrophotographic photosensitive member 7 using a brush, roller, or the like. Among these, a developing roller that holds a developer on its surface is preferred.

[0175] The developer used in the developing device 11 may be a one-component developer containing only toner, or a two-component developer containing toner and a carrier. The developer may be magnetic or non-magnetic. Known developers are used.

[0176] -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 cleaning type may also be used.

[0177] -Static eliminator- The static eliminator 15 irradiates the surface of the electrophotographic photosensitive member 7 with static elimination light to remove residual potential on the electrophotographic photosensitive member 7. The static eliminator 15 is a light irradiator that irradiates the entire area of ​​the electrophotographic photosensitive member 7 in the rotational axis direction with light, and examples of the static eliminator include a halogen lamp, a tungsten lamp, and an LED lamp. The wavelength of the static eliminator light is, for example, 600 nm or more and 700 nm or less, and the light amount of the static eliminator light is, for example, 5 mJ / m 2 More than 100mJ / m 2 The following is the result. After the toner image is transferred to the intermediate transfer body 50, the electrophotographic photosensitive member 7 has residual toner and other adhering matter on its surface removed by the cleaning device 13, and the residual charge on the surface is removed by irradiating it with discharging light by the discharging device 15. Although FIG. 2 shows a configuration in which the static eliminator 15 is disposed downstream of the cleaning device 13, the static eliminator 15 may be disposed upstream of the cleaning device 13.

[0178] -Transfer device- Examples of the transfer device 40 include a contact type transfer charger using a belt, roller, film, rubber blade, etc., and a known transfer charger such as a scorotron transfer charger or corotron transfer charger that utilizes corona discharge.

[0179] -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.

[0180] FIG. 3 is a schematic diagram showing another example of the configuration of the image forming apparatus according to the present embodiment. 3 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 member 50, and one electrophotographic photosensitive member is used per color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem-type apparatus. [Example]

[0181] 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, treatment, measurement, etc. were carried out at room temperature (25°C ± 3°C).

[0182] <Photoreceptor manufacturing> [Example 1] - Formation of undercoat layer - As a conductive substrate, an aluminum cylindrical tube having an outer diameter of 30 mm, a length of 365 mm, and a wall thickness of 1 mm was prepared.

[0183] Zinc oxide (average particle size 70 nm, specific surface area 15 m 2100 parts of a silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, trade name: KBM603, manufactured by Teika Corporation) was mixed with 500 parts of toluene by stirring, and 1.3 parts of a silane coupling agent (N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, trade name: KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) 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.

[0184] 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 under reduced pressure and dried under reduced pressure at 60° C. to obtain zinc oxide with alizarin added thereto.

[0185] A solution of 60 parts alizarin-modified zinc oxide, 13.5 parts curing agent (blocked isocyanate, trade name: Sumidur 3175, Sumitomo Bayer Urethane Co., Ltd.), and 15 parts butyral resin (trade name: S-LEC BM-1, Sekisui Chemical Co., Ltd.) dissolved in 68 parts methyl ethyl ketone was mixed with 5 parts methyl ethyl ketone and dispersed in a sand mill using 1 mm diameter glass beads for 2 hours to obtain a dispersion. To the dispersion, 0.005 parts dioctyltin dilaurate as a catalyst and 4 parts silicone resin particles (trade name: Tospearl 145, Momentive Performance Materials Japan, LLC) were added to obtain a coating solution for forming an undercoat layer. The coating solution for forming the undercoat layer was applied to the outer surface of a conductive substrate by dip coating and dried and cured at 170 °C for 40 minutes to form an undercoat layer with an average thickness of 25 μm.

[0186] - Formation of charge generation layer - A mixture consisting of 15 parts of hydroxygallium phthalocyanine (CGL) as a charge-generating material (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), 10 parts of vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using 1 mm diameter glass beads 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 solution for forming a charge-generating layer. The coating solution for forming the charge-generating layer was dip-coated onto the undercoat layer and dried at room temperature (25°C ± 3°C) to form a charge-generating layer with an average thickness of 0.18 μm.

[0187] - Formation of charge transport layer - Binder resin: Polycarbonate resin (PC1) (viscosity average molecular weight 50,000) 50 parts ·Charge transport material: CTM (1) 50 parts Solvent: 200 parts tetrahydrofuran Solvent: 50 parts toluene The above materials were mixed to obtain a coating liquid for forming a charge transport layer. The coating liquid for forming a charge transport layer was dip-coated onto the charge generation layer and dried at 145°C for 30 minutes to form a charge transport layer with a thickness of 11.0 µm. The chemical structures of polycarbonate resin (PC1) and CTM (1) are shown below. The numerical values ​​in the structural formula of polycarbonate resin (PC1) are molar ratios.

[0188] [ka]

[0189] [ka]

[0190] - Formation of a protective layer - Reactive charge transport material: CTM(R1) 70 parts Reactive charge transport material: CTM(R2) 15 parts Reactive non-charge transport material (thermosetting resin): benzoguanamine resin (trade name: Nikalac BL-60, Sanwa Chemical Co., Ltd.) 4.4 parts Curing catalyst: NACURE 5225 (King Industries) 0.1 parts Solvent: 220 parts 2-propanol The above materials were mixed to obtain a coating solution for forming a protective layer. The coating solution for forming a protective layer was dip-coated onto the charge transport layer and dried at room temperature (25°C ± 3°C) for 30 minutes. The protective layer was then placed in a heating furnace and heated at 155°C for 20 minutes under a nitrogen stream with an oxygen concentration of 110 ppm to harden the protective layer, forming a protective layer with a thickness of 7.0 μm. The chemical structures of CTM(R1) and CTM(R2) are shown below.

[0191] [ka]

[0192] [Examples 2 to 7, Comparative Examples 1 and 2] A photoreceptor was produced in the same manner as in Example 1, except that the thickness of the charge transport layer and the thickness of the protective layer were changed as shown in Table 1.

[0193] [Example 11] A photoreceptor was produced in the same manner as in Example 1, except that the formation of the charge transport layer and the protective layer was changed as follows.

[0194] - Formation of charge transport layer - Binder resin: Polyarylate resin (PA1) (weight average molecular weight 80,000) 50 parts ·Charge transport material: CTM (2) 50 parts Solvent: 200 parts tetrahydrofuran Solvent: 50 parts toluene The above materials were mixed to obtain a coating liquid for forming a charge transport layer. The coating liquid for forming a charge transport layer was dip-coated onto the charge generation layer and dried at 145°C for 30 minutes to form a charge transport layer with a thickness of 11.0 µm. The chemical structures of polyarylate resin (PA1) and CTM (2) are shown below. The numerical values ​​in the structural formula of polyarylate resin (PA1) are molar ratios.

[0195] [ka]

[0196] [ka]

[0197] - Formation of a protective layer - Reactive charge transport material: CTM(R1) 70 parts Reactive charge transport material: CTM(R2) 15 parts Reactive non-charge transport material (thermosetting resin): benzoguanamine resin (trade name: Nikalac BL-60, Sanwa Chemical Co., Ltd.) 4.4 parts Curing catalyst: NACURE 5225 (King Industries) 0.1 parts Solvent: 220 parts 2-propanol The above materials were mixed to obtain a coating solution for forming a protective layer. The coating solution for forming a protective layer was dip-coated onto the charge transport layer and dried at room temperature (25°C ± 3°C) for 30 minutes. The protective layer was then placed in a heating furnace and heated at 155°C for 20 minutes under a nitrogen stream with an oxygen concentration of 110 ppm to harden the protective layer, forming a protective layer with a thickness of 7.0 μm.

[0198] [Examples 12 to 17, Comparative Examples 11 to 12] A photoreceptor was produced in the same manner as in Example 11, except that the thickness of the charge transport layer and the thickness of the protective layer were changed as shown in Table 1.

[0199] <Performance evaluation> A DocuCentre-V C2263 (FUJIFILM Business Innovation Co., Ltd.) was prepared as an image forming apparatus equipped with a contact-type DC charging device in which the charging member is a charging roll, and a static eliminator that eliminates static by irradiating light. The static eliminator has a static eliminator light source: an LED lamp, a static eliminator light wavelength: 600 nm to 700 nm, and a static eliminator light intensity: 50 mJ / m 2 The photoreceptor of each example or comparative example was installed in an image forming apparatus.

[0200] [Amount of decrease in surface potential] The following operations were carried out consecutively in an environment at a temperature of 28°C and a relative humidity of 85%. The potential probe of a surface potential meter (Trek Japan, Model 347) was placed at the developer position of the image forming device described above. Five sheets of A4-sized plain paper were passed through the device, and the initial surface potential (V) was measured. The potential probe was removed, and 1,000 sheets of A4-sized plain paper were passed through the device. The potential probe was then placed back at the developer position, and five sheets of A4-sized plain paper were passed through the device, and the surface potential (V) after the continuous paper feed was measured. The surface potential (V) after the continuous paper feed was calculated by subtracting the surface potential (V) after the continuous paper feed from the initial surface potential (V). The results are shown in Table 1. A surface potential drop of less than 25 V is within the acceptable range.

[0201] [Cover] Using the image forming apparatus described above, 1,000 full-page solid black images were printed onto A4-sized plain paper in an environment of 22°C temperature and 55% relative humidity. Five sheets of A4-sized plain paper were then fed through, and the five sheets were visually observed and classified as follows: A: There is no overlap. B: Fog occurred, but was within the acceptable range. C: Obvious fogging occurred, outside the acceptable range.

[0202] [Charge leak] The following operations were carried out consecutively in an environment at a temperature of 22°C and a relative humidity of 55%. A voltage of 2 kV was applied to the charging roll of the image forming apparatus described above, and after 30 minutes had passed, discharge was applied to one point on the surface of the photosensitive member, and the occurrence of black spots due to pinholes was confirmed. A: There are no black spots (leaks). B: Minute black spots (leakage) were observed, but were within the acceptable range. C: Obvious black spots (leakage) occurred. Outside the allowable range.

[0203] [Table 1]

[0204] The electrophotographic photoreceptor, process cartridge, and image forming apparatus of the present disclosure include the following aspects.

[0205] (((1))) a conductive substrate; a charge generating layer disposed on the conductive substrate; a charge transport layer disposed on the charge generating layer; a protective layer disposed on the charge transport layer, a ratio L / ε of a total thickness L (μm) of the charge transport layer and the protective layer to a dielectric constant ε (F / m) of the entire charge transport layer and the protective layer in the thickness direction is 3 or more and 6 or less; Electrophotographic photoreceptor. (((2))) The electrophotographic photoreceptor according to (((1))), wherein the value of the ratio L / ε is 4.5 or more and 5.5 or less. (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), wherein the protective layer is a cured or crosslinked film of a composition containing a reactive charge transport material. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the total thickness L is 10 μm or more and 20 μm or less. (((5))) The electrophotographic photoreceptor according to any one of (((1))) to (((4))), wherein the ratio L2 / L1 of the thickness L1 of the charge transport layer to the thickness L2 of the protective layer is 0.1 or more and 1 or less. (((6))) a charging device for charging a surface of an electrophotographic photosensitive member, the charging device having a charging member in contact with the electrophotographic photosensitive member and applying only a DC voltage to the charging member; a static elimination device that irradiates a static elimination light onto the surface of the electrophotographic photosensitive member to eliminate static electricity after the toner image is transferred onto the surface of the recording medium; For use in an image forming apparatus having The electrophotographic photoreceptor according to any one of (((1))) to (((5))). (((7))) An electrophotographic photoreceptor according to any one of (((1))) to (((5))), A process cartridge that is detachably attached to an image forming apparatus. (((8))) a static elimination device that irradiates the surface of the electrophotographic photosensitive member with static elimination light to eliminate static electricity after the toner image is transferred to the surface of the recording medium; The process cartridge according to (((7))). (((9))) a charging device for charging the surface of the electrophotographic photosensitive member, the charging device having a charging member in contact with the electrophotographic photosensitive member and applying a DC voltage to the charging member; The process cartridge according to (((7))) or (((8))). (((10))) an electrophotographic photoreceptor according to any one of (((1))) to (((5))); a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; a static elimination device that irradiates a static elimination light onto the surface of the electrophotographic photosensitive member to eliminate static electricity after the toner image is transferred onto the surface of the recording medium; An image forming apparatus comprising: (((11))) the charging device has a charging member that contacts the electrophotographic photosensitive member and applies a DC voltage to the charging member; The image forming apparatus according to (((10))).

[0206] According to (((1))), (((3))), or (((6))), an electrophotographic photosensitive member is provided which is less likely to cause charge leakage than an electrophotographic photosensitive member having a ratio L / ε value of less than 3, and an electrophotographic photosensitive member is provided which is less likely to cause fogging during continuous image formation than an electrophotographic photosensitive member having a ratio L / ε value of more than 6. According to (((2))), an electrophotographic photosensitive member is provided which is less likely to cause charge leakage than an electrophotographic photosensitive member having a ratio L / ε value of less than 4.5, and an electrophotographic photosensitive member is provided which is less likely to cause fogging during continuous image formation than an electrophotographic photosensitive member having a ratio L / ε value of more than 5.5. According to (((4))), an electrophotographic photoreceptor is provided which is less likely to cause charge leakage than an electrophotographic photoreceptor having a total thickness L of the charge transport layer and the protective layer of less than 10 μm, and an electrophotographic photoreceptor is provided which is less likely to cause fogging during continuous image formation than an electrophotographic photoreceptor having a total thickness L of the charge transport layer and the protective layer of more than 20 μm. According to (((5))), an electrophotographic photoreceptor is provided which is less susceptible to charge leakage than an electrophotographic photoreceptor in which the ratio L2 / L1 of the layer thickness L1 of the charge transport layer to the layer thickness L2 of the protective layer is less than 0.1. According to (((7))), (((8))) or (((9))), a process cartridge is provided which is less likely to cause charge leakage than a process cartridge in which the value of the ratio L / ε of the electrophotographic photosensitive member is less than 3, and a process cartridge is provided which is less likely to cause fogging during continuous image formation than a process cartridge in which the value of the ratio L / ε of the electrophotographic photosensitive member is more than 6. According to (((10))) or (((11))), an image forming apparatus is provided which is less likely to cause charge leakage than an image forming apparatus in which the value of the ratio L / ε of the electrophotographic photosensitive member is less than 3, and an image forming apparatus is provided which is less likely to cause fogging during continuous image formation than an image forming apparatus in which the value of the ratio L / ε of the electrophotographic photosensitive member is more than 6. [Explanation of symbols]

[0207] 1 conductive substrate, 2 subbing layer, 3 charge generation layer, 4 charge transport layer, 5 photosensitive layer, 6 protective layer, 10A photoreceptor

[0208] 7 electrophotographic photosensitive member, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 15 static eliminator, 40 transfer device, 50 intermediate transfer body, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll), 300 process cartridge

Claims

1. a conductive substrate; a charge generating layer disposed on the conductive substrate; a charge transport layer disposed on the charge generating layer; a protective layer disposed on the charge transport layer, a ratio L / ε of a total thickness L (μm) of the charge transport layer and the protective layer to a dielectric constant ε (F / m) of the entire charge transport layer and the protective layer in the thickness direction is 3 or more and 6 or less; Electrophotographic photoreceptor.

2. 2. The electrophotographic photoreceptor according to claim 1, wherein the value of the ratio L / ε is 4.5 or more and 5.5 or less.

3. 2. The electrophotographic photoreceptor according to claim 1, wherein the protective layer is a cured or crosslinked film of a composition containing a reactive charge transport material.

4. 2. The electrophotographic photoreceptor according to claim 1, wherein the total thickness L is 10 [mu]m or more and 20 [mu]m or less.

5. 2. The electrophotographic photoreceptor according to claim 1, wherein a ratio L2 / L1 of a thickness L1 of said charge transport layer to a thickness L2 of said protective layer is 0.1 or more and 1 or less.

6. a charging device for charging a surface of an electrophotographic photosensitive member, the charging device having a charging member in contact with the electrophotographic photosensitive member and applying only a DC voltage to the charging member; a static elimination device that irradiates a static elimination light onto the surface of the electrophotographic photosensitive member to eliminate static electricity after the toner image is transferred onto the surface of the recording medium; For use in an image forming apparatus having The electrophotographic photoreceptor according to any one of claims 1 to 5.

7. The electrophotographic photoreceptor according to any one of claims 1 to 5 is provided, A process cartridge that is detachably attached to an image forming apparatus.

8. a static elimination device that irradiates the surface of the electrophotographic photosensitive member with static elimination light to eliminate static electricity after the toner image is transferred to the surface of the recording medium; The process cartridge according to claim 7 .

9. a charging device for charging the surface of the electrophotographic photosensitive member, the charging device having a charging member in contact with the electrophotographic photosensitive member and applying only a DC voltage to the charging member; The process cartridge according to claim 8.

10. The electrophotographic photoreceptor according to any one of claims 1 to 5, a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; a transfer device that transfers the toner image onto a surface of a recording medium; a static elimination device that irradiates a static elimination light onto the surface of the electrophotographic photosensitive member to eliminate static electricity after the toner image is transferred onto the surface of the recording medium; An image forming apparatus comprising:

11. the charging device has a charging member that contacts the electrophotographic photosensitive member, and applies only a DC voltage to the charging member; The image forming apparatus according to claim 10.

Images