Electrophotographic photoreceptor and image forming apparatus equipped with the same

Abstract

To provide an electrophotographic photoreceptor that keeps on cleaning properties and wear resistance over a long period through a product life, and further can suppress a reversal of cleaning blades, and to provide an image formation device including the electrophotographic photoreceptor.SOLUTION: An electrophotographic photoreceptor includes at least a photosensitive layer on a conductive substrate. An outermost surface layer of the photosensitive layer contains 5 to 20 mass% of fluorine-based resin particle having an average primary particle diameter of 0.1 to 3.0 μm in the outermost surface layer. A width 4 mm area in a center part of a charge area in an axial direction of the electrophotographic photoreceptor in a surface of the outermost surface layer has ten-point surface roughness Rz of 0.05 to 0.25 μm and an average interval Sm of convexoconcave of 50 to 150 μm, which are defined in JIS-B-0601 (1994). A problem is solved by the electrophotographic photoreceptor characterized in that the surface of the outermost surface layer has a contact angle with respect to pure water equal to or more than 100°.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electrophotographic photoreceptor and an image forming apparatus equipped with the same. More specifically, the present disclosure relates to an electrophotographic photoreceptor that maintains cleaning performance and abrasion resistance over a long period throughout its product life and can suppress reversal of a cleaning blade, and an image forming apparatus equipped with the same. [Background technology]

[0002] In recent years, electrophotographic image forming apparatuses (electrophotographic apparatuses) that form images using electrophotographic technology have been widely used in copiers, printers, facsimile machines, multifunction machines, etc., and the electrophotographic photoreceptors (hereinafter also referred to as "photoreceptors") used in these apparatuses are photoreceptors (also referred to as "organic photoreceptors") that have a photosensitive layer containing an organic photoconductive material as a main component on a conductive substrate. As organic photoreceptors, a structure has been proposed in which a single-layer photosensitive layer is provided on a conductive substrate, in which a charge generating material and a charge transport material are dispersed in a binder resin, and a structure in which a multilayer photosensitive layer is provided in which a charge generating layer in which a charge generating material is dispersed in a binder resin and a charge transport layer in which a charge transport material is dispersed in a binder resin are laminated in that order. Of these, the latter function-separated type photoreceptor is widely used because it has excellent electrophotographic properties and durability, a high degree of freedom in material selection, and the ability to design various photoreceptor properties.

[0003] A drawback of organic photoreceptors is that, due to the nature of the organic materials, the surface is subject to wear due to mechanical loads from cleaners around the photoreceptor, etc. In recent years, studies have been conducted to overcome this drawback by hardening the surface or laminating a protective layer containing a filler, thereby improving the mechanical properties of the surface and increasing the wear resistance of the photoreceptor. However, when the wear resistance of the photoreceptor is improved, problems such as cleaning blade reversal tend to occur during the cleaning process.

[0004] To solve this problem, Japanese Patent Application Laid-Open No. 2-150850 (Patent Document 1) attempts to roughen the surface of a photosensitive member by blasting, and Japanese Patent Application Laid-Open No. 2010-134459 (Patent Document 2) attempts to form linear scratches on a surface layer containing a filler. However, in the above-mentioned prior art, since the processing is performed only on the surface, there is a problem that it is difficult to achieve the effect throughout the life of the product. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 02-150850 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-134459 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the present disclosure aims to provide an electrophotographic photosensitive member and an image forming apparatus equipped therewith that can maintain cleaning performance and wear resistance over a long period of time throughout the product life and can suppress reversal of the cleaning blade. [Means for solving the problem]

[0007] As a result of intensive research into solving the above-mentioned problems, the inventors discovered that by providing the outermost surface layer of a photosensitive member with specific surface properties, it is possible to suppress the reversal of the cleaning blade, thereby solving the above-mentioned problems, and thus completed the present invention.

[0008] Thus, according to the present disclosure, there is provided an electrophotographic photoreceptor comprising at least a photosensitive layer on a conductive substrate, the outermost layer of the photosensitive layer contains fluorine-based resin fine particles having an average primary particle diameter of 0.1 to 3.0 μm in a proportion of 5 to 20 mass % in the outermost layer, a 4 mm-wide region at the center of the charged region in the axial direction of the electrophotographic photosensitive member on the surface of the outermost layer has a ten-point surface roughness Rz of 0.05 to 0.25 μm and an average spacing Sm of irregularities of 50 to 150 μm, as defined in JIS-B-0601 (1994), The surface of the outermost layer has a contact angle with pure water of 100° or more. An electrophotographic photoreceptor characterized by the above-mentioned is provided.

[0009] Furthermore, according to the present disclosure, there is provided an image forming apparatus comprising at least the above-mentioned electrophotographic photosensitive member, charging means for charging the electrophotographic photosensitive member, exposure means for exposing the charged electrophotographic photosensitive member to light to form an electrostatic latent image, developing means for developing the electrostatic latent image to form a toner image, and transfer means for transferring the toner image onto a recording medium. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide an electrophotographic photoreceptor and an image forming apparatus equipped therewith that can maintain cleaning performance and wear resistance over a long period of time throughout the product life and can suppress reversal of the cleaning blade. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic cross-sectional view showing the configuration of a main part of a photoreceptor according to an embodiment of the present disclosure. [Figure 2] 1 is a schematic side view illustrating a configuration of a main part of an image forming apparatus according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] The photoreceptor of the present disclosure is an electrophotographic photoreceptor including at least a photosensitive layer on a conductive substrate, the outermost layer of the photosensitive layer contains fluorine-based resin fine particles having an average primary particle diameter of 0.1 to 3.0 μm in a proportion of 5 to 20 mass % in the outermost layer, a 4 mm-wide region at the center of the charged region in the axial direction of the electrophotographic photosensitive member on the surface of the outermost layer has a ten-point surface roughness Rz of 0.05 to 0.25 μm and an average spacing Sm of irregularities of 50 to 150 μm, as defined in JIS-B-0601 (1994), The surface of the outermost layer has a contact angle with pure water of 100° or more. It is characterized by: Below, the constituent elements that characterize the photoreceptor of the present disclosure and the surface properties of the outermost layer of the photoreceptor will be described, followed by a description of (1) the photoreceptor and (2) the image forming apparatus. It should be noted that the embodiments and examples described below are merely specific examples of the present invention, and the present invention is not limited to these.

[0013] <Fluorine-based resin particles> The outermost layer of the photosensitive layer contains fluorine-based resin fine particles having an average primary particle diameter of 0.1 to 3.0 μm in a proportion of 5 to 20% by mass in the outermost layer. The fluorine-based resin particles have excellent properties as a lubricant, and can impart lubricity to the surface of the photoreceptor.

[0014] (material) Examples of fluorine-based resin particles include tetrafluoroethylene (PTFE) particles, trifluorochloroethylene resin particles, hexafluoropropylene resin particles, vinyl fluoride resin particles, vinylidene fluoride resin particles, difluorodichloroethylene resin particles, copolymer resin particles containing these units, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin particles, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin particles. Among these, when the outermost layer of the photosensitive layer is formed by coating, polytetrafluoroethylene (PTFE) fine particles are preferred from the viewpoint of dispersibility and dispersion stability in the coating liquid.

[0015] Examples of the fluorine-based resin fine particles include the following commercially available products. Examples of PTFE resin microparticles include Daikin Industries, Ltd.'s product names: Lubron L-2, L-5, L-5F, Kitamura Co., Ltd.'s product names: KTL-500F, KTL-1N, KTL-2N, Asahi Glass Co., Ltd.'s product name: FLUON PTFE L173J, Techno Chemical Co., Ltd.'s product name: microdispers-200, Soken Chemical & Engineering Co., Ltd.'s product name: MP-300, and Mitsui DuPont Fluorochemicals Co., Ltd.'s product name: TLP-10F-1. Examples of PFA resin fine particles include MP-101, a product of DuPont-Mitsui Fluorochemicals Co., Ltd. Examples of FEP resin fine particles include product name: 120-JR manufactured by Mitsui DuPont Fluorochemicals Co., Ltd.

[0016] (Average primary particle size) The fluorine-based resin fine particles have an average primary particle size of 0.1 to 3.0 μm. It is preferable that the average primary particle diameter of the fluororesin fine particles is within the above range, since the dispersion stability of the fine particles in the coating liquid droplets during coating formation is good, and good image quality can be obtained in image formation on the photoreceptor. If the average primary particle size of the fluororesin particles is less than 0.1 μm, the particles will aggregate severely, making dispersion extremely difficult, and the stability of the dispersion will be reduced, making it difficult to control the surface properties.On the other hand, if the primary particle size of the fluororesin particles exceeds 3.0 μm, image quality defects will be more likely to occur. The average primary particle size of the fluorine-based resin fine particles is more preferably 0.25 to 0.5 μm. In the present disclosure, the average primary particle diameter refers to a value measured using, for example, a laser diffraction / scattering particle size analyzer (manufactured by Nikkiso Co., Ltd., model: Microtrac MT3000II) in a measurement solution diluted with the same solvent as the dispersion liquid in which the fine particles are dispersed.

[0017] (Content) The higher the content of fluorine-based resin particles in the outermost layer of the photoreceptor, the better the abrasion resistance of the photoreceptor, but if the content of fluorine-based resin particles exceeds 20% by mass, the deterioration of the electrical properties of the photoreceptor becomes significant and the photoreceptor may not be able to withstand practical use in an image-forming device.On the other hand, if the content of fluorine-based resin particles is less than 5%, the improvement in the abrasion resistance of the photoreceptor may not be achieved.

[0018] <Ten-point surface roughness Rz and average spacing of irregularities Sm> A 4 mm wide area at the center of the charged area in the axial direction of the photoreceptor on the surface of the outermost layer has a ten-point surface roughness Rz of 0.05 to 0.25 μm and an average spacing Sm of irregularities of 50 to 150 μm as defined in JIS-B-0601 (1994). By defining the surface roughness of the photosensitive member within the above range, the effect of reducing friction between the cleaning blade and the photosensitive member can be obtained.

[0019] The ten-point average roughness Rz means the difference in μm between the average elevation of the fifth highest peak and the average elevation of the fifth deepest valley, measured in a direction perpendicular to the average line from a line that is parallel to the average line and does not cross the cross-sectional curve, in a portion of a reference length taken from the cross-sectional curve of the outermost surface layer of the photosensitive member; the measurement method will be explained in the Examples. The average spacing Sm of irregularities means the average length of the average line corresponding to one peak and one adjacent peak in a portion of a reference length extracted from the cross-sectional curve of the outermost surface layer of the photosensitive member, and the method for measuring this will be described in the Examples.

[0020] If the ten-point mean roughness Rz exceeds 0.25 μm, poor cleaning is likely to occur, whereas if the ten-point mean roughness Rz is less than 0.05 μm, the friction reduction effect may not be obtained. The ten-point average roughness Rz is preferably 0.12 to 0.22 μm. Furthermore, when the spacing Sm between the projections and recesses is within the above range, the friction-reducing effect is likely to be obtained throughout the life of the roller. If the spacing Sm between the projections and recesses exceeds 150 μm, when the tops of the projections wear down due to long-term use, a wide flat portion is generated at the top, increasing the contact area with the cleaning blade, which may reduce the friction-reducing effect. On the other hand, if the spacing Sm between the projections and recesses is less than 50 μm, the number of contact points with the cleaning blade increases, and the friction-reducing effect may not be obtained. The preferable spacing Sm between the projections and recesses is 90 to 120 μm.

[0021] <Ratio of ten-point surface roughness Rz to the average spacing of irregularities Sm, Sm / Rz> The ratio Sm / Rz of the ten-point surface roughness Rz to the average spacing Sm of the irregularities is preferably 300-700. The definition of the ratio Sm / Rz means defining the load applied to each contact point with the cleaning blade. When the ratio Sm / Rz is in the above range, the load applied to the contact point with the cleaning blade is appropriate, and both cleaning performance and wear resistance can be achieved. If the ratio Sm / Rz exceeds 700, the load applied to one point becomes large, which can increase friction. On the other hand, if the ratio Sm / Rz is too small, less than 300, the load is too small, which can cause poor cleaning. The ratio Sm / Rz is more preferably 400-600.

[0022] <Contact angle with pure water> The surface of the outermost layer has a contact angle with pure water of 100° or more. A contact angle of 100° or more makes it possible to provide a photoreceptor that does not experience cleaning failure throughout its life, even if it is a wear-resistant photoreceptor. On the other hand, if the contact angle is too large, it becomes difficult for the photoreceptor and toner to adhere to each other during image formation. The preferred contact angle is 90 to 120°. The method for measuring the contact angle will be specifically explained in the Examples.

[0023] The contact angle with pure water can be controlled by adding silicone oil or a resin having a siloxane skeleton to the outermost layer of the photoreceptor, that is, by adding silicone oil or a resin having a siloxane skeleton when preparing a coating liquid for forming an outermost layer such as a charge transport layer. An example of silicone oil is SH200, a product of Dow Toray Co., Ltd. When the outermost layer is a charge transport layer, the appropriate amount of silicone oil to be added is 0.1 to 0.5% by mass based on the charge transport material. Furthermore, an example of a resin having a siloxane skeleton is SD Polyca SIA8001-20, a product name of Sumika Polycarbonate Co., Ltd. The amount of resin added is suitably 5 to 15% of the binder resin of the outermost surface layer. In both cases of silicone oil and resin having a siloxane skeleton, when the outermost layer is a charge transport layer, it is preferable to add it at the same time as the charge transport material and binder resin.

[0024] <Glass transition temperature Tg of photosensitive layer> The photosensitive layer preferably has a glass transition temperature Tg of 100 to 120°C. If the glass transition temperature Tg of the photosensitive layer is too low, below 100°C, the abrasion resistance of the photosensitive member may be reduced. On the other hand, if the glass transition temperature Tg of the photosensitive layer is too high, above 120°C, the abrasion resistance will be good, but the surface of the photosensitive member will be difficult to refresh, which may result in poor image quality. The glass transition temperature Tg of the photosensitive layer is more preferably 105 to 115°C.

[0025] <Na or K element in the outermost surface layer> The outermost surface layer preferably contains 0.01 to 20 ppm of Na element or K element. The present inventors have conducted extensive research to optimize the dispersibility of fluororesin microparticles in the coating solutions for the photosensitive layer and the surface layer thereof, and have found that the uniformity of dispersion of the fluororesin microparticles in the layer is improved by bringing the dispersion into contact with a soda-lime glass material in the process of preparing the coating solution. The presence of metal oxides with high contact electrification, such as sodium oxide, potassium oxide, calcium oxide, magnesium oxide, and aluminum oxide, in soda-lime glass is thought to charge the fluororesin microparticles in the coating solution, and these metal oxides are adsorbed onto the surface of the fluororesin microparticles, improving the dispersion stability of the fluororesin microparticles. It has been found that the presence of sodium and potassium components, which have high contact electrification, contributes significantly to dispersion stability. By specifying the content of sodium or potassium within the above range, dispersion stability can be improved without affecting photoreceptor properties. Therefore, the outermost layer of the photoreceptor of the present disclosure is preferably a layer obtained through a manufacturing process in which it is brought into contact with a material containing a metal oxide.

[0026] If the Na content is less than 0.1 ppm or the K content is less than 0.01 ppm, there is almost no contribution to the dispersion stability of the fluororesin microparticles. On the other hand, if the Na content exceeds 20 ppm or the K content exceeds 10 ppm, the dispersibility of the fluororesin microparticles is good, but when charges are transported within the surface layer, the worn-out areas become charge trap sites, hindering charge movement, which can lead to a deterioration in sensitivity. The content of Na element is more preferably 0.1 to 0.6 ppm. The content of the K element is more preferably 0.1 to 0.6 ppm. The contents of Na element, K element, and Ca element and Mg element described later can be measured by, for example, measuring the charge transport layer of the photoreceptor using an ICP emission spectrophotometer (manufactured by Thermo Fisher Scientific, model: iCAP-6500).

[0027] <Ca, Al, or Mg elements in the outermost surface layer> The outermost surface layer preferably contains 0.01 to 10 ppm of Ca element, 0.01 to 8 ppm of Al element, and 0.01 to 4 ppm of Mg element. Soda-lime glass also contains calcium, aluminum, and magnesium as its constituents. Although their content is inferior to that of sodium and potassium, they are known to contribute to improving the dispersion stability of fluororesin microparticles. By limiting the content of Ca, Al, or Mg to the above ranges, dispersion stability can be improved without affecting the photoreceptor characteristics. Although Ca, Al and Mg have a smaller difference in electronegativity between oxygen atoms than Na and K, they are effective in improving the dispersion stability of fluorine-based resin particles.

[0028] If the content of Ca, Al, or Mg is less than 0.01 ppm, it makes almost no contribution to the dispersion stability of the fluororesin microparticles. On the other hand, if the content of Ca exceeds 10 ppm, the content of Al exceeds 8 ppm, or the content of Mg exceeds 4 ppm, the dispersibility of the fluororesin microparticles will be good, but when charges are transported within the surface layer, the worn-out areas will act as charge trap sites, hindering charge movement and possibly leading to a deterioration in sensitivity. The content of Ca element and Al element is more preferably 0.01 to 0.6 ppm. The content of Mg element is more preferably 0.01 to 0.5 ppm.

[0029] <Silica fine particles> The outermost surface layer preferably further contains silica fine particles. Inorganic filler particles may be added to the charge transport layer to improve abrasion resistance, etc. The inorganic filler particles are contained in such a manner that the total amount of the inorganic filler particles and the fluorine-based resin particles is 5 to 17 wt %, more preferably 8 to 12 wt %, of the total solid components in the charge transport layer. An example of the inorganic particles is silica particles.

[0030] (material) Examples of silica particles used in the outermost surface layer include dry silica particles and wet silica particles. Examples of dry silica particles include combustion silica (fumed silica) obtained by burning a silane compound, and deflagration silica obtained by explosively burning metallic silicon powder. Examples of wet silica particles include wet silica particles obtained by the neutralization reaction of sodium silicate and mineral acid (precipitation silica synthesized and agglomerated under alkaline conditions, and gel-process silica particles synthesized and agglomerated under acidic conditions), colloidal silica particles (silica sol particles) obtained by polymerizing acidic silicic acid in an alkaline state, and sol-gel silica particles obtained by hydrolysis of organic silane compounds (e.g., alkoxysilanes). Among these, combustion-processed silica particles, which have a low void structure and a small number of silanol groups on the surface, are desirable as silica particles from the viewpoint of suppressing image defects due to the generation of residual potential and other deterioration of electrical properties (suppressing deterioration of fine-line reproducibility). Furthermore, when the toner is treated with silica fine particles, such as dimethyldichlorosilane or hexamethyldisilazane, the best electrophotographic properties can be exhibited.

[0031] (Average primary particle size) The silica particles preferably have a number average primary particle size of 30 nm or less. If the number average primary particle diameter exceeds 30 nm, the aggregate structure formed in the photosensitive layer becomes large, which may easily cause problems with poor cleaning. On the other hand, if the number average primary particle diameter is less than 7 nm, the silica particles have a strong aggregation force, making them difficult to disintegrate, and their dispersibility may decrease. Therefore, the number average primary particle diameter of the silica particles is more preferably 7 to 30 nm. The number average primary particle diameter is a measurement value of the Feret's direction average diameter obtained by observing silica particles under a scanning electron microscope at a magnification of 30,000 to 300,000 times, for example 10,000 times, randomly selecting 100 particles as primary particles, and analyzing the image.

[0032] (1) Electrophotographic photoreceptor The photosensitive layer is preferably a laminated photosensitive layer in which a single-layer photosensitive layer, a charge generation layer, and a charge transport layer are laminated, or a laminated photosensitive layer in which a charge generation layer, a first charge transport layer, and a second charge transport layer are laminated, and the outermost layer is preferably a single-layer photosensitive layer, a charge transport layer, and a second charge transport layer, respectively.

[0033] FIG. 1 is a schematic cross-sectional view showing the configuration of a main part of a photoreceptor according to an embodiment of the present disclosure. The photoreceptor 1 is a laminated photoreceptor (also referred to as a "function-separated photoreceptor") having an undercoat layer 15 provided on a conductive support 11, and a laminated photosensitive layer (also referred to as a "function-separated photosensitive layer") 14 having a laminated structure in which a charge generation layer 12 containing a charge generation substance and a charge transport layer 13 containing a charge transport substance and a binder resin that binds the substance are laminated in this order. Each component of the photoreceptor 1 will be described below.

[0034] <Conductive substrate 11> The conductive substrate 11 is also called a conductive support, and functions as an electrode for the photoreceptor and as a support member, and the material constituting the conductive substrate 11 is not particularly limited as long as it is a material used in the relevant technical field. Specific examples include metal materials such as aluminum, aluminum alloys, copper, zinc, stainless steel, and titanium, as well as polymer materials such as polyethylene terephthalate, nylon, and polystyrene, whose surfaces are laminated with metal foil, subjected to metal vapor deposition, or vapor-deposited or coated with a layer of a conductive compound such as a conductive polymer, tin oxide, or indium oxide, as well as hard paper and glass. Among these, aluminum is preferred from the viewpoint of ease of processing, and aluminum alloys such as JIS 3003, JIS 5000, and JIS 6000 series are particularly preferred. The shape of the conductive support is not limited to a cylindrical (drum) shape as shown in FIG. 2, but may be a sheet shape, a columnar shape, an endless belt shape, or the like. Furthermore, the surface of the conductive support may be subjected to anodizing film treatment, surface treatment with chemicals or hot water, coloring treatment, or diffuse reflection treatment such as surface roughening, as needed, to prevent interference fringes caused by laser light, within a range that does not affect image quality.

[0035] <Undercoat layer (also called "intermediate layer") 15> The photoreceptor of the present disclosure preferably includes an undercoat layer 15 between the conductive substrate 11 and the photosensitive layer 14 . The undercoat layer 15, also referred to as an intermediate layer, has the function of preventing charge injection from the conductive substrate 11 into the photosensitive layer 14. Therefore, even if a defect exists in the conductive substrate 11 or the photosensitive layer 14, it is possible to prevent a decrease in the chargeability of a small area of ​​the photosensitive layer 14 due to the defect. As a result, it is possible to suppress a decrease in surface charge in areas other than those that should be erased by exposure, and to effectively prevent the occurrence of image defects due to image fogging and the like. Furthermore, by providing the undercoat layer 15, irregularities present on the surface of the conductive substrate 11 can be covered to form a uniform surface, thereby improving the film-forming properties of the photosensitive layer 14. Furthermore, the adhesion between the conductive substrate 11 and the photosensitive layer 14 can be improved, preventing or suppressing peeling of the photosensitive layer 14 from the conductive substrate 11. For this undercoat layer 15, for example, a resin layer made of a resin material or an anodized aluminum layer can be used.

[0036] Examples of resin materials constituting the undercoat layer 15 include polyethylene resin, polypropylene resin, polystyrene resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane resin, epoxy resin, polyester resin, melamine resin, silicone resin, polyvinyl butyral resin, polyvinylpyrrolidone resin, polyacrylamide resin, and polyamide resin, as well as copolymer resins containing two or more of the repeating units constituting these resins. Other resin materials constituting the undercoat layer 15 include casein, gelatin, polyvinyl alcohol, cellulose, nitrocellulose, and ethyl cellulose. These resins can be used alone or in combination.

[0037] Among these resins, it is preferable to use polyamide resins, and it is particularly preferable to use alcohol-soluble nylon resins. Preferred examples of alcohol-soluble nylon resins include so-called nylons such as 6-nylon, 6,6-nylon, 6,10-nylon, 11-nylon, 2-nylon, and 12-nylon, and chemically modified nylons such as N-alkoxymethyl-modified nylon and N-alkoxyethyl-modified nylon.

[0038] The undercoat layer 15 may contain metal oxide fine particles as filler fine particles in order to impart a charge adjusting function. Examples of metal oxide fine particles include titanium oxide fine particles, aluminum oxide fine particles, aluminum hydroxide fine particles, and tin oxide fine particles. The average particle size of the filler particles is preferably about 0.01 to 0.3 μm, and more preferably about 0.02 to 0.1 μm.

[0039] The undercoat layer 15 can be formed, for example, by dissolving or dispersing the resin in an appropriate solvent to prepare a coating liquid for the undercoat layer (resin liquid for the undercoat layer), applying this coating liquid to the surface of the conductive substrate 11, and drying it. When filler particles such as the metal oxide particles are added to the undercoat layer 15, the filler particles may be dispersed in the coating liquid for the undercoat layer.

[0040] The solvent for the coating solution for the undercoat layer is water, various organic solvents, or a mixture thereof. Specific examples of such solvents include a single solvent consisting of water, alcohols such as methanol, ethanol, and butanol, a mixture of water and alcohols, a mixture of two or more alcohols, a mixture of acetone or dioxolane with alcohols, and a mixture of alcohols with halogenated organic solvents such as dichloroethane, chloroform, and trichloroethane. Among these solvents, non-halogenated organic solvents are preferably used in consideration of the global environment.

[0041] Methods for dispersing filler particles in a coating solution include, for example, dispersion methods using a ball mill, sand mill, attritor, vibration mill, ultrasonic disperser, paint shaker, etc. Alternatively, a dispersion method using a media-less dispersion device that passes a coating solution containing filler particles through micropores at ultrahigh pressure can also be used. In such dispersion methods, the filler particles are dispersed in the coating solution by the extremely strong shear force that occurs when the coating solution is passed through the micropores. This allows the filler particles to be dispersed more stably in the coating solution.

[0042] Examples of coating methods for the undercoat layer coating solution include spraying, bar coating, roll coating, blade coating, ring coating, and dip coating. Among these coating methods, dip coating is particularly preferred. Here, the dip coating method is a method in which a substrate is immersed in a coating tank filled with a coating solution and then withdrawn from the coating tank at a constant speed or a gradually changing speed to form a layer on the surface of the substrate. This method is relatively simple and has advantages in terms of productivity and cost, and is therefore widely used in the production of photoreceptors.

[0043] The thickness of the undercoat layer 15 is preferably about 0.01 to 20 μm, and more preferably about 0.05 to 10 μm. By setting the thickness of the undercoat layer 15 at or above the lower limit, the irregularities of the conductive substrate 11 can be reliably covered, resulting in the formation of an undercoat layer 15 with a uniform and highly flat surface. This allows the undercoat layer 15 to fully perform its functions. As a result, charge injection from the conductive substrate 11 into the photosensitive layer 14 can be more reliably prevented, preventing a decrease in the chargeability of the photosensitive layer 14. On the other hand, by setting the thickness of the undercoat layer 15 at or below the upper limit, the undercoat layer 15 can be formed with precision, for example, by a dip coating method. This allows the photosensitive layer 14 to be uniformly formed on the undercoat layer 15, resulting in a photoreceptor 1 with sufficient sensitivity.

[0044] <Charge generation layer 15> The charge generation layer 12 provided on the undercoat layer 15 contains, as a main component, a charge generation material that generates charges by absorbing light. The amount of the charge generation material contained in the charge generation layer 12 is not particularly limited, but is preferably about 40 to 80% by mass.

[0045] As the charge generating material, various organic photoconductive materials and various inorganic photoconductive materials can be used alone or in combination of two or more. Examples of organic photoconductive materials include azo pigments such as monoazo pigments, bisazo pigments, and trisazo pigments, indigo pigments such as indigo and thioindigo, perylene pigments such as perylene imide and perylene anhydride, polycyclic quinone pigments such as anthraquinone and pyrenequinone, phthalocyanine compounds such as metal phthalocyanines (e.g., oxotitanium phthalocyanine compounds), metal-free phthalocyanines, squarylium dyes, pyrylium salts, thiopyrylium salts, and triphenylmethane dyes. On the other hand, examples of inorganic photoconductive materials include selenium and amorphous silicon.

[0046] Among these charge-generating materials, phthalocyanine compounds are preferred, and oxotitanium phthalocyanine compounds are more preferred. Here, "oxotitanium phthalocyanine compounds" refers to oxotitanium phthalocyanine and its derivatives. Examples of oxotitanium phthalocyanine derivatives include oxotitanium phthalocyanines in which at least one hydrogen atom in the aromatic ring contained in the phthalocyanine group is substituted with a substituent such as a halogen atom (e.g., a chlorine atom or a fluorine atom), a nitro group, a cyano group, or a sulfonic acid group, and oxotitanium phthalocyanines in which a ligand such as a chlorine atom is coordinated to the titanium atom, which is the central metal.

[0047] The oxotitanium phthalocyanine compound preferably has a specific crystal structure. Specifically, the oxotitanium phthalocyanine compound preferably has a crystal structure that exhibits a diffraction peak at a Bragg angle (2θ±0.2°) of at least 27.2° in an X-ray diffraction spectrum for Cu-Kα characteristic X-rays (wavelength 1.54 Å). Here, the Bragg angle 2θ is the angle between incident X-rays and diffracted X-rays, and represents the so-called diffraction angle. By using such an oxotitanium phthalocyanine compound as a charge-generating material, a photoreceptor 1 with even better sensitivity and resolution can be obtained. Furthermore, the oxotitanium phthalocyanine compound has excellent charge-generating and charge-injecting capabilities. Therefore, the oxotitanium phthalocyanine compound generates a large amount of charge by absorbing light, and can efficiently inject the generated charge into the charge-transport layer 13 without accumulating it internally. The oxotitanium phthalocyanine compounds can be prepared, for example, according to the preparation methods described in Phthalocyanine Compounds by Moser, Frank H. and Arthur L. Thomas, Reinhold Publishing Corp., New York, 1963. For example, oxotitanium phthalocyanine can be produced by synthesizing dichlorotitanium phthalocyanine by heating and melting phthalonitrile and titanium tetrachloride, or by heating and reacting them in a suitable solvent such as α-chloronaphthalene, and then hydrolyzing the resulting mixture with a base or water. Oxotitanium phthalocyanine can also be produced by reacting isoindoline with a titanium tetraalkoxide such as tetrabutoxytitanium under heating in a suitable solvent such as N-methylpyrrolidone.

[0048] The charge generation layer 12 can be formed, for example, by vacuum-depositing a charge generation substance on the surface of the conductive substrate 11, or by dissolving or dispersing the charge generation substance in a suitable solvent and applying a coating liquid for the charge generation layer to the surface of the conductive substrate 11. Among these, a preferred method is to prepare a coating liquid for the charge generation layer by dispersing a charge generation substance in a binder resin liquid obtained by mixing (dissolving or dispersing) a binder resin, which serves as a binder, in a solvent, and then applying the resulting coating liquid to the surface of the conductive substrate 11. This method will be described below.

[0049] Examples of binder resins used in the charge generating layer 12 include resins such as polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate resin, polyarylate resin, phenoxy resin, polyvinyl butyral resin, polyvinyl chloride resin, and polyvinyl formal resin, as well as copolymer resins containing two or more of the repeating units that constitute these resins. Specific examples of copolymer resins include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. The binder resin is not limited to these resins, but may be any commonly used resin. The above resins may be used alone or in combination of two or more.

[0050] Examples of solvents for the charge generating layer coating solution include halogenated hydrocarbons such as dichloromethane and dichloroethane, alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran and dioxane, alkyl ethers of ethylene glycol such as 1,2-dimethoxyethane, aromatic hydrocarbons such as benzene, toluene, and xylene, and aprotic polar solvents such as N,N-dimethylformamide and N,N-dimethylacetamide. Among these solvents, non-halogenated organic solvents are preferred for environmental reasons. These solvents may be used alone or in combination.

[0051] In the charge generation layer 12 containing a charge generation material and a binder resin, the ratio (M1 / M2) of the mass M1 of the charge generation material to the mass M2 of the binder resin is preferably 10 / 100 to 400 / 100. When the ratio (M1 / M2) is 10 / 100 or more, a decrease in the sensitivity of the photoreceptor 1 can be prevented or suppressed. On the other hand, when the ratio (M1 / M2) is 400 / 100 or less, the charge generation layer 12 can maintain sufficient film strength. Furthermore, in this case, the charge generation material is sufficiently dispersed in the charge generation layer 12, preventing the formation of coarse particles. Therefore, the surface charge is maintained high in areas other than those to be erased by exposure, and image defects such as image fogging caused by toner adhering to a white background and forming minute black dots can be effectively prevented.

[0052] Examples of methods for applying the coating liquid for the charge generating layer include spraying, bar coating, roll coating, blade coating, ring coating, and dip coating. Among these coating methods, the dip coating method described in the application method for the coating liquid for the undercoat layer is particularly preferred. When the charge generating layer 12 is formed by coating, the stability of the coating liquid can be improved by adding an antioxidant or an ultraviolet absorber to the coating liquid for the charge generating layer.

[0053] The thickness of the charge generation layer 12 is preferably about 0.05 to 5 μm, and more preferably about 0.1 to 1 μm. By making the thickness of the charge generation layer 12 equal to or greater than the lower limit, the charge generation efficiency due to light absorption by the charge generation layer 12 is improved, thereby increasing the sensitivity of the photoreceptor 1. On the other hand, by making the thickness of the charge generation layer 12 equal to or less than the upper limit, charge transfer within the charge generation layer 12 does not become the rate-limiting factor in the process of erasing the surface charge of the photosensitive layer 14, and the sensitivity of the photoreceptor 1 can be increased.

[0054] <Charge transport layer 13> The charge transport layer has the function of receiving and transporting charges generated by the charge generating material, and is obtained by incorporating the charge transport material into a binder resin. In addition, in this disclosure, fluorine-based resin particles are added to the charge transport layer, which is the outermost layer of the photoreceptor, for the purpose of improving wear resistance.

[0055] The charge transport material is not particularly limited, and any compound used in the art can be used. Specific examples of the charge transport material include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene derivatives, and benzidine derivatives. As the binder resin constituting the charge transport layer, resins containing polycarbonate or polyarylate as a main component, which are well known in the art, are preferably selected because of their excellent transparency and printing durability. In addition to the polycarbonate resin, other binder resins, such as vinyl polymer resins (e.g., polymethyl methacrylate resin, polystyrene resin, polyvinyl chloride resin), copolymer resins containing two or more of the repeating units constituting these, or polyester resins, polyestercarbonate resins, polysulfone resins, phenoxy resins, epoxy resins, silicone resins, polyarylate resins, polyamide resins, polyether resins, polyurethane resins, polyacrylamide resins, and phenolic resins, or copolymer resins having a polycarbonate skeleton and a polydimethylsiloxane skeleton, can also be used. Thermosetting resins obtained by partially crosslinking these resins can also be used. In particular, silicone resins and resins having a siloxane skeleton are preferred because they increase surface smoothness, resulting in a water contact angle of 100° or more on the surface of the photosensitive layer, preventing poor cleaning throughout the product's life. These resins may be used alone or in combination of two or more. The term "polycarbonate resin is the main component" means that the polycarbonate resin accounts for the highest weight percent of the total binder resins constituting the charge transport layer, and preferably ranges from 50 to 90 weight percent. The binder resin as the second component refers to a binder resin that can be used in an amount of 10 to 50% by weight, which is lower than the content of the polycarbonate resin, relative to the total weight of the binder resins constituting the charge transport layer. The weight ratio of the charge transport material to the binder resin in the charge transport layer is preferably in the range of 10 / 18 to 10 / 10.

[0056] The filler particles can be dispersed using a known dispersing machine such as a homogenizer or a high-pressure collision type. In particular, a high-pressure collision type disperser is preferred from the viewpoint of reducing damage to the fine particles. An example of a high-pressure collision type disperser is a high-pressure jet emulsifier / disperser. This high-pressure jet emulsifier / disperser is a wet atomization device that emulsifies, disperses, and surface treats particles without damaging them by forcing the processing liquid (slurry, emulsion, dispersion, etc.) into a fine flow path using a high-pressure plunger pump or similar, and then spraying and colliding it at high pressure from the discharge port by adjusting a special valve at the discharge part. Therefore, high-pressure jet dispersers are used to emulsify, disperse, or pulverize materials to be dispersed by adjusting the pressure when sprayed from the discharge port to cause collisions between high-pressure jet liquids and between the high-pressure jet liquid and the wall surface of the device. Therefore, as the above-mentioned high-pressure jet disperser, a device can be used that is composed of a high-pressure pump, a jig with multiple small-diameter orifices connected to it by piping, and a jig that is processed so that the liquids collide with each other when they are discharged from the orifices. Examples of such devices include Starburst from Sugino Machine Co., Ltd., Nanovaita from Yoshida Kikai Kogyo Co., Ltd., and Microfluidizer from Microfluidics. In addition, since heat generated by liquid collisions tends to accumulate as the number of collision passes increases, it is desirable to attach a cooling device to the dispersion circuit. The high pressure referred to in the present disclosure preferably means 10 to 300 MPa, which is determined largely by the discharge volume and discharge pressure of the high-pressure pump, the diameter and length of the orifice, and the viscosity of the solvent and the substance to be dispersed. If the treatment pressure is lower than 10 MPa, the collision energy between the liquids is insufficient, and the particles cannot be dispersed to the desired particle size. On the other hand, if the treatment pressure is higher than 300 MPa, the collision energy between the liquids becomes too high, which may cause deterioration of the dispersion and explosion of the dispersion, etc. A more preferable treatment pressure is 50 to 150 MPa.

[0057] In addition, a plasticizer or leveling agent may be added to the charge transport layer to improve film-forming properties and surface smoothness. Examples of the plasticizer include dibasic acid esters such as phthalates, fatty acid esters, phosphate esters, chlorinated paraffins, and epoxy-type plasticizers. Examples of the leveling agent include silicone-based leveling agents. Silicone-based leveling agents are particularly preferred because they maintain a water contact angle of 100° or greater even when binder resins that are not capable of imparting surface smoothness are used, thereby preventing poor cleaning throughout the layer's life. The photosensitive layer may contain an antioxidant or an ultraviolet absorber. In particular, the charge transport layer may contain an antioxidant or an ultraviolet absorber, which can improve the stability of the coating solution when each layer is formed by coating. Furthermore, it is particularly preferable to add an antioxidant to the charge transport layer, which can reduce the deterioration of the photosensitive layer due to oxidizing gases such as ozone and nitrogen oxides. Examples of the antioxidant include phenolic compounds, hydroquinone compounds, tocopherol compounds, and amine compounds. Among these, hindered phenol derivatives, hindered amine derivatives, or mixtures thereof are preferably used.

[0058] Examples of solvents include aromatic hydrocarbons such as benzene, toluene, xylene, and monochlorobenzene; halogenated hydrocarbons such as dichloromethane and dichloroethane; ethers such as tetrahydrofuran, dioxane, and dimethoxymethyl ether; and aprotic polar solvents such as N,N-dimethylformamide. Furthermore, if necessary, solvents such as alcohols, acetonitrile, or methyl ethyl ketone can also be added. These solvents can be used alone or in combination.

[0059] Examples of methods for applying the coating solution for the charge transport layer include spraying, bar coating, roll coating, blade coating, ring coating, and dip coating. Among these coating methods, the dip coating method is particularly advantageous in various respects as described above, and can therefore also be used to form the charge transport layer 16.

[0060] The thickness of the charge transport layer is not particularly limited, but is preferably about 5 to 50 μm, and more preferably about 10 to 40 μm. If the thickness of the charge transport layer is less than 5 μm, the charge retention ability of the photoreceptor surface may decrease, whereas if the thickness of the charge transport layer is more than 50 μm, the resolution of the photoreceptor may decrease.

[0061] (2) Image forming apparatus 100 The image forming apparatus of the present disclosure comprises at least the photosensitive member of the present disclosure, a charging means for charging the photosensitive member, an exposure means for exposing the charged photosensitive member to light to form an electrostatic latent image, a developing means for developing the electrostatic latent image to form a toner image, and a transfer means for transferring the toner image onto a recording medium, and may also comprise means selected from a fixing means for fixing the transferred toner image onto the recording medium to form an image, a cleaning means for removing and recovering toner remaining on the photosensitive member, and a discharging means for discharging surface charges remaining on the photosensitive member. The image forming apparatus and its operation according to the present disclosure will be described below with reference to the drawings, but the present disclosure is not limited to the following description.

[0062] 2 is a schematic side view showing the configuration of a main part of the image forming apparatus according to an embodiment of the present disclosure. 2 includes the photoreceptor 1 of the present disclosure, an exposure means (semiconductor laser) 31, a charging means (charger) 32, a developing means (developer) 33, a transfer means (transfer charger) 34, a conveyor belt (not shown), a fixing means (fixer) 35, and a cleaning means (cleaner) 36. Reference numeral 51 denotes a recording medium (recording paper or transfer paper).

[0063] Photoreceptor 1 is rotatably supported on the main body of image forming apparatus 100 and is driven to rotate around rotation axis 44 in the direction of arrow 41 by driving means (not shown). The driving means includes, for example, an electric motor and a reduction gear, and transmits its driving force to a conductive support constituting the core of photoreceptor 1, thereby driving photoreceptor 1 to rotate at a predetermined peripheral speed. Charging means (charger) 32, exposure means 31, developing means (developer) 33, transfer means (transfer charger) 34, and cleaning means (cleaner) 36 are provided in this order along the outer circumferential surface of photoreceptor 1 from upstream to downstream in the direction of rotation of photoreceptor 1, as indicated by arrow 41.

[0064] The charger 32 is a charging means for uniformly charging the outer peripheral surface of the photosensitive member 1 to a predetermined potential. The exposure means 31 has a semiconductor laser as a light source, and irradiates the surface of the photoreceptor 1 between the charger 32 and the developer 33 with a laser beam light output from the light source, thereby exposing the charged outer peripheral surface of the photoreceptor 1 in accordance with image information. The light is repeatedly scanned in the main scanning direction, that is, the direction of extension of the rotation axis 44 of the photoreceptor 1, and these are focused to sequentially form electrostatic latent images on the surface of the photoreceptor 1. In other words, the amount of charge on the photoreceptor 1, which has been uniformly charged by the charger 32, differs depending on whether or not it is irradiated with the laser beam, thereby forming an electrostatic latent image.

[0065] The developing device 33 is a developing means that develops the electrostatic latent image formed on the surface of the photosensitive member 1 by exposure with a developer (toner), and is provided facing the photosensitive member 1 and includes a developing roller 33a that supplies toner to the outer peripheral surface of the photosensitive member 1, and a casing 33b that supports the developing roller 33a rotatably around a rotation axis parallel to the rotation axis 44 of the photosensitive member 1 and contains a developer containing toner in its internal space.

[0066] The transfer charger 34 is a transfer means that transfers a toner image, which is a visible image formed on the outer peripheral surface of the photosensitive member 1 by development, onto transfer paper 51, which is a recording medium that is supplied between the photosensitive member 1 and the transfer charger 34 from the direction of arrow 42 by a transport means (not shown). The transfer charger 34 is, for example, a contact-type transfer means that includes a charging means and transfers the toner image onto the transfer paper 51 by applying a charge of the opposite polarity to that of the toner to the transfer paper 51.

[0067] The cleaner 36 is a cleaning means that removes and collects toner remaining on the outer peripheral surface of the photoreceptor 1 after the transfer operation by the transfer charger 34, and includes a cleaning blade 36a that separates the toner remaining on the outer peripheral surface of the photoreceptor 1, and a collection casing 36b that contains the toner separated by the cleaning blade 36a. The cleaner 36 is also provided together with a static elimination lamp (not shown).

[0068] The image forming apparatus 100 is also provided with a fixing device 35, which is a fixing means for fixing the transferred image, downstream of the transport of the transfer paper 51 that has passed between the photoreceptor 1 and the transfer charger 34. The fixing device 35 is provided with a heating roller 35a having a heating means (not shown), and a pressure roller 35b that is provided opposite the heating roller 35a and is pressed against the heating roller 35a to form a contact portion. Reference numeral 37 denotes a separating means for separating the transfer paper from the photosensitive member, and reference numeral 38 denotes a casing that houses the above-mentioned means of the image forming apparatus.

[0069] The image forming operation by this image forming apparatus 100 is performed as follows. First, when the photosensitive member 1 is rotated in the direction of arrow 41 by the driving means, the surface of the photosensitive member 1 is uniformly charged to a predetermined positive potential by the charger 32, which is located upstream of the image-forming point of the light by the exposure means 31 in the direction of rotation of the photosensitive member 1.

[0070] Next, light corresponding to image information is irradiated from exposure means 31 onto the surface of photoreceptor 1. This exposure removes surface charge from the areas of photoreceptor 1 that have been irradiated with light, creating a difference in surface potential between the areas that have been irradiated with light and the areas that have not been irradiated with light, forming an electrostatic latent image. Toner is supplied from a developing device 33, which is located downstream in the rotational direction of the photosensitive member 1 from the imaging point of the light by the exposure means 31, to the surface of the photosensitive member 1 on which the electrostatic latent image is formed, thereby developing the electrostatic latent image and forming a toner image.

[0071] In synchronization with the exposure of the photoreceptor 1, transfer paper 51 is supplied between the photoreceptor 1 and transfer charger 34. The transfer charger 34 imparts a charge of opposite polarity to that of the toner to the supplied transfer paper 51, and the toner image formed on the surface of the photoreceptor 1 is transferred onto the transfer paper 51. The transfer paper 51 onto which the toner image has been transferred is transported by the transport means to the fixing device 35, and is heated and pressurized as it passes through the contact area between the heating roller 35a and the pressure roller 35b of the fixing device 35, and the toner image is fixed onto the transfer paper 51 to form a solid image. The transfer paper 51 on which the image has been formed in this way is ejected to the outside of the image forming apparatus 100 by the transport means.

[0072] Meanwhile, any toner remaining on the surface of photoreceptor 1 after the transfer of the toner image by transfer charger 34 is peeled off and collected from the surface of photoreceptor 1 by cleaner 36. The charge on the surface of photoreceptor 1 from which the toner has been removed in this way is removed by light from the discharging lamp, and the electrostatic latent image on the surface of photoreceptor 1 disappears. Thereafter, photoreceptor 1 is rotated again, and the series of operations starting with charging are repeated again to form images continuously. [Example]

[0073] The present disclosure will be specifically described below with reference to examples and comparative examples based on the drawings, but the present invention is not limited to these examples. The physical properties of the photoreceptors obtained in the examples and comparative examples and their raw materials were measured by the following methods.

[0074] (1) Measurement of the ten-point surface roughness Rz and the average spacing Sm of the surface roughness of the photoreceptor Using a surface roughness measuring device (Tokyo Seimitsu Co., Ltd., model: Surfcom1400D), the ten-point surface roughness Rz (μm) and the average spacing Sm (μm) of irregularities are measured in a 4 mm wide area in the center of the axially charged area of ​​the outermost surface layer (charge transport layer) of the photosensitive member using a method with a reference length of 0.8 mm, a cutoff wavelength of 0.8 mm, a measurement speed of 0.1 mm / sec, and a Gaussian cutoff type. These Rz and Sm correspond to the ten-point surface roughness Rz and the average spacing of irregularities Sm defined in JIS-B-0601 (1994).

[0075] (2) Measurement of the contact angle of the outermost surface of the photoreceptor with pure water Using a contact angle meter (Kyowa Interface Science Co., Ltd., Model: CA-DT·A) and pure water (temperature 20°C) as a reagent, measure the contact angle (°) of the outermost layer (charge transport layer) of the photoreceptor (center of the axial direction of the photoreceptor) in an environment of 20°C temperature and 50% humidity.

[0076] (3) Measurement of the glass transition temperature Tg of the photosensitive layer A DSC curve is measured by heating 1 g of a sample at a heating rate of 10°C / min using a differential scanning calorimeter (Seiko Electronics Co., Ltd. (now Hitachi High-Tech Science Corporation), model number: DSC6200) in accordance with Japanese Industrial Standards (JIS) K7121-1987. In the obtained DSC curve, the glass transition temperature (Tg) is determined as the temperature at the intersection of a straight line extending the high-temperature side baseline of the endothermic peak corresponding to the glass transition toward the low-temperature side and a tangent drawn from the rising part of the peak to the apex of the curve at the point where the gradient is maximum. The sample was obtained by making a 1 cm square scratch on the outermost surface layer with a cutter knife or the like and peeling it off.

[0077] (4) Measurement of metal element concentration in the outermost surface layer of the photoreceptor The contents of Na, K, Ca and Mg elements in the outermost surface layer (charge transport layer) of the photoreceptor are measured using an ICP emission spectrometer (manufactured by Thermo Fisher Scientific, model: iCAP-6500). The sample was obtained by making a 1 cm square scratch on the outermost surface layer with a cutter knife or the like and peeling it off.

[0078] Example 1 (Preparation of Undercoat Layer) 3 parts by mass of titanium oxide (manufactured by Ishihara Sangyo Kaisha, Ltd., product name: TYPAQUE (registered trademark) TTO-D-1) and 2 parts by mass of polyamide resin (manufactured by Toray Industries, Inc., product name: AMILAN (registered trademark) CM8000) were added to 25 parts by mass of methyl alcohol, and the mixture was dispersed using a paint shaker for 8 hours to prepare 3 kg of a coating solution for the undercoat layer. The obtained coating liquid for the undercoat layer was filled into a coating tank, and a cylindrical aluminum substrate having a diameter of 30 mm and a length of 357 mm was immersed as the conductive substrate 11 and then removed.The obtained coating film was allowed to dry naturally, forming an undercoat layer 15 having a thickness of 1 μm on the conductive substrate 11.

[0079] (Preparation of Charge Generation Layer) Next, 1 part by mass of titanyl phthalocyanine as a charge-generating substance, which has an X-ray diffraction spectrum showing a major peak at a Bragg angle (2θ±0.2°) of 27.2° for X-rays of CuKα 1.541 Å, and 1 part by mass of butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BM-2) as a binder resin, were mixed with 98 parts by mass of methyl ethyl ketone, and the mixture was dispersed for 8 hours using a paint shaker to prepare 3 kg of a coating liquid for the charge-generating layer. The obtained coating liquid for the charge generating layer was applied to the surface of the previously formed undercoat layer 15 using the same immersion method as used to form the undercoat layer, and the resulting coating film was allowed to dry naturally to form a charge generating layer 12 with a film thickness of 0.3 μm.

[0080] (Preparation of charge transport layer) Next, 4.8 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.2 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-2) as fluororesin fine particles were heat-treated in an oven at 150° C. for 30 minutes. The obtained tetrafluoropolyethylene resin microparticles were mixed in a polypropylene container together with 0.34 g of a fluorine-based dispersant (manufactured by Toa Gosei Co., Ltd., product name: GF-400) and 25.5 g of tetrahydrofuran, and the mixture was stirred for 30 hours using a stirrer (manufactured by Shibata Scientific Co., Ltd., model: M-103) and a stirring blade to obtain a fluorine-based resin microparticle dispersion.

[0081] The resulting fluorine-based resin fine particle dispersion contained a compound having the following formula: [ka] A suspension with a solid content of 24 mass % was prepared by mixing 15.3 g of a triphenylamine compound (TPD) represented by the formula (manufactured by Tokyo Chemical Industry Co., Ltd., product name: D2448), 27.6 g of a polycarbonate resin (manufactured by Teijin Chemical Co., Ltd., product name: TS2050) as a binder resin, 0.0031 g of silicone oil, and 126.5 g of tetrahydrofuran. The obtained suspension was subjected to a dispersion process by passing it through a wet emulsification dispersion device (Microfluidizer, model: M-110P) five times at a set pressure of 100 MPa to prepare 200 g of a coating liquid for the charge transport layer.

[0082] The obtained charge transport layer coating liquid was applied to the surface of the previously formed charge generation layer 12 by the same dipping method as used to form the undercoat layer, and the resulting coating film was dried at a temperature of 130°C for 90 minutes to form a charge transport layer 13 with a thickness of 28 μm, thereby forming a photosensitive layer 14 consisting of the charge generation layer 12 and the charge transport layer 13. In this manner, a photoreceptor 1 having the structure shown in FIG.

[0083] Example 2 In preparing the coating solution for the charge transport layer, the amount of fluorine-based resin fine particles was changed from 4.8 g to 2.4 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.2 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-2), and 2.4 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.5 μm, manufactured by Kitamura Co., Ltd., product name: KTL-500F) was added. Except for this, photoreceptor 1 was obtained in the same manner as in Example 1.

[0084] Example 3 Photoreceptor 1 was obtained in the same manner as in Example 1, except that in preparing the coating solution for the charge transport layer, the amount of fluorine-based resin fine particles was changed from 4.8 g to 4.3 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.2 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-2), and 0.5 g of silica fine particles (average primary particle diameter: approximately 16 nm, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972V) was added.

[0085] Example 4 Photoreceptor 1 was obtained in the same manner as in Example 1, except that in preparing the coating solution for the charge transport layer, 4.8 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.2 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-2) was replaced with 4.8 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.2 μm, manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd., product name: TLP10F-1) as the fluororesin fine particles.

[0086] Example 5 Photoreceptor 1 was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the charge transport layer, 4.8 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 2.5 μm, manufactured by Kitamura Co., Ltd., product name: KTL-2F) was used as the fluorine-based resin fine particles instead of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.2 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-2).

[0087] Example 6 In preparing the coating solution for the charge transport layer, the amount of fluorine-based resin microparticles was changed from 4.8 g to 2.9 g, the fluorine-based dispersant from 0.34 g to 0.20 g, the tetrahydrofuran solvent for the fluorine-based resin microparticle dispersion from 25.5 g to 17.3 g, the charge transport material from 27.6 g to 16.0 g, the polycarbonate resin binder resin from 27.6 g to 28.9 g, and the tetrahydrofuran solvent for the coating solution for the charge transport layer, which is added together with the charge transport material and binder resin, from 126.5 g to 134.7 g, except for this, photoreceptor 1 was obtained in the same manner as in Example 1.

[0088] Example 7 Photoreceptor 1 was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the charge transport layer, the amount of fluorine-based resin microparticles was changed from 4.8 g to 8.6 g, the fluorine-based dispersant was changed from 0.34 g to 0.61 g, the tetrahydrofuran solvent for the fluorine-based resin microparticle dispersion was changed from 25.5 g to 42.0 g, the charge transport material was changed from 27.6 g to 13.8 g, the polycarbonate resin binder resin was changed from 27.6 g to 24.9 g, and the tetrahydrofuran solvent for the coating solution for the charge transport layer, which was added together with the charge transport material and binder resin, was changed from 126.5 g to 110.0 g.

[0089] Example 8 Photoreceptor 1 was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the charge transport layer, the fluorine-based dispersant was changed from 0.34 g to 0.14 g, the tetrahydrofuran used as the solvent for the fluorine-based resin microparticle dispersion was changed from 25.5 g to 24.8 g, the charge transport material was changed from 27.6 g to 15.4 g, the polycarbonate resin binder resin was changed from 27.6 g to 27.7 g, and the tetrahydrofuran used as the solvent for the coating solution for the charge transport layer, which was added together with the charge transport material and binder resin, was changed from 126.5 g to 127.2 g.

[0090] Example 9 Photoreceptor 1 was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the charge transport layer, the binder resin was changed from 27.6 g to 24.8 g of polycarbonate resin (manufactured by Teijin Chemicals Co., Ltd., product name: TS2050) and 2.8 g of polyethylene resin (manufactured by Toyobo Co., Ltd., product name: Vylon (registered trademark) GK-360) was added.

[0091] Example 10 Photoreceptor 1 was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the charge transport layer, the binder resin was changed from 27.6 g to 24.8 g of polycarbonate resin (manufactured by Teijin Chemical Co., Ltd., product name: TS2050) and 2.8 g of polyethylene resin (manufactured by Mitsubishi Gas Chemical Co., Inc., product name: FPC-0820) was added.

[0092] Example 11 Photoreceptor 1 was obtained in the same manner as in Example 8, except that in the preparation of the coating liquid for the charge transport layer, the number of times of passing through the dispersing device was changed from 5 times to 8 times.

[0093] Example 12 In preparing the coating solution for the charge transport layer, the fluorine-based dispersant was changed from 0.34 g to 0.48 g, the tetrahydrofuran used as the solvent for the fluorine-based resin microparticle dispersion was changed from 25.5 g to 26.1 g, the charge transport material was changed from 27.6 g to 15.3 g, the polycarbonate resin binder resin was changed from 27.6 g to 27.5 g, the tetrahydrofuran used as the solvent for the coating solution for the charge transport layer added together with the charge transport material and binder resin was changed from 126.5 g to 125.9 g, and the number of times of passing through the dispersing device was changed from 5 to 3. Except for this, photoreceptor 1 was obtained in the same manner as in Example 1.

[0094] Example 13 Photoreceptor 1 was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the charge transport layer, the binder resin was changed from 27.6 g to 13.8 g of polycarbonate resin (manufactured by Teijin Chemicals Co., Ltd., product name: TS2050) and 13.8 g of polyethylene resin (manufactured by Toyobo Co., Ltd., product name: Vylon (registered trademark) GK-360) was added.

[0095] Example 14 Photoreceptor 1 was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the charge transport layer, the binder resin was changed from 27.6 g to 13.8 g of polycarbonate resin (manufactured by Teijin Chemical Co., Ltd., product name: TS2050) and 13.8 g of polyethylene resin (manufactured by Mitsubishi Gas Chemical Co., Inc., product name: FPC-0820) was added.

[0096] Example 15 Photoreceptor 1 was obtained in the same manner as in Example 8, except that in preparing the coating liquid for the charge transport layer, the polypropylene container for mixing the fluorine-based resin particle dispersion was changed to a soda-lime glass container.

[0097] Example 16 Photoreceptor 1 was obtained in the same manner as in Example 15, except that in preparing the coating liquid for the charge transport layer, the stirring time for the fluorine-based resin fine particle dispersion with a stirring blade was changed from 30 hours to 72 hours.

[0098] Example 17 Photoreceptor 1 was obtained in the same manner as in Example 15, except that in preparing the coating liquid for the charge transport layer, 0.024 g of glass abrasion powder (soda-lime glass, average primary particle diameter: approximately 0.10 μm) was added when the charge transport material and binder resin were added.

[0099] (Comparative Example 1) Photoreceptor 1 was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the charge transport layer, 4.8 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.12 μm, manufactured by 3M Japan Limited, product name: TF9207Z) was used as the fluorine-based resin fine particles instead of 4.8 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.2 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-2).

[0100] (Comparative Example 2) Photoreceptor 1 was obtained in the same manner as in Example 1, except that in preparing the coating liquid for the charge transport layer, 4.8 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 3.1 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-5F) was used as the fluorine-based resin fine particles instead of 4.8 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.2 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-2).

[0101] (Comparative Example 3) In preparing the coating solution for the charge transport layer, the amount of tetrafluoroethylene resin particles (average primary particle diameter: approximately 0.2 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-2) was changed from 4.8 g to 1.9 g as the fluorine-based resin particles, the amount of fluorine-based dispersant was changed from 0.34 g to 0.13 g, the amount of tetrahydrofuran as the solvent for the fluorine-based resin particle dispersion was changed from 25.5 g to 13.2 g, the amount of charge transport material was changed from 27.6 g to 16.4 g, the amount of polycarbonate resin as the binder resin was changed from 27.6 g to 29.5 g, and the amount of tetrahydrofuran as the solvent for the coating solution for the charge transport layer, which was added together with the charge transport material and the binder resin, was changed from 126.5 g to 138.8 g. Except for this, the photoreceptor 1 was obtained in the same manner as in Example 1.

[0102] Comparative Example 4 In preparing the coating solution for the charge transport layer, the photoreceptor 1 was obtained in the same manner as in Example 1, except that in the preparation of the coating solution for the charge transport layer, the fluorine-based resin fine particles were changed from 4.8 g to 10.1 g of tetrafluoropolyethylene resin fine particles (average primary particle diameter: approximately 0.2 μm, manufactured by Daikin Industries, Ltd., product name: Lubron L-2), the fluorine-based dispersant was changed from 0.34 g to 0.71 g, the solvent for the fluorine-based resin fine particle dispersion was changed from 25.5 g to 48.1 g of tetrahydrofuran, the charge transport material was changed from 27.6 g to 13.3 g, the binder resin polycarbonate resin was changed from 27.6 g to 23.9 g, and the solvent for the coating solution for the charge transport layer, which was added together with the charge transport material and the binder resin, was changed from 126.5 g to 103.9 g of tetrahydrofuran.

[0103] (Comparative Example 5) Photoreceptor 1 was obtained in the same manner as in Example 12, except that in the preparation of the coating liquid for the charge transport layer, the number of times of passing through the dispersing device was changed from 5 times to 8 times.

[0104] (Comparative Example 6) Photoreceptor 1 was obtained in the same manner as in Example 8, except that in the preparation of the coating liquid for the charge transport layer, the number of times of passing through the dispersing device was changed from five to three.

[0105] (Comparative Example 7) Photoreceptor 1 was obtained in the same manner as in Example 1, except that silicone oil was not added in the preparation of the coating liquid for the charge transport layer.

[0106] (Comparative Example 8) Photoreceptor 1 was obtained in the same manner as in Example 15, except that in the preparation of the coating liquid for the charge transport layer, the stirring time for the fluorine-based resin fine particle dispersion with a stirring blade was changed from 30 hours to 50 hours.

[0107] Comparative Example 9 Photoreceptor 1 was obtained in the same manner as in Example 17, except that in preparing the coating liquid for the charge transport layer, the stirring time for the fluorine-based resin fine particle dispersion with a stirring blade was changed from 30 hours to 48 hours.

[0108] [evaluation] The photoreceptors prepared in Examples 1 to 17 and Comparative Examples 1 to 9 were evaluated for (1) sensitivity (sensitivity stability), (2) printing durability, (3) cleaning resistance, and (4) blade reversal as follows. (1) Sensitivity (sensitivity stability) was evaluated.

[0109] (1) Sensitivity (sensitivity stability) The photoreceptor to be evaluated was mounted in the unit of a digital copier (Model MX-B455W, manufactured by Sharp Corporation) that had been modified for the test, the developing unit was removed from the digital copier, and a surface potential meter (Model 344, manufactured by Trek Japan) was attached to the developing section instead. In an environment of normal temperature and humidity (N / N) with a temperature of 25°C and a relative humidity of 50%, the surface potential of the photoreceptor without exposure to laser light was adjusted to -600V, and the surface potential VL(-V) of the black background was measured in that state. The sensitivity was evaluated based on the obtained VL according to the following criteria: The smaller the absolute value of the surface potential VL, the higher the sensitivity was evaluated.

[0110] <Evaluation criteria> VG:|VL|<100 Can be used without problems in high-speed multifunction devices or printers that require high sensitivity G: 100≦|VL|<120 Can be used without problems on medium to low speed multifunction devices or printers NG:120≦|VL|<140 If you are using a slow, inexpensive multifunction device or printer, the density may be a little low, but it can be used without any problems. B:140 ≤ |VL| Poor sensitivity results in low concentration, which is problematic for practical use

[0111] (2) Printing durability The photoreceptor to be evaluated was mounted in the unit of a digital copier (model MX-B455W, manufactured by Sharp Corporation) that had been modified for testing, and a developing unit was attached. The pressure with which the cleaning blade of the cleaning unit contacted the photoreceptor, the so-called cleaning blade pressure, was set to 21 gf / cm (2.05 x 10 -1 A print durability test was conducted by printing a character test chart (ISO19752) on 350,000 sheets of recording paper in an environment of 25°C temperature and 8% humidity. The thickness of the photosensitive layer at the start of the printing durability test and after 350,000 images were formed was measured using a film thickness measuring device (Filmetrics, Model: F-20-EXR). The amount of film scraped off (amount of film reduction) per 100,000 rotations of the photosensitive drum was calculated from the difference between the film thickness at the start of the printing durability test and the film thickness after 350,000 images were formed, and the printing durability was evaluated based on the obtained amount of film scraped off according to the following criteria. The greater the amount of scraping, the worse the printing durability was evaluated to be.

[0112] <Evaluation criteria> VG: Amount of scraping <1.00μm / 100,000 revolutions Can be used without problems in multifunction devices or printers that require a long lifespan G: 1.00 μm / 100,000 revolutions≦Abrasion amount<1.10 μm / 100,000 revolutions Although the amount of scraping is somewhat large, it can be used without any problems unless it is used in a multifunction machine or printer that requires a long life. NB: 1.10 μm / 100,000 revolutions≦Abrasion amount<1.20 μm / 100,000 revolutions Although there is a large amount of scraping, it can be used without problems if it is an inexpensive multifunction machine or printer. B: 1.20 μm / 100,000 revolutions ≦ scraping amount There is a large amount of scraping, which causes problems in practical use.

[0113] (3) Cleaning resistance In order to confirm the level of cleaning defects occurring on the photoreceptor after the printing durability test, the photoreceptor after 350,000 images was formed on was attached to the unit of a test digital copier (Model: MX-B455W, manufactured by Sharp Corporation), and one 100% density untransferred image was printed on an A4 sheet of paper. Immediately after that, the copier was forcibly stopped, and the surface of the photoreceptor was visually observed, and the cleaning ability (degree of cleaning defects) was evaluated according to the following criteria.

[0114] <Evaluation criteria> VG: No occurrence G: One or two cleaning defects Can be used without problems except for multifunction devices or printers that require high image quality NB: 3 to 5 cleaning defects Can be used without problems with inexpensive multifunction devices or printers B: Many (6 or more) cleaning defects Problems in actual use

[0115] (4) Blade reversal We checked whether or not blade reversal occurred until 350,000 sheets were printed.

[0116] (5) Image quality Under a normal temperature and humidity (N / N) environment with a temperature of 25°C and a relative humidity of 50%, images were formed using a total of four patterns: a 1-dot written pattern, a 1-dot missing pattern, and a 1-line periodic pattern (in the main scanning and sub-scanning directions), and the initial image quality was evaluated according to the following criteria.

[0117] <Evaluation criteria> VG: High-quality images can be obtained with good reproducibility in both cases. G: 2-3 patterns are clearly distinguishable, and there is no problem in practical use. Can be used without problems except for multifunction devices or printers that require high image quality NB: Only one of the patterns can be distinguished, and it is judged that the image quality is deteriorated in actual use. Can be used without problems with inexpensive multifunction devices or printers B: None of the patterns can be distinguished, making it unusable. Problems in actual use

[0118] (6) Overall Judgment Based on the above evaluation results, an overall evaluation was made according to the following criteria. VG: VG rating in all categories, very good G: Some items may be rated G, but all items are rated G or higher Long-lasting, high-quality multifunction devices or printers can be used without problems. NB: Some items may be rated G, but all items are rated NB or higher Can be used without problems with inexpensive multifunction devices or printers B: Any item has a B rating and cannot be used. The constituent materials and physical properties of the photoreceptor are shown in Table 1, and the evaluation results obtained are shown in Tables 2 and 3.

[0119] [Table 1]

[0120] [Table 2]

[0121] [Table 3]

[0122] The results in Tables 1 and 2-3 reveal the following. (1) An electrophotographic photoreceptor having at least a photosensitive layer on a conductive substrate, wherein the outermost surface layer of the photosensitive layer contains fluororesin fine particles having an average primary particle diameter of 0.1 to 3.0 μm in a proportion of 5 to 20 mass % in the outermost surface layer, and a 4 mm wide region at the center of the charged region in the axial direction of the photoreceptor on the surface of the outermost surface layer has a ten-point surface roughness Rz of 0.05 to 0.25 μm as defined in JIS-B-0601 (1994) and an average spacing Sm of irregularities of 50 to 150 μm, and the surface of the outermost surface layer has a contact angle with pure water of 100° or more (Examples 1 to 17). These photoreceptors have excellent printing durability and cleanability, do not cause blade reversal, and do not cause image defects or deterioration of sensitivity.

[0123] (2) When the average primary particle diameter of the fluororesin fine particles is too small (Comparative Example 1), dispersibility deteriorates, resulting in defects that lead to poor images. On the other hand, when the average primary particle diameter is too large (Comparative Example 2), the presence of particles with a large average primary particle diameter leads to poor images. On the other hand, in Example 3, particle aggregation was observed, although it did not result in noticeable poor images, and in Example 4, poor images were observed that were due to particles with a large average primary particle diameter and did not pose any problems in practical use. Therefore, the preferred range of the average primary particle diameter is 0.25 to 2.0 μm.

[0124] (3) When the content of fluorine-based resin microparticles is too low (Comparative Example 3), printing durability is significantly deteriorated, and when the content of fluorine-based resin microparticles is too high (Comparative Example 4), sensitivity is significantly deteriorated and poor image quality is observed. Example 6 shows slightly inferior printing durability compared to Example 1, and Example 7 shows deterioration in sensitivity and image quality compared to Example 1, although it is within a range that does not cause problems in practical use. Therefore, it is concluded that the preferred range of the content of fluorine-based resin microparticles is 8 to 15 mass %.

[0125] (4) There is a general correlation between the ten-point mean roughness Rz and the average spacing Sm of irregularities, and as Rz decreases, Sm increases, and as Rz increases, Sm decreases. When Rz is too small and Sm is too large (Comparative Example 5), friction with the blade becomes very large, causing blade reversal. When Rz is too large and Sm is too small (Comparative Example 6), cleaning failure occurs. Compared with Example 11, cleaning failure was observed, although it was not a problem in practical use. Compared with Example 11, Example 12 showed inferior printing durability, which is thought to be due to increased friction between the photosensitive member and the blade. It is believed that a more preferable range for Rz is 0.12 to 0.22 μm, and a more preferable range for Sm is 90 to 120 μm.

[0126] (5) When the contact angle of the outermost surface layer of the photoreceptor with pure water is too small (Comparative Example 7), the cleaning property deteriorates.

[0127] (6) Example 15 and Comparative Example 8 Even when soda-lime glass as a metal oxide is brought into contact with the charge transport layer coating solution on the outermost surface of the photoreceptor during preparation, if the content (concentration) of the metal oxide is within the specified range (Example 15), the printing durability, cleaning properties, image quality, and sensitivity are good and blade reversal does not occur. On the other hand, if the content (concentration) of the metal oxide is higher than the specified range (Comparative Example 8), the sensitivity is significantly reduced. [Explanation of symbols]

[0128] 1. Electrophotographic photoreceptor 11 Conductive substrate 12 Charge generation layer 13 Charge transport layer 14 Photosensitive layer 15 Undercoat layer (intermediate layer) 31 Exposure means (semiconductor laser) 32 Charging means (charger) 33 Developing means (developer) 33a Developing roller 33b casing 34 Transfer means (transfer charger) 35 Fixing means (fixing device) 35a Heating roller 35b Pressure roller 36 Cleaning means (cleaner) 36a cleaning blade 36b Recovery casing 37 Separation means 38 Housing 41, 42 arrow mark 44 Rotation axis 51 Recording media (recording paper or transfer paper) 100 Image forming device (laser printer)

Claims

1. An electrophotographic photoreceptor comprising at least a photosensitive layer on a conductive substrate, the outermost layer of the photosensitive layer contains fluorine-based resin fine particles having an average primary particle diameter of 0.2 to 3.0 μm in a proportion of 5 to 20% by mass in the outermost layer; the outermost surface layer contains 0.01 to 20 ppm of Na element or K element, a 4 mm-wide region at the center of a charged region in the axial direction of the electrophotographic photosensitive member on the surface of the outermost layer has a ten-point surface roughness Rz of 0.05 to 0.25 μm and an average spacing Sm of irregularities of 50 to 150 μm, as defined in JIS-B-0601 (1994); The surface of the outermost layer has a contact angle with pure water of 100° or more. An electrophotographic photoreceptor characterized by:

2. 2. The electrophotographic photoreceptor according to claim 1, wherein the ratio Sm / Rz of the ten-point surface roughness Rz to the average spacing Sm of the irregularities is 300 to 700.

3. 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a glass transition temperature Tg of 100 to 120.degree.

4. 3. The electrophotographic photoreceptor according to claim 1, wherein the outermost layer contains 0.01 to 0.6 ppm of Na element or K element.

5. 3. The electrophotographic photoreceptor according to claim 1, wherein the outermost layer contains 0.01 to 0.6 ppm of Ca element, 0.01 to 0.6 ppm of Al element, and 0.01 to 0.5 ppm of Mg element.

6. A method for producing an electrophotographic photoreceptor according to claim 1 or 2, a step of contacting the material with a metal oxide to prepare a coating liquid for the surface layer 10. A method for producing an electrophotographic photosensitive member, comprising:

7. 3. The electrophotographic photoreceptor according to claim 1, wherein the outermost layer further contains silica fine particles.

8. 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is a single-layer photosensitive layer, a multi-layer photosensitive layer in which a charge generation layer and a charge transport layer are laminated, or a multi-layer photosensitive layer in which a charge generation layer, a first charge transport layer and a second charge transport layer are laminated, and the outermost layer is the single-layer photosensitive layer, the charge transport layer or the second charge transport layer, respectively.

9. 10. An image forming apparatus comprising at least the electrophotographic photosensitive member according to claim 1, a charging unit that charges the electrophotographic photosensitive member, an exposure unit that exposes the charged electrophotographic photosensitive member to light to form an electrostatic latent image, a developing unit that develops the electrostatic latent image to form a toner image, and a transfer unit that transfers the toner image onto a recording medium.

Images