Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

To provide an electrophotographic photoreceptor that improves crack resistance of an inorganic protective layer.SOLUTION: An electrophotographic photoreceptor comprises: a conductive substrate; a photosensitive layer that is provided on the conductive substrate, and includes inorganic oxide particles; and an inorganic protective layer that is provided on the photosensitive layer. In the particle size distribution of the inorganic oxide particles obtained through cross-sectional observation of the photosensitive layer, at 6 nm as a boundary, the maximum peak for small diameter-side particles A is present in a range of 20 nm or more and 50 nm or less, and the maximum peak for large diameter-side particles B is present in a range of 80 nm or more and 400 nm or less, and the relationship between the particle diameter dA at the maximum peak for the small diameter-side particles A and the particle diameter dB at the maximum peak for the large diameter-side particles B satisfies the following formula (A1). Formula (A1): dB / dA≥4.0.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 electrophotographic photoreceptor having, in this order: a substrate; a photosensitive layer; and a protective layer containing oxygen and gallium, the protective layer having a first region located on the outer peripheral surface side; and a second region located closer to the substrate than the first region and having a larger atomic ratio [oxygen / gallium] than the first region."

[0003] Patent Document 2 discloses "an electrophotographic photoreceptor obtained by sequentially laminating on a conductive support at least a photosensitive layer and a surface protective layer having at least two or more types of fillers dispersed in a resin, wherein one type of the filler is diamond-like carbon or amorphous carbon fine particles having an average particle size of 50 nm or less, and at least another type of filler is an inorganic filler having an average particle size of 0.1 to 1.0 μm." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5447062 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-286887 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide an electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles, and an inorganic protective layer provided on the photosensitive layer, wherein, in the particle size distribution of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer, the maximum peak of small-diameter particles A is in the range of 20 nm to 50 nm, and the maximum peak of large-diameter particles B is in the range of 80 nm to 400 nm, with a particle size of 6 nm as the boundary, and the relationship between the particle size dA of the maximum peak of small-diameter particles A and the particle size dB of the maximum peak of large-diameter particles B does not satisfy formula (A1), and the crack resistance of the inorganic protective layer is improved compared to when this electrophotographic photoreceptor [Means for solving the problem]

[0006] Means for solving the above problems include the following aspects. <1> a conductive substrate; a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles; an inorganic protective layer provided on the photosensitive layer; Equipped with In the particle size distribution of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer, the maximum peak of smaller diameter particles A is in the range of 20 nm to 50 nm, and the maximum peak of larger diameter particles B is in the range of 80 nm to 400 nm, with a particle size of 6 nm as the boundary, and the relationship between the particle size dA of the maximum peak of the smaller diameter particles A and the particle size dB of the maximum peak of the larger diameter particles B satisfies the following formula (A1): Formula (A1): dB / dA≧4.0 <2> The relationship between the maximum peak particle diameter dA of the small diameter side particles A and the maximum peak particle diameter dB of the large diameter side particles B satisfies the following formula (A2): <1> Electrophotographic photoreceptor. Formula (A2): dB / dA≧6.0 <3> In the area ratio of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer, the relationship between the area ratio VA of the small diameter particles A and the area ratio VB of the large diameter particles B satisfies the following formula (B1): <1> or <2> The electrophotographic photoreceptor according to claim 1. Formula (B1): VB / (VA+VB)×100≧60% <4> The relationship between the area ratio VA of the small diameter particles A and the area ratio VB of the large diameter particles B satisfies the following formula (B2): <3> The electrophotographic photoreceptor according to claim 1. Formula (B2): VB / (VA+VB)×100≧70% <5> The area ratio of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer is 50% or more and 90% or less. <1> ~ <4> 10. The electrophotographic photoreceptor according to claim 9, wherein the electrophotographic photoreceptor is a <6> The area ratio of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer is 60% or more and 80% or less. <5> The electrophotographic photoreceptor according to claim 1. <7> The inorganic oxide particles are silica particles. <1> ~ <6> 10. The electrophotographic photoreceptor according to claim 9, wherein the electrophotographic photoreceptor is a <8> The inorganic protective layer is a layer containing gallium oxide. <1> ~ <7> 10. The electrophotographic photoreceptor according to claim 9, wherein the electrophotographic photoreceptor is a <9> a conductive substrate; a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles; an inorganic protective layer provided on the photosensitive layer; Equipped with the inorganic oxide particles include inorganic oxide particles α having an average particle size of 20 nm or more and 50 nm or less, and inorganic oxide particles β having an average particle size of 80 nm or more and 400 nm or less, An electrophotographic photosensitive member in which the relationship between the average particle diameter dα of the inorganic oxide particles α and the average particle diameter dβ of the inorganic oxide particles β satisfies the following formula (α1): Formula (α1): dβ / dα≧4.0 <10> <1> ~ <9> 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. <11> <1> ~ <9> 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 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; An image forming apparatus comprising: [Effects of the Invention]

[0007] <1> According to the invention, there is provided an electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles, and an inorganic protective layer provided on the photosensitive layer, in which, in the particle size distribution of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer, the maximum peak of small-diameter particles A is in the range of 20 nm to 50 nm, and the maximum peak of large-diameter particles B is in the range of 80 nm to 400 nm, with a particle size of 6 nm as the boundary, and the relationship between the particle size dA of the maximum peak of small-diameter particles A and the particle size dB of the maximum peak of large-diameter particles B does not satisfy formula (A1), and the electrophotographic photoreceptor has improved crack resistance of the inorganic protective layer compared to a case where the relationship does not satisfy formula (A1). <2> According to the invention, an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when formula (A2) is not satisfied. <3> According to the invention, an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when formula (B1) is not satisfied. <4> According to the invention, an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when formula (B2) is not satisfied. <5> According to the invention, an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when the area ratio of inorganic oxide particles is less than 50% or exceeds 90%. <6> According to the invention, an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when the area ratio of inorganic oxide particles is less than 60% or exceeds 80%. <7> According to the invention, there is provided an electrophotographic photoreceptor having a photosensitive layer containing silica particles as inorganic oxide particles, and in which the crack resistance of the inorganic protective layer is improved compared to when formula (A1) is not satisfied. <8> According to the invention, an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer containing gallium oxide is improved compared to when formula (A1) is not satisfied.

[0008] <9> According to the invention, there is provided an electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles, and an inorganic protective layer provided on the photosensitive layer, wherein the inorganic oxide particles comprise inorganic oxide particles α having an average particle size of 20 nm or more and 50 nm or less and inorganic oxide particles β having an average particle size of 80 nm or more and 400 nm or less, in which the relationship between the average particle size dα of the inorganic oxide particles α and the average particle size dβ of the inorganic oxide particles β does not satisfy formula (α1), and the inorganic protective layer has improved crack resistance compared to a case where the relationship does not satisfy formula (α1).

[0009] <10> , or <11> According to the invention described in (1), there is provided a process cartridge or an image forming apparatus including an electrophotographic photoreceptor having a conductive substrate, a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles, and an inorganic protective layer provided on the photosensitive layer, in which, in the particle size distribution of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer, the maximum peak of smaller diameter particles A is in the range of 20 nm or more and 50 nm or less, and the maximum peak of larger diameter particles B is in the range of 80 nm or more and 400 nm or less, with a particle size of 6 nm as the boundary, and the relationship between the particle size dA of the maximum peak of smaller diameter particles A and the particle size dB of the maximum peak of larger diameter particles B does not satisfy formula (A1), and in which the crack resistance of the inorganic protective layer is improved compared to an electrophotographic photoreceptor. [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] FIG. 3 is a partial cross-sectional view showing another example of the layer structure of the electrophotographic photosensitive member according to the present embodiment. [Figure 3] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 4] FIG. 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, exemplary embodiments of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the present disclosure.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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, 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.

[0017] In this disclosure, ppm is an abbreviation for parts per million and is based on mass.

[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 comprises a conductive substrate, a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles, and an inorganic protective layer provided on the photosensitive layer.

[0020] In the photoreceptor according to the first embodiment, in the particle size distribution of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer, the maximum peak of the smaller diameter particles A is in the range of 20 nm to 50 nm, and the maximum peak of the larger diameter particles B is in the range of 80 nm to 400 nm, with a particle size of 6 nm as the boundary. The relationship between the particle size dA of the maximum peak of the smaller diameter particles A and the particle size dB of the maximum peak of the larger diameter particles B satisfies the formula (A1) described below. In the photoreceptor according to the second embodiment, the inorganic oxide particles include inorganic oxide particles α having an average particle size of 20 nm or more and 50 nm or less, and inorganic oxide particles β having an average particle size of 80 nm or more and 400 nm or less, and the relationship between the average particle size dα of the inorganic oxide particles α and the average particle size dβ of the inorganic oxide particles β satisfies the formula (α1) described below.

[0021] The photoreceptor according to this embodiment has the above-described structure, which improves the crack resistance of the inorganic protective layer. The reason for this is presumed to be as follows.

[0022] Conventionally, in an electrophotographic photoreceptor having an inorganic protective layer, a technique has been known in which the photosensitive layer contains inorganic oxide particles (e.g., silica particles) to increase the hardness of the photosensitive layer in order to prevent the inorganic protective layer from cracking due to mechanical load. On the other hand, because the photosensitive layer contains inorganic oxide particles of a single particle size, there is a mathematical limit to the amount of inorganic oxide particles that can be packed (i.e., the content), and therefore there is an upper limit to the amount of inorganic oxide particles that can be contained in the photosensitive layer. It is also generally known that the greater the loading of inorganic oxide particles, the greater the hardness of the photosensitive layer. Therefore, there is an upper limit to the hardness of the photosensitive layer, along with an upper limit to the amount of inorganic oxide particles filled. However, in order to further improve the crack resistance of the inorganic protective layer, it is necessary to increase the hardness of the photosensitive layer.

[0023] Therefore, in the first embodiment, inorganic oxide particles are contained in the photosensitive layer so as to satisfy formula (A1). As a result, small diameter particles A are distributed in the gaps between large diameter particles B, and a higher inorganic oxide particle loading is achieved compared to when inorganic oxide particles of a single particle size are used. This also increases the hardness of the photosensitive layer, improving the crack resistance of the inorganic protective layer.

[0024] On the other hand, in the second embodiment, inorganic oxide particles are contained in the photosensitive layer so as to satisfy the formula (α1). As a result, the inorganic oxide particles α are distributed in the gaps between the inorganic oxide particles α, and a higher inorganic oxide particle loading is achieved compared to when inorganic oxide particles of a single particle size are used. This also increases the hardness of the photosensitive layer, improving the crack resistance of the inorganic protective layer.

[0025] From the above, it is presumed that the photoreceptor according to this embodiment has improved crack resistance of the inorganic protective layer.

[0026] The photoreceptor applicable to both the first and second embodiments will be described in detail below, however, the photoreceptor of the present disclosure may be a photoreceptor applicable to either the first or second embodiment.

[0027] FIG. 1 is a partial cross-sectional view schematically showing an example of the layer structure of a photoreceptor according to this embodiment. The photoreceptor 10A shown in FIG. 1 has a laminated photosensitive layer. The photoreceptor 10A has a conductive substrate 1 and a The photoreceptor 10A has a structure in which an undercoat layer 2, a charge generation layer 3, a charge transport layer 4, and an inorganic protective layer 6 are laminated in this order, 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 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.

[0028] Fig. 2 is a partial cross-sectional view schematically illustrating another example of the layer structure of the photoreceptor according to this embodiment. The photoreceptor 10B shown in Fig. 2 has a single-layer photosensitive layer. The photoreceptor 10B has a structure in which an undercoat layer 2, a photosensitive layer 5, and an inorganic protective layer 6 are laminated in this order on a conductive substrate 1. The photoreceptor 10B may have an intermediate layer (not shown) between the undercoat layer 2 and the photosensitive layer 5. The undercoat layer 2 may or may not be present.

[0029] When the photosensitive layer of the photoreceptor according to this embodiment is a laminated photosensitive layer consisting of a charge generation layer and a charge transport layer, the inorganic protective layer is disposed on and in contact with the charge transport layer, and the inorganic oxide particles are not contained in the charge generation layer but are contained in the charge transport layer. On the other hand, when the photosensitive layer of the photoreceptor according to this exemplary embodiment is a single-layer type photosensitive layer, the inorganic oxide particles are contained in the single-layer type photosensitive layer. That is, the inorganic oxide particles are contained in the layer of the photosensitive layer that is in contact with the inorganic protective layer.

[0030] In the present embodiment, when describing matters common to the multi-layer type photosensitive layer and the single-layer type photosensitive layer, they will be collectively referred to as photosensitive layer.

[0031] (Particle size distribution of inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer) In the particle size distribution of inorganic oxide particles obtained by observing the cross section of the photosensitive layer, particles on the smaller diameter side are designated as small diameter particles A and particles on the larger diameter side are designated as large diameter particles B, with a particle size of 6 nm as the boundary. The maximum peak of the small diameter particles A is in the range of 20 nm or more and 50 nm or less. The maximum peak of the larger diameter particles B is in the range of 80 nm or more and 400 nm or less. The relationship between the maximum peak particle diameter dA of the smaller diameter particles A and the maximum peak particle diameter dB of the larger diameter particles B satisfies the following formula (A1). When the relationship satisfies the following formula (A1), the hardness of the photosensitive layer (specifically, the charge transport layer or the single-layer photosensitive layer) increases, and the crack resistance of the inorganic protective layer improves. From the viewpoint of improving the crack resistance of the inorganic protective layer, the relationship preferably satisfies the following formula (A2), and more preferably satisfies the following formula (A3). Formula (A1): dB / dA≧4.0 Formula (A2): dB / dA≧6.0 Formula (A3): dB / dA≧7.0

[0032] Here, from the viewpoint of improving the crack resistance of the inorganic protective layer, it is preferable that the maximum peak of the small diameter particles A is in the range of 20 nm or more and 50 nm or less, and the maximum peak of the large diameter particles B is in the range of 80 nm or more and 400 nm or less. Furthermore, the upper limit of "dB / dA" is preferably 20.0 or less, and more preferably 15.0 or less, from the viewpoint that a large difference in particle size increases the number of smaller diameter particles required to form a configuration in which smaller diameter particles fill the gaps between larger diameter particles, thereby increasing the total area of ​​the interparticle interfaces and making it more likely that breakage will occur due to slippage at the interparticle interfaces.

[0033] The particle size distribution of the smaller diameter particles A and the larger diameter particles B is preferably a single-peak distribution. In other words, in the particle size distribution of the inorganic oxide particles, the smaller diameter particles A and the larger diameter particles B preferably have a single peak.

[0034] (Area ratio of inorganic oxide particles obtained by cross-sectional observation of photosensitive layer) In the area ratio of inorganic oxide particles obtained by observing a cross section of the photosensitive layer, the relationship between the area ratio VA of small diameter particles A and the area ratio VB of large diameter particles B preferably satisfies the following formula (B1). When the relationship satisfies the following formula (B1), the small diameter particles A are sufficiently embedded in the gaps between the large diameter particles B. This increases the hardness of the photosensitive layer (specifically, the charge transport layer or the single-layer photosensitive layer), improving the crack resistance of the inorganic protective layer. The relationship more preferably satisfies the following formula (B2), and even more preferably satisfies the following formula (B3). Formula (B1): VB / (VA+VB)×100≧60% Formula (B2): VB / (VA+VB)×100≧65% Formula (B3): VB / (VA+VB)×100≧70%

[0035] However, the upper limit of "VB / (VA+VB)" is preferably 85% or less, and more preferably 80% or less, from the viewpoint that if there are not enough small-diameter particles, the gaps between the large-diameter particles cannot be filled, and the effect of improving strength is reduced.

[0036] The area ratio of inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer (i.e., the area ratio of all inorganic oxide particles (VA+VB)) is preferably 50% or more and 90% or less, more preferably 55% or more and 85% or less, and even more preferably 60% or more and 80% or less. When the area ratio of the inorganic oxide particles is within the above range, the inorganic oxide particles are sufficiently packed in the photosensitive layer (specifically, the charge transport layer or the single-layer type photosensitive layer), which increases the hardness of the photosensitive layer (specifically, the charge transport layer or the single-layer type photosensitive layer) and improves the crack resistance of the inorganic protective layer.

[0037] Here, the area ratios of the small diameter particles A, the large diameter particles B, and the inorganic oxide are the area ratios relative to the layer in contact with the inorganic protective layer in the photosensitive layer (i.e., the charge transport layer or single-layer photosensitive layer containing inorganic oxide particles).

[0038] (Method for observing the cross section of the photosensitive layer) The cross section of the photosensitive layer was observed as follows. The photosensitive layer of the photoreceptor is cut in the thickness direction with a knife or the like, and the exposed cut surface is used as the observation surface to obtain a sample. Next, the observation surface of the sample is observed with a scanning electron microscope (SEM) to obtain a cross-sectional SEM image of the photosensitive layer.

[0039] Then, the particle size distribution of the inorganic oxide particles is obtained using a cross-sectional SEM image of the photosensitive layer. Specifically, the inorganic oxide particles are observed, and the images of the observed inorganic oxide particles are analyzed using image processing analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.) to determine the circle-equivalent diameters of at least 200 particles. Then, the particle size distribution of the inorganic oxide particles is obtained based on the obtained circle-equivalent diameters.

[0040] Meanwhile, the area ratios of small-diameter particles A, large-diameter particles B, and inorganic oxide particles are also determined using cross-sectional SEM images of the photosensitive layer. Specifically, the inorganic oxide particles are observed, and the images of the observed inorganic oxide particles are analyzed using image processing and analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.), and the area ratios of all observed inorganic oxide particles relative to the layer of the photosensitive layer that contacts the inorganic protective layer (i.e., the charge transport layer or single-layer photosensitive layer containing inorganic oxide particles) are determined. In addition, when measuring the area ratio of all inorganic oxide particles, the area ratio of small-diameter particles A with a particle size (i.e., equivalent circle diameter) of 6 nm or less and the area ratio of large-diameter particles B with a particle size (i.e., equivalent circle diameter) of more than 6 nm are also determined.

[0041] (Composition of inorganic oxide particles) Examples of inorganic oxide particles include silica particles, alumina particles, and titanium oxide particles. Among these, silica particles are preferred as inorganic oxide particles from the viewpoint of suppressing deterioration in the electrical properties of the photoreceptor.

[0042] Examples of silica particles include dry silica particles and wet silica particles. Examples of dry silica particles include combustion silica (fumed silica) obtained by burning a silane compound, and deflagration silica obtained by explosively burning metallic silicon powder. Examples of wet silica particles include wet silica particles obtained by the neutralization reaction of sodium silicate and mineral acid (precipitation silica synthesized and agglomerated under alkaline conditions, and gel-process silica particles synthesized and agglomerated under acidic conditions), colloidal silica particles (silica sol particles) obtained by polymerizing acidic silicic acid in an alkaline state, and sol-gel silica particles obtained by hydrolysis of organic silane compounds (e.g., alkoxysilanes). As the silica particles, from the viewpoint of suppressing image defects due to deterioration of electrical properties, combustion method silica (fumed silica) which has few silanol groups on the surface and a poor void structure is preferred.

[0043] From the viewpoint of dispersibility in the layer-forming coating liquid, the inorganic oxide particles are preferably surface-treated with a hydrophobic treatment agent, such as known silane compounds such as chlorosilanes, alkoxysilanes, and silazanes. The hydrophobic treatment agent is preferably a silane compound having a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group, that is, the silica particles preferably have trimethylsilyl groups, decylsilyl groups, or phenylsilyl groups on their surfaces. Examples of silane compounds having a trimethylsilyl group include trimethylchlorosilane, trimethylmethoxysilane, 1,1,1,3,3,3-hexamethyldisilazane, etc. Examples of silane compounds having a decylsilyl group include decyltrichlorosilane, decyltrichlorosilane, decyldimethylchlorosilane, decyltrimethoxysilane, etc. Examples of silane compounds having a phenyl group include triphenylmethoxysilane, triphenylchlorosilane, etc.

[0044] In order to satisfy formula (A1), inorganic oxide particles that include, for example, inorganic oxide particles α having an average particle size of 20 nm or more and 50 nm or less and inorganic oxide particles β having an average particle size of 80 nm or more and 400 nm or less are used. The relationship between the average particle size dα of the inorganic oxide particles α and the average particle size dβ of the inorganic oxide particles β satisfies, for example, the following formula (α1): Preferably, the relationship satisfies the following formula (α2), and more preferably the following formula (α3): Formula (α1): dβ / dα≧4.0 Formula (α2): dβ / dα≧6.0 Formula (α3): dβ / dα≧7.0

[0045] In order to satisfy the formula (B1) and the area ratio of the inorganic oxide particles, the amounts of the inorganic oxide particles α and inorganic oxide particles β having the above average particle diameters are adjusted.

[0046] Here, the average particle diameters of the inorganic oxide particles α and the inorganic oxide particles β are measured as follows. The inorganic oxide particles to be measured are observed under a scanning electron microscope, the circle-equivalent diameters of 100 randomly selected primary particles are determined, and the arithmetic mean of the circle-equivalent diameters is taken as the average particle size.

[0047] Each layer of the photoreceptor will be described in detail below.

[0048] [Conductive substrate] The conductive substrate may be, for example, a metal (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or a gold-containing alloy (stainless steel, etc.). Examples of conductive substrates include metal plates, metal drums, and metal belts. Examples of conductive substrates include paper, resin films, belts, and the like 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 Ωcm.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0057] For example, inorganic particles have a powder resistance (volume resistivity) of 1×10 2 Ωcm or more 1×10 11 Examples include inorganic particles with a particle size of Ωcm 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.

[0058] 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).

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] Examples of the electron-accepting compound 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; 2-(4-biphenyl)-2-(2-phenyl-2-methylphenyl)-1-propanol; )-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, and other oxadiazole-based compounds; xanthone-based 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.

[0068] 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.

[0069] The electron-accepting compound can be attached to the surface of the inorganic particles by, for example, a dry method or a wet method.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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 the binder resin used in the undercoat layer include a charge transporting resin having a charge transporting group, a conductive resin, and the like. Conductive resins (such as polyaniline) are also included.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0081] These additives may be used alone or as a mixture or polycondensation product of multiple compounds. Good too.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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, knife coating, and curtain coating.

[0087] The thickness of the undercoat layer is preferably set to 15 μm or more, more preferably in the range of 20 μm to 50 μm.

[0088] [Middle layer] The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include polymer compounds such as acetal resins (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.

[0089] Among these, the intermediate layer is preferably an organometallic compound containing zirconium atoms or silicon atoms. It is preferable that the layer contains a substance.

[0090] 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.

[0091] The thickness of the intermediate layer is preferably set in the range of 0.1 μm to 3 μm, and the intermediate layer may also be used as an undercoat layer.

[0092] [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 (Electro-Luminescence) image array.

[0093] 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.

[0094] 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, specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, or titanyl phthalocyanine.

[0095] 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.

[0096] The above charge-generating materials may also be used when using incoherent light sources such as LEDs and organic EL image arrays that emit light at a central wavelength of 450 nm to 780 nm. However, from the viewpoint of resolution, when using a thin photosensitive layer of 20 μm or less, the electric field strength in the photosensitive layer becomes high, and charge injection from the substrate can easily cause a decrease in charging, resulting in image defects known as black spots. This problem becomes more pronounced when using charge-generating materials that are p-type semiconductors, such as trigonal selenium and phthalocyanine pigments, that are prone to generating dark current.

[0097] 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.

[0098] 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, and acrylic. Examples of the insulating material include resins, polyacrylamide resins, polyvinylpyridine resins, cellulose resins, urethane resins, epoxy resins, casein, polyvinyl alcohol resins, and polyvinylpyrrolidone resins. 13 These binder resins can be used alone or in combination of two or more.

[0099] 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.

[0100] The charge generating layer may contain other known additives.

[0101] 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.

[0102] 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.

[0103] Methods for dispersing particles (e.g., charge-generating material) in the coating liquid for forming a charge-generating layer include media-based dispersers such as ball mills, vibration ball mills, attritors, sand mills, and horizontal sand mills, as well as media-less dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include 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 dispersion, it is effective to adjust the average particle size of the charge-generating material in the coating liquid for forming a charge-generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0104] 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, knife coating, and curtain coating.

[0105] The thickness of the charge generating layer is preferably set within the range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0106] [Charge transport layer] The charge transport layer is, for example, a layer containing a binder resin, a charge transport material, and inorganic oxide particles, or may be a layer containing a polymer charge transport material.

[0107] 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 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 can be used alone. One or more kinds of these may be used, but the present invention is not limited to these.

[0108] 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.

[0109] [ka]

[0110] 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 each of 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 each of the above groups also include substituted amino groups substituted with alkyl groups having from 1 to 3 carbon atoms.

[0111] [ka]

[0112] 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 each of 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 each of the above groups also include substituted amino groups substituted with alkyl groups having from 1 to 3 carbon atoms.

[0113] A triarylamine derivative represented by the structural formula (a-1), and a compound represented by the structural formula (a-2) Among the benzidine derivatives shown, in particular, "-C6H4-CH=CH-CH=C(RT7 )(R T8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 ) is preferred from the viewpoint of charge mobility.

[0114] 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.

[0115] 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.

[0116] The charge transport layer may contain other known additives.

[0117] The charge transport layer is formed by coating. An embodiment of the coating method includes, for example, preparing a coating liquid for forming the charge transport layer by dissolving or dispersing a binder resin, a charge transport material, and inorganic oxide particles in a solvent, applying the coating liquid for forming the charge transport layer to the surface of the charge generation layer to form a coating film, and drying the coating film.

[0118] 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.

[0119] As a method for dispersing inorganic oxide particles in the coating liquid for forming the charge transport layer, for example, a media disperser such as a ball mill, a vibration ball mill, an attritor, a sand mill, or a horizontal sand mill, or a medialess disperser such as a stirrer, an ultrasonic disperser, a roll mill, or a high-pressure homogenizer, may be used.

[0120] 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, knife coating, and curtain coating.

[0121] 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.

[0122] [Inorganic protective layer] The inorganic protective layer is an inorganic material layer. Examples of inorganic materials include metal oxides such as gallium oxide, aluminum oxide, zinc oxide, titanium oxide, indium oxide, tin oxide, and boron oxide; metal nitrides such as gallium nitride, aluminum nitride, zinc nitride, titanium nitride, indium nitride, tin nitride, and boron nitride; carbon-based and silicon-based inorganic materials such as diamond-like carbon, amorphous carbon, hydrogenated amorphous carbon, hydrogenated-fluorinated amorphous carbon, amorphous silicon carbide, hydrogenated amorphous silicon carbide, amorphous silicon, and hydrogenated amorphous silicon; and mixed crystals thereof.

[0123] From the viewpoint of the abrasion resistance and electrical properties of the photoreceptor, the inorganic protective layer is preferably a layer containing a metal oxide, more preferably a layer containing gallium oxide. The metal oxide contained in the inorganic protective layer may be one type or two or more types.

[0124] The volume resistivity of the inorganic protective layer is set to 1.0×10 10 It is preferable that the resistance is Ω·cm or more, and 1.0×10 11 It is more preferable that the resistivity is Ω·cm or more.

[0125] The volume resistivity of the inorganic protective layer was measured by the following method. The inorganic protective layer is peeled off from the photoreceptor to prepare a sample. The sample is clamped in the sample holder of an impedance analyzer (Toyo Corporation), and the resistance is measured at an AC voltage of 1 V and a frequency of 100 Hz, and calculated based on the electrode area and sample thickness.

[0126] The inorganic protective layer can be formed by plasma CVD (Chemical Vapor Deposition), organic Examples of known vapor deposition methods include metal vapor deposition, molecular beam epitaxy, evaporation, sputtering, etc. For example, the inorganic protective layer can be formed using the plasma CVD film deposition apparatus and film deposition conditions described in JP 2014-191179 A.

[0127] From the viewpoint of the abrasion resistance and electrical properties of the photoreceptor, the thickness of the inorganic protective layer is preferably 0.2 μm to 10 μm, more preferably 0.4 μm to 8 μm, and even more preferably 0.6 μm to 6 μm.

[0128] The thickness of each layer of the photoreceptor is the arithmetic mean of the values ​​measured with an electromagnetic film thickness meter, and the measurement points are four points at 90° intervals around the circumference of the axial center of the photoreceptor.

[0129] [Single-layer photosensitive layer] The single-layer photosensitive layer (charge generation / charge transport layer) is a layer containing, for example, a binder resin, a charge generation material, a charge transport material, and inorganic oxide particles. These materials are the same as those described for the charge generation layer and the charge transport layer.

[0130] The content of the charge generating material in the single-layer photosensitive layer is preferably 0.1% by mass to 10% by mass, and more preferably 0.8% by mass to 5% by mass, based on the total solid content. The content of the charge transport material in the single-layer photosensitive layer is preferably 5% by mass to 50% by mass, based on the total solid content.

[0131] The single-layer photosensitive layer is formed by coating. An embodiment of the coating method includes, for example, dissolving or dispersing a binder resin, a charge generating material, a charge transport material, and inorganic oxide particles in a solvent to prepare a coating liquid for forming a single-layer photosensitive layer, applying the coating liquid for forming a single-layer photosensitive layer to the surface of an undercoat layer or a conductive substrate to form a coating film, and drying the coating film. The details of the preparation method and application method for the coating liquid for forming a single-layer photosensitive layer are the same as those of the preparation method and application method for the coating liquid for forming a charge transport layer.

[0132] The thickness of the single-layer photosensitive layer is, for example, 5 μm or more and 50 μm or less, and preferably 10 μm or more and 40 μm or less.

[0133] <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, 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.

[0134] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as an apparatus including a fixing device that fixes a toner image transferred onto the surface of a recording medium; an apparatus of a direct transfer type that directly transfers a toner image formed on the surface of an electrophotographic photosensitive member onto a recording medium; an apparatus of an intermediate transfer type that primarily transfers a toner image formed on the surface of an electrophotographic photosensitive member onto the surface of an intermediate transfer member, and then secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium; an apparatus including a cleaning device that cleans the surface of an electrophotographic photosensitive member after transfer of a toner image but before charging; an apparatus including 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 including an electrophotographic photosensitive member heating member that increases the temperature of the electrophotographic photosensitive member and reduces the relative temperature.

[0135] 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.

[0136] 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).

[0137] 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.

[0138] 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 descriptions of other parts will be omitted.

[0139] FIG. 3 is a schematic diagram showing an example of the configuration of an image forming apparatus according to this embodiment. As shown in FIG. 3, the image forming apparatus 100 according to this embodiment includes an electrophotographic photosensitive member 7. The image forming apparatus 100 includes a process cartridge 300 for transferring a toner image thereon, 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, and the intermediate transfer member 50 is disposed with a portion thereof in contact with the electrophotographic photosensitive member 7. Although not shown, the image forming apparatus 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.

[0140] 3 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.

[0141] FIG. 3 shows an example of an image forming apparatus that includes 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, which may be arranged as needed.

[0142] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0143] -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.

[0144] -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.

[0145] -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.

[0146] 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.

[0147] -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.

[0148] -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.

[0149] -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.

[0150] FIG. 4 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. 4 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer 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]

[0151] 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).

[0152] Example 1 [Formation of undercoat layer] As a conductive substrate, an aluminum cylindrical tube having an outer diameter of 30 mm, a length of 250 mm, and a wall thickness of 1 mm was prepared.

[0153] Zinc oxide (average particle size 70 nm, specific surface area 15 m 2 100 parts of a silane coupling agent (trade name: KBM603, Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) was added and stirred for 2 hours. The toluene was then 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.

[0154] 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.

[0155] 100 parts of a solution prepared by dissolving 60 parts of alizarin-added zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, trade name: Sumidur 3175, Sumitomo Bayer Urethane Co., Ltd.), and 15 parts of a butyral resin (trade name: S-LEC BM-1, Sekisui Chemical Co., Ltd.) in 68 parts of methyl ethyl ketone was mixed with 5 parts of methyl ethyl ketone, and the mixture was dispersed in a sand mill using glass beads with a diameter of 1 mm for 2 hours to obtain a dispersion. 0.005 parts of octyltin dilaurate and 4 parts of silicone resin particles (product name: Tospearl 145, Momentive Performance Materials) were added to obtain a coating solution for forming an undercoat layer. The coating solution for forming an undercoat layer was applied to the outer surface of the conductive substrate by dip coating, and then dried and cured at 170°C for 40 minutes to form an undercoat layer with a thickness of 20 μm.

[0156] [Formation of charge generation layer] A mixture consisting of 15 parts of hydroxygallium phthalocyanine (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, manufactured by 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 to form a 0.25 μm thick charge-generating layer.

[0157] [Formation of charge transport layer] Binder resin: Polycarbonate resin (1) (viscosity average molecular weight: 40,000, the numerical values ​​in the structural formula indicate the molar ratio (mol %)) 20 parts ·Charge transport material: CTM-1 ···15 parts Silica particles α (average particle size dα = 20 nm) hydrophobized with 1,1,1,3,3,3-hexamethyldisilazane. The volume ratio Vα of silica particles α to the charge transport layer is the volume % shown in Table 1. Silica particles β hydrophobized with 1,1,1,3,3,3-hexamethyldisilazane (average particle size dβ = 80 nm) Amount that makes the volume ratio Vβ of silica particles β in the charge transport layer the volume % shown in Table 1 Solvent: tetrahydrofuran (THF) 600 parts The above materials were mixed and stirred for 12 hours to obtain a coating solution for forming a charge transport layer. The coating solution for forming a charge transport layer was dip-coated onto the charge generation layer, and the coating film was dried to form a charge transport layer with a thickness of 30 μm. The volume ratio described here is a calculated value calculated from the weights of the polycarbonate resin, CTM-1, and silica particles added as materials. Specifically, the density of the polycarbonate resin (1) is 1.2 g / cm 3 , the density of CTM-1 is 1.2 g / cm 3 , the density of silica particles is 2.2 g / cm3 The volume of each particle was calculated as follows, and the ratio of the volume of silica particles to the total volume was defined as the volume ratio.

[0158] [ka]

[0159] [Formation of inorganic protective layer] Using trimethylgallium as the film-forming material, an amorphous layer containing gallium oxide was formed as an inorganic protective layer by plasma CVD. The layer thickness was 1 μm.

[0160] Through the above steps, a photoreceptor was obtained.

[0161] <Examples 2 to 15 and Comparative Examples 1 to 6> A photoreceptor was obtained in the same manner as in Example 1, except for the following changes: In Comparative Example 1, only one type of silica particles was used in the charge transport layer. · Average particle size dα and volume fraction Vα of silica particles α · Average particle size dβ and volume fraction Vβ of silica particles β

[0162] <Photoreceptor characteristic measurement> According to the method already described, the cross section of the charge transport layer of each photoreceptor was observed, and the following properties were measured. The maximum peaks of small particle A and large particle B in the particle size distribution of silica particles as inorganic oxide particles The area ratio of silica particles as inorganic oxide particles, and the area ratio of small-diameter particles A and large-diameter particles B among silica particles

[0163] <Photoreceptor performance measurement> [Hardness of photosensitive layer] The hardness of the surface of the photosensitive layer of each example of the photoreceptor was measured as follows. First, the inorganic protective layer was peeled off from the photoreceptor of each example to obtain a sample. The hardness of the sample is Young's modulus (GPa) determined by the nanoindentation method. The axial direction of the photoreceptor was fixed horizontally, and the measurement was made at the apex at the center of the axial direction of the photoreceptor. Measurements were made at four positions at 90° intervals around the circumferential direction of the photoreceptor, and the Young's moduli at the four positions were arithmetically averaged. The measurement conditions using the nanoindenter are as follows. The measurement results are shown in Table 1. Test equipment: Product name HM-500, Fisher Instruments Co., Ltd. Indenter: Diamond triangular indenter with a 115° edge angle Load: 75mN

[0164] [Crack resistance of inorganic protective layer] The cracking load of the inorganic protective layer was measured as follows to evaluate the crack resistance of the inorganic protective layer. Measurements were made using a microhardness tester, with the load being increased from 0 mN to 5 mN increments. Observations were made with an optical microscope each time a load was applied, and the load at which the inorganic protective layer broke was taken as the crack initiation load. The measurement conditions were as follows. The measurement results are shown in Table 1. Test equipment: Product name DUH-201, Shimadzu Corporation Indenter: Diamond spherical indenter

[0165] [Table 1-1]

[0166] [Table 1-2]

[0167] From the above results, it can be seen that the photoreceptor of this example has higher resistance to cracking of the inorganic protective layer than the photoreceptor of the comparative example.

[0168] This embodiment includes the following aspects. (((1))) a conductive substrate; a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles; an inorganic protective layer provided on the photosensitive layer; Equipped with In the particle size distribution of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer, the maximum peak of smaller diameter particles A is in the range of 20 nm to 50 nm, and the maximum peak of larger diameter particles B is in the range of 80 nm to 400 nm, with a particle size of 6 nm as the boundary, and the relationship between the particle size dA of the maximum peak of the smaller diameter particles A and the particle size dB of the maximum peak of the larger diameter particles B satisfies the following formula (A1): Formula (A1): dB / dA≧4.0 (((2))) The relationship between the maximum peak particle diameter dA of the small diameter particles A and the maximum peak particle diameter dB of the large diameter particles B satisfies the following formula (A2) (((1))). Formula (A2): dB / dA≧6.0 (((3))) The electrophotographic photoreceptor according to (((1))) or (((2))), wherein, in the area ratios of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer, the relationship between the area ratio VA of the small diameter particles A and the area ratio VB of the large diameter particles B satisfies the following formula (B1): Formula (B1): VB / (VA+VB)×100≧60% (((4))) The electrophotographic photoreceptor according to (((3))), wherein the relationship between the area ratio VA of the small diameter particles A and the area ratio VB of the large diameter particles B satisfies the following formula (B2): Formula (B2): VB / (VA+VB)×100≧70% (((5))) The electrophotographic photoreceptor according to any one of (((1))) to (((4))), wherein the area ratio of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer is 50% or more and 90% or less. (((6))) The electrophotographic photoreceptor according to (((5))), wherein the area ratio of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer is 60% or more and 80% or less. (((7))) The electrophotographic photoreceptor according to any one of (((1))) to (((6))), wherein the inorganic oxide particles are silica particles. (((8))) The electrophotographic photoreceptor according to any one of ((1))) to (((7))), wherein the inorganic protective layer is a layer containing gallium oxide. (((9))) a conductive substrate; a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles; an inorganic protective layer provided on the photosensitive layer; Equipped with the inorganic oxide particles include inorganic oxide particles α having an average particle size of 20 nm or more and 50 nm or less, and inorganic oxide particles β having an average particle size of 80 nm or more and 400 nm or less, An electrophotographic photosensitive member in which the relationship between the average particle diameter dα of the inorganic oxide particles α and the average particle diameter dβ of the inorganic oxide particles β satisfies the following formula (α1): Formula (α1): dβ / dα≧4.0 (((10))) The electrophotographic photoreceptor according to any one of (((1))) to (((9))) is provided, A process cartridge that is detachably attached to an image forming apparatus. (((11))) The electrophotographic photoreceptor according to any one of (((1))) to (((9))), 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; An image forming apparatus comprising:

[0169] The effects of the above embodiment are as follows. According to the invention related to (((1))), there is provided an electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles, and an inorganic protective layer provided on the photosensitive layer, in which, in the particle size distribution of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer, the maximum peak of small-diameter particles A is in the range of 20 nm or more and 50 nm or less, and the maximum peak of large-diameter particles B is in the range of 80 nm or more and 400 nm or less, with a particle size of 6 nm as the boundary, and the relationship between the particle size dA of the maximum peak of small-diameter particles A and the particle size dB of the maximum peak of large-diameter particles B does not satisfy formula (A1), and the electrophotographic photoreceptor has improved crack resistance of the inorganic protective layer compared to a case where the relationship does not satisfy formula (A1). According to the invention related to (((2))), an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when formula (A2) is not satisfied. According to the invention related to (((3))), an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when formula (B1) is not satisfied. According to the invention related to (((4))), an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when formula (B2) is not satisfied. According to the invention related to (((5))), an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when the area ratio of inorganic oxide particles is less than 50% or more than 90%. According to the invention related to (((6))), an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared to when the area ratio of inorganic oxide particles is less than 60% or more than 80%. According to the invention related to (((7))), there is provided an electrophotographic photoreceptor having a photosensitive layer containing silica particles as inorganic oxide particles, and in which the crack resistance of the inorganic protective layer is improved compared to when formula (A1) is not satisfied. According to the invention related to (((8))), an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer containing gallium oxide is improved compared to when formula (A1) is not satisfied.

[0170] According to the invention of (((9))), there is provided an electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles, and an inorganic protective layer provided on the photosensitive layer, wherein the inorganic oxide particles comprise inorganic oxide particles α having an average particle size of 20 nm or more and 50 nm or less and inorganic oxide particles β having an average particle size of 80 nm or more and 400 nm or less, in which the crack resistance of the inorganic protective layer is improved compared to when the relationship between the average particle size dα of the inorganic oxide particles α and the average particle size dβ of the inorganic oxide particles β does not satisfy formula (α1).

[0171] According to the invention described in (((10))) or (((11))), there is provided a process cartridge or an image forming apparatus including an electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles, and an inorganic protective layer provided on the photosensitive layer, in which, in the particle size distribution of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer, the maximum peak of smaller diameter particles A is in the range of 20 nm or more and 50 nm or less, and the maximum peak of larger diameter particles B is in the range of 80 nm or more and 400 nm or less, with a particle size of 6 nm as the boundary, and the relationship between the particle size dA of the maximum peak of smaller diameter particles A and the particle size dB of the maximum peak of larger diameter particles B does not satisfy formula (A1), and in which the crack resistance of the inorganic protective layer is improved compared to an electrophotographic photoreceptor. [Explanation of symbols]

[0172] 1 Conductive substrate, 2 Undercoat layer, 3 Charge generation layer, 4 Charge transport layer, 5 Photosensitive layer, 6 Inorganic protective layer, 10A photoreceptor, 10B photoreceptor

[0173] 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; a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles; an inorganic protective layer provided on the photosensitive layer; Equipped with In the particle size distribution of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer, the maximum peak of smaller diameter particles A is in the range of 20 nm to 50 nm, and the maximum peak of larger diameter particles B is in the range of 80 nm to 400 nm, with a particle size of 6 nm as the boundary, and the relationship between the particle size dA of the smaller diameter particles A at the maximum peak and the particle size dB of the larger diameter particles B at the maximum peak satisfies the following formula (A1): Formula (A1): dB / dA≧4.0

2. 2. The electrophotographic photosensitive member according to claim 1, wherein the relationship between the maximum peak particle diameter dA of the smaller particle A and the maximum peak particle diameter dB of the larger particle B satisfies the following formula (A2): Formula (A2): dB / dA≧6.0

3. 2. The electrophotographic photoreceptor according to claim 1, wherein, in the area ratios of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer, a relationship between an area ratio VA of the small diameter particles A and an area ratio VB of the large diameter particles B satisfies the following formula (B1): Formula (B1): VB / (VA+VB)×100≧60%

4. 4. The electrophotographic photosensitive member according to claim 3, wherein the relationship between the area ratio VA of the small diameter particles A and the area ratio VB of the large diameter particles B satisfies the following formula (B2): Formula (B2): VB / (VA+VB)×100≧70%

5. 2. The electrophotographic photoreceptor according to claim 1, wherein an area ratio of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer is 50% or more and 90% or less.

6. 6. The electrophotographic photoreceptor according to claim 5, wherein an area ratio of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer is 60% or more and 80% or less.

7. 2. The electrophotographic photoreceptor according to claim 1, wherein the inorganic oxide particles are silica particles.

8. 2. The electrophotographic photoreceptor according to claim 1, wherein the inorganic protective layer is a layer containing gallium oxide.

9. a conductive substrate; a photosensitive layer provided on the conductive substrate and containing inorganic oxide particles; an inorganic protective layer provided on the photosensitive layer; Equipped with the inorganic oxide particles include inorganic oxide particles α having an average particle size of 20 nm or more and 50 nm or less, and inorganic oxide particles β having an average particle size of 80 nm or more and 400 nm or less, The electrophotographic photoreceptor has a relationship between the average particle diameter dα of the inorganic oxide particles α and the average particle diameter dβ of the inorganic oxide particles β that satisfies the following formula (α1): Formula (α1): dβ / dα≧4.0

10. An electrophotographic photoreceptor according to any one of claims 1 to 9, A process cartridge that is detachably attached to an image forming apparatus.

11. The electrophotographic photoreceptor according to any one of claims 1 to 9, 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; An image forming apparatus comprising:

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