JP2022189754A - Electrophotographic photoreceptor, process cartridge, and electrophotographic device - Google Patents

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

The present invention relates to an electrophotographic photoreceptor, a process cartridge having the electrophotographic photoreceptor, and an electrophotographic apparatus.

2. Description of the Related Art In recent years, in the field of electrophotographic apparatuses such as copiers and printers, there has been a demand for high-speed printing in order to improve productivity. In order to achieve a high speed electrophotographic apparatus, a latent image formed in the exposure process is developed with toner in the development process in the repetition of the charging process, the exposure process, the development process, and the transfer process in the electrophotographic process. , the toner must be efficiently transferred to a medium such as paper or an intermediate transfer member. Also, from the viewpoint of effective use of office space, there is a demand for a compact electrophotographic apparatus in which the cleaning process is omitted by improving the efficiency of the transfer process.

In the transfer process, a predetermined bias is applied to the toner in order to transfer the toner, which is obtained by developing the latent image on the photoreceptor, to 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 surface of the photoreceptor is reduced, thereby reducing the applied bias. As a result, it becomes possible not only to save space in the electrophotographic apparatus for a high-voltage power supply for applying a high bias, but also to suppress toner scattering due to a high transfer bias, thereby achieving an improvement in image quality. . As one method for reducing the adhesion of toner to the surface of the photoreceptor by forming a specific shape on the surface of the photoreceptor, the toner and the surface of the photoreceptor are brought into point contact. It has previously been proposed to include particles on the surface to form convex shapes.

Patent Document 1 discloses a polymerized cured product of a composition containing a polymerizable monomer and an inorganic filler for the purpose of improving cleanability and reducing abrasion of a photoreceptor and a cleaning blade regardless of the amount of lubricant supplied. An electrophotographic photoreceptor is disclosed in which the surface of the outermost layer composed of has a convex structure.

In Patent Document 2, for the purpose of making the surface of a photoreceptor wear-resistant and highly lubricious, at least one of acrylic resin particles and melamine resin particles and a hole-transporting polymer having a polymerizable functional group are disclosed. and an electrophotographic photoreceptor having a surface layer formed by curing a coating film containing a chemical compound.

Patent Document 3 discloses that the surface of the surface layer contains a curable resin and polytetrafluoroethylene particles for the purpose of reducing image unevenness caused by uneven glossiness of a support while maintaining abrasion resistance. , discloses an electrophotographic photoreceptor having an uneven shape formed by mechanical polishing.

Patent Document 4 discloses an electrophotographic photoreceptor containing encapsulated spherical particles surrounded by pores in a matrix component for the purpose of improving the lubricity and cleanability of the surface of the photoreceptor. there is

In Patent Document 5, for the purpose of maintaining the release effect, independent concave portions having a depth of 0.1 μm or more and 10 μm or less are formed on the surface of the surface layer of the photoreceptor, and the mold release is formed in the concave portions. An electrophotographic photoreceptor containing the material is disclosed.

JP 2020-71423 A JP 2019-45862 A JP 2016-118628 A JP 2013-029812 A JP 2009-14915 A

In the electrophotographic apparatus of recent years, there is a demand for both an efficient transfer process for reducing waste toner and high image quality in high-speed output for environmental friendliness. However, in Patent Documents 1 to 3, although the adhesion between the toner and the surface of the photoreceptor is reduced to some extent and the transferability of the toner is improved, the microparticles contained in the surface layer are laminated in multiple layers, so that the photoreceptor It has been found that the laser light scatters during exposure and the uniformity of the halftone image cannot be maintained. Furthermore, in Patent Document 4, when there is a peripheral speed difference between the photoreceptor and the intermediate transfer member or medium in the transfer process, the encapsulated spherical particles move, and the contact area between the toner and the surface of the photoreceptor increases. As a result, a phenomenon of transcriptional decline was observed. Further, in Patent Document 5, it is found that a plurality of release materials are contained in the recessed portion, point contact between the toner and the surface of the photoreceptor cannot be maintained, and it is difficult to maintain good transferability for a long period of time. rice field.

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoreceptor that achieves both improved image quality of halftone images and improved transferability by suppressing light scattering in the surface layer of the photoreceptor.

The above objects are achieved by the present invention described below.
That is, the electrophotographic photoreceptor according to the present invention is an electrophotographic photoreceptor having a support and a photosensitive layer on the support,
the surface layer of the electrophotographic photoreceptor contains particles,
The surface layer has particles partially exposed from the surface layer in the particles contained in the surface layer,
The volume average particle size of the particles 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,
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 with respect to the total volume of the particles contained in the surface layer. and

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

FIG. 2 is a conceptual diagram of each layer structure in a cross section of a photoreceptor; FIG. 2 is a conceptual diagram of each layer structure in a cross section of a photoreceptor; FIG. 2 is a conceptual diagram of each layer structure in a cross section of a photoreceptor; FIG. 2 is a conceptual diagram of exposed areas of particles when the photoreceptor is viewed from above. 1 is a conceptual diagram for explaining an electrophotographic apparatus; FIG. FIG. 2 is a conceptual diagram illustrating the exposed volume of particles in the surface layer of a photoreceptor;

Preferred embodiments of the present invention are described below.
[Electrophotographic photoreceptor]
The electrophotographic photoreceptor of the present invention has a support, a photosensitive layer provided on the support, and a surface layer containing particles. The electrophotographic photoreceptor according to the present invention can be used as a cylindrical electrophotographic photoreceptor in which a photosensitive layer and a surface layer are formed on a cylindrical support, but belt-like or sheet-like forms are also possible.

The electrophotographic photoreceptor of the present invention comprises a charging step of charging the surface of the electrophotographic photoreceptor, an exposure step of exposing the charged electrophotographic photoreceptor to form an electrostatic latent image, and the electrostatic latent image. used in an image forming method comprising a developing step of supplying toner to the electrophotographic photosensitive member on which is formed to form a toner image, and a transferring step of transferring the toner image formed on the electrophotographic photosensitive member be done.

Examples of the method for producing the electrophotographic photoreceptor of the present invention include a method of preparing a coating solution for each layer, which will be described later, coating the desired layers in order, and drying. At this time, the method of applying the coating liquid includes dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, ring coating, and the like. Among these, dip coating is preferable from the viewpoint of efficiency and productivity.

The present invention provides an electrophotographic photoreceptor having a support and a photosensitive layer on the support, wherein a surface layer of the electrophotographic photoreceptor contains particles, and the surface layer is contained in the surface layer. The electrophotographic photoreceptor has particles partially exposed from the surface layer and satisfies the following three conditions.
(i) The particles have a volume average particle size of 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% 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 with respect to the total volume of the particles contained in the surface layer.

Although the mechanism by which the problem is solved by the above configuration is not clear, the inventors speculate as follows.
In order to improve transferability in an electrophotographic apparatus, it is necessary to reduce adhesion between the toner and the electrophotographic photosensitive member. The adhesion force between the toner and the electrophotographic photosensitive member is roughly classified into electrostatic adhesion force and non-electrostatic adhesion force. Since the main factor of the electrostatic adhesion force is the mirror force, it is greatly influenced by the charge amount of the toner. The magnitude of the specular force is proportional to the charge amount of the toner and inversely proportional to the square of the distance of the surface of the photoreceptor to which the toner adheres. From the viewpoint of securing the distance between the toner and the surface of the photoreceptor, a method of arranging particles on the surface layer of the photoreceptor to attenuate the specular force is often adopted.

However, in the prior art, in order to arrange the particles on the surface layer of the photoreceptor, the particles are mixed with the resin forming the surface layer, and a part of the total number of the particles is exposed. I often took As a result, the particles inside the surface layer of the photoreceptor become excessive, and light scattering occurs in the surface layer of the photoreceptor in the exposure process for forming an electrostatic latent image in an electrophotographic apparatus. Non-uniform formation was observed.

In the electrophotographic photoreceptor of the present invention, in order to suppress light scattering, the surface layer of the photoreceptor needs to have particles partially exposed from the surface layer among the particles contained in the surface layer. be. Furthermore, in the cross section of the surface layer, the number of particles partially exposed from the surface layer should be 80% or more of the total number of particles contained in the surface layer. This suppresses light scattering and improves the reproducibility of the latent image. If the number of partially exposed grains is less than 80% by number with respect to the total number of grains contained in the surface layer, the uniformity of the halftone image deteriorates. More preferably, it is 85 number % or more, and still more preferably 90 number % or more. Here, the particles contained in the surface layer are particles that are partially exposed from the surface layer and particles that have no portion exposed from the surface layer.

At the same time, in order 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 photosensitive member. At this time, the volume average particle diameter of the particles contained in the surface layer of the electrophotographic photosensitive member of the present invention should be 50.0 nm or more and 350.0 nm or less. By using particles of this volume average size, the curvature of the partially exposed particles in the surface layer of the photoreceptor is high, maximizing the reduction of Van der Waals forces to the curvature of the toner surface. It is possible that More preferably, it is 70.0 nm or more and 250.0 nm or less, and still more preferably 90.0 nm or more and 200.0 nm or less.

Furthermore, if the particle size distribution of the particles becomes highly uneven, the effect of reducing the adhesion between the photoreceptor and the toner will become uneven. In the present invention, the volume average particle diameter and number average particle diameter of the particles are measured with an apparatus capable of measuring particle diameters by a dynamic light scattering method. It is preferable that (volume average particle diameter)/(number average particle diameter) obtained by dividing the volume average particle diameter of the particles by the number average particle diameter is 1.5 or less. It is more preferably 1.4 or less, still more preferably 1.3 or less.

Furthermore, in order to reduce the light scattering in the exposure step while reducing the non-electrostatic adhesive force with the toner, exposure of the particles partially exposed from the surface layer is required. It is necessary to use an electrophotographic photoreceptor in which the total volume of the parts is 30% by volume or more and 80% by volume or less with respect to the total volume of the particles contained in the surface layer. If it exceeds 80% by volume, the exposed volume of the particles becomes too large, and the particles tend to come off from the surface layer of the photoreceptor due to repeated rubbing of the toner in the developing process. Furthermore, when the total volume of the exposed portions of the particles partially exposed from the surface layer is less than 30% by volume with respect to the total volume of the particles contained in the surface layer, the contact area increases, resulting in transfer. The quality deteriorates and the uniformity of the halftone image decreases. Therefore, the total volume of the exposed portions of the particles partially exposed from the surface layer should be 30% by volume or more and 80% by volume or less with respect to the total volume of the particles contained in the surface layer. . More preferably, it is 35% by volume or more and 77.5% by volume or less, and still more preferably 37.5% by volume or more and 75.0% by volume or less. The exposed portions of the particles that are partially exposed from the surface layer may be previously coated with a resin or a surface treatment agent. As shown in FIG. 6, the volume of the exposed portion of the particles partially exposed from the surface layer is the volume of the particles contained in the binder resin of the surface layer exposed from the surface of the resin portion of the surface layer. Volume.

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

For the purpose of improving the charge-transporting ability of the surface layer, conductive particles or a charge-transporting substance may be added to the coating liquid for the surface layer. As the conductive particles, conductive pigments used in the conductive layer described later can be used. As the charge-transporting substance, the charge-transporting substance described later can be used. Additives can also be added for the purpose of improving various functions. Examples of additives include conductive particles, antioxidants, UV absorbers, plasticizers, and leveling agents.

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

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

The polytetrafluoroethylene particles may be particles mainly composed of tetrafluoroethylene resin, and also include trifluoroethylene chloride resin, hexafluoropropylene resin, vinyl fluoride resin, vinylidene fluoride resin, and difluoride resin. It may contain ethylene dichloride resin and the like.

Organic-inorganic hybrid particles include polymethylsilsesquioxane particles containing siloxane bonds.

As the particles contained in the surface layer of the electrophotographic photosensitive member of the present invention, it is preferable to use inorganic particles that have low elasticity and are advantageous in point contact with the toner.
Magnesium oxide, zinc oxide, lead oxide, tin oxide, tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, tin oxide, titanium oxide , niobium oxide, molybdenum oxide, vanadium oxide, copper aluminum oxide, tin oxide doped with antimony ions, hydrotalcite, and the like. These particles can be used alone or in combination of two or more. As the inorganic particles, silica particles are preferable.
As the silica particles, known silica particles can be used, and either dry silica particles or wet silica particles may be used. More preferably, it is wet silica particles obtained by a sol-gel method (hereinafter also referred to as "sol-gel silica").

The sol-gel silica used for the particles contained in the surface layer of the electrophotographic photosensitive member of the present invention may have a hydrophilic surface or may have a hydrophobic surface.
As a method of hydrophobizing treatment, in the sol-gel method, the solvent is removed from the silica sol suspension, dried, and then treated with a hydrophobizing agent, and the silica sol suspension is directly treated with a hydrophobizing agent. is added and treated at the same time as drying. From the viewpoint of controlling the half-value width of the particle size distribution and controlling the saturated water adsorption amount, a method of directly adding a hydrophobizing agent to the silica sol suspension is preferable.
Hydrophobic treatment of the particles contained in the surface layer of the electrophotographic photosensitive member of the present invention makes it possible to control the exposure state of the particles in the surface layer.

Hydrophobizing agents include the following.
chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, t-butyldimethylchlorosilane, vinyltrichlorosilane;
Tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, n-butyltrimethoxysilane, i-butyltrimethoxysilane silane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, i-butyltri ethoxysilane, decyltriethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane Alkoxysilanes such as silane;
Hexamethyldisilazane, hexaethyldisilazane, hexapropyldisilazane, hexabutyldisilazane, hexapentyldisilazane, hexahexyldisilazane, hexacyclohexyldisilazane, hexaphenyldisilazane, divinyltetramethyldisilazane, dimethyltetravinyl silazanes such as disilazane;
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 oils such as silicone oil, amino-modified silicone oil, fluorine-modified silicone oil, and terminally reactive silicone oil;
siloxanes such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethyldisiloxane, octamethyltrisiloxane;
Fatty acids and metal salts thereof include 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, arachidonic acid, and the like. Long-chain fatty acids, salts of said fatty acids with metals such as zinc, iron, magnesium, aluminum, calcium, sodium and lithium.

Among these, alkoxysilanes, silazanes, and silicone oils are preferably used because they are easily subjected to hydrophobizing treatment. One of these hydrophobizing agents may be used alone, or two or more thereof may be used in combination.

The Young's modulus of the particles contained in the surface layer of the electrophotographic photoreceptor of the present invention is preferably 0.60 GPa or more. If the Young's modulus of the particle surface is less than 0.60 GPa, the contact area between the surface of the toner and the surface of the particle increases when the toner is brought into contact with the toner, resulting in poor transferability.

When the surface layer of the electrophotographic photoreceptor of the present invention is viewed from above at a predetermined magnification of a scanning electron microscope, as shown in FIG. When the total area of 402 other than the portion is S2, S1/(S1+S2) (hereinafter also referred to as "coverage") preferably satisfies the following formula (A).
0.15≦S1/(S1+S2)≦0.80 Formula (A)

If the coverage is less than 0.15, the contact area between the toner and the portion other than the exposed portion of the particles on the surface of the photoreceptor increases, resulting in increased adhesion and poor transferability. When the coverage exceeds 0.80, the exposed portion of the particles on the surface of the photoreceptor increases, and the distance between the contact portions of the toner and the particles contained in the surface layer of the photoreceptor tends to be shortened. As a result, the contact area between the toner and the particles contained in the surface layer of the photoreceptor increases, resulting in increased adhesion and poor transferability. As a result, the developability deteriorates, resulting in a decrease in density. A more preferable range is from 0.20 to 0.70, and more preferably from 0.25 to 0.60.

Also, the coefficient of variation of the coverage S1/(S1+S2) is preferably 25% or less. If the coefficient of variation exceeds 25%, the state of point contact becomes uneven, resulting in poor transferability. More preferably, it is 20% or less, and still more preferably 15% or less.

In the electrophotographic photoreceptor of the present invention, when the surface layer is viewed from above, the average circularity of the shape of the exposed portions of the particles is preferably 0.90 or more.
If the average circularity is less than 0.90, point contact between the toner and the surface layer of the electrophotographic photosensitive member becomes difficult, resulting in poor transferability and poor scattering of dots on the image. More preferably, the average circularity of the shape of the exposed portions of the grains is 0.92 or more, more preferably 0.94 or more.
In the electrophotographic photoreceptor of the present invention, when the surface layer is viewed from above, the SF-2 of the shape of the exposed portions of the particles, which will be described later, is preferably 135 or less. If SF-2 exceeds 135, point contact between the toner and the surface layer of the electrophotographic photosensitive member becomes difficult, resulting in poor transferability and poor scattering of dots on the image.

In the electrophotographic photoreceptor of the present invention, the ash content of the insoluble portion of methyl ethyl ketone in the surface layer at the time of sintering is preferably 5.0% by mass or less with respect to the total mass of the surface layer. If the MEK-insoluble content exceeds 5.0% by mass, the light scattering on the surface of the photoreceptor increases, and there is a possibility that the rough evaluation of the halftone image will deteriorate. More preferably, the MEK-insoluble content is 4.5% by mass or less.

The electrophotographic photoreceptor of the present invention can have several layer structures.
Layer structure 1: An electrophotographic photoreceptor having a support 104 and a photosensitive layer on the support, the surface layer of the electrophotographic photoreceptor containing particles 101, the photosensitive layer comprising a charge generation layer 103 and a An electrophotographic photoreceptor having a charge transport layer 102 on the charge generating layer, wherein the charge transport layer is the surface layer. (Fig. 1)
Layer structure 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 and the photosensitive layer comprises a charge generating layer 204 and the An electrophotographic photoreceptor having a charge transport layer 203 on the charge generating layer, further comprising a protective layer 202 on the photoreceptive layer, wherein the protective layer is the surface layer. (Figure 2)
Layer structure 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 and the photosensitive layer is a single layer. An electrophotographic photoreceptor which is a layered photosensitive layer 303, further has a protective layer 302 on the photosensitive layer, and the protective layer is the surface layer. (Fig. 3)

From the viewpoint of facilitating control of the arrangement of particles in the surface layer, it is preferable to use the layer structure 1 or the layer structure 2, and more preferably the layer structure 2 to achieve both high-level transferability and halftone image quality. This is the structure of the layer structure 1.
Each layer will be described below.

<Support>
The electrophotographic photoreceptor of the present invention has a support. In the present invention, the support is preferably an electrically conductive support. Further, the shape of the support includes a cylindrical shape, a belt shape, a sheet shape, and the like. Among them, a cylindrical support is preferable. Further, the surface of the support may be subjected to electrochemical treatment such as anodization, blasting treatment, cutting treatment, or the like.
The material of the support is preferably metal, resin, glass, or the like.
Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among them, an aluminum support using aluminum is preferable.
Conductivity may be imparted to the resin or glass by treatment such as mixing or coating with a conductive material.

<Photosensitive layer>
The photosensitive layer of the electrophotographic photoreceptor is mainly classified into (1) laminated photosensitive layer and (2) single layer photosensitive layer. (1) The laminated photosensitive layer has a charge generation layer containing a charge generation substance and a charge transport layer containing a charge transport substance. (2) A single-layer type photosensitive layer has a photosensitive layer containing both a charge-generating substance and a charge-transporting substance.

(1) Laminated photosensitive layer The laminated photosensitive layer has a charge generation layer and a charge transport layer.

(1-1) Charge Generation Layer The charge generation layer preferably contains a charge generation substance and a resin.
Examples of charge-generating substances include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferred. Among the phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferred.
The content of the charge-generating substance in the charge-generating layer is preferably 40% by mass or more and 85% by mass or less, more preferably 60% by mass or more and 80% by mass or less, relative to the total mass of the charge-generating layer. preferable.

Resins include polyester resins, polycarbonate resins, polyvinyl acetal resins, polyvinyl butyral resins, acrylic resins, silicone resins, epoxy resins, melamine resins, polyurethane resins, phenol resins, polyvinyl alcohol resins, cellulose resins, polystyrene resins, and polyvinyl acetate resins. , polyvinyl chloride resin, and the like. Among these, polyvinyl butyral resin is more preferable.

The charge generation layer may further contain additives such as antioxidants and UV absorbers. Specific examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, and the like.

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

The charge-generating layer can be formed by preparing a charge-generating layer coating solution containing the above materials and a solvent, forming a coating film, and drying the coating film. Solvents used in the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents and the like.

（式（１）中、Ｒ^１～Ｒ^１０は、それぞれ独立して、水素原子、又はメチル基を表す。） (1-2) Charge Transport Layer The charge transport layer preferably contains a charge transport substance and a binder resin.
Examples of charge-transporting substances include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these substances. be done. Among these, triarylamine compounds and benzidine compounds are preferable, and those having the following structures are preferably used.

(In Formula (1), R ¹ to R ¹⁰ each independently represent a hydrogen atom or a methyl group.)

Examples of structures represented by formula (1) are shown in formulas (1-1) to (1-10). Among these, structures represented by formulas (1-1) to (1-6) are more preferable.

As the binder resin, a thermoplastic resin is used, and examples thereof include polyester resin, polycarbonate resin, acrylic resin, and polystyrene resin. Among these, polycarbonate resins and polyester resins are preferred. A polyarylate resin is particularly preferable as the polyester resin.

The content of the charge transport substance in the charge transport layer is preferably 25% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 55% by mass or less, relative to the total mass of the charge transport layer. preferable.

The content ratio (mass ratio) between the charge transport substance and the binder resin is preferably 4/10 to 20/10, more preferably 5/10 to 12/10.

The charge transport layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slipperiness agents and wear resistance improvers. Specifically, 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, boron nitride particles. etc.

The average film thickness of the charge transport layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

The charge-transporting layer can be formed by preparing a charge-transporting-layer coating solution containing each of the materials and solvents described above, forming a coating film thereon, and drying the coating film. Solvents used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents. Among these solvents, ether solvents and aromatic hydrocarbon solvents are preferred.
When the charge transport layer serves as the surface layer, the particles of the present invention are contained on the surface of the charge transport layer.

(2) Single-layer type photosensitive layer A single-layer type photosensitive layer is formed by preparing a photosensitive layer coating solution containing a charge-generating substance, a charge-transporting substance, a binder resin and a solvent, forming this coating film, and drying it. can be formed with The charge-generating substance, charge-transporting substance, and resin are the same as those exemplified in the above “(1) Laminated photosensitive layer”.

<Protective layer>
In the present invention, a protective layer may be provided on the photosensitive layer. Durability can be improved by providing a protective layer.
The protective layer preferably contains conductive particles and/or a charge-transporting substance, and a binder resin.

Conductive particles include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide. Charge-transporting substances 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.

Examples of binder resins include polyester resins, acrylic resins, phenoxy resins, polycarbonate resins, polystyrene resins, phenol resins, melamine resins, and epoxy resins. Among them, polycarbonate resins, polyester resins, and acrylic resins are preferred. Alternatively, the protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. The reaction at that time includes thermal polymerization reaction, photopolymerization reaction, radiation polymerization reaction, and the like. Examples of the polymerizable functional group possessed by the monomer having a polymerizable functional group include an acrylic group and a methacrylic group. A material having charge transport ability may be used as the monomer having a polymerizable functional group.

A compound having a polymerizable functional group may have a charge-transporting structure at the same time as the chain-polymerizable functional group. As the charge-transporting structure, a triarylamine structure is preferable in terms of charge transport. As the chain polymerizable functional group, an acryloyl group and a methacryloyl group are preferred. It may have one or more functional groups. Among them, it is particularly preferable to form a cured film containing a compound having a plurality of functional groups and a compound having a single functional group, because the distortion caused by the polymerization of the plurality of functional groups is easily eliminated.

Examples of compounds having one functional group are shown in (2-1) to (2-6).

Examples of the compounds having multiple functional groups are shown in (3-1) to (3-7).

The protective layer may contain additives such as an antioxidant, an ultraviolet absorber, a plasticizer, a leveling agent, a lubricating agent, and an abrasion resistance improver. Specifically, 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, boron nitride particles. etc.

The protective layer can be formed by preparing a protective layer coating solution containing each of the materials and solvents described above, forming a coating film, and drying and/or curing the coating film. Solvents used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, sulfoxide solvents, ester solvents, and aromatic hydrocarbon solvents.
When the protective layer serves as the surface layer, the particles of the present invention are contained on the surface of the protective layer.
Further, the ratio of the volume of the particles to the total volume of the protective layer is preferably 20% to 80% by volume. Furthermore, 25% to 75% by volume is more preferable, and 35% to 70% by volume is even more preferable.

<Conductive layer>
In the electrophotographic photoreceptor of the present invention, a conductive layer may be provided on the support. By providing the conductive layer, it is possible to cover scratches and irregularities on the surface of the support and to control reflection of light on the surface of the support. The conductive layer preferably contains conductive particles and a resin. Materials for the conductive particles include metal oxides, metals, and carbon black.

Metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Metals include aluminum, nickel, iron, nichrome, copper, zinc, silver and the like.
Among these, metal oxides are preferably used as the conductive particles, and titanium oxide, tin oxide, and zinc oxide are particularly preferably used.

When a metal oxide is used as the conductive particles, the surface of the metal oxide may be treated with a silane coupling agent or the like, or the metal oxide may be doped with an element such as phosphorus or aluminum or an oxide thereof.
Also, the conductive particles may have a laminated structure including core particles and a coating layer that covers the particles. Examples of core material particles include titanium oxide, barium sulfate, and zinc oxide. Metal oxides, such as tin oxide, are mentioned as a coating layer.
When metal oxides are used as the conductive particles, the volume average particle diameter is preferably 1 nm or more and 500 nm or less, more preferably 3 nm or more and 400 nm or less.

Examples of resins include polyester resins, polycarbonate resins, polyvinyl acetal resins, acrylic resins, silicone resins, epoxy resins, melamine resins, polyurethane resins, phenol resins, and alkyd resins.
In addition, the conductive layer may further contain silicone oil, resin particles, masking agents such as titanium oxide, and the like.

The average film thickness of the conductive layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less. The conductive layer can be formed by preparing a conductive layer coating liquid containing each of the above materials and a solvent, forming a coating film thereon, and drying the coating film. Solvents used in the coating liquid include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents and the like. Examples of the dispersion method for dispersing the conductive particles in the conductive layer coating liquid include methods using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

<Undercoat layer>
In the electrophotographic photoreceptor of the present invention, an undercoat layer may be provided on the support or the conductive layer. By providing the undercoat layer, the adhesion function between the layers is enhanced, and the charge injection blocking function can be imparted.
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 a polymerizable functional group.

Examples of resins include polyester resins, polycarbonate resins, polyvinyl acetal resins, acrylic resins, epoxy resins, melamine resins, polyurethane resins, phenol resins, polyvinyl phenol resins, alkyd resins, polyvinyl alcohol resins, polyethylene oxide resins, polypropylene oxide resins, and polyamide resins. , polyamic acid resins, polyimide resins, polyamideimide resins, cellulose resins, and the like.

The polymerizable functional group possessed by the monomer having a polymerizable functional group includes an isocyanate group, a blocked isocyanate group, a methylol group, an alkylated methylol group, an epoxy group, a metal alkoxide group, a hydroxyl group, an amino group, a carboxyl group, a thiol group, Carboxylic anhydride groups, carbon-carbon double bond groups, and the like.

Moreover, the undercoat layer may further contain an electron transporting substance, a metal oxide, a metal, a conductive polymer, or the like for the purpose of enhancing electrical properties. Among these, electron transport substances and metal oxides are preferably used.
Examples of electron-transporting substances include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, halogenated aryl compounds, silole compounds, and boron-containing compounds. . An electron transporting substance having a polymerizable functional group may be used as the electron transporting substance, and an undercoat layer may be formed as a cured film by copolymerizing the electron transporting substance with the above-mentioned monomer having a polymerizable functional group.
Metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide. Metals include gold, silver, and aluminum.

In addition, the undercoat layer may further contain additives. The average thickness of the undercoat layer is preferably from 0.1 μm to 50 μm, more preferably from 0.2 μm to 40 μm, and particularly preferably from 0.3 μm to 30 μm.

The undercoat layer can be formed by preparing an undercoat layer coating solution containing each of the above materials and a solvent, forming a coating film, and drying and/or curing the coating film. Solvents used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents and the like.

[Process cartridge, electrophotographic device]
The electrophotographic photoreceptor described so far can be provided in a process cartridge integrally supporting at least one process selected from the group consisting of a charging process, a developing process, and a transfer process. The process cartridge is detachable from the main body of the electrophotographic apparatus.

FIG. 5 shows an example of the schematic configuration of an electrophotographic apparatus having a process cartridge provided with the electrophotographic photoreceptor of the present invention.

[Structure of Electrophotographic Apparatus]
The electrophotographic apparatus of this embodiment is a so-called tandem type electrophotographic apparatus provided with a plurality of image forming units a to d. The first image forming unit a is yellow (Y), the second image forming unit b is magenta (M), the third image forming unit c is cyan (C), and the fourth image forming unit d is black (Bk ) are used to form an image. These four image forming units are arranged in a row at regular intervals, and most of the configurations of the image forming units are substantially common except for the color of the toner to be accommodated. Therefore, the electrophotographic apparatus of this embodiment will be described below using the first image forming section a.

The first image forming section a has a photosensitive drum 1a that is a drum-shaped photosensitive member, a charging roller 2a that is a charging member, developing means 4a, and drum cleaning means 5a.
The photosensitive drum 1a is an image carrier that carries a toner image, and is rotationally driven at a predetermined peripheral speed (process speed) in the direction indicated by an arrow R1. The developing means 4a accommodates yellow toner and develops the yellow toner on the photosensitive drum 1a. The drum cleaning unit 5a is a unit for collecting toner adhering to the photosensitive drum 1a. The drum cleaning unit 5a has a cleaning blade that contacts the photosensitive drum 1a, and a waste toner box that stores toner removed from the photosensitive drum 1a by the cleaning blade.

When control means (not shown) such as a controller receives an image signal, an image forming operation is started, and the photosensitive drum 1a is rotationally driven. The photosensitive drum 1a is uniformly charged to a predetermined voltage (charging voltage) with a predetermined polarity (negative polarity in this embodiment) by the charging roller 2a during the rotation process, and exposed according to an image signal by the exposing means 3a. be. As a result, an electrostatic latent image corresponding to the yellow component image of the desired 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 accommodated in the developing means 4a is negative, and the electrostatic latent image is reversely developed with the toner charged to 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 the present invention can also be applied to an electrophotographic apparatus that positively develops an electrostatic latent image with a toner charged in a polarity opposite to that of the photosensitive drum 1a.

An endless movable intermediate transfer belt 10 is electrically conductive, forms a primary transfer portion N1a in contact with the photosensitive drum 1a, and rotates at substantially the same peripheral speed as the photosensitive drum 1a. The intermediate transfer belt 10 is stretched by a facing roller 13 as a facing member, a drive roller 11 and a tension roller 12 as tension members, and a metal roller 14a. It is stretched with The intermediate transfer belt 10 can be moved by rotationally driving the drive roller 11 in the illustrated arrow R2 direction. Further, each metal roller 14 and the opposing roller 13 are grounded via a Zener diode 15 as a constant voltage element.

The yellow toner image formed on the photosensitive drum 1a is primarily transferred from the photosensitive drum 1a onto the intermediate transfer belt 10 while passing through the primary transfer portion N1a. After the primary transfer residual toner remaining on the surface of the photosensitive drum 1a is cleaned and removed by the drum cleaning means 5a, it is subjected to the image forming process including charging.

During primary transfer, current is supplied to the conductive intermediate transfer belt 10 from a secondary transfer roller 20 as a secondary transfer member that contacts the outer peripheral surface of the intermediate transfer belt 10 . A current supplied from the secondary transfer roller 20 flows in the circumferential direction of the intermediate transfer belt 10 , whereby the toner image is primarily transferred from the photosensitive drum 1 a 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 .

Subsequently, a magenta toner image of the second color, a cyan toner image of the third color, and a black toner image of the fourth color are formed in the same manner, and transferred onto the intermediate transfer belt 10 in order. As a result, a four-color toner image corresponding to the desired color image is formed on the intermediate transfer belt 10 . After that, the four-color toner image carried on the intermediate transfer belt 10 is fed by the paper feeding means 50 in the process of passing through the secondary transfer portion N2 formed by the contact between the secondary transfer roller 20 and the intermediate transfer belt 10. The images are secondarily transferred collectively onto the surface of a transfer material P such as a fed paper or an OHP sheet. The transfer material P onto which the four-color toner image has been transferred by secondary transfer is then heated and pressurized by the fixing means 30 so that the four-color toners are melted and mixed and fixed onto the transfer material P. FIG. Toner remaining on the intermediate transfer belt 10 after the secondary transfer is cleaned and removed by belt cleaning means 16 provided facing the opposing roller 13 via the intermediate transfer belt 10 . Further, there is provided a path that does not pass through the secondary transfer roller 20 and that electrically connects the transfer power supply 21 and each metal roller 14 through a constant current diode 22 as a constant current element. When a voltage is applied from the transfer power source 21 to the secondary transfer roller 20, a pinch-off current Id flows through the constant current diode 22 in addition to the current It2 flowing toward the secondary transfer portion N2.

The electrophotographic photoreceptor of the present invention can be used in laser beam printers, LED printers, copiers and the like.

[Evaluation method for electrophotographic photoreceptor]
An evaluation method in the present invention will be described.

<Method for Measuring Exposed Volume and Number of Exposed Particles in Surface Layer of Photoreceptor>
The electrophotographic photoreceptor of the present invention is cut into 5 mm squares at 12 points in total, 50 mm from each end in the longitudinal direction, 3 points at the center, and 4 points at 90 degrees in the circumferential direction, to obtain samples. . The photosensitive layer of the sample is coated with platinum for 30 seconds using an evaporator.
In FIB-SEM (NVision 40, manufactured by Carl Zeiss), each sample is cut as follows.
Beam type: Gallium ion beam Accelerating voltage: 1 kV
Size: length 3 μm, width 3 μm, depth 3 μm
Processing step length: 10 nm
Number of steps: 300 Further, SEM observation is performed in a field of view of 30,000 times with an acceleration voltage of 5 kV and a focal length WD of 5 mm for each step.
All the images taken by the FIB-SEM are converted into three-dimensional images by image processing analysis software (“Exfact VR2.1”, manufactured by Nippon Visual Science Co., Ltd.) via an interface. The number of particles exposed from the surface layer of the photoreceptor is measured from the three-dimensional image, and the ratio of the number of exposed particles to the total number of particles contained in the surface layer is calculated.

Furthermore, the derived three-dimensional image and the image of the particle exposed from the surface layer cut by FIB-SEM are compared, and the cross-sectional image of the particle cut at the center of gravity is processed by an image processing analysis device ("LUZEX AP", manufactured by Nireco Co., Ltd.), and the particles in the cross-sectional image are binarized. As shown in the conceptual diagram of FIG. was approximated to a spherical particle of a virtual true sphere. The center of gravity of the cross section of the particles exposed from the surface layer coincides with the center of gravity of the spherical particles of the virtual perfect sphere. For the particles exposed from the surface layer of the photoreceptor, the surface layer 602 where the resin portion is exposed is almost free from undulations, and the calculation is performed by approximating it as a smooth surface. The depth of the portion where the particles contained in the surface layer of the electrophotographic photosensitive member of the present invention were embedded from the surface layer 602 of the resin portion was defined as h.
Further, the virtual true sphere was approximated to a circle having the radius C of the particle when the bottom surface of the portion exposed from the surface layer 602 of the resin portion was viewed from above. (The conceptual diagram is shown in Fig. 6.)
The volume V of the exposed portion of the particle is calculated by the following formula (B).
V=4πR ³ /3−πh(3C ² +h ² )/6 Formula (B)
The volume of the portion exposed to the particles in the three-dimensional image is measured, the sum of the volumes of the exposed portions of the particles partially exposed from the surface layer is calculated, and the sum is The ratio of the volume of the exposed portion of the grain that is partially exposed from the surface layer is calculated by dividing by the total volume of the grain.

<Method for Measuring Volume Average Particle Diameter of Particles of the Present Invention>
The volume average particle diameter is measured using a Zetasizer Nano-ZS (manufactured by MALVERN). The device can measure particle size by dynamic light scattering. First, the sample to be measured is diluted and adjusted so that the solid-liquid ratio is 0.10% by mass (±0.02% by mass), collected in a quartz cell, and placed in the measurement unit. As the dispersion medium, water or a mixed solvent of methyl ethyl ketone/methanol is used when the sample is inorganic fine particles, and water is used when the sample is resin particles or an external additive for toner. As the measurement conditions, the refractive index of the sample, the refractive index of the dispersion solvent, the viscosity and the temperature are input and measured using the control software Zetasizersoftware 6.30. Dn is adopted as the number average particle size.

The refractive index of the particles is adopted from "Refractive index of solids" described in Kagaku Binran, Basic Edition, Revised 4th Edition (Edited by The Chemical Society of Japan, Maruzen Co., Ltd.), Vol. II, p.517. As for the refractive index of the resin particles, the refractive index of the resin used for the resin particles, which is incorporated in the control software, is adopted. However, if there is no built-in refractive index, use the value described in the polymer database of the National Institute for Materials Science. The refractive index of the external additive for toner is calculated by taking the weight average from the refractive index of the inorganic fine particles and the refractive index of the resin used for the resin particles. For the refractive index, viscosity and temperature of the dispersion solvent, the numerical values built into the control software are selected. In the case of a mixed solvent, the weight average of the mixed dispersion medium is taken.

<Method for Measuring Particle Coverage and Variation Coefficient in Surface Layer of Photoreceptor>
In the electrophotographic photoreceptor of the present invention, S1/(S1+S2) can be calculated as follows, where S1 is the total area of the exposed portions of the particles when the surface layer is viewed from above.
For the particles of the surface layer, a 30,000-fold photographic image of the surface layer of the photoreceptor taken with a scanning electron microscope (SEM) ("S-4800", manufactured by JEOL Ltd.) is captured by a scanner, and image processing analysis is performed. A device ("LUZEX AP", manufactured by Nireco Corporation) is used to binarize the grains of the photographic image. The coverage ratio S1/(S1+S2) (%) is calculated, where S1 is the area of the exposed portion of the grain on the photoreceptor in one field of view, and S2 is the total area of the portion other than the exposed portion of the grain. The above coverage is calculated for a total of 10 fields of view, and the average value of the obtained coverage is taken as the coverage of the particles in the surface layer of the photoreceptor.

<Method for Measuring Circularity of Exposed Particles in Surface Layer of Photoreceptor>
For the particles of the surface layer, a photographic image of the surface layer of the photoreceptor taken with a scanning electron microscope (SEM) ("S-4800", manufactured by JEOL Ltd.) at a magnification of 30,000 times is captured by a scanner. Image analysis is performed using image processing software (Image J (available from https://imagej.nih.gov/ij/)), and the grains of the photographic image are binarized. The electrophotographic photoreceptor of the present invention is cut into 5 mm squares at 12 points in total, 50 mm from each end in the longitudinal direction, 3 points at the center, and 4 points at 90 degrees in the circumferential direction, to obtain samples. . The central portion of the sample is regarded as one field of view, and the circularity of all the particles in one field of view is calculated.

<Method for measuring unevenness of exposed particles in surface layer of photoreceptor>
On the other hand, the shape factor of exposed grains in the surface layer of the photoreceptor is obtained by sampling 100 grain images magnified 30,000 times at random using, for example, Hitachi FE-SEM (S-4800). Via the interface, the image information is taken into an image processing analysis device ("LUZEX AP", manufactured by Nireco Co., Ltd.), binarized and analyzed, and the value obtained by calculating from the following formula C is the shape factor Define SF-2.
(SF-2)=(PER)2/(AREA)×1/(4π)×100 (C)
(In the formula, PER indicates the perimeter of the particle, and AREA indicates the projected area of the particle.)
The shape factor SF-2 indicates the degree of fine unevenness on the particle surface.
On the other hand, if SF-2 exceeds 135, the transfer efficiency of the toner image from the photoreceptor to the intermediate transfer member and the transfer material is lowered, and the transfer failure of characters and line images is unfavorably caused.

<Method for Measuring Young's Modulus of Exposed Particles in Surface Layer of Photoreceptor>
As an evaluation machine, an SPM probe station (“NanoNaviReal” manufactured by Hitachi High-Tech Science Co., Ltd.) equipped with a scanning probe microscope (“S-image” manufactured by Hitachi High-Tech Science Co., Ltd.) with a built-in heater was used. Prior to the measurement, the evaluator was calibrated using PMMA (polymethyl methacrylate) particles as a standard material under the conditions of the allowable range of 2.920±0.119 GPa (Young's modulus). The Young's modulus of PMMA measured by the calibrated evaluator was 3.01 GPa.
The particles of the surface layer of the electrophotographic photosensitive member were measured by SPM, and the average value of ten measurement results for one particle was taken as the Young's modulus of one particle. Furthermore, the average value of the Young's moduli of ten particles was taken as the Young's modulus of the exposed particles in the surface layer of the photoreceptor in the present invention.

EXAMPLES The present invention will be described in more detail below using examples and comparative examples. The present invention is by no means limited by the following examples, as long as the gist thereof is not exceeded. In the description of the following examples, "parts" are based on mass unless otherwise specified. The film thickness of each layer of the electrophotographic photoreceptor of Examples and Comparative Examples was determined by an eddy current film thickness meter (Fischerscope, manufactured by Fischer Instruments), or determined by converting the mass per unit area into specific gravity. rice field.

Table 1 shows the type of particles contained in the surface layer of the electrophotographic photosensitive member of the present invention, the manufacturer, the number average particle size, the volume average particle size, and (volume average particle size)/(number average particle size).

(Production of surface-treated particles 1)
10 parts by mass of methanol and 5 parts by mass of particles 1 (listed in Table 1) were added and dispersed at room temperature for 30 minutes using a US homogenizer. Next, 0.25 parts by mass of n-propyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) and 10 parts by mass of toluene, which are reactive surface treatment agents, were added and stirred at room temperature for 60 minutes. After removing the solvent with an evaporator, the mixture was heated at 140° C. for 60 minutes to prepare surface-treated particles 1 surface-treated with a reactive surface-treating agent. The volume average particle diameter was 136 nm, and the number average particle diameter was 124 nm.

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

(Preparation Example of Coating Liquid 1 for Conductive Layer)
・Anatase titanium dioxide (average primary particle size: 150 nm, niobium content: 0.20 wt%) 100 parts by mass Dispersed in 1000 parts by mass of pure water to form a 1 L water suspension and heated to 60°C.
A niobium solution of 3 parts by mass of niobium pentachloride (NbCl ₅ ) dissolved in 100 mL of 11.4 mol/L hydrochloric acid and 600 mL of a titanium sulfate solution containing 33.7 parts by mass of Ti were mixed with a titanium niobate solution of 10.7 mol. /L sodium hydroxide solution was simultaneously added dropwise over 3 hours so that the pH of the suspension was 2-3. After completion of dropping, the suspension was filtered, washed and dried at 110° C. for 8 hours.
The dried product is subjected to heat treatment at 800° C. for 1 hour in an air atmosphere, and the metal oxide particles have a core material containing titanium oxide and a coating layer containing titanium oxide doped with niobium. 1 powder was obtained.
Phenol resin (trade name: Pryofen J-325, manufactured by DIC, resin solid content: 60%, density after curing: 1.3 g/cm ² ) 50 parts by mass 1-methoxy-2-propanol 35 parts by mass parts, 75 parts by mass of metal oxide particles 1, and 120 parts by mass of glass beads (average particle size: 1.0 mm) were mixed, placed in a vertical sand mill, and dispersed at a dispersion temperature of 23 ± 3 ° C. and a rotation speed of 1,500 rpm (peripheral speed of 5.0 mm). 5 m/s) for 4 hours to obtain a metal oxide particle dispersion liquid 1. Remove the glass beads from the metal oxide particle dispersion liquid 1 with a mesh,
・ Silicone oil (trade name: SH28 PAINT ADDITIVE, manufactured by Dow Corning Toray) 0.01 part by mass ・ Silicone resin particles (trade name: Tospearl 120, manufactured by Momentive Performance Materials, average particle size: 2 μm, density: 1 .3 g/cm ² ) 10 parts by mass were added, stirred, and filtered under pressure using PTFE filter paper (trade name: PF060, manufactured by Advantec Toyo Co., Ltd.) to prepare a conductive layer coating liquid 1.

(Production example of conductive layer 1)
The conductive layer coating solution 1 was dip-coated on the support and heated at 140° C. for 1 hour to form a conductive layer 1 having a thickness of 20 μm.

(Preparation Example of Coating Liquid 1 for Undercoat Layer)
・ Rutile-type titanium oxide particles (average primary particle size: 50 nm, manufactured by Tayca) 100 parts by mass ・ Phenolic resin (trade name: Pryofen J-325, manufactured by Dainippon Ink and Chemicals, Inc., resin solid content: 60% by mass ) 132 parts by mass, 500 parts by mass of toluene, 5 parts by mass of vinyltrimethoxysilane (trade name: KBM-1003, manufactured by Shin-Etsu Chemical Co., Ltd.), and 450 parts by mass of glass beads (diameter 0.8 mm) were mixed and stirred for 8 hours. After that, toluene was distilled off under reduced pressure and dried at 120° C. for 3 hours to obtain rutile-type titanium oxide particles 1 surface-treated with vinyltrimethoxysilane.
・Surface-treated rutile-type titanium oxide particles 18 parts by mass ・N-Methoxymethylated nylon (trade name: Toresin EF-30T, manufactured by Nagase ChemteX) 4.5 parts by mass ・Copolymerized nylon resin (trade name: Amilan CM8000 , manufactured by Toray) 1.5 parts by mass, 90 parts by mass of methanol, 60 parts by mass of 1-butanol, 15 parts by mass of acetone, and 120 parts by mass of glass beads (average particle size: 1.0 mm). A coating liquid 1 for undercoat layer was prepared by time dispersion treatment.

(Example of preparation of undercoat layer 1)
The undercoat layer coating liquid 1 was dip-coated on the conductive layer 1 and heated at 170° C. for 30 minutes to form an undercoat layer 1 having a thickness of 1.0 μm.

(Preparation example 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 (trade name: S-Lec BX-1, Sekisui Chemical manufactured by Kogyosha)
5 parts by mass, 200 parts by mass of cyclohexanone and 200 parts by mass of glass beads were dispersed in a sand mill for 6 hours. 150 parts by mass of cyclohexanone and 350 parts by mass of ethyl acetate were further added to dilute the mixture to obtain a coating liquid 1 for charge generation layer. The resulting charge generation layer coating solution 1 was dip-coated on the undercoat layer 1 and dried at 95° C. for 10 minutes to form a charge generation layer 1 having a thickness of 0.20 μm.

(Preparation example of charge transport layer 1)
Next, the following materials were prepared.
・Charge-transporting substance (hole-transporting substance) represented by the above structural formula (1-1) 5 parts by mass ・Charge-transporting substance (hole-transporting substance) represented by the above structural formula (1-3) 5 parts by mass・ Polycarbonate (trade name: Iupilon Z400, manufactured by Mitsubishi Engineering-Plastics Co., Ltd.) 10 parts by mass ・ Polycarbonate resin 0.02 having a copolymer unit of the following structural formula (C-1) and the following structural formula (C-2) Part (x/y = 0.95/0.05: viscosity average molecular weight = 20000)
By dissolving these in a mixed solvent of 60 parts by mass of toluene/3 parts by mass of methyl benzoate/15 parts by mass of tetrahydrofuran, coating liquid 1 for charge transport layer was prepared. The charge transport layer coating liquid 1 was dip-coated on the charge generation layer 1 to form a coating film, and the coating film was dried at a drying temperature of 40° C. for 5 minutes to form a charge transport layer 1 having a thickness of 15 μm. formed.

(Preparation Example 1 of Surface Layer Containing Particles)
Next, the following materials were prepared.
・ Particle 1 (listed in Table 1) 1.2 parts by mass ・ Siloxane-modified acrylic compound (trade name: Cymac US270, manufactured by Toagosei Co., Ltd.)
0.1 part by mass, 30 parts by mass of cyclohexane and 70 parts by mass of 1-propanol were mixed and stirred to prepare a surface layer coating liquid 1.
This surface layer coating liquid was dip-coated on the charge transport layer 1 to form a coating film, and the resulting coating film was dried at 100° C. for 20 minutes to obtain an electrophotographic photoreceptor 1 . Film thickness [μm] of charge transport layer of electrophotographic photosensitive member 1, volume average particle size [nm] of particles contained in surface layer, number ratio of particles exposed from surface layer [number %], exposed from surface layer Volume ratio [number %] of particles exposed from the surface layer, coverage S1 / (S1 + S2) and coefficient of variation of particles exposed from the surface layer, average circularity and SF-2 of the shape of the exposed portion of the particles exposed from the surface layer, surface layer Young's modulus [GPa] of the surface of the particles exposed from the surface, volume average particle size / number average particle size of the particles, ash content [mass%] at the time of sintering of the insoluble part of the surface layer in methyl ethyl ketone, particles contained in the surface layer The content [% by volume] of was measured. Table 3 shows the results.

<Production Examples 2 to 36 of Electrophotographic Photoreceptors>
In the manufacturing example of the electrophotographic photoreceptor 1, the coating liquid 1 for the charge transport layer in the manufacturing example of the charge transport layer 1 is dip-coated on the charge generation layer 1 to form a coating film, and the temperature at which the coating film is dried and the content in the surface layer Electrophotographic photoreceptors 2 to 36 were produced in the same manner as electrophotographic photoreceptor 1, except that the type and amount of particles added and the amounts of cyclohexane and 1-propanol added were changed as shown in Table 2. Physical properties of electrophotographic photoreceptors 2 to 36 were measured. Table 3 shows the results.

<Manufacturing Example of Electrophotographic Photoreceptor 37>
In the manufacturing example of the electrophotographic photoreceptor 1, the charge transport layer coating liquid 37 is dip-coated on the charge generation layer 37 to form a coating film, and the coating film is dried at a drying temperature of 120° C. for 5 minutes. , and a charge transport layer 37 having a film thickness of 15 μm.

(Preparation Example 2 of Surface Layer Containing Particles)
Next, the following materials were prepared.
・Particle 1 (listed in Table 1) 1.2 parts by mass ・Charge-transporting substance (hole-transporting substance) represented by the above structural formula (2-1) 0.1 part by mass ・The above structural formula (3-1) Charge-transporting material (hole-transporting material) represented by 0.2 parts by mass Siloxane-modified acrylic compound (trade name: Cymac US270, manufactured by Toagosei Co., Ltd.)
0.1 part by mass, 30 parts by mass of cyclohexane and 70 parts by mass of 1-propanol were mixed and stirred to prepare a surface layer coating liquid 2.
This surface layer coating liquid 2 was dip-coated on the charge transport layer 1 to form a coating film, and the resulting coating film was dried at 40° C. for 5 minutes.
After that, in a nitrogen atmosphere, the coating film was irradiated with an electron beam for 1.6 seconds while rotating the support (object to be irradiated) at a speed of 300 rpm under the conditions of an acceleration voltage of 70 kV and a beam current of 5.0 mA. The dose at the outermost layer position was 15 kGy. After that, in a nitrogen atmosphere, the temperature was raised from 25° C. to 100° C. over 20 seconds to perform first heating to form a surface layer having a thickness of 1.0 μm. The oxygen concentration from the electron beam irradiation to the subsequent heat treatment was 10 ppm or less. Next, the coating film was naturally cooled in the atmosphere until the temperature of the coating film reached 25°C, and a second heat treatment was performed for 20 minutes under the condition that the temperature of the coating film reached 100°C. Thus, an electrophotographic photoreceptor 37 was produced. Film thickness [μm] of charge transport layer of electrophotographic photosensitive member 37, film thickness [μm] of surface layer, volume average particle diameter [nm] of particles contained in surface layer, number ratio of particles exposed from surface layer [number %], volume ratio of particles exposed from the surface layer [number %], coverage by particles exposed from the surface layer S1 / (S1 + S2), average circularity of the shape of the exposed portion of the particles exposed from the surface layer, Young's modulus [GPa] of the surface of the particles exposed from the surface layer, volume average particle size / number average particle size of the particles, ash content [mass%] at the time of sintering of the insoluble portion of the surface layer in methyl ethyl ketone, contained in the surface layer The content [% by volume] of the particles contained was measured. Table 5 shows the results.

<Production Examples 38 to 72 of Electrophotographic Photoreceptors>
In the production example of the electrophotographic photoreceptor 37, the charge transport layer coating liquid 37 in the production example of the charge transport layer 37 is dip-coated on the charge generation layer 37 to form a coating film, and the temperature and particles are included. In the surface layer preparation example 2, an electrophotographic photoreceptor was prepared in the same manner as the electrophotographic photoreceptor 37 except that the type and amount of particles contained in the surface layer and the amount of cyclohexane and 1-propanol added were changed as shown in Table 4. Photoreceptors 38-72 were produced. Each physical property of the electrophotographic photoreceptors 38 to 72 was measured. Table 5 shows the results.

[Production Example of Electrophotographic Photoreceptor 73]
Among the production examples of the electrophotographic photoreceptor 1, the production up to the production example 1 of the undercoat layer was performed in the same manner.

(Formation of single-layer type photosensitive layer)
[Production of photoreceptor]
The following compounds were put into the container.
Charge generation agent Titanyl phthalocyanine 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 (the following formula D) 138 parts by mass Solvent (tetrahydrofuran) 400 parts by mass As a result, a coating liquid 73 for forming a photosensitive layer was obtained. The photosensitive layer forming coating solution 73 was dip-coated on the support and heated at 40° C. for 5 minutes to form a single layer type photosensitive layer 1 having a thickness of 15 μm.

(Preparation Example 3 of Surface Layer Containing Particles)
Next, the following materials were prepared.
・ Particle 1 (listed in Table 1) 1.2 parts by mass ・ Siloxane-modified acrylic compound (trade name: Cymac US270, manufactured by Toagosei Co., Ltd.)
0.1 part by mass, 30 parts by mass of cyclohexane and 70 parts by mass of 1-propanol were mixed and stirred to prepare a surface layer coating liquid 3.
This surface layer coating solution 3 was dip-coated on the single-layer type 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 film thickness of the charge transport layer [μm], the volume average particle diameter of the particles contained in the surface layer [nm], the number ratio of the particles exposed from the surface layer [number %], the volume ratio of the particles exposed from the surface layer [ number %], coverage by particles exposed from the surface layer S1/(S1+S2), average circularity of the shape of the exposed portion of the particles exposed from the surface layer, Young's modulus [GPa] of the surface of the particles exposed from the surface layer, The volume-average particle diameter/number-average particle diameter of the particles, the ash content [mass %] at the time of sintering of the insoluble portion of the surface layer in methyl ethyl ketone, and the content [volume %] of the particles contained in the surface layer were measured. Table 5 shows the results.

<Electrophotographic Photoreceptor Production Examples 74 to 88>
In the manufacturing example of the electrophotographic photoreceptor 1, the coating liquid 1 for the charge transport layer in the manufacturing example of the charge transport layer 1 is dip-coated on the charge generation layer 1 to form a coating film, and the temperature at which the coating film is dried and the content in the surface layer Electrophotographic photoreceptors 74 to 88 were produced in the same manner as electrophotographic photoreceptor 1, except that the type and amount of particles added and the amounts of cyclohexane and 1-propanol added were changed as shown in Table 6. Each physical property of the electrophotographic photoreceptors 74 to 88 was measured. Table 7 shows the results.

<Production Examples 89 to 103 of electrophotographic photoreceptors>
In the production example of the electrophotographic photoreceptor 37, the charge transport layer coating liquid 37 is dip-coated on the charge generation layer 37 to form a coating film, and the temperature at which the coating film is dried is Electrophotographic photoreceptors 89 to 103 were produced in the same manner as electrophotographic photoreceptor 37 except that the types and amounts of particles contained in the surface layer and the amounts of cyclohexane and 1-propanol added were changed as shown in Table 8. did. Physical properties of electrophotographic photoreceptors 89 to 103 were measured. Table 9 shows the results.

<Production Example 104 of Electrophotographic Photoreceptor>
In Production Example of Electrophotographic Photoreceptor 1, an electrophotographic photosensitive member was prepared in the same manner as in Electrophotographic Photoreceptor 1, except that the drying temperature and drying time in Production Example 1 of Charge Transport Layer 1 were changed to 130° C. and 20 minutes, respectively. A body 24 was produced. Each physical property of the electrophotographic photosensitive member 104 was measured. Table 9 shows the results.

<Production Example 105 of Electrophotographic Photoreceptor>
Electrophotographic photoreceptor 105 was prepared in the same manner as electrophotographic photoreceptor 37 except that Particle 1 was not added in (Preparation Example 2 of Surface Layer Containing Particles) in Production Example of Electrophotographic Photoreceptor 37 . was made. Each physical property of the electrophotographic photosensitive member 105 was measured. Table 9 shows the results.

<Production Example 106 of Electrophotographic Photoreceptor>
Electrophotographic photoreceptor 106 was prepared in the same manner as electrophotographic photoreceptor 1 except that Particle 1 was not added in (Preparation Example 3 of Surface Layer Containing Particles) in Production Example of Electrophotographic Photoreceptor 73 . was made. Each physical property of the electrophotographic photosensitive member 106 was measured. Table 9 shows the results.

<Production Example 107 of Electrophotographic Photoreceptor>
Among the manufacturing examples of the electrophotographic photosensitive member 37, the manufacturing examples up to the manufacturing example of the charge transport layer 2 were manufactured in the same manner.

(Production of surface-treated particles 2)
10 parts by mass of methanol and 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.), a reactive surface treatment agent (3-methacryloxypropyl 0.25 parts by mass of trimethoxysilane ("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 with an evaporator, the mixture was heated at 120° C. for 60 minutes to prepare surface-treated particles 2 surface-treated with a reactive surface-treating 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 surface layer coating liquid 107 .
・Radical polymerizable monomer (trimethylolpropane trimethacrylate) 120 parts by mass ・Surface treatment particles 2 100 parts by mass ・Polymerization initiator (manufactured by BASF Japan Ltd., IRGACURE (registered trademark) 819)
10 parts by mass 2-butanol 800 parts by mass Subsequently, the obtained surface layer coating solution 107 was dip-coated on the charge transport layer 2 to form a coating film. cm ² for 1 minute (cumulative amount of light: 960 mJ/cm ² ) to form a surface layer with a dry film thickness of 1.0 μm, thereby producing an electrophotographic photoreceptor 107 . Each physical property of the electrophotographic photosensitive member 107 was measured. Table 9 shows the results.

<Production Example 108 of Electrophotographic Photoreceptor>
100 parts of monochlorobenzene and 10 parts of spherical polymethylsilsesquioxane particles having an average particle size of 4.5 μm, which are organic-inorganic hybrid particles (trade name: Tospearl 145, manufactured by Toshiba Silicone Co., Ltd.), were placed in a paint shaker. A surface layer coating liquid 108 was obtained by time dispersion treatment.
The charge-transporting layer coating liquid 108 was prepared by mixing the charge-transporting layer coating liquid 1 and the surface layer coating liquid 108 in Electrophotographic Photoreceptor Production Example 1 with stirring. The charge transport layer coating liquid 108 was dip-coated on the charge generation layer 1, and the resulting coating film was dried at 120° C. for 1 hour to form a charge transport layer 108 having a thickness of 16 μm. Next, the surface of the charge transport layer 108 was treated with a hydrofluoric acid solution having a concentration of 20 mass % to obtain an electrophotographic photoreceptor 108 having the charge transport layer as the surface layer.
Observation with a scanning electron microscope (SEM) shows that the particles are attached to the charge transport layer before hydrofluoric acid treatment, whereas the particles are attached to the charge transport layer after hydrofluoric acid treatment. There were many gaps with the inner surfaces of the pores of the charge transport layer 108 . Each physical property of the electrophotographic photosensitive member 108 was measured. Table 9 shows the results.

<Production Example of Toner Particle 1>
(Preparation of aqueous medium 1)
650.0 parts of ion-exchanged water and 14.0 parts of sodium phosphate (manufactured by Rasa Kogyo Co., Ltd., dodecahydrate) were added to a reaction vessel equipped with a stirrer, a thermometer, and a reflux tube, and the mixture was purged with nitrogen. The mixture was kept at 65° C. for 1.0 hour.
T. K. Using a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), while stirring at 15000 rpm, a calcium chloride aqueous solution in which 9.2 parts of calcium chloride (dihydrate) is dissolved in 10.0 parts of ion-exchanged water is added all at once. Then, an aqueous medium containing a dispersion stabilizer was prepared. Furthermore, 10% by mass hydrochloric acid was added to the aqueous medium to adjust the pH to 5.0, and an aqueous medium 1 was obtained.

(Preparation of polymerizable monomer composition)
・Styrene: 60.0 parts ・C.I. I. Pigment Blue 15:3: 6.5 parts The above material was placed in an attritor (manufactured by Mitsui Miike Kakoki Co., Ltd.), and further dispersed using zirconia particles with a diameter of 1.7 mm at 220 rpm for 5.0 hours. 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 (Polycondensation of propylene oxide-modified bisphenol A (2 mol 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 This material is added to the above colorant dispersion, heated to 65°C, and then treated with T.I. K. A homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) was used to uniformly dissolve and disperse at 500 rpm to prepare a polymerizable monomer composition.

(Granulation process)
The temperature of the aqueous medium 1 was adjusted to 70°C, and T.I. K. While maintaining the rotation speed of the homomixer at 15000 rpm, the polymerizable monomer composition was charged into the aqueous medium 1, and 10.0 parts of t-butyl peroxypivalate as a polymerization initiator was added. The mixture was granulated as it was for 10 minutes while maintaining 15000 rpm with the stirring device.

(Polymerization step and distillation step)
After the granulation step, the stirrer was changed to a propeller stirring blade, and the mixture was stirred at 150 rpm while maintaining the temperature at 70°C for 5.0 hours to conduct polymerization. did After that, the reflux tube of the reaction vessel is replaced with a cooling tube, and the obtained slurry is heated to 100° C. to perform distillation for 6 hours to distill off the unreacted polymerizable monomer to obtain a resin particle dispersion liquid. got

<Production Example of External Additive 1>
The external additive 1 was manufactured as follows.
150 parts of 5% aqueous ammonia was put into a 1.5 L glass reactor equipped with a stirrer, a dropping nozzle and a thermometer to prepare an alkaline catalyst solution. After the alkali catalyst solution was adjusted to 50° C., 100 parts of tetraethoxysilane and 50 parts of 5% aqueous ammonia were added dropwise at the same time while stirring, and reacted for 8 hours to obtain a fine silica particle dispersion. After that, the obtained silica fine particle dispersion was dried by spray drying and pulverized by a pin mill to obtain silica fine particles. Here, external additives 1 having different number average particle diameters R of primary particles were obtained by appropriately changing the above production conditions.

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

<Production Example of Toner 2>
・Polymerizable monomer: 74 parts of styrene, 26 parts of n-butyl acrylate ・Colorant: 7 parts of carbon black (trade name: #25B, manufactured by Mitsubishi Chemical) ・Crosslinking agent: 0.74 parts of divinylbenzene ・Charge control agent : Styrene/acrylic resin (trade name: FCA-592P, manufactured by Fujikura Kasei Co., Ltd.) 0.37 parts Molecular weight modifier: Tetraethylthiuram disulfide 1 part Macromonomer: Polymethacrylate macromonomer (trade name: AA6, Toa Gosei Kagaku Kogyo Co., Ltd., glass transition temperature Tg = 94°C) 0.25 part After stirring and mixing the above materials with an ordinary stirrer, they were uniformly dispersed and heated to 63°C with a media-type disperser.
Here, 20 parts of wax A-1 was added to the uniformly dispersed material, mixed and dissolved to obtain a polymerizable monomer composition.
Separately, in a stirring tank, an aqueous solution of 7.4 parts of magnesium chloride dissolved in 250 parts of ion-exchanged water and an aqueous solution of 4.1 parts of sodium hydroxide dissolved in 50 parts of ion-exchanged water were stirred at room temperature. It was gradually added to prepare a magnesium hydroxide colloidal dispersion (3.0 parts of magnesium hydroxide).
The polymerizable monomer composition was added to the magnesium hydroxide colloidal dispersion obtained above at room temperature, the temperature was raised to 60° C., and the mixture was stirred until the droplets were stabilized. 5 parts of t-butylperoxy-2-ethylhexanoate (trade name: Perbutyl O, manufactured by NOF CORPORATION) was added thereto as a polymerization initiator. Thereafter, an in-line emulsifying disperser (trade name: Milder, manufactured by Taiheiyo Kiko Co., Ltd.) was used to form droplets of the polymerizable monomer composition by high shear stirring at a rotation speed of 15,000 rpm.
The magnesium hydroxide colloidal dispersion in which the droplets of the polymerizable monomer composition are dispersed is charged into a reactor equipped with a stirring blade, and the temperature is raised to 89° C. and the temperature is controlled to be constant. , the polymerization reaction was carried out. Next, when the polymerization conversion rate reached 98%, the temperature in the system was cooled to 75°C, and 15 minutes after reaching 75°C, 3 parts of methyl methacrylate as a polymerizable monomer for the shell and ion exchange 2,2′-azobis[2-methyl-N-(1,1-bis(hydroxymethyl)2-hydroxyethyl)propionamide]tetrahydrate dissolved in 10 parts of water (trade name: VA086, Wako Pure Chemical Industries, Ltd.) product) was added. After continuing the polymerization for an additional 3 hours, the reaction was terminated to obtain an aqueous dispersion of colored resin particles having a pH of 9.5.
After that, the aqueous dispersion of the colored resin particles was heated to 80°C, stripped for 5 hours at a nitrogen gas flow rate of 0.6 m3/(hr·kg), and then cooled to 25°C. Next, while stirring the resulting aqueous dispersion at 25° C., the pH of the system is adjusted to 6.5 or less with sulfuric acid for acid washing. was added to reslurry and washed with water. Thereafter, dehydration and washing with water were repeated several times, and the solid content was separated by filtration.
To 100 parts of the toner particles obtained above, 0.7 parts of hydrophobized silica fine particles having a number average primary particle size of 7 nm and 1 part of hydrophobized silica fine particles having a number average primary particle size of 50 nm are added, Toner 2 was produced by mixing using a high-speed stirrer (trade name: FM Mixer, manufactured by Nippon Coke Kogyo Co., Ltd.).

[Example 1]
Using electrophotographic photoreceptor 1 and toner 1, the following evaluations were made. Table 10 shows the evaluation results.

<Evaluation method>
<Evaluation of transferability>
A commercially available Canon laser beam printer LBP7700C modified was used. As for the modified point, the rotation speed of the developing roller was set to 360 mm/sec by changing the main body of the evaluation machine and the software.
Toner was loaded into the toner cartridge of the evaluation machine LBP7700C, and the toner cartridge was left for 24 hours under normal temperature and normal humidity (25° C., 50% RH; hereinafter also referred to as N/N). After leaving the toner cartridge for 24 hours in the environment, attach the toner cartridge to the above, leave 50 mm left and right margins in the N/N environment, and print up to 500 sheets of A4 paper in the horizontal direction with a print rate of 5.0% in the center. printed out. Plain paper CS-680 (68 g/m ² ) (Canon Marketing Japan Inc.) was used as the paper.
The evaluation was carried out by outputting a solid image at the initial stage of use (after printing the first sheet) and after printing 500 sheets (after long-term use). was taped and stripped using
The difference in density was calculated by subtracting the density of the adhesive tape alone pasted on paper from the density of the stripped adhesive tape pasted on paper. Density measurements were performed at 5 points, and the arithmetic mean value was obtained. Then, from the value of the density difference (referred to as the residual density after transfer), determination was made as follows. The density was measured with an X-Rite color reflection densitometer (manufactured by X-rite, X-rite 500 Series).
(Evaluation criteria)
A: Residual transfer density is less than 0.20 B: Residual transfer density is 0.20 or more and less than 0.50 C: Residual transfer density is 0.50 or more and less than 1.0 D: Residual transfer density is 1.0 or more

<Rough evaluation>
After outputting 10,000 sheets of character images with a print ratio of 1% in a remodeled machine under an environment of 30° C. and 80% RH, a halftone (20H) image is formed. was evaluated based on the criteria of Plain paper CS-680 (68 g/m ² ) (Canon Marketing Japan Inc.) was used as the paper. The 20H image is a value obtained by expressing 256 gradations in hexadecimal, and is a halftone image in which 00H is solid white (non-image) and FFH is solid black (full-surface image).
Roughness was evaluated according to the following criteria. Density was measured at 20 points, and the difference in density between the maximum value and the minimum value (which is referred to as density uniformity) was evaluated as follows. The density was measured with an X-Rite color reflection densitometer (manufactured by X-rite, X-rite 500 Series).
(Evaluation criteria)
A: Density uniformity of less than 0.04 B: Density uniformity of 0.04 to less than 0.06 C: Density uniformity of 0.06 to less than 0.08 D: Density uniformity of 0.06 to less than 0.08 08 or more

<Evaluation of Change in Durability Concentration>
The modified machine was placed in an environment of 30° C. and 80% RH, and the change in concentration in the endurance test was evaluated. An original image in which five 20 mm square solid black patches were arranged in the development area was output, and the development bias was set so that the initial reflection density was 1.3. Next, 10,000 sheets of character images with a print ratio of 1% were output. Plain paper CS-680 (68 g/m ² ) (Canon Marketing Japan Inc.) was used as the paper. Durability was evaluated by comparing the density difference between the image density after the durability test and the density of the initial image with respect to the 5-point average density of the solid black patch.
The image density was measured relative to the white background portion of the original image using a "Macbeth reflection densitometer RD918" (manufactured by Macbeth).
(Evaluation criteria)
A: Density difference less than 0.10 B: Density difference 0.10 to less than 0.15 C: Density difference 0.15 to less than 0.20 D: Density difference 0.20 or more

[Examples 2 to 72]
A combination of the electrophotographic photoreceptor and toner as shown in Table 4 was evaluated by the same evaluation method as in Example 1. Table 10 shows the evaluation results.

[Comparative Examples 1 to 32, 34, and 35]
A combination of the electrophotographic photoreceptor and toner as shown in Table 4 was evaluated by the same evaluation method as in Example 1. Table 10 shows the evaluation results.

[Example 73]
Using the electrophotographic photoreceptor 73 and the toner 2, evaluation was performed in the same manner as in Example 1 using the following electrophotographic apparatus. Table 10 shows the evaluation results.
As an electrophotographic apparatus, a monochrome laser printer HL-5200 manufactured by Brother was modified. A high-voltage power supply control system (trade name: Model 615-3, manufactured by Trek) was used as a power supply for supplying electric power for the corona charger from the outside of the printer. Then, the amount of current flowing through the corona wire of the corona charger was adjusted to 500 μA.
The toner in the toner cartridge for this printer was removed, and toner 2 was filled instead. Also, the electrophotographic photoreceptor was removed from the drum unit, and an electrophotographic photoreceptor 73 whose initial film thickness was measured for durability evaluation was set instead.

[Comparative Example 33]
Using the electrophotographic photoreceptor 106 and toner 2, the same evaluation method as in Example 73 was used for evaluation. Table 10 shows the evaluation results.

The disclosure of this embodiment includes the following configurations.
[Configuration 1]
An electrophotographic photoreceptor having a support and a photosensitive layer on the support,
the surface layer of the electrophotographic photoreceptor contains particles,
The surface layer has particles partially exposed from the surface layer in the particles contained in the surface layer,
The volume average particle size of the particles 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,
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 with respect to the total volume of the particles contained in the surface layer. and an electrophotographic photoreceptor.
[Configuration 2]
The electrophotographic photoreceptor according to Structure 1, wherein the photosensitive layer has a charge generation layer and a charge transport layer on the charge generation layer, and the charge transport layer is the surface layer.
[Configuration 3]
The photosensitive layer has a charge generation layer and a charge transport layer on the charge generation layer, the electrophotographic photoreceptor further has a protective layer on the photosensitive layer, and the protective layer is the surface layer. The electrophotographic photoreceptor according to Structure 1.
[Configuration 4]
Electrophotography according to Structure 1, wherein the photosensitive layer is a single-layer type photosensitive layer, the electrophotographic photoreceptor further has a protective layer on the photosensitive layer, and the protective layer is the surface layer. photoreceptor.
[Configuration 5]
When the surface layer is viewed from above, the total area of the exposed portions of the grains partially exposed from the surface layer is S1, and the grains other than the exposed portions of the grains partially exposed from the surface layer are defined as S1. The electrophotographic photoreceptor according to any one of Structures 1 to 4, wherein S1/(S1+S2) satisfies the following formula (A), where S2 is the total area of .
0.15≦S1/(S1+S2)≦0.80 Formula (A)
[Configuration 6]
When the surface layer is viewed from above, the total area of the exposed portions of the particles is S1, and the total area of the particles other than the exposed portions is S2, the coefficient of variation of S1/(S1+S2) is 25%. The electrophotographic photoreceptor according to Structure 5 below.
[Configuration 7]
7. The electrophotographic photoreceptor according to any one of Structures 1 to 6, wherein SF-2 of the shape of the exposed portions of the particles is 135 or less when the surface layer is viewed from above.
[Configuration 8]
The electrophotographic photoreceptor according to any one of Structures 1 to 7, wherein 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.
[Configuration 9]
The electrophotographic photoreceptor according to any one of Structures 1 to 8, wherein the Young's modulus of the particles is 0.60 GPa or more.
[Configuration 10]
The electrophotographic photoreceptor according to any one of Structures 1 to 9, wherein (volume average particle diameter)/(number average particle diameter) of the particles is 1.5 or less.
[Configuration 11]
11. The electrophotographic photoreceptor according to any one of Structures 1 to 10, wherein the ash content of the methyl ethyl ketone-insoluble portion of the surface layer upon sintering is 5.0% by mass or less with respect to the total mass of the surface layer. .
[Configuration 12]
The electrophotographic photoreceptor according to any one of structures 1 to 11 and at least one means selected from the group consisting of charging means and developing means are integrally supported, and the electrophotographic photoreceptor is detachably attachable to the electrophotographic photoreceptor. A process cartridge characterized by:
[Configuration 13]
An electrophotographic apparatus comprising the electrophotographic photoreceptor according to any one of structures 1 to 11, charging means, developing means and transfer means.

1a to d: electrophotographic photosensitive members 2a to d: charging rollers 3a to d: exposure means 4a to d: developing means 5a to 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 supply
22: constant current diode
50: Paper 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 401 Exposed portion of grains 402 Other than exposed portion of grains 601 Exposed portion 602 Surface of surface layer

Claims (13)

An electrophotographic photoreceptor having a support and a photosensitive layer on the support,
the surface layer of the electrophotographic photoreceptor contains particles,
The surface layer has particles partially exposed from the surface layer in the particles contained in the surface layer,
The volume average particle size of the particles 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,
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 with respect to the total volume of the particles contained in the surface layer. and an electrophotographic photoreceptor. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a charge generation layer and a charge transport layer on the charge generation layer, and the charge transport layer is the surface layer. The photosensitive layer has a charge generation layer and a charge transport layer on the charge generation layer, the electrophotographic photoreceptor further has a protective layer on the photosensitive layer, and the protective layer is the surface layer. The electrophotographic photoreceptor according to claim 1, wherein 2. The electronic device according to claim 1, wherein the photosensitive layer is a single-layer type photosensitive layer, the electrophotographic photoreceptor further has a protective layer on the photosensitive layer, and the protective layer is the surface layer. photoreceptor. When the surface layer is viewed from above, the total area of the exposed portions of the grains partially exposed from the surface layer is S1, and the grains other than the exposed portions of the grains partially exposed from the surface layer are defined as S1. 2. The electrophotographic photoreceptor according to claim 1, wherein S1/(S1+S2) satisfies the following formula (A), where S2 is the total area of .
0.15≦S1/(S1+S2)≦0.80 Formula (A) When the surface layer is viewed from above, the total area of the exposed portions of the particles is S1, and the total area of the particles other than the exposed portions is S2, the coefficient of variation of S1/(S1+S2) is 25%. 6. The electrophotographic photoreceptor according to claim 5, wherein: 2. The electrophotographic photoreceptor according to claim 1, wherein SF-2 of the shape of the exposed portions of the particles is 135 or less when the surface layer is viewed from above. 2. The electrophotographic photosensitive member according to claim 1, wherein 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. 2. The electrophotographic photoreceptor according to claim 1, wherein the particles have a Young's modulus of 0.60 GPa or more. 2. The electrophotographic photoreceptor according to claim 1, wherein (volume average particle diameter)/(number average particle diameter) of the particles is 1.5 or less. 2. The electrophotographic photosensitive member according to claim 1, wherein the ash content of the insoluble portion of methyl ethyl ketone in the surface layer upon sintering is 5.0% by mass or less with respect to the total mass of the surface layer. Integrally supporting the electrophotographic photoreceptor according to any one of claims 1 to 11 and at least one means selected from the group consisting of a charging means and a developing means, and detachable from the electrophotographic photoreceptor A process cartridge characterized by: An electrophotographic apparatus comprising the electrophotographic photoreceptor according to any one of claims 1 to 11, charging means, developing means and transfer means.

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