Electrophotographic photoreceptor, process cartridge, and electrophotographic apparatus

Abstract

To provide an electrophotographic photoreceptor that can achieve both an improvement in image quality of a halftone image and an improvement in transfer property by preventing scattering of light on a surface layer of the electrophotographic photoreceptor.SOLUTION: An electrophotographic photoreceptor has a support and a photosensitive layer on the support. A surface layer of the electrophotographic photoreceptor contains particles. The surface layer has particles that are partially exposed from the surface layer among the particles contained in the surface layer. The volume average particle diameter of the particles is 50.0 nm or more and 350.0 nm or less. In a cross section of the surface layer, the number of the particles partially exposed from the surface layer is 80 number% or more based on the total number of the particles contained in the surface layer. The sum of the volume of exposed parts of the particles partially exposed from the surface layer is 30 volume% or more and 80 volume% or less based on the total volume of the particles contained in the surface layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrophotographic photoreceptor, a process cartridge having the electrophotographic photoreceptor, and an electrophotographic apparatus. [Background technology]

[0002] In recent years, in the field of electrophotographic devices such as photocopiers and printers, there has been a demand for high-speed printing to increase productivity. To achieve high speed in electrophotographic devices, the electrophotographic process, which involves repeated charging, exposure, development, and transfer steps, requires that the latent image created in the exposure step is developed into toner in the development step, and that the toner is efficiently transferred to a medium such as paper or an intermediate transfer medium. Furthermore, from the perspective of making effective use of space in offices, there is a demand for compact electrophotographic devices that eliminate the cleaning step by streamlining the transfer process.

[0003] In the transfer process, a predetermined bias is applied to the toner in order to transfer the latent image on the photoreceptor to the developed toner onto the medium. By adding an external additive to the toner and forming a specific shape on the surface of the photoreceptor, the adhesion between the toner and the photoreceptor surface is reduced, thereby reducing the applied bias. This not only eliminates the need for a high-voltage power supply to apply a high bias within the electrophotographic device, but also suppresses toner splatter caused by high transfer bias, thereby improving image quality. As one method of reducing the adhesion of toner to the surface of the photoreceptor by forming a specific shape on the surface of the photoreceptor, it has been conventionally proposed to incorporate particles into the surface of the electrophotographic photoreceptor to form a convex shape, thereby creating point contact between the toner and the surface of the photoreceptor.

[0004] Patent Document 1 discloses an electrophotographic photoreceptor having a convex structure on the surface of its outermost layer, which is composed of a polymerizable monomer and an inorganic filler polymerized cured product, with the aim of improving cleaning performance and reducing wear on the photoreceptor and cleaning blade, regardless of the amount of lubricant supplied.

[0005] Patent Document 2 discloses an electrophotographic photoreceptor having a surface layer formed by curing a coating film containing at least one of acrylic resin particles and melamine resin particles, and a hole-transporting compound having polymerizable functional groups, for the purpose of making the surface of the photoreceptor wear-resistant and highly lubricated.

[0006] Patent Document 3 discloses an electrophotographic photoreceptor containing a curable resin and polytetrafluoroethylene particles, the surface of which has an uneven surface formed by mechanical polishing, with the aim of reducing image unevenness caused by uneven gloss of the support while maintaining wear resistance.

[0007] Patent Document 4 discloses an electrophotographic photoreceptor containing enclosed spherical particles surrounded by pores in a matrix component, with the aim of improving the lubricity and cleanability of the photoreceptor surface.

[0008] Patent Document 5 discloses an electrophotographic photoreceptor in which, for the purpose of maintaining a mold release effect, independent concave portions with a depth of 0.1 μm to 10 μm are formed on the surface of the surface layer of the photoreceptor, and a mold release material is contained within the concave portions. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2020-71423 [Patent Document 2] Japanese Patent Publication No. 2019-45862 [Patent Document 3] Japanese Patent Publication No. 2016-118628 [Patent Document 4] Japanese Patent Publication No. 2013-029812 [Patent Document 5] Japanese Patent Publication No. 2009-14915 [Overview of the project] [Problems that the invention aims to solve]

[0010] In recent years, electrophotographic devices have been required to achieve both high image quality at high output speeds and efficient transfer processes to reduce waste toner due to environmental considerations. However, Patent Documents 1-3 have shown that although the adhesion between the toner and the photoreceptor surface is reduced to some extent and the transferability of the toner is improved, the layering of fine particles contained in the surface layer causes the laser to scatter when the photoreceptor is exposed, making it impossible to maintain the uniformity of the halftone image. Furthermore, Patent Document 4 has shown that when there is a difference in peripheral speed between the photoreceptor and the intermediate transfer medium or medium during the transfer process, the enclosed spherical particles move, increasing the contact area between the toner and the surface of the photoreceptor and reducing the transferability. In addition, Patent Document 5 has shown that multiple release materials are contained within the concave portion, making it difficult to maintain point contact between the toner and the surface of the photoreceptor and thus making it difficult to maintain good transferability over the long term.

[0011] The object of the present invention is to provide a photoreceptor that achieves both improved image quality and improved transferability of halftone images by suppressing light scattering in the surface layer of the photoreceptor. [Means for solving the problem]

[0012] The above objectives are achieved by the present invention as described below. That is, the electrophotographic photoreceptor according to the present invention is a support, Applicable on support of photosensitive layer and protective layer on the photosensitive layer to have The photosensitive layer has a charge generating layer and a charge transport layer on the charge generating layer, and the protective layer is a cured film formed by polymerizing a composition containing a monomer having a polymerizable functional group. An electrophotographic photoreceptor, The protective layer is the surface layer of the electrophotographic photoreceptor, Applicable table Surface layer 、 Contains particles, The surface layer has particles contained in the surface layer that are partially exposed from the surface layer. The volume-average particle size of the particle is 7 0.0nm or more 2 It is less than 50.0 nm, The Young's modulus of the particle is 0.60 GPa or higher. In the cross-section of the surface layer, from the surface layer Department The number of partially exposed particles is 80% or more of the total number of particles present in the surface layer, Contains and from the surface layer Department the total volume of the exposed portions of the partially exposed particles is 30% or more and Contains 30% or less by volume of the total volume of the particles present in the surface layer 75 by volume. the law of nature, When the surface layer is viewed from above, let S1 be the total area of ​​the partially exposed parts of the particles, and S2 be the total area of ​​the parts of the surface layer other than the partially exposed parts of the particles. Then, S1 / (S1+S2) satisfies the following equation (A). 0.15≦S1 / (S1+S2)≦0.80...Formula (A) When the surface layer is viewed from above, the shape factor SF-2 of the exposed portion of the particles is 135 or less. This is the gist of the invention.

Advantages of the Invention

[0013] According to the present invention, it is possible to achieve both improvement in the image quality of halftone images and improvement in transferability by suppressing light scattering in the surface layer of the photoreceptor.

Brief Description of the Drawings

[0014] [Figure 1] It is a conceptual diagram of each layer structure in the cross section of the photoreceptor. [Figure 2] It is a conceptual diagram of each layer structure in the cross section of the photoreceptor. [Figure 3] It is a conceptual diagram of each layer structure in the cross section of the photoreceptor. [Figure 4] It is a conceptual diagram of the exposed area of particles when the photoreceptor is viewed from above. [Figure 5] It is a conceptual diagram for explaining an electrophotographic apparatus. [Figure 6] It is a conceptual diagram for explaining the exposed volume of particles in the surface layer of the photoreceptor.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, preferred embodiments of the present invention will be described. [Electrophotographic Photoreceptor] The electrophotographic photoreceptor of the present invention comprises a support and a surface layer containing a photosensitive layer and particles provided on the support. The electrophotographic photoreceptor of the present invention can be used as a cylindrical electrophotographic photoreceptor in which the photosensitive layer and surface layer are formed on a cylindrical support, but it can also be in the shape of a belt or a sheet.

[0016] The electrophotographic photoreceptor of the present invention is used in an image forming method comprising: a charging step of charging the surface of the electrophotographic photoreceptor; an exposure step of exposing the charged electrophotographic photoreceptor to light to form an electrostatic latent image; a developing step of supplying toner to the electrophotographic photoreceptor on which the electrostatic latent image has been formed to form a toner image; and a transfer step of transferring the toner image formed on the electrophotographic photoreceptor.

[0017] One method for manufacturing the electrophotographic photoreceptor of the present invention is to prepare coating solutions for each layer, as described later, apply them in the desired order, and then dry them. Methods for applying the coating solutions include immersion coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, immersion coating is preferred from the viewpoint of efficiency and productivity.

[0018] The present invention relates to an electrophotographic photoreceptor having a support and a photosensitive layer on the support, wherein the surface layer of the electrophotographic photoreceptor contains particles, and the surface layer has particles that are partially exposed from the surface layer, and satisfies the following three conditions. (i) The volume-average particle size of the particle is 50.0 nm or more and 350.0 nm or less. (ii) In the cross-section of the surface layer, the number of particles partially exposed from the surface layer is 80 percent or more of the total number of particles contained in the surface layer. (iii) The total volume of the exposed portions of the particles partially exposed from the surface layer is 30% by volume or more and 80% by volume or less of the total volume of the particles contained in the surface layer.

[0019] The inventors of the present invention have not yet clearly established the mechanism by which the problem is solved by the above configuration, but they surmise the following: To improve transferability in electrophotographic devices, it is necessary to reduce the adhesion between the toner and the electrophotographic photoreceptor. The adhesion between toner and the electrophotographic photoreceptor can be broadly classified into electrostatic and non-electrostatic adhesion. Electrostatic adhesion is primarily influenced by the mirroring force and is therefore heavily dependent on the charge of the toner. The magnitude of the mirroring force is proportional to the charge of the toner and inversely proportional to the square of the distance from the surface of the photoreceptor to which the toner is attached. From the perspective of ensuring sufficient distance between the toner and the surface of the photoreceptor, a method is often employed in which particles are arranged on the surface layer of the photoreceptor to attenuate the mirroring force.

[0020] However, conventional techniques often involved mixing particles into the resin forming the surface layer of the photoreceptor in order to arrange the particles on the surface layer, resulting in a configuration where only a portion of the total number of particles were exposed. Consequently, the interior of the photoreceptor's surface layer became saturated with particles, and during the exposure process in an electrophotographic device to form an electrostatic latent image, light scattering occurred on the surface layer of the photoreceptor, leading to uneven formation of the latent image in halftone images.

[0021] In the electrophotographic photoreceptor of the present invention, in order to suppress light scattering, the surface layer of the photoreceptor must have particles that are partially exposed from the surface layer among the particles contained in the surface layer. Furthermore, in the cross-section of the surface layer, the number of particles partially exposed from the surface layer must be 80% or more of the total number of particles contained in the surface layer. This suppresses light scattering and improves the reproducibility of latent images. If the number of partially exposed particles is less than 80% of the total number of particles contained in the surface layer, the uniformity of the halftone image deteriorates. More preferably, it is 85% or more, and even more preferably 90% or more. Here, particles contained in the surface layer refer to particles that are partially exposed from the surface layer and particles that do not have any portion exposed from the surface layer.

[0022] In addition, to reduce the non-electrostatic adhesion force, it is also necessary to reduce the van der Waals force. To reduce the van der Waals force, it is effective to geometrically reduce the contact area between the toner and the electrophotographic photoreceptor. In this case, the volume-average particle size of the particles contained in the surface layer of the electrophotographic photoreceptor of the present invention must be between 50.0 nm and 350.0 nm. By using particles with this volume-average particle size, the curvature of the partially exposed particles on the surface layer of the photoreceptor becomes higher, which may maximize the reduction of the van der Waals force relative to the curvature of the toner surface. More preferably, the particle size is between 70.0 nm and 250.0 nm, and even more preferably, between 90.0 nm and 200.0 nm.

[0023] Furthermore, if the variation in particle size distribution becomes large, the effect of reducing adhesion between the photoreceptor and toner will vary, so it is preferable that it be within a certain range. In this invention, the volume average particle size and the number average particle size of the particles are measured using an apparatus capable of measuring particle size by dynamic light scattering. It is preferable that (volume average particle size) / (number average particle size), obtained by dividing the volume average particle size by the number average particle size, is 1.5 or less. More preferably, it is 1.4 or less, and even more preferably, 1.3 or less.

[0024] Furthermore, in order to achieve a high level of simultaneous reduction in non-electrostatic adhesion to toner and reduction in light scattering during the exposure process, it is necessary to use an electrophotographic photoreceptor in which the total volume of the exposed portion of particles partially exposed from the surface layer is 30% to 80% of the total volume of particles contained in the surface layer. If it exceeds 80%, the exposed volume of particles becomes too large, and the particles tend to detach from the surface layer of the photoreceptor due to repeated friction with toner during the development process. Furthermore, if the total volume of the exposed portion of particles partially exposed from the surface layer is less than 30% of the total volume of particles contained in the surface layer, the contact area becomes large, the transferability deteriorates, and the uniformity of the halftone image decreases. For this reason, the total volume of the exposed portion of particles partially exposed from the surface layer must be 30% to 80% of the total volume of particles contained in the surface layer. More preferably, it is 35% to 77.5% of the volume, and even more preferably, 37.5% to 75.0% of the volume. The exposed portions of particles partially exposed from the surface layer may be coated in advance with resin or a surface treatment agent. As shown in Figure 6, the volume of the exposed portions of particles partially exposed from the surface layer is the volume of the portion of particles contained in the binder resin of the surface layer that is exposed from the surface of the resin portion of the surface layer.

[0025] The particles on the surface layer of the electrophotographic photoreceptor of the present invention are not particularly limited. Examples of particles include organic resin particles such as acrylic resin particles, inorganic particles such as alumina, silica, and titania, and organic-inorganic hybrid particles.

[0026] Furthermore, conductive particles or charge transport materials may be added to the surface layer coating solution to improve the charge transport capability of the surface layer. Conductive pigments used in the conductive layer described later can be used as conductive particles. Charge transport materials described later can be used as charge transport materials. Additives can also be added for the purpose of improving various functions. Examples of additives include conductive particles, antioxidants, ultraviolet absorbers, plasticizers, and leveling agents.

[0027] Examples of organic resin particles include cross-linked polystyrene particles, cross-linked acrylic resin particles, phenolic resin particles, melamine resin particles, polyethylene particles, polypropylene particles, acrylic resin particles, polytetrafluoroethylene particles, and silicone particles.

[0028] The acrylic resin particles contain polymers of acrylic acid esters or methacrylic acid esters. Among these, styrene-acrylic resin particles are more preferred. The degree of polymerization of the acrylic resin and styrene-acrylic resin, and whether the resin is thermoplastic or thermosetting, are not particularly limited.

[0029] The polytetrafluoroethylene particles may consist mainly of tetrafluoroethylene resin, but may also contain other materials such as trifluoroethylene chloride resin, hexafluoropropylene resin, vinyl fluoride resin, vinylidene fluoride resin, and difluoroethylene chloride resin.

[0030] Examples of organic-inorganic hybrid particles include polymethylsilsesquioxane particles containing siloxane bonds.

[0031] In the present invention, it is preferable to use inorganic particles that have low elasticity and are advantageous in terms of point contact with toner as particles in the surface layer of the electrophotographic photoreceptor. Examples of 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, antimony ion-doped tin oxide, and hydrotalcite. These particles can be used individually or in combination of two or more types. Silica particles are preferred as the inorganic particles. Any known silica particles can be used as the silica particles, and they may be either dry silica particles or wet silica particles. More preferably, wet silica particles obtained by the sol-gel method (hereinafter also referred to as "sol-gel silica") are used.

[0032] The sol-gel silica used in the particles contained in the surface layer of the electrophotographic photoreceptor of the present invention may have a hydrophilic surface or a surface that has been treated to be hydrophobic. Methods for hydrophobic treatment include the sol-gel method, in which the solvent is removed from the silica sol suspension, dried, and then treated with a hydrophobic agent; and the method in which the hydrophobic agent is directly added to the silica sol suspension and treated simultaneously with drying. From the viewpoint of controlling the full width at half maximum of the particle size distribution and the amount of saturated water adsorbed, the method of directly adding the hydrophobic agent to the silica sol suspension is preferred. By hydrophobicizing the particles contained in the surface layer of the electrophotographic photoreceptor of the present invention, it becomes possible to control the exposure state of the particles in the surface layer.

[0033] Examples of hydrophobic treatment agents include the following: 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-butyltrimethoxysilane Alkoxysilanes such as tiltriethoxysilane, 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, methylphenyl 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 oils; 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, as well as salts of the above fatty acids with metals such as zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

[0034] Among these, alkoxysilanes, silazanes, and silicone oils are preferred because they facilitate hydrophobic treatment. These hydrophobic agents may be used individually or in combination of two or more.

[0035] It is preferable that the Young's modulus of the particles contained in the surface layer of the electrophotographic photoreceptor of the present invention is 0.60 GPa or higher. 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 increases when in contact with the toner, resulting in poor transferability.

[0036] In the electrophotographic photoreceptor of the present invention, when the surface layer is viewed from above at a predetermined magnification of a scanning electron microscope, it is preferable that S1 / (S1+S2) (hereinafter also referred to as "coverage rate") satisfies the following formula (A), where S1 is the total area of ​​the exposed portion 401 of the particles and S2 is the total area of ​​the portion 402 other than the exposed portion of the particles. 0.15≦S1 / (S1+S2)≦0.80...Formula (A)

[0037] If the coverage ratio is less than 0.15, the contact area between the toner and the parts of the photoreceptor surface other than the exposed particles increases, leading to increased adhesion and poor transferability. If the coverage ratio exceeds 0.80, the increased exposed particles on the photoreceptor surface bring the contact points between the toner and the particles contained in the surface layer of the photoreceptor closer together. As a result, the contact area between the toner and the particles contained in the surface layer of the photoreceptor increases, leading to increased adhesion and poor transferability. Additionally, during durability testing of the electrophotographic photoreceptor, the amount of toner adhering increases, resulting in poor developability and a decrease in density. A more preferable range is 0.20 to 0.70, and even more preferably 0.25 to 0.60.

[0038] Furthermore, it is preferable that the coefficient of variation of the coverage ratio S1 / (S1+S2) is 25% or less. If the coefficient of variation exceeds 25%, unevenness will occur in the point contact state, and the transferability will deteriorate. More preferably, it is 20% or less, and even more preferably, 15% or less.

[0039] In the electrophotographic photoreceptor of the present invention, it is preferable that the average circularity of the shape of the exposed portion of the particles is 0.90 or higher when the surface layer is viewed from above. If the average circularity is less than 0.90, point contact between the toner and the surface layer of the electrophotographic photoreceptor becomes difficult, resulting in poor transferability and worsening of dot scattering on the image. More preferably, the average circularity of the shape of the exposed portion of the particles is 0.92 or higher, and even more preferably 0.94 or higher. In the electrophotographic photoreceptor of the present invention, when the surface layer is viewed from above, it is preferable that the SF-2 of the shape of the exposed portion of the particles, as described later, is 135 or less. If SF-2 exceeds 135, point contact between the toner and the surface layer of the electrophotographic photoreceptor becomes difficult, resulting in poor transferability and worsening of dot scattering on the image.

[0040] In the electrophotographic photoreceptor of the present invention, it is preferable that the amount of methyl ethyl ketone insoluble matter in the surface layer during sintering is 5.0% by mass or less relative to the total mass of the surface layer. If the MEK insoluble matter exceeds 5.0% by mass, light scattering on the photoreceptor surface increases, which may worsen the evaluation of the roughness of the halftone image. More preferably, the MEK insoluble matter is 4.5% by mass or less.

[0041] The electrophotographic photoreceptor of the present invention can have several layer configurations. Layer configuration 1: An electrophotographic photoreceptor having a support 104 and a photosensitive layer on the support, wherein the surface layer of the electrophotographic photoreceptor contains particles 101, the photosensitive layer has a charge generating layer 103 and a charge transport layer 102 on the charge generating layer, and the charge transport layer is the surface layer of the electrophotographic photoreceptor. (Figure 1) Layer configuration 2: An electrophotographic photoreceptor having a support 205 and a photosensitive layer on the support, wherein the surface layer of the electrophotographic photoreceptor contains particles 201, the photosensitive layer has a charge generation layer 204 and a charge transport layer 203 on the charge generation layer, and the electrophotographic photoreceptor further has a protective layer 202 on the photosensitive layer, the protective layer being the surface layer. (Figure 2) Layer configuration 3: An electrophotographic photoreceptor having a support 304 and a photosensitive layer on the support, wherein the surface layer of the electrophotographic photoreceptor contains particles 301, the photosensitive layer is a single-layer type photosensitive layer 303, and the electrophotographic photoreceptor further has a protective layer 302 on the photosensitive layer, the protective layer being the surface layer. (Figure 3)

[0042] To achieve a high level of both transferability and halftone image quality, the configuration of layer configuration 1 or layer configuration 2 is preferred, and more preferably, the configuration of layer configuration 1, from the viewpoint of easily controlling the arrangement of particles in the surface layer. The following explains each layer.

[0043] <Support> The electrophotographic photoreceptor of the present invention has a support. In the present invention, the support is preferably a conductive support. The shape of the support can be cylindrical, belt-shaped, or sheet-shaped. Among these, a cylindrical support is preferred. Furthermore, the surface of the support may be subjected to electrochemical treatments such as anodizing, blasting, or cutting. Suitable materials for the support include metal, resin, and glass. Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among these, an aluminum support made of aluminum is preferred. Furthermore, conductivity may be imparted to resins and glass by processing such as mixing or coating them with conductive materials.

[0044] <Photosensitive layer> The photosensitive layers of electrophotographic photoreceptors are mainly classified into (1) multilayer photosensitive layers and (2) single-layer photosensitive layers. (1) A multilayer photosensitive layer has a charge generating layer containing a charge generating material and a charge transport layer containing a charge transport material. (2) A single-layer photosensitive layer has a photosensitive layer containing both a charge generating material and a charge transport material.

[0045] (1) Stacked photosensitive layer The stacked photosensitive layer comprises a charge generation layer and a charge transport layer.

[0046] (1-1) Charge generation layer The charge generation layer preferably contains a charge generation material and a resin. Examples of charge-generating materials 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. The content of the charge generating material in the charge generating layer is preferably 40% to 85% by mass, and more preferably 60% to 80% by mass, relative to the total mass of the charge generating layer.

[0047] Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, and polyvinyl chloride resin. Among these, polyvinyl butyral resin is more preferred.

[0048] Furthermore, the charge generation layer may contain additives such as antioxidants and ultraviolet absorbers. Specifically, examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0049] The average thickness of the charge generation layer is preferably 0.1 μm or more and 1 μm or less, and more preferably 0.15 μm or more and 0.4 μm or less.

[0050] The charge generation layer can be formed by preparing a coating solution for the charge generation layer containing the above-mentioned materials and solvents, forming a coating film, and drying it. Examples of solvents 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.

[0051] (1-2) Charge transport layer The charge transport layer preferably contains a charge transport material and a binder resin. Examples of charge transport materials include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Among these, triarylamine compounds and benzidine compounds are preferred, and those with the following structures are preferably used. [ka] (In formula (1), R 1 ~R 10 (Each of these independently represents either a hydrogen atom or a methyl group.)

[0052] Examples of the structure shown by equation (1) are shown in equations (1-1) to (1-10). Among these, the structures shown by equations (1-1) to (1-6) are more preferred. [ka]

[0053] As the binder resin, thermoplastic resins are used, including polyester resin, polycarbonate resin, acrylic resin, and polystyrene resin. Among these, polycarbonate resin and polyester resin are preferred. Among polyester resins, polyarylate resin is particularly preferred.

[0054] The content of the charge transport material in the charge transport layer is preferably 25% by mass or more and 70% by mass or less, and more preferably 30% by mass or more and 55% by mass or less, based on the total mass of the charge transport layer.

[0055] The content ratio (mass ratio) of the charge transport material to the binder resin is preferably 4 / 10 to 20 / 10, and more preferably 5 / 10 to 12 / 10.

[0056] Furthermore, the charge transport layer may contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, lubrication agents, and wear resistance enhancers. Specifically, examples 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.

[0057] The average thickness of the charge transport layer is preferably 5 μm to 50 μm, more preferably 8 μm to 40 μm, and particularly preferably 10 μm to 30 μm.

[0058] The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing the above-mentioned materials and solvents, forming a coating film, and drying it. Examples of solvents 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. Furthermore, if the charge transport layer is a surface layer, the particles according to the present invention are contained on the surface of the charge transport layer.

[0059] (2) Single-layer photosensitive layer A single-layer photosensitive layer can be formed by preparing a coating solution for a photosensitive layer containing a charge generating substance, a charge transporting substance, a binder resin, and a solvent, forming this coating film, and drying it. The charge generating substance, charge transporting substance, and resin are the same as the examples of materials in "(1) Multilayer Photosensitive Layer" above.

[0060] <Protective layer> In this invention, a protective layer may be provided on the photosensitive layer. Providing a protective layer can improve durability. The protective layer preferably contains conductive particles and / or charge transport material and a binder resin.

[0061] Examples of conductive particles include metal oxide particles such as titanium dioxide, zinc oxide, tin oxide, and indium oxide. Examples of charge transport materials include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. Among these, triarylamine compounds and benzidine compounds are preferred.

[0062] Examples of binder resins include polyester resins, acrylic resins, phenoxy resins, polycarbonate resins, polystyrene resins, phenolic resins, melamine resins, and epoxy resins. Among these, polycarbonate resins, polyester resins, and acrylic resins are preferred. The protective layer may also be formed as a cured film by polymerizing a composition containing monomers having polymerizable functional groups. Examples of reactions in this case include thermal polymerization, photopolymerization, and radiation polymerization. Examples of polymerizable functional groups in monomers having polymerizable functional groups include acrylic groups and methacrylic groups. Materials with charge transport ability may be used as monomers having polymerizable functional groups.

[0063] Compounds having polymerizable functional groups may also have charge-transporting structures simultaneously with chain-polymerizable functional groups. Triarylamine structures are preferred as charge-transporting structures. Acryloyl groups and methacryloyl groups are preferred as chain-polymerizable functional groups. The number of functional groups may be one or more. In particular, forming a cured film containing a compound with multiple functional groups and a compound with one functional group is especially preferable because the strain generated by polymerization between the multiple functional groups is easily relieved.

[0064] Examples of compounds having one of the above functional groups are shown in (2-1) to (2-6). [ka]

[0065] Examples of compounds having the above-mentioned multiple functional groups are shown in (3-1) to (3-7). [ka]

[0066] The protective layer may contain additives such as antioxidants, UV absorbers, plasticizers, leveling agents, lubrication agents, and wear resistance enhancers. Specifically, examples 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.

[0067] The protective layer can be formed by preparing a protective coating solution containing the above-mentioned materials and solvents, forming a coating film, and then drying and / or curing it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Furthermore, if the protective layer is the surface layer, the particles according to the present invention are contained on the surface of the protective layer. Furthermore, the proportion of the volume of particles to the total volume of the protective layer is preferably 20% to 80% by volume. More preferably 25% to 75% by volume, and even more preferably 35% to 70% by volume.

[0068] <Conductive layer> The electrophotographic photoreceptor of the present invention may have a conductive layer provided on the support. By providing a conductive layer, scratches and irregularities on the surface of the support can be concealed, and light reflection on the surface of the support can be controlled. The conductive layer preferably contains conductive particles and a resin. Examples of materials for the conductive particles include metal oxides, metals, and carbon black.

[0069] Examples of metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of metals include aluminum, nickel, iron, nichrome, copper, zinc, and silver. Among these, it is preferable to use metal oxides as conductive particles, and more preferably titanium oxide, tin oxide, and zinc oxide.

[0070] When using metal oxides as conductive particles, the surface of the metal oxide may be treated with a silane coupling agent or doped with elements such as phosphorus or aluminum, or their oxides. Furthermore, the conductive particles may have a laminated structure comprising core material particles and a coating layer covering those particles. Examples of core material particles include titanium oxide, barium sulfate, and zinc oxide. Examples of the coating layer include metal oxides such as tin oxide. Furthermore, when using metal oxides as conductive particles, their volume-average particle diameter is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

[0071] Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, and alkyd resin. Furthermore, the conductive layer may further contain silicone oil, resin particles, a concealing agent such as titanium dioxide, etc.

[0072] The average thickness of the conductive layer is preferably 1 μm to 50 μm, and particularly preferably 3 μm to 40 μm. The conductive layer can be formed by preparing a coating solution for the conductive layer containing the above-mentioned materials and solvents, forming this coating film, and drying it. Examples of solvents 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. Methods for dispersing conductive particles in the coating solution for the conductive layer include using a paint shaker, sand mill, ball mill, or liquid impaction type high-speed disperser.

[0073] <Underlayer> The electrophotographic photoreceptor of the present invention may have an undercoat layer provided on top of the support or conductive layer. By providing an undercoat layer, the adhesion function between layers is enhanced and a charge injection blocking function can be provided. The undercoat layer preferably contains a resin. Alternatively, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having polymerizable functional groups.

[0074] Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, polyvinylphenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin, polyimide resin, polyamide-imide resin, and cellulose resin.

[0075] Polymerizable functional groups found in monomers possessing polymerizable functional groups include isocyanate groups, blocked isocyanate groups, methylol groups, alkylated methylol groups, epoxy groups, metal alkoxide groups, hydroxyl groups, amino groups, carboxyl groups, thiol groups, carboxylic acid anhydride groups, and carbon-carbon double bond groups.

[0076] Furthermore, the undercoat layer may further contain electron transport materials, metal oxides, metals, conductive polymers, etc., for the purpose of improving electrical properties. Among these, electron transport materials and metal oxides are preferred. Examples of electron transport materials include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, aryl halides, silole compounds, and boron-containing compounds. An electron transport material having polymerizable functional groups may be used as the electron transport material, and a base layer may be formed as a cured film by copolymerizing it with the above-mentioned monomers having polymerizable functional groups. Examples of metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide. Examples of metals include gold, silver, and aluminum.

[0077] Furthermore, the undercoat layer may contain additives. The average thickness of the undercoat layer is preferably 0.1 μm or more and 50 μm or less, more preferably 0.2 μm or more and 40 μm or less, and particularly preferably 0.3 μm or more and 30 μm or less.

[0078] The undercoat can be formed by preparing an undercoat coating solution containing the above-mentioned materials and solvents, forming a coating film, and then drying and / or curing it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0079] [Process cartridges, electrophotographic equipment] The electrophotographic photoreceptor described above can be provided in a process cartridge that integrally supports at least one process selected from the group consisting of a charging process, a developing process, and a transfer process. The process cartridge is characterized by being detachable from the main body of the electrophotographic apparatus.

[0080] Figure 5 shows an example of a schematic configuration of an electrophotographic apparatus having a process cartridge equipped with the electrophotographic photoreceptor of the present invention.

[0081] [Configuration of an electrophotographic device] The electrophotographic apparatus in this embodiment is a so-called tandem type electrophotographic apparatus, equipped with multiple image forming units a to d. The first image forming unit a uses yellow (Y) toner, the second image forming unit b uses magenta (M) toner, the third image forming unit c uses cyan (C) toner, and the fourth image forming unit d uses black (Bk) toner to form an image. These four image forming units are arranged in a line at regular intervals, and the configuration of each image forming unit is substantially common in many ways, except for the color of the toner they contain. Therefore, the electrophotographic apparatus of this embodiment will be described below using the first image forming unit a.

[0082] The first image forming unit a includes a photosensitive drum 1a which is a drum-shaped photosensitive element, a charging roller 2a which is a charging member, a developing means 4a, and a drum cleaning means 5a. The photosensitive drum 1a is an image carrier that holds a toner image and is driven to rotate at a predetermined peripheral speed (process speed) in the direction of the arrow R1 shown in the figure. The developing means 4a contains yellow toner and develops the yellow toner on the photosensitive drum 1a. The drum cleaning means 5a is a means for collecting toner adhering to the photosensitive drum 1a. The drum cleaning means 5a has a cleaning blade that contacts the photosensitive drum 1a and a waste toner box that contains toner and other materials removed from the photosensitive drum 1a by the cleaning blade.

[0083] When a control means (not shown), such as a controller, receives an image signal, the image forming operation is initiated and the photosensitive drum 1a is driven to rotate. During the rotation process, the photosensitive drum 1a is uniformly charged by the charging roller 2a to a predetermined voltage (charging voltage) with a predetermined polarity (negative polarity in this embodiment), and is exposed by the exposure means 3a according to the image signal. As a result, an electrostatic latent image corresponding to the yellow color component image of the target color image is formed on the photosensitive drum 1a. Next, the electrostatic latent image is developed by the developing means 4a at the development position and visualized as a yellow toner image on the photosensitive drum 1a. Here, the normal charging polarity of the toner contained in the developing means 4a is negative polarity, and the electrostatic latent image is reverse-developed by toner charged with the same polarity as the charging polarity of the photosensitive drum 1a by the charging roller 2a. However, the present invention is not limited to this, and can also be applied to electrophotographic devices in which the electrostatic latent image is positively developed by toner charged with the opposite polarity to the charging polarity of the photosensitive drum 1a.

[0084] The endless, movable intermediate transfer belt 10 is conductive and contacts the photosensitive drum 1a to form the primary transfer section N1a, rotating at approximately the same peripheral speed as the photosensitive drum 1a. The intermediate transfer belt 10 is tensioned by opposing rollers 13 as opposing members, and drive rollers 11 and tension rollers 12 and metal rollers 14a as tensioning members, with a total tension of 60N exerted by the tension rollers 12. The intermediate transfer belt 10 can be moved by the rotational drive of the drive rollers 11 in the direction of the arrow R2 shown in the figure. Each metal roller 14 and opposing roller 13 is connected to ground via a Zener diode 15 as a constant voltage element.

[0085] The yellow toner image formed on the photosensitive drum 1a is first transferred from the photosensitive drum 1a to the intermediate transfer belt 10 during the process of passing through the primary transfer section N1a. The remaining primary transfer toner on the surface of the photosensitive drum 1a is cleaned and removed by the drum cleaning means 5a, and then subjected to the subsequent image forming process.

[0086] During the primary transfer, a current is supplied to the conductive intermediate transfer belt 10 from a secondary transfer roller 20, which acts as a secondary transfer member that contacts the outer surface of the intermediate transfer belt 10. As the current supplied from the secondary transfer roller 20 flows in the circumferential direction of the intermediate transfer belt 10, the toner image is primary transferred from the photosensitive drum 1a to the intermediate transfer belt 10. At this time, a voltage of a predetermined polarity (positive polarity in this embodiment) opposite to the normal charging polarity of the toner is applied from the transfer power supply 21 to the secondary transfer roller 20.

[0087] Similarly, the second color magenta toner image, the third color cyan toner image, and the fourth color black toner image are formed and sequentially transferred onto the intermediate transfer belt 10. As a result, four toner images corresponding to the desired color image are formed on the intermediate transfer belt 10. Subsequently, the four toner images supported on the intermediate transfer belt 10 are transferred in one step to the surface of the transfer material P, such as paper or an OHP sheet fed by the paper feeding means 50, as they pass through the secondary transfer section N2 formed by the contact between the secondary transfer roller 20 and the intermediate transfer belt 10. The transfer material P onto which the four toner images have been transferred by secondary transfer is then heated and pressurized in the fixing means 30, causing the four toners to melt and mix, and fix them to the transfer material P. Toner remaining on the intermediate transfer belt 10 after secondary transfer is cleaned and removed by the belt cleaning means 16, which is provided opposite the opposing roller 13 via the intermediate transfer belt 10. Furthermore, a path is provided that does not go through the secondary transfer roller 20, and electrically connects the transfer power supply 21 and each metal roller 14 via a constant current diode 22, which acts as a constant current element. In addition, when a voltage is applied from the transfer power supply 21 to the secondary transfer roller 20, a pinch-off current Id flows through the constant current diode 22, separate from the current It2 that flows toward the secondary transfer section N2.

[0088] The electrophotographic photoreceptor of the present invention can be used in laser beam printers, LED printers, photocopiers, and the like.

[0089] [Evaluation methods for electrophotographic photoreceptors] The evaluation method in this invention will be described.

[0090] <Method for measuring the exposed volume and number of particles on the surface layer of a photoreceptor> The electrophotographic photoreceptor of the present invention is cut into 5mm squares at 50mm from each end along the longitudinal direction, at three points in the center, and at four points at 90-degree intervals along the circumferential direction, for a total of 12 points, to obtain samples. Platinum is coated onto the photosensitive layer of the samples using a vapor deposition system for 30 seconds. Using a FIB-SEM (NVision40, manufactured by Carl Zeiss), the following cutting operations are performed on each sample. Beam type: Gallium ion beam Acceleration voltage: 1kV Size: 3μm (length), 3μm (width), 3μm (depth) Processing step length: 10nm Number of steps: 300 Furthermore, for each step, SEM observation is performed with an acceleration voltage of 5kV and a focal length WD of 5mm, at a field of view of 30,000x magnification. All images captured by the above FIB-SEM are converted into 3D images via an interface using image processing and analysis software ("ExfactVR2.1," manufactured by Visual Science Japan Co., Ltd.). The number of particles exposed from the surface layer of the photoreceptor is measured from the 3D image, and the ratio of the number of exposed particles to the total number of particles contained in the surface layer is calculated.

[0091] Furthermore, the derived 3D image is compared with the image of particles exposed from the surface layer cut by FIB-SEM. The cross-sectional image of the particle cut at the center of gravity is imported via an interface into an image processing and analysis device ("LUZEX AP", manufactured by Nireco Corporation), and the particles in the cross-sectional image are binarized. As shown in the conceptual diagram of Figure 6, the particles in the surface layer exposed from the surface layer of the photoreceptor are approximated as virtual spherical particles whose radius R is half the sum of the major axis L and minor axis l of the particle. The center of gravity of the cross-section of the particles exposed from the surface layer and the center of gravity of the virtual spherical particles coincide. For particles exposed from the surface layer of the photoreceptor, the surface layer 602 where the resin portion is exposed is approximated as a smooth surface with almost no undulation, and calculations are performed accordingly. The depth of the portion in which the particles contained in the surface layer of the electrophotographic photoreceptor of the present invention are embedded from the surface layer 602 of the resin portion is denoted as h. Furthermore, the virtual sphere approximated a circle with particle radius C when the bottom surface of the portion exposed from the surface layer 602 of the resin part was viewed from above. (A conceptual diagram is shown in Figure 6.) The volume V of the exposed portion of the particle is calculated using the following formula (B). V = 4πR 3 / 3―πh(3C 2 +h 2 ) / 6...Equation (B) The volume of the exposed portion of each particle in the three-dimensional image is measured, the total volume of the exposed portions of the particles partially exposed from the surface layer is calculated, and this total is divided by the total volume of the particles contained in the surface layer to calculate the ratio of the volume of the exposed portions of the particles partially exposed from the surface layer.

[0092] <Method for measuring the volume-average particle size of particles according to the present invention> The volume-average particle size is measured using a Zetasizer Nano-ZS (MALVERN). This instrument can measure particle size using dynamic light scattering. First, the sample to be measured is diluted and prepared so that the solid-liquid ratio is 0.10% by mass (±0.02% by mass), and then collected in a quartz cell and placed in the measurement section. If the sample is an inorganic fine particle, water or a methyl ethyl ketone / methanol mixed solvent is used as the dispersion medium; if the sample is a resin particle or an external additive for toner, water is used. As measurement conditions, the refractive index of the sample, the refractive index of the dispersion solvent, viscosity, and temperature are input into the control software Zetasizersoftware 6.30 and measurement is performed. Dn is adopted as the number-average particle size.

[0093] The refractive index of the particles is taken from "Refractive Index of Solids" as described on page 517 of Volume II of the Chemical Handbook, Basic Edition, Revised 4th Edition (edited by the Chemical Society of Japan, Maruzen Co., Ltd.). The refractive index of the resin particles is taken from the refractive index of the resin used in the resin particles, which is included in 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 is used. The refractive index of the toner additive is calculated by taking the weight average of the refractive index of the inorganic fine particles and 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 ​​included in the control software. In the case of a mixed solvent, the weight average of the dispersion media to be mixed is taken.

[0094] <Method for measuring particle coverage and coefficient of variation in the surface layer of a photoreceptor> In the electrophotographic photoreceptor of the present invention, when the surface layer is viewed from above, if the total area of ​​the exposed portion of the particles is S1, then S1 / (S1+S2) can be calculated as follows. For the particles on the surface layer, a 30,000x magnified photographic image of the surface layer of the photoreceptor is taken using a scanning electron microscope (SEM) ("S-4800", manufactured by JEOL Ltd.), and the image is scanned. The particles in the photographic image are then binarized using an image processing and analysis device ("LUZEX AP", manufactured by Nireco Corporation). The coverage rate S1 / (S1+S2)(%) is calculated by taking S1 as the area of ​​the exposed part of the particles on the photoreceptor in one field of view, and S2 as the total area of ​​the parts not exposed. This coverage rate calculation is performed for a total of 10 fields of view, and the average of the obtained coverage rates is taken as the coverage rate of the particles on the surface layer of the photoreceptor.

[0095] <Method for measuring the circularity of exposed particles on the surface layer of a photoreceptor> For the particles on the surface layer, a 30,000x magnified photographic image of the surface layer of the photoreceptor is captured using a scanning electron microscope (SEM) ("S-4800," manufactured by JEOL Ltd.) and then scanned. Image analysis is performed using image processing software (ImageJ (available from https: / / imagej.nih.gov / ij / )) and the particles in the photographic image are binarized. The electrophotographic photoreceptor of the present invention is cut into 5mm squares at 50mm from each end in the longitudinal direction, at three locations in the center, and at four locations at 90 degrees in the circumferential direction, for a total of 12 locations, to create a sample. The central part of the sample is used as one field of view, and the circularity is calculated for all particles in one field of view. The average value of the obtained circularity is taken as the circularity of the exposed particles on the surface layer of the photoreceptor.

[0096] <Method for measuring the degree of unevenness of exposed particles on the surface layer of a photoreceptor> On the other hand, the shape factor of exposed particles on the surface layer of the photoreceptor is determined by, for example, using a Hitachi FE-SEM (S-4800), randomly sampling 100 particle images magnified 30,000 times. The image information is then imported into an image processing and analysis device ("LUZEX AP," manufactured by Nireco Corporation) via an interface, binarized, and analyzed. The value obtained from the following equation C is defined as the shape factor SF-2. (SF-2)=(PER)2 / (AREA)×1 / (4π)×100...(C) (In the formula, PER represents the perimeter of the particle, and AREA represents the projected area of ​​the particle.) The shape factor SF-2 indicates the degree of fine irregularities on the particle surface. Furthermore, if SF-2 exceeds 135, it leads to a decrease in the efficiency of toner image transfer from the photoreceptor to the intermediate transfer medium and transfer material, as well as the loss of characters and line images during transfer, which is undesirable.

[0097] <Method for measuring the Young's modulus of exposed particles on the surface layer of a photoreceptor> As the evaluation instrument, an SPM probe station (NanoNaviReal, Hitachi High-Tech Science Co., Ltd.) equipped with a scanning probe microscope (S-image, Hitachi High-Tech Science Co., Ltd.) with a built-in heater was used. Prior to measurement, the evaluation instrument was calibrated using PMMA (polymethyl methacrylate) particles as a standard material under conditions of an acceptable range of 2.920 ± 0.119 GPa (Young's modulus). The Young's modulus of PMMA measured with the calibrated evaluation instrument was 3.01 GPa. Measurements were performed on the particles in the surface layer of the electrophotographic photoreceptor using SPM, and the average of 10 measurement results for each particle was taken as the Young's modulus of that particle. Furthermore, the average of the Young's moduli of 10 particles was taken as the Young's modulus of the exposed particles in the surface layer of the photoreceptor in this invention. [Examples]

[0098] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples unless it exceeds the gist of the invention. In the following descriptions of examples, "parts" refers to mass unless otherwise specified. The film thickness of each layer of the electrophotographic photoreceptor in the examples and comparative examples was determined using an eddy current film thickness gauge (Fischerscope, manufactured by Fischer Instruments, Inc.) or by converting the mass per unit area to specific gravity. Furthermore, Examples 1-36, 43, 44, 53, 55, 57, 58, 59, 66, 67, and 71-73 are for reference only.

[0099] Table 1 shows the types of particles contained in the surface layer of the electrophotographic photoreceptor of the present invention, the manufacturer, the number-average particle size, the volume-average particle size, and the (volume-average particle size) / (number-average particle size). [Table 1]

[0100] (Preparation of surface-treated particles 1) • 10 parts by mass of methanol • Particle 1 (listed in Table 1): 5 parts by mass The mixture was then 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 the mixture was stirred at room temperature for 60 minutes. After removing the solvent with an evaporator, surface-treated particles 1 were prepared by heating at 140°C for 60 minutes. The volume-average particle size was 136 nm, and the number-average particle size was 124 nm.

[0101] <Manufacturing example of electrophotographic photoreceptor 1> (Creation of support) An aluminum cylinder (JIS-A3003, aluminum alloy) with a diameter of 20 mm and a length of 257.5 mm was used as the support (conductive support).

[0102] (Example of preparation of conductive layer coating solution 1) • Anatase-type 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 into a 1L aqueous suspension and heated to 60°C. A niobium solution, prepared by dissolving 3 parts by mass of niobium pentachloride (NbCl5) in 100 mL of 11.4 mol / L hydrochloric acid, was mixed with 600 mL of titanium sulfate solution containing 33.7 parts by mass of Ti to create a titanium-niobium acid solution. This solution was then simultaneously added dropwise over 3 hours to adjust the pH of the suspension to 2-3. After the addition was complete, the suspension was filtered, washed, and dried at 110°C for 8 hours. This dried material was heat-treated 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 niobium-doped titanium oxide. next • Phenolic resin (Product name: Priofen J-325, manufactured by DIC, resin solids content: 60%, density after curing: 1.3 g / cm³) 2 ) 50 parts by mass 1-Methoxy-2-propanol 35 parts by mass ·Metal oxide particles 1 75 parts by mass • Glass beads (average particle size 1.0 mm) 120 parts by mass The mixture was placed in a vertical sand mill and dispersed for 4 hours under the conditions of dispersion temperature 23±3℃ and rotation speed 1500 rpm (peripheral speed 5.5 m / s) to obtain metal oxide particle dispersion 1. 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 mass • Silicone resin particles (product name: Tospearl 120, manufactured by Momentive Performance Materials, average particle size: 2 μm, density: 1.3 g / cm³) 2 ) 10 parts by mass The conductive layer coating solution 1 was prepared by adding and stirring the mixture, and then pressure filtering it using PTFE filter paper (product name: PF060, manufactured by Advantec Toyo).

[0103] (Example of fabrication of conductive layer 1) The conductive layer coating liquid 1 was applied to a support by immersion, and this was heated at 140°C for 1 hour to form a conductive layer 1 with a thickness of 20 μm.

[0104] (Example of preparation of coating solution 1 for the undercoat) • Rutile-type titanium dioxide particles (average primary particle size: 50 nm, manufactured by Teika) 100 parts by mass • Phenolic resin (product name: Priofen J-325, manufactured by Dainippon Ink and Chemicals, Inc., resin solids content: 60% by mass) 132 parts by mass • Toluene 500 parts by mass • Vinyltrimethoxysilane (product name: KBM-1003, manufactured by Shin-Etsu Chemical Co., Ltd.) 5 parts by mass • Glass beads (0.8 mm in diameter) 450 parts by mass The mixture was stirred for 8 hours. Then, toluene was removed by vacuum distillation, and the mixture was dried at 120°C for 3 hours to obtain rutile-type titanium dioxide particles 1 surface-treated with vinyltrimethoxysilane. • Surface-treated rutile-type titanium oxide particles: 18 parts by mass • N-methoxymethylated nylon (product name: Trezin EF-30T, manufactured by Nagase ChemteX) 4.5 parts by mass • Copolymerized nylon resin (product name: Amiran CM8000, manufactured by Toray) 1.5 parts by mass • Methanol 90 parts by mass 1-Butanol 60 parts by mass • 15 parts by mass of acetone • Glass beads (average particle size 1.0 mm) 120 parts by mass The following were mixed and dispersed in a vertical sand mill for 5 hours to prepare coating solution 1 for the undercoat layer.

[0105] (Example of fabrication of the lower layer 1) The undercoating liquid 1 for the undercoat layer was applied to the conductive layer 1 by immersion, and the undercoat layer 1 with a thickness of 1.0 μm was formed by heating at 170°C for 30 minutes.

[0106] (Example of fabrication of charge generation layer 1) • Hydroxygallium phthalocyanine (having peaks at 7.5° and 28.4° in the chart obtained from CuKα characteristic X-ray diffraction) 10 parts by mass • Polyvinyl butyral resin (product name: S-Rec BX-1, manufactured by Sekisui Chemical Co., Ltd.) 5 parts by mass Cyclohexanone 200 parts by mass • Glass beads 200 parts by mass 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 added to this mixture to further dilute it and obtain coating solution 1 for the charge generation layer. The obtained coating solution 1 for the charge generation layer was applied to the undercoat layer 1 by immersion and dried at 95°C for 10 minutes to form a charge generation layer 1 with a film thickness of 0.20 μm.

[0107] (Example of fabrication of charge transport layer 1) Next, I prepared the following materials. • 5 parts by mass of the charge-transporting material (hole-transporting material) represented by the above structural formula (1-1) • 5 parts by mass of a charge-transporting substance (hole-transporting substance) represented by the above structural formula (1-3) • Polycarbonate (product name: Yupiron Z400, manufactured by Mitsubishi Engineering Plastics Corporation) 10 parts by mass • 0.02 parts of polycarbonate resin having copolymer units of the following structural formulas (C-1) and (C-2) (x / y=0.95 / 0.05: viscosity-average molecular weight=20000) These were dissolved in a mixed solvent of 60 parts by mass of toluene, 3 parts by mass of methyl benzoate, and 15 parts by mass of tetrahydrofuran to prepare a coating solution 1 for the charge transport layer. This coating solution 1 for the charge transport layer was applied to the charge generating layer 1 by immersion 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 with a thickness of 15 μm. [ka] [ka]

[0108] (Example 1 of fabrication of a surface layer containing particles) Next, I prepared the following materials. • Particle 1 (listed in Table 1) 1.2 parts by mass • Siloxane-modified acrylic compound (product name: Cymac US270, manufactured by Toagosei Co., Ltd.) 0.1 part by mass • Cyclohexane 30 parts by mass 1-Propanol 70 parts by mass The ingredients were mixed and stirred to prepare coating solution 1 for the surface layer. The surface layer coating solution was applied to the charge transport layer 1 by immersion 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 thickness of the charge transport layer of the electrophotographic photoreceptor 1 [μm], the volume average particle size of the particles contained in the surface layer [nm], the number ratio of particles exposed from the surface layer [number %], the volume ratio of particles exposed from the surface layer [number %], the coverage rate S1 / (S1+S2) and coefficient of variation by particles exposed from the surface layer, the average circularity and SF-2 of the exposed portion of the particles exposed from the surface layer, the Young's modulus of the surface of the particles exposed from the surface layer [GPa], the volume average particle size / number average particle size of the particles, the amount of ash content at sintering of the insoluble portion of the surface layer relative to methyl ethyl ketone [mass %], and the content of particles contained in the surface layer [volume %] were measured. The results are shown in Table 3.

[0109] <Manufacturing Examples of Electrophotographic Photoreceptors 2-36> In the example of manufacturing electrophotographic photoreceptor 1, electrophotographic photoreceptors 2 to 36 were manufactured in the same manner as electrophotographic photoreceptor 1, except that the temperature at which the charge transport layer coating solution 1 used in the example of manufacturing the charge transport layer 1 was immersed and applied onto the charge generating layer 1 to form a coating film and dried, the type and amount of particles contained in the surface layer, and the amounts of cyclohexane and 1-propanol added were changed as shown in Table 2. The physical properties of electrophotographic photoreceptors 2 to 36 were measured. The results are shown in Table 3.

[0110] [Table 2]

[0111] [Table 3]

[0112] <Manufacturing example of electrophotographic photoreceptor 37> In the example of manufacturing the electrophotographic photoreceptor 1 described above, the charge transport layer was manufactured in the same manner as in the example of manufacturing the charge transport layer 1, except that the charge transport layer coating solution 37 was immersed and applied onto the charge generating layer 37 to form a coating film, and the coating film was dried at a drying temperature of 120°C for 5 minutes to produce a charge transport layer 37 with a thickness of 15 μm.

[0113] (Example 2 of fabrication of a surface layer containing particles) Next, I prepared the following materials. • Particle 1 (listed in Table 1) 1.2 parts by mass • 0.1 parts by mass of the charge-transporting material (hole-transporting material) represented by the above structural formula (2-1) • 0.2 parts by mass of a charge-transporting material (hole-transporting material) represented by the above structural formula (3-1) • Siloxane-modified acrylic compound (product name: Cymac US270, manufactured by Toagosei Co., Ltd.) 0.1 part by mass • Cyclohexane 30 parts by mass 1-Propanol 70 parts by mass The ingredients were mixed and stirred to prepare coating solution 2 for the surface layer. This surface layer coating liquid 2 was applied to the charge transport layer 1 by immersion to form a coating film, and the resulting coating film was dried at 40°C for 5 minutes. Subsequently, under a nitrogen atmosphere, the support (irradiated object) was rotated at a speed of 300 rpm while the electron beam was irradiated onto the coating for 1.6 seconds under conditions of an acceleration voltage of 70 kV and a beam current of 5.0 mA. The dose at the outermost surface layer was 15 kGy. Then, under a nitrogen atmosphere, the temperature was raised from 25°C to 100°C over 20 seconds to perform the first heating, forming a surface layer with a thickness of 1.0 μm. The oxygen concentration from electron beam irradiation to the subsequent heat treatment was 10 ppm or less. Next, the coating was allowed to cool naturally in air until its temperature reached 25°C, and then a second heat treatment was performed for 20 minutes under conditions of the coating reaching 100°C. In this way, an electrophotographic photoreceptor 37 was fabricated. The following parameters were measured for the electrophotographic photoreceptor 37: film thickness of the charge transport layer [μm], film thickness of the surface layer [μm], volume-average particle size of particles contained in the surface layer [nm], number ratio of particles exposed from the surface layer [number %], volume ratio of particles exposed from the surface layer [number %], coverage rate S1 / (S1+S2) by particles exposed from the surface layer, average circularity of the exposed portion of the particles exposed from the surface layer, Young's modulus of the surface of the particles exposed from the surface layer [GPa], volume-average particle size / number-average particle size, ash content of the insoluble material in the surface layer at sintering relative to methyl ethyl ketone [mass %], and particle content in the surface layer [volume %]. The results are shown in Table 5.

[0114] <Manufacturing Examples of Electrophotographic Photoreceptors 38-72> In the example of manufacturing the electrophotographic photoreceptor 37, electrophotographic photoreceptors 38 to 72 were manufactured in the same manner as the electrophotographic photoreceptor 37, except that the temperature at which the charge transport layer coating solution 37 was immersed and applied onto the charge generating layer 37 to form a coating film and dried, and the type and amount of particles contained in the surface layer, as well as the amounts of cyclohexane and 1-propanol added, were changed as shown in Table 4, in the example of manufacturing the surface layer containing particles 2. The physical properties of the electrophotographic photoreceptors 38 to 72 were measured. The results are shown in Table 5.

[0115] [Table 4]

[0116] [Table 5]

[0117] [Manufacturing example of electrophotographic photoreceptor 73] The manufacturing process for the electrophotographic photoreceptor 1 was carried out similarly up to the first example of the undercoat layer manufacturing.

[0118] (Formation of a single-layer photosensitive layer) [Manufacturing of photoreceptors] The following compounds were added to the container. Charge generating agent: Titanylphthalocyanine, 2 parts by mass Hole transport agent (HTM-1) 65 parts by mass Electron transport agent (ETM-1) 33.5 parts by mass Electron transport agent (ETM-2) 33.5 parts by mass Resin (formula D below): 138 parts by mass Solvent (tetrahydrofuran) 400 parts by mass This yielded a photosensitive layer forming coating solution 73. The photosensitive layer forming coating solution 73 was applied to a support by immersion, and this was heated at 40°C for 5 minutes to form a single-layer photosensitive layer 1 with a thickness of 15 μm. [ka] [ka] [ka]

[0119] (Example 3 of fabrication of a surface layer containing particles) Next, I prepared the following materials. • Particle 1 (listed in Table 1) 1.2 parts by mass • Siloxane-modified acrylic compound (product name: Cymac US270, manufactured by Toagosei Co., Ltd.) 0.1 part by mass • Cyclohexane 30 parts by mass 1-Propanol 70 parts by mass The ingredients were mixed and stirred to prepare coating solution 3 for the surface layer. The surface layer coating solution 3 was immersed onto a single-layer photosensitive 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 73. The thickness of the charge transport layer [μm], the volume-average particle size of the particles contained in the surface layer [nm], the number ratio of particles exposed from the surface layer [number %], the volume ratio of particles exposed from the surface layer [number %], the coverage rate by particles exposed from the surface layer S1 / (S1+S2), the average circularity of the exposed portion of the particles exposed from the surface layer, the Young's modulus of the surface of the particles exposed from the surface layer [GPa], the volume-average particle size / number-average particle size of the particles, the amount of ash content of the insoluble material in the surface layer at sintering relative to methyl ethyl ketone [mass %], and the particle content in the surface layer [volume %] were measured. The results are shown in Table 5.

[0120] <Manufacturing Examples of Electrophotographic Photoreceptors 74-88> In the example of manufacturing electrophotographic photoreceptor 1, electrophotographic photoreceptors 74 to 88 were manufactured in the same manner as electrophotographic photoreceptor 1, except that the temperature at which the charge transport layer coating solution 1 was immersed and applied onto the charge generating layer 1 to form a coating film and dried, the type and amount of particles contained in the surface layer, and the amounts of cyclohexane and 1-propanol added were changed as shown in Table 6. The physical properties of electrophotographic photoreceptors 74 to 88 were measured. The results are shown in Table 7.

[0121] [Table 6]

[0122] [Table 7]

[0123] <Manufacturing Examples of Electrophotographic Photoreceptors 89-103> In the example of manufacturing the electrophotographic photoreceptor 37, electrophotographic photoreceptors 89 to 103 were manufactured in the same manner as the electrophotographic photoreceptor 37, except that the temperature at which the charge transport layer coating solution 37 was immersed and applied onto the charge generation layer 37 to form a coating film and dried, and the type and amount of particles contained in the surface layer, as well as the amounts of cyclohexane and 1-propanol added, were changed as shown in Table 8, compared to Example 2 of manufacturing the surface layer containing particles. The physical properties of the electrophotographic photoreceptors 89 to 103 were measured. The results are shown in Table 9.

[0124] [Table 8]

[0125] [Table 9]

[0126] <Manufacturing Example 104 of Electrophotographic Photoreceptors> In the manufacturing example of electrophotographic photoreceptor 1, electrophotographic photoreceptor 24 was manufactured in the same manner as electrophotographic photoreceptor 1, except that the drying temperature and drying time of the charge transport layer 1 were changed to 130°C and 20 minutes, respectively. The physical properties of electrophotographic photoreceptor 104 were measured. The results are shown in Table 9.

[0127] <Manufacturing Example 105 of Electrophotographic Photoreceptors> In the manufacturing example of electrophotographic photoreceptor 37, electrophotographic photoreceptor 105 was manufactured in the same manner as electrophotographic photoreceptor 37, except that particle 1 was omitted from (Example 2 of manufacturing a surface layer containing particles). The physical properties of electrophotographic photoreceptor 105 were measured. The results are shown in Table 9.

[0128] <Manufacturing Example 106 of Electrophotographic Photoreceptors> In the manufacturing example of electrophotographic photoreceptor 73, electrophotographic photoreceptor 106 was manufactured in the same manner as electrophotographic photoreceptor 1, except that particle 1 was omitted from (Example 3 of manufacturing a surface layer containing particles). The physical properties of electrophotographic photoreceptor 106 were measured. The results are shown in Table 9.

[0129] <Manufacturing Example 107 of Electrophotographic Photoconductor> Among the manufacturing examples of the electrophotographic photoconductor 37, up to the production example of the charge transport layer 2 was produced in the same manner.

[0130] (Production of Surface Treatment Particles 2) · 10 parts by mass of methanol · 5 parts by mass of tin oxide / barium sulfate (number average particle diameter: 100 nm) were added and dispersed at room temperature for 30 minutes using a US homogenizer. Next, 0.25 parts by mass of a side-chain type silicone surface treatment agent having a silicone chain in the side chain of the silicone main chain ("KF9908" manufactured by Shin-Etsu Chemical Co., Ltd.), 0.25 parts by mass of a reactive surface treatment agent (3-methacryloxypropyltrimethoxysilane ("KBM-503" manufactured by Shin-Etsu Chemical Co., Ltd.)) and 10 parts by mass of toluene were added and stirred at room temperature for 60 minutes. After removing the solvent by an evaporator, it was heated at 120 °C for 60 minutes to produce surface treatment particles 2 surface-treated with a reactive surface treatment agent. The volume average particle diameter was 200 nm and the number average particle diameter was 110 nm. Next, the following materials were mixed to prepare a coating solution 107 for the surface layer. · 120 parts by mass of a radically polymerizable monomer (trimethylolpropane trimethacrylate) · 100 parts by mass of surface treatment particles 2 · A polymerization initiator (IRGACURE (registered trademark) 819, manufactured by BASF Japan Ltd.) 10 parts by mass · 800 parts by mass of 2-butanol Subsequently, the obtained coating solution 107 for the surface layer was dip-coated on the charge transport layer 2 to form a coating film, and then irradiated with ultraviolet rays at 16 mW / cm 2 for 1 minute (integrated light quantity 960 mJ / cm 2 ) to form a surface layer with a dry film thickness of 1.0 μm, and an electrophotographic photoconductor 107 was produced. Each physical property of the electrophotographic photoconductor 107 was measured. The results are shown in Table 9.

[0131] <Manufacturing Example 108 of Electrophotographic Photoconductor> A coating solution 108 for the surface layer was obtained by placing 100 parts of monochlorobenzene and 10 parts of spherical polymethylsilsesquioxane particles (product name: Tospar 145, manufactured by Toshiba Silicone Co., Ltd.), which are organic-inorganic hybrid particles with an average particle size of 4.5 μm, into a paint shaker and dispersing them for 3 hours. A charge transport layer coating solution 108 was prepared by mixing the charge transport layer coating solution 1 and the surface layer coating solution 108 in the manufacturing example 1 of the electrophotographic photoreceptor while stirring. This charge transport layer coating solution 108 was immersion coated onto the charge generating layer 1, and the resulting coating film was dried at 120°C for 1 hour to form a charge transport layer 108 with a thickness of 16 μm. Next, the surface of this charge transport layer 108 was treated with a 20% by mass hydrofluoric acid solution to obtain an electrophotographic photoreceptor 108 in which the charge transport layer was the surface layer. Observation using an electron scanning microscope (SEM) revealed that before hydrofluoric acid treatment, the particles were bound to the charge transport layer, whereas after hydrofluoric acid treatment, they were not bound to the charge transport layer, and many gaps existed between the particles and the inner surface of the pores of the charge transport layer 108. The physical properties of the electrophotographic photoreceptor 108 were measured. The results are shown in Table 9.

[0132] <Example of toner particle 1 manufacturing> (Preparation of aqueous medium 1) In a reaction vessel equipped with a stirrer, thermometer, and reflux tubing, 650.0 parts of deionized water and 14.0 parts of sodium phosphate (manufactured by Rasa Industries, dodecahydrate) were added, and the mixture was kept at 65°C for 1.0 hour while purging with nitrogen. Using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), a calcium chloride aqueous solution, prepared by dissolving 9.2 parts of calcium chloride (dihydrate) in 10.0 parts of ion-exchanged water, was added all at once while stirring at 15,000 rpm to prepare an aqueous medium containing a dispersion stabilizer. Furthermore, 10% by mass hydrochloric acid was added to the aqueous medium to adjust the pH to 5.0 to obtain aqueous medium 1.

[0133] (Preparation of polymerizable monomer composition) • Styrene: 60.0 parts CI Pigment Blue 15:3 : 6.5 parts The aforementioned materials were placed in an attritor (manufactured by Mitsui Miike Chemical Machinery Co., Ltd.), and then dispersed using 1.7 mm diameter zirconia particles at 220 rpm for 5.0 hours. After that, the zirconia particles were removed to prepare a colorant dispersion. on the other hand, Styrene: 20.0 parts n-butyl acrylate: 20.0 parts • Crosslinking agent (divinylbenzene): 0.3 parts • Saturated polyester resin: 5.0 parts (Polycondensate of propylene oxide-modified bisphenol A (2 molar adduct) and terephthalic acid (molar ratio 10:12), glass transition temperature (Tg) of 68°C, weight-average molecular weight (Mw) of 10000, molecular weight distribution (Mw / Mn) of 5.12) • Fischer-Tropsch wax (melting point 78°C): 7.0 parts The material was added to the above-mentioned colorant dispersion, heated to 65°C, and then uniformly dissolved and dispersed at 500 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to prepare a polymerizable monomer composition.

[0134] (granulation process) The temperature of aqueous medium 1 was adjusted to 70°C, and while maintaining the rotation speed of the TK homomixer at 15,000 rpm, the polymerizable monomer composition was added to aqueous medium 1, and 10.0 parts of t-butyl peroxypivalate, a polymerization initiator, were added. Granulation was then carried out for 10 minutes while maintaining a stirring speed of 15,000 rpm with the stirring device.

[0135] (Polymerization process and distillation process) After the granulation process, the stirrer was replaced with a propeller-type stirring blade, and polymerization was carried out for 5.0 hours while stirring at 150 rpm and maintaining a temperature of 70°C. Further polymerization was carried out by raising the temperature to 85°C and maintaining the temperature for another 2.0 hours. Subsequently, the reflux tube of the reaction vessel was replaced with a condenser, and the obtained slurry was heated to 100°C for 6 hours to distillate and remove unreacted polymerizable monomers, obtaining a resin particle dispersion.

[0136] <Manufacturing example of external additive 1> External additive 1 was manufactured as follows: 150 parts of 5% aqueous ammonia were added to a 1.5 L glass reaction vessel equipped with a stirrer, dropping nozzle, and thermometer to prepare an alkaline catalyst solution. After adjusting the alkaline catalyst solution to 50°C, 100 parts of tetraethoxysilane and 50 parts of 5% aqueous ammonia were simultaneously added dropwise while stirring, and the mixture was reacted for 8 hours to obtain a silica microparticle dispersion. The obtained silica microparticle dispersion was then dried by spray drying and crushed with a pin mill to obtain silica microparticles. By appropriately changing the above manufacturing conditions, external additive 1 with different primary particle number average particle size R was obtained.

[0137] <Example of Toner 1 manufacturing> 100.00 parts of toner particles 1 and 1.00 part of external additive 1 were added to a Henschel mixer (FM10C model, manufactured by Nippon Coke Industries Co., Ltd.) through which 7°C water was passed through the jacket. Next, after the water temperature in the jacket stabilized at 7°C ± 1°C, the mixture was mixed for 10 minutes at a peripheral speed of 38 m / sec. During this mixing, the amount of water passing through the jacket was appropriately adjusted so that the temperature inside the Henschel mixer tank did not exceed 25°C. The resulting mixture was sieved through a mesh with a mesh opening of 75 μm to obtain toner 1.

[0138] <Example of Toner 2 manufacturing> • Polymerizable monomers: 74 parts styrene, 26 parts n-butyl acrylate • Coloring agent: Carbon black (product name: #25B, manufactured by Mitsubishi Chemical) 7 parts • Crosslinking agent: 0.74 parts divinylbenzene • Electrostatic control agent: Styrene / acrylic resin (product name: FCA-592P, manufactured by Fujikura Chemical Co., Ltd.) 0.37 parts • Molecular weight modifier: Tetraethylthiuram disulfide 1 part • Macromonomer: Polymethacrylate macromonomer (product name: AA6, manufactured by Toa Gosei Chemical Co., Ltd., glass transition temperature Tg=94℃) 0.25 parts The above materials were stirred and mixed using a conventional stirring device, then uniformly dispersed using a media-type disperser, and heated to 63°C. Here, 20 parts of wax A-1 were added to a uniformly dispersed material, mixed, and dissolved to obtain a polymerizable monomer composition. Separately, in a stirring tank at room temperature, a magnesium hydroxide colloidal dispersion (3.0 parts magnesium hydroxide) was prepared by gradually adding an aqueous solution prepared by dissolving 7.4 parts magnesium chloride in 250 parts deionized water to an aqueous solution prepared by dissolving 4.1 parts sodium hydroxide in 50 parts deionized water, while stirring. The polymerizable monomer composition was added to the magnesium hydroxide colloidal dispersion obtained above at room temperature, and the temperature was raised to 60°C and stirred until the droplets stabilized. Five parts of t-butyl peroxy-2-ethylhexanoate (trade name: Perbutyl O, manufactured by NOF Corporation) were added as a polymerization initiator. Subsequently, droplet formation of the polymerizable monomer composition was performed by high-shear stirring at a rotational speed of 15,000 rpm using an in-line emulsifying disperser (trade name: Milder, manufactured by Taiheiyo Kiko Co., Ltd.). A magnesium hydroxide colloidal dispersion containing droplets of the above polymerizable monomer composition was introduced into a reactor equipped with a stirring blade, and the temperature was raised to 89°C and controlled to maintain a constant temperature to carry out the polymerization reaction. Next, when the polymerization conversion rate reached 98%, the system temperature was cooled to 75°C, and 15 minutes after reaching 75°C, 3 parts of methyl methacrylate and 0.36 parts of 2,2'-azobis[2-methyl-N-(1,1-bis(hydroxymethyl)2-hydroxyethyl)propionamide] tetrahydrate (trade name: VA086, manufactured by Wako Pure Chemical Industries, Ltd.), dissolved in 10 parts of deionized water, were added as polymerizable monomers for the shell. After continuing polymerization for a further 3 hours, the reaction was stopped to obtain an aqueous dispersion of colored resin particles with a pH of 9.5. Next, the aqueous dispersion of colored resin particles was heated to 80°C and stripped with nitrogen gas at a flow rate of 0.6 m³ / (hr·kg) for 5 hours, after which the aqueous dispersion was cooled to 25°C. Then, the obtained aqueous dispersion was acid washed with sulfuric acid while stirring at 25°C to lower the system's pH to 6.5 or less, and after separating the water by filtration, 500 parts of freshly deionized water were added to re-slurry and washed with water. After that, dehydration and water washing were repeated several times, and after separating the solid components by filtration, the material was placed in a dryer and dried at 40°C for 12 hours to obtain toner particles 2. To 100 parts of the toner particles obtained as described above, 0.7 parts of hydrophobized silica fine particles with a number-average primary particle size of 7 nm and 1 part of hydrophobized silica fine particles with a number-average primary particle size of 50 nm were added and mixed using a high-speed stirrer (product name: FM Mixer, manufactured by Nippon Coke Industries Co., Ltd.) to produce toner 2.

[0139] [Example 1] The following evaluations were performed using the electrophotographic photoconductor 1 and toner 1. The evaluation results are shown in Table 10.

[0140] <Evaluation Method> <Evaluation of transferability> A modified Canon LBP7700C laser beam printer was used. The modifications involved changing the evaluation unit's body and software to achieve a developing roller rotation speed of 360 mm / sec. Toner was loaded into the toner cartridge of the evaluation machine LBP7700C, and the toner cartridge was left for 24 hours in a normal temperature and humidity environment (25°C, 50%RH; hereinafter also referred to as N / N). After 24 hours in this environment, the toner cartridge was installed in the machine, and 500 copies of an image with a 5.0% print coverage were printed in the center of an A4 sheet of paper in landscape orientation, with a 50mm margin on both sides, under N / N conditions. The paper used was plain paper CS-680 (68g / m²). 2 (Canon Marketing Japan Inc.) was used. The evaluation involved printing solid images at the initial stage of use (after the first print) and after printing 500 pages (after long-term use). The residual toner transfer on the photoreceptor during solid image formation was then taped off using transparent polyester adhesive tape. The density difference was calculated by subtracting the density of the paper with only the adhesive tape attached from the density of the paper with the removed adhesive tape attached. Density measurements were taken at five locations, and the arithmetic mean was calculated. Then, the following determination was made based on this density difference value (referred to as the residual transfer density). The density was measured using an X-Rite color reflectance densitometer (X-rite 500 Series). (Evaluation Criteria) A: Transcription residue concentration is less than 0.20 B: Transcription residue concentration is 0.20 or higher but less than 0.50 C: Transcription residue concentration is 0.50 or higher but less than 1.0 D: Transcription residue concentration is 1.0 or higher

[0141] <Evaluation of sloppiness> The modified machine was tested at 30°C and 80% RH, printing 10,000 character images with a print ratio of 1%. After printing, a halftone (20H) image was formed, and the roughness (density uniformity) of this image was evaluated based on the following criteria. The paper used was plain paper CS-680 (68g / m²). 2 (Canon Marketing Japan Inc.) was used. Note that a 20H image is a value that represents 256 gradations in hexadecimal, and is a halftone image where 00H is solid white (no image) and FFH is solid black (full image). The roughness was evaluated according to the following criteria. Density measurements were taken at 20 locations, and the difference between the maximum and minimum density values ​​(assuming uniform density) was used for the determination as follows. Density was measured using an X-Rite color reflectance densitometer (X-rite 500 Series). (Evaluation Criteria) A: Concentration uniformity is less than 0.04 B: Concentration uniformity is 0.04 or higher and less than 0.06 C: Concentration uniformity is 0.06 or higher and less than 0.08. D: Concentration uniformity is 0.08 or higher

[0142] <Evaluation of the change in endurance concentration> The modified machine was subjected to a durability test under 30°C and 80% RH conditions to evaluate the density changes during the test. An original image with five 20mm square solid black patches placed within the development zone was printed, and the development bias was set so that the initial reflectance density was 1.3. Next, 10,000 copies of a text image with a print ratio of 1% were printed. The paper used was plain paper CS-680 (68g / m²). 2 Canon Marketing Japan Inc. was used. Durability was evaluated by comparing the density difference between the initial image density and the image density after the durability test, using the 5-point average density of the solid black patch. Image density was measured relative to the white areas of the original image using a Macbeth RD918 reflectance densitometer (manufactured by Macbeth). (Evaluation Criteria) A: Concentration difference is less than 0.10 B: Concentration difference is 0.10 or more but less than 0.15 C: Concentration difference is 0.15 or more and less than 0.20 D: Concentration difference is 0.20 or greater

[0143] [Examples 2-72] The electrophotographic photoreceptor and toner combinations shown in Table 4 were evaluated using the same evaluation method as in Example 1. The evaluation results are shown in Table 10.

[0144] [Comparative Examples 1-32, 34, and 35] The electrophotographic photoreceptor and toner combinations shown in Table 4 were evaluated using the same evaluation method as in Example 1. The evaluation results are shown in Table 10.

[0145] [Example 73] Using the electrophotographic photoreceptor 73 and toner 2, evaluation was performed using the same evaluation method as in Example 1 with the electrophotographic apparatus described below. The evaluation results are shown in Table 10. For the electrophotographic apparatus, a modified Brother HL-5200 monochrome laser printer was used. A high-voltage power control system (product name: Model 615-3, manufactured by Trek) was used to supply power to the corona charger from outside the printer. The current flowing through the corona wire of the corona charger was then adjusted to 500 μA. The toner was removed from the toner cartridge for this printer and replaced with toner 2. Additionally, the electrophotographic photoreceptor in the drum unit was removed and replaced with electrophotographic photoreceptor 73, whose initial film thickness was measured for durability evaluation.

[0146] [Comparative Example 33] The electrophotographic photoreceptor 106 and toner 2 were evaluated using the same evaluation method as in Example 73. The evaluation results are shown in Table 10.

[0147] [Table 10]

[0148] This embodiment includes the following configuration. [Configuration 1] A support, and an electrophotographic photoreceptor having a photosensitive layer on the support, The surface layer of the electrophotographic photoreceptor contains particles, The surface layer has particles contained in the surface layer that are partially exposed from the surface layer. The volume-average particle size of the particle is 50.0 nm or more and 350.0 nm or less. In the cross-section of the surface layer, the number of particles partially exposed from the surface layer is 80% or more of the total number of particles contained in the surface layer. An electrophotographic photoreceptor characterized in that the total volume of the exposed portions of the partially exposed particles from the surface layer is 30% by volume or more and 80% by volume or less of the total volume of the particles contained in the surface layer. [Configuration 2] The electrophotographic photoreceptor according to configuration 1, wherein the photosensitive layer comprises a charge generating layer and a charge transport layer on the charge generating layer, and the charge transport layer is the surface layer. [Configuration 3] The electrophotographic photoreceptor according to configuration 1, wherein the photosensitive layer comprises a charge generating layer and a charge transport layer on the charge generating layer, and the electrophotographic photoreceptor further comprises a protective layer on the photosensitive layer, wherein the protective layer is the surface layer. [Structure 4] The electrophotographic photoreceptor according to configuration 1, wherein the photosensitive layer is a single-layer photosensitive layer, and the electrophotographic photoreceptor further has a protective layer on the photosensitive layer, and the protective layer is the surface layer. [Composition 5] When the surface layer is viewed from above, let S1 be the total area of ​​the partially exposed particles from the surface layer, and S2 be the total area of ​​the surface layer other than the partially exposed particles, then S1 / (S1+S2) satisfies the following formula (A) for the electrophotographic photoreceptor according to any one of configurations 1 to 4. 0.15 ≦ S1 / (S1 + S2) ≦ 0.80 ··· Formula (A) [Configuration 6] When the surface layer is viewed from above, when the total area of the exposed portions of the particles is S1 and the total area other than the exposed portions of the particles is S2, the coefficient of variation of S1 / (S1 + S2) is 25% or less, the electrophotographic photoreceptor according to Configuration 5. [Configuration 7] When the surface layer is viewed from above, the SF-2 of the shape of the exposed portions of the particles is 135 or less, the electrophotographic photoreceptor according to any one of Configurations 1 to 6. [Configuration 8] When the surface layer is viewed from above, the average circularity of the shape of the exposed portions of the particles is 0.90 or more, the electrophotographic photoreceptor according to any one of Configurations 1 to 7. [Configuration 9] The Young's modulus of the particles is 0.60 GPa or more, the electrophotographic photoreceptor according to any one of Configurations 1 to 8. [Configuration 10] (Volume average particle diameter) / (Number average particle diameter) of the particles is 1.5 or less, the electrophotographic photoreceptor according to any one of Configurations 1 to 9. [Configuration 11] The ash content at the time of sintering of the insoluble content of methyl ethyl ketone in the surface layer is 5.0 mass% or less with respect to the total mass of the surface layer, the electrophotographic photoreceptor according to any one of Configurations 1 to 10. [Configuration 12] An electrophotographic photoreceptor according to any one of Configurations 1 to 11, and at least one means selected from the group consisting of charging means and developing means are integrally supported and are detachable from the electrophotographic photoreceptor, a process cartridge characterized by this. [Configuration 13] An electrophotographic photoreceptor according to any one of Configurations 1 to 11, and an electrophotographic apparatus having charging means, developing means, and transfer means.

Explanation of Signs

[0149] 1a~d: Electrophotographic photoreceptor 2a~d: Charging roller 3a~d: Exposure means 4a~d: Developing means 5a~d: Cleaning means 10: Intermediate transfer belt 11: Driving roller 12: Tension roller 13: Opposing roller 14: Metal roller 20: Secondary transfer roller 21: Transfer power source 22: Constant current diode 50: Sheet feeding means 50 P: Transfer material 101, 201, 301 particles 102, 203 Charge transport layer 103, 204 Charge generation layer 104, 205, 304 Support 202, 302 Protective layer (surface layer) 303 Single-layer type photosensitive layer Exposed portion of particle 401 Portion other than the exposed portion of particle 402 Exposed portion 601 Surface of the surface layer

Claims

1. An electrophotographic photoreceptor having a support, a photosensitive layer on the support, and a protective layer on the photosensitive layer, wherein the photosensitive layer has a charge generating layer and a charge transport layer on the charge generating layer, and the protective layer is a cured film formed by polymerizing a composition containing a monomer having a polymerizable functional group, The protective layer is the surface layer of the electrophotographic photoreceptor, The surface layer contains particles, The surface layer has particles contained in the surface layer that are partially exposed from the surface layer. The volume-average particle size of the particles is 70.0 nm or more and 250.0 nm or less. The Young's modulus of the particle is 0.60 GPa or higher. In the cross-section of the surface layer, the number of particles partially exposed from the surface layer is 80 percent or more of the total number of particles contained in the surface layer. The total volume of the exposed portions of particles partially exposed from the surface layer is 30% by volume or more and 75% by volume or less of the total volume of particles contained in the surface layer. When the surface layer is viewed from above, let S1 be the total area of ​​the partially exposed parts of the particles, and S2 be the total area of ​​the parts of the surface layer other than the partially exposed parts of the particles. Then, S1 / (S1+S2) satisfies the following equation (A). 0.15≦S1 / (S1+S2)≦0.80...Formula (A) When the surface layer is viewed from above, the shape coefficient SF-2 of the exposed portion of the particles is 135 or less. An electrophotographic photoreceptor characterized by the following features.

2. The electrophotographic photoreceptor according to claim 1, wherein the coefficient of variation of S1 / (S1+S2) is 25% or less.

3. The electrophotographic photoreceptor according to claim 1, wherein when the surface layer is viewed from above, the average circularity of the shape of the exposed portion of the particles is 0.90 or greater.

4. The electrophotographic photoreceptor according to claim 1, wherein the ratio (volume-average particle size) / (number-average particle size), obtained by dividing the volume-average particle size of the particles by the number-average particle size of the particles, is 1.5 or less.

5. The electrophotographic photoreceptor according to claim 1, wherein the amount of ash content of the methyl ethyl ketone insoluble material in the surface layer during sintering is 5.0% by mass or less relative to the total mass of the surface layer.

6. A process cartridge that integrally supports an electrophotographic photoreceptor according to any one of claims 1 to 5 and at least one means selected from the group consisting of a charging means and a developing means, and is detachably attached to the body of an electrophotographic apparatus.

7. An electrophotographic photoreceptor according to any one of claims 1 to 5, and an electrophotographic apparatus having a charging means, a developing means, and a transfer means.

Images