Image formation apparatus and process cartridge

Abstract

To improve transfer efficiency and suppress the shape change of a photoreceptor drum surface in a long period of use.SOLUTION: There is provided an image formation apparatus in which the width in the axial direction of multiple stretching rollers of a transfer member is narrower than the width of at least one of the multiple stretching rollers; an attached process cartridge has particles partially exposed from an image carrier; the volume average particle size of the particles is greater than 37 nm but less than 550 nm; 80 number % or greater of the particles contained in the cross section of a surface layer are partially exposed from the surface layer; the total volume of the exposed portion is greater than or equal to 30 volume% but less than or equal to 80 volume% of the total volume of the contained particles; and the width of the surface layer of the image carrier in the axial direction is formed in a region wider than the width of the transfer member.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus and a process cartridge. [Background technology]

[0002] In image forming apparatuses using electrophotography, photosensitive drums that are toner image carriers are widely used that contain organic photoconductive materials that generate electric charges. In recent years, there has been a demand for the mechanical durability of photosensitive drums, i.e., improved wear resistance and maintenance of surface properties, in order to extend the life of the photosensitive drums and improve image quality during repeated use.

[0003] There is an image forming apparatus using an intermediate transfer method as a method for transferring a toner image on a photosensitive drum to a recording material. In an image forming apparatus using the intermediate transfer method, a toner image formed on a photosensitive drum is primarily transferred to an intermediate transfer body, and then the toner image on the intermediate transfer body is secondarily transferred to a recording material. An intermediate transfer belt formed of an endless belt is widely used as the intermediate transfer body. In the primary transfer process, a high-voltage power source is used to create a potential difference between the drum surface and the intermediate transfer belt, and the toner image on the photosensitive drum is generally transferred to the intermediate transfer belt by electrostatic force. Recently, in image forming apparatuses, there is a demand for miniaturization of the device and process cartridge, and an increase in the number of printable sheets, and there is an increasing need for a technology for transferring toner with high efficiency and without waste. As a method for increasing the transfer efficiency, a configuration is considered in which a convex shape is given to the surface of the photosensitive drum, and the contact area with the toner is reduced, thereby reducing the adhesion force.

[0004] Means for imparting a convex shape to the surface of a photosensitive drum have been proposed in the past. Patent Document 1 proposes a configuration for preventing filming of external additives onto the photosensitive drum surface by forming convex shapes with a height of 20 nm or more by adding a filler to the photosensitive drum surface made of a curable resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6361958 Summary of the Invention [Problem to be solved by the invention]

[0006] When a convex shape is formed by adding filler, depending on the amount of filler particles added, particle size, and exposure state, the adhesion to the toner may not decrease, and the transfer efficiency may not improve. Also, the added filler may come off due to friction with the intermediate transfer belt, making it impossible to maintain high transfer efficiency throughout the product life.

[0007] The present invention has been made in view of the above problems, and has an object to simultaneously improve transfer efficiency and suppress change in the shape of the photosensitive drum surface over a long period of use. [Means for solving the problem]

[0008] The present invention employs the following configuration. An image forming apparatus having an endless transfer belt stretched by a plurality of tension rollers and a transfer member disposed on the inner peripheral side of the transfer belt, the image forming apparatus being capable of mounting a process cartridge; The width of the transfer member in the axial direction of the plurality of tension rollers is narrower than the width of at least one of the plurality of tension rollers, the process cartridge has an image carrier having a surface layer for carrying a toner image, the image carrier has particles partially exposed from the surface layer of the image carrier, The particles have a volume average particle size of more than 37 nm and less than 550 nm; 80% by number or more of the particles contained in the surface layer are partially exposed from the surface layer in a cross section of the surface layer, and the total volume of the exposed parts is 30% by volume or more and 80% by volume or less with respect to the total volume of the particles contained, In the axial direction, the width of the surface layer of the image carrier is formed in an area wider than the width of the transfer member. The image forming apparatus is characterized in that: The present invention also employs the following configuration. The present invention is capable of being attached to an image forming apparatus having an endless transfer belt stretched by a plurality of tension rollers and a transfer member disposed on the inner peripheral side of the transfer belt, and in the image forming apparatus, the width of the transfer member in the axial direction of the plurality of tension rollers is narrower than the width of at least one of the plurality of tension rollers; an image carrier having a surface layer that carries a toner image; the image bearing member has particles partially exposed from the surface layer, The particles have a volume average particle size of more than 37 nm and less than 550 nm; 80% by number or more of the particles contained in the surface layer are partially exposed from the surface layer in a cross section of the surface layer, and the total volume of the exposed parts is 30% by volume or more and 80% by volume or less with respect to the total volume of the particles contained, In the axial direction, the width of the surface layer of the image carrier is formed in an area wider than the width of the transfer member. The process cartridge is characterized in that Effect of the Invention

[0009] According to the present invention, it is possible to improve the transfer efficiency while suppressing the change in the surface shape of the photosensitive drum over a long period of use. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus; [Diagram 2] Conceptual diagram of the layer structure in the cross section of a photosensitive drum [Diagram 3] A conceptual diagram explaining the exposed volume of particles on the surface layer of a photosensitive drum. [Figure 4] FIG. 13 is a diagram showing a deformation state at an end of a tension roller of the first image forming apparatus; [Diagram 5] FIG. 13 is a diagram showing a deformation state at the end of the tension roller of the second image forming apparatus; [Figure 6] FIG. 13 is a diagram showing a deformation state at the end of the tension roller of the third image forming apparatus; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, with reference to the drawings, preferred embodiments of the present invention will be described in detail by way of example. However, the dimensions, materials, shapes, and relative positions of the components described in the following embodiments should be appropriately changed depending on the configuration of the device to which the present invention is applied and various conditions. Therefore, unless otherwise specified, the scope of the present invention is not intended to be limited. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined in any manner.

[0012] (Image forming device configuration) 1 is a schematic diagram of an image forming apparatus equipped with a process cartridge of this embodiment, showing a cross section from the front of the image forming apparatus. In the following explanation, the letters YMCK added to the end of the reference numbers indicate the toner color, and matters common to all four colors will be omitted. As the image forming apparatus, a laser beam printer of an electrophotographic process type compatible with legal size paper, capable of forming images at a process speed of 210 mm / s and 600 dpi, was used. .

[0013] The image forming apparatus shown in FIG. 1 is equipped with a detachable process cartridge P. These four process cartridges P have the same structure. The difference is that the process cartridges form images using the toner of the color contained therein, namely, yellow (Y), magenta (M), cyan (C), and black (K). Below, the content common to each color will be given a subscript representing the color and individual explanations will be omitted. For example, when distinguishing between process cartridges of each color, they will be referred to as process cartridge PY, process cartridge PM, process cartridge PC, and process cartridge PK, and when explaining the content common to each color, they will simply be referred to as process cartridge P.

[0014] The process cartridge P has a toner container 23. It also has a photosensitive drum 1, which is an image carrier. It also has a charging roller 2 and a developing roller 3. The photosensitive drum 1 is a cylindrical body having a width (hereinafter referred to as the long side) of 255 mm in the cylindrical axial direction (depth direction in FIG. 1) and a diameter of 24 mm, on which multiple functional layers are formed. The configuration of the photosensitive drum 1 will be described in detail later. The axial direction of the photosensitive drum 1 is the longitudinal direction. This longitudinal direction is the axial direction common to each member such as the photosensitive drum 1, the charging roller 2, the developing roller 3, and the primary transfer roller 6, and multiple tension rollers such as the driving roller 9, the tension roller 10, and the opposing roller 28.

[0015] The charging roller 2 is a rubber roller with a length of 230 mm and a diameter of 8 mm, made by molding conductive rubber onto a plated free-cutting steel shaft. The charging roller 2 is pressed against the photosensitive drum 1 with a predetermined pressure to form a charging nip, and rotates in accordance with the rotation of the photosensitive drum.

[0016] The developing roller 3 is a rubber roller with a longitudinal width of 235 mm and a diameter of 12 mm, made by molding conductive rubber onto a plated free-cutting steel shaft. The developing roller 4 is pressed against the photosensitive drum 1 with a predetermined pressure, forming a developing nip with an intrusion amount of just under 0.1 mm. The developing roller 3 is driven by a driving means (not shown) so that it can rotate at a speed faster than the photosensitive drum.

[0017] A laser unit 7 is disposed below the process cartridge P, and exposes the photosensitive drum 1 based on an image signal. The photosensitive drum 1 is charged to a predetermined negative dark potential (Vd) by applying a predetermined negative voltage to the charging roller 2. The laser unit 7 emits a laser in the image forming section based on the image signal, and the potential drops at the exposed portion of the photosensitive drum 1, forming an electrostatic latent image with a predetermined light potential (Vl). By applying a predetermined negative voltage (Vdc) to the developing roller 4 and providing an appropriate potential difference between the Vd and Vl portions, when the electrostatic latent image passes through the developing nip, the toner on the developing roller 3 is transferred only to the Vl portion, thereby visualizing the electrostatic latent image. The difference between Vdc and Vl is called the development contrast, and this potential difference can control the amount of toner developed from the developing roller 4 to the photosensitive drum 1. The difference between Vd and Vdc is called the back contrast, and this potential difference allows the primary transfer residual toner to be collected from the photosensitive drum 1 to the developing roller 4. In this embodiment, the settings Vd=-550V, Vl=-150V, and Vdc=-350V were adopted, so that the development contrast and back contrast were 200V.

[0018] The toner used in this embodiment is composed of toner particles with an average particle size of 6.4 μm and silica fine particles with an average particle size of 20 nm added thereto, and is negatively charged. The average particle size is the average particle size determined from the particle volume, which can be measured, for example, by the Coulter method.

[0019] The intermediate transfer belt unit is composed of an intermediate transfer belt 8 which is an endless transfer belt, a drive roller 9 as a tension roller, a tension roller 10, and an opposing roller .

[0020] The intermediate transfer belt 8 is an endless belt with a longitudinal width of 250 mm and a circumference of 712 mm, made of two layers of resin material, with a 2 μm-thick resin surface layer coated on a 60 μm-thick base layer. The intermediate transfer belt 8 is stretched around three axes, a drive roller 9 with a diameter of 24 mm, a tension roller 10 with a diameter of 24 mm, and an opposing roller 28 with a diameter of 16 mm, and is stretched with a total tension of 100 N by the tension roller 10.

[0021] The base layer of the intermediate transfer belt 8 is a seamless belt-shaped layer obtained by adding an ionic conductive agent as a conductive agent to polyethylene naphthalate resin (PEN) and polyether ester amide (PEEA) and extruding the resulting material. Although PEN and PEEA resins are used as the material for the base layer, other materials may be used as long as they are thermoplastic resins, such as polyester, polycarbonate, polyarylate, polyether ether ketone (PEEK), acrylonitrile-butadiene-styrene copolymer (ABS), polyphenylene sulfide (PPS), polyvinylidene fluoride (PVdF), and mixtures thereof. An alkali metal salt is used as the ionic conductive material as the conductive agent.

[0022] The surface layer of the intermediate transfer belt 8 is an acrylic resin layer obtained by dip-coating a curable composition, which is prepared by dissolving and dispersing a multifunctional acrylic monomer, a photopolymerization initiator, and conductive metal oxide particles in a solvent, onto a base layer and then irradiating the curable composition with ultraviolet light. Note that other methods may be used to apply the surface layer as long as they can form a uniform film, and spray coating, flow coating, shower coating, roll coating, spin coating, and the like may also be used.

[0023] Inside the intermediate transfer belt 8, i.e., on the inner circumference side of the transfer belt, a primary transfer roller 6 is disposed facing the photosensitive drum 1 as a primary transfer member (transfer member), and a transfer voltage is applied by a voltage application means (not shown). The primary transfer roller 6 is a plated metal shaft made of free-cutting steel with a diameter of 6 mm, and presses the intermediate transfer belt 8 against the photosensitive drum 1 with a contact pressure of 5 N to form a primary transfer nip. In order to stably form the primary transfer nip shape, it is desirable to dispose the primary transfer roller 6 offset downstream in the rotation direction of the intermediate transfer belt with respect to the center position of the photosensitive drum 1. In this configuration, the intermediate transfer belt 8 is stably wrapped around the photosensitive drum 1 with a width of about 0.8 mm by shifting it downstream by about 2 mm.

[0024] The optical sensors 27 are positioned 100 mm on either side of the center of the longitudinal width of the intermediate transfer belt, and are configured to detect a calibration patch, which is a test image, formed on the intermediate transfer belt 8, with the drive roller 9 as the opposing member.

[0025] The toner image formed on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 8 as each photosensitive drum rotates in the direction of the arrow, the intermediate transfer belt 8 rotates in the direction of the arrow Z by an intermediate transfer belt driving means (not shown), and a positive voltage is applied to the primary transfer roller 6. The toner images on the photosensitive drum 1Y are sequentially primarily transferred onto the intermediate transfer belt 8, and are transported to a secondary transfer portion (secondary transfer nip) formed by the secondary transfer roller 11 and the opposing roller 28, which are secondary transfer members, in a state in which the four color toner images are superimposed.

[0026] The feeding and conveying device 12 has a paper feed roller 14 that feeds the recording material K from a paper feed cassette 13 that stores the recording material K, and a conveying roller pair 15 that conveys the fed recording material K. The recording material K conveyed from the feeding and conveying device 12 is conveyed to a secondary transfer section by a registration roller pair 16.

[0027] In order to transfer the toner image from the intermediate transfer belt 8 to the recording material K, the secondary transfer roller 11 is A voltage of positive polarity is applied. This allows the toner image on the intermediate transfer belt 8 to be secondarily transferred to the recording material K being conveyed. The recording material K to which the toner image has been transferred is conveyed to a fixing device 17, where the toner image is fixed to the surface by being heated and pressed by a fixing film 18 and a pressure roller 19. The fixed recording material K is discharged by a pair of discharge rollers 20.

[0028] After the toner image is transferred to the recording material K, the primary transfer residual toner remaining on the surface of the photosensitive drum 1 is electrostatically collected in the development nip. The primary transfer residual toner has a negative polarity, and since the surface potential of the charging roller has a more negative potential than the drum surface potential in the charging nip, it remains on the drum surface. Meanwhile, in the development nip, due to the back contrast between Vd and Vdc, the primary transfer residual toner is transferred from the photosensitive drum 1, which has a high potential, to the developing roller 4, which has a low potential, and is collected. In this embodiment, a so-called cleanerless system is adopted, which does not have a cleaning means for removing the primary transfer residual toner on the photosensitive drum with a blade or the like.

[0029] After the intermediate transfer belt 8 rotates in the direction of the arrow Z, the secondary transfer residual toner is mechanically scraped off by a secondary cleaning blade 21 as a cleaning member and collected in a waste toner collection container 22. The secondary cleaning blade 21 is made of a 3 mm thick zinc-plated steel plate with a 2 mm thick urethane rubber blade with an angle of 77 degrees according to the JIS K 6253 standard attached thereto, and is pressed against the tension roller 10 via the intermediate transfer belt 8 in the counter direction with a linear pressure of 0.49 N / cm and a total pressure of about 11.3 N.

[0030] The control board 25 is a board on which an electric circuit for controlling the image forming apparatus is mounted, and a CPU 26 is mounted as a control unit. The CPU 26 collectively controls the operations of the image forming apparatus, such as the control of an intermediate transfer belt drive motor which is a drive source for the intermediate transfer belt 8 related to the transport of the recording material K, the drive sources (not shown) for the feed / transport device 12, the pair of registration rollers 16, and the fixing device 17, and a drum motor (not shown) which is a drive source for the process cartridge P, the control of various image signals related to image formation, the control of density correction based on the detection result of the optical sensor 27, and further the control related to failure detection.

[0031] (Photosensitive drum) The photosensitive drum 1 of the present invention has a support, a photosensitive layer provided on the support, and a surface layer 32 containing particles. The photosensitive drum 1 of the present invention can be used as a cylindrical photosensitive drum in which the photosensitive layer and the surface layer 32 are formed on a cylindrical support, but it can also be in the form of a belt or sheet.

[0032] The manufacturing method includes a method of preparing a coating liquid for each layer described later, coating the layers in the desired order, and drying the liquid. In this case, the coating liquid can be applied by dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, ring coating, etc. Among these, dip coating is preferred from the viewpoint of efficiency and productivity.

[0033] Each layer will be described below. <Support> In the photosensitive drum 1 of the present invention, the support is preferably a conductive support having electrical conductivity. The shape of the support may be cylindrical, belt-like, sheet-like, or the like. Of these, a cylindrical support is preferable. The surface of the support may be subjected to electrochemical treatment such as anodization, blasting, cutting, or the like. The material of the support is preferably metal, resin, glass, or the like. Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Of these, an aluminum support using aluminum is preferable. Resin or glass may be made conductive by mixing or coating a conductive material.

[0034] <Conductive layer> In the photosensitive drum 1 of the present invention, a conductive layer may be provided on the support. By providing the conductive layer, scratches and irregularities on the support surface can be concealed and light reflection on the support surface can be controlled. The conductive layer preferably contains conductive particles and a resin. Examples of the material of the conductive particles include metal oxides, metals, and carbon black.

[0035] Examples of metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, etc. Examples of metals include aluminum, nickel, iron, nichrome, copper, zinc, silver, etc.

[0036] Among these, it is preferable to use metal oxides as the conductive particles, and it is particularly preferable to use titanium oxide, tin oxide, or zinc oxide.

[0037] When a metal oxide is used as the conductive particles, the surface of the metal oxide may be treated with a silane coupling agent or the like, or the metal oxide may be doped with an element such as phosphorus or aluminum or its oxide. The conductive particles may have a laminated structure in which a pre-coated particle such as titanium oxide, barium sulfate, or zinc oxide is coated with a metal oxide having a different composition from the pre-coated particle. Examples of the coating include metal oxides such as tin oxide. When a metal oxide is used as the conductive particles, the average primary particle size is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

[0038] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, and alkyd resin.

[0039] The conductive layer may further contain a masking agent such as silicone oil, resin particles, and titanium oxide. The average thickness of the conductive layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less. The conductive layer can be formed by preparing a coating liquid for the conductive layer containing the above-mentioned materials and solvent, forming this coating film, and drying it. Examples of the solvent used in the coating liquid include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Examples of the dispersion method for dispersing the conductive particles in the coating liquid for the conductive layer include a method using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

[0040] <Undercoat layer> In the photosensitive drum 1 of the present invention, an undercoat layer may be provided on the support or the conductive layer. The average thickness of the undercoat layer is preferably from 0.1 μm to 50 μm, more preferably from 0.2 μm to 40 μm, and particularly preferably from 0.3 μm to 30 μm.

[0041] Examples of the resin for the undercoat layer include polyacrylic acid resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyethylene oxide resins, polypropylene oxide resins, ethyl cellulose resins, methyl cellulose resins, polyamide resins, polyamic acid resins, polyurethane resins, polyimide resins, polyamideimide resins, polyvinyl phenol resins, melamine resins, phenol resins, epoxy resins, and alkyd resins. In addition, the resin may be a resin having a structure in which a resin having a polymerizable functional group is crosslinked with a monomer having a polymerizable functional group.

[0042] The undercoat layer may contain an inorganic compound or an organic compound in addition to the resin.

[0043] Inorganic compounds include, for example, metals, oxides, and salts. Examples of metals include gold, silver, aluminum, etc. Examples of oxides include zinc oxide, white lead, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, bismuth oxide, indium oxide, tin oxide, zirconium oxide, etc. Examples of salts include barium sulfate and strontium titanate.

[0044] These inorganic compounds may be present in the film in the form of particles. The number-average particle size of the particles is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

[0045] These inorganic compounds may have a laminated structure having core particles and a coating layer that coats the particles.

[0046] The surface of these inorganic compounds may be treated with silicone oil, silane compounds, silane coupling agents, other organic silicon compounds, organic titanium compounds, etc. Furthermore, they may be doped with elements such as tin, phosphorus, aluminum, and niobium.

[0047] Examples of the organic compound include electron transport compounds and conductive polymers. Examples of the conductive polymer include polythiophene, polyaniline, polyacetylene, polyphenylene, and polyethylenedioxythiophene. Examples of the electron transport material include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, aryl halide compounds, silole compounds, and boron-containing compounds. The electron transport material has a polymerizable functional group, and may be crosslinked with a resin having a functional group capable of reacting with the functional group. Examples of the polymerizable functional group include a hydroxyl group, a thiol group, an amino group, a carboxyl group, a vinyl group, an acryloyl group, a methacryloyl group, and an epoxy group. These organic compounds may be present in the film in the form of particles, or may be surface-treated.

[0048] The undercoat layer may contain various additives such as a leveling agent such as silicone oil, a plasticizer, and a thickener. The undercoat layer is obtained by preparing a coating solution for the undercoat layer containing the above-mentioned materials, applying the coating film on a support or a conductive layer, and then drying or curing the coating film. Examples of the solvent used to prepare the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Examples of the dispersion method for dispersing particles in the coating solution include a method using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

[0049] <Photosensitive layer> Photosensitive layers are mainly classified into (1) multi-layer type photosensitive layers and (2) single-layer type photosensitive layers. (1) Multi-layer type photosensitive layers have a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material. (2) Single-layer type photosensitive layers have a photosensitive layer containing both a charge generation material and a charge transport material.

[0050] (1) Laminated photosensitive layer The laminated type photosensitive layer has a charge generating layer and a charge transport layer.

[0051] (1-1) Charge generation layer The charge generating layer preferably contains a charge generating material and a resin. Examples of the charge generating material include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferred. Among phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferred.

[0052] The content of the charge generating material in the charge generating layer is preferably from 40% by mass to 85% by mass, and more preferably from 60% by mass to 80% by mass, based on the total mass of the charge generating layer.

[0053] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, polyvinyl chloride resin, etc. Among these, polyvinyl butyral resin is more preferable.

[0054] The charge generating layer may further contain additives such as an antioxidant and an ultraviolet absorbing agent, etc. Specific examples of such additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0055] The charge generating layer can be formed by preparing a coating solution for the charge generating layer containing the above-mentioned materials and solvent, forming this coating film on the undercoat layer, and drying it. Examples of the solvent used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0056] The thickness of the charge generating layer is preferably from 0.1 μm to 1.5 μm, and more preferably from 0.15 μm to 1.0 μm.

[0057] (1-2) Charge transport layer The charge transport layer preferably contains a charge transport material and a resin.

[0058] Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, resins having groups derived from these materials, etc. Among these, triarylamine compounds and benzidine compounds are preferred, and those having the following structures are preferably used. [ka] (In formula (1), R 1 ~R 10 each independently represents a hydrogen atom or a methyl group.

[0059] Examples of the structure represented by formula (1) are shown in formulas (1-1) to (1-10). Among these, the structures represented by formulas (1-1) to (1-6) are more preferred. [ka]

[0060] The content of the charge transport material in the charge transport layer is preferably from 25% by weight to 70% by weight, and more preferably from 30% by weight to 55% by weight, based on the total weight of the charge transport layer.

[0061] Examples of the resin include polyester resin, polycarbonate resin, acrylic resin, polystyrene resin, etc. Among these, polycarbonate resin and polyester resin are preferable. As the polyester resin, polyarylate resin is particularly preferable.

[0062] The content ratio (mass ratio) of the charge transport material to the resin is preferably from 4:10 to 20:10, and more preferably from 5:10 to 12:10.

[0063] The charge transport layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slipping agents, and abrasion resistance improvers. Specific examples of such additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

[0064] The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing the above-mentioned materials and solvent, forming the coating film on the charge generating layer, and drying it. Examples of the solvent used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents or aromatic hydrocarbon-based solvents are preferred.

[0065] The thickness of the charge transport layer is preferably 3 μm to 50 μm, more preferably 5 μm to 40 μm, and particularly preferably 10 μm to 30 μm. As described later, when the charge transport layer is used as the surface layer 32 of the photosensitive drum 1, the particles forming the convex shape are formed on the surface of the charge transport layer. Usable particle materials, appropriate convex shapes, etc. will be described in detail in the explanation of the surface layer 32.

[0066] (2) Single-layer photosensitive layer The single-layer type photosensitive layer can be formed by preparing a coating solution for the photosensitive layer containing a charge generating material, a charge transporting material, a resin, and a solvent, forming this coating film on the undercoat layer, and drying it. The charge generating material, the charge transporting material, and the resin are the same as the examples of materials in the above "(1) laminated type photosensitive layer". The thickness of the single-layer type photosensitive layer is preferably 10 μm to 45 μm, more preferably 25 μm to 35 μm.

[0067] <Surface layer> The photosensitive drum 1 of the present invention is characterized by having a surface layer 32 containing particles. By setting the convex shape caused by the contained particles within an appropriate range, the adhesive force between the toner and the photosensitive drum 1 can be reduced, and the transfer efficiency can be improved.

[0068] The adhesion force between the toner and the photosensitive drum 1 is roughly divided into electrostatic adhesion force and non-electrostatic adhesion force. The electrostatic adhesion force is largely influenced by the charge amount of the toner, since the main factor is the reflective force. The magnitude of the reflective force is proportional to the charge amount of the toner, and inversely proportional to the square of the distance between the toner and the surface of the photosensitive drum 1 to which the toner is attached. The reflective force can be reduced by forming a convex shape on the surface layer 32 of the photosensitive body and ensuring the distance between the toner and the surface of the photosensitive drum 1. In other words, ensuring the convex height of the convex shape is effective in reducing the reflective force. In other words, it is effective to increase the particle diameter that forms the convex and expose the particles from the surface layer 32.

[0069] On the other hand, in order to reduce the non-electrostatic adhesion force, it is necessary to reduce the van der Waals force. In order to reduce the van der Waals force, it is effective to geometrically reduce the contact area between the toner and the surface of the photosensitive drum 1. In order to reduce the contact area, it is effective to reduce the number of contact points between the toner and the photosensitive drum 1 and to reduce the area at the contact points between the toner and the photosensitive drum 1. In order to reduce the number of contact points, it is effective to form the convex shapes discretely in a range smaller than the toner particle size. In order to reduce the contact area, it is effective to reduce the radius of curvature of the convex shapes. In other words, it is effective to reduce the particle diameter that forms the convexities and form them discretely in a range equal to or smaller than the toner particle size.

[0070] Furthermore, in order to maintain the durability of the convex shape, it is effective to suppress exposure of the particles from the surface layer 32.

[0071] In the photosensitive drum 1, process cartridge, and image forming apparatus using the same of the present invention, by combining an appropriate convex shape with an appropriate image forming apparatus configuration for these elements, the convex shape can be maintained throughout durability, and the effect of improving transfer efficiency can be obtained for a long period of time. The appropriate convex shape and its combination with the image forming apparatus configuration will be described in detail later, and the constituent material of the photosensitive drum front surface layer will be described.

[0072] The surface layer 32 of the photosensitive drum 1 of the present invention contains particles for forming a convex shape as described above. The material of the particles is not particularly limited. Organic resin particles such as acrylic resin particles, inorganic particles such as alumina, silica, and titania, and organic-inorganic hybrid particles can be used.

[0073] Furthermore, in order to improve the charge transport ability of the surface layer 32, conductive particles or a charge transport material may be added to the surface layer coating liquid. As the conductive particles, the conductive pigments used in the conductive layer described above can be used. As the charge transport material, the charge transport material described above can be used. In addition, additives can be added to improve various functions. Examples of additives include conductive particles, antioxidants, ultraviolet absorbers, plasticizers, and leveling agents.

[0074] Examples of the organic resin particles include crosslinked polystyrene particles, crosslinked acrylic resin particles, phenolic resin particles, melamine resin particles, polyethylene particles, polypropylene particles, acrylic resin particles, polytetrafluoroethylene particles, and silicone particles.

[0075] The acrylic resin particles contain a polymer of an acrylic acid ester or a methacrylic acid ester. Among them, styrene-acrylic resin particles are more preferable. There are no particular limitations on the degree of polymerization of the acrylic resin or styrene-acrylic resin, or whether the resin is thermoplastic or thermosetting.

[0076] The polytetrafluoroethylene particles may be particles mainly made of tetrafluoroethylene resin, and may also contain trifluorochloroethylene resin, hexafluoropropylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluorodichloroethylene resin, and the like.

[0077] An example of the organic-inorganic hybrid particles is polymethylsilsesquioxane particles that contain siloxane bonds.

[0078] It is more preferable to use inorganic particles as the particles contained in the surface layer 32 of the photosensitive drum 1 of the present invention, which have low elasticity and are advantageous in terms of point contact with the toner.

[0079] Examples of the inorganic particles include magnesium oxide, zinc oxide, lead oxide, tin oxide, tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, tin oxide, titanium oxide, niobium oxide, molybdenum oxide, vanadium oxide, copper aluminum oxide, tin oxide doped with antimony ions, and hydrotalcite. These particles can be used alone or in combination of two or more kinds. In addition, silica particles are preferable as the inorganic particles.

[0080] As the silica particles, known silica particles can be used, and may be either dry silica particles or wet silica particles. More preferably, wet silica particles obtained by a sol-gel method (hereinafter, also referred to as "sol-gel silica") are preferred.

[0081] The sol-gel silica used for the particles contained in the surface layer 32 of the photosensitive drum 1 of the present invention may have a hydrophilic surface or may have a hydrophobic surface.

[0082] The hydrophobic treatment method includes a method in which the solvent is removed from the silica sol suspension in the sol-gel method, the silica sol suspension is dried, and then the silica sol suspension is treated with a hydrophobic treatment agent, and a method in which the silica sol suspension is directly added with a hydrophobic treatment agent and treated at the same time as drying. From the viewpoint of controlling the half-width of the particle size distribution and the saturated water adsorption amount, the method of directly adding the hydrophobic treatment agent to the silica sol suspension is preferred.

[0083] By subjecting the particles contained in the surface layer 32 of the photosensitive drum 1 of the present invention to hydrophobic treatment, it becomes possible to control the exposed state of the particles in the surface layer 32. Examples of the hydrophobic treatment agent include the following.

[0084] Chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, t-butyldimethylchlorosilane, and vinyltrichlorosilane; Tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltrimethoxysilane, i-butyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, i-butyl alkoxysilanes such as ethyltriethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, and γ-(2-aminoethyl)aminopropylmethyldimethoxysilane; silazanes such as hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexabutyldisilazane, hexapentyldisilazane, hexahexyldisilazane, hexacyclohexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, and dimethyltetravinyldisilazane; Silicone oils such as dimethyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil, alkyl modified silicone oil, chloroalkyl modified silicone oil, chlorophenyl modified silicone oil, fatty acid modified silicone oil, polyether modified silicone oil, alkoxy modified silicone oil, carbinol modified silicone oil, amino modified silicone oil, fluorine modified silicone oil, and terminal reactive silicone oil; Siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, and octamethyltrisiloxane; Fatty acids and their metal salts include long-chain fatty acids such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid, and salts of the above fatty acids with metals such as zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

[0085] Among these, alkoxysilanes, silazanes, and silicone oils are preferably used because they are easy to carry out hydrophobic treatment. These hydrophobic treatment agents may be used alone. Two or more types may be used in combination.

[0086] The Young's modulus of the particles contained in the surface layer 32 of the photosensitive drum 1 of the present invention is preferably 0.60 GPa or more. If the Young's modulus of the particle surface is less than 0.60 GPa, the contact area between the toner surface and the particle surface upon contact with the toner becomes large, which may deteriorate the transferability.

[0087] There are three possible layer configurations for the photosensitive drum to obtain the effects of the present invention, which will be described with reference to Figs. 2(A), 2(B) and 2(C).

[0088] Layer structure 1: A photosensitive drum 1 having a support 105 and a photosensitive layer on the support, the surface layer 32 of the photosensitive drum 1 containing particles 101, the photosensitive layer having a charge generating layer 104 and a charge transport layer 103 on the charge generating layer, the charge transport layer being the surface layer 32. (FIG. 2(A))

[0089] Layer structure 2: A photosensitive drum 1 having a support 205 and a photosensitive layer on the support, the surface layer 32 of the photosensitive drum 1 containing particles 201, the photosensitive layer having a charge generating layer 204 and a charge transport layer 203 on the charge generating layer, the photosensitive drum 1 further having a protective layer 202 on the photosensitive layer, the protective layer being the surface layer 32. (FIG. 2(B))

[0090] Layer structure 3: A photosensitive drum 1 having a support 305 and a photosensitive layer on the support, the surface layer 32 of the photosensitive drum 1 containing particles 301, the photosensitive layer being a single-layer type photosensitive layer 304, the photosensitive drum 1 further having a protective layer 302 on the photosensitive layer, the protective layer being the surface layer 32. (FIG. 2(C))

[0091] In order to achieve both high levels of transferability and durability, the above-mentioned layer structure 1 or layer structure 2 is preferable from the viewpoint of ease of control of the arrangement of particles in the surface layer 32 .

[0092] (Photosensitive drum evaluation method) In the photosensitive drum 1 of the present invention, keeping the convex shape caused by the contained particles within an appropriate range is an important factor for improving transfer efficiency by reducing the adhesive force between the toner and the photosensitive drum 1, and for maintaining performance throughout durability. Therefore, it is necessary to appropriately evaluate and control the particle size of the particles that cause the convex shape, the exposed state in the photosensitive drum state, the uneven state of the exposed particles, the Young's modulus of the exposed particles, etc. Each evaluation method will be described.

[0093] <Method for measuring the volume average particle size> The volume average particle size of the particles is measured using a Zetasizer Nano-ZS (manufactured by MALVERN). This device can measure particle size by dynamic light scattering. First, the sample to be measured is diluted and adjusted so that the solid-liquid ratio is 0.10 mass% (±0.02 mass%), and then collected in a quartz cell and placed in the measurement section. When the sample is inorganic fine particles, water or a methyl ethyl ketone / methanol mixed solvent is used as the dispersion medium, and when the sample is resin particles or toner external additives, water is used. The measurement conditions are as follows: Zetasizer software control In 6.30, enter the refractive index of the sample, the refractive index of the dispersion solvent, the viscosity, and the temperature, and measure. Dn is used as the number average particle size.

[0094] The refractive index of the particles is taken from "Refractive Index of Solids" on page 517 of Volume II of the Fourth Revised Edition of the Basic Chemistry Handbook (edited by the Chemical Society of Japan, Maruzen Co., Ltd.). The refractive index of the resin particles is the refractive index of the resin used in the resin particles that is built into the control software. However, if there is no built-in refractive index, the value listed in the Polymer Database of the National Institute for Materials Science, National Research and Development Agency, is used. The refractive index of external toner additives is calculated by taking the refractive index of inorganic fine particles and The weight average is calculated from the refractive index of the resin used in the resin particles. The refractive index, viscosity, and temperature of the dispersion solvent are selected from the values ​​stored in the control software. In the case of a mixed solvent, the weight average of the dispersion medium to be mixed is calculated.

[0095] <Method for measuring the exposed volume and number of particles from the surface layer> The photosensitive drum 1 of the present invention is cut into 5 mm square samples at 50 mm from each end in the longitudinal direction, three locations in the center, and four locations at 90 degrees each in the circumferential direction, for a total of 12 locations. The photosensitive layer of each sample is coated with platinum for 30 seconds using an evaporator.

[0096] In the FIB-SEM (NVision40, Carl Zeiss), A cut is made for each sample. Beam type: Gallium ion beam Acceleration voltage: 1 kV Size: Length 3μm, width 3μm, depth 3μm Processing step length: 10 nm Number of steps: 300 Furthermore, for each step, SEM observation is performed with an accelerating voltage of 5 kV, a focal length WD of 5 mm, and a field of view of 30,000 times.

[0097] All images captured by the FIB-SEM are converted into three-dimensional images via an interface using image processing and analysis software ("ExfactVR2.1", manufactured by Nihon Visual Science Co., Ltd.). The number of particles exposed from the surface layer 32 of the photosensitive drum 1 is measured from the three-dimensional images, and the ratio of the number of exposed particles to the total number of particles contained in the surface layer 32 is calculated. Furthermore, the derived three-dimensional image is compared with an image of the particles exposed from the surface layer 32 cut by the FIB-SEM, and the cross-sectional image of the particle cut at the center of gravity is analyzed using an image processing and analysis device ("LUZEX AP", manufactured by Nireco Corporation) via an interface. ) and the particles in the cross-sectional image are subjected to binarization processing.

[0098] As shown in the conceptual diagram of FIG. 3, the particle 31 exposed from the surface layer 32 is approximated to a virtual spherical particle with a particle radius R that is one-fourth of the sum of the long axis L and short axis l of the particle when viewed from the surface layer 32. The center of gravity of the cross section of the particle 31 exposed from the surface layer 32 coincides with the center of gravity of the virtual spherical particle. The particle 31 exposed from the surface layer 32 is approximated to a smooth surface with almost no waviness, with the resin portion exposed, for the particle 31, in the calculation. The depth to which the particle 31 contained in the surface layer 32 of the photosensitive drum 1 of the present invention is buried from the resin portion of the surface layer 32 is defined as h.

[0099] In addition, the virtual sphere is approximated to a circle having a particle radius C when the bottom surface of the part exposed from the surface layer 32 of the resin part is viewed from above. (A conceptual diagram is shown in FIG. 3.)

[0100] The volume V1 of the particle is calculated from the formula for the volume of a sphere using the following formula (a). V1=4πR 3 / 3...Equation (a) The volume V2 of the buried part of the particle is calculated from the formula for the volume of a spherical cap using the following formula (b). V2 = πh(3C 2 +h 2 ) / 6...Equation (b) The volume V3 of the exposed part of the particle is calculated by taking the difference between V1 and V2 and using the following formula (c). V3 = V2 - V3 = 4πR 3 / 3―πh(3C 2 +h 2 ) / 6...Equation (c)

[0101] V1, V2, and V3 are calculated for the particles present in the three-dimensional image, and the sum of V3 of all present particles is divided by the sum of V1 of all particles to calculate the volume ratio of the exposed portion of the particle that is partially exposed from the surface layer 32.

[0102] <Method of measuring the coverage rate and coefficient of variation of particles in the surface layer> In the photosensitive drum 1 of the present invention, when the surface layer 32 is viewed from above, if the total area of ​​the exposed portions of the particles is S1, S1 / (S1+S2) can be calculated as follows.

[0103] Regarding the particles in the surface layer 32, a 30,000-fold magnification photograph of the surface layer 32 of the photosensitive drum 1 taken using a scanning electron microscope (SEM) ("S-4800", manufactured by JEOL Ltd.) was captured by a scanner, and the photograph was analyzed using an image processing and analysis device ("LUZEX AP", manufactured by Nireco Corporation). The particles in the photographic image are binarized using a hologram (manufactured by Sigma-Aldrich). The area of ​​the exposed part of the particles on the photosensitive drum 1 in one visual field is defined as S1, and the total area of ​​the particles other than the exposed part is defined as S2, and the coverage rate S1 / (S1+S2) (%) is calculated. The coverage rate is calculated for a total of 10 visual fields, and the average of the obtained coverage rates is regarded as the coverage rate of the particles in the surface layer 32 of the photosensitive body.

[0104] <Method for measuring Young's modulus of exposed particles in surface layer> The evaluation machine used was an SPM probe station (Hitachi High-Tech Science Corporation's "NanoNaviReal") equipped with a scanning probe microscope (Hitachi High-Tech Science Corporation's "S-image") with a built-in heater. Prior to the measurement, the evaluation machine was calibrated under the allowable range of 2.920 ± 0.119 GPa (Young's modulus) using PMMA (polymethyl methacrylate) particles as a standard material. The Young's modulus of PMMA measured with the calibrated evaluation machine was 3.01 GPa.

[0105] The particles in the surface layer 32 were measured by SPM, and the average of 10 measurement results for each particle was taken as the Young's modulus of the particle. Furthermore, the average of the Young's moduli of the 10 particles was taken as the Young's modulus of the particles exposed in the surface layer 32 of the photoreceptor in the present invention.

[0106] <Measurement of thickness of each layer> The thickness of each layer of the photosensitive drum 1, except for the charge generating layer, was determined by a method using an eddy current thickness meter (Fischerscope, manufactured by Fisher Instruments) or a method of converting the specific gravity from the mass per unit area. The thickness of the charge generating layer was measured by converting the concentration value of the photosensitive drum using a calibration curve previously obtained from the concentration value measured by pressing a spectrodensitometer (product name: X-Rite504 / 508, manufactured by X-Rite) against the surface of the photosensitive drum and the thickness measurement value obtained by observing a cross-sectional SEM image.

[0107] [Example] (Photosensitive drum manufacturing) A manufacturing example of the photosensitive drum 1 according to the present invention will be described in detail. Table 1 shows the type, manufacturer, number average particle diameter, volume average particle diameter, and (volume average particle diameter) / (number average particle diameter) of the particles contained in the surface layer 32 of the photosensitive drum 1. Table 1. Details of particles contained in the surface layer [Table 1]

[0108] <Preparation of surface-treated particles 1> Methanol: 10 parts by weight Particle 1 (listed in Table 1): 5 parts by weight The mixture was added and dispersed at room temperature for 30 minutes using a US homogenizer. Next, 0.25 parts by mass of n-propyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.), a reactive surface treatment agent, and 10 parts by mass of toluene were added and stirred at room temperature for 60 minutes. After removing the solvent using an evaporator, the mixture was heated at 140°C for 60 minutes to produce surface-treated particles 1 that were surface-treated with a reactive surface treatment agent. The volume average particle size was 136 nm, and the number average particle size was 124 nm.

[0109] <Production Example of Electrophotographic Photoreceptor 1> [Creating the support] An aluminum cylinder (JIS-A3003, aluminum alloy) having a diameter of 20 mm and a length of 257.5 mm was used as a support (conductive support).

[0110] [Preparation example of conductive layer coating solution 1] Anatase titanium dioxide (Average primary particle size 150nm, niobium content 0.20wt%): 100 parts by mass ·Pure water: 1000 parts by mass The mixture was dispersed in 1 L of water and heated to 60°C.

[0111] A titanium niobate solution prepared by mixing 600 mL of a titanium sulfate solution containing 33.7 parts by mass of Ti with 3 parts by mass of niobium pentachloride (NbCl5) dissolved in 100 mL of 11.4 mol / L hydrochloric acid was added dropwise simultaneously over a period of 3 hours, and a 10.7 mol / L sodium hydroxide solution was added dropwise at the same time so that the pH of the suspension became 2 to 3. After the addition was completed, the suspension was filtered, washed, and dried at 110°C for 8 hours.

[0112] This dried product was subjected to a heat treatment at 800°C for 1 hour in an air atmosphere to obtain a powder of metal oxide particles 1 having a core material containing titanium oxide and a coating layer containing titanium oxide doped with niobium.

[0113] next, Phenolic resin (Product name: Plyofen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g / cm 2 ) :50 parts by mass 1-Methoxy-2-propanol: 35 parts by weight ·Metal oxide particles 1: 75 parts by mass Glass beads (average particle size 1.0 mm): 120 parts by weight The mixture was mixed and placed in a vertical sand mill, and dispersed for 4 hours at a dispersion temperature of 23±3°C and a rotation speed of 1500 rpm (circumferential speed of 5.5 m / s) to obtain metal oxide particle dispersion 1. The glass beads were removed from metal oxide particle dispersion 1 using a mesh, Silicone oil (product name: SH28 PAINT ADDITIVE, manufactured by Toray Dow Corning): 0.01 parts by weight Silicone resin particles (product name: Tospearl 120, manufactured by Momentive Performance Materials, average particle size: 2 μm, density: 1.3 g / cm 2 ) :10 parts by mass The mixture was added and stirred, and pressure filtered using PTFE filter paper (product name: PF060, manufactured by Advantec Toyo) to prepare conductive layer coating solution 1.

[0114] [Example of preparation of conductive layer 1] The conductive layer coating solution 1 was applied onto the support by dip coating, and then heated at 140° C. for 1 hour to form a conductive layer 1 having a thickness of 20 μm.

[0115] [Preparation example of coating solution 1 for undercoat layer] Rutile-type titanium oxide particles (average primary particle size: 50 nm, manufactured by Teika): 100 parts by weight Phenol resin (product name: Plyofen J-325, manufactured by Dainippon Ink and Chemicals, Inc., resin solid content: 60% by mass): 132 parts by mass Toluene: 500 parts by weight Vinyltrimethoxysilane (product name: KBM-1003, manufactured by Shin-Etsu Chemical): 5 parts by mass Glass beads (diameter 0.8 mm): 450 parts by weight The mixture was mixed and stirred for 8 hours, after which the toluene was removed by distillation under reduced pressure, and the mixture was dried at 120° C. for 3 hours to obtain rutile-type titanium oxide particles 1 that had been surface-treated with vinyltrimethoxysilane. Surface-treated rutile titanium dioxide particles: 18 parts by weight N-methoxymethylated nylon (product name: Torezin EF-30T, manufactured by Nagase ChemteX): 4.5 parts by weight Copolymer nylon resin (product name: Amilan CM8000, manufactured by Toray): 1.5 parts by weight Methanol: 90 parts by weight 1-butanol: 60 parts by weight Acetone: 15 parts by weight Glass beads (average particle size 1.0 mm): 120 parts by weight The above was mixed and dispersed in a vertical sand mill for 5 hours to prepare coating solution 1 for undercoat layer.

[0116] [Example of preparation of undercoat layer 1] The undercoat layer coating solution 1 was dip-coated onto the conductive layer 1, and heated at 170° C. for 30 minutes to form an undercoat layer 1 having a thickness of 1.0 μm.

[0117] [Example of preparation of charge generation layer 1] Hydroxygallium phthalocyanine (having peaks at 7.5° and 28.4° in a chart obtained by CuKα characteristic X-ray diffraction): 10 parts by mass Polyvinyl butyral resin (product name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.): 5 parts by weight Cyclohexanone: 200 parts by weight Glass beads: 200 parts by weight The mixture was dispersed in a sand mill for 6 hours. 150 parts by mass of cyclohexanone and 350 parts by mass of ethyl acetate were further added to dilute the mixture, to obtain a coating solution 1 for the charge generating layer. Coating Liquid 1 was dip-coated on Undercoat Layer 1 and dried at 95° C. for 10 minutes to form Charge Generating Layer 1 having a thickness of 0.20 μm.

[0118] [Example of preparation of charge transport layer 1] Next, the following materials were prepared: Charge transport material (hole transport material) represented by the above structural formula (1-1): 5 parts by mass Charge transport material (hole transport material) represented by the above structural formula (1-3): 5 parts by mass Polycarbonate (product name: Iupilon Z400, manufactured by Mitsubishi Engineering Plastics Corporation): 10 parts by weight 0.02 parts of polycarbonate resin having copolymer units of the following structural formula (C-1) and the following structural formula (C-2) (x / y=0.95 / 0.05: viscosity average molecular weight=20,000)

[0119] These were dissolved in a mixed solvent of 60 parts by mass of toluene / 3 parts by mass of methyl benzoate / 15 parts by mass of tetrahydrofuran to prepare a coating solution 1 for a charge transport layer. The coating solution 1 for a charge transport layer was dip-coated onto the charge generating layer 1 to form a coating film, and the coating film was dried at a drying temperature of 40° C. for 5 minutes to form a charge transport layer 1 having a thickness of 15 μm. [ka]

[0120] [Example 1 of preparation of surface layer containing particles] Next, the following materials were prepared: Particle 1 (listed in Table 1): 1.2 parts by weight Siloxane-modified acrylic compound (product name: Simac US270, manufactured by Toagosei Co., Ltd.) :0.1 part by mass Cyclohexane: 30 parts by weight 1-Propanol: 70 parts by weight The above was mixed and stirred to prepare surface layer coating solution 1.

[0121] This surface layer coating liquid was dip-coated on the charge transport layer 1 to form a coating film, and the resulting coating film was dried at 100° C. for 20 minutes to obtain an electrophotographic photoreceptor 1. The film thickness [μm] of the charge transport layer of the electrophotographic photoreceptor 1, the volume average particle size [nm] of the particles contained in the surface layer 32, the number ratio [number %] of the particles exposed from the surface layer 32, the volume ratio [volume %] of the particles exposed from the surface layer 32, the coverage rate S1 / (S1+S2) and the coefficient of variation of the particles exposed from the surface layer, and the Young's modulus [GPa] of the surface of the particles exposed from the surface layer 32 were measured. The results are shown in Table 3.

[0122] <Production Examples of Electrophotographic Photoreceptors 2 to 34> In the manufacturing example of the electrophotographic photoreceptor 1, the temperature at which the coating solution 1 for the charge transport layer is dip-coated on the charge generating layer 1 to form a coating film and then dried, the type and amount of particles contained in the surface layer 32, and the amount of cyclohexane and 1-propanol added are set as shown in Table 2. Except for the above change, electrophotographic photoreceptors 2 to 34 were produced in the same manner as electrophotographic photoreceptor 1. The physical properties measured for electrophotographic photoreceptors 2 to 34 are shown in Table 3.

[0123] Table 2. Details of the formulation for electrophotographic photoreceptors 1 to 34 [Table 2]

[0124] Table 3. Physical properties of electrophotographic photoreceptors 1 to 34 [Table 3]

[0125] <Production Example of Electrophotographic Photoreceptor 35> In the manufacturing example of the electrophotographic photoreceptor 1, the charge transport layer coating liquid 35 is applied onto the charge generation layer 35. The charge transport layer 35 was prepared in the same manner as in the preparation example up to the charge transport layer 1, except that a coating film was formed by dip coating and the coating film was dried at a drying temperature of 120° C. for 5 minutes to prepare a charge transport layer 35 having a thickness of 15 μm.

[0126] [Example 2 of preparation of surface layer containing particles] Next, the following materials were prepared: Particle 1 (listed in Table 1): 1.2 parts by weight Charge transport material (hole transport material) represented by the above structural formula (2-1): 0.1 parts by mass Charge transport material (hole transport material) represented by the above structural formula (3-1): 0.2 parts by mass Siloxane-modified acrylic compound (product name: Simac US270, manufactured by Toagosei Co., Ltd.) :0.1 part by mass Cyclohexane: 30 parts by weight 1-Propanol: 70 parts by weight The above was mixed and stirred to prepare surface layer coating solution 2.

[0127] This surface layer coating solution 2 was dip-coated onto the charge transport layer 1 to form a coating film, and the resulting coating film was dried at 40° C. for 5 minutes.

[0128] Thereafter, under a nitrogen atmosphere, the support (irradiated body) was rotated at a speed of 300 rpm under conditions of an acceleration voltage of 70 kV and a beam current of 5.0 mA, and the coating film was irradiated with an electron beam for 1.6 seconds. The dose at the outermost surface layer position was 15 kGy. Then, under a nitrogen atmosphere, the temperature was raised from 25°C to 100°C over 20 seconds to perform a first heating, and a surface layer 32 having a thickness of 1.0 μm was formed. The oxygen concentration from the electron beam irradiation to the subsequent heat treatment was 10 ppm or less. Next, in the atmosphere, the coating film was naturally cooled until the temperature reached 25°C, and a second heat treatment was performed for 20 minutes under conditions where the temperature of the coating film reached 100°C. In this manner, an electrophotographic photoreceptor 37 was produced. The film thickness [μm] of the charge transport layer of the electrophotographic photoreceptor 37, the film thickness [μm] of the surface layer 32, the volume average particle size [nm] of the particles contained in the surface layer 32, the number ratio [number %] of the particles exposed from the surface layer 32, the volume ratio [volume %] of the particles exposed from the surface layer 32, the coverage S1 / (S1+S2) of the particles exposed from the surface layer 32, and the Young's modulus [GPa] of the surface of the particles exposed from the surface layer 32 were measured. The results are shown in Table 5.

[0129] <Electrophotographic Photoreceptor Manufacturing Examples 36 to 68> Electrophotographic photoreceptors 36 to 68 were produced in the same manner as electrophotographic photoreceptor 35, except that the temperature at which the coating solution 35 for charge transport layer in the preparation example of charge transport layer 35 in the preparation example of charge transport layer 35 was dip-coated onto the charge generation layer 35 to form a coating film and then dried, and the types and amounts of particles contained in surface layer 32 in preparation example 2 of particle-containing surface layer 32, and the amounts of cyclohexane and 1-propanol added were changed as shown in Table 4. The physical properties measured for electrophotographic photoreceptors 36 to 68 are shown in Table 5.

[0130] Table 4. Details of the prescription for electrophotographic photoreceptors 35 to 68 [Table 4]

[0131] Table 5. Physical properties of electrophotographic photoreceptors 35 to 68 [Table 5]

[0132] <Electrophotographic Photoreceptor Manufacturing Examples 69 to 82> Electrophotographic photoreceptors 69 to 82 were produced in the same manner as electrophotographic photoreceptor 1, except that the temperature at which the coating solution 1 for charge transport layer 1 in the preparation example of charge transport layer 1 was dip-coated onto charge generation layer 1 to form a coating film and then dried, the types and amounts of particles contained in surface layer 32, and the amounts of cyclohexane and 1-propanol added were changed as shown in Table 6. The physical properties measured for electrophotographic photoreceptors 69 to 82 are shown in Table 7.

[0133] Table 6. Details of the formulation for electrophotographic photoreceptors 69 to 82 [Table 6]

[0134] Table 7. Physical properties of electrophotographic photoreceptors 69 to 82 [Table 7]

[0135] <Electrophotographic Photoreceptor Manufacturing Examples 83 to 96> Electrophotographic photoreceptors 83 to 96 were produced in the same manner as electrophotographic photoreceptor 35, except that in the production example of electrophotographic photoreceptor 35, the temperature at which coating solution 37 for charge transport layer was dip-coated onto charge generation layer 37 to form a coating film and then dried, and in Production Example 2 of particle-containing surface layer 32, the types and amounts of particles contained in surface layer 32, and the amounts of cyclohexane and 1-propanol added were changed as shown in Table 8. The physical properties measured for electrophotographic photoreceptors 83 to 96 are shown in Table 9.

[0136] <Production Example 97 of Electrophotographic Photoreceptor> Electrophotographic photoreceptor 24 was produced in the same manner as in Production Example 1 of Electrophotographic Photoreceptor 1, except that the drying temperature and drying time in Production Example 1 of Charge Transport Layer 1 were changed to 130° C. and 20 minutes, respectively. The physical properties measured for Electrophotographic Photoreceptor 97 are shown in Table 9.

[0137] <Production Example 98 of Electrophotographic Photoreceptor> An electrophotographic photoreceptor 98 was produced in the same manner as the electrophotographic photoreceptor 35, except that in the production example of the electrophotographic photoreceptor 35, the particles 1 in [Production Example 2 of a Particle-Containing Surface Layer] were not added. The physical properties measured for the electrophotographic photoreceptor 98 are shown in Table 9.

[0138] Table 8. Details of the prescription for electrophotographic photoreceptors 83 to 98 [Table 8]

[0139] Table 9. Physical properties of electrophotographic photoreceptors 83 to 98 [Table 9]

[0140] (Image forming device configuration) In the image forming apparatus shown in FIG. 1, image forming apparatus 1, image forming apparatus 2, and image forming apparatus 3 were prepared, in which the rollers stretching the intermediate transfer belt 8 have different longitudinal widths. Table 10 shows the longitudinal widths of various members and rollers. The image forming apparatus of this embodiment is compatible with legal size paper, and is configured to be capable of forming images up to a paper width of 216 mm, and the longitudinal width of the primary transfer roller 6 is 216 mm or more in all of the image forming apparatuses 1, 2, and 3. Similarly, the opposing roller 28 is also required to perform secondary transfer reliably to the paper width, so the longitudinal width is 216 mm or more in all of the image forming apparatuses 1, 2, and 3. The tension roller 10 is also set to a width close to the intermediate transfer belt width in order to stably apply tension to the entire belt width and stretch it.

[0141] On the other hand, the smaller the width of the drive roller 9 relative to the intermediate transfer belt 8, the more a force will act in the direction to return the belt to its original position when it becomes misaligned in the longitudinal direction, which is advantageous in preventing damage to the belt. Therefore, the drive roller 9 is designed to have the smallest longitudinal width among the three tension rollers.

[0142] In the image forming apparatus 1, the minimum width of the primary transfer roller and the roller that stretches the intermediate transfer belt 8 is The relationship of width is Primary transfer roller width < minimum tension roller width The relationship is as follows.

[0143] In the image forming apparatuses 2 and 3, Primary transfer roller width>minimum tension roller width In the image forming device 2, the minimum width of the tension roller is greater than the image forming width of 216 mm and is equal to the charging roller width. Furthermore, in the image forming device 3, the minimum width of the tension roller is smaller than the image forming width of 216 mm.

[0144] Table 10. Configuration of image forming devices 1 to 3 [Table 10]

[0145] (Evaluation method) The effects of this embodiment were confirmed under the following conditions: In the image forming apparatus shown in Fig. 1, electrophotographic photoreceptors 1 to 98 were attached, and a durability test was conducted in which images were actually formed on a large number of recording materials, and the transfer performance at the beginning and end of the durability test, and the presence or absence of durability problems were confirmed.

[0146] <Transfer performance evaluation method> In an environment with a temperature of 25°C and humidity of 50%, a black image was formed over the entire area of ​​the process cartridge PK, and the residual toner on the photosensitive drum after passing through the primary transfer nip was taped with transparent polyester adhesive tape and obtained. The adhesive tape was attached to a piece of paper, and the measurement was performed with an X-Rite color reflection densitometer (X-rite 500 Series, manufactured by X-rite). The density was measured at 100°C, and the amount of residual toner was quantitatively determined as the density. The density measured when only the adhesive tape was attached to the paper was subtracted to obtain the density corresponding to the pure amount of toner. The density was measured at five equal points in the longitudinal and transverse directions, and the average value was calculated. Based on the density of the residual toner, the transfer performance was ranked according to the following evaluation criteria.

[0147] [Evaluation Criteria] A: Transfer residual density is less than 0.20 B: Transfer residual density is 0.20 or more and less than 0.50 C: Transfer residual density is 0.50 or more and less than 1.0 D: Transfer residual density is 1.0 or more

[0148] <Durability method> In an environment with a temperature of 25°C and humidity of 50%, 2,000 sheets of text images with a print rate of 1% were printed per day for each color process cartridge, and a paper feed durability test was conducted up to 50,000 sheets. For the paper feed durability test, A4 size GF-C081 (manufactured by Canon) was used as the recording material. The paper feed durability test was conducted by combining the configurations of image forming devices 1, 2, and 3 with each photosensitive drum configuration.

[0149] After the durability test, the transfer performance was evaluated in the same manner as in the initial test, and the change in the transfer performance was confirmed. In addition, in order to detect image defects caused by partial damage to the photosensitive drum 1, a black half-tone Toner load: 0.2mg / cm 2 ) was printed out to check the uniformity of the image, the presence or absence of partial defects, etc. Furthermore, a scanning electron microscope (SEM) ("S-4800", manufactured by JEOL Ltd.) was used to observe the surface layer 32 of the photosensitive drum 1 at 30,000 times magnification to check for damage to the partial convex shape and the presence or absence of holes due to detachment of particles.

[0150] [Evaluation Criteria] A: No halftone image defects, no photosensitive drum defects B: No halftone image defects, convex shape change occurs C: No halftone image defects, holes due to particle detachment D: Halftone image defect

[0151] (Evaluation Results) Tables 11 to 14 show the relationship between the evaluation results of the initial transferability, the transferability after durability, and the damage to the photosensitive drum 1 after durability testing of the electrophotographic photosensitive members 1 to 98 in combination with the image forming apparatuses 1 to 3 and the physical properties of the photosensitive drum.

[0152] <Improvement of transfer performance by including particles> In the case of the electrophotographic photoreceptors 97 and 98 which do not contain particles, the transfer residue was ranked D even in the initial stage, whereas in the case of the other electrophotographic photoreceptors, although there were differences in rank depending on the formulation of the photosensitive drum 1 and the physical properties of the obtained surface, the electrophotographic photoreceptors 1 to 68 showed an effect of improving to rank C or higher both in the initial stage and after durability.

[0153] <Improvement of transfer performance due to the effect of volume average particle size> In the electrophotographic photoreceptors 69 and 83 using the large particle size 3 having a volume average particle size of 550 nm, the transfer residue was ranked D even in the initial stage, and the transferability was not improved. In the electrophotographic photoreceptors 70 and 84 using the small particle size particles 4 having a volume average particle size of 37 nm, the transfer residue was ranked D even in the early stages, and the transferability was not improved. In electrophotographic photoreceptors 1 to 68 using particles 1, 2, 5, 6, and surface-treated particles 1, the effect of improving transfer performance was confirmed, and it was confirmed that the range of volume average particle diameter excluding 37 nm or less and 550 nm or more is suitable for improving transfer performance. More preferably, the volume average particle diameter is 50 nm or more and 350 nm or less.

[0154] <Achieving both transfer performance and durability through the volume ratio of exposed particles> In electrophotographic photoreceptors 69, 76, 78, 80, 82, 83, 90, 92, 94, and 96, in which the ratio of the volume of exposed particles to the volume of particles contained in the surface layer 32 was low, below 30 volume %, the transfer residue was ranked D even in the early stages, and the transferability was not improved.

[0155] On the other hand, in electrophotographic photoreceptors 71, 73, 74, 75, 77, 79, 81, 85, 87, 88, 89, 91, 93 and 95, which have a high exposure ratio exceeding 80 volume %, the transferability after durability testing was rated D rank, indicating durability issues.

[0156] Therefore, in this embodiment, it was confirmed that, in the range where the ratio of exposed particles to all particles in the surface layer is 80% by number or more, the range of the ratio of exposed particles to the total particle volume of 30 to 80% by volume is suitable from the standpoint of achieving both improved transferability and durability.

[0157] <Improving transfer performance by particle coverage rate S1 / (S1+S2)> In the electrophotographic photoreceptors 22, 23, 56 and 57 in which the coverage ratio S1 / (S1+S2) of the particles in the surface layer was low, below 0.13, the transfer residue was ranked C even in the initial stage, and the effect of improving the transferability was small.

[0158] On the other hand, even in the electrophotographic photoreceptors 30 and 64 with a high coverage ratio S1 / (S1 + S2) of 0.85, the initial transfer residue was at C rank, and the effect of improving transferability was small.

[0159] Therefore, it was confirmed that the coverage ratio S1 / (S1 + S2) of the particles in the surface layer is more preferably in the range excluding 0.13 or less and 0.85 or more, as shown in the following formula (A). 0.13 < S1 / (S1 + S2) < 0.85 ··· Formula (A) More preferably, it is as shown in the following formula (B). 0.15 ≦ S1 / (S1 + S2) ≦ 0.80 ··· Formula (B)

[0160] <Compatibility between Transfer Performance and Durability by Coefficient of Variation of Coverage Ratio> In the electrophotographic photoreceptors 18, 19, 31, 52, 53, and 65 in which the coefficient of variation of the coverage ratio of the particles contained in the surface layer 32 is high and 27% or more, the transfer residue at the initial stage or after durability is at C rank, and the effect of improving transferability through durability is small. Therefore, it was confirmed that the coefficient of variation of the coverage ratio of the particles contained in the surface layer 32 is more preferably less than 26%.

[0161] <Improvement of Transfer Performance by Young's Modulus of Particle Surface> In the electrophotographic photoreceptors 34 and 68 using the particles 7, the transfer residue was at C rank even at the initial stage, and the effect of improving transferability was small. It is considered that the Young's modulus of the exposed particle surface was 0.5 GPa in both cases, which was lower than that of the electrophotographic photoreceptors of other examples, and the effect of reducing the contact area with the toner was limited. Therefore, it was confirmed that the Young's modulus of the particle surface is more preferably greater than 0.5 GPa.

[0162] <Maintenance of Durability by Image Forming Apparatus Configuration> In the configuration of the image forming apparatus 1, in the electrophotographic photoreceptors 1 to 68, although some convex shape changes were observed, no image defects occurred, and appropriate image quality could be obtained even after durability.

[0163] On the other hand, in electrophotographic photoreceptors 70, 71, 73, 74, 75, 77, 79, 81, 84, 85, 87, 88, 89, 91, 93, and 95, which had a high exposure ratio exceeding 80 volume %, particles were seen to have fallen off after the durability test.

[0164] In addition, although no image defects occurred, convex deformation was observed in electrophotographic photoreceptors 7, 8, 17, 19, 21, 41, 42, 51, 53, and 55, which had a high exposure ratio of 70 volume % or more. It was therefore confirmed that, from the standpoint of image quality after durability testing and damage to the photosensitive drum surface, it is appropriate for the exposed volume ratio to the total particle volume to be 80 volume % or less, more preferably 70 volume % or less.

[0165] In the configuration of image forming apparatus 2, particles were also observed to have detached from electrophotographic photoreceptors 70, 71, 73, 74, 75, 77, 79, 81, 84, 85, 87, 88, 89, 91, 93, and 95, and electrophotographic photoreceptors 7, 8, 17, 19, 21, 41, 42, 51, 53, and 55, which have a high exposed volume ratio.

[0166] The damaged area was the end of the charging roller 2 and the driving roller 9, and was 115 mm from the center in the longitudinal direction, where detachment was noticeable.

[0167] In the configuration of image forming apparatus 3, image defects due to vertical streak-like uneven density occurred in electrophotographic photoreceptors 70, 71, 73, 74, 75, 77, 79, 81, 84, 85, 87, 88, 89, 91, 93, and 95, and electrophotographic photoreceptors 7, 8, 17, 19, 21, 41, 42, 51, 53, and 55, which have a high exposed volume ratio.

[0168] The location where the image defect occurred was 103 mm from the longitudinal center, which corresponds to the end of the drive roller 9, and detachment was also noticeable on the photosensitive drum surface. It is believed that the vertical streak-like density unevenness was caused by a partial decrease in transfer performance due to particle detachment at the position corresponding to the end of the drive roller 9, which led to uneven image density.

[0169] 4, 5, and 6 are conceptual diagrams showing the tension and deformation state of the intermediate transfer belt 8 in (A) image forming apparatus 1, (B) image forming apparatus 2, and (C) image forming apparatus 3, respectively. FIG. 4 shows the state of the image forming apparatus 1, FIG. 5 shows the state of the image forming apparatus 2, and FIG. 6 shows the state of the image forming apparatus 3. FIG. 4(A-1), FIG. 5(B-1), and FIG. 6(C-1) show the tension and deformation state of the intermediate transfer belt 8 with respect to the opposing roller 28 and the driving roller 9, as viewed from the right side of FIG. 1 (from the direction of the arrow LK1). Since the longitudinal width of the intermediate transfer belt 8 is longer than the longitudinal width of each tension roller, the belt is pulled to the left in FIG. 1 by the tension roller 10, and as a result, the belt is tensioned at the end of each tension roller while deforming as shown in FIG. 4(A-1), FIG. 5(B-1), and FIG. 6(C-1). If the intermediate transfer belt 8 is left in this state for a long period of time, the intermediate transfer belt 8 shrinks and develops a curl in a deformed state, resulting in the formation of steps due to the curl.

[0170] Figures 4 (A-2), 5 (B-2), and 6 (C-2) show the state in which the intermediate transfer belt 8 is wrapped around the photosensitive drum 1 at the primary transfer nip, as viewed from the right side of Figure 1 (from the direction of the arrow LK2). In each figure, it can be seen that the relationship in length between the primary transfer roller 6, the photosensitive drum 1, and the charging roller 2 in the longitudinal direction is as shown in Table 10.

[0171] Figures 4 (A-3), 5 (B-3), and 6 (C-3) show enlarged views of the end of the primary transfer roller 6 in Figures 4 (A-2), 5 (B-2), and 6 (C-2), respectively. They also show a cross section of the intermediate transfer belt 8 at the phase where the longitudinal end of the drive roller 9 has a curl formed, when the intermediate transfer belt 8 reaches the primary transfer nip.

[0172] When a printing operation is performed in this state, the intermediate transfer belt 8 passes through the primary transfer nip with a curled shape, as shown in Figures 4 (A-2), 5 (B-2), 6 (C-2), 4 (A-3), 5 (B-3), and 6 (C-3). Although the step caused by the curl is eliminated as the printing operation continues, it takes time for the step to disappear, so the intermediate transfer belt passes through the primary transfer nip repeatedly.

[0173] In the configurations of the image forming apparatuses 2 and 3 shown in Fig. 5 (B-2), Fig. 6 (C-2), Fig. 5 (B-3), and Fig. 6 (C-3), the step of the curl caused by the driving roller 9 exists inside the longitudinal width of the primary transfer roller 6. Therefore, when passing through the primary transfer nip, the step of the curl strongly rubs against the surface of the photosensitive drum 1. It is considered that the repeated rubbing over the life of the device led to the detachment of particles from the surface layer and the occurrence of vertical streaky density unevenness.

[0174] On the other hand, in the configuration of the image forming apparatus 1 shown in Figures 4(A-2) and 4(A-3), the curl step is located outside the primary transfer roller 6, so that the curl step does not rub against the surface of the photosensitive drum 1 when passing through the primary transfer nip.

[0175] From the above, it has been confirmed that a configuration in which the width of the transfer member is shorter than the width of the tension roller is suitable for an image forming apparatus that can be combined with a process cartridge using a photosensitive drum 1 containing particles in its surface layer.

[0176] The width of the transfer member is narrower than the width of at least one of the tension rollers (drive roller 9, tension roller 10, opposing roller 28, etc.). The effects of the present invention can be obtained if the image forming apparatus 2 is configured as shown in FIG. 5, for example, the width of the transfer roller 6 is narrower than that of the opposing roller 28, but wider than that of the drive roller 9. Even with this configuration, as shown in Table 11, for example, an image with fewer image defects is obtained compared to the case where the image forming apparatus 3 shown in FIG. 6 is used (Examples 7, 8, 17, 19, and 21). This is believed to be because the image forming apparatus 2 satisfies the relationship of image formation width<drive roller 9. can be done.

[0177] 4, the width of the transfer member is narrower than both the drive roller 9 and the counter roller 28. With this configuration, more preferable effects can be obtained as shown in Table 11 (Examples 7, 8, 17, 19, and 21).

[0178] 1, a so-called drum cleanerless system that does not have a cleaning means for the primary transfer residual toner is used in this embodiment, but a cleaning means for the primary transfer residual toner may be provided. For example, the effect of the present invention can be obtained even with a so-called blade cleaning system in which a rubber blade is brought into contact with the photosensitive drum 1 to collect the primary transfer residual toner.

[0179] Also, in this embodiment, a configuration in which a metal shaft is used as the primary transfer member has been shown, but similar effects can be obtained using other members as long as the primary transfer nip is formed by contacting the intermediate transfer belt 8 with the photosensitive drum 1. Specifically, the effects of the present invention can be obtained even in a configuration in which the intermediate transfer belt 8 is pushed up and brought into contact with the photosensitive drum 1 using a rubber roller, a resin roller, a fiber brush, a pad, or the like as the primary transfer member.

[0180] In this embodiment, only the layer structure using the laminated type photosensitive layer shown in Figure 2 (A) and Figure 2 (B) was described. As mentioned above, in the layer structure using the single-layer type photosensitive layer shown in Figure 2 (C), it is difficult to control the particle arrangement, but if it is controlled within the range specified in the present invention, the same effect can be obtained even with the single-layer type photosensitive layer.

[0181] Tables 11 to 14: Evaluation results of image forming apparatus using photosensitive drum 1 [Table 11] [Table 12] [Table 13] [Table 14]

[0182] [Configuration 1] An image forming apparatus having an endless transfer belt stretched by a plurality of stretching rollers and a transfer member disposed on the inner circumferential side of the transfer belt, wherein a process cartridge can be attached, the width of the transfer member in the axial direction of the plurality of stretching rollers is narrower than the width of at least one of the plurality of stretching rollers, the process cartridge has an image carrier having a surface layer that carries a toner image, the image carrier has particles partially exposed from the surface layer of the image carrier, the volume average particle diameter of the particles exceeds 37 nm and is less than 550 nm, in the cross section of the surface layer, 80% or more of the number of particles contained are partially exposed from the surface layer, and the total volume of the exposed portions is 30% or more and 80% or less of the total volume of the contained particles, in the axial direction, the width of the surface layer of the image carrier is formed in a region wider than the width of the transfer member An image forming apparatus characterized by the above. [Configuration 2] the volume average particle diameter of the particles is 50 nm or more and 350 nm or less The image forming apparatus according to claim 1, characterized by the above. [Configuration 3] When the process cartridge views the surface layer from above, when the total area of the exposed portions of the particles partially exposed from the surface layer is S1 and the total area of the portions other than the exposed portions of the particles partially exposed from the surface layer is S2, S1 / (S1 + S2) satisfies the following formula (A) The image forming apparatus according to claim 1 or 2, characterized by the above. 0.13 < S1 / (S1 + S2) < 0.85 ··· Formula (A) [Configuration 4] S1 / (S1 + S2) satisfies the following formula (B) The image forming apparatus according to claim 3, characterized by the above. 0.15 ≦ S1 / (S1 + S2) ≦ 0.80 ··· Formula (B) [Configuration 5] In the process cartridge, when the surface layer is viewed from above, a coefficient of variation of S1 / (S1+S2) is less than 26%, where S1 is the total area of ​​the exposed portions of the particles and S2 is the total area of ​​the portions other than the exposed portions of the particles. 5. The image forming apparatus according to claim 3, wherein the first and second electrodes are arranged in a first direction. [Configuration 6] In the process cartridge, the particles have a Young's modulus of 0.60 GPa or more. 6. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. [Claim 7] The width of the transfer member in the axial direction of the plurality of tension rollers is narrower than the width of any of the tension rollers included in the plurality of tension rollers. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Configuration 8] The width of the transfer belt is wider than the width of the tension rollers. 8. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. [Configuration 9] The image forming width of the transfer belt is narrower than the width of a drive roller included in the plurality of tension rollers in the axial direction of the plurality of tension rollers. 9. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus. [Configuration 10] The present invention is capable of being attached to an image forming apparatus that is arranged on the inner circumferential side of an endless transfer belt that is tensioned by a plurality of tension rollers, and in the image forming apparatus, a width of the transfer member in an axial direction of the plurality of tension rollers is narrower than a width of at least one of the plurality of tension rollers; an image carrier having a surface layer that carries a toner image; the image bearing member has particles partially exposed from the surface layer, The particles have a volume average particle size of more than 37 nm and less than 550 nm; In the cross-section of the surface layer, 80% or more of the number of particles contained are partially exposed from the surface layer, and the total volume of the exposed portions is 30% by volume or more and 80% by volume or less with respect to the total volume of the contained particles. In the axial direction, the width of the surface layer of the image carrier is formed in a region wider than the width of the transfer member. A process cartridge characterized by the above. [Configuration 11] The volume average particle diameter of the particles is 50 nm or more and 350 nm or less. The process cartridge according to claim 10, characterized by the above. [Configuration 12] When the surface layer of the image carrier is viewed from above, let the total area of the exposed portions of the particles partially exposed from the surface layer be S1, and the total area of the portions other than the exposed portions of the particles partially exposed from the surface layer be S2. Then, S1 / (S1 + S2) satisfies the following formula (A). When the total area of the exposed portions of the particles partially exposed from the surface layer is S1, and the total area of the portions other than the exposed portions of the particles partially exposed from the surface layer is S2, S1 / (S1 + S2) satisfies the following formula (A). The process cartridge according to claim 10 or 11, characterized by the above. 0.13 < S1 / (S1 + S2) < 0.85 ··· Formula (A) [Configuration 13] S1 / (S1 + S2) satisfies the following formula (B). The process cartridge according to claim 12, characterized by the above. 0.15 ≤ S1 / (S1 + S2) ≤ 0.80 ··· Formula (B) [Configuration 14] When the surface layer of the image carrier is viewed from above, when the total area of the exposed portions of the particles is S1 and the total area of the portions other than the exposed portions of the particles is S2, the coefficient of variation of S1 / (S1 + S2) is less than 26%. The process cartridge according to claim 12 or 13, characterized by the above. [Configuration 15] The Young's modulus of the particles of the image carrier is 0.60 GPa or more. The process cartridge according to any one of claims 10 to 14, characterized by the above. [Configuration 16] 16. An image forming apparatus in which the process cartridge according to claim 10 can be attached, wherein a width of the transfer member in an axial direction of the plurality of tension rollers is narrower than a width of any of the tension rollers included in the plurality of tension rollers. 1. An image forming apparatus comprising: [Configuration 17] 17. An image forming apparatus in which the process cartridge according to claim 10 can be installed, wherein the width of the transfer belt is wider than the width of the tension rollers. 1. An image forming apparatus comprising: [Configuration 18] 11. An image forming apparatus in which the process cartridge according to claim 10 can be installed, wherein an image forming width of the transfer belt is narrower than a width of a drive roller included in the plurality of tension rollers in an axial direction of the plurality of tension rollers. 1. An image forming apparatus comprising: [Explanation of symbols]

[0183] 1: photosensitive drum, 6: primary transfer roller, 8: intermediate transfer belt, 9: drive roller, 10: tension roller, 28: opposing roller, 31: particles exposed from the surface layer, P: process cartridge, 101, 201, 301: particles, 103,

Claims

1. An image forming apparatus having an endless transfer belt stretched by a plurality of tension rollers and a transfer member disposed on the inner circumferential side of the transfer belt, wherein a process cartridge can be attached; a width of the transfer member in the axial direction of the plurality of tension rollers is narrower than a width of at least one of the plurality of tension rollers; the process cartridge has an image carrier having a surface layer that carries a toner image, the image bearing member has particles having exposed portions that are partially exposed from the surface layer of the image bearing member, The particles have a volume average particle size of more than 37 nm and less than 550 nm; 80% by number or more of the particles contained in the surface layer are partially exposed from the surface layer in a cross section thereof, and the total volume of the exposed portions is 30% by volume or more and 80% by volume or less of the total volume of the particles contained; 10. An image forming apparatus according to claim 9, wherein the width of the surface layer of the image carrier is greater than the width of the transfer member in the axial direction.

2. The particles have a volume average particle size of 50 nm or more and 350 nm or less.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. In the process cartridge, when the surface layer is viewed from above, S1 is the total area of ​​the exposed portions of the particles partially exposed from the surface layer, and S2 is the total area of ​​the portions of the surface layer other than the exposed portions of the particles, and S1 / (S1+S2) satisfies the following formula (A):

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium. 0.13<S1 / (S1+S2)<0.85...Formula (A)

4. S1 / (S1+S2) satisfies the following formula (B):

4. The image forming apparatus according to claim 3, wherein the image forming apparatus is a recording medium. 0.15≦S1 / (S1+S2)≦0.80...Formula (B)

5. When the surface layer of the process cartridge is viewed from above, the total area of ​​the exposed part of the particles is S1, and the total area of ​​the other parts of the particles is S2, where S1 / ( The coefficient of variation of (S1 + S2) is less than 26% 4. The image forming apparatus according to claim 3, wherein the image forming apparatus is a recording medium.

6. In the process cartridge, the particles have a Young's modulus of 0.60 GPa or more.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

7. The width of the transfer member in the axial direction of the plurality of tension rollers is narrower than the width of any of the tension rollers included in the plurality of tension rollers.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

8. The width of the transfer belt is wider than the width of the plurality of tension rollers.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

9. The image forming width of the transfer belt is narrower than the width of a drive roller included in the plurality of tension rollers in the axial direction of the plurality of tension rollers.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

10. The image forming apparatus can be attached to an image forming apparatus having an endless transfer belt stretched by a plurality of tension rollers and a transfer member disposed on the inner circumferential side of the transfer belt, and in the image forming apparatus, the width of the transfer member in the axial direction of the plurality of tension rollers is narrower than the width of at least one of the plurality of tension rollers, an image carrier having a surface layer that carries a toner image; the image bearing member has particles having exposed portions that are partially exposed from the surface layer, The particles have a volume average particle size of more than 37 nm and less than 550 nm; 80% by number or more of the particles contained in the surface layer are partially exposed from the surface layer in a cross section thereof, and the total volume of the exposed portions is 30% by volume or more and 80% by volume or less of the total volume of the particles contained; In the axial direction, the width of the surface layer of the image carrier is formed in an area wider than the width of the transfer member. A process cartridge characterized by:

11. The particles have a volume average particle size of 50 nm or more and 350 nm or less.

11. The process cartridge according to claim 10.

12. When the surface layer of the image bearing member is viewed from above, S1 is the total area of ​​the exposed portions of the particles that are partially exposed from the surface layer, and S2 is the total area of ​​the particles other than the exposed portions that are partially exposed from the surface layer, and S1 / (S1+S2) satisfies the following formula (A):

11. The process cartridge according to claim 10. 0.13<S1 / (S1+S2)<0.85...Formula (A)

13. S1 / (S1+S2) satisfies the following formula (B):

13. The process cartridge according to claim 12. 0.15≦S1 / (S1+S2)≦0.80...Formula (B)

14. When the surface layer of the image bearing member is viewed from above, the coefficient of variation of S1 / (S1+S2) is less than 26%, where S1 is the total area of ​​the exposed portions of the particles and S2 is the total area of ​​the particles other than the exposed portions.

13. The process cartridge according to claim 12.

15. The particles of the image bearing member have a Young's modulus of 0.60 GPa or more.

11. The process cartridge according to claim 10.

16. 11. An image forming apparatus to which the process cartridge according to claim 10 can be attached, wherein the width of the transfer member in the axial direction of the plurality of tension rollers is narrower than the width of any of the tension rollers included in the plurality of tension rollers. An image forming apparatus characterized by:

17. 11. An image forming apparatus to which the process cartridge according to claim 10 can be attached, wherein the width of the transfer belt is wider than the width of the plurality of tension rollers. An image forming apparatus characterized by:

18. 11. An image forming apparatus to which the process cartridge according to claim 10 can be attached, wherein an image forming width of the transfer belt is narrower than a width of a drive roller included in the plurality of tension rollers in an axial direction of the plurality of tension rollers. An image forming apparatus characterized by:

Images