Electrophotographic photoreceptor and image forming apparatus including the same

Abstract

To provide an electrophotographic photoreceptor that is excellent in print resistance, has high mechanical strength, and prevents the occurrence of an image defect associated with partial damage to a cleaning blade and image shading unevenness associated with uneven wear of the cleaning blade, and an image forming apparatus including the electrophotographic photoreceptor.SOLUTION: The above-mentioned problem is solved by an electrophotographic photoreceptor. An outermost surface layer of the electrophotographic photoreceptor includes inorganic compound fine particles. The inorganic compound fine particles have a number average primary particle diameter of 10-40 nm, and is dispersed uniformly in the outermost surface layer at a ratio of 7-18% by mass in the outermost surface layer. When the outermost surface layer is sliced in a lamination direction at a thickness of 70 nm, an obtained strip-shaped test piece is observed by a scanning transmission electron microscope, an obtained cross-sectional image is converted into an 8-bit binarized image, and 50 areas of 5 μm×5 μm observation visual fields of an obtained binarized image are arbitrary observed, the relationship of 0.5≤SAve / N≤2.0 is satisfied, and the maximum gap area when a space absent of the inorganic compound fine particles is taken as an equivalent circle diameter is 1.0 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrophotographic photoreceptor and an image forming apparatus having the same. More specifically, the present invention relates to an electrophotographic photoreceptor having excellent printing durability, high mechanical strength, and free from image defects caused by partial damage of a cleaning blade and image density unevenness caused by wear variation, and an image forming apparatus having the same. [Background technology]

[0002] In recent years, organic photoreceptors using organic photoconductive materials (herein referred to as "electrophotographic photoreceptors" or simply "photoreceptors") have been widely used as electrophotographic photoreceptors. However, due to the nature of the organic materials, the organic photoconductor has a sliding surface such as a cleaning blade around the photoconductor. motion Therefore, the surface is easily worn away. On the other hand, in recent years, with an increase in contact charging methods using roller charging and with the trend toward longer life, smaller size and higher speed of electrophotographic devices such as digital copiers and printers, the surface of the organic photoreceptor is more susceptible to wear and is exposed to even harsher conditions. As a means for overcoming the above-mentioned drawbacks, efforts have been made up to now to improve the mechanical properties (wear resistance, printing durability) of the material surface of the photoreceptor.

[0003] Specifically, the addition of inorganic fine particles such as silica or alumina (also simply referred to as "inorganic particles") as a filler to the outermost surface layer of the photoreceptor has been considered. For example, JP 2017-049519 A (Patent Document 1) discloses a laminated electrophotographic photoreceptor that includes a photosensitive layer including a charge generation layer containing a charge generation agent (also referred to as a "charge generation substance") and a charge transport layer containing a charge transport agent (also referred to as a "charge transport substance"), a binder resin, a phthalocyanine pigment, and silica particles, in which the charge transport layer is a single layer and is arranged as the outermost layer, the content of the silica particles is 0.5 parts by mass or more and 15 parts by mass or less relative to 100 parts by mass of the binder resin, and the average primary particle size of the silica particles is 50 nm or more and 150 nm or less.

[0004] Furthermore, JP 2001-066800 A (Patent Document 2) discloses an electrophotographic photoreceptor having at least a photosensitive layer on a conductive support, the outermost layer of which contains a modified polycarbonate copolymer resin containing a repeating unit represented by a specific general formula (1), a repeating unit represented by a specific general formula (2), and a repeating unit of a siloxane structure, and which contains silica fine particles having a volume average particle size of 0.005 μm or more and less than 0.05 μm.

[0005] Further, a method has been considered in which a curable protective layer (also called a "surface protective layer") is formed on the charge transport layer, and inorganic fine particles such as silica particles are added as a filler to the outermost surface layer. For example, JP 2012-108487 A (Patent Document 3) discloses an electrophotographic photoreceptor in which a photosensitive layer and a curable protective layer are sequentially provided on a conductive support, the curable protective layer contains a cured product of a radically polymerizable compound with three or more functionalities and a filler having a portion exposed from the surface of the curable protective layer, the surface of the curable protective layer has a raised portion that is raised along the surface of the filler, and when the radius of the filler contained in the curable protective layer is r and the film thickness of the curable protective layer is T, T>2r and formula (a): 100 × (number of fillers at a depth from the free surface of the curable protective layer to T / 2 / total number of fillers in the curable protective layer)≧70% is satisfied. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP2017-049519A [Patent Document 2] JP2001-066800A [Patent Document 3] JP2012-108487A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the above-mentioned prior art, it is difficult to simultaneously improve the abrasion resistance of the photoreceptor surface and obtain good cleaning properties. That is, even if a sea-island structure consisting of a sea part of binder resin and islands of inorganic particles is formed in the outermost layer of the photoreceptor, the distance between the islands becomes large due to aggregation of the inorganic particles, the islands become localized, and the wear of the sea part and the island part becomes extremely different. This causes damage to the cleaning blade, and uneven wear of the outermost layer causes color unevenness in the image, making it difficult to obtain stable image characteristics over a long period of time.

[0008] Therefore, an object of the present invention is to provide an electrophotographic photoreceptor having excellent printing durability, high mechanical strength, and free from image defects caused by partial damage to the cleaning blade and uneven image shading caused by wear variations, and an image forming apparatus equipped with the same. [Means for solving the problem]

[0009] As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that when the outermost layer of a photoreceptor contains inorganic compound microparticles having a specific number average primary particle diameter in a specific mass ratio and the inorganic compound microparticles are in a specific dispersed state, the above-mentioned problems can be solved while improving both the printing durability and cleaning properties of the photoreceptor, and have completed the present invention.

[0010] Thus, according to the present invention, there is provided an electrophotographic photoreceptor having a photosensitive layer in which at least a charge generating layer and a charge transport layer are laminated in this order on a conductive support, the outermost layer of the electrophotographic photoreceptor contains inorganic compound fine particles, the inorganic compound fine particles have a number average primary particle diameter of 10 to 40 nm and are uniformly dispersed in the outermost surface layer at a ratio of 7 to 18% by mass, The outermost surface layer was sliced ​​in the lamination direction to a thickness of 70 nm, and the obtained rectangular test piece was observed with a scanning transmission electron microscope. The obtained cross-sectional image was converted into an 8-bit binary image, and 50 areas of a 5 μm × 5 μm observation field of the obtained binary image were arbitrarily observed. When the following formula was obtained: 0.5≦S Ave / N≦2.0 (In the formula, S Ave is the area S (25 μm 2 ) is the average value of 50 regions of the ratio (%) of the occupied area of ​​the inorganic compound fine particles to the total solid content (g) of the outermost surface layer. and the maximum gap area when the space where the inorganic compound fine particles are not present is taken as a circle equivalent diameter is 1.0 μm or less. The electrophotographic photoreceptor is characterized in that

[0011] According to the present invention, there is also 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 formed by exposure to form a toner image, transfer means for transferring the toner image formed by development onto a recording medium, fixing means for fixing the transferred toner image on the recording medium to form an image, cleaning means for removing and recovering toner remaining on the electrophotographic photosensitive member, and discharging means for discharging surface charge remaining on the electrophotographic photosensitive member. Effect of the Invention

[0012] According to the present invention, it is possible to provide an electrophotographic photoreceptor having excellent printing durability and high mechanical strength, and free from image defects caused by partial breakage of a cleaning blade and uneven image density caused by wear variations, and an image forming apparatus equipped with the same. That is, in the photoreceptor of the present invention, as shown in Figure 3(a), it is believed that gentle intermolecular forces are formed by the inorganic compound microparticles in the outermost layer, and that a gentle aggregation structure like a uniform mesh structure in which the inorganic compound microparticles are interconnected throughout the entire outermost layer (islands: black parts in a sea of ​​binder resin (white parts)), which eliminates variation in the mechanical strength of the outermost layer, equalizes the load on the blade, and suppresses the progression of abrasive wear, making it possible to provide a photoreceptor with significantly improved printing durability and improved partial damage to the cleaning blade compared to conventional photoreceptors.

[0013] On the other hand, in conventional photoreceptors, as shown in Figure 3(b), an island structure (island part: black part) of silica filler (fine inorganic compound particles) is formed in the sea part (white part) of the binder resin in the photosensitive layer (outermost layer). However, the distance between the islands is large, and the silica filler is extremely localized in the island part. This results in an extremely different abrasion property between the sea part and the island part, which is thought to be the cause of partial damage to the cleaning blade. Patent Document 3 discloses the ratio of the projected area of ​​the filler portion contained in the cured protective layer to the projected area of ​​the portion where no filler is present, but does not disclose the probability of the presence of inorganic compound microparticles in the outermost surface layer as in the present invention.

[0014] The photoreceptor of the present invention exhibits the above-mentioned effects more effectively when any one of the following conditions (1) to (7) is satisfied. (1) In the observation field of view of 5 μm × 5 μm of the binarized image, inorganic compound particles are 0.005 μm 2 It has the following average size: (2) The inorganic compound fine particles are dispersed in a solution containing ε=1-rB / rS, where rB is the bulk density of the inorganic compound fine particles (g / cm 3 ) and rS is the true density of the inorganic compound particles (g / cm 3 )) and has a porosity ε of 0.96 to 0.98. (3) The outermost surface layer has a surface roughness Rz of 0.2 to 1.0 μm as defined by JIS-B-0601 (1994). (4) The inorganic compound fine particles are silica fine particles. (5) The silica fine particles are surface-treated with dimethyldichlorosilane or hexamethyldisilazane. (6) The outermost layer is a charge transport layer constituting a photosensitive layer, or a surface protective layer formed on a photosensitive layer. (7) An undercoat layer is provided between the conductive support and the photosensitive layer. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view showing a configuration of a main part of a photoreceptor of the present invention. [Diagram 2] 1 is a schematic side view illustrating a configuration of a main part of an image forming apparatus according to the present invention. [Diagram 3] FIG. 2A is a scanning transmission electron microscope image showing the dispersion state of inorganic compound fine particles in the outermost layer of the photoreceptor of the present invention, and FIG. 2B is a scanning transmission electron microscope image showing the dispersion state of inorganic compound fine particles in the outermost layer of a conventional photoreceptor. [Figure 4] 1 is an example of an 8-bit binarized image of a cross-sectional image of a photoreceptor of the present invention taken by a scanning transmission electron microscope. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (1) Electrophotographic Photoreceptor The photoreceptor of the present invention is an electrophotographic photoreceptor having a photosensitive layer in which at least a charge generating layer and a charge transport layer are laminated in this order on a conductive support, the outermost layer of the electrophotographic photoreceptor contains inorganic compound fine particles, the inorganic compound fine particles have a number average primary particle diameter of 10 to 40 nm and are uniformly dispersed in the outermost surface layer at a ratio of 7 to 18% by mass, The outermost surface layer was sliced ​​in the lamination direction to a thickness of 70 nm, and the obtained rectangular test piece was observed with a scanning transmission electron microscope. The obtained cross-sectional image was converted into an 8-bit binary image, and 50 areas of a 5 μm × 5 μm observation field of the obtained binary image were arbitrarily observed. When the following formula was obtained: 0.5≦S Ave / N≦2.0 (In the formula, S Ave is the area S (25 μm 2 ) is the average value of 50 regions of the ratio (%) of the occupied area of ​​the inorganic compound fine particles to the total solid content (g) of the outermost surface layer. and the maximum gap region, when the space where the inorganic compound fine particles are not present is taken as a circle-equivalent diameter, is 1.0 μm or less. First, the inorganic compound particles and their dispersion state in the outermost layer, i.e., 8-bit binary image analysis of a cross-sectional image of the outermost layer containing the inorganic compound particles taken by a scanning transmission electron microscope, will be described, and then each component of the photoreceptor will be described.

[0017] <Inorganic compound fine particles> The photoreceptor of the present invention contains inorganic compound fine particles as a filler in the outermost layer. The inorganic compound of the inorganic compound fine particles is silica (silicon dioxide: SiO 2 ), Alumina (Al 2 O 3 ), Celia (CeO 2 ), molybdenum oxide (MoO 3 ), titania (TiO 2 ), zirconia (ZrO 2 ), zinc oxide (ZnO), magnetite (Fe 3 O 4 ) and various forms of Fe 2 O 3 Iron oxide, niobium oxide (Nb 2 O 5 ), vanadium oxide (VO), tungsten oxide (WO 2 ) and tin oxide (SnO), and one of these can be used alone or as a mixture of two or more of them or as a mixed oxide. The chemical formula in parentheses is a representative oxide form, and there are also oxide forms that differ depending on the valence of the metal atom, and these are included in the present invention. Among the above oxides, from the viewpoint of abrasion resistance, silica, alumina, and titania are preferred, silica and alumina are more preferred, and from the viewpoint of electrical properties, silica is particularly preferred.

[0018] The silica fine particles preferably used in the present invention are not limited by the production method as long as they have the above number average primary particle diameter. Examples of the silica fine particles include dry-process silica particles such as fumed silica obtained by burning silicon tetrachloride and arc-process silica obtained by atomizing silica in the gas phase with high energy such as plasma; wet-process silica particles such as precipitated silica synthesized under alkaline conditions using an aqueous sodium silicate solution as a raw material and gel-process silica synthesized under acidic conditions; colloidal silica particles obtained by polymerizing acidic silicic acid to make it alkaline; sol-gel process silica particles obtained by hydrolysis of an organic silane compound.

[0019] <Number average primary particle diameter of inorganic compound fine particles> The inorganic compound fine particles as the filler of the present invention have a number average primary particle diameter of 10 to 40 nm. If the number average primary particle diameter of the inorganic compound fine particles is less than 10 nm, sufficient printing resistance may not be obtained. On the other hand, if the number average primary particle diameter of the inorganic compound fine particles exceeds 40 nm, problems such as poor cleaning may easily occur due to the increase in the aggregation structure formed in the photosensitive layer. The preferred number average primary particle diameter of the inorganic compound fine particles is 10 to 20 nm. The measurement method will be described in the examples.

[0020] <Content of inorganic compound fine particles> The inorganic compound fine particles as the filler are contained in the outermost surface layer at a ratio of 7 to 18% by mass and are uniformly dispersed. If the content of the inorganic compound fine particles is less than 7% by mass, the effect on abrasion resistance may not be sufficiently obtained. On the other hand, if the content of the inorganic compound fine particles exceeds 18% by mass, the dispersibility may not be sufficient, the aggregates may increase, and the cleaning property may deteriorate. The content of the inorganic compound particles in the outermost layer is preferably 7 to 12% by mass.

[0021] <Surface treatment of inorganic compound particles> The inorganic compound fine particles of the present invention are preferably surface-treated with a surface treatment agent in order to improve the electrical properties of the photoreceptor. When the inorganic compound fine particles are silica particles, examples of the surface treatment agent include hexamethyldisilazane, N-methyl-hexamethyldisilazane, N-ethyl-hexamethyldisilazane, hexamethyl-N-propyldisilazane, dimethyldichlorosilane, and polydimethylsiloxane. Among these surface treatment agents, the one with the best reactivity with the hydroxyl groups on the silica particle surface is Reduce As a result, deterioration of the electrical properties of the photoconductor due to moisture (humidity) can be suppressed, and therefore dimethyldichlorosilane and hexamethyldisilazane are particularly preferable.

[0022] In the present invention, the silica particles obtained by treating with the above-mentioned surface treatment agent can be used, but commercially available silica fine particles treated with a surface treatment agent can also be used. child Examples of such products include Nippon Aerosil Co., Ltd.'s product names: R972, R974, RX50, RX200, NX130, NX90G, NX90S, and NAX-50; Cabot Japan Co., Ltd.'s product names: TS610, TG709F, and TG6110G; and Admatechs Co., Ltd.'s product name: YA010C.

[0023] <Dispersion state of inorganic compound particles in the outermost surface layer> In the present invention, the phrase "the inorganic compound fine particles are uniformly dispersed in the outermost surface layer" means that the inorganic compound fine particles are contained in the outermost surface layer so as to satisfy the following dispersion conditions: Be This means that The dispersion state of inorganic compound fine particles in the outermost surface layer is analyzed based on an 8-bit binary image of a cross-sectional image of the outermost surface layer taken by a scanning transmission electron microscope. The photoreceptor of the present invention is prepared by slicing the outermost surface layer to a thickness of 70 nm in the lamination direction, observing the obtained rectangular test piece with a scanning transmission electron microscope, converting the obtained cross-sectional image into an 8-bit binary image, and observing 50 areas of a 5 μm×5 μm observation field of the obtained binary image at random, and the following formula is satisfied: 0.5≦S Ave / N≦2.0 (In the formula, S Ave is the area of ​​the observation region S (25 μm 2 ) is the average value of 50 regions of the ratio (%) of the occupied area of ​​inorganic compound fine particles to the total solid content (g) of the outermost surface layer. and the maximum gap region, when the space where the inorganic compound fine particles are not present is taken as a circle-equivalent diameter, is 1.0 μm or less. This image analysis will be explained in the Examples.

[0024] S Ave (%) is the percentage of inorganic compound particles relative to the total area (Stotal) of the observation field of the photosensitive layer. fortune telling This means the average ratio of the total area Ssa. S Ave / N is 0. 5 years old If the filler is less than 100%, the distribution of the filler in the photosensitive layer is insufficient, and sufficient printing durability may not be obtained. Ave If / N exceeds 2.0, the amount of filler is too high. stomach The unevenly distributed aggregates may cause a large amount of toner to be added to the cleaning blade during repeated image formation, which may result in poor cleaning performance. Preferred S Ave / N is equal to or greater than 1.0 and equal to or less than 1.8.

[0025] If the maximum gap area exceeds 1.0 μm, poor cleaning may occur due to insufficient distribution of the filler in the photosensitive layer, whereas the lower limit of the maximum gap area is about 0.2 μm.

[0026] <Average size of inorganic compound particles> In the observation field of view of 5 μm × 5 μm of the above binary image, the inorganic compound fine particles are 0.005 μm2 It is preferred that the particles have an average secondary size of: Average secondary size is 0.005μm 2 If the average secondary size exceeds 0.002 μm, the filler aggregate structure becomes large and cleaning failure may occur easily. 2 That's about it. The preferred average secondary size is 0.003 μm 2 The following is the result. The average particle size can be adjusted by dispersing a coating liquid containing fine inorganic compound particles, as described in the Examples.

[0027] <Porosity ε of inorganic fine particles> The inorganic compound fine particles are represented by the following formula: ε=1-rB / rS (wherein rB is the bulk density of the inorganic compound fine particles (g / cm 3 ) and rS is the true density of the inorganic compound particles (g / cm 3 ) is) It is preferable that the porosity ε is 0.96 to 0.98. The bulk density rB is the apparent density of an aggregate of inorganic compound fine particles. For example, the bulk density rB is calculated by adding an amount of inorganic compound fine particles to a measuring cylinder of 250 mL capacity, measuring the weight (g) of the aggregate after leaving it to stand for 2 minutes, and then calculating the volume (cm 3 ) to calculate the The true density rS is a physical property value specific to inorganic compounds of inorganic compound particles. For example, for silica, it is 2.2 g / cm 3 It is. If the porosity ε is 0.96, the printing durability may be poor, whereas if the porosity ε exceeds 0.98, the dispersion state of the filler in the photosensitive layer may be insufficient, resulting in poor cleaning.

[0028] <Surface roughness Rz of the outermost layer> The outermost layer of the photoreceptor of the present invention preferably has a surface roughness Rz of 0.2 to 1.0 μm as defined by JIS-B-0601 (1994). This is achieved by the appropriate and uniform aggregation of inorganic compound fine particles with a small particle size. Generally, the larger the particle size of the inorganic compound fine particles, the higher the wear resistance, but it causes chipping at the edge of the cleaning blade. In the present invention, by appropriately aggregating small inorganic compound fine particles, large particles are created, improving the wear resistance. Regarding chipping of the cleaning blade, since small particles are peeled off, it is possible to make it difficult to cause partial damage.

[0029] The surface roughness Rz is an index of the aggregation state of the inorganic compound fine particles in the outermost surface layer of the photoreceptor. The ten-point average roughness Rz defined in JIS-B-0601(1994) is the difference between the average value of the elevations of the top five peaks and the average value of the elevations of the bottom five valleys measured in the direction perpendicular to the average line from a straight line parallel to the average line and not crossing the cross-sectional curve in the portion extracted from the cross-sectional curve of the outermost surface layer of the photoreceptor by the reference length, expressed in μm. The measurement method will be described in the examples.

[0030] When the surface roughness Rz is less than 0.2 μm, the aggregation of the inorganic compound fine particles is not sufficient, and it is difficult to obtain an effect on the wear resistance. On the other hand, when the surface roughness Rz exceeds 1.0 μ m m, since the aggregation of the inorganic compound fine particles is too large, it is likely to cause a state where a part of the edge portion of the cleaning blade chips, and it becomes impossible to sufficiently clean the remaining toner, which may cause streak-like defects in the printed image. A more preferable surface roughness Rz is 0.2 to 0.5 μm.

[0031] <Photoreceptor> The photoreceptor of the present invention comprises a photosensitive layer in which at least a charge generation layer and a charge transport layer are sequentially laminated on a conductive support. Preferably, its outermost surface layer is the charge transport layer constituting the photosensitive layer or a surface protective layer formed on the photosensitive layer. Hereinafter, with reference to the drawings, the photoreceptor of the present invention in which the outermost surface layer is the charge transport layer will be described, but the present invention is not limited thereto. That is, when the outermost layer is a surface protective layer, the surface protective layer contains specific inorganic compound fine particles in a specific ratio and satisfies specific dispersion conditions, so that the photoreceptor exhibits the excellent effects of the present invention.

[0032] FIG. 1 is a schematic cross-sectional view showing the configuration of a main part of a photoreceptor of the present invention. The photoreceptor 1 is a laminated photoreceptor (also referred to as a "function-separated photoreceptor") in which an undercoat layer 18 is provided on a conductive support 11, and a photosensitive layer (also referred to as a "laminated photosensitive layer" or "function-separated photosensitive layer") 14 having a laminated structure in which a charge generation layer 15 containing a charge generation substance (not shown), a charge transport substance (not shown), a binder resin (not shown) that binds the charge transport substance, and a charge transport layer 16 containing inorganic compound particles 19 are laminated in this order. Each component will be described below.

[0033] <Conductive support 11> The conductive support has a function as an electrode for the photoreceptor and a function as a support member, and the material constituting the conductive support 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 are particularly preferred. The shape of the conductive support is not limited to a cylindrical shape (drum shape) as shown in FIG. 2, but may be a sheet shape, a columnar shape, an endless belt shape, or the like. In addition, 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 necessary, to prevent interference fringes caused by laser light, within a range that does not affect image quality.

[0034] <Undercoat layer (also called "middle layer") 18>

[0035] The photoreceptor of the present invention preferably includes an undercoat layer 18 between the conductive substrate 11 and the photosensitive layer 14 . The undercoat layer generally covers the unevenness of the surface of the conductive support to make it uniform, improves the film-forming property of the photosensitive layer, here the charge generating layer, suppresses the peeling of the photosensitive layer from the conductive support, and improves the adhesion between the conductive support and the photosensitive layer. Specifically, it prevents the injection of charges from the conductive support into the photosensitive layer, prevents the chargeability of the photosensitive layer from decreasing, and prevents fogging of the image (so-called black spots).

[0036] The undercoat layer can be formed, for example, by dissolving a binder resin in a suitable solvent to prepare a coating liquid for the undercoat layer, coating this coating liquid on the surface of the conductive support, and removing the organic solvent by drying.

[0037] Examples of the binder resin include the same binder resin as that contained in the photosensitive layer described below, as well as natural polymeric materials such as casein, gelatin, polyvinyl alcohol, and ethyl cellulose, and one or more of these can be used. The binder resin is required to have properties such as not dissolving or swelling in the solvent used when forming the photoreceptor layer on the undercoat layer, excellent adhesion to the conductive support, and flexibility. Therefore, among the above-mentioned binder resins, polyamide resins are preferred, and alcohol-soluble nylon resins are particularly preferred. Examples of alcohol-soluble nylon resins include homopolymer or copolymer nylons such as 6-nylon, 66-nylon, 610-nylon, 11-nylon, and 12-nylon, and resins obtained by chemically modifying nylons such as N-alkoxymethyl-modified nylons.

[0038] Examples of solvents for dissolving or dispersing resin materials include water, alcohols such as methanol, ethanol, and butanol, glymes such as methyl carbitol and butyl carbitol, chlorine-based solvents such as dichloroethane, chloroform, and trichloroethane, acetone, dioxolane, mixed solvents of two or more of these solvents, etc. Among these solvents, non-halogenated organic solvents are preferably used in consideration of the global environment.

[0039] The coating solution for the undercoat layer may contain inorganic compound fine particles. The inorganic compound fine particles of the undercoat layer have a different purpose from the inorganic compound fine particles of the outermost layer, and may be the same compound or different compounds. The inorganic compound fine particles can easily adjust the volume resistivity of the undercoat layer, can further suppress the injection of charges into the photosensitive layer, and can maintain the electrical characteristics of the photoreceptor under various environments. Examples of inorganic compound fine particles include titanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide. The ratio (C / D) of the total weight C of the binder resin and the inorganic compound particles to the weight D of the solvent in the coating liquid for the undercoat layer is preferably from 1 / 99 to 40 / 60, particularly preferably from 2 / 98 to 30 / 70. The ratio E / F of the weight E of the binder resin to the weight F of the inorganic compound particles is preferably 90 / 10 to 1 / 99, and particularly preferably 70 / 30 to 5 / 95.

[0040] In order to disperse the inorganic compound particles in the coating liquid for the undercoat layer, known devices such as a ball mill, a sand mill, an attritor, a vibration mill, an ultrasonic disperser, and a paint shaker may be used. The coating method for the undercoat layer coating liquid may be appropriately selected from among the most suitable methods taking into consideration the physical properties of the coating liquid and productivity, and examples of the method include spraying, bar coating, roll coating, blade coating, ring coating, and dip coating. Among these, the dip coating method is a method in which a substrate is immersed in a coating tank filled with a coating liquid, and then pulled up at a constant speed or a gradually changing speed to form a layer on the surface of the substrate, and is relatively simple and has excellent productivity and cost, so that it can be suitably used for manufacturing photoreceptors. The apparatus used for the dip coating method may be provided with a coating liquid dispersion device, typically an ultrasonic generator, in order to stabilize the dispersibility of the coating liquid.

[0041] The solvent in the coating film may be removed by natural drying, but the solvent in the coating film may also be removed forcibly by heating. The temperature in such a drying step is not particularly limited as long as it is a temperature at which the solvent used can be removed, but a temperature of about 50 to 140°C is appropriate, and a temperature of about 80 to 130°C is particularly preferable. If the drying temperature is less than 50°C, the drying time may be long and the solvent may not evaporate sufficiently and remain in the photoreceptor layer, while if the drying temperature exceeds about 140°C, the electrical characteristics of the photoreceptor may deteriorate during repeated use, resulting in poor quality of the obtained image. Such temperature conditions are common not only to the formation of the undercoat layer, but also to the formation of layers such as the photosensitive layer, which will be described later, and other treatments.

[0042] The thickness of the undercoat layer is not particularly limited, but is preferably 0.01 to 20 μm, and more preferably 0.05 to 10 μm. If the thickness of the undercoat layer is less than 0.01 μm, it will not function as an undercoat layer, and it may not be possible to cover defects in the conductive support to obtain a uniform surface, and it may not be possible to prevent injection of charges from the conductive support into the photosensitive layer. On the other hand, if the thickness of the undercoat layer is more than 20 μm, it is difficult to form a uniform undercoat layer, and the sensitivity of the photoreceptor may also decrease. When the conductive support is made of aluminum, a layer containing alumite (alumite layer) may be formed as the undercoat layer.

[0043] <Charge generation layer 15> The charge generating layer has a function of generating charges by absorbing light irradiated by, for example, semiconductor laser light in an image forming apparatus, and contains a charge generating substance as a main component and, if necessary, a binder resin and additives.

[0044] The charge generating material can be a compound used in the field, specifically, azo pigments such as monoazo pigments, bisazo pigments and trisazo pigments; indigo pigments such as indigo and thioindigo; perylene pigments such as peryleneimide and perylene acid anhydride; polycyclic quinone pigments such as anthraquinone and pyrenequinone; phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine such as titanyl phthalocyanine; organic photoconductive materials such as squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes; and inorganic photoconductive materials such as selenium and amorphous silicon, and can be appropriately selected and used from those having sensitivity in the exposure wavelength range. These charge generating materials can be used alone or in combination of two or more. Among these charge generating materials, those represented by the following general formula (A):

[0045] [ka]

[0046] (In the formula, X 1 , X 2 , X 3 and X 4 are the same or different and each is a halogen atom, an alkyl group, or an alkoxy group, and r, s, y, and z are the same or different and each is an integer of 0 to 4. It is preferable to use titanyl phthalocyanine represented by the following formula: Titanyl phthalocyanine is a charge-generating material that has high charge generation efficiency and charge injection efficiency in the emission wavelength range (near-infrared light) of currently commonly used laser light and LED light. It generates a large amount of charge by absorbing light and can efficiently inject the generated charge into the charge-transport material without accumulating it inside.

[0047] The titanyl phthalocyanine represented by the general formula (A) can be produced by known production methods such as the method described in Phthalocyanine Compounds by Moser, Frank H. and Arthur L. Thomas, Reinhold Publishing Corp., New York, 1963. For example, among the titanyl phthalocyanine compounds represented by the general formula (A), in the case of an unsubstituted titanyl phthalocyanine in which r, s, y, and z are 0, it can be obtained by synthesizing dichlorotitanyl 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 resultant with a base or water. Alternatively, the titanyl phthalocyanine composition can be produced by reacting isoindoline with a titanium tetraalkoxide such as tetrabutoxytitanium under heating in a suitable solvent such as N-methylpyrrolidone.

[0048] The method for forming the charge generation layer includes a method of vacuum-depositing the charge generation material on the conductive support, and a method of dispersing the charge generation material in a solvent and applying a coating liquid for the charge generation layer onto the conductive support. Among these, a method of dispersing the charge generation material in a binder resin solution obtained by mixing a binder resin in a solvent by a conventionally known method and applying the coating liquid for the charge generation layer onto the conductive support is preferred. This method will be described below.

[0049] The binder resin is not particularly limited, and any resin known in the art can be used. Examples of the binder resin include polyester, polystyrene, polyurethane, phenolic resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate, polyarylate, polyphenoxy, polyvinyl butyral, and polyvinyl formal resins, as well as copolymer resins containing two or more of the repeating units constituting these resins. Examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. These resins can be used alone or in combination of two or more.

[0050] Examples of the solvent include halogenated hydrocarbons such as dichloromethane and dichloroethane, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran (THF) 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. These solvents can be used alone or in combination of two or more.

[0051] The compounding ratio between the charge generating substance and the binder resin is preferably such that the proportion of the charge generating substance is within a range of 10 to 99 mass %. If the ratio of the charge generating material is less than 10% by mass, the sensitivity may decrease. On the other hand, if the ratio of the charge generating material is more than 99% by mass, not only the film strength of the charge generating layer decreases, but also the dispersibility of the charge generating material decreases, the number of coarse particles increases, and the surface charge decreases in areas other than those that should be erased by exposure, resulting in image defects, particularly image fogging called black spots, in which toner adheres to a white background and tiny black spots are formed.

[0052] Before dispersing the charge generating material in the binder resin solution, the charge generating material may be pulverized in advance using a pulverizer such as a ball mill, a sand mill, an attritor, a vibration mill, or an ultrasonic disperser. Examples of dispersing machines used when dispersing the charge generating material in the binder resin solution include a paint shaker, a ball mill, a sand mill, etc. Appropriate dispersion conditions may be selected so as to prevent the incorporation of impurities due to wear of the container and members constituting the dispersing machine. The coating liquid for the charge generating layer may be applied by the same method as the coating liquid for the undercoat layer, and a dip coating method is particularly preferred.

[0053] The thickness of the charge generating layer is not particularly limited, but is preferably 0.05 to 5 μm, and more preferably 0.1 to 1 μm. If the thickness of the charge generating layer is less than 0.05 μm, the efficiency of light absorption decreases, and the sensitivity of the photoconductor may decrease. On the other hand, if the thickness of the charge generating layer is more than 5 μm, the charge transfer inside the charge generating layer becomes the rate-limiting step in the process of erasing the charge on the surface of the photoconductor, and the sensitivity of the photoconductor may decrease.

[0054] <Charge transport layer 16> The charge transport layer has the function of receiving the charges generated by the charge generating substance and transporting them to the surface of the photoreceptor, and contains a charge transport substance, a binder resin, inorganic compound particles, and additives as required.

[0055] As the charge transport material, compounds used in the art can be used. Specific examples thereof include carbazole derivatives, pyrene 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, butadiene derivatives, enamine derivatives, benzidine derivatives, polymers having groups derived from these compounds in the main chain or side chain (poly-N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, poly-9-vinylanthracene, etc.), and polysilanes. These charge transport materials can be used alone or in combination of two or more.

[0056] Among these various charge transport materials, in terms of electrical properties, durability and chemical stability, stilbene derivatives, butadiene derivatives, enamine derivatives and compounds in which a plurality of these compounds are combined are preferred, and stilbene derivatives are more preferred, and are represented by the following general formula (I):

[0057] [ka]

[0058] (In the formula, R 1 , R 2 , R 5 and R 6 are the same or different and each is an alkyl group, an alkoxy group, an aryl group, or an aralkyl group; m, n, p, and q are the same or different and each is an integer of 0 to 3; R 3 and R 4 are the same or different and are a hydrogen atom or an alkyl group. Particularly preferred is a stilbene compound represented by the following formula:

[0059] The substituent R in the general formula (I) 1 , R 2 , R 5 and R 6 This article explains: Examples of the alkyl group include alkyl groups having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl. Examples of the alkoxy group include alkoxy groups having 1 to 6 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, tert-butoxy, n-pentyloxy, and n-hexyloxy. Examples of the aryl group include phenyl, naphthyl, anthryl, phenanthryl, fluorenyl, biphenylyl, and o-terphenyl. Aralkyl groups include, for example, benzyl, phenethyl, benzhydryl, trityl, and the like. Examples of the halogen atom include fluorine, chlorine, bromine, and iodine.

[0060] Substituent R 1 , R 2 , R 5 and R 6 The indices m, n, p and q are the same or different and are integers of 0 to 3, and when the index is 2 or more, each substituent may be different from each other. In addition, the substituent R in the general formula (I) 3 and R 4 Examples of the alkyl group include alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, n-propyl, and isopropyl. The stilbene compound represented by the general formula (I) can be synthesized, for example, by the method described in Japanese Patent No. 3272257.

[0061] Examples of the stilbene compound represented by the general formula (I) include the following compounds (1) to (3), and compound (1) is particularly preferred in terms of printing durability when used in a photosensitive layer.

[0062] [ka]

[0063] A preferred method for forming the charge transport layer is to disperse the charge transport material and inorganic compound particles in a binder resin solution obtained by mixing a binder resin in a solvent by a conventionally known method, and then coat the coating liquid for the charge transport layer on the charge generating layer. This method will be described below.

[0064] The binder resin is not particularly limited, and any resin known in the art can be used, for example, vinyl polymer resins such as polymethyl methacrylate, polystyrene, polyvinyl chloride, and copolymer resins thereof, as well as resins such as polycarbonate, polyester, polyester carbonate, polysulfone, polyphenoxy, epoxy resin, silicone resin, polyarylate, polyphenylene oxide, polyamide, polyether, polyurethane, polyacrylamide, and phenol resin, and thermosetting resins obtained by partially crosslinking these resins, etc. These binder resins can be used alone or in combination of two or more. Among these, polystyrene, polycarbonate, polyarylate and polyphenylene oxide have a volume resistivity of 10 13 It is preferable because it has a hardness of Ω or more, is excellent in electrical insulation, and is also excellent in film-forming properties and potential characteristics, and polycarbonate is particularly preferable.

[0065] The ratio A / B of the charge transport material (A) to the binder resin (B) is preferably from 10 / 12 to 10 / 30. If the ratio A / B is less than 10 / 30 and the ratio of the binder resin is high, when the charge transport layer is formed by dip coating, the viscosity of the coating liquid increases, leading to a decrease in the coating speed and a significant decrease in productivity. In addition, if the amount of solvent in the coating liquid is increased to suppress the increase in the viscosity of the coating liquid, a blushing phenomenon may occur and the formed charge transport layer may become cloudy. On the other hand, if the ratio A / B exceeds 10 / 12 and the ratio of the binder resin is low, the printing durability may be lower than when the ratio of the binder resin is high, and the amount of wear of the photosensitive layer may increase.

[0066] The content of the inorganic compound fine particles is, as described in the section <Content of inorganic compound fine particles>, 7 to 18% by mass in the outermost layer, here the charge transport layer.

[0067] The charge transport layer may contain additives such as a plasticizer or a leveling agent, if necessary, in order to improve film formability, flexibility and surface smoothness. Examples of the plasticizer include dibasic acid esters such as phthalic acid esters, fatty acid esters, phosphate esters, chlorinated paraffin, and epoxy type plasticizers. The leveling agent may be, for example, a silicone-based leveling agent. The charge transport layer may contain fine particles of an inorganic or organic compound in order to increase the mechanical strength and improve the electrical characteristics.

[0068] Examples of the solvent include aromatic hydrocarbons such as benzene, toluene, xylene, and monochlorobenzene, halogenated hydrocarbons such as dichloromethane and dichloroethane, ethers such as THF, dioxane, and dimethoxymethyl ether, and aprotic polar solvents such as N,N-dimethylformamide. If necessary, solvents such as alcohols, acetonitrile, or methyl ethyl ketone can also be added. Among these solvents, non-halogenated organic solvents are preferably used in consideration of the global environment. These solvents can be used alone or in combination of two or more.

[0069] The charge transport layer is formed, for example, in the same manner as in the case of forming the above-mentioned charge generation layer 15, by preparing a coating liquid for the charge transport layer by dissolving or dispersing the charge transport material and binder resin, and, if necessary, the above-mentioned additives, in an appropriate solvent, and applying this coating liquid onto the charge generation layer 15 by a spray method, a bar coating method, a roll coating method, a blade method, a ring method, a dip coating method, or the like. Among these coating methods, the dip coating method is particularly excellent in various respects as described above, and is therefore often used in forming the charge transport layer.

[0070] The thickness of the charge transport layer is not particularly limited, but is preferably 5 to 50 μm, and more preferably 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.

[0071] <Surface protective layer> The surface protective layer has a function of improving the durability of the photoreceptor, and contains a binder resin, inorganic compound fine particles, and additives as necessary. In addition, the surface protective layer may contain one or more of the same charge transport materials as the charge transport layer in order to stabilize the electrical characteristics.

[0072] As the binder resin, a resin having binding properties used in the relevant field can be used, such as polystyrene, polyacetal, polyethylene, polycarbonate, polyarylate, polysulfone, polypropylene, polyvinyl chloride, etc. These binder resins can be used alone or in combination of two or more. Among these, polycarbonate and polyarylate are particularly preferable in consideration of wear characteristics and electrical characteristics.

[0073] The surface protective layer is formed, for example, in the same manner as in the case of forming the charge generating layer 15 and the charge transport layer 16 described above, by preparing a coating liquid for the surface protective layer by dissolving or dispersing a binder resin and inorganic compound fine particles, and, if necessary, the additives described above, in an appropriate solvent, and applying this coating liquid onto the charge transport layer 16 by a spray method, a bar coating method, a roll coating method, a blade method, a ring method, a dip coating method, or the like. Among these coating methods, the dip coating method is particularly excellent in various respects as described above, and is therefore often used in forming the surface protective layer.

[0074] The thickness of the surface protective layer is not particularly limited, but is preferably 0.1 to 10 μm, and more preferably 1.0 to 8.0 μm. Photoconductors that are used repeatedly over a long period of time are designed to be mechanically durable and resistant to wear. However, in actual machines, ozone and NOx gases are generated from the charging members and adhere to the surface of the photoconductor, causing image deletion. In order to prevent this image deletion, the photosensitive layer needs to be worn at a certain rate or higher, and when considering long-term repeated use, it is preferable that the surface protective layer has a thickness of at least 1.0 μm. Furthermore, if the thickness of the surface protective layer exceeds 8.0 μm, problems such as an increase in residual potential and a decrease in fine dot reproducibility may occur.

[0075] (2) Image forming apparatus 100 The image forming apparatus of the present invention is characterized by comprising at least the photoconductor of the present invention, charging means for charging the photoconductor, exposure means for exposing the charged photoconductor to form an electrostatic latent image, developing means for developing the electrostatic latent image formed by exposure to form a toner image (visible image), transfer means for transferring the toner image formed by development onto a recording medium, fixing means for fixing the transferred toner image on the recording medium to form an image, cleaning means for removing and recovering toner remaining on the photoconductor, and discharging means for discharging surface charge remaining on the photoconductor. The image forming apparatus of the present invention and its operation will be described with reference to the drawings, but the present invention is not limited to the following description.

[0076] FIG. 2 is a schematic side view showing the configuration of the image forming apparatus of the present invention. 2 includes the photoreceptor 1 of the present invention, 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).

[0077] Photoconductor 1 is rotatably supported by 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 body of photoconductor 1, thereby driving and rotating photoconductor 1 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 photoconductor 1 from the upstream side to the downstream side in the rotation direction of photoconductor 1 indicated by arrow 41.

[0078] The charger 32 is a charging means for uniformly charging the outer circumferential surface of the photoreceptor 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 according to image information. The light is repeatedly scanned in the direction of extension of the rotation axis 44 of the photoreceptor 1, which is the main scanning direction, and these are focused to sequentially form electrostatic latent images on the surface of the photoreceptor 1. In other words, the charge amount of the photoreceptor 1, which has been uniformly charged by the charger 32, differs depending on whether it is irradiated with the laser beam or not, and an electrostatic latent image is formed.

[0079] The developing device 33 is a developing means that develops the electrostatic latent image formed on the surface of the photoconductor 1 by exposure with a developer (toner), and is provided facing the photoconductor 1. The developing device 33 includes a developing roller 33a that supplies toner to the outer peripheral surface of the photoconductor 1, and a casing 33b that rotatably supports the developing roller 33a about a rotation axis parallel to the rotation axis 44 of the photoconductor 1 and contains a developer including toner in its internal space.

[0080] 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 photoconductor 1 by development, onto a transfer paper 51, which is a recording medium, supplied between the photoconductor 1 and the transfer charger 34 from the direction of the 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.

[0081] The cleaner 36 is a cleaning means for removing and recovering the 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 for removing the toner remaining on the outer peripheral surface of the photoreceptor 1, and a recovery casing 36b for containing the toner removed by the cleaning blade 36a. The cleaner 36 is also provided together with a static elimination lamp (not shown).

[0082] Furthermore, in the image forming apparatus 100, a fixing device 35, which is a fixing means for fixing a transferred image, is provided downstream of the conveyance of the transfer paper 51 that has passed between the photoconductor 1 and the transfer charger 34. The fixing device 35 includes 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 for accommodating the above-mentioned means of the image forming apparatus.

[0083] The image forming operation by this image forming apparatus 100 is carried out as follows. First, when the photoconductor 1 is rotated in the direction of arrow 41 by the driving means, the surface of the photoconductor 1 is uniformly charged to a predetermined positive potential by the charger 32, which is provided upstream of the image-forming point of the light by the exposure means 31 in the rotational direction of the photoconductor 1.

[0084] Next, light according 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 irradiated with light, creating a difference in surface potential between the areas irradiated with light and the areas not irradiated with light, forming an electrostatic latent image. Toner is supplied from a developing device 33, which is provided downstream in the rotational direction of the photoconductor 1 from the imaging point of the light by the exposure means 31, to the surface of the photoconductor 1 on which the electrostatic latent image is formed, thereby developing the electrostatic latent image and forming a toner image.

[0085] In synchronization with the exposure of the photoconductor 1, a transfer paper 51 is supplied between the photoconductor 1 and the transfer charger 34. The transfer charger 34 gives the supplied transfer paper 51 a charge of the opposite polarity to that of the toner, and the toner image formed on the surface of the photoconductor 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 robust image. The transfer paper 51 on which the image has been formed in this way is discharged to the outside of the image forming apparatus 100 by the transport means.

[0086] Meanwhile, the toner remaining on the surface of the photoreceptor 1 after the transfer of the toner image by the transfer charger 34 is peeled off from the surface of the photoreceptor 1 and collected by the cleaner 36. The charge on the surface of the photoreceptor 1 from which the toner has been removed in this manner is removed by light from a discharging lamp, and the electrostatic latent image on the surface of the photoreceptor 1 disappears. The photoreceptor 1 is then rotated again, and the series of operations starting with charging are repeated again to form images continuously. EXAMPLES

[0087] The present invention 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. In addition, the porosity ε of the inorganic compound fine particles used in the examples and comparative examples, the number average primary particle diameter of the inorganic compound fine particles, an indicator of the dispersion state of the inorganic compound fine particles in the outermost surface layer, S Ave The / N, maximum gap area and average size of the inorganic compound fine particles, as well as the surface roughness Rz of the outermost surface layer were measured as follows.

[0088] [Porosity ε of inorganic compound fine particles] Add inorganic compound particles to a measuring cylinder of 250 mL capacity, and measure the weight (g) of the particles and the volume (cm) after leaving the cylinder for 2 minutes. 3 ) to obtain the bulk density rB (g / cm 3 ) and calculate the true density rS (g / cm 3 ) and calculate the porosity ε using the formula: ε = 1-rB / rS.

[0089] [Number average primary particle size of inorganic compound particles] The number average primary particle diameter is measured by observing inorganic compound microparticles under a scanning electron microscope at a magnification of 30,000 to 300,000 times, for example 10,000 times, randomly observing 100 particles as primary particles, and measuring the Feret direction average diameter by image analysis.

[0090] [Inorganic compound fine particles S Ave / N, maximum interstitial area and average size of inorganic particulates] The outermost surface layer of the photoreceptor is peeled off and sliced ​​in the stacking direction to a thickness of 70 nm using an ultramicrotome (Reichert, model: Ultracut N) to create a thin strip of the photosensitive layer (test piece). The resulting test piece is then subjected to a scanning transmission electron microscope (STEM, Hitachi High-Technologies Corporation, model: S-4800) with the observation mode: dark-field image observation and acceleration voltage: 30 kV, and the field of view of the microscope is enlarged to create 50 cross-sectional slices as measurement samples. These are then photographed, and a 5 μm x 5 μm area of ​​the STEM surface observation photograph is analyzed using the image analysis software ImageJ to determine the total surface area of ​​the photosensitive layer. Product S The total area Ssa of inorganic compound particles is calculated for each sample, and the average value S of the 50 samples is calculated. Ave The average value obtained is S Ave and the total solid content (g) of the outermost layer, S Ave Find / N.

[0091] The obtained image file is converted into an 8-bit binary image, and the upper and lower threshold levels are set so that the inorganic compound particle (filler) area on the image is most clearly distinguished and the noise is minimized. Furthermore, in the "Analyze Particle" command, 0.0001 μm is set as the lower limit of the area to be extracted in Size. 2 Enter -infinity, enter MASK in Show, and check "Display results", "Exclude on edges", and "Include holes" before clicking OK. The individual areas of the filler regions identified by binarization will be output as Results. Here, the occupied area Average value S Ave is calculated. In addition, the maximum circle equivalent diameter of the space where no filler exists is calculated from the binarized image, and this is taken as the maximum gap area (μm). 4 The binarized image of the first embodiment is shown in FIG. The magnification of the microscope was adjusted until the particle size of the filler could be measured, and the cross-sectional photograph was analyzed using the image analysis software ImageJ to identify the inorganic fine particles. NextThe particle size of inorganic fine particles can be calculated. The particle size of inorganic fine particles is defined as the distance between two parallel lines drawn at the maximum when the two parallel lines pass through the contact points at both ends of the fine particle. The average size (μm 2 ) is calculated.

[0092] [Surface roughness of the outermost layer Rz] Using a surface roughness measuring device (Tokyo Seimitsu Co., Ltd., model: Surfcom1400D), measure the surface roughness Rz (μm) of the center part with the horizontal direction of the outermost surface layer of the photoconductor as the measurement position, 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.

[0093] Example 1 Titanium oxide (manufactured by Ishihara Sangyo Kaisha, Ltd., product name: Titanium P Three parts by weight of a copolymer polyamide (nylon) (manufactured by Toray Industries, Inc., product name: Amilan (registered trademark), grade: CM8000) were added to 25 parts by weight of methyl alcohol, and the mixture was dispersed for 8 hours using a paint shaker to prepare 3 liters of a coating solution for the undercoat layer. The obtained undercoat layer coating liquid was filled into a coating layer, and an aluminum drum-shaped support having a diameter of 30 mm and a length of 255 mm as the conductive support 11 was immersed in it and then removed. The obtained coating film was allowed to dry naturally, thereby forming an undercoat layer 18 with a thickness of 1 μm on the conductive support 11.

[0094] Titanyl phthalocyanine represented by the following structural formula, which was to be used as a charge generating material, was prepared in advance. [ka]

[0095] 29.2 g of diiminoisoindoline and 200 ml of sulfolane were mixed, and 17.0 g of titanium tetraisopropoxide was added and reacted under a nitrogen atmosphere at 140° C. for 2 hours. The resulting reaction mixture was allowed to cool, and the precipitate was collected by filtration, washed successively with chloroform and a 2% aqueous hydrochloric acid solution, further washed successively with water and methanol, and dried to obtain 25.5 g of blue-purple crystals. As a result of chemical analysis of the obtained compound, it was confirmed that it was titanyl phthalocyanine represented by the above structural formula (yield 88.5%).

[0096] 1 part by weight of the obtained titanyl phthalocyanine and 1 part by weight of butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BM-2) were added to 98 parts by weight of methyl ethyl ketone, and the mixture was dispersed for 2 hours using a paint shaker to prepare 3 liters of a coating solution for the charge generating layer. The obtained coating liquid for the charge generating layer was applied onto the undercoat layer 18 by the same immersion method as in the case of forming the undercoat layer, and the obtained coating film was allowed to dry naturally to form a charge generating layer 15 with a thickness of 0.3 μm.

[0097] Next, silica particles (number average primary particle size 16 nm, bulk density 0.05 g / cm 3 ) were added to a 900 mL glass container. 3 , true density 2.65g / cm 3 , dimethyldichlorosilane surface treatment, Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972) 7g, 25g of compound (1) represented by the following structural formula as a charge transport material, 37.5g of polycarbonate (Teijin Chemical Co., Ltd., product name: TS2050) and 272.5g of tetrahydrofuran were added, mixed, and stirred for 30 hours with a ball mill. The obtained mixture was subjected to 10-pass dispersion treatment using a particle dispersion device (Microfluidics Co., Ltd., model: Microfluidizer M110P) to prepare 319.2g of a coating liquid for a charge transport layer. The obtained coating liquid for a charge transport layer was transferred to a glass container and roll-stirred with a ball mill for 12 hours. After the stirring was completed, the coating liquid for a charge transport layer was left to stand for 3 days under the condition of 20 ° C. to prepare a coating liquid for a charge transport layer.

[0098] [ka]

[0099] The obtained coating liquid for the charge transport layer was applied onto the charge generation layer 15 by the same immersion method as in the case of forming the undercoat layer, and the obtained coating film was dried at 115°C for 1.5 hours to form a charge transport layer 16 with a thickness of 35 μm, thereby obtaining the photoreceptor 1 shown in Figure 1. Compound (1) (stilbene compound) previously prepared according to the method described in Japanese Patent No. 3272257 was used as the charge transport material.

[0100] Example 2 Photoreceptor 1 was produced in the same manner as in Example 1, except that in the preparation of the coating solution for the charge transport layer, the dispersion treatment with the particle dispersing device was changed from 10 passes to 20 passes.

[0101] Example 3 Photoreceptor 1 was produced in the same manner as in Example 1, except that in the preparation of the coating solution for the charge transport layer, the dispersion treatment with the particle dispersing device was changed from 10 passes to 2 passes.

[0102] Example 4 In preparing the coating solution for the charge transport layer, silica particles (number average primary particle size 40 nm, bulk density 0.17 g / cm 3 , true density 2.65g / cm 3 Photoreceptor 1 was produced in the same manner as in Example 1, except that a hexamethyldisilazane surface treatment and AEROSIL (registered trademark) RX50 manufactured by Nippon Aerosil Co., Ltd. were used.

[0103] Example 5 In preparing the coating solution for the charge transport layer, silica particles (number average primary particle size 16 nm, bulk density 0.05 g / cm 3 , true density 2.65g / cm 3 Photoreceptor 1 was produced in the same manner as in Example 1, except that the amount of the photoreceptor (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972) was changed from 7 g to 14 g.

[0104] Example 6 In preparing the coating solution for the charge transport layer, silica particles (number average primary particle size 16 nm, bulk density 0.05 g / cm 3 , true density 2.65g / cm 3 Photoreceptor 1 was produced in the same manner as in Example 1, except that the amount of the photoreceptor (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972) was changed from 7 g to 5 g.

[0105] Example 7 In preparing the coating solution for the charge transport layer, silica particles (number average primary particle size 16 nm, bulk density 0.05 g / cm 3 , true density 2.65g / cm 3 Photoreceptor 1 was produced in the same manner as in Example 1, except that a dimethylpolysiloxane surface treatment, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) RY200S, was used and the photoreceptor 1 was allowed to stand for one day at 25°C before the ball mill stirring treatment.

[0106] Example 8 In preparing the coating solution for the charge transport layer, silica particles (number average primary particle size 16 nm, bulk density 0.05 g / cm 3 , true density 2.65g / cm 3 Photoreceptor 1 was produced in the same manner as in Example 1, except that hexamethyldisilazane (surface treatment, product name: AEROSIL (registered trademark) ADMAFINE NX-130, manufactured by Nippon Aerosil Co., Ltd.) was used.

[0107] Example 9 A photoreceptor 1 was produced in the same manner as in Example 1, except that the undercoat layer 18 was not formed on the conductive support 11 .

[0108] Example 10 In the same manner as in Example 1, an undercoat layer 18 and a charge generating layer 15 were formed on a conductive support 11 . Next, 25 g of compound (1) as a charge transport material, 37.5 g of polycarbonate (manufactured by Teijin Chemical Co., Ltd., product name: TS2040) and 250 g of tetrahydrofuran were added to a 900 mL glass container, mixed, and stirred in a ball mill for 15 hours to prepare 312.5 g of a charge transport coating liquid. The obtained coating liquid for the charge transport layer was applied onto the charge generating layer 15 by the same immersion method as in the case of forming the undercoat layer, and the obtained coating film was dried at 115°C for 1.5 hours to form a charge transport layer with a thickness of 35 μm.

[0109] Next, 25 g of compound (1) as a charge transport material, 37.5 g of polycarbonate (manufactured by Teijin Chemical Co., Ltd., product name: TS2050), 200 g of tetrahydrofuran, and 55.3 g of alumina fine particle slurry (average particle diameter 31 nm, solid content 15%, tetrahydrofuran (THF) solvent, manufactured by CI Chemical Co., Ltd. (now: CIK Nanotech Co., Ltd.)) were added to a 900 mL glass container, mixed, and stirred for 30 hours in a ball mill. The resulting mixture was subjected to 10-pass dispersion treatment using a particle dispersion device (manufactured by Microfluidics Co., Ltd., model: Microfluidizer M110P). surface protection A coating solution for the layer, 317.5 g, was prepared. surface protection The layer coating solution was transferred to a glass container and roll-mixed in a ball mill for 12 hours. After mixing was completed, the mixture was left to stand at 20°C for 3 days. surface protection A layer coating solution was prepared. The obtained coating liquid for the surface protective layer was applied onto the charge transport layer 16 by spray coating, and the obtained coating film was dried at 120°C for 0.5 hours to form a surface protective layer with a thickness of 5 μm, thereby obtaining a photoreceptor having a surface protective layer (not shown) on the outermost surface layer of the photoreceptor 1 shown in Figure 1.

[0110] Example 11 In the same manner as in Example 10, an undercoat layer 18, a charge generating layer 15 and a charge transport layer 16 were formed on a conductive support 11. In a glass container with a capacity of 900 mL, 25 g of compound (1) as a charge transport material, 37.5 g of polycarbonate (manufactured by Teijin Chemicals Ltd., product name: TS2050), 200 g of tetrahydrofuran, and 8.3 g of silica particles (number average primary particle size 16 nm, bulk density 0.05 g / cm 3 , true density 2.65 g / cm 3 , surface-treated with dimethyldichlorosilane, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972) were added, mixed, and stirred in a ball mill for 30 hours. The resulting mixture was subjected to 10 Pass dispersion treatment using a particle dispersion device (manufactured by Microfluidics, model: Microfluidizer M110P) to surface protection prepare 260.3 g of a coating solution for the layer. The resulting surface protection coating solution for the layer was transferred to a glass container and subjected to roll stirring in a ball mill for 12 hours. After the stirring was completed, it was allowed to stand for 3 days under the condition of 20 °C to surface protection prepare a coating solution for the layer. The obtained coating solution for the surface protection layer was applied onto the charge transport layer 16 by spray coating, and the obtained coating film was dried at 120 °C for 0.5 hour to form a surface protection layer with a film thickness of 5 μm, and a photoreceptor having a surface protection layer (not shown) on the outermost surface layer of the photoreceptor 1 shown in Fig. 1 was obtained.

[0111] (Example 12) In the preparation of the coating solution for the charge transport layer, except that silica particles (number average primary particle size 16 nm, bulk density 0.07 g / cm 3 , true density 2.65 g / cm 3 , surface-treated with hexamethyldisilazane, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972V) were used, a photoreceptor 1 was produced in the same manner as in Example 1.

[0112] (Comparative Example 1) In the preparation of the coating solution for the charge transport layer, a photoreceptor 1 was produced in the same manner as in Example 1, except that 10 Pass dispersion treatment by a particle dispersion device was not performed.

[0113] (Comparative Example 2) A photoreceptor was produced in the same manner as in Example 1, except that in the preparation of the coating solution for the charge transport layer, the dispersion treatment with the particle dispersing device was changed from 10 passes to 1 pass.

[0114] Comparative Example 3 In preparing the coating solution for the charge transport layer, silica particles (number average primary particle size 7 nm, bulk density 0.05 g / cm 3 , true density 2.65g / cm 3 Photoreceptor 1 was produced in the same manner as in Example 1, except that a dimethylpolysiloxane surface treatment (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R976) was used.

[0115] Comparative Example 4 In preparing the coating solution for the charge transport layer, silica particles (number average primary particle size: 200 to 400 nm, true density: 2.65 g / cm) were used in the same manner as in Example 8. 3 Photoreceptor 1 was produced in the same manner as in Example 1, except that a high-purity synthetic spherical silica (Admafine SO-E1, product name: high-purity synthetic spherical silica, manufactured by Admatechs Co., Ltd., with no surface treatment) was used, a polypropylene container was used instead of the glass container, and the stirring treatment in the ball mill was changed from 30 hours to 15 hours.

[0116] Comparative Example 5 In preparing the coating solution for the charge transport layer, silica particles (number average primary particle size: 40 nm, bulk density: 0.17 g / cm) were used in the same manner as in Example 4. 3 , true density 2.65g / cm 3 Photoreceptor 1 was produced in the same manner as in Example 1, except that 35 g of a photoreceptor (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) RX50) was used, which was surface-treated with hexamethyldisilazane.

[0117] Comparative Example 6 In preparing the coating solution for the charge transport layer, silica particles (number average primary particle size 16 nm, bulk density 0.05 g / cm 3 , true density 2.65g / cm 3Photoreceptor 1 was produced in the same manner as in Example 1, except that the amount of the photoreceptor (manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972) was changed from 70 g to 150 g.

[0118] [evaluation] The photoreceptors prepared in Examples 1 to 11 and Comparative Examples 1 to 6 were mounted in a unit of a digital copier (manufactured by Sharp Corporation, model: MX-B455W) modified for testing, and 300,000 images were formed to evaluate the initial sensitivity, printing durability, charging stability, and cleaning ability as described below.

[0119] [Initial Sensitivity] The surface potential of the photoconductor in the development area, specifically the surface potential VL (-V) of the photoconductor in the black area when exposed to light to check the sensitivity, was measured, and the initial sensitivity was evaluated based on the following criteria. The measurements were performed by removing the developing unit from a test digital copier and installing a surface potential meter (Trek Japan, Model 344) in the developing area instead.

[0120] <Judgment criteria> A: VL(-V)<80 Can be used without problems in high-speed multifunction machines or printers that require high sensitivity B: 80≦VL(-V)<110 Can be used without problems on low to medium speed multifunction devices or printers C: 110≦VL(-V)<140 If you have a slow, inexpensive multifunction device or printer, the density may be a little low, but it can be used without any problems. D: 140≦VL(-V) Poor sensitivity, low concentration, and problematic for practical use

[0121] [Print durability] Cleaning blades in cleaning devices installed in digital multifunction machines I feel The pressure on the light body, the so-called cleaning blade pressure, is set to 21 gf / cm (2.06 x 10 -1A printing durability test was conducted by printing a character test chart (ISO19752) on 300,000 sheets of recording paper in a normal temperature / humidity environment of 25°C and 50% relative humidity. The thickness of the photosensitive layer at the start of the printing durability test and after 300,000 images were formed was measured using a film thickness measuring device (Filmetrics, Model: F-20-EXR). The amount of scraping per 100,000 revolutions of the photoreceptor drum was calculated from the difference in film thickness between the start of the printing durability test and after 300,000 images were formed, and the printing durability was evaluated based on the following criteria. The greater the amount of scraping, the worse the printing durability was evaluated to be.

[0122] <Judgment criteria> A: Amount of scraping <0.50μm / 100,000 revolutions Can be used without problems in multifunction devices or printers that require a long life B: 0.50μm / 100,000 revolutions ≦ amount of scraping < 0.70μm / 100,000 revolutions Although the amount of wear is somewhat large, it can be used without problems except for multifunction machines or printers that require a long life. C: 0.70μm / 100,000 revolutions ≦ amount of scraping < 0.85μm / 100,000 revolutions Although there is a lot of wear, it can be used without problems with inexpensive multifunction devices or printers. D: 0.85μm / 100,000 revolutions ≦ amount of scraping There is a lot of wear and tear, which is problematic for practical use.

[0123] [Charge stability] The photoconductor (drum) to be evaluated is placed in a test copier, and the process of charging, exposing, and discharging is repeated 600,000 times in a normal temperature / low humidity environment of 25°C / 10% relative humidity. The initial charging potential and the charging potential after fatigue are measured, and the difference between these, ΔV 0 of Using The charge stability was evaluated based on the following criteria, and used as an index of charge reduction in a low humidity environment. <Judgment criteria> A: 0≦ΔV 0 (-V)<60 Very good, can be used without problems even in high-speed multifunction machines or printers that require high sensitivity B: 60≦ΔV 0 (-V)<80 Good, can be used without problems on low to medium speed multifunction devices or printers C:80≦ΔV 0 (-V)<100 Fairly good. If you have a slow, inexpensive multifunction device or printer, the density may be a little low, but it is still usable. D:100≦ΔV 0 (-V) Not good, problems in practical use

[0124] [Cleaning ability] In order to confirm the level of cleaning defects of the photoreceptor after the printing durability test, the photoreceptor after 300,000 images were formed was set in a test digital copier and one 100% density untransferred image was printed on an A4 sheet of paper. Immediately after that, the image forming device was forcibly stopped and the surface of the photoreceptor was visually observed and the cleaning ability (degree of defect) was evaluated based on the following criteria.

[0125] <Judgment criteria> A: No cleaning failures Can be used without problems on multifunction devices or printers that require high image quality B: 1 to 2 cleaning defects Can be used without problems on any multifunction device or printer that does not require high image quality C: 3 to 5 cleaning defects Can be used without problems with inexpensive multifunction devices or printers D: Many cleaning defects Problems in actual use

[0126] <Overall rating> Based on the results of the above evaluations, the photoreceptors were comprehensively evaluated according to the following criteria. A: A rating in all categories, very good Can be used without problems in multifunction machines or printers that require long life and high image quality B: Some items were rated B, but all items were rated B or higher Can be used without problems in any multifunction device or printer that requires long life and high image quality C: Some items were graded C, but all items were graded C or higher Can be used without problems with inexpensive multifunction devices or printers D: Any judgement includes D grade Not for actual use

[0127] The main constituent materials and physical properties of the outermost layer of the prepared photoreceptor are shown in Table 1, and the measurement and evaluation results obtained are shown in Table 2. The symbols for the inorganic compound fine particle materials in Table 1 represent the product names, and the abbreviations for the surface treatment materials represent the following compounds. DMDCS: Dimethyldichlorosilane ·HMDS: Hexamethyldisilazane ·DMPS: Dimethylpolysiloxane

[0128] [Table 1]

[0129] [Table 2]

[0130] The results in Tables 1 and 2 reveal the following: (1) Inorganic compound fine particles having an average primary particle diameter of 10 to 40 nm are dispersed in a charge transport layer at 7 to 18% by mass relative to the total solid content (N), and the average occupation area of ​​the inorganic compound fine particles in a predetermined region of 5 μm × 5 μm in the pre-observation visual field is calculated from a scanning transmission electron microscope image of a cross section of the photosensitive layer of a strip-shaped test piece having a thickness of 70 nm. Ave (%), S Ave The photoconductors (Examples 1 to 11) having a / N of 0.5 or more and 2.0 or less and a maximum gap region having a circle equivalent diameter of 1.0 μm or less are AveCompared to photoreceptors containing silica particles with a / N outside the above range (Comparative Example 1), photoreceptors with a maximum gap region with a circle equivalent diameter outside the above range (Comparative Examples 1, 2, 4, 5), and photoreceptors with an average primary particle diameter outside the above range (Comparative Examples 3 and 4), it is possible to achieve improved printing durability and suppress poor cleaning and uneven shading on the image, compared to photoreceptors with an inorganic compound fine particle content outside the above range relative to the total solid content (Comparative Examples 3 and 4). Average primary particle size of inorganic particles However, by controlling the above range, the particles in the photosensitive layer become finer, the number of particles increases, the interaction between the silica fine particles is large due to the van der Waals forces, and a three-dimensional network structure is formed in which the individual particles form loose interconnections. In a system in which a network structure is not formed, the photosensitive layer and silica fine particles gradually peel off during the wear process, and wear progresses, but the formation of a network structure creates strong interactions between the fine particles, causing the silica filler to detach from the photosensitive layer. Things to do Therefore, the printing durability of the photosensitive layer is improved. Also, the photoreceptors (Examples 10 and 11) in which a surface protective layer was further provided on the charge transport layer were able to obtain the same effects as above.

[0131] (2) The average size of inorganic fine particles is 0.005 μm 2 It was found that the larger photoreceptors (Examples 3, 4, and 7, and Comparative Examples 1, 2, and 4) tended to have poor cleaning properties. 2 By forming this network structure in the photosensitive layer with an average particle size within the above-specified range, the silica fine particles are uniformly distributed on the surface of the photosensitive layer, and the load on the cleaning blade when worn is reduced. (3) It can be seen that the photoconductor using silica filler as inorganic fine particles (Example 11) has inferior printing durability compared to the photoconductor using alumina filler as inorganic fine particles (Example 10), but has extremely good initial sensitivity characteristics. Since the dielectric constant of silica is smaller than that of alumina, damage to sensitivity characteristics is small, and better characteristics can be obtained by using silica filler as inorganic fine particles in a comprehensive characteristic evaluation.

[0132] (4) Silica filler alone in the photosensitive layer Sky In photoreceptors with porosity outside the range of 0.96 to 0.98 (Examples 1, 4, and 12, and Comparative Example 4), the gap regions where silica filler is not present tend to be large, and cleaning properties tend to deteriorate, and it is clear that a void region in the range of 0.96 to 0.98 is preferable. By adopting a silica filler that forms a network structure in the photosensitive layer within the above-mentioned regulation, it is considered that the interaction between fillers works more effectively, and as a result, the printing durability of the photoreceptor is improved. (5) By treating the silica filler in the photosensitive layer with dimethyldichlorosilane or hexamethyldisilazane, the sensitivity of the photosensitive layer is improved compared to photosensitive layers that are not treated with the dimethyldichlorosilane or hexamethyldisilazane treatment (Example 7, Comparative Example 4).

[0133] (6) When comparing the surface roughness Rz of the photoreceptor surface (Examples 1, 5, and 6, and Comparative Example 1), the photoreceptor of Example 1, in which the surface roughness Rz of the surface layer is less than 0.2 to 1.0 μm, tends to have good cleaning properties and printing durability. And, As Rz decreases, the contact area with the blade increases, friction increases, and printing durability tends to deteriorate, but in this photosensitive layer, the interaction between the fine silica particles works effectively within the above specified range, suppressing deterioration of printing durability. On the other hand, when Rz is greater than 1.0, the unevenness of the surface Large In addition, the interaction between the fillers is too strong, resulting in extremely poor printing durability. but As a result, repeated fatigue causes the blade to wear out and break, which can lead to poor cleaning performance. Stable image characteristics cannot be obtained over a long period of time. [Explanation of symbols]

[0134] 1. Electrophotographic photoreceptor 11 Conductive support 14 Photosensitive layer 15 Charge generation layer 16 Charge transport layer 18 Undercoat layer (middle layer) 19 Inorganic compound fine particles

[0135] 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 apparatus (laser printer)

Claims

1. An electrophotographic photoreceptor comprising a photosensitive layer in which at least a charge generating layer and a charge transport layer are laminated in this order on a conductive support, the outermost layer of the electrophotographic photoreceptor contains inorganic compound fine particles, the inorganic compound fine particles have a number average primary particle diameter of 10 to 40 nm and are uniformly dispersed in the outermost surface layer at a ratio of 7 to 18% by mass, The outermost surface layer was sliced ​​in the lamination direction to a thickness of 70 nm, and the obtained rectangular test piece was observed with a scanning transmission electron microscope. The obtained cross-sectional image was converted into an 8-bit binary image, and 50 areas of a 5 μm × 5 μm observation field of the obtained binary image were arbitrarily observed. When the following formula: 0.5≦S Ave / N≦2.0 (In the formula, S Ave is the area S (25 μm 2 ) is the average value of 50 regions of the ratio (%) of the occupied area (%) of the inorganic compound fine particles to the total solid content (g) of the outermost surface layer, and N satisfies the relationship of (a) above, and (b) above, and (c) above, and the maximum gap region when the space where the inorganic compound fine particles are not present is taken as a circle-equivalent diameter is 1.0 μm or less.

1. An electrophotographic photoreceptor comprising:

2. In the region of the observation field of view of 5 μm×5 μm of the binarized image, the inorganic compound fine particles are 2 2. The electrophotographic photoreceptor of claim 1 having an average size of:

3. The inorganic compound fine particles are represented by the following formula: ε=1−rB / rS (wherein rB is the bulk density of the inorganic compound fine particles (g / cm 3 ) and rS is the true density of the inorganic compound fine particles (g / cm 3 ) 3. The electrophotographic photoreceptor according to claim 1, which has a porosity ε of 0.96 to 0.98, as represented by the following formula:

4. 4. The electrophotographic photoreceptor according to claim 1, wherein the outermost layer has a surface roughness Rz of 0.2 to 1.0 μm as defined in JIS-B-0601 (1994).

5. 5. The electrophotographic photoreceptor according to claim 1, wherein the inorganic compound fine particles are silica fine particles.

6. 6. The electrophotographic photoreceptor according to claim 5, wherein the silica fine particles are surface-treated with dimethyldichlorosilane or hexamethyldisilazane.

7. 7. The electrophotographic photoreceptor according to claim 1, wherein the outermost layer is a charge transport layer constituting the photosensitive layer, or a surface protective layer formed on the photosensitive layer.

8. 8. An image forming apparatus comprising at least the electrophotographic photoreceptor according to claim 1, a charging means for charging the electrophotographic photoreceptor, an exposure means for exposing the charged electrophotographic photoreceptor to light to form an electrostatic latent image, a developing means for developing the electrostatic latent image formed by exposure to form a toner image, a transfer means for transferring the toner image formed by development onto a recording medium, a fixing means for fixing the transferred toner image on the recording medium to form an image, a cleaning means for removing and recovering toner remaining on the electrophotographic photoreceptor, and a discharging means for discharging surface charge remaining on the electrophotographic photoreceptor.

Images