Electrophotographic photoreceptor and electrophotographic image forming apparatus

Abstract

The object of the present invention is to provide an electrophotographic photoreceptor that achieves both wear resistance and cleaning performance during long-term use, and an electrophotographic image forming apparatus using the same. [Solution] An electrophotographic photoreceptor comprising at least a charge generation layer, a charge transport layer, and a protective layer sequentially laminated on a conductive support, wherein the protective layer is a cured film formed from a cured product of a compound containing inorganic fine particles and having polymerizable functional groups, the protective layer having a first region and a second region in that order from the outermost surface, and when the thickness of the protective layer is L, the thickness of the first region is 0.2L and the thickness of the second region is 0.8L, and the area ratio F1[%] of the inorganic fine particles in the cross-section of the first region when the protective layer is cut in the thickness direction is smaller than the area ratio F2[%] of the inorganic fine particles in the cross-section of the second region.

Description

Technical Field

[0001] The present invention relates to an electrophotographic photoreceptor and an electrophotographic image forming system. More specifically, it relates to an electrophotographic photoreceptor that achieves both wear resistance and cleaning performance during long-term use.

Background Art

[0002] In recent years, there has been a demand for high durability (long life) of electrophotographic photoreceptors. Conventionally, in order to improve the durability of electrophotographic photoreceptors, there is a technique of providing a protective layer on the outermost surface of the electrophotographic photoreceptor to improve wear resistance. For example, in Patent Document 1, an electrophotographic photoreceptor having a protective layer using a crosslinked polymer polymer containing inorganic fine particles is used, thereby improving wear resistance.

[0003] However, an electrophotographic photoreceptor having a protective layer as described above is likely to cause cleaning defects such as filming on the surface of the electrophotographic photoreceptor during long-term use, which is particularly remarkable in a system where a lubricant is externally added to the toner. Here, the "system" refers to the part being focused on as the object of consideration.

[0004] As described above, in the technology related to conventional electrophotographic photoreceptors, it has not been possible to sufficiently achieve both high durability performance and excellent cleaning performance, and further technological improvement has been desired.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above problems and situations, and the problem to be solved is to provide an electrophotographic photoreceptor that achieves both wear resistance and cleaning performance in long-term use, and an electrophotographic image forming apparatus using the same.

Means for Solving the Problem

[0007] In an electrophotographic photoreceptor having a protective layer containing a cured product of a compound having a polymerizable functional group and inorganic fine particles, it has been found that the above problem can be solved by reducing the content ratio of the inorganic fine particles in the region on the outermost surface side of the protective layer. That is, the above problems according to the present invention are solved by the following means.

[0008] 1. An electrophotographic photoreceptor obtained by sequentially laminating at least a charge generation layer, a charge transport layer, and a protective layer on a conductive support, where the protective layer is a cured film formed of a cured product of a compound having a polymerizable functional group and containing inorganic fine particles, the protective layer has a first region and a second region in this order from the outermost surface side, [[ID= nineteen]]When the thickness of the protective layer is L, the thickness of the first region is 0.2L, and the thickness of the second region is 0.8L, when the protective layer is cut in the thickness direction, the area ratio F1 [%] of the inorganic fine particles in the cross section of the first region and the area ratio F2 [%] of the inorganic fine particles in the cross section of the second region satisfy the relationship of the following formula (1) F1 < F2 Formula (1) An electrophotographic photoreceptor characterized by the above.

[0009] 2. The primary average particle diameter of the inorganic fine particles is in the range of 100 to 700 nm The electrophotographic photoreceptor according to claim 1, characterized by the above.

[0010] 3. The area ratio F1 [%] is 20% or more The electrophotographic photoreceptor according to claim 1, characterized by the above.

[0011] 4. The area ratio F1 [%] and the area ratio F2 [%] satisfy the relationship of the following formula (2). The electrophotographic photoreceptor according to claim 1, characterized in that. F1 < 0.9 × F2 Formula (2)

[0012] 5. The inorganic fine particles are silica fine particles. The electrophotographic photoreceptor according to claim 1, characterized in that.

[0013] 6. The compound having a polymerizable functional group is a charge transporting compound having a chain polymerizable functional group. The electrophotographic photoreceptor according to claim 1, characterized in that.

[0014] 7. The charge transporting compound has a structure represented by the following general formula (1). The electrophotographic photoreceptor according to claim 6, characterized in that.

Chemical formula

[0015] 8. An electrophotographic image forming apparatus provided with a lubricant supply means, Comprising the electrophotographic photoreceptor according to any one of claims 1 to 7, The lubricant supply means is a means for adding a lubricant to toner for electrostatic charge image development and supplying it onto the electrophotographic photoreceptor. The electrophotographic image forming apparatus, characterized in that.

Advantages of the Invention

[0016] By the above means of the present invention, it is possible to provide an electrophotographic photoreceptor that achieves both wear resistance and cleaning performance in long-term use, and an electrophotographic image forming apparatus using the same.

[0017] Although the mechanism of manifestation or the mechanism of action of the effects of the present invention is not clearly understood, it is presumed as follows.

[0018] The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor in which at least a charge generation layer, a charge transport layer, and a protective layer are sequentially laminated on a conductive support, wherein the protective layer is a cured film formed of a cured product of a compound containing inorganic fine particles and having a polymerizable functional group, the protective layer has a first region and a second region in this order from the outermost surface side, and when the thickness of the protective layer is L, the thickness of the first region is 0.2L and the thickness of the second region is 0.8L, and the area ratio F1 [%] of the inorganic fine particles in the cross section of the first region and the area ratio F2 [%] of the inorganic fine particles in the cross section of the second region when the protective layer is cut in the thickness direction satisfy the relationship of the formula (1). Hereinafter, the "electrophotographic photoreceptor" is also simply referred to as the "photoreceptor".

[0019] For example, since a new photoreceptor has a small surface roughness, when cleaning the photoreceptor, the friction with the cleaning blade increases, the rotation torque of the photoreceptor drum unit increases, and there is a tendency to enter a high torque state. Hereinafter, such a "high torque state" is also referred to as an "unstable state". Also, the "photoreceptor drum unit" is also simply referred to as the "photoreceptor".

[0020] When the photoreceptor enters the high torque state as described above, the cleaning blade is likely to vibrate, and the performance of removing deposits on the photoreceptor by the cleaning blade deteriorates. Then, the deposits on the photoreceptor become film formation nuclei, and film formation is likely to occur.

[0021] Over time, as the photoreceptor is used and the number of printed pages increases, the surface of the photoreceptor gradually wears down, increasing its surface roughness. This reduces the friction between the photoreceptor and the cleaning blade during cleaning, which in turn suppresses the vibration of the cleaning blade and improves the cleaning blade's ability to remove deposits from the photoreceptor. Hereafter, this state in which "friction between the photoreceptor and the cleaning blade is reduced, and consequently the vibration of the cleaning blade is suppressed" will also be referred to as the "stable state."

[0022] When a new photoreceptor is used, it is in an unstable state as described above. However, when using the photoreceptor, it is desirable for it to reach a stable state as quickly as possible. In order to transition quickly from an unstable state to a stable state, it is necessary to moderately reduce the wear resistance of the photoreceptor protective layer.

[0023] In the present invention, an electrophotographic photoreceptor having a protective layer containing a cured product of a compound having polymerizable functional groups and inorganic fine particles, wherein the content of the inorganic fine particles is reduced in the region on the outermost surface side of the protective layer.

[0024] This provides the photoreceptor with an appropriate roughness even in the initial stages of use, which reduces friction between the photoreceptor and the cleaning blade, as well as suppresses vibration of the cleaning blade, thereby preventing filming from occurring.

[0025] Furthermore, once the photoreceptor has been given an appropriate roughness, the cleaning performance stabilizes even with minimal photoreceptor wear, making it possible to slow down the wear rate of the region containing a large amount of inorganic fine particles on the substrate side (opposite the outermost surface) of the protective layer of the photoreceptor.

[0026] As a result, it is presumed that good cleaning performance can be ensured throughout the entire period of use of the photoreceptor, thereby extending the lifespan of the photoreceptor. [Brief explanation of the drawing]

[0027] [Figure 1]Cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor of the present invention [Figure 2] Schematic cross-sectional view of the protective layer of the electrophotographic photoreceptor of the present invention in the thickness direction [Figure 3] Explanatory cross-sectional view showing an example of the configuration of the image forming apparatus according to the present invention

Mode for Carrying Out the Invention

[0028] The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor in which at least a charge generation layer, a charge transport layer, and a protective layer are sequentially laminated on a conductive support, wherein the protective layer contains inorganic fine particles and is a cured film formed from a cured product of a compound having a polymerizable functional group. The protective layer has a first region and a second region in this order from the outermost surface side. When the thickness of the protective layer is L, the thickness of the first region is 0.2L, and the thickness of the second region is 0.8L. The area ratio F1 [%] of the inorganic fine particles in the cross section of the first region when the protective layer is cut in the thickness direction and the area ratio F2 [%] of the inorganic fine particles in the cross section of the second region satisfy the relationship of the following formula (1). F1 < F2 Formula (1) It is characterized by this. This feature is a common or corresponding technical feature in each of the following embodiments (aspects).

[0029] As an embodiment of the present invention, it is preferable that the primary average particle diameter of the inorganic fine particles is in the range of 100 to 700 nm from the viewpoint of improving the filming resistance and from the viewpoint that the inorganic fine particles are less likely to settle during storage of the coating liquid for forming the protective layer.

[0030] It is preferable that the area ratio F1 [%] is 20% or more from the viewpoints of improving the abrasion resistance and the filming resistance.

[0031] It is preferable that the area ratio F1 [%] and the area ratio F2 [%] satisfy the relationship of the following formula (2) from the viewpoint of improving the filming resistance. F1 < 0.9 × F2 Formula (2)

[0032] From the viewpoint of suppressing the generation of image memory, it is preferable that the inorganic fine particles are silica fine particles.

[0033] From the viewpoint of improving charge transport performance, it is preferable that the compound having the polymerizable functional group is a charge transport compound having a chain polymerizable functional group.

[0034] From the viewpoint of suppressing a decrease in charge transport performance, it is preferable that the charge transport compound has a structure represented by the following general formula (1).

[0035] The electrophotographic photoreceptor of the present invention can be suitably used in an electrophotographic photoreceptor that includes a lubricant supply means for supplying a lubricant added to a toner for developing electrostatic images onto the electrophotographic photoreceptor.

[0036] The present invention, its components, and embodiments and models for carrying out the present invention will be described in detail below. In this application, "~" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0037] While the advantages and features provided by one or more embodiments of the present invention will be better understood from the following detailed description and accompanying drawings, these drawings are for illustrative purposes only and are not intended to define any limitations of the present invention.

[0038] [I. Electrophotographic photoreceptor] 1. Overview The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor formed by sequentially laminating at least a charge generation layer, a charge transport layer, and a protective layer on a conductive support, wherein the protective layer contains inorganic fine particles and is a cured film formed from a cured product of a compound having a polymerizable functional group. The protective layer has a first region and a second region in this order from the outermost surface side. When the thickness of the protective layer is L, the thickness of the first region is 0.2L, and the thickness of the second region is 0.8L. The area ratio F1 [%] of the inorganic fine particles in the cross-section of the first region when the protective layer is cut in the thickness direction and the area ratio F2 [%] of the inorganic fine particles in the cross-section of the second region satisfy the relationship of the following formula (1). F1 < F2 Formula (1)

[0039] Note that the electrophotographic photoreceptor of the present invention may further include other layers in addition to the above-mentioned each layer. Examples of other layers include an intermediate layer laminated on the conductive support. The intermediate layer has, for example, a barrier function and an adhesion function.

[0040] The electrophotographic photoreceptor of the present invention is an organic photoreceptor. The "organic photoreceptor" means an electrophotographic photoreceptor in which at least one of the charge generation function and the charge transport function essential for the structure of the electrophotographic photoreceptor is exhibited by an organic compound. In addition, the meaning of the electrophotographic photoreceptor includes a photoreceptor composed of a known organic charge generating substance or an organic charge transporting substance, a photoreceptor in which the charge generation function and the charge transport function are composed of a polymer complex, and the like.

[0041] Examples of the specific layer structure of the photoreceptor of the present invention are shown below. In this specification, the "photosensitive layer" means a layer including at least a charge generation layer, a charge transport layer, and a protective layer other than the conductive support in the following layer structure example, and an intermediate layer may further be included as a layer constituting the photosensitive layer. The layer structure of the photoreceptor may be any of the layer structures (1) to (4) below, and among these, the layer structure of (3) below is particularly preferable.

[0042] (1) Conductive support / Charge generation layer / Charge transport layer / Protective layer (2) Conductive support / charge transport layer / protective layer that also serves as a charge generation layer (3) Conductive support / intermediate layer / charge generation layer / charge transport layer / protective layer (4) Conductive support / intermediate layer / charge transport layer that also serves as a charge generation layer / protective layer

[0043] Figure 1 is a cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor of the present invention. In the electrophotographic photoreceptor 1 shown in Figure 1, an intermediate layer 102, a charge generation layer 103, a charge transport layer 104, and a protective layer 105 are sequentially laminated on a conductive support 101. The photosensitive layer 106 includes the intermediate layer 102, the charge generation layer 103, the charge transport layer 104, and the protective layer 105.

[0044] Hereinafter, the protective layer, which is an important component of the electrophotographic photoreceptor of the present invention, will be described first, followed by the conductive support, intermediate layer, charge generation layer, and charge transport layer in that order.

[0045] 2.Protective layer The protective layer according to the present invention is obtained by preparing a protective layer-forming coating solution by mixing inorganic fine particles, a compound having polymerizable functional groups, and other components in a solvent, applying the protective layer-forming coating solution onto a charge transport layer, drying and curing it, and forming a resin layer.

[0046] For example, when metal oxide particles surface-modified to have radical polymerizable functional groups are used as the inorganic fine particles, the following three reactions proceed in a mixture during the above process, forming a protective resin layer.

[0047] (1) Reactions between radical polymerizable functional groups of metal oxide particles (2) Reaction of radical polymerizable functional groups with compounds having polymerizable functional groups (3) Reactions between compounds having polymerizable functional groups

[0048] In the present specification, the "coating liquid for forming a protective layer" is also referred to as the "composition for forming a protective layer". Further, the resin component in the protective layer may be regarded as being constituted by all of the polymerizable compounds contained in the coating liquid for forming a protective layer undergoing a curing reaction.

[0049] (2.1) Inorganic fine particles (Proportion of existence in the cross-section) Since the protective layer according to the present invention contains inorganic fine particles, it has excellent abrasion resistance. FIG. 2 is a schematic cross-sectional view in the thickness direction of the protective layer of the electrophotographic photoreceptor of the present invention.

[0050] The protective layer according to the present invention is considered by dividing it into a first region and a second region in this order from the outermost surface side. At this time, the thickness of the protective layer is "L", the thickness of the first region is "0.2L", and the thickness of the second region is "0.8L".

[0051] In FIG. 2, "S1" is the cross-section of the first region, and "S2" is the cross-section of the second region. In the present specification, the "outermost surface of the photoreceptor" means the "outermost surface of the protective layer". Further, the "outermost surface of the photoreceptor" means the "surface on the opposite side of the conductive support" in the protective layer. Note that the "outermost surface of the photoreceptor" and the "outermost surface of the protective layer" mean the same thing.

[0052] When the outermost surface of the protective layer is set as the depth h = 0 and the boundary between the protective layer and the charge transport layer is set as the depth h = 1.0L, the first region according to the present invention is a region within the range of the depth h = 0 to 0.2L. Further, the second region according to the present invention is a region within the range of the depth h = 0.2 to 1.0L. In the present specification, the region of the depth h = 0.2L is positioned as the boundary between the first region and the second region.

[0053] In the present invention, the area ratio F1 [%] of the inorganic fine particles in the cross-section of the first region and the area ratio F2 [%] of the inorganic fine particles in the cross-section of the second region satisfy the relationship of the following formula (1). F1 < F2 Formula (1)

[0054] Furthermore, satisfying equation (1) above means that the inorganic fine particle content in the second region on the side opposite the outermost surface of the protective layer according to the present invention, i.e., on the substrate side (conductive support side) of the protective layer, is higher than in the first region. This imparts an appropriate roughness to the photoreceptor surface.

[0055] As a result, it is presumed that good cleaning performance can be ensured throughout the entire period of use of the photoreceptor, thereby extending the lifespan of the photoreceptor.

[0056] From the viewpoint of improving abrasion resistance and filming resistance, it is preferable that the area ratio F1[%] of inorganic fine particles in the cross-section of the first region is 20% or more. When the area ratio F1 is 20% or more, sufficient abrasion resistance and filming resistance can be obtained even in a lubricant toner external addition system with a relatively small amount of lubricant on the photoreceptor. If the area ratio F1 is less than 80%, the protective layer will not become brittle and its strength can be maintained to a certain extent.

[0057] If the inorganic fine particles become densely packed in the protective layer, they will not be able to be unevenly distributed, making it difficult to satisfy the relationship in equation (1) described above. For this reason, it is preferable that the area ratio F1[%] and the area ratio F2[%] are 50% or less.

[0058] From the viewpoint of improving filming resistance, it is preferable that the area ratio F1[%] and the area ratio F2[%] satisfy the relationship shown in the following formula (2). F1<0.9×F2 Formula (2)

[0059] When the area ratio F1[%] and the area ratio F2[%] satisfy the relationship in equation (2) above, the proportion of inorganic fine particles on the surface side of the protective layer becomes smaller.

[0060] As the photoreceptor is used, its surface roughness increases. However, as described above, the decreasing proportion of inorganic fine particles on the surface side of the protective layer leads to a greater rate of increase in surface roughness in the initial stages of use.

[0061] As a result, the cleaning blade transitions to a stable state with less vibration more quickly, improving its filming resistance.

[0062] (kinds) The inorganic fine particles according to the present invention are not particularly limited as long as they are compounds that are stable in the atmosphere, but it is preferable from the viewpoint of wear resistance that the inorganic fine particles are metal oxide particles. Furthermore, it is preferable that the inorganic fine particles are insulating oxide particles.

[0063] Examples of insulating oxide particles include silica, alumina, magnesium oxide, zirconium oxide, and calcium titanate. In particular, it is preferable that the inorganic fine particles according to the present invention are silica fine particles from the viewpoint of suppressing the generation of image memory.

[0064] Silica nanoparticles have a relatively low dielectric constant of 3.8 among inorganic nanoparticles, making them less likely to hinder charge transport in the protective layer. Furthermore, from the viewpoint of dispersibility in the binder resin, it is particularly preferable to surface treat the silica nanoparticles to make them hydrophobic.

[0065] Preferably, the metal oxide particles described above are surface-modified with a surface modifier so that a surface is obtained having a functional group that reacts with a charge-transporting compound having a chain-polymerizable functional group and / or a polymerizable compound containing a trifunctional or higher polymerizable monomer.

[0066] As a result, the surface-modified metal oxide particles can react with polymerizable compounds during protective layer formation. This allows the metal oxide particles to be fixed to the matrix, forming a stronger protective layer.

[0067] The surface modifier preferably has a functional group that reacts with the hydroxyl group on the surface of the metal oxide particles, in addition to a functional group that reacts with the polymerizable compound. Examples of functional groups that react with the hydroxyl group on the surface of the metal oxide particles include hydrolyzable silyl groups. Examples of such surface modifiers include silane coupling agents and titanium coupling agents.

[0068] For example, if the polymerizable group of a polymerizable compound is an addition-polymerizable functional group, it is preferable to use a silane coupling agent having an addition-polymerizable functional group and a hydrolyzable silyl group as the surface modifier. Examples of such surface modifiers include the compounds listed below.

[0069] S-1 CH2=CHSi(CH3)(OCH3)2 S-2 CH2=CHSi(OCH3)3 S-3 CH2=CHSiCl3 S-4 CH2=CHCOO(CH2)2Si(CH3)(OCH3)2 S-5 CH2=CHCOO(CH2)2Si(OCH3)3 S-6 CH2=CHCOO(CH2)3Si(CH3)(OCH3)2 S-7 CH2=CHCOO(CH2)3Si(OCH3)3 S-8 CH2=CHCOO(CH2)2Si(CH3)Cl2 S-9 CH2=CHCOO(CH2)2SiCl3 S-10 CH2=CHCOO(CH2)3Si(CH3)Cl2 S-11 CH2=CHCOO(CH2)3SiCl3 S-12 CH2=C(CH3)COO(CH2)2Si(CH3)(OCH3)2 S-13 CH2=C(CH3)COO(CH2)2Si(OCH3)3 S-14 CH2=C(CH3)COO(CH2)3Si(CH3)(OCH3)2 S-15 CH2=C(CH3)COO(CH2)3Si(OCH3)3 S-16 CH2=C(CH3)COO(CH2)2Si(CH3)Cl2 S-17 CH2=C(CH3)COO(CH2)2SiCl3 S-18 CH2=C(CH3)COO(CH2)3Si(CH3)Cl2 S-19 CH2=C(CH3)COO(CH2)3SiCl3 S-20 CH2=CHSi(C2H5)(OCH3)2 S-21 CH2=C(CH3)Si(OCH3)3 S-22 CH2=C(CH3)Si(OC2H5)3 S-23 CH2=CHSi(OCH3)3 S-24 CH2=C(CH3)Si(CH3)(OCH3)2 S-25 CH2=CHSi(CH3)Cl2 S-26 CH2=CHCOOSi(OCH3)3 S-27 CH2=CHCOOSi(OC2H5)3 S-28 CH2=C(CH3)COOSi(OCH3)3 S-29 CH2=C(CH3)COOSi(OC2H5)3 S-30 CH2=C(CH3)COO(CH2)3Si(OC2H5)3

[0070] [ka]

[0071] These surface modifiers can be used individually or in combination of two or more. While there are no particular restrictions on the amount of surface modifier used, it is preferable that it be in the range of 0.1 to 100 parts by mass per 100 parts by mass of metal oxide particles before surface modification.

[0072] Specifically, surface modification of metal oxide particles can be performed by wet grinding a slurry containing metal oxide particles and a surface modifier to refine the metal oxide particles while simultaneously advancing the surface modification, and then removing the solvent to produce a powder. A "slurry" is a suspension of solid particles.

[0073] One type of apparatus used for wet grinding of slurries is a wet media dispersion apparatus. A wet media dispersion apparatus is an apparatus that has a process of crushing, grinding, and dispersing aggregated metal oxide particles by filling a container with beads as media and then rotating a stirring disc mounted perpendicular to the rotating shaft at high speed.

[0074] The configuration of a wet media dispersion apparatus is acceptable as long as it can sufficiently disperse metal oxide particles and perform surface modification on them. For example, various types can be used, such as vertical or horizontal, continuous or batch-type.

[0075] Specifically, sand mills, ultravisco mills, pearl mills, grain mills, dyno mills, agitator mills, dynamic mills, etc., can be used. These dispersion devices use grinding media such as balls and beads to perform fine grinding and dispersion by impact crushing, friction, shear, shear stress, etc.

[0076] For use in a wet media dispersion apparatus, beads made from materials such as glass, alumina, zircon, zirconia, steel, and flint can be used, but it is particularly preferable to use beads made of zirconia or zircon. While beads with a diameter of approximately 1-2 mm are typically used, when implementing the present invention, it is preferable to use beads with a diameter of approximately 0.1-1.0 mm.

[0077] Various materials can be used for the discs and inner walls of containers used in wet media dispersion apparatuses, such as stainless steel, nylon, and ceramic. In particular, discs and inner walls of ceramics such as zirconia or silicon carbide are preferred.

[0078] (particle size) It is preferable that the primary average particle size of the inorganic fine particles is within the range of 100 to 700 nm, from the viewpoint of improving filming resistance and from the viewpoint of preventing the inorganic fine particles from settling during storage of the coating liquid for forming the protective layer.

[0079] If the primary average particle size of the inorganic microparticles is 100 nm or larger, the microscopic surface irregularities on the photoreceptor surface increase, further improving filming resistance. Furthermore, if the primary average particle size of the inorganic microparticles is 700 nm or smaller, the inorganic microparticles are less likely to settle during storage of the protective layer-forming coating solution.

[0080] Assuming that the particle diameter is the same as the diameter of a circle with the same area as the projected area of ​​the inorganic microparticles projected from the cross-sectional SEM image in the thickness direction of the protective layer, the average value of this circle is taken as the primary mean particle size of the inorganic microparticles. The primary mean particle size (number mean primary particle size) of inorganic microparticles can be calculated, for example, as follows.

[0081] First, a 10,000x magnified image is taken using a scanning electron microscope (manufactured by JEOL). Next, 300 randomly selected particles are captured by the scanner, and the resulting image (excluding aggregated particles) is binarized using the "LUZEX AP (registered trademark) AP" automated image processing and analysis system software Ver. 1.32 manufactured by Nireco Corporation.

[0082] From the binarized photographic images, the horizontal Ferret diameter is calculated for each image, and the average value is calculated as the number-mean primary particle size. Here, the horizontal Ferret diameter refers to the length of the side parallel to the x-axis of the circumscribing rectangle when the image of inorganic microparticles is binarized.

[0083] (Content ratio) The content of inorganic fine particles is preferably in the range of 1 to 100 parts by mass, and more preferably in the range of 5 to 80 parts by mass, per 100 parts by mass of the total amount of compounds having polymerizable functional groups.

[0084] By keeping the inorganic fine particle content within the above range, it becomes possible to sufficiently satisfy the requirements for hardness and light transmittance of the protective layer.

[0085] If the inorganic fine particle content is 1 part by mass or more, further wear resistance can be obtained by improving the hardness of the protective layer. If it is 100 parts by mass or less, the impact on latent image formation due to reduced light transmittance and the occurrence of image defects due to aggregation of inorganic fine particles become less likely.

[0086] (2.2) Cured products of compounds having polymerizable functional groups In forming the protective layer according to the present invention, a protective layer-forming composition containing inorganic fine particles and a compound having polymerizable functional groups is prepared, applied to a charge transport layer, and dried to cure. Depending on the desired application, the protective layer-forming composition may also contain other additives besides inorganic fine particles and compounds having polymerizable functional groups.

[0087] In the present invention, "cured product of a compound having polymerizable functional groups" refers to a cured product obtained when a curable component in a composition containing a compound having polymerizable functional groups hardens to form a matrix. If the composition contains solid components such as particles, the cured product is composed of the matrix and the solid components.

[0088] The protective layer according to the present invention exhibits improved charge transport performance when it contains a charge transport compound. Therefore, it is preferable to use a charge transport compound as the polymerizable functional group compound contained in the protective layer. Furthermore, using a charge transport compound having a chain polymerizable functional group as the charge transport compound further improves the resin strength of the protective layer, thereby improving abrasion resistance, which is preferable.

[0089] Furthermore, it is preferable to include polymerizable monomers having three or more functional groups as the compound having polymerizable functional groups.

[0090] (2.2.1) Charge transport compounds having chain polymerizable functional groups A "charge-transporting compound having a chain-polymerizable functional group" refers to a compound that has a charge-transporting compound as its basic skeleton and possesses at least one chain-polymerizable functional group.

[0091] The compound having the polymerizable functional group is preferable because it is a charge-transporting compound having a chain-polymerizable functional group, which improves the charge transport performance of the entire photosensitive layer.

[0092] A "chain polymerization functional group" refers to a functional group that can undergo reactions via chain polymerization. A "charge transport compound" refers to a compound that exhibits charge transport properties.

[0093] The term "charge-transporting compound having a chain-polymerizable functional group" is not limited to a specific compound, and may be a compound consisting of any combination of a charge-transporting compound forming the basic skeleton and a chain-polymerizable functional group. It may also have other substituents or linking groups.

[0094] The "charge transport compound having a chain polymerizable functional group" according to the present invention is not limited to a specific compound as described above, but it is preferable that it has a structure represented by the following general formula (1).

[0095] [ka] In general formula (1), substituent X of the aryl group is an acryloyl group or a methacryloyl group, and may have an alkylene group or a divalent polyether residue between X and the aryl group. n represents an integer from 1 to 3. The hydrogen atoms bonded to the aryl group in general formula (1) may be substituted with an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a halogen atom.

[0096] The substituent X represents an acryloyloxy group or methacryloyloxy group, which are chain polymerizable functional groups, but may have an alkylene group, an oxyalkylene group, or a polyoxyalkylene group between it and the aryl group.

[0097] The alkylene group that substituent X may have is -(CH2) n - is a linking group having the structure represented by -. If substituent X has an alkylene group, -(CH2)n In -, n is preferably an integer between 1 and 6, and more preferably an integer between 1 and 3.

[0098] The oxyalkylene group or polyoxyalkylene group that substituent X may have is -(OCH2CH2) n -(OCH2CH2) is a linking group having the structure represented by -. n - When n is 1, it is called an oxyalkylene group, and when n is 2 or more, it is called a polyoxyalkylene group. When substituent X has an oxyalkylene group or a polyoxyalkylene group, -(OCH2CH2) n In -, n is preferably an integer between 1 and 6, and more preferably an integer between 1 and 3.

[0099] Examples of C1-C10 alkyl groups that can substitute hydrogen atoms in an aryl group include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl, sec-hexyl, tert-hexyl, isoheptyl, sec-heptyl, tert-heptyl, isooctyl, sec-octyl, tert-octyl, isononyl, sec-nonyl, tert-nonyl, isodecyl, sec-decyl, and tert-decyl groups. Among these, lower alkyl groups such as methyl, ethyl, and isopropyl are preferred.

[0100] Examples of C1-C10 alkoxy groups that can substitute hydrogen atoms in an aryl group include: methoxy, ethoxy, n-propoxy, n-butoxy, n-pentyloxy, n-hexyloxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, isopropoxy, isobutoxy, sec-butoxy, tert-butoxy, isopentyloxy, neopentyloxy, and tert-pe. Examples include ethyloxy group, isohexyloxy group, sec-hexyloxy group, tert-hexyloxy group, isoheptyloxy group, sec-heptyloxy group, tert-heptyloxy group, isooctyloxy group, sec-octyloxy group, tert-octyloxy group, isononyloxy group, sec-nonyloxy group, tert-nonyloxy group, isodecyloxy group, sec-decyloxy group, tert-decyloxy group, etc. Among these, a methoxy group or an ethoxy group is preferred.

[0101] Examples of halogen groups in which a hydrogen atom of an aryl group can be substituted include fluoro groups, chloro groups, bromo groups, and iodo groups.

[0102] The proportion of the compound of general formula (1) contained in the protective layer is preferably in the range of 2 to 60 parts by mass, more preferably in the range of 10 to 50 parts by mass, and even more preferably in the range of 10 to 35 parts by mass, based on 100 parts by mass of the resin component of the protective layer.

[0103] Furthermore, the proportion of the compound of general formula (1) in the protective layer relative to the resin component may be considered to be the same as the proportion of the compound of general formula (1) relative to the polymerizable compound in the protective layer coating solution.

[0104] Thus, by incorporating a charge transport material satisfying the general formula (1) into the protective layer according to the present invention, trapping of charge carriers in the protective layer can be prevented, thereby preventing an increase in residual potential and the occurrence of image memory (transfer memory), etc.

[0105] Generally, charge-transporting compounds with relatively large π-conjugated skeletons are used to improve charge transport performance. However, such common charge-transporting compounds strongly absorb light in the wavelength range of 360-400 nm, which is suitably used in photocuring reactions, making it difficult to apply photocuring reactions to form layers containing these compounds.

[0106] In contrast, the structure represented by general formula (1) does not absorb light in the wavelength range of 360-400 nm, and its charge transport performance is at the same level as that of charge transport compounds in typical electrophotographic photoreceptors.

[0107] Therefore, when using a charge-transporting compound having the structure represented by general formula (1), a protective layer with sufficient charge transport performance can be formed by applying a simple method such as a photocuring reaction.

[0108] (Types of chain polymerization) Chain polymerization mainly consists of addition polymerization and ring-opening polymerization.

[0109] "Addition polymerization" is a reaction in which functional groups having unsaturated moieties, such as C=C, C≡C, C=O, C=N, and C≡N, undergo chain polymerization by radicals, ions, etc. It primarily involves the chain polymerization of functional groups containing C=C.

[0110] Specific examples of addition-polymerizable functional groups are shown below. In the structural formulas, * indicates a bonding site. R indicates a hydrogen atom or a substituent such as an alkyl group, aralkyl group, or aryl group.

[0111] [ka]

[0112] "Ring-opening polymerization" is a reaction in which a cyclic structure with high steric strain opens its ring and undergoes chain polymerization. Specific examples of ring-opening polymerizable functional groups are shown below. In the structural formulas, * indicates a bonding site. R indicates a hydrogen atom or a substituent such as an alkyl group, aralkyl group, or aryl group.

[0113] [ka]

[0114] Among the chain polymerizable functional groups mentioned above, addition polymerizable functional groups are preferred, and acryloyloxy groups (CH2=CHCOO-) or methacryloyloxy groups (CH2=C(CH3)COO-) are more preferred.

[0115] 〔structure〕 The following are examples of the structures of the "charge-transporting compounds having chain-polymerizable functional groups" according to the present invention. Of these, T-1 to T-13 correspond to the structures represented by general formula (1).

[0116] [ka]

[0117] [ka]

[0118] [ka]

[0119] [Specific examples] Examples of charge transport compounds that can form the basic framework of a "charge transport compound having a chain polymerizable functional group" include triphenylamine derivatives, carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolon derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl derivatives, hydrazone derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, phenylenediamine derivatives, stilbene derivatives, and benzidine derivatives.

[0120] Among the above compounds, triphenylamine derivatives are preferred, and in the triphenylamine derivatives, it is preferable that one of the phenyl groups is a biphenyl group.

[0121] [Content ratio] The content of the charge transport compound having a chain polymerizable functional group in the protective layer-forming composition is preferably in the range of 10 to 90% by mass, and more preferably in the range of 20 to 80% by mass, based on the total amount of the protective layer-forming composition. A content of 10% by mass or more provides sufficient charge transport, thereby providing sufficient memory resistance. A content of 90% by mass or less provides sufficient crosslinking density of the protective layer, thereby providing sufficient abrasion resistance.

[0122] The presence of a cured product of a charge-transporting compound having a chain-polymerizable functional group in the protective layer can be confirmed by subjecting the alkaline hydrolysate obtained by alkaline hydrolysis of the protective layer to known instrumental analysis methods such as NMR, IR, and mass spectrometry.

[0123] [Synthesis method] Charge-transporting compounds having chain-polymerizable functional groups can be synthesized using known methods. For example, compounds having structure T-3 can be synthesized by the esterification reaction of an N,N-diphenyl-N-biphenylamine derivative having a hydroxyl group with acrylate chloride, as shown in the reaction equation below.

[0124] [ka]

[0125] (2.2.2) Trifunctional or higher polymerizable monomers The protective layer-forming composition according to the present invention may contain, in addition to the charge-transporting compound having a chain-polymerizable functional group, a polymerizable monomer with three or more functions. A "polymerizable monomer" refers to a compound that has polymerizable groups and polymerizes (cures) upon irradiation with active energy rays such as ultraviolet light, visible light, or electron beams, or upon the addition of energy such as heating.

[0126] The polymerizable monomer with three or more functions may be a compound that polymerizes only with other polymerizable monomer molecules to introduce a three-dimensional network structure into the matrix of the protective layer. Alternatively, the polymerizable monomer with three or more functions may be a compound that polymerizes together with a charge-transporting compound to introduce a three-dimensional network structure into the matrix of the protective layer. This increases the crosslinking density of the matrix of the protective layer, resulting in a protective layer with high hardness and high elasticity, and achieving higher abrasion resistance and scratch resistance.

[0127] The polymerizable groups of a trifunctional or higher polymerizable monomer are preferably addition polymerizable functional groups. Among addition polymerizable functional groups, acryloyloxy groups (CH2=CHCOO-) or methacryloyloxy groups (CH2=C(CH3)COO-) are particularly preferred because they allow curing with less light or in a shorter time.

[0128] In polymerizable monomers with three or more functions, it is preferable that the portion other than the polymerizable group does not have charge transport ability. From this viewpoint, the portion other than the polymerizable group in polymerizable monomers with three or more functions is typically preferably an aliphatic hydrocarbon group which may have oxygen atoms between carbon atoms, an isocyanuric ring, etc.

[0129] The content of trifunctional or higher polymerizable monomers is preferably in the range of 20 to 80% by mass, and more preferably in the range of 30 to 70% by mass, relative to the total amount of the protective layer forming composition.

[0130] When the content of trifunctional or higher polymerizable monomers is 20% by mass or more, the resulting protective layer matrix has a sufficient crosslinking density, and the abrasion resistance of the protective layer is significantly improved. When the content of trifunctional or higher polymerizable monomers is 80% by mass or less, the charge transport capacity of the protective layer is sufficient without a decrease in the content of charge transport compounds having chain polymerizable functional groups, resulting in excellent memory resistance.

[0131] Examples of polymerizable monomers with three or more functions include the compounds (compounds M1 to M11) exhibiting the following structures. However, the present invention is not limited to these.

[0132] In the following formulas, R represents an acryloyl group (CH2=CHCO-) ​​and R' represents a methacryloyl group (CH2=C(CH3)CO-).

[0133] [ka]

[0134] The polymerizable monomers with three or more functions may be synthetic or commercially available. Furthermore, the polymerizable monomers with three or more functions may be used individually or in combination of two or more types.

[0135] (2.3) Other ingredients The protective layer-forming composition according to the present invention may contain other optional components as long as they do not impair the effects of the present invention.

[0136] Other components include, for example, polymerization initiators, lubricating organic particles, antioxidants, stabilizers, and silicone oils.

[0137] (Polymerization initiator) Polymerization initiators are used to polymerize polymerizable compounds, such as compounds having polymerizable functional groups which are essential components of protective layer-forming compositions, and polymerizable compounds such as trifunctional or higher polymerizable monomers which are optional components.

[0138] The polymerization initiator is appropriately selected depending on the type of polymerizable compound contained in the protective layer-forming composition. In the present invention, the polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator, but a photopolymerization initiator is preferred. A radical polymerization initiator is particularly preferred.

[0139] The radical polymerization initiator is not particularly limited and any known one can be used, such as alkylphenone compounds and phosphine oxide compounds. Among these, compounds having an α-aminoalkylphenone structure or an acylphosphine oxide structure are preferred, and compounds having an acylphosphine oxide structure are more preferred. An example of a compound having an acylphosphine oxide structure is Omnirad819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by IGM Resins BV). The polymerization initiator may be used alone or in combination of two or more.

[0140] The amount of polymerization initiator in the protective layer-forming composition is preferably in the range of 0.1 to 20 parts by mass, and more preferably in the range of 0.5 to 10 parts by mass, per 100 parts by mass of the total amount of compounds having polymerizable functional groups.

[0141] (Lubricating organic fine particles) The protective layer according to the present invention contains lubricating organic fine particles, which further improves the wear resistance of the protective layer.

[0142] As lubricating organic fine particles, for example, fluorine atom-containing resin particles can be used. It is preferable to appropriately select one or more from among tetrafluoroethylene resin, trifluoroethylene chloride resin, trifluoroethylene chloride propylene resin, hexafluoroethylene chloride propylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluorodichloride resin, and copolymers thereof as fluorine atom-containing resin particles. Tetrafluoroethylene resin and vinylidene fluoride resin are particularly preferred.

[0143] The particle size of the lubricating organic fine particles is preferably in the range of 0.01 to 1 μm for the number mean primary particle size. Particularly preferably, it is in the range of 0.05 to 0.5 μm. The number mean primary particle size of the lubricating organic fine particles is measured in the same manner as for inorganic fine particles.

[0144] The proportion of lubricating organic fine particles in the protective layer-forming composition is preferably in the range of 5 to 70 parts by mass, and more preferably in the range of 10 to 60 parts by mass, based on 100 parts by mass of the total amount of polymerizable compounds.

[0145] (Antioxidants, stabilizers, silicone oil, etc.) For antioxidants, those disclosed in Japanese Patent Publication No. 2000-305291, etc., are preferred. For stabilizers and silicone oils, various known types can be used depending on the application. Antioxidants, stabilizers, silicone oils, etc., can each be used in a range of preferably 0.01 to 50 parts by mass, more preferably 0.01 to 40 parts by mass, per 100 parts by mass of the total amount of polymerizable compounds.

[0146] (2.4) Thickness of the protective layer The thickness of the protective layer is preferably in the range of 0.2 to 10.0 μm, and more preferably in the range of 0.5 to 6.0 μm.

[0147] (2.5) Method for forming a protective layer The protective layer according to the present invention is obtained by preparing a protective layer forming coating solution by mixing the aforementioned inorganic fine particles, a compound having polymerizable functional groups, and other components in a solvent, applying the protective layer forming coating solution onto a charge transport layer, drying and curing it to form a resin layer.

[0148] During the above coating, drying, and curing processes, reactions between the radical polymerizable functional groups of the metal oxide particles, reactions between the radical polymerizable functional groups and polymerizable compounds, and reactions between polymerizable compounds proceed in a mixed manner, forming a protective resin layer.

[0149] As stated above, in this specification, "coating liquid for forming a protective layer" means "composition for forming a protective layer." Furthermore, the resin component in the protective layer may be considered to be formed by the curing reaction of all polymerizable compounds contained in the coating liquid for forming a protective layer.

[0150] As a coating method for forming a protective layer, known coating methods can be used, but coating using a slide hopper type device and coating by immersion coating are preferred. As a slide hopper type device, for example, a circular slide hopper type coating device described in detail in Japanese Patent Publication No. 58-189061 can be used.

[0151] (solvent) Examples of solvents used in preparing coating solutions for forming a protective layer include, but are not limited to, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol, benzyl alcohol, toluene, xylene, methylene chloride, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine.

[0152] Any solvent can be used as long as it can dissolve or disperse inorganic fine particles, compounds having polymerizable functional groups, and other components.

[0153] (Coating solution for forming a protective layer) There are no particular restrictions on the method for preparing the protective layer-forming coating solution. A compound having polymerizable functional groups, inorganic fine particles, and other components can be added to a solvent and stirred until completely dissolved or dispersed. There are also no particular restrictions on the amount of solvent; it can be adjusted as needed to achieve a viscosity suitable for the coating process.

[0154] As a method for applying the protective layer-forming coating solution to the charge transport layer, known methods such as immersion coating, spray coating, spinner coating, bead coating, blade coating, beam coating, slide hopper method, and circular slide hopper method can be used.

[0155] (Curing method) The protective layer is preferably formed by applying the protective layer-forming coating solution to the charge transport layer, then allowing the coating film of the protective layer-forming coating solution to air dry or heat dry, irradiating it with active rays to generate radicals and polymerize, and forming cross-linked bonds through intermolecular and intramolecular cross-linking reactions to cure it. This produces a cured resin.

[0156] Ultraviolet light and electron beams are more preferred as the active beams, with ultraviolet light being particularly preferred due to its ease of use.

[0157] Any light source that emits ultraviolet light can be used without restriction, such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, and flash (pulsed) xenon lamps.

[0158] Irradiation conditions vary depending on the lamp, but the amount of active radiation is typically 5-500 mJ / cm². 2 Within the range of 5 to 100 mJ / cm², preferably 5 to 100 mJ / cm². 2 The lamp power is preferably in the range of 0.1 to 5 kW, and particularly preferably in the range of 0.5 to 3 kW.

[0159] There are no particular restrictions on the electron beam irradiation device used as the electron source; generally, curtain beam type electron accelerators, which are relatively inexpensive and can provide high output, are effectively used for such electron beam irradiation. The acceleration voltage during electron beam irradiation is preferably 100 to 300 kV. The absorbed dose is preferably 0.5 to 10 Mrad.

[0160] The irradiation time required to obtain the necessary amount of active radiation is preferably in the range of 0.1 seconds to 10 minutes, and more preferably in the range of 0.1 seconds to 5 minutes from the viewpoint of work efficiency.

[0161] Drying can be performed before, during, and after irradiation with the active ray, and the timing of drying can be appropriately selected by combining these methods.

[0162] Drying conditions can be appropriately selected depending on the type of solvent, film thickness, etc. The drying temperature is preferably The temperature is within the range of room temperature to 180°C, and is particularly preferably within the range of 80 to 140°C. The drying time is preferably within the range of 1 to 200 minutes, and is particularly preferably within the range of 5 to 100 minutes.

[0163] 2. Conductive support The conductive support according to the present invention may be any support having conductivity. Examples of such supports include those made by forming metals such as aluminum, copper, chromium, nickel, zinc, and stainless steel into a drum or sheet shape.

[0164] Other examples include metal foils made of aluminum or copper laminated onto a plastic film, and plastic films coated with aluminum, indium oxide, or tin oxide. Furthermore, examples include metals, plastic films, and paper coated with a conductive material, either alone or together with a binder resin, to form a conductive layer.

[0165] 3. Middle class The intermediate layer has the function of enhancing the barrier or adhesion between the conductive support and the charge generation layer or the charge transport layer which also functions as a charge generation layer. Although the intermediate layer is not an essential component in the photoreceptor of the present invention, it is preferable to provide an intermediate layer considering various failure prevention measures.

[0166] Such an intermediate layer is, for example, a layer containing a binder resin and, if necessary, conductive particles or metal oxide particles. Hereinafter, the "binder resin used to form the intermediate layer" will also be referred to as the "binder resin for intermediate layer formation."

[0167] Examples of binder resins for forming the intermediate layer include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide resin, polyurethane resin, and gelatin. Among these, alcohol-soluble polyamide resins are preferred.

[0168] The intermediate layer may contain various conductive particles or metal oxide particles for the purpose of adjusting resistance. Examples of metal oxide particles include alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, and zirconium oxide. Alternatively, composite metal oxide particles, such as tin-doped indium oxide or antimony-doped tin oxide, may be used as the metal oxide particles.

[0169] The number-average primary particle size of the metal oxide particles described above is preferably in the range of 10 to 300 nm, and more preferably in the range of 20 to 100 nm.

[0170] Conductive particles or metal oxide particles may be used individually or in combination of two or more types. When two or more types are mixed, they may take the form of a solid solution or fusion.

[0171] The content ratio of conductive particles or metal oxide particles is preferably in the range of 20 to 400 parts by mass, and more preferably in the range of 50 to 350 parts by mass, per 100 parts by mass of binder resin.

[0172] The thickness of the intermediate layer is preferably in the range of 0.1 to 15 μm, and more preferably in the range of 0.3 to 10 μm.

[0173] 4. Charge generation layer The charge generation layer is a layer containing a charge generating agent and a binder resin. Hereinafter, the "binder resin used to form the charge generation layer" will also be referred to as the "binder resin for forming the charge generation layer."

[0174] Examples of charge-generating agents include, but are not limited to, azo pigments such as Sudan Red and Diane Blue, quinone pigments such as pyrenequinone and anthantrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, polycyclic quinone pigments such as pyranthrone and diphthaloylpyrene, and phthalocyanine pigments. Among these, polycyclic quinone pigments and titanylphthalocyanine pigments are preferred. These charge-generating agents may be used individually or in combination of two or more.

[0175] As the binder resin for forming the charge generation layer, known resins can be used, for example, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenolic resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and copolymer resins containing two or more of these resins, polyvinylcarbazole resin, etc., but are not limited to these. Examples of the above-mentioned "copolymer resins" include vinyl chloride-vinyl acetate copolymer resin and vinyl chloride-vinyl acetate-maleic anhydride copolymer resin.

[0176] Among the binder resins for forming the charge generation layer listed above, polyvinyl butyral resin is particularly preferred.

[0177] The content ratio of the charge generating agent in the charge generating layer is preferably in the range of 1 to 600 parts by mass, and more preferably in the range of 50 to 500 parts by mass, per 100 parts by mass of the binder resin for forming the charge generating layer.

[0178] The thickness of the charge generation layer varies depending on the properties of the charge generation agent, the properties and content ratio of the binder resin for forming the charge generation layer, etc., but is preferably in the range of 0.01 to 5 μm, and more preferably in the range of 0.05 to 3 μm.

[0179] 5.Charge transport layer The charge transport layer according to the present invention is a layer containing a charge transport compound and a binder resin. Hereinafter, the "binder resin used for forming the charge transport layer" will also be referred to as the "binder resin for forming the charge transport layer."

[0180] Furthermore, the charge transport compound contained in the charge transport layer is a non-reactive charge transport compound. A "non-reactive charge transport compound" is a charge transport compound that does not have a chain polymerizable functional group.

[0181] In the present invention, the charge transport layer may also be a layer containing a charge generating material and thus serving as a charge generating layer. When the charge transport layer also serves as a charge generating layer, it is not necessary to have a separate charge generating layer between the conductive support and the charge transport layer.

[0182] If the charge transport layer also functions as a charge generation layer, the charge transport layer contains a charge generating agent as described below.

[0183] The binder resin for forming the charge transport layer can be a known resin, such as polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylate ester resin, or styrene-methacrylate ester copolymer resin, but polycarbonate resin is preferred.

[0184] Furthermore, polycarbonate resins of the BPA (bisphenol A) type, BPZ (bisphenol Z) type, dimethyl BPA type, and BPA-dimethyl BPA copolymer type are preferred in terms of crack resistance, abrasion resistance, and electrostatic properties.

[0185] The content of the nonreactive charge transport compound in the charge transport layer is preferably in the range of 10 to 500 parts by mass, and more preferably in the range of 20 to 250 parts by mass, per 100 parts by mass of the binder resin for forming the charge transport layer.

[0186] The charge transport layer may contain antioxidants, electronically conductive agents, stabilizers, silicone oil, etc. For antioxidants, those disclosed in Japanese Patent Publication No. 2000-305291 are preferred, and for electronically conductive agents, those disclosed in Japanese Patent Publication Nos. 50-137543 and 58-76483 are preferred.

[0187] The thickness of the charge transport layer varies depending on the properties of the non-reactive charge transport compound, the properties and content ratio of the binder resin used to form the charge transport layer, etc., but is preferably in the range of 5 to 40 μm, and more preferably in the range of 10 to 30 μm.

[0188] [II. Electrophotographic image forming method and electrophotographic image forming apparatus] The electrophotographic photoreceptor of the present invention exhibits even greater effects when combined with the electrophotographic image forming apparatus of the present invention.

[0189] The following describes an example of an image forming method using an electrophotographic image forming apparatus equipped with the electrophotographic photoreceptor of the present invention, but the details of the electrophotographic photoreceptor are as described above. Hereinafter, "electrophotographic image forming apparatus" will also be simply referred to as "image forming apparatus".

[0190] Figure 3 is an explanatory cross-sectional view showing an example of the configuration of an image forming apparatus according to the present invention. In Figure 3, the image forming apparatus comprises a charging means, an exposure means, a developing means, and a transfer means.

[0191] The image forming apparatus 100 shown in Figure 3 is called a tandem-type color image forming apparatus and has four sets of image forming units 110Y, 110M, 110C, and 110Bk, a paper feeding and transporting means 150, and a fixing means 170.

[0192] A document image reading device SC is located on the upper part of the main body of the image forming apparatus 100.

[0193] The image forming units 110Y, 110M, 110C, and 110Bk are arranged in a vertical line.

[0194] The image forming units 110Y, 110M, 110C, and 110Bk each include a rotating drum-shaped photoreceptor 111Y, 111M, 111C, and 111Bk, and charging means 113Y, 113M, 113C, and 113Bk, exposure means 115Y, 115M, 115C, and 115Bk, developing means 117Y, 117M, 117C, and 117Bk, primary transfer rollers (primary transfer means) 133Y, 133M, 133C, and 133Bk, and cleaning means 119Y, 119M, 119C, and 119Bk.

[0195] The device is configured such that yellow (Y), magenta (M), cyan (C), and black (Bk) toner images are formed on the photoreceptors 111Y, 111M, 111C, and 111Bk, respectively.

[0196] The following describes each component of the image forming apparatus other than the photoreceptor. When explaining using diagrams, the example of the image forming unit 110Y will be used.

[0197] (Means of charging) The charging means is a means of uniformly charging the surface of the photoreceptor.

[0198] The charging method may be either contact-based or non-contact-based. Examples of contact-based methods include charging rollers, charging brushes, and charging blades. Examples of non-contact-based methods include corona chargers. Examples of corona chargers include corotron chargers and strocoton chargers.

[0199] The contact method has the advantage of generating less harmful ozone gas during the charging process. The non-contact method has the advantage of being less prone to filming compared to the contact method because it does not involve proximity discharge.

[0200] It is preferable that the charging means be a proximity charging roller and a contact charging roller, as this reduces the amount of harmful ozone gas generated during the charging process, which is advantageous for improving image quality and miniaturizing the device.

[0201] The charging means 113Y shown in Figure 3 is a contact type. In this example, the charging means 113Y consists of a charging roller positioned in contact with the surface of the photoreceptor 111Y and a power supply that applies voltage to the charging roller.

[0202] (Exposure means) The exposure means is a means of exposing a photoreceptor, which has been given a uniform potential by a charging means, based on an image signal, to form an electrostatic latent image corresponding to the image.

[0203] Examples of exposure methods include those consisting of an LED array with light-emitting elements arranged in the axial direction of the photoreceptor and an imaging element, and those using a laser optical system.

[0204] (Developing means) A developing means (developing machine) is a means of supplying a developer to the surface of a photoreceptor to develop the electrostatic latent image formed on the surface of the photoreceptor and to form a toner image.

[0205] The developer used was the same as that described above for the electrostatic image developing toner.

[0206] The developing means 117Y shown in Figure 3 specifically consists of a developing roller 118Y that incorporates a magnet and rotates while holding the developer, and a voltage application device (not shown) that applies a DC and / or AC bias voltage between the photoreceptor 111Y and the developing roller 118Y.

[0207] The developing roller 118Y rotates to transport the developer to the photoreceptor 111Y. Then, the thin layer of toner on the developing roller 118Y comes into contact with the photoreceptor 111Y, developing the electrostatic latent image on the photoreceptor 111Y.

[0208] The developing roller 118Y is connected to a voltage application device. This device applies a DC and / or AC bias voltage to the developing roller 118Y. The system is configured so that the developing bias can be adjusted to a desired value by controlling the voltage applied to the developing roller 118Y.

[0209] An electric field is formed in the developing section where the developing roller 118Y and the photoreceptor 111Y face each other, due to the potential difference (developing potential difference) between the potential of the electrostatic latent image supported by the developing roller 118Y and the photoreceptor 111Y.

[0210] The toner in the developer, transported to the developing section by the rotation of the developing roller 118Y, moves due to the force from the electric field and adheres to the electrostatic latent image on the photoreceptor 111Y. As the electrostatic latent image carried on the photoreceptor 111Y is made visible, a toner image corresponding to the shape of the electrostatic latent image is formed on the surface of the photoreceptor 111Y.

[0211] <Lubricant supply means> The developing means is equipped with a lubricant supply means for supplying a lubricant to the developer. This improves wear resistance. From the viewpoint of improving wear resistance, it is more preferable that the lubricant is a metal soap.

[0212] (Transfer means) A transfer means is a means of transferring the toner image on a photoreceptor to a transfer body. This transfer body is either an intermediate transfer body or a transfer material. When an intermediate transfer body is used, the primary transfer roller becomes the transfer means.

[0213] Since the transfer means is a means for transferring the toner image on the photoreceptor, the secondary transfer roller used when transferring from the intermediate transfer body to the transfer material is not included in the transfer means.

[0214] The primary transfer roller 133Y shown in Figure 3 transfers the toner image formed on the photoreceptor 111Y to the endless belt-shaped intermediate transfer body 131. The primary transfer roller 133Y is positioned in contact with the intermediate transfer body 131.

[0215] In the image forming apparatus 100 shown in Figure 3, the photoreceptors 111Y, 111M, 111C, 1 An intermediate transfer method is employed in which the toner image formed on 11Bk is transferred to an intermediate transfer body 131 by primary transfer rollers (primary transfer means) 133Y, 133M, 133C, and 133Bk, and each toner image transferred on the intermediate transfer body 131 is transferred to a transfer material P by a secondary transfer roller (secondary transfer means) 217. However, a direct transfer method may also be employed in which the toner image formed on the photoreceptor is directly transferred to the transfer material P by the transfer means. [Examples]

[0216] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the examples, the units "parts" or "%" are used, and unless otherwise specified, they represent "parts by mass" or "mass%".

[0217] The chemical structural formulas of the charge transport compounds (CT-1) to (CT-4) and (CTM-1) used in the fabrication of the photoreceptor are shown below. Note that charge transport compounds (CT-1), (CT-2), and (CT-3) have chain polymerizable functional groups, while charge transport compounds (CT-4) and (CTM-1) do not.

[0218] [ka]

[0219] A. Fabrication of the photoreceptor (A.1) Photoreceptor 1 (Preparation of conductive support) A conductive support [1] with a surface roughness Rz = 1.5 μm was prepared by machining the surface of a cylindrical aluminum support with a diameter of 30 mm.

[0220] (Formation of the intermediate layer) The following materials were mixed in the specified quantities, and the mixture was dispersed in a batch using a sand mill for 10 hours. After standing overnight, the mixture was filtered. A 5μm rigidmesh filter (manufactured by Nippon Pall Co., Ltd.) was used for filtration.

[0221] ·material Polyamide resin "CM8000" (manufactured by Toray Industries, Inc.) 1 part by mass Titanium oxide "SMT500SAS" (manufactured by Teika Co., Ltd.) 3 parts by mass 20 parts by mass of methanol

[0222] Based on the above, the coating solution for forming the intermediate layer [1] was prepared.

[0223] An intermediate layer [1] was formed by applying an intermediate layer [1] to a conductive support [1] using an immersion coating method to achieve a dry film thickness of 2 μm.

[0224] (Formation of a charge generation layer) The following materials were mixed in the specified quantities and dispersed using a sand mill for 10 hours. The "titanium phthalocyanine pigment" in the materials listed below has a maximum diffraction peak at at least 27.3° as measured by Cu-Kα characteristic X-ray diffraction spectroscopy.

[0225] ·material Titanyl phthalocyanine pigment (charge generating substance) 20 parts by mass Polyvinyl butyral resin "#6000-C" (manufactured by Denki Kagaku Kogyo Co., Ltd.) 10 parts by mass 700 parts by mass of t-butyl acetate 4-Methoxy-4-methyl-2-pentanone (mixed solvent) 300 parts by mass

[0226] Based on the above, a coating solution for forming a charge generation layer [1] was prepared.

[0227] This charge generation layer forming coating solution [1] was applied to the intermediate layer [1] by immersion coating to a dry film thickness of 0.3 μm, and the charge generation layer [1] was formed by drying at 25°C for 30 minutes.

[0228] (Formation of a charge transport layer) "Z-300" polycarbonate, a copolymer of bisphenol Z manufactured by Mitsubishi Gas Chemical Company (solubility parameter δ B =9.9) Using 100 parts by mass as a binder resin, the following materials were mixed in the following quantities and dissolved.

[0229] ·material Charge transporting compound (CTM-1) 50 parts by mass Antioxidant "Irganox 1010" (manufactured by BASF Japan) 2 parts by mass 540 parts by mass of tetrahydrofuran Toluene 135 parts by mass Silicone oil "KF-54" (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.3 parts by mass

[0230] Based on the above, a coating solution for forming a charge transport layer [1] was prepared.

[0231] A charge transport layer forming solution [1] was applied to the charge generation layer [1] by immersion coating to a dry film thickness of 18 μm, thereby forming the charge transport layer [1].

[0232] (Formation of a protective layer) Inorganic fine particles [1] of the following material were mixed and stirred in a mixed solvent of 2-butanol (solvent 1) and 4-methyltetrahydropyran (solvent 2), and then thoroughly dispersed by ultrasound. The inorganic fine particles [1] are fine particles of silica particles "SO-C1" (average primary particle size 300 nm) manufactured by Admatex, Inc., surface-treated with a methacrylsilane compound. The amounts of the inorganic fine particles [1], 2-butanol (solvent 1), and 4-methyltetrahydropyran (solvent 2) are as follows. The methacrylsilane compound used was 3-methacryloxypropyltrimethoxysilane "KBM-503" manufactured by Shin-Etsu Chemical Co., Ltd.

[0233] · Materials Inorganic fine particles [1] 13.2 parts by mass 2-Butanol (solvent 1) 40 parts by mass 4-Methyltetrahydropyran (solvent 2) 19 parts by mass

[0234] Thereby, an inorganic fine particle dispersion liquid [1] was prepared.

[0235] For the inorganic fine particle dispersion liquid [1], the following materials were sequentially added in the following amounts, mixed and stirred, and dissolved sufficiently.

[0236] · Materials Charge transporting compound (CT-1) 14.9 parts by mass Polymerizable monomer "SR350" 11.2 parts by mass "Omnirad819" 0.4 parts by mass

[0237] Note that the polymerizable monomer in the above materials is manufactured by Sartomer Company and is trimethylolpropane trimethacrylate represented by the following chemical structural formula M1. Also, the photoinitiator "Omnirad819" is a photoinitiator manufactured by IGM Resins B.V.

[0238]

Chemical formula

[0239] As described above, a coating liquid [1] for forming a protective layer was prepared.

[0240] The prepared coating liquid [1] for forming a protective layer was applied onto the charge transport layer [1] using a circular slide hopper coater. Next, after irradiating with ultraviolet rays for 1 minute using an LED light source with a wavelength of 385 nm, drying was performed at 110°C for 70 minutes.

[0241] Thereby, a protective layer with a thickness of 3.5 μm after drying was formed, and the photoreceptor 1 was manufactured.

[0242] (A.2) Photoconductor 2 In the preparation of the inorganic microparticle dispersion [1] for forming the protective layer, the photoreceptor 2 was prepared in the same manner as photoreceptor 1, except that inorganic microparticles [1] were replaced with inorganic microparticles [2].

[0243] The inorganic microparticles [2] were "YC100C" (average primary particle size 100 nm) manufactured by Admatex Corporation.

[0244] (A.3) Photoreceptor 3 In the preparation of the inorganic fine particle dispersion [1] for the formation of a protective layer, the inorganic fine particles [1] are Photoreceptor 3 was manufactured in the same manner as photoreceptor 1, except that inorganic fine particles [3] were used instead.

[0245] The inorganic microparticles [3] were "SO-C2" (average primary particle size 500 nm) manufactured by Admatex Corporation.

[0246] (A.4) Photoreceptor 4 In the preparation of the inorganic microparticle dispersion [1] for forming the protective layer, the photoreceptor 4 was prepared in the same manner as the photoreceptor 1, except that the inorganic microparticles [1] were replaced with inorganic microparticles [4].

[0247] The inorganic fine particles [4] were a mixture of 8.8 parts by mass of "SO-C1" (average primary particle size 300 nm) manufactured by Admatex Corporation and 4.4 parts by mass of "OX50" (average primary particle size 40 nm) manufactured by Aerosil Corporation.

[0248] (A.5) Photoreceptor 5 In the preparation of the inorganic microparticle dispersion [1] for forming the protective layer, the photoreceptor 5 was prepared in the same manner as the photoreceptor 1, except that the inorganic microparticles [1] were replaced with inorganic microparticles [5].

[0249] The inorganic fine particles [5] were prepared by changing the surface treatment of silica particles "SO-C1" (average primary particle size: 300 nm) manufactured by Admatechs Co., Ltd. The surface treatment was performed by using a mixture of a methacryl silane-based compound and a reactive silicone oil at a weight ratio of 1:1 as the surface treatment agent. As the methacryl silane-based compound, 3-methacryloxypropyltrimethoxysilane "KBM-503" manufactured by Shin-Etsu Chemical Co., Ltd. was used. As the reactive silicone oil, methylhydrogenpolysiloxane "KF-9908" manufactured by Shin-Etsu Chemical Co., Ltd. was used.

[0250] (A.6) Photoconductor 6 In the preparation of the inorganic fine particle dispersion liquid [1] in the formation of the protective layer, a photoconductor 6 was produced in the same manner as the photoconductor 1, except that the inorganic fine particles [1] were changed to inorganic fine particles [6].

[0251] The inorganic fine particles [6] were hexamethyldisilazane surface-treated product "RX50" (average primary particle size: 40 nm) manufactured by Aerosil Co., Ltd.

[0252] (A.7) Photoconductor 7 In the preparation of the inorganic fine particle dispersion liquid [1] in the formation of the protective layer, a photoconductor 7 was produced in the same manner as the photoconductor 1, except that the inorganic fine particles [1] were changed to inorganic fine particles [7].

[0253] The inorganic fine particles [7] were silica particles "SO-C4" (average primary particle size: 1000 nm) manufactured by Admatechs Co., Ltd.

[0254] (A.8) Photoconductor 8 In the preparation of the inorganic fine particle dispersion liquid [1] in the formation of the protective layer, a photoconductor 8 was produced in the same manner as the photoconductor 1, except that the amount of the inorganic fine particles [1] was changed to 4.4 parts by mass.

[0255] (A.9) Photoconductor 9 In the preparation of the inorganic fine particle dispersion [1] for forming the protective layer, the inorganic fine particles [1] were replaced with inorganic fine particles [9], and the amount of said inorganic fine particles [9] was changed to 17.9 parts by mass. Otherwise, the photoreceptor 9 was prepared in the same manner as the photoreceptor 1.

[0256] The inorganic microparticles [9] were alumina particles "AO-502" (average primary particle size 250 nm) manufactured by Admatex, Inc., which were surface-treated with a methacrylate silane compound.

[0257] (A.10) Photoreceptor 10 In the preparation of the inorganic fine particle dispersion [1] for the formation of the protective layer, inorganic fine particles [1] were replaced with inorganic fine particles

[10] , and the amount of inorganic fine particles

[10] was changed to 39.6 parts by mass. In addition, in the formation of the protective layer, the charge transport compound (CT-1) in the material sequentially added to the inorganic fine particle dispersion was replaced with the charge transport compound (CT-2). Otherwise, the photoreceptor 10 was prepared in the same manner as the photoreceptor 1.

[0258] The inorganic microparticles

[10] were "ST-7MK" (average primary particle size 20 nm) manufactured by CIK Nanotech, Inc., and surface-treated with a methacrylate silane compound.

[0259] (A.11) Photoreceptor 11 In forming the protective layer, the charge transport compound (CT-1) in the material sequentially added to the inorganic fine particle dispersion was changed to a charge transport compound (CT-3), which is an arylamine compound obtained by the method described in Japanese Patent Application Publication No. 2023-66792. Otherwise, the photoreceptor 11 was prepared in the same manner as the photoreceptor 1.

[0260] (A.12) Photoreceptor 12 In forming the protective layer, the charge transport compound (CT-1) in the material sequentially added to the inorganic fine particle dispersion was changed to the charge transport compound (CT-4). Furthermore, the polymerizable monomer "SR350" in the above material was changed to the block-type isocyanate "Sumijule BL3175" manufactured by Sumitomo Bayer Urethanes. The photopolymerization initiator "Omnirad819" was not added.

[0261] Otherwise, the protective layer forming coating solution

[12] was prepared in the same manner as the protective layer forming coating solution [1] used in the fabrication of photoreceptor 1. The protective layer forming coating solution

[12] was applied to the charge transport layer while adjusting the coating speed so that the thickness of the protective layer was 6 μm, and then a heat curing treatment was performed. Otherwise, photoreceptor 12 was fabricated in the same manner as photoreceptor 1. Note that the protective layer forming coating solution was not irradiated with ultraviolet light from an LED light source. The above heat curing treatment was performed at 160°C for 60 minutes.

[0262] (A.13) Photoreceptor 13 In the preparation of the inorganic fine particle dispersion [1] for forming the protective layer, the photoreceptor 13 was prepared in the same manner as photoreceptor 1, except that 4-methyltetrahydropyran (solvent 2) was replaced with tetrahydrofuran.

[0263] (A.14) Photoreceptor 14 In the preparation of the inorganic fine particle dispersion [1] for forming the protective layer, the photoreceptor 14 was prepared in the same manner as the photoreceptor 1, except that the inorganic fine particles [1] were replaced with inorganic fine particles

[14] .

[0264] The inorganic fine particles

[14] were melamine particles "Eposter S6" (average primary particle size 400 nm) manufactured by Nippon Shokubai Co., Ltd.

[0265] (A.15) Photoreceptor 15 In forming the protective layer, the charge transport compound (CT-1) in the materials sequentially added to the inorganic fine particle dispersion was changed to the charge transport compound (CTM-1). Furthermore, the polymerizable monomer "SR350" in the above materials was changed to "Z-300," a polycarbonate manufactured by Mitsubishi Gas Chemical Company. The photopolymerization initiator "Omnirad819" was not added. Note that the charge transport compound (CTM-1) is the same compound used in the materials for preparing the coating solution for forming the charge transport layer.

[0266] Otherwise, the protective layer forming coating solution

[15] was prepared in the same manner as the protective layer forming coating solution [1] used in the fabrication of photoreceptor 1. The protective layer forming coating solution

[15] was applied to the charge transport layer while adjusting the coating speed so that the thickness of the protective layer was 6 μm, and then a heat curing treatment was performed. Otherwise, photoreceptor 15 was fabricated in the same manner as photoreceptor 1. Note that the protective layer forming coating solution was not irradiated with ultraviolet light from an LED light source. The heat curing treatment described above was performed at 110°C for 70 minutes.

[0267] (A.16) Summary of the composition of the protective layer Table I summarizes the composition of the protective layer in the fabricated photoreceptor.

[0268] [Table 1]

[0269] B. Calculation of the proportion of inorganic fine particles in the cross-section of the protective layer For each photoreceptor fabricated, the area percentage of inorganic microparticles in the cross-section obtained by cutting the protective layer in the thickness direction was calculated. The protective layer was divided into a first region and a second region from the outermost surface, and the area percentage F1[%] of inorganic microparticles in the cross-section of the first region and the area percentage F2[%] of inorganic microparticles in the cross-section of the second region were calculated. Specifically, the calculations were performed using the following method.

[0270] The cross-section of the photoreceptor protective layer processed using the cross-section polishing (CP) method was observed at a magnification of 10,000x using a scanning electron microscope (SEM). An SM-09010 (JEOL product) was used as the CP processing device, and an S-4800 (HITACHI product) was used as the SEM observation device.

[0271] The SEM image data was binarized, and the bright areas were treated as inorganic microparticles. The area ratio occupied by inorganic microparticles in the first and second regions was then calculated.

[0272] Cross-sectional sampling of the photoreceptor protective layer was performed at three equally spaced points circumferentially from the center position along the long axis of the photoreceptor, and the average values ​​were adopted as F1 and F2. The values ​​of F1 and F2 are shown in Table II.

[0273] C. Rating (C.1) Abrasion resistance evaluation The surface layer thickness was measured before and after the durability test, and the amount of film thickness loss was calculated and evaluated. The surface layer thickness was measured at 10 random locations using a film thickness gauge in the uniform thickness area (excluding the areas with thickness variations at the leading and trailing ends of the coating), and the average value was taken as the surface layer thickness. The film thickness gauge used was the eddy current type film thickness gauge "EDDY560C" (manufactured by HELMUT FISCHER GMBTE CO), and the difference in surface layer thickness before and after the durability test was taken as the amount of film thickness loss. The amount of loss per 100 krot (100,000 revolutions) (μm) is recorded.

[0274] (C.2) Filming evaluation For photoreceptors 1-7, 9-11, and 13-15, filming evaluations were performed by mounting them on the commercially available full-color MFP "bizhub C650i" (manufactured by Konica Minolta).

[0275] For the photoconductor 8, filming evaluation was performed by mounting it in a commercially available full-color MFP camera, the "SP-C831" (manufactured by Ricoh).

[0276] For the photoconductor 12, filming evaluation was performed by mounting it on a commercially available full-color MFP camera, the "iR-ADV C5870" (manufactured by Canon).

[0277] Of the electrophotographic image forming apparatuses mentioned above, the MFP machine "bizhub C650i" has a lubricant supply mechanism that adds a lubricant to the toner and supplies it onto the photoreceptor. The MFP machines "SP-C831" and "iR-ADV C5870" do not have a similar lubricant supply mechanism.

[0278] A durability test was conducted by continuously printing 300,000 double-sided pages of A4 landscape orientation with a text image at a 5% image ratio under conditions of 23°C and 50% RH. This durability test will also be referred to as the long-term printing test.

[0279] At the 10,000-print and 300,000-print stages, the deposits on the surface of each photoreceptor were observed visually and with a 100x optical microscope, and then ranked.

[0280] Furthermore, since the photoconductors 14 and 15 stopped outputting images at the stages of 120,000 and 80,000 prints, respectively, the evaluation was discontinued at this point.

[0281] The evaluation criteria are as follows. Based on the evaluation criteria below, items A and B were judged to be practically acceptable and therefore passed. Items C were judged to have practical problems and therefore failed. The evaluation results are shown in Table II.

[0282] A: No deposits were observed under an optical microscope (100x magnification) (Pass). B: The longest side length of the attached material was 10-200 μm, and it was observed with an optical microscope (100x magnification), but not with the naked eye (pass). C: The longest side length of the attached material was 200 μm or more, and the attached material was observed visually (failure).

[0283] [Table 2]

[0284] D. Summary As is clear from the results in Tables I and II, the examples are at a level that can be used without practical problems, and it can be seen that they are able to achieve both wear resistance and cleaning performance in long-term use.

[0285] Although embodiments of the present invention have been described and illustrated in detail above, the disclosed embodiments are illustrative and for illustrative purposes only and are not limiting. The scope of the present invention should be interpreted by the terms of the appended claims. [Explanation of symbols]

[0286] 100 Image forming apparatus 110Y, 110M, 110C, 110Bk Image Forming Units 111, 111Y, 111M, 111C, 111Bk Photoconductor 101 Conductive support 102 Middle Class 103 Charge generation layer 104 Charge transport layer 105 Protective layer 106 Photosensitive layer (102~105) 113Y, 113M, 113C, 113Bk Charging means (charging roller) 115Y, 115M, 115C, 115Bk exposure means 117Y, 117M, 117C, 117Bk developing means 118Y, 118M, 118C, 118Bk developing rollers 119Y, 119M, 119C, 119Bk Cleaning Methods 131 Intermediate Transfer 133Y, 133M, 133C, 133Bk Transfer method (primary transfer roller) 150 Paper feeding and transporting means 170 Fixing means 217 Secondary transfer roller (secondary transfer means) SC Document Image Reader P Transfer Material h Depth from the outermost surface of the protective layer

Claims

1. An electrophotographic photoreceptor comprising at least a charge generation layer, a charge transport layer, and a protective layer sequentially laminated on a conductive support, The protective layer is a cured film formed from a cured product of a compound containing inorganic fine particles and having polymerizable functional groups. The protective layer has a first region and a second region in that order from the outermost surface side. When the thickness of the protective layer is L, the thickness of the first region is 0.2L, and the thickness of the second region is 0.8L. The area ratio F1 [%] of inorganic fine particles in the cross-section of the first region when the protective layer is cut in the thickness direction, and the area ratio F2 [%] of inorganic fine particles in the cross-section of the second region, satisfy the relationship given by the following formula (1). F1<F2 Formula (1) An electrophotographic photoreceptor characterized by the following features.

2. The primary average particle size of the inorganic fine particles is in the range of 100 to 700 nm. The electrophotographic photoreceptor according to feature 1.

3. The area ratio F1 [%] is 20% or more. The electrophotographic photoreceptor according to feature 1.

4. The area ratio F1 [%] and the area ratio F2 [%] satisfy the relationship shown in the following formula (2). The electrophotographic photoreceptor according to feature 1. F1<0.9×F2 Formula (2)

5. The inorganic fine particles are silica fine particles. The electrophotographic photoreceptor according to feature 1.

6. The compound having the polymerizable functional group is a charge transport compound having a chain polymerizable functional group. The electrophotographic photoreceptor according to feature 1.

7. The charge transport compound has a structure represented by the following general formula (1). The electrophotographic photoreceptor according to feature 6. 【Chemistry 1】 In general formula (1), substituent X of the aryl group is an acryloyl group or a methacryloyl group, and may have an alkylene group or a divalent polyether residue between X and the aryl group. n represents an integer from 1 to 3. The hydrogen atom bonded to the aryl group in general formula (1) may be substituted with an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or a halogen atom.

8. An electrophotographic image forming apparatus equipped with a lubricant supply means, The device comprises an electrophotographic photoreceptor as described in any one of claims 1 to 7, The lubricant supply means is a means for adding a lubricant to the toner for electrostatic image development and supplying it onto the electrophotographic photoreceptor. An electrophotographic image forming apparatus characterized by the following:

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