Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that prevents positive ghost.SOLUTION: An electrophotographic photoreceptor has: a conductive substrate; an undercoat layer provided on the conductive substrate and including zinc oxide particles and a binder resin; a charge generating layer provided on the undercoat layer and including a titanium-containing organic pigment and a binder resin; and a charge transport layer provided on the charge generating layer. The film thickness of the undercoat layer is 15.0 μm or more and 30.0 μm or less. When the film thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, in a region within ±500 nm in a film thickness direction from an interface between the undercoat layer and the charge generating layer, the ratio of Ti concentration and the ratio of Zn concentration to the total of Ti concentration and Zn concentration are both 30% or more and 70% or less. When the film thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, in the region within ±500 nm in the film thickness direction from the interface between the undercoat layer and the charge generating layer, the ratio of Ti concentration and the ratio of Zn concentration to the total of Ti concentration and Zn concentration are both 20% or more and 80% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] An image is formed by electrophotography, for example, by charging the surface of a photoreceptor, forming an electrostatic image on the surface of the photoreceptor in accordance with image information, developing the electrostatic image with a developer containing toner to form a toner image, and transferring and fixing the toner image to the surface of a recording medium.

[0003] Patent Document 1 discloses "an electrophotographic photoreceptor characterized by comprising a support and a photosensitive layer containing oxytitanium phthalocyanine hydrate crystals provided on the support." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 4-189873 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an electrophotographic photoreceptor in which positive ghosts are suppressed compared to when the thickness of the undercoat layer is less than 15.0 μm or exceeds 30.0 μm. An object of the present invention is to provide an electrophotographic photoreceptor in which, when the thickness of an undercoat layer is 22.0 μm or more and 30.0 μm or less, positive ghosts are suppressed compared to when the Ti concentration ratio and the Zn concentration ratio described below are less than 30% or more than 70%, respectively. An object of the present invention is to provide an electrophotographic photoreceptor in which, when the thickness of an undercoat layer is 15.0 μm or more and less than 22.0 μm, positive ghosts are suppressed compared to when the Ti concentration ratio and the Zn concentration ratio are less than 20% or more than 80%, respectively. [Means for solving the problem]

[0006] Means for solving the above problems include the following aspects. <1> a conductive substrate; an undercoat layer provided on the conductive substrate and containing zinc oxide particles and a binder resin; a charge generating layer provided on the undercoat layer and including a titanium-containing organic pigment and a binder resin; a charge transport layer disposed on the charge generating layer; and the undercoat layer has a thickness of 15.0 μm or more and 30.0 μm or less, when the thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, in a region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer, the ratio of the Ti concentration and the Zn concentration to the total concentration of Ti and Zn are each 30% or more and 70% or less, When the thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, the ratio of the Ti concentration and the Zn concentration to the total concentration of the Ti concentration and the Zn concentration in a region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer is 20% or more and 80% or less, respectively. <2> The titanium-containing organic pigment is titanyl phthalocyanine. <1> The electrophotographic photoreceptor according to claim 1. <3> the undercoat layer has a thickness of 15.0 μm or more and 25.0 μm or less, In a region within ±500 nm in the film thickness direction from the interface between the undercoat layer and the charge generating layer, the ratio of the Ti concentration to the total Ti concentration and the Zn concentration is 40% or more and 60% or less. <1> or <2> The electrophotographic photoreceptor according to claim 1. <4> <1> ~ <3> The electrophotographic photoreceptor according to any one of the preceding claims is provided, A process cartridge that is detachably attached to an image forming apparatus. <5> <1> ~ <3> the electrophotographic photoreceptor according to any one of the above items; a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic image forming device for forming an electrostatic image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic 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; An image forming apparatus comprising: [Effects of the Invention]

[0007] <1> , or <2> According to the invention, an electrophotographic photoreceptor is provided in which positive ghosts are suppressed compared to when the thickness of the undercoat layer is less than 15.0 μm or exceeds 30.0 μm. <1> , or <2> According to the invention, when the thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, an electrophotographic photoreceptor is provided in which positive ghosts are suppressed compared to when the Ti concentration ratio and the Zn concentration ratio are each less than 30% or more than 70%. <1> , or <2> According to the invention, when the thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, an electrophotographic photoreceptor is provided in which positive ghosts are suppressed compared to when the Ti concentration ratio and the Zn concentration ratio are less than 20% or more than 80%, respectively.

[0008] <3> According to the invention, an electrophotographic photoreceptor is provided in which positive ghosts are suppressed compared to when the thickness of the undercoat layer is less than 15.0 μm or exceeds 25.0 μm, or when the Ti concentration ratio and the Zn concentration ratio are each less than 40% or exceeds 60%.

[0009] <4> , or <5> According to the invention, there is provided a process cartridge or an image forming apparatus in which, when the thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, positive ghosts are suppressed compared to when an electrophotographic photosensitive member in which the Ti concentration ratio and the Zn concentration ratio are each less than 30% or more than 70%, respectively, is used. <4> , or <5> According to the invention, there is provided a process cartridge or an image forming apparatus in which, when the thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, positive ghosts are suppressed compared to when an electrophotographic photosensitive member in which the Ti concentration ratio and the Zn concentration ratio are each less than 20% or more than 80%, respectively, is used. [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] Hereinafter, an embodiment of the present invention will be described in detail. These descriptions and examples are for illustrating the present invention, but are not intended to limit the present invention.

[0012] In this specification, 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 present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0013] In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0014] When embodiments are described in this specification 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.

[0015] In this specification, each component may contain multiple corresponding substances. When referring to the amount of each component in a composition in this specification, 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.

[0016] In this specification, the "electrophotographic photoreceptor" is also referred to as the "photoreceptor."

[0017] <Electrophotographic photoreceptor> The photoreceptor according to this embodiment includes a conductive substrate, an undercoat layer provided on the conductive substrate and containing zinc oxide particles and a binder resin, a charge generation layer provided on the undercoat layer and containing a titanium-containing organic pigment and a binder resin, and a charge transport layer provided on the charge generation layer. When the thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, the ratio of the Ti concentration and the Zn concentration to the total concentration of Ti and Zn in the region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer is 30% or more and 70% or less, respectively. When the thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, the ratio of the Ti concentration and the Zn concentration to the total concentration of Ti and Zn in the region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer is 20% or more and 80% or less, respectively.

[0018] The photoreceptor according to this embodiment has the above-described structure, and the occurrence of positive ghost images is suppressed. The reason for this is presumed to be as follows.

[0019] A photoreceptor having a conductive substrate, an undercoat layer containing zinc oxide particles and a binder resin, a charge generation layer containing a titanium-containing organic pigment and a binder resin, and a charge transport layer has a large energy gap at the interface between the undercoat layer and the charge generation layer. This inhibits charge migration and injection, making dark decay more likely to occur. When dark decay occurs, the surface potential of the electrophotographic photoreceptor in the image area of ​​the previous image formation cycle is partially reduced in the next image formation cycle, resulting in potential fluctuations. This results in a phenomenon known as positive ghosting, in which the area with the partially reduced surface potential (i.e., the image area of ​​the previous image formation cycle) appears darker in the next image formation cycle.

[0020] In contrast, in the photoreceptor according to this embodiment, the Ti concentration ratio and Zn concentration ratio in the region within ±500 nm in the film thickness direction from the interface between the undercoat layer and the charge generation layer are within the above ranges. The Ti and Zn concentrations approach uniformity near the interface between the undercoat layer and the charge generation layer. In other words, the dispersibility of the zinc oxide particles and the titanium-containing organic pigment approaches uniformity. This reduces the energy gap at the interface between the undercoat layer and the charge generation layer. This suppresses the inhibition of charge migration and injection, making dark decay less likely to occur. As a result, potential fluctuations are less likely to occur, and positive ghosts are suppressed. Furthermore, when the thickness of the undercoat layer is reduced, the film resistance of the undercoat layer is reduced. Therefore, when the thickness of the undercoat layer is thin, even if the concentration ratio of Ti to Zn is high, that is, even if the dispersibility of the zinc oxide particles and the titanium-containing organic pigment is low, the inhibition of charge migration and injection is suppressed and dark decay is less likely to occur compared to when the thickness of the undercoat layer is thick. As a result, potential fluctuation is less likely to occur and positive ghosts are suppressed.

[0021] From the above, it is presumed that the positive ghost is suppressed in the photoreceptor according to this embodiment. Positive ghost images tend to occur in image forming apparatuses that are equipped with a DC charging device but do not have a static eliminator that neutralizes the photoconductor after toner transfer and before charging the photoconductor. However, the photoconductor according to this embodiment suppresses positive ghost images even when applied to such image forming apparatuses.

[0022] The photoreceptor according to this embodiment will be described in detail below.

[0023] Fig. 1 is a partial cross-sectional view showing an example of the layer structure of a photoreceptor according to this embodiment. Photoreceptor 10A shown in Fig. 1 has a laminated photosensitive layer. Photoreceptor 10A 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 (a so-called function-separated photosensitive layer). The protective layer 6 may or may not be present.

[0024] Hereinafter, each layer of the photosensitive layer according to this embodiment will be described in detail, with the reference numerals omitted.

[0025] (Thickness of undercoat layer) The thickness of the undercoat layer is from 15.0 μm to 30.0 μm, and preferably from 15.0 μm to 25.0 μm. If the thickness of the undercoat layer is less than 15.0 μm, current leakage occurs during charging and current leakage occurs due to piercing by needle-like foreign matter, and the photoreceptor will not function properly. If the thickness of the undercoat layer exceeds 30.0 μm, the resistance increases and the potential retention decreases, resulting in the occurrence of positive ghost images. Therefore, the thickness of the undercoat layer is set within the above range.

[0026] The thickness of the undercoat layer was measured as follows. First, a sample is obtained by cutting out the central portion of the photoreceptor in the axial direction. Next, an observation image of the cross section of the sample is obtained using a scanning electron microscope (SEM). Next, in the observation image, the film thickness of the undercoat layer and the charge transport layer are measured at 10 points each, and the arithmetic mean value is calculated.

[0027] (Ratio of Ti concentration and Zn concentration at the interface between the undercoat layer and the charge generating layer) When the thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, the proportion of the Ti concentration and the proportion of the Zn concentration relative to the total concentration of Ti and Zn in the region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer are each 30% or more and 70% or less, and preferably 40% or more and 60% or less. That is, the concentration ratio of Ti to Zn (T1 / Zn) in this region is 30 / 70 or more and 70 / 30, and preferably 40 / 60 or more and 60 / 40 or less.

[0028] When the thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, the proportion of the Ti concentration and the proportion of the Zn concentration relative to the total concentration of Ti and Zn in the region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer are each 20% or more and 80% or less, preferably 30% or more and 70% or less, and more preferably 40% or more and 60% or less. That is, the concentration ratio of Ti to Zn (T1 / Zn) in this region is 20 / 80 or more and 80 / 20, preferably 30 / 70 or more and 70 / 30, and more preferably 40 / 60 or more and 60 / 40 or less.

[0029] If the Ti concentration ratio and the Zn concentration ratio are outside the above ranges, the dispersibility of the zinc oxide particles and the titanium-containing organic pigment will be low. This will increase the energy gap at the interface between the undercoat layer and the charge generating layer. This will tend to hinder charge transfer and injection, resulting in dark decay. This will result in potential fluctuations and the generation of positive ghost images.

[0030] In particular, from the viewpoint of suppressing positive ghosts, it is preferable that the thickness of the undercoat layer is 15.0 μm or more and 25.0 μm or less, and that the ratio of the Ti concentration and the Zn concentration to the total concentration of the Ti concentration and the Zn concentration in the region within ±500 nm in the film thickness direction from the interface between the undercoat layer and the charge generating layer is 40% or more and 60% or less, respectively.

[0031] One method for adjusting the Ti concentration ratio and Zn concentration ratio within the above ranges is to slow the circulating flow rate of the coating liquid when forming the undercoat layer by dip coating with a circulating coating liquid. It is believed that slowing the circulating flow rate of the coating liquid changes the surface properties of the undercoat layer. As a result, the contact area between the undercoat layer and the charge transport layer increases, and they tend to mix more uniformly, which tends to cause the ratio of Ti concentration to Zn concentration to approach 50%:50%. Increasing the circulating flow rate tends to increase the Zn concentration ratio, while slowing the circulating flow rate tends to increase the Zn concentration ratio. Based on this trend, it is believed that the Ti concentration ratio and Zn concentration ratio can be adjusted to fall within the above ranges.

[0032] The method for measuring the Ti concentration ratio and the Zn concentration ratio is as follows. First, a sample is taken from the photoreceptor to be measured. The surface of the sample is polished to remove as much of the charge transport layer as possible. Next, the surface of the charge generating layer of the sample is subjected to elemental analysis by X-ray photoelectron spectroscopy (XPS) under the following analytical conditions, and the Ti concentration (atomic %) and Zn concentration (atomic %) are determined from the peak intensities of Ti and Zn. The elements to be analyzed are Ti, Zn, C, O, N, and Si. However, measurements of both the Ti concentration and the Zn concentration are started after ion etching has been carried out until a Ti peak is detected. -XPS analysis conditions- Device name: JPS-9030 (JEOL XPS) X-ray type: MgKα Accelerating voltage: 10 kV Emission current: 10mA Measurement step: 0.1 eV Pass energy: 10 eV Dwell Time: 100-500ms

[0033] The above elemental analysis operation is carried out under the following conditions while performing ion etching from the surface of the charge generating layer to the undercoat layer until the Zn concentration is saturated. -Etching conditions- Etching gas: Argon Ion gun acceleration voltage: 500V Etching time: The first etching of the charge generating layer surface at the start of measurement is 40 seconds, and subsequent etchings are 60 seconds.

[0034] By carrying out the above operations, the Ti concentration and Zn concentration profiles in the film thickness direction of the undercoat layer and the charge generating layer are obtained. From the Ti and Zn concentration profiles, a region within ±500 nm in the film thickness direction from the interface between the undercoat layer and the charge generating layer is identified, and the cumulative values ​​of the Ti and Zn concentrations within the identified region are calculated. Here, the interface between the undercoat layer and the charge generating layer is a location where the Zn concentration is half of the saturated value. Then, the Ti concentration ratio and the Zn concentration ratio are calculated using the following formula. Formula: Ti concentration ratio = cumulative Ti concentration / (cumulative Ti concentration + cumulative Zn concentration) x 100 Formula: Zn concentration ratio = cumulative Zn concentration / (cumulative Ti concentration + cumulative Zn concentration) x 100

[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 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] (subbing layer) The undercoat layer is a layer containing zinc oxide particles and a binder resin. The volume average particle size of the zinc oxide particles is, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less). The volume average particle size of silica particles is determined by separating zinc oxide particles from the layer, observing 100 primary particles of the resulting zinc oxide particles using a scanning electron microscope (SEM) at 40,000x magnification, measuring the longest and shortest diameters of each particle using image analysis of the primary particles, and then calculating the equivalent circle diameter from the intermediate value. The 50% diameter (D50v) of the volume-based cumulative frequency of the obtained equivalent circle diameters is calculated. The obtained 50% diameter (D50v) is the volume average particle size of the zinc oxide particles.

[0044] The specific surface area of ​​zinc oxide particles by the BET method is, for example, 10 m 2 / g or more is preferable.

[0045] The content of the zinc oxide particles is, for example, preferably 10% by mass or more and 80% by mass or less, and more preferably 40% by mass or more and 80% by mass or less, relative to the binder resin.

[0046] Other inorganic particles may be used in combination with zinc oxide particles, provided that the proportion of zinc oxide particles in the total inorganic particles is preferably 90% by mass or more, and more preferably 95% by mass or more. Other inorganic particles include, for example, particles with a powder resistance (volume resistivity) of 10 2 Ω cm or more 10 11 Examples include inorganic particles with a particle size of Ω·cm or less. Examples of other inorganic particles include metal oxide particles such as tin oxide particles, titanium oxide particles, and zirconium oxide particles.

[0047] The inorganic particles including zinc oxide 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 electron-transporting substances such as compounds having an anthraquinone structure; 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, purpurin, or a derivative thereof.

[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 surfaces 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 is a method in which inorganic particles are dispersed in a solvent using, for example, a stirrer, ultrasonic disperser, sand mill, attritor, or ball mill, while an electron-accepting compound is added, followed by stirring or dispersion, 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 in which the inorganic particles are removed by stirring and heating in a solvent, and a method in which the inorganic particles are removed 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, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[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 well-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 the 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 a method 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] (charge generation layer) The charge generating layer is a layer containing a titanium-containing organic pigment and a binder resin.

[0075] A suitable example of the titanium-containing organic pigment is titanyl phthalocyanine. Examples of oxytitanium phthalocyanine include well-known crystal types of oxytitanium phthalocyanine, such as α-type, β-type, C-type, D-type, Y-type, M-type, M-α-type, and I-type.

[0076] Among these, from the viewpoint of high sensitivity, Y-type or D-type oxytitanium phthalocyanine that exhibits a maximum diffraction peak at a Bragg angle (2θ±0.2°) of 27.3° in a powder X-ray diffraction spectrum using CuKα characteristic X-rays is preferred. Here, θ is the angle between the lattice plane of the crystal lattice and the incident wave.

[0077] Titanyl phthalocyanine is dried at 100°C under reduced pressure of 0.1 mmHg for 1 hour, and then left in an air atmosphere at room temperature (25°C) and normal pressure (1 atmosphere) for 12 hours. The molecular formula of the titanyl phthalocyanine is TiPc(HO). n (wherein Pc is a phthalocyanine residue, and n is 0.15 to 1.) Specifically, the titanyl phthalocyanine is preferably an oxytitanium phthalocyanine hydrate crystal described in JP-A-4-189873. The use of the above-mentioned hydrated crystal as titanyl phthalocyanine is preferred because it improves photosensitivity.

[0078] Other charge-generating materials may be used in combination with the titanium-containing organic pigment, provided that the proportion of the titanium-containing organic pigment in the total charge-generating materials is preferably 90% by mass or more, more preferably 95% by mass or more. Other charge-generating materials include well-known charge-generating materials such as azo pigments such as bisazo and trisazo; fused-ring aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments other than titanyl phthalocyanine; zinc oxide; and trigonal selenium.

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

[0080] 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.

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

[0082] The formation of the charge generation layer is not particularly limited, and a well-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.

[0083] 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.

[0084] 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.

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

[0086] The thickness of the charge generating layer is set, for example, preferably in the range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0087] (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.

[0088] 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.

[0089] 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.

[0090] [ka]

[0091] In structural formula (a-1), Ar T1 , Ar T2 , and Ar T3each 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.

[0092] [ka]

[0093] In structural formula (a-2), R T91 and R T92 R each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. T101 , R T102 , R T111 and R T112 each independently represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ) and R T12 , R T13 , R T14 , R T15 and R T16each 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.

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

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

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

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

[0098] The formation of the charge transport layer is not particularly limited, and a well-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 if necessary.

[0099] 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.

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

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

[0102] (protective layer) A protective layer may be provided on the photosensitive layer as needed, for example, to prevent chemical changes in the photosensitive layer when charged, or to further improve the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a layer made of a cured film (crosslinked film) as the protective layer. Examples of such a layer include the following layers 1) and 2).

[0103] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton in the same molecule (i.e., a layer containing a polymer or crosslinked product of the reactive group-containing charge transport material). 2) A layer composed of a cured film of a composition containing a non-reactive charge transport material and a reactive group-containing non-charge transport material that does not have a charge transport skeleton and has a reactive group (i.e., a layer containing a non-reactive charge transport material and a polymer or crosslinked product of the reactive group-containing non-charge transport material).

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

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

[0106] The charge transport skeleton of the reactive group-containing charge transport material is not particularly limited as long as it has a known structure in electrophotographic photoreceptors, and examples thereof include a skeleton derived from a nitrogen-containing hole transport compound such as a triarylamine compound, a benzidine compound, or a hydrazone compound, and having a conjugated structure with a nitrogen atom. Among these, a triarylamine skeleton is preferred.

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

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

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

[0110] Examples of solvents for preparing 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. The protective layer-forming coating liquid may be a solvent-free coating liquid.

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

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

[0113] [Image forming device (and 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, and a transfer device that transfers the toner image to the surface of a recording medium. The electrophotographic photosensitive member according to the present embodiment is used as the electrophotographic photosensitive member.

[0114] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, 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 an electrophotographic photosensitive member after transfer of a toner image but before charging; an apparatus equipped with a static elimination device that irradiates the surface of an electrophotographic photosensitive member with static elimination light to eliminate static electricity after transfer of a toner image but before charging; and an apparatus equipped with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

[0115] 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.

[0116] 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).

[0117] 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 also include at least one selected from the group consisting of a charging device, an electrostatic latent image forming device, a developing device, and a transfer device.

[0118] 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. Note that only the main parts shown in the drawings will be described, and descriptions of other parts will be omitted.

[0119] 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 to 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.

[0120] 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.

[0121] Note that FIG. 2 shows an example of an image forming apparatus equipped with a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists cleaning, but these may be arranged as needed.

[0122] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0123] -Charging device- The charging device 8 may be, for example, a contact-type charger using a conductive or semi-conductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. Also usable are non-contact type roller chargers, scorotron chargers and corotron chargers that utilize corona discharge, and other known chargers.

[0124] -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.

[0125] -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.

[0126] 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. Well-known developers are used.

[0127] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131 . In addition to the cleaning blade system, a fur brush cleaning system or a simultaneous development and cleaning system may also be used.

[0128] -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.

[0129] -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.

[0130] FIG. 3 is a schematic diagram showing another example of the configuration of the image forming apparatus according to the present embodiment. The image forming apparatus 120 shown in Fig. 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]

[0131] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0132] Example 1 -Production of electrophotographic photoreceptor- 100 parts by mass of zinc oxide particles (trade name: Nano Tek ZnO, manufactured by CI Chemical Co., Ltd.) were pre-dried by heating at 120° C. for 2 hours in a stainless steel tray. Next, 40 parts by mass of a 4% by mass toluene solution of N-β(aminoethyl)-γ-aminopropyltrimethoxysilane (silane coupling agent) was sprayed onto the pre-dried zinc oxide particles while stirring, and the mixture was stirred for 1 hour at 100° C. After that, the mixture was further baked for 1 hour at 175° C., and then pulverized in a mortar.

[0133] Next, 25 parts by mass of the zinc oxide particles surface-treated in the obtained Surface Treatment Example, 10 parts by mass of a curing agent (blocked isocyanate Sumidur 3175, manufactured by Sumitomo Bayer Urethane Co., Ltd.), 9 parts by mass of a butyral resin S-LEC BM-1 (manufactured by Sekisui Chemical Co., Ltd.), 60 parts by mass of methyl ethyl ketone, and 0.1 parts by mass of an additive (EDHA: 4-ethoxy-1,2-dihydroxy-9,10-anthraquinone) were mixed, and the mixture was dispersed in a sand mill using 1 mmφ glass beads for 2 hours to obtain a dispersion. To the resulting dispersion, 3 parts by mass of silicone ball "Tospearl 120 (manufactured by Nissho Sangyo Co., Ltd.)" and 0.01 parts by mass of silicone oil SH29PA (manufactured by DuPont Toray Specialty Materials Co., Ltd.) were added, thereby obtaining a coating liquid for forming an undercoat layer.

[0134] The obtained coating liquid for forming an undercoat layer was applied onto a cylindrical conductive aluminum substrate and dried and cured at 160° C. for 60 minutes, thereby forming an undercoat layer with a thickness of 23.5 μm. The coating solution was applied to the conductive substrate by dip coating, with the coating solution circulating at a flow rate of 1.5 L / min.

[0135] Next, a mixture consisting of 15 parts by mass of titanyl phthalocyanine, a titanium-containing organic pigment that serves as a charge-generating material and has a maximum diffraction peak at a Bragg angle (2θ±0.2°) of 27.3° in an X-ray diffraction spectrum using Cukα rays, 10 parts by mass of polyvinyl butyral resin (S-LEC BM-5, manufactured by Sekisui Chemical Co., Ltd.) that serves as a binder resin, and 300 parts by mass of n-butyl acetate was dispersed in a sand mill using 1 mmφ glass beads for 4 hours. Titanyl phthalocyanine is dried at 100°C under reduced pressure of 0.1 mmHg for 1 hour, and then left in an air atmosphere at room temperature (25°C) and normal pressure (1 atm) for 12 hours. The molecular formula of the titanyl phthalocyanine is TiPc(HO). n (wherein Pc is a phthalocyanine residue, and n is 0.15 to 1) was used. The resulting charge generating layer-forming coating liquid was dip coated onto the undercoat layer and dried to form a charge generating layer having a thickness of 150 nm.

[0136] Next, 4 parts by mass of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1']biphenyl-4,4'-diamine and 6 parts by mass of bisphenol Z polycarbonate resin (viscosity average molecular weight 40,000) were added to 80 parts by mass of chlorobenzene and dissolved. The obtained coating liquid for forming a charge transport layer was dip-coated on the charge generation layer and dried at 130° C. for 40 minutes, thereby forming a charge transport layer with a thickness of 25 μm.

[0137] By the above operations, a photoreceptor was obtained.

[0138] <Examples 2 to 24 and Comparative Examples 1 to 14> A photoreceptor was obtained in the same manner as in Example 1, except that the amount of zinc oxide particles relative to the binder resin and the amount of titanium-containing organic pigment relative to the binder resin were changed according to Table 1. However, the circulation flow rate of the coating solution during dip coating was adjusted so that the ratio of the Ti concentration and the Zn concentration to the total Ti concentration and Zn concentration in the region within ±500 nm in the film thickness direction from the interface between the undercoat layer and the charge generating layer would be the values ​​shown in Table 1. The amounts of zinc oxide particles and titanium-containing organic pigment shown in Table 1 are expressed in parts by mass when the amount of binder resin is taken as 100 parts by mass.

[0139] <Evaluation> (Ti concentration ratio and Zn concentration) The photoreceptor of each example was measured for the following properties according to the methods already described. The ratio of the Ti concentration and the Zn concentration to the total Ti concentration and Zn concentration in a region within ±500 nm from the interface between the undercoat layer and the charge generating layer in the film thickness direction

[0140] (Actual machine evaluation) The photoreceptor of each example was attached as a black photoreceptor to an image forming apparatus for evaluation ("DocuPrint DocuPrint CP400 ps II" manufactured by Fuji Business Innovation Co., Ltd.). The following evaluations were carried out using the image forming apparatus for evaluation. The image forming apparatus for evaluation is an image forming apparatus that includes a charging device of a DC charging type, but does not include a static eliminator that neutralizes the photosensitive member after toner transfer and before charging the photosensitive member.

[0141] -Positive Ghost- Positive ghosting was evaluated as follows. Using the image forming apparatus described above equipped with each photoreceptor, 100 sheets of a pattern chart having the letter "G" and a "solid black area" were continuously printed in an environment of 22°C and 55% RH, and the appearance of the letter "G" (ghost) in the solid black area of ​​the 100th image was visually observed and evaluated according to the following criteria. A+(◎): The letter "G" is not visible in the solid black area. A(○): The letter "G" can be vaguely seen in the solid black area. B(△): The letter "G" is slightly visible in the solid black area (no practical problems). C(×): The letter "G" is clearly visible and dark in the solid black area.

[0142] [Table 1]

[0143] The results shown in the table show that the photoreceptor of this example suppresses positive ghosts more effectively than the photoreceptor of the comparative example.

[0144] This embodiment includes the following aspects. (((1))) a conductive substrate; an undercoat layer provided on the conductive substrate and containing zinc oxide particles and a binder resin; a charge generating layer provided on the undercoat layer and including a titanium-containing organic pigment and a binder resin; a charge transport layer disposed on the charge generating layer; and the undercoat layer has a thickness of 15.0 μm or more and 30.0 μm or less, when the thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, in a region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer, the ratio of the Ti concentration and the Zn concentration to the total concentration of Ti and Zn are each 30% or more and 70% or less, When the thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, the ratio of the Ti concentration and the Zn concentration to the total concentration of the Ti concentration and the Zn concentration in a region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer is 20% or more and 80% or less, respectively. (((2))) The electrophotographic photoreceptor according to (((1))), wherein the titanium-containing organic pigment is titanyl phthalocyanine. (((3))) the undercoat layer has a thickness of 15.0 μm or more and 25.0 μm or less, The electrophotographic photoreceptor according to (((1))) or (((2))), wherein in a region within ±500 nm in the film thickness direction from the interface between the undercoat layer and the charge generating layer, the ratio of the Ti concentration and the Zn concentration to the total of the Ti concentration and the Zn concentration is 40% or more and 60% or less. (((4))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))) is provided, A process cartridge that is detachably attached to an image forming apparatus. (((5))) The electrophotographic photoreceptor according to any one of (((1))) to (((3))), a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic image forming device for forming an electrostatic image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic 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; An image forming apparatus comprising:

[0145] The effects of the above embodiment are as follows. According to the invention related to (((1))) or (((2))), an electrophotographic photoreceptor is provided in which positive ghosts are suppressed compared to when the thickness of the undercoat layer is less than 15.0 μm or exceeds 30.0 μm. According to the invention related to (((1))) or (((2))), when the film thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, an electrophotographic photoreceptor is provided in which positive ghosts are suppressed compared to when the Ti concentration ratio and the Zn concentration ratio are each less than 30% or more than 70%. According to the invention related to (((1))) or (((2))), when the film thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, an electrophotographic photoreceptor is provided in which positive ghosts are suppressed compared to when the Ti concentration ratio and the Zn concentration ratio are less than 20% or more than 80%, respectively.

[0146] According to the invention related to (((3))), an electrophotographic photoreceptor is provided in which positive ghosts are suppressed compared to when the thickness of the undercoat layer is less than 15.0 μm or exceeds 25.0 μm, or when the Ti concentration ratio and the Zn concentration ratio are each less than 40% or exceed 60%.

[0147] According to the invention related to (((4))) or (((5))), there is provided a process cartridge or an image forming apparatus in which, when the film thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, positive ghosts are suppressed compared to when an electrophotographic photosensitive member in which the Ti concentration ratio and the Zn concentration ratio are each less than 30% or more than 70%, respectively, is used. According to the invention related to (((4))) or (((5))), there is provided a process cartridge or an image forming apparatus in which, when the film thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, positive ghosts are suppressed compared to when an electrophotographic photosensitive member is used in which the Ti concentration ratio and the Zn concentration ratio are each less than 20% or more than 80%, respectively. [Explanation of symbols]

[0148] 1 conductive substrate, 2 subbing layer, 3 charge generation layer, 4 charge transport layer, 5 photosensitive layer, 6 protective layer, 10A photoreceptor

[0149] 7 electrophotographic photosensitive member, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 40 transfer device, 50 intermediate transfer body, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll-shaped), 133 fibrous member (flat brush-shaped), 300 process cartridge

Claims

1. a conductive substrate; an undercoat layer provided on the conductive substrate and containing zinc oxide particles and a binder resin; a charge generating layer provided on the undercoat layer and including a titanium-containing organic pigment and a binder resin; a charge transport layer disposed on the charge generating layer; and the undercoat layer has a thickness of 15.0 μm or more and 30.0 μm or less, when the thickness of the undercoat layer is 22.0 μm or more and 30.0 μm or less, the ratio of the Ti concentration and the Zn concentration to the total concentration of the Ti concentration and the Zn concentration in a region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer are each 30% or more and 70% or less, an electrophotographic photoreceptor, wherein when the thickness of the undercoat layer is 15.0 μm or more and less than 22.0 μm, in a region within ±500 nm in the thickness direction from the interface between the undercoat layer and the charge generating layer, the proportion of the Ti concentration and the proportion of the Zn concentration relative to the total of the Ti concentration and the Zn concentration are each 20% or more and 80% or less.

2. 2. The electrophotographic photoreceptor according to claim 1, wherein the titanium-containing organic pigment is titanyl phthalocyanine.

3. the undercoat layer has a thickness of 15.0 μm or more and 25.0 μm or less, 2. The electrophotographic photoreceptor according to claim 1, wherein in a region within ±500 nm in the film thickness direction from the interface between the undercoat layer and the charge generating layer, the ratio of the Ti concentration to the total Ti concentration and the Zn concentration is 40% or more and 60% or less.

4. The electrophotographic photoreceptor according to any one of claims 1 to 3 is provided, A process cartridge that is detachably attached to an image forming apparatus.

5. The electrophotographic photoreceptor according to any one of claims 1 to 3, a charging device that charges the surface of the electrophotographic photosensitive member; an electrostatic image forming device for forming an electrostatic image on the charged surface of the electrophotographic photosensitive member; a developing device that develops the electrostatic 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; An image forming apparatus comprising:

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