Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

The invention discloses an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus, the electrophotographic photoreceptor includes 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 the particle size distribution of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer, the maximum peak of small-diameter-side particles A is in the range of 20-50 nm inclusive, the maximum peak of large-diameter-side particles B is in the range of 80-400 nm inclusive, and the maximum peak of the small-diameter-side particles A is in the range of 20-50 nm inclusive, with the particle size of 60 nm as the boundary, and the maximum peak of the large-diameter-side particles B is in the range of 80-400 nm inclusive. And the relationship between the particle diameter dA of the maximum peak of the small-diameter-side particles A and the particle diameter dB of the maximum peak of the large-diameter-side particles B satisfies formula (A1). Formula (A1): dB / dA > = 4.0.

Description

Technical Field

[0001] The present invention relates to an electronic photographic photoreceptor, a processing box and an image forming device. Background Art

[0002] Japanese Patent No. 5447062 discloses "an electrophotographic photoreceptor comprising, in order, a substrate, a photosensitive layer, and a protective layer, the protective layer containing oxygen and gallium, and having a first region located on the peripheral surface side and a second region located closer to the substrate than the first region and having an atomic ratio (oxygen / gallium) greater than that of the first region."

[0003] Japanese Patent Publication No. 2004-286887 discloses "an electrophotographic photoreceptor formed by sequentially stacking at least a photosensitive layer and a surface protective layer on a conductive support, wherein the surface protective layer has at least two or more fillers dispersed in a resin, and the electrophotographic photoreceptor is characterized in that one of the fillers is diamond-like carbon or amorphous carbon particles having an average particle size of less than 50 nm, and at least another filler is an inorganic filler having an average particle size of 0.1 to 1.0 μm." Summary of the Invention

[0004] The object of the present invention is to provide an electronic photographic photoreceptor comprising: a conductive substrate; a photosensitive layer, the photosensitive layer being arranged on the conductive substrate and containing inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being arranged on the photosensitive layer, wherein the crack resistance of the inorganic protective layer is improved compared with the following situation: in the particle size distribution of the inorganic oxide particles obtained by observing the cross section of the photosensitive layer, with a particle size of 60 nm as the boundary, the maximum peak of the small-diameter side particles A exists in the range of greater than 20 nm and less than 50 nm, and the maximum peak of the large-diameter side particles B exists in the range of greater than 80 nm and less than 400 nm, and the relationship between the particle size dA of the maximum peak of the small-diameter side particles A and the particle size dB of the maximum peak of the large-diameter side particles B does not satisfy formula (A1).

[0005] According to a first embodiment of the present invention, an electronic photographic photoreceptor is provided, comprising: a conductive substrate; a photosensitive layer, the photosensitive layer being arranged on the conductive substrate and comprising inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being arranged on the photosensitive layer, wherein in the particle size distribution of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer, with a particle size of 60 nm as the boundary, the maximum peak of the small-diameter side particles A exists in a range of greater than 20 nm and less than 50 nm, and the maximum peak of the large-diameter side particles B exists in a range of greater than 80 nm and less than 400 nm, and the relationship between the particle size dA of the maximum peak of the small-diameter side particles A and the particle size dB of the maximum peak of the large-diameter side particles B satisfies the following formula (A1).

[0006] Formula (A1): dB / dA ≥ 4.0

[0007] According to a second aspect of the present invention, in the electrophotographic photoreceptor according to the first aspect, the relationship between the maximum peak particle size dA of the small-diameter particles A and the maximum peak particle size dB of the large-diameter particles B satisfies the following formula (A2).

[0008] Formula (A2): dB / dA ≥ 6.0

[0009] According to the third scheme of the present invention, in the electronic photographic photoreceptor involved in the first or second scheme, in the area ratio of the inorganic oxide particles obtained by observing the cross section of the photosensitive layer, the relationship between the area ratio VA of the small-diameter side particles A and the area ratio VB of the large-diameter side particles B satisfies the following formula (B1).

[0010] Formula (B1): VB / (VA+VB)×100≥60%

[0011] According to a fourth aspect of the present invention, in the electrophotographic photoreceptor according to the third aspect, the relationship between the area ratio VA of the smaller-diameter particles A and the area ratio VB of the larger-diameter particles B satisfies the following formula (B2).

[0012] Formula (B2): VB / (VA+VB)×100≥70%

[0013] According to a fifth aspect of the present invention, in the electrophotographic photoreceptor according to any one of the first to fourth aspects, an area ratio of the inorganic oxide particles observed through a cross section of the photosensitive layer is 50% to 90%.

[0014] According to a sixth aspect of the present invention, in the electrophotographic photoreceptor according to the fifth aspect, an area ratio of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer is 60% to 80%.

[0015] According to a seventh aspect of the present invention, in the electrophotographic photoreceptor according to any one of the first to sixth aspects, the inorganic oxide particles are silica particles.

[0016] According to an eighth aspect of the present invention, in the electrophotographic photoreceptor according to any one of the first to seventh aspects, the inorganic protective layer is a layer containing gallium oxide.

[0017] According to the ninth embodiment of the present invention, an electronic photographic photosensitive body is provided, which comprises: a conductive substrate; a photosensitive layer, the photosensitive layer being arranged on the conductive substrate and comprising inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being arranged on the photosensitive layer, the inorganic oxide particles comprising inorganic oxide particles α having an average particle size of greater than 20 nm and less than 50 nm and inorganic oxide particles β having an average particle size of greater than 80 nm and less than 400 nm, 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 following formula (α1).

[0018] Formula (α1): dβ / dα≥4.0

[0019] According to a tenth aspect of the present invention, there is provided a process cartridge including the electrophotographic photoreceptor according to any one of the first to ninth aspects, wherein the process cartridge is attachable to and detachable from an image forming apparatus.

[0020] According to the eleventh embodiment of the present invention, there is provided an image forming device comprising: the electronic photographic photoreceptor according to any one of the first to ninth embodiments; a charging device for charging the surface of the electronic photographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electronic photographic photoreceptor; a developing device for developing the electrostatic latent image formed on the surface of the electronic photographic photoreceptor using a developer containing a colorant to form a colorant image; and a transfer device for transferring the colorant image to the surface of a recording medium.

[0021] (Effect)

[0022] According to the first scheme, an electronic photographic photoreceptor is provided, which comprises: a conductive substrate; a photosensitive layer, the photosensitive layer being arranged on the conductive substrate and containing inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being arranged on the photosensitive layer, wherein the crack resistance of the inorganic protective layer is improved compared with the following situation: in the particle size distribution of the inorganic oxide particles obtained by observing the cross section of the photosensitive layer, with a particle size of 60 nm as the boundary, the maximum peak of the small-diameter side particles A exists in the range of greater than 20 nm and less than 50 nm, and the maximum peak of the large-diameter side particles B exists in the range of greater than 80 nm and less than 400 nm, and the relationship between the particle size dA of the maximum peak of the small-diameter side particles A and the particle size dB of the maximum peak of the large-diameter side particles B does not satisfy formula (A1).

[0023] According to the second aspect, there is provided an electrophotographic photoreceptor having an inorganic protective layer with improved crack resistance compared to a case where the formula (A2) is not satisfied.

[0024] According to the third aspect, there is provided an electrophotographic photoreceptor having an inorganic protective layer with improved crack resistance compared to a case where the formula (B1) is not satisfied.

[0025] According to the fourth aspect, there is provided an electrophotographic photoreceptor in which the crack resistance of the inorganic protective layer is improved compared to a case where the formula (B2) is not satisfied.

[0026] According to the fifth aspect, there is provided an electrophotographic photoreceptor having an inorganic protective layer with improved crack resistance compared to a case where the area ratio of the inorganic oxide particles is less than 50% or exceeds 90%.

[0027] According to the sixth aspect, there is provided an electrophotographic photoreceptor having an inorganic protective layer with improved crack resistance compared to a case where the area ratio of the inorganic oxide particles is less than 60% or exceeds 80%.

[0028] According to the seventh aspect, there is provided an electrophotographic photoreceptor having a photosensitive layer containing silica particles as inorganic oxide particles, wherein the crack resistance of the inorganic protective layer is improved compared to a case where the formula (A1) is not satisfied.

[0029] According to the eighth aspect, there is provided an electrophotographic photoreceptor in which the crack resistance of the inorganic protective layer containing gallium oxide is improved compared to a case where the formula (A1) is not satisfied.

[0030] According to the ninth scheme, an electronic photographic photoreceptor is provided, which comprises: a conductive substrate; a photosensitive layer, the photosensitive layer being arranged on the conductive substrate and comprising inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being arranged on the photosensitive layer, the inorganic oxide particles comprising inorganic oxide particles α having an average particle size of greater than 20 nm and less than 50 nm and inorganic oxide particles β having an average particle size of greater than 80 nm and less than 400 nm, wherein the crack resistance of the inorganic protective layer is improved compared with the case where 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).

[0031] According to the tenth or eleventh scheme, a processing box or image forming device having an electronic photographic photosensitive body is provided, which has improved crack resistance of the inorganic protective layer compared with the case of having the following electronic photographic photosensitive body: it has: a conductive substrate; a photosensitive layer, the photosensitive layer is arranged on the conductive substrate and contains inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer is arranged on the photosensitive layer, wherein, in the particle size distribution of the inorganic oxide particles obtained by observing the cross section of the photosensitive layer, with a particle size of 60 nm as the boundary, the maximum peak of the small-diameter side particles A exists in the range of greater than 20 nm and less than 50 nm, and the maximum peak of the large-diameter side particles B exists in the range of greater than 80 nm and less than 400 nm, and the relationship between the particle size dA of the maximum peak of the small-diameter side particles A and the particle size dB of the maximum peak of the large-diameter side particles B does not satisfy formula (A1). BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a partial cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor according to the present embodiment;

[0033] Figure 2 is a partial cross-sectional view showing another example of the layer structure of the electrophotographic photoreceptor of this embodiment;

[0034] Figure 3 FIG. 1 is a schematic structural diagram showing an example of an image forming apparatus according to the present embodiment;

[0035] Figure 4 This is a schematic structural diagram showing another example of the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION

[0036] Hereinafter, an embodiment of the present invention will be described. These descriptions and examples are for illustrative purposes only and do not limit the scope of the present invention.

[0037] In the present invention, a numerical range expressed using “to” indicates a range including the numerical values ​​described before and after “to” as the minimum value and the maximum value, respectively.

[0038] In the numerical range of recording in stages in the present invention, the upper limit or lower limit of recording in one numerical range can also be replaced by the upper limit or lower limit of the numerical range of recording in other stages. In addition, in the numerical range of recording in the present invention, the upper limit or lower limit of the numerical range can also be replaced by the value shown in the embodiment.

[0039] In the present invention, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the purpose of the process can be achieved.

[0040] In the present invention, when the embodiments are described with reference to the drawings, the configuration of the embodiments is not limited to the configuration shown in the drawings. In addition, the sizes of the components in the drawings are conceptual sizes, and the relative relationship between the sizes of the components is not limited to this.

[0041] In the present invention, each component may also include multiple corresponding substances. In the present invention, when the amount of each component in the composition is mentioned, if multiple substances equivalent to each component are present in the composition, the amount of each component refers to the total amount of the multiple substances present in the composition, unless otherwise specified.

[0042] In the present invention, multiple types of particles corresponding to each component may be included. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for the mixture of the multiple types of particles present in the composition unless otherwise specified.

[0043] In the present invention, unless otherwise specified, alkyl groups and alkylene groups include linear, branched, and cyclic groups.

[0044] In the present invention, hydrogen atoms in groups such as organic groups, aromatic rings, linking groups, alkyl groups, alkylene groups, aryl groups, aralkyl groups, alkoxy groups, and aryloxy groups may be replaced by halogen atoms.

[0045] In the present invention, when a compound is represented by a structural formula, the symbols (C and H) representing carbon atoms and hydrogen atoms in a hydrocarbon group and / or a hydrocarbon chain may be omitted.

[0046] In the present invention, ppm is the abbreviation of parts per million and is a mass standard.

[0047] In the present invention, the “axial direction” of the electrophotographic photoreceptor refers to the direction in which the rotation axis of the electrophotographic photoreceptor extends, and the “circumferential direction” of the electrophotographic photoreceptor refers to the rotation direction of the electrophotographic photoreceptor.

[0048] <Electrophotographic photoreceptor>

[0049] The electrophotographic photoreceptor (hereinafter also referred to as “photoreceptor”) of this embodiment includes 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.

[0050] In the photosensitive body of the first embodiment, in the particle size distribution of the inorganic oxide particles obtained by observing the cross section of the photosensitive layer, with the particle size of 60 nm as the boundary, the maximum peak of the small-diameter side particles A exists in the range of greater than 20 nm and less than 50 nm, and the maximum peak of the large-diameter side particles B exists in the range of greater than 80 nm and less than 400 nm, and the relationship between the particle size dA of the maximum peak of the small-diameter side particles A and the particle size dB of the maximum peak of the large-diameter side particles B satisfies the formula (A1) described later.

[0051] In the photoreceptor of the second embodiment, the inorganic oxide particles include inorganic oxide particles α with an average particle size of greater than 20 nm and less than 50 nm and inorganic oxide particles β with an average particle size of greater than 80 nm and less than 400 nm, 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 later.

[0052] The photoreceptor of this embodiment has the above-described structure, which improves the crack resistance of the inorganic protective layer. The reason for this is presumably as follows.

[0053] Conventionally, it is known that in an electrophotographic photoreceptor having an inorganic protective layer, inorganic oxide particles (such as silica particles) are contained in the photosensitive layer to improve the hardness of the photosensitive layer in order to suppress the inorganic protective layer from cracking due to mechanical load.

[0054] On the other hand, since the photosensitive layer contains inorganic oxide particles of a single particle size, the filling amount (ie, content) of the inorganic oxide particles is mathematically limited. Therefore, there is an upper limit to the amount of inorganic oxide particles that can be contained in the photosensitive layer.

[0055] In addition, it is generally known that the harder the photosensitive layer is, the greater the filling amount of the inorganic oxide particles is.

[0056] Therefore, the hardness of the photosensitive layer also has an upper limit according to the upper limit of the filling amount of the inorganic oxide particles.

[0057] However, in order to further improve the crack resistance of the inorganic protective layer, the hardness of the photosensitive layer is required to be increased.

[0058] Therefore, in the first embodiment, the photosensitive layer contains inorganic oxide particles to satisfy formula (A1). This results in a state where small-diameter particles A are distributed in the gaps between large-diameter particles B, achieving a higher loading of inorganic oxide particles compared to the case of using inorganic oxide particles of a single particle size. This also increases the hardness of the photosensitive layer and improves the crack resistance of the inorganic protective layer.

[0059] On the other hand, in the second embodiment, the photosensitive layer contains inorganic oxide particles so as to satisfy formula (α1). This results in inorganic oxide particles α being distributed in the gaps between inorganic oxide particles β, achieving a higher loading of inorganic oxide particles than when using inorganic oxide particles of a single particle size. This also increases the hardness of the photosensitive layer and improves the crack resistance of the inorganic protective layer.

[0060] From the above, it is presumed that the photoreceptor of this embodiment has improved crack resistance of the inorganic protective layer.

[0061] The following describes in detail the photoreceptors corresponding to both the first and second embodiments. However, the photoreceptor of the present invention may be any photoreceptor corresponding to one of the first and second embodiments.

[0062] Figure 1 This is a partial cross-sectional view schematically showing an example of the layer structure of the photoreceptor according to this embodiment. Figure 1 The photoreceptor 10A shown has a laminated photosensitive layer. Photoreceptor 10A has a structure in which an undercoat layer 2, a charge generating layer 3, a charge transport layer 4, and an inorganic protective layer 6 are sequentially laminated on a conductive substrate 1. The charge generating layer 3 and the charge transport layer 4 constitute a photosensitive layer 5 (a so-called functionally separated photosensitive layer). Photoreceptor 10A may also have an intermediate layer (not shown) between the undercoat layer 2 and the charge generating layer 3. The undercoat layer 2 may or may not be present.

[0063] Figure 2 This is a partial cross-sectional view schematically showing another example of the layer structure of the photoreceptor according to this embodiment. Figure 2 The photoreceptor 10B shown 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 sequentially laminated on a conductive substrate 1. The photoreceptor 10B may also include 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.

[0064] In the case where the photosensitive layer of the photoreceptor of this embodiment is a laminated photosensitive layer composed of a charge generating layer and a charge transporting layer, the inorganic protective layer is disposed on the charge transporting layer in contact with the charge transporting layer. Furthermore, the inorganic oxide particles are contained in the charge transporting layer, not in the charge generating layer.

[0065] On the other hand, when the photosensitive layer of the photoreceptor of the present embodiment is a single-layer photosensitive layer, the inorganic oxide particles are contained in the single-layer photosensitive layer.

[0066] That is, the inorganic oxide particles are contained in a layer in contact with the inorganic protective layer in the photosensitive layer.

[0067] In this embodiment, when describing matters common to the laminated photosensitive layer and the single-layer photosensitive layer, they are collectively referred to as a photosensitive layer.

[0068] (Particle Size Distribution of Inorganic Oxide Particles Obtained by Cross-Section Observation of Photosensitive Layer)

[0069] In the particle size distribution of the inorganic oxide particles obtained by cross-sectional observation of the photosensitive layer, particles on the smaller diameter side were designated as smaller diameter particles A, and particles on the larger diameter side were designated as larger diameter particles B, with a particle diameter of 60 nm as a boundary.

[0070] The maximum peak of the particles A on the smaller diameter side exists in the range of 20 nm to 50 nm.

[0071] The maximum peak of the large-diameter particles B exists in the range of 80 nm to 400 nm.

[0072] Furthermore, 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 (A1).

[0073] When this 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.

[0074] From the viewpoint of improving the crack resistance of the inorganic protective layer, this relationship preferably satisfies the following formula (A2), and more preferably satisfies the following formula (A3).

[0075] Formula (A1): dB / dA ≥ 4.0

[0076] Formula (A2): dB / dA ≥ 6.0

[0077] Formula (A3): dB / dA ≥ 7.0

[0078] Here, from the viewpoint of improving the crack resistance of the inorganic protective layer, it is preferred that the maximum peak of the small-diameter particles A exists in the range of 20 nm to 50 nm, and the maximum peak of the large-diameter particles B exists in the range of 80 nm to 400 nm.

[0079] In addition, with regard to the upper limit of "dB / dA", since the difference in particle size is large, the number of small-diameter particles required to fill the gaps between large-diameter particles with small-diameter particles increases, and the total area of ​​the interface between particles increases. As a result, damage caused by deviation at the interface between particles is likely to occur. From this point of view, the upper limit of "dB / dA" is preferably less than 20.0, and more preferably less than 15.0.

[0080] Furthermore, the particle size distribution of the small-diameter particles A and the large-diameter particles B is preferably unimodal. That is, in the particle size distribution of the inorganic oxide particles, there is preferably one peak for the small-diameter particles A and the large-diameter particles B.

[0081] (Area ratio of inorganic oxide particles obtained by cross-sectional observation of photosensitive layer)

[0082] In the area ratio 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 preferably satisfies the following formula (B1).

[0083] When this relationship satisfies the following formula (B1), the smaller-diameter particles A fully enter the gaps between the larger-diameter particles B. This increases the hardness of the photosensitive layer (specifically, the charge transport layer or the single-layer photosensitive layer) and improves the crack resistance of the inorganic protective layer.

[0084] This relationship more preferably satisfies the following formula (B2), and further preferably satisfies the following formula (B3).

[0085] Formula (B1): VB / (VA+VB)×100≥60%

[0086] Formula (B2): VB / (VA+VB)×100≥65%

[0087] Formula (B3): VB / (VA+VB)×100≥70%

[0088] However, as for the upper limit of "VB / (VA+VB)", if a sufficient amount of small-diameter particles is not included, the gaps between the large-diameter particles cannot be filled, and the effect of improving strength becomes smaller. From this point of view, VB / (VA+VB) is preferably less than 85%, and more preferably less than 80%.

[0089] The area ratio of the 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% to 90%, more preferably 55% to 85%, and even more preferably 60% to 80%.

[0090] When the area ratio of the inorganic oxide particles is within the above range, the photosensitive layer (specifically, the charge transport layer or the single-layer photosensitive layer) is fully filled with the inorganic oxide particles. This increases the hardness of the photosensitive layer (specifically, the charge transport layer or the single-layer photosensitive layer) and improves the crack resistance of the inorganic protective layer.

[0091] Here, the area ratios of the small-diameter particles A, large-diameter particles B, and inorganic oxide particles 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).

[0092] (Method for observing cross section of photosensitive layer)

[0093] The cross-sectional observation method of the photosensitive layer is as follows.

[0094] The photosensitive layer of the photoreceptor is cut in the thickness direction using a knife or the like, and a sample is obtained with the exposed cut surface serving as an observation surface.

[0095] Next, the observation surface of the sample was observed using a scanning electron microscope (SEM) to obtain a cross-sectional SEM image of the photosensitive layer.

[0096] Next, a cross-sectional SEM image of the photosensitive layer was used to determine the particle size distribution of the inorganic oxide particles. Specifically, the inorganic oxide particles were observed and analyzed using image processing and analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.) to determine the equivalent circular diameters of at least 200 particles. Based on these equivalent circular diameters, the particle size distribution of the inorganic oxide particles was determined.

[0097] On the other hand, the area ratios of the small-diameter particles A, large-diameter particles B, and inorganic oxide particles were also determined using a cross-sectional SEM image of the photosensitive layer. Specifically, the inorganic oxide particles were observed, and the image of the observed inorganic oxide particles was analyzed using image processing and analysis software WinRoof (manufactured by Mitani Shoji Co., Ltd.). The area ratio of all the observed inorganic oxide particles relative to the layer in contact with the inorganic protective layer in the photosensitive layer (i.e., the charge transport layer or the single-layer photosensitive layer containing the inorganic oxide particles) was determined.

[0098] In addition, in the measurement of 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 less than 60 nm and the area ratio of large-diameter particles B with a particle size (i.e., equivalent circle diameter) exceeding 60 nm are also calculated.

[0099] (Structure of Inorganic Oxide Particles)

[0100] Examples of the inorganic oxide particles include silica particles, alumina particles, and titania particles.

[0101] Among them, from the viewpoint of suppressing the reduction in electrical characteristics of the photoreceptor, the inorganic oxide particles are preferably silica particles.

[0102] Examples of the silica particles include dry silica particles and wet silica particles.

[0103] Examples of dry silica particles include combustion silica (fumed silica) obtained by burning a silane compound and explosion silica obtained by explosively burning metallic silicon powder.

[0104] Examples of wet silica particles include wet silica particles obtained by a neutralization reaction of sodium silicate and an inorganic acid (precipitated silica synthesized / aggregated under alkaline conditions, gel-process silica particles synthesized / aggregated under acidic conditions), colloidal silica particles (silica sol particles) obtained by making acidic silicic acid alkaline and polymerizing it, and sol-gel silica particles obtained by hydrolyzing an organic silane compound (e.g., alkoxysilane).

[0105] As the silica particles, from the viewpoint of suppressing image defects caused by deterioration of electrical characteristics, preferably used are fumed silica (fumed silica) having a small number of silanol groups on the surface and a poor void structure.

[0106] The inorganic oxide particles are preferably surface-treated with a hydrophobizing agent from the viewpoint of dispersibility in the layer-forming coating liquid. Examples of the hydrophobizing agent include well-known silane compounds such as chlorosilane, alkoxysilane, and silazane.

[0107] As the hydrophobizing agent, a silane compound having a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group is preferred. That is, the silica particles preferably have a trimethylsilyl group, a decylsilyl group, or a phenylsilyl group on their surface.

[0108] Examples of silane compounds having a trimethylsilyl group include trimethylchlorosilane, trimethylmethoxysilane, and 1,1,1,3,3,3-hexamethyldisilazane. Examples of silane compounds having a decylsilyl group include decyltrichlorosilane, decyldimethylchlorosilane, and decyltrimethoxysilane. Examples of silane compounds having a phenyl group include triphenylmethoxysilane and triphenylchlorosilane.

[0109] In order to satisfy the formula (A1), inorganic oxide particles including inorganic oxide particles α having an average particle size of 20 nm to 50 nm and inorganic oxide particles β having an average particle size of 80 nm to 400 nm are used.

[0110] 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 following formula (α2), and more preferably the following formula (α3).

[0111] Formula (α1): dβ / dα≥4.0

[0112] Formula (α2): dβ / dα≥6.0

[0113] Formula (α3): dβ / dα≥7.0

[0114] Furthermore, the amounts of the inorganic oxide particles α and the inorganic oxide particles β having the above-mentioned average particle diameter are adjusted so as to satisfy the formula (B1) and the area ratio of the inorganic oxide particles.

[0115] Here, the average particle diameters of the inorganic oxide particles α and the inorganic oxide particles β are measured as follows.

[0116] The inorganic oxide particles to be measured are observed with a scanning electron microscope, and the equivalent circle diameters of 100 randomly selected primary particles are determined. The arithmetic average of the equivalent circle diameters is taken as the average particle size.

[0117] Next, each layer of the photoreceptor will be described in detail.

[0118] [Conductive substrate]

[0119] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Furthermore, examples of conductive substrates include paper, resin films, and belts coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.), or alloys. Here, "conductive" means a volume resistivity of less than 1×10 13 Ω·cm.

[0120] When using electrophotographic photoreceptors in laser printers, the surface of the conductive substrate is preferably roughened to a centerline average roughness Ra of 0.04 μm to 0.5 μm to suppress interference fringes generated during laser irradiation. When using non-interfering light as the light source, roughening is not particularly necessary to prevent interference fringes. However, roughening can help extend the life of the printer by suppressing defects caused by irregularities on the conductive substrate surface.

[0121] Examples of methods for roughening the surface include wet honing in which an abrasive is suspended in water and sprayed onto the conductive substrate; centerless grinding in which the conductive substrate is pressed against a rotating grindstone and continuously ground; and anodizing.

[0122] As a method for roughening the surface, the following method can be cited: instead of 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.

[0123] The roughening treatment based on anodizing is to form an oxide film on the surface of the conductive substrate by carrying out anodizing in an electrolyte solution with a conductive substrate made of metal (such as aluminum) as an anode. As an electrolyte solution, for example, sulfuric acid solution, oxalic acid solution etc. can be enumerated. However, the porous anodized film formed by anodizing is chemically active under the original state, easily contaminated, and the resistance change caused by the environment is also large. Thus, preferably, the porous anodized film is carried out to a sealing process, in which the micropores of the oxide film are blocked by the volume expansion caused by hydration reaction in pressurized steam or boiling water (metal salts such as nickel can be added), and the oxide film is changed into a more stable hydrated oxide.

[0124] The thickness of the anodic oxide film is preferably 0.3 μm to 15 μm, for example. If the film thickness is within the above range, the film tends to exhibit a barrier property against injection and tends to suppress an increase in residual potential due to repeated use.

[0125] The conductive substrate may be subjected to treatment using an acidic treatment liquid or boehmite treatment.

[0126] The treatment using 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. As for the mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution, for example, phosphoric acid is in the range of 10% by mass to 11% by mass, chromic acid is in the range of 3% by mass to 5% by mass, and hydrofluoric acid is in the range of 0.5% by mass to 2% by mass, and the overall concentration of these acids is 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.

[0127] Boehmite treatment can be performed, for example, by immersing the film in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting the film with heated steam at 90°C to 120°C for 5 to 60 minutes. The film thickness is preferably 0.1 μm to 5 μm. The film can also be further anodized using an electrolyte solution with low film solubility, such as adipic acid, boric acid, borates, phosphates, phthalates, maleates, benzoates, tartrates, or citrates.

[0128] [Base coating]

[0129] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0130] Examples of the inorganic particles include particles having a powder resistance (volume resistivity) of 1×10 2 Ω·cm or more and 1×10 11Inorganic particles with a particle size of Ω·cm or less.

[0131] Among them, as the inorganic particles having the above-mentioned resistance value, for example, metal oxide particles such as tin oxide particles, titanium dioxide particles, zinc oxide particles, and zirconium oxide particles are preferred, and zinc oxide particles are particularly preferred.

[0132] The specific surface area of ​​the inorganic particles based on the BET method is preferably 10 m 2 / g or above.

[0133] The volume average particle size of the inorganic particles is preferably, for example, 50 nm or more and 2000 nm or less (preferably 60 nm or more and 1000 nm or less).

[0134] The content of the inorganic particles is, for example, preferably 10% by mass or more and 80% by mass or less, and more preferably 40% by mass or more and 80% by mass or less, relative to the binder resin.

[0135] The inorganic particles may be surface-treated. Inorganic particles having different surface treatments or two or more inorganic particles having different particle sizes may be mixed and used.

[0136] Examples of the surface treatment agent include silane coupling agents, titanate coupling agents, aluminum coupling agents, surfactants, etc. In particular, silane coupling agents are preferred, and silane coupling agents having an amino group are more preferred.

[0137] Examples of the silane coupling agent 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.

[0138] Silane coupling agents can also be used in combination of two or more. For example, a silane coupling agent having an amino group and other silane coupling agents can also be used in combination. As other silane coupling agents, for example, vinyl trimethoxysilane, 3-methacryloxypropyl-tris (2-methoxyethoxy) silane, 2- (3,4-epoxycyclohexyl) ethyl trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, vinyl triacetoxysilane, 3-mercaptopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, N-2- (aminoethyl) -3-aminopropyl trimethoxysilane, N-2- (aminoethyl) -3-aminopropyl methyl dimethoxysilane, N, N-bis (2-hydroxyethyl) -3-aminopropyl triethoxysilane, 3-chloropropyl trimethoxysilane, etc. can be mentioned, but it is not limited thereto.

[0139] The surface treatment method using the surface treatment agent may be any method as long as it is a known method, and may be either a dry method or a wet method.

[0140] The treatment amount of the surface treatment agent is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0141] Here, from the viewpoint of improving the long-term stability of electrical characteristics and carrier blocking properties, the undercoat layer preferably contains an electron acceptor compound (acceptor compound) together with the inorganic particles.

[0142] Examples of electron acceptor compounds include quinone compounds such as tetrachlorobenzoquinone and tetrabromobenzoquinone; tetracyanoquinolinemethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; diphenoquinone compounds such as 3,3',5,5'-tetra-tert-butyldiphenoquinone; and electron transporting substances such as benzophenone compounds.

[0143] As the electron acceptor compound, a compound having an anthraquinone structure is particularly preferred. Examples of the compound having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds. Specifically, examples include anthraquinone, alizarin, quinizarin, anthrarutin, and purpurin.

[0144] The electron acceptor compound may be contained in the undercoat layer in a dispersed state together with the inorganic particles, or may be contained in a state of being attached to the surface of the inorganic particles.

[0145] Examples of a method for attaching the electron acceptor compound to the surface of the inorganic particles include a dry method and a wet method.

[0146] The dry method, for example, involves adding an electron acceptor compound directly or dissolved in an organic solvent while stirring the inorganic particles using a mixer with high shear force, spraying the electron acceptor compound with dry air or nitrogen to adhere the electron acceptor compound to the surface of the inorganic particles. The dropwise addition or spraying of the electron acceptor compound is preferably performed at a temperature below the boiling point of the solvent. Alternatively, the dropwise addition or spraying of the electron acceptor compound may be followed by sintering at a temperature above 100°C. The sintering process is not particularly limited, as long as the temperature and time required to achieve electrophotographic properties are sufficient.

[0147] The wet method is, for example, a method in which inorganic particles are dispersed in a solvent using a stirrer, ultrasonic disperser, sand mill, grinder, ball mill, etc., while adding an electron acceptor compound and stirring or dispersing, and then removing the solvent to attach the electron acceptor compound to the surface of the inorganic particles. The solvent removal method is, for example, distillation removal by filtration or distillation. After the solvent is removed, sintering may be further performed at a temperature above 100°C. There are no particular restrictions on sintering, as long as the temperature and time are such that electronic photographic characteristics can be obtained. In the wet method, the water content of the inorganic particles may also be removed before adding the electron acceptor compound. Examples thereof include a method of removing the water content in the solvent while stirring and heating, and a method of removing the water content by azeotropic reaction with the solvent.

[0148] The electron acceptor compound may be attached before or after the inorganic particles are subjected to surface treatment using a surface treatment agent, or may be attached simultaneously with the surface treatment using a surface treatment agent.

[0149] The content of the electron acceptor compound is, for example, preferably 0.01% by mass or more and 20% by mass or less, and more preferably 0.01% by mass or more and 10% by mass or less, relative to the inorganic particles.

[0150] Examples of the binder resin used for the primer layer include acetal resins (e.g., polyvinyl butyral), 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-modified alkyd resins, urea-formaldehyde resins, phenol resins, phenol-formaldehyde resins, melamine resins, polyurethane resins, alkyd resins, epoxy resins, and other known polymer compounds; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; alkoxytitanium compounds; organic titanium compounds; and silane coupling agents.

[0151] Examples of the binder resin used for the primer layer include charge transporting resins having a charge transporting group and conductive resins (eg, polyaniline).

[0152] Among them, the binder resin used as the primer layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and is particularly preferably a thermosetting resin such as urea-formaldehyde resin, phenol resin, phenol-formaldehyde resin, melamine resin, polyurethane resin, unsaturated polyester resin, alkyd resin, epoxy resin; or a resin obtained by reacting at least one resin selected from the group consisting of polyamide resin, polyester resin, polyether resin, methacrylic resin, acrylic resin, polyvinyl alcohol resin and polyvinyl acetal resin with a curing agent.

[0153] When two or more of these binder resins are used in combination, the mixing ratio thereof is set as needed.

[0154] The undercoat layer may contain various additives for the purpose of improving electrical characteristics, enhancing environmental stability, and improving image quality.

[0155] Examples of additives include known materials such as polycyclic condensation-based and azo-based electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, alkoxytitanium compounds, organic titanium compounds, and silane coupling agents. Silane coupling agents are used for surface treatment of inorganic particles as described above, but can also be added to the primer as an additive.

[0156] Examples of the silane coupling agent used as an additive 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.

[0157] Examples of the zirconium chelate compound include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, zirconium acetylacetonate butoxide, zirconium ethyl acetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octylate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium methacrylate butoxide, zirconium stearate butoxide, and zirconium isostearate butoxide.

[0158] Examples of the titanium chelate compound include tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, titanium polyacetylacetonate, titanium octyl glycolate, titanium ammonium lactate, titanium lactate, titanium ethyl lactate, triethanolamine titanium, and polyhydroxytitanium stearate.

[0159] Examples of the aluminum chelate compound include aluminum isopropoxide, diisopropoxymonobutoxyaluminum, aluminum butyrate, diethylacetoacetate aluminum diisopropoxide, and tris(ethylacetoacetoxy)aluminum.

[0160] These additives may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0161] The Vickers hardness of the primer layer is preferably 35 or higher.

[0162] To suppress moire patterns, the surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to be from 1 / (4n) to 1 / 2 of the wavelength λ of the exposure laser used (n is the refractive index of the upper layer).

[0163] To adjust the surface roughness, resin particles or the like may be added to the primer layer. Examples of the resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. Furthermore, to adjust the surface roughness, the primer layer surface may be ground. Examples of the grinding method include soft leather polishing, sandblasting, wet honing, and grinding.

[0164] The formation of the undercoat layer is not particularly limited and can be performed using a known formation method, for example, by forming a coating film of an undercoat layer-forming coating liquid obtained by adding the above-mentioned components to a solvent, drying the coating film, and heating as needed.

[0165] Examples of the solvent used for preparing the coating liquid for forming the undercoat layer include well-known organic solvents such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketone alcohol solvents, ether solvents, and ester solvents.

[0166] Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene dichloride, chloroform, chlorobenzene, and toluene.

[0167] Examples of the method for dispersing the inorganic particles when preparing the coating liquid for forming an undercoat layer include known methods such as a roll mill, a ball mill, a vibration ball mill, an attritor, a sand mill, a colloid mill, and a paint sieve.

[0168] Examples of a method for applying the coating liquid for forming an undercoat layer onto a conductive substrate include common methods such as doctor blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0169] The thickness of the primer layer is preferably set to 15 μm or more, and more preferably set to be within the range of 20 μm or more and 50 μm or less.

[0170] [Middle layer]

[0171] The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include polymer compounds such as acetal resins (e.g., polyvinyl butyral), 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-modified alkyd resins, phenol-formaldehyde resins, and melamine resins.

[0172] The intermediate layer may also be a layer containing an organic metal compound. Examples of the organic metal compound used in the intermediate layer include organic metal compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon.

[0173] The compounds used in the intermediate layer may be used alone or as a mixture or polycondensate of a plurality of compounds.

[0174] Among them, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0175] The intermediate layer can be formed without particular limitation and can be formed using a known formation method, for example, by forming a coating film of an intermediate layer-forming coating liquid obtained by adding the above-mentioned components to a solvent, drying the coating film, and heating as needed.

[0176] As a coating method for forming the intermediate layer, a common method such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, curtain coating, etc. is used.

[0177] The thickness of the intermediate layer is preferably set within a range of 0.1 μm to 3 μm. The intermediate layer can also be used as a primer layer.

[0178] [Charge Generation Layer]

[0179] The charge generating layer is, for example, a layer comprising a charge generating material and a binder resin. Alternatively, the charge generating layer may be a vapor-deposited layer of the charge generating material. This vapor-deposited layer of charge generating material is suitable for use with non-interfering light sources such as LEDs (Light Emitting Diodes) and organic EL (Electro-Luminescence) image arrays.

[0180] Examples of the charge generating material include azo pigments such as disazo and trisazo; ring-condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0181] Among them, in order to cope with near-infrared laser exposure, metal phthalocyanine pigments or metal-free phthalocyanine pigments are preferably used as charge generating materials. Specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and oxytitanium phthalocyanine are more preferred.

[0182] On the other hand, in order to cope with near-ultraviolet laser exposure, preferred charge generating materials include cyclic aromatic pigments such as dibromoanthrone and anthrone, thioindigo pigments, tetraazaporphyrin compounds, zinc oxide, trigonal selenium, and disazo pigments.

[0183] The above-mentioned charge generation material can also be used when using a non-interfering light source such as an LED or an organic EL array whose central wavelength of light emission is from 450 nm to 780 nm.

[0184] In contrast, when using n-type semiconductors such as cyclic aromatic pigments, perylene pigments, and azo pigments as charge-generating materials, dark current is less likely to occur, and even thin films can suppress image defects known as black spots. The n-type is determined by the polarity of the photocurrent flowing using the commonly used time-of-flight method, with those that more readily carry electrons as carriers than holes being designated n-type.

[0185] The binder resin used in the charge generating layer can be selected from a wide range of insulating resins. Alternatively, the binder resin can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane.

[0186] Examples of the binder resin include polyvinyl butyral resin, polyarylate resin (a polycondensate of bisphenols and aromatic dicarboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinyl pyridine resin, cellulose resin, polyurethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinyl pyrrolidone resin. Here, "insulating property" means a volume resistivity of 10 13 These binder resins are used alone or in combination of two or more.

[0187] The mixing ratio of the charge generating material and the binder resin is preferably in the range of 10:1 to 1:10 in terms of mass ratio.

[0188] The charge generating layer may contain other known additives.

[0189] The charge generating layer can be formed without particular limitation and can be formed using a known method, for example, by forming a film of a charge generating layer-forming coating liquid obtained by adding the above-mentioned components to a solvent, drying the film, and optionally heating it. The charge generating layer can also be formed by vapor deposition of the charge generating material. Formation of the charge generating layer by vapor deposition is particularly suitable when using cyclic aromatic pigments or perylene pigments as the charge generating material.

[0190] Examples of the solvent used for preparing the charge generating layer-forming coating solution 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 dichloride, chloroform, chlorobenzene, and toluene. These solvents may be used alone or in combination of two or more.

[0191] As a method for dispersing particles (e.g., charge generating material) in a coating liquid for forming a charge generating layer, for example, a medium disperser such as a ball mill, a vibrating ball mill, a grinder, a sand mill, a horizontal sand mill, or a medium-free disperser such as a stirrer, an ultrasonic disperser, a roller mill, or a high-pressure homogenizer is used. As a high-pressure homogenizer, for example, a collision method in which the dispersion liquid is subjected to liquid-liquid collision or liquid-wall collision under high pressure, or a penetration method in which the dispersion liquid is dispersed by penetrating a fine flow path under high pressure can be cited. During dispersion, it is effective to set the average particle size of the charge generating material in the coating liquid for forming a charge generating layer to be less than 0.5 μm, preferably less than 0.3 μm, and more preferably less than 0.15 μm.

[0192] Examples of methods for applying the charge generating layer-forming coating liquid onto the undercoat layer (or intermediate layer) include common methods such as doctor blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0193] The thickness of the charge generating layer is preferably set to be in the range of 0.1 μm to 5.0 μm, and more preferably in the range of 0.2 μm to 2.0 μm.

[0194] [Charge transport layer]

[0195] The charge transport layer is, for example, a layer containing a binder resin, a charge transport material, and inorganic oxide particles. The charge transport layer may also be a layer containing a polymer charge transport material.

[0196] Examples of charge transport materials include electron transport compounds such as quinone compounds such as p-benzoquinone, tetrachlorobenzoquinone, tetrabromobenzoquinone, and anthraquinone; tetracyanoquinolmethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanoethylene compounds; and vinyl compounds. Other examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted vinyl compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination of two or more, but are not limited thereto.

[0197] As the charge transport material, from the viewpoint of charge mobility, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2) are preferred.

[0198]

[0199] In the structural formula (a-1), Ar T1 、Ar T2 , and Ar T3 Each independently represents a substituted or unsubstituted aryl, -C6H4-C(R T4 )=C(R T5 )(R T6 ), or -C6H4-CH=CH-CH=C(R T7 )(R T8 ). R T4 、R T5 、R T6 、R T7 , and R T8 Each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

[0200] Examples of substituents for the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. Examples of substituents for the above groups include substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms.

[0201]

[0202] In the 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 T112Each 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 ), 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.

[0203] Examples of substituents for the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. Examples of substituents for the above groups include substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms.

[0204] From the viewpoint of charge mobility, the triarylamine derivative represented by the structural formula (a-1) and the benzidine derivative represented by the structural formula (a-2) are particularly preferably the one having "-C6H4-CH=CH-CH=C(R T7 )(R T8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 )" benzidine derivatives.

[0205] As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane are used. In particular, polyester-based polymer charge transport materials are particularly preferred. The polymer charge transport material can be used alone or in combination with a binder resin.

[0206] The binder resin used in the charge transport layer can include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-modified alkyd resin, phenol-formaldehyde resin, styrene-modified alkyd resin (styrene-alkyd resin), poly-N-vinyl carbazole, polysilane, etc. Among them, as the binder resin, preferably polycarbonate resin or polyarylate resin. These binder resins are used alone or in combination.

[0207] The mixing ratio of the charge transport material and the binder resin is preferably 10:1 to 1:5 in terms of mass ratio.

[0208] The charge transport layer may contain other known additives.

[0209] The charge transport layer is formed by coating. Examples of coating methods include dissolving or dispersing a binder resin, a charge transport material, and inorganic oxide particles in a solvent to prepare a charge transport layer-forming coating solution, applying the charge transport layer-forming coating solution to the surface of the charge generating layer to form a coating film, and drying the coating film.

[0210] Examples of solvents used to prepare the charge transport layer coating solution include common organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanol; halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, and ethylene chloride; and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents can be used alone or in combination of two or more.

[0211] As a method for dispersing the inorganic oxide particles in the charge transport layer-forming coating liquid, 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 media-free disperser such as a stirrer, an ultrasonic disperser, a roll mill, or a high-pressure homogenizer is used.

[0212] Examples of the coating method for applying the charge transport layer-forming coating liquid onto the charge generating layer include common methods such as doctor blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0213] The thickness of the charge transport layer is preferably set to, for example, 5 μm or more and 50 μm or less, and more preferably set to be within the range of 10 μm or more and 30 μm or less.

[0214] [Inorganic protective layer]

[0215] The inorganic protective layer is an inorganic material layer. Examples of the inorganic material include metal oxides such as gallium oxide, aluminum oxide, zinc oxide, titanium dioxide, 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, amorphous hydrogenated carbon, hydrogen / fluorinated amorphous carbon, amorphous silicon carbide, amorphous hydrogenated silicon carbide, amorphous silicon, and amorphous hydrogenated silicon; and mixed crystals thereof.

[0216] From the viewpoint of 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 kind or two or more kinds.

[0217] From the viewpoint of maintaining the electrostatic latent image, the volume resistivity of the inorganic protective layer is preferably 1.0×10 10 Ω·cm or more, more preferably 1.0×10 11 Ω·cm or more.

[0218] The volume resistivity of the inorganic protective layer is measured as follows.

[0219] The inorganic protective layer was peeled off from the photoreceptor and used as a sample. The sample was clamped on the sample holder of an impedance analyzer (TOYO Corporation) and the resistance was measured at an AC voltage of 1 V and a frequency of 100 Hz. The resistance was calculated based on the electrode area and the sample thickness.

[0220] Examples of methods for forming the inorganic protective layer include known vapor phase film formation methods such as plasma CVD (Chemical Vapor Deposition), metal organic vapor phase growth, molecular beam epitaxy, evaporation, and sputtering. For example, the inorganic protective layer can be formed using the plasma CVD film formation apparatus and film formation conditions described in Japanese Patent Application Laid-Open No. 2014-191179.

[0221] From the viewpoint of 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.

[0222] The thickness of each layer of the photoreceptor was the arithmetic average of values ​​measured using an electromagnetic film thickness meter. The measurement locations were four locations at 90° intervals in the circumferential direction at the center of the axial direction of the photoreceptor.

[0223] [Single-layer photosensitive layer]

[0224] 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.

[0225] In a single-layer photosensitive layer, the content of the charge generating material is preferably from 0.1% to 10% by mass, more preferably from 0.8% to 5% by mass, relative to the total solids. In a single-layer photosensitive layer, the content of the charge transporting material is preferably from 5% to 50% by mass, relative to the total solids.

[0226] The single-layer photosensitive layer is formed by coating. Examples of coating methods include dissolving or dispersing a binder resin, a charge generating material, a charge transporting material, and inorganic oxide particles in a solvent to prepare a coating solution for forming a single-layer photosensitive layer, applying the coating solution to the surface of an undercoat layer or a conductive substrate to form a coating film, and drying the coating film. Details of the preparation and coating methods for the single-layer photosensitive layer coating solution are similar to those for the charge transport layer coating solution.

[0227] The thickness of the single-layer photosensitive layer is, for example, preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less.

[0228] <Image forming apparatus, process cartridge>

[0229] The image forming apparatus of this embodiment includes an electrophotographic photoreceptor, a charging device for charging the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photoreceptor, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor using a developer containing toner to form a toner image, and a transfer device for transferring the toner image to the surface of a recording medium. The electrophotographic photoreceptor of this embodiment is employed as the electrophotographic photoreceptor.

[0230] The image forming device of this embodiment applies the following well-known image forming devices: a device equipped with a fixing device for fixing the colorant image transferred to the surface of a recording medium; a device of a direct transfer method for directly transferring the colorant image formed on the surface of an electronic photographic photosensitive body to a recording medium; a device of an intermediate transfer method for transferring the colorant image formed on the surface of an electronic photographic photosensitive body to the surface of an intermediate transfer body for the first time, and transferring the colorant image transferred to the surface of the intermediate transfer body to the surface of a recording medium for the second time; a device equipped with a cleaning device for cleaning the surface of an electronic photographic photosensitive body after the transfer of the colorant image and before charging; a device equipped with an electrostatic elimination device for irradiating the surface of an electronic photographic photosensitive body with electrostatic elimination light for electrostatic elimination after the transfer of the colorant image and before charging; a device equipped with an electronic photographic photosensitive body heating component for increasing the temperature of the electronic photographic photosensitive body and reducing the relative temperature, etc.

[0231] In the case of an intermediate transfer method device, the transfer device, for example, has the following structure: an intermediate transfer body for transferring a colorant image on a surface, a primary transfer device for transferring the colorant image formed on the surface of the electronic photographic photosensitive body to the surface of the intermediate transfer body for the first time, and a secondary transfer device for secondary transferring the colorant image transferred to the surface of the intermediate transfer body to the surface of the recording medium.

[0232] The image forming apparatus of the present embodiment may be any of a dry development system image forming apparatus and a wet development system (development system using a liquid developer) image forming apparatus.

[0233] In the image forming apparatus of this embodiment, for example, the portion comprising the electrophotographic photoreceptor may be a toner cartridge structure (process cartridge) that is attachable to and detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge comprising the electrophotographic photoreceptor of this embodiment is preferably used. In addition to the electrophotographic photoreceptor, the process cartridge may also comprise, 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.

[0234] An example of the image forming apparatus according to the present embodiment is shown below, but the present invention is not limited thereto. The main parts shown in the drawings will be described, and description of the other parts will be omitted.

[0235] Figure 3 This is a schematic configuration diagram showing an example of the image forming apparatus according to the present embodiment.

[0236] like Figure 3As shown, the image forming apparatus 100 of this embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming device), a transfer device 40 (a primary transfer device), and an intermediate transfer member 50. In the image forming apparatus 100, the exposure device 9 is positioned so as to expose the electrophotographic photoreceptor 7 through the opening of the process cartridge 300. The transfer device 40 is positioned so as to face the electrophotographic photoreceptor 7 across the intermediate transfer member 50, with a portion of the intermediate transfer member 50 in contact with the electrophotographic photoreceptor 7. Although not shown, the image forming apparatus 100 further includes a secondary transfer device that transfers the toner image transferred to 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) constitute an example of a transfer device.

[0237] Figure 3 The process cartridge 300 in the embodiment of the present invention integrally supports the electrophotographic photoreceptor 7, the charging device 8 (an example of a charging device), the developing device 11 (an example of a developing device), and the cleaning device 13 (an example of a cleaning device) within a housing. The cleaning device 13 includes a cleaning blade (an example of a cleaning member) 131, which is arranged to contact the surface of the electrophotographic photoreceptor 7. The cleaning member may be a conductive or insulating fibrous member instead of the cleaning blade 131, and may be used alone or in combination with the cleaning blade 131.

[0238] exist Figure 3 2 shows an example in which a fibrous member 132 (roller-shaped) for supplying the lubricant 14 to the surface of the electrophotographic photoreceptor 7 and a fibrous member 133 (flat brush-shaped) for assisting cleaning are provided as the cleaning device, but these can be arranged as needed.

[0239] Next, each component of the image forming apparatus according to this embodiment will be described.

[0240] - Charging device -

[0241] As the charging device 8, for example, a contact charger using a conductive or semiconductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, etc. can be used. Alternatively, a non-contact roller charger, a scorotron charger using corona discharge, a corotron charger, or other known chargers can be used.

[0242] -Exposure device-

[0243] As the exposure device 9, for example, there can be cited an optical system device that exposes light such as semiconductor laser, LED light, liquid crystal shutter light to the surface of the electrophotographic photoreceptor 7 in a determined image shape. The wavelength of the light source is set within the spectral sensitivity area of ​​the electrophotographic photoreceptor. As the wavelength of the semiconductor laser, near-infrared with an oscillation wavelength around 780nm is the mainstream. However, it is not limited to this wavelength, and a laser with an oscillation wavelength of more than 600nm and less than 700nm, or a laser with an oscillation wavelength of more than 400nm and less than 450nm can also be used as a blue laser. In addition, a surface-emitting laser source that can output multiple beams in order to form a color image is also effective.

[0244] -Developing device-

[0245] Examples of the developing device 11 include general developing devices that develop the electrophotographic photoreceptor 7 with or without contacting the developer. The developing device 11 is not particularly limited as long as it has the functions described above, and can be selected based on the intended purpose. Examples include known developing devices that utilize a brush, roller, or the like to deposit a single-component developer or a two-component developer onto the electrophotographic photoreceptor 7. Among these, a developing roller that retains the developer on its surface is preferably used.

[0246] The developer used in the developing device 11 may be a single-component developer containing only toner or a two-component developer containing toner and a carrier. Furthermore, the developer may be magnetic or non-magnetic. These developers are known developers.

[0247] - Cleaning device -

[0248] The cleaning device 13 uses a cleaning blade type including a cleaning blade 131. In addition to the cleaning blade type, a brush cleaning method or a simultaneous development cleaning method may be used.

[0249] - Transfer device -

[0250] Examples of the transfer device 40 include known transfer chargers such as a contact transfer charger using a belt, a roller, a film, or a rubber blade, and a scorotron transfer charger or corotron transfer charger utilizing corona discharge.

[0251] -Intermediate transfer body-

[0252] As the intermediate transfer member 50, a belt-shaped intermediate transfer member (intermediate transfer belt) made of polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. imparted with semiconductivity is used. In addition, as the form of the intermediate transfer member, a drum-shaped intermediate transfer member can also be used in addition to the belt-shaped intermediate transfer member.

[0253] Figure 4This is a schematic structural diagram showing another example of the image forming apparatus according to the present embodiment.

[0254] Figure 4 The illustrated image forming apparatus 120 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In image forming apparatus 120, four process cartridges 300 are arranged side by side on an intermediate transfer body 50, with one electrophotographic photoreceptor used for each color. Aside from its tandem configuration, image forming apparatus 120 has the same structure as image forming apparatus 100.

[0255] [Example]

[0256] Hereinafter, 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.

[0257] In the following description, "parts" and "%" are based on mass unless otherwise specified.

[0258] In the following description, unless otherwise specified, synthesis, production, handling, measurement, etc. were performed at room temperature (25°C ± 3°C).

[0259] <Example 1>

[0260] [Formation of Primer Layer]

[0261] 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.

[0262] 100 parts of zinc oxide (average particle size 70 nm, specific surface area 15 m 2 / g, Tayca Co., Ltd.) and 500 parts of toluene were stirred and mixed, and 1.3 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. Subsequently, the toluene was distilled off under reduced pressure, and the mixture was calcined at 120°C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent.

[0263] 110 parts of surface-treated zinc oxide and 500 parts of tetrahydrofuran were stirred and mixed, and a solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran was added, followed by stirring at 50°C for 5 hours. The solid content was then filtered and separated by vacuum filtration and dried at 60°C under reduced pressure to obtain zinc oxide with alizarin added thereto.

[0264] 60 parts of alizarin-imparted zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, trade name: Sumidur 3175, Sumitomo Bayer Urethanes Co., Ltd.), and 15 parts of a butyral resin (trade name: S-LEC BM-1, Sekisui Chemical Co., Ltd.) were dissolved in 100 parts of a solution of 68 parts of methyl ethyl ketone and mixed with 5 parts of methyl ethyl ketone. The mixture was dispersed for 2 hours using a sand mill with 1 mm diameter glass beads to obtain a dispersion. 0.005 parts of dioctyltin dilaurate and 4 parts of silicone resin particles (trade name: TOSPEARL 145, Momentive Performance Materials) were added to the dispersion as catalysts to obtain a coating solution for forming a primer layer. The primer layer coating solution was applied to the outer peripheral surface of the conductive substrate by dip coating and dried and cured at 170°C for 40 minutes to form a 20 μm thick primer layer.

[0265] [Formation of Charge Generation Layer]

[0266] A mixture of 15 parts of hydroxygallium phthalocyanine (having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in the X-ray diffraction spectrum using CuKα characteristic X-rays) as a charge generating material, 10 parts of a vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, manufactured by Unicar Co., Ltd., Japan) as a binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill using glass beads having a diameter of 1 mm for 4 hours. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion, and the mixture was stirred to obtain a coating solution for forming a charge generating layer. The coating solution for forming a charge generating layer was dip-coated on the undercoat layer and dried at room temperature to form a charge generating layer having a thickness of 0.25 μm.

[0267] [Formation of Charge Transport Layer]

[0268] Binder resin: polycarbonate resin (1) (viscosity average molecular weight 40,000, the numerical values ​​in the structural formula represent molar ratio (mol %)) ··· 20 parts

[0269] Charge transport material: CTM-1···15 parts

[0270] Silica particles α (average particle size dα = 20 nm) hydrophobized with 1,1,1,3,3,3-hexamethyldisilazane ···The amount of silica particles α such that the volume ratio Vα of the charge transport layer is the volume % shown in Table 1

[0271] Silica particles β (average particle size dβ = 80 nm) hydrophobized with 1,1,1,3,3,3-hexamethyldisilazane ···The amount of silica particles β to achieve the volume ratio Vβ of the charge transport layer shown in Table 1

[0272] Solvent: Tetrahydrofuran (THF) 600 parts

[0273] The above materials were stirred and mixed for 12 hours to obtain a charge transport layer coating solution, which was then dip-coated onto the charge generating layer and the coating film was dried to form a charge transport layer having a thickness of 30 μm.

[0274] The volume fractions described here are calculated values ​​based on the weights of the polycarbonate resin, CTM-1, and silica particles added as materials. Specifically, the density of the polycarbonate resin (1) is set to 1.2 g / cm 3 , set the density of CTM-1 to 1.2 g / cm 3 , the density of silica particles is set to 2.2 g / cm 3 , calculate the individual volumes, and take the ratio of the volume of silica particles to the total volume as the volume ratio.

[0275]

[0276] Polycarbonate resin (1)

[0277]

[0278] [Formation of Inorganic Protective Layer]

[0279] An amorphous layer containing gallium oxide was formed as an inorganic protective layer by plasma CVD using trimethylgallium as a film-forming material. The layer thickness was set to 1 μm.

[0280] Through the above steps, a photoreceptor is obtained.

[0281] <Examples 2 to 15, Comparative Examples 1 to 6>

[0282] A photoreceptor was obtained in the same manner as in Example 1 except for the following changes: However, in Comparative Example 1, only one type of silica particles was used in the charge transport layer.

[0283] Average particle size dα and volume fraction Vα of silica particles α

[0284] Average particle size dβ and volume fraction Vβ of silica particles β

[0285] <Photoreceptor Characteristics Measurement>

[0286] According to the above-mentioned method, the cross section of the charge transport layer of the photoreceptor of each example was observed, and the following characteristics were measured.

[0287] The maximum peaks of the small-diameter particles A and the large-diameter particles B in the particle size distribution of the silica particles as the inorganic oxide particles

[0288] The area ratio of the silica particles as the inorganic oxide particles, and the area ratios of the small-diameter particles A and the large-diameter particles B in the silica particles

[0289] <Photoreceptor Performance Measurement>

[0290] [Hardness of the photosensitive layer]

[0291] The hardness of the surface of the photosensitive layer of the photoreceptor of each example was measured as follows.

[0292] First, a sample was obtained by peeling the inorganic protective layer from the photoreceptor of each example.

[0293] The hardness of the sample is the Young's modulus (GPa) determined by nanoindentation. The photoreceptor's axial direction is fixed horizontally, and the measurement is performed at the vertex in the center of the photoreceptor's axial direction. Four locations are measured at 90° intervals around the circumference of the photoreceptor, and the Young's modulus at these four locations is calculated as the arithmetic average. The measurement conditions based on the nanoindenter are as follows. The measurement results are shown in Table 1.

[0294] Test equipment: Trade name HM-500, Fischer Instruments Co., Ltd.

[0295] Indenter: Diamond triangular indenter with 115° angle

[0296] ·Load: 75mN

[0297] [Crack resistance of inorganic protective layer]

[0298] The load of cracks in the inorganic protective layer was measured as follows to evaluate the crack resistance of the inorganic protective layer.

[0299] The hardness test using a microhardness tester was repeated while increasing the load by 5 mN from 0 mN. Each time the load was applied, observation was performed using an optical microscope. The load at which damage occurred in the inorganic protective layer was defined as the crack initiation load. The measurement conditions are as follows. The measurement results are shown in Table 1.

[0300] Test device: Trade name DUH-201, Shimadzu Corporation

[0301] Indenter: Diamond ball indenter

[0302] [Table 1-1]

[0303]

[0304] [Table 1-2]

[0305]

[0306] The above results show that the inorganic protective layer of the photoreceptor of this example has higher crack resistance than the photoreceptor of the comparative example.

[0307] (Note) (((1)))

[0309] An electrophotographic photoreceptor, comprising:

[0310] Conductive substrate;

[0311] a photosensitive layer, the photosensitive layer being disposed on the conductive substrate and comprising inorganic oxide particles; and

[0312] an inorganic protective layer, the inorganic protective layer being disposed on the photosensitive layer,

[0313] In the particle size distribution of the inorganic oxide particles obtained by observing the cross section of the photosensitive layer, with the particle size of 60 nm as the boundary, the maximum peak of the small-diameter side particles A exists in the range of greater than 20 nm and less than 50 nm, and the maximum peak of the large-diameter side particles B exists in the range of greater than 80 nm and less than 400 nm, and the relationship between the particle size dA of the maximum peak of the small-diameter side particles A and the particle size dB of the maximum peak of the large-diameter side particles B satisfies the following formula (A1).

[0314] Formula (A1): dB / dA ≥ 4.0 (((2)))

[0316] The electrophotographic photoreceptor according to (((1))), wherein

[0317] 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).

[0318] Formula (A2): dB / dA ≥ 6.0 (((3)))

[0320] The electrophotographic photoreceptor according to (((1))) or (((2))), wherein

[0321] In the area ratio of the inorganic oxide particles obtained by observing the 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).

[0322] Formula (B1): VB / (VA+VB)×100≥60% (((4)))

[0324] The electrophotographic photoreceptor according to (((3))), wherein

[0325] The relationship between the area ratio VA of the small-diameter side particles A and the area ratio VB of the large-diameter side particles B satisfies the following formula (B2).

[0326] Formula (B2): VB / (VA+VB)×100≥70% (((5)))

[0328] The electrophotographic photoreceptor according to any one of (((1))) to (((4))), wherein

[0329] 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. (((6)))

[0331] The electrophotographic photoreceptor according to (((5))), wherein

[0332] 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. (((7)))

[0334] The electrophotographic photoreceptor according to any one of (((1))) to (((6))), wherein

[0335] The inorganic oxide particles are silicon dioxide particles. (((8)))

[0337] The electrophotographic photoreceptor according to any one of (((1))) to (((7))), wherein

[0338] The inorganic protective layer is a layer containing gallium oxide. (((9)))

[0340] An electrophotographic photoreceptor, comprising:

[0341] Conductive substrate;

[0342] a photosensitive layer, the photosensitive layer being disposed on the conductive substrate and comprising inorganic oxide particles; and

[0343] an inorganic protective layer, the inorganic protective layer being disposed on the photosensitive layer,

[0344] The inorganic oxide particles include inorganic oxide particles α having an average particle size of 20 nm to 50 nm inclusive and inorganic oxide particles β having an average particle size of 80 nm to 400 nm inclusive.

[0345] 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 following formula (α1).

[0346] Formula (α1): dβ / dα≥4.0 (((10)))

[0348] A process cartridge comprising the electrophotographic photoreceptor described in any one of (((1))) to (((9))),

[0349] The process cartridge is attachable to and detachable from the image forming apparatus. (((11)))

[0351] An image forming apparatus comprising:

[0352] The electrophotographic photoreceptor according to any one of (((1))) to (((9)));

[0353] a charging device for charging the surface of the electrophotographic photoreceptor;

[0354] an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor;

[0355] a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image; and

[0356] A transfer device transfers the toner image to a surface of a recording medium.

[0357] According to the invention of (((1))), there is provided an electronic photographic photoreceptor comprising: a conductive substrate; a photosensitive layer, the photosensitive layer being arranged on the conductive substrate and comprising inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being arranged on the photosensitive layer, wherein the crack resistance of the inorganic protective layer is improved compared with the following situation: in the particle size distribution of the inorganic oxide particles obtained by observing the cross section of the photosensitive layer, with a particle size of 60 nm as the boundary, the maximum peak of the small-diameter side particles A exists in the range of greater than 20 nm and less than 50 nm, and the maximum peak of the large-diameter side particles B exists in the range of greater than 80 nm and less than 400 nm, and the relationship between the particle size dA of the maximum peak of the small-diameter side particles A and the particle size dB of the maximum peak of the large-diameter side particles B does not satisfy formula (A1).

[0358] According to (((2))), there is provided an electrophotographic photoreceptor having an improved crack resistance of the inorganic protective layer compared to a case where the formula (A2) is not satisfied.

[0359] According to (((3))), there is provided an electrophotographic photoreceptor having an improved crack resistance of the inorganic protective layer compared to a case where the formula (B1) is not satisfied.

[0360] According to (((4))), there is provided an electrophotographic photoreceptor having an improved crack resistance of the inorganic protective layer compared to a case where the formula (B2) is not satisfied.

[0361] According to (((5))), there is provided an electrophotographic photoreceptor having an improved crack resistance of an inorganic protective layer compared to a case where the area ratio of inorganic oxide particles is less than 50% or exceeds 90%.

[0362] According to (((6))), an electrophotographic photoreceptor is provided in which the crack resistance of the inorganic protective layer is improved compared with a case where the area ratio of the inorganic oxide particles is less than 60% or exceeds 80%.

[0363] According to (((7))), there is provided an electrophotographic photoreceptor having a photosensitive layer containing silica particles as inorganic oxide particles, wherein the crack resistance of the inorganic protective layer is improved compared to a case where the formula (A1) is not satisfied.

[0364] According to (((8))), there is provided an electrophotographic photoreceptor in which the crack resistance of the inorganic protective layer containing gallium oxide is improved compared to a case where the formula (A1) is not satisfied.

[0365] According to (((9))), an electronic photographic photoreceptor is provided, comprising: a conductive substrate; a photosensitive layer, the photosensitive layer being arranged on the conductive substrate and comprising inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being arranged on the photosensitive layer, the inorganic oxide particles comprising inorganic oxide particles α having an average particle size of greater than 20 nm and less than 50 nm and inorganic oxide particles β having an average particle size of greater than 80 nm and less than 400 nm, wherein the crack resistance of the inorganic protective layer is improved compared with a case where 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).

[0366] According to (((10))) or (((11))), there is provided a processing box or image forming device having an electronic photographic photoreceptor, wherein the crack resistance of the inorganic protective layer is improved compared with the case of having the following electronic photographic photoreceptor: comprising: a conductive substrate; a photosensitive layer, the photosensitive layer being arranged on the conductive substrate and containing inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being arranged on the photosensitive layer, wherein, in the particle size distribution of the inorganic oxide particles obtained by observing the cross section of the photosensitive layer, with a particle size of 60 nm as the boundary, the maximum peak of the small-diameter side particles A exists in the range of greater than 20 nm and less than 50 nm, and the maximum peak of the large-diameter side particles B exists in the range of greater than 80 nm and less than 400 nm, and the relationship between the particle size dA of the maximum peak of the small-diameter side particles A and the particle size dB of the maximum peak of the large-diameter side particles B does not satisfy formula (A1).

Claims

1. An electrophotographic photoreceptor, characterized in that have: Conductive substrate; a photosensitive layer, the photosensitive layer being disposed on the conductive substrate and comprising inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being disposed on the photosensitive layer, In the particle size distribution of the inorganic oxide particles obtained by observing a cross section of the photosensitive layer, with a particle diameter of 60 nm as a boundary, the maximum peak of the small-diameter side particles A exists in a range of 20 nm to 50 nm, and the maximum peak of the large-diameter side particles B exists in a range of 80 nm to 400 nm, and the relationship between the particle diameter dA of the maximum peak of the small-diameter side particles A and the particle diameter dB of the maximum peak of the large-diameter side particles B satisfies the following formula (A1): Formula (A1): dB / dA ≥ 4.

0.

2. The electrophotographic photoreceptor according to claim 1, wherein The relationship between the maximum peak particle size dA of the small-diameter side particles A and the maximum peak particle size dB of the large-diameter side particles B satisfies the following formula (A2): Formula (A2): dB / dA ≥ 6.

0.

3. The electrophotographic photoreceptor according to claim 1 or 2, wherein In the area ratio of the inorganic oxide particles obtained by observing the 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): Formula (B1): VB / (VA+VB)×100≥60%.

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

5. The electrophotographic photoreceptor according to any one of claims 1 to 4, wherein 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.

6. The electrophotographic photoreceptor according to claim 5, wherein 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.

7. The electrophotographic photoreceptor according to any one of claims 1 to 6, wherein The inorganic oxide particles are silicon dioxide particles.

8. The electrophotographic photoreceptor according to any one of claims 1 to 7, wherein The inorganic protective layer is a layer containing gallium oxide.

9. An electrophotographic photoreceptor, characterized in that: have: Conductive substrate; a photosensitive layer, the photosensitive layer being disposed on the conductive substrate and comprising inorganic oxide particles; and an inorganic protective layer, the inorganic protective layer being disposed on the photosensitive layer, The inorganic oxide particles include inorganic oxide particles α having an average particle size of 20 nm to 50 nm inclusive and inorganic oxide particles β having an average particle size of 80 nm to 400 nm inclusive. 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 following formula (α1): Formula (α1): dβ / dα≥4.

0.

10. A processing cartridge, characterized in that: An electrophotographic photoreceptor according to any one of claims 1 to 9, The process cartridge is attachable to and detachable from the image forming apparatus.

11. An image forming apparatus, characterized in that: have: The electrophotographic photoreceptor according to any one of claims 1 to 9; a charging device for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photoreceptor using a developer containing toner to form a toner image; as well as A transfer device transfers the toner image to a surface of a recording medium.

Images