JP7504954B2 - Process cartridge - Google Patents

Description

The present invention relates to a process cartridge used in copying machines and printers that use electrophotographic or electrostatic recording methods.

In recent years, there has been a demand for ever higher image quality in printers and copiers. Furthermore, as the environments in which users use these devices are becoming more diverse, there is a demand for stable image quality regardless of the environment in which they are used.

In response to this demand, many toners have been proposed that are manufactured using the emulsion aggregation method, which allows for a wide range of material options and allows for easy control of the shape of toner particles. In the emulsion aggregation method, a resin particle dispersion is prepared using emulsion polymerization, forced emulsification, phase inversion emulsification, etc., and a colorant dispersion is prepared by dispersing a colorant in a solvent. These are then mixed together, and an aggregator is used to form aggregates that correspond to the toner particle size. These are then fused and united by heating to produce the toner.

A polyvalent metal ion is generally used as the coagulant, and the presence of metal ions derived from the coagulant in the toner particles allows the charge accumulated on the toner particle surface to leak. This makes it possible to suppress the charge-up phenomenon of the toner, particularly in low-temperature, low-humidity environments where charge is easily accumulated, and to suppress the adverse effect of the toner being developed in non-printed areas of an image due to poor toner charging (hereinafter referred to as "fogging"). On the other hand, in high-temperature, high-humidity environments with a high moisture content in the air, the charge on the toner surface leaks and the charge amount decreases, which also causes problems such as fogging and the inability to obtain an image with excellent gradation. Excellent gradation means that the difference in color shading of the image can be clearly seen. The color shading is expressed by increasing or decreasing the amount of toner per unit area on the image, but when the charge amount of the toner is low, the amount of toner developed on the electrophotographic photoconductor (hereinafter also referred to as "photoconductor") may be increased or extremely decreased, making it difficult to see subtle differences in color shading on the image.

In response to these issues, Patent Document 1 proposes a process cartridge that combines an emulsion aggregation toner with a photoconductor having a surface protective layer (hereinafter also referred to as a "protective layer") that contains specific conductive particles. In Patent Document 1, image flow in high-temperature, high-humidity environments is improved by stabilizing the charging characteristics of the photoconductor and improving its mechanical strength, and it is believed that such an innovation will also be effective in suppressing the occurrence of fogging.

JP 2009-229495 A

However, the inventors' investigations have shown that even the configuration of Patent Document 1 could not improve the deterioration of gradation in a high-temperature, high-humidity environment. This is presumably because the charging characteristics of the protective layer of the photoconductor were not appropriate. In order to obtain an image with excellent gradation, it is believed that there is still room for improvement in the characteristics and content of the conductive particles in the protective layer.

Therefore, the present invention aims to provide a process cartridge that can suppress fogging and produce images with excellent gradation regardless of the usage environment.

The process cartridge according to the present invention is a process cartridge that is detachably attached to a main body of an electrophotographic apparatus, the process cartridge having an electrophotographic photosensitive member, and a developing means having a toner storage section that stores toner and supplies the toner to a surface of the electrophotographic photosensitive member, the electrophotographic photosensitive member having a conductive support, and a photosensitive layer and a surface protective layer formed on the conductive support in this order, the surface protective layer containing conductive particles, the content of the conductive particles being 20.0 volume % or more and 70.0 volume % or less of the total volume of the surface protective layer, the volume resistivity of the surface protective layer being 1.0×10 ⁹ Ω·cm or more and 1.0×10 ¹⁴ The toner accommodated in the toner accommodation section has toner particles containing a binder resin and an external additive, the toner particles have at least one polyvalent metal element selected from the group consisting of aluminum, magnesium, calcium and iron, and the total content of the polyvalent metal element in the toner particles, as measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), is 0.10 μmol/g or more and 1.25 μmol/g or less.

The present invention provides a process cartridge that can suppress fogging and produce images with excellent gradation regardless of the usage environment.

FIG. 2 is a schematic view of a process cartridge used for evaluating toner in Examples. FIG. 2 is a diagram showing an example of a comb-shaped electrode for measuring the volume resistivity of a photoconductor according to the present invention. 5 is an example of an image for evaluating the gradation of the process cartridge according to the present invention. 1 is a STEM image showing an example of niobium-containing titanium oxide used in an example. FIG. 1 is a schematic diagram showing an example of niobium-containing titanium oxide used in the examples.

In the present invention, the descriptions "XX or more and YY or less" and "XX to YY" expressing a numerical range mean a numerical range including the endpoints, that is, the lower limit and the upper limit, unless otherwise specified.
The present invention will be described in detail below.
The present inventors have found that in toners containing toner particles containing polyvalent metal elements,
(1) Excellent gradation can be obtained even in a high temperature and high humidity environment.
(2) No fogging occurs in high temperature and high humidity environments.
(3) No fogging due to charge-up occurs in a low-temperature, low-humidity environment.
We conducted intensive research into the following points.

As a result, a process cartridge having a photoconductor, a toner storage section that stores toner, and a developing means that supplies toner to the surface of the photoconductor,
the photoreceptor has a conductive support, and a photosensitive layer and a surface protective layer formed on the conductive support in this order, the surface protective layer contains conductive particles, the content of the conductive particles is 20.0 volume % or more and 70.0 volume % or less of the total volume of the surface protective layer, and the volume resistivity of the surface protective layer is 1.0 x 10 ⁹ Ω·cm or more and 1.0 x 10 ¹⁴ Ω·cm or less,
the toner contained in the toner container comprises toner particles containing a binder resin and an external additive, the toner particles contain at least one polyvalent metal element selected from the group consisting of aluminum, magnesium, calcium and iron, and the total content of the polyvalent metal element in the toner particles, as measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), is 0.10 μmol/g or more and 1.25 μmol/g or less;
It has been found that this makes it possible to suppress fog and form images with excellent gradation, regardless of the usage environment.

Based on the above, the reason why the effects of the present invention are manifested is believed to be as follows.
The gradation of an image is expressed by increasing or decreasing the amount of toner per unit area developed on the photoconductor in the process cartridge to express the difference in color density. The amount of toner developed is controlled by the potential of the electrostatic latent image formed on the surface of the photoconductor and the charge amount of the toner. In order to obtain excellent gradation, it is important that the charge amount of the toner is high and the charge distribution is sharp. For example, in a high-temperature and high-humidity environment with a high moisture content in the air, the charge amount of the toner is likely to decrease, and the amount of toner developed on the photoconductor tends to increase, making it difficult to achieve a difference in density for the subtle potential difference of the electrostatic latent image. In addition, it becomes difficult to control the density of low-density images such as halftones, and when the potential of the electrostatic latent image falls below a certain value, the developability of the toner suddenly decreases, and the image density becomes extremely low.

The inventors have found that by incorporating an appropriate amount of conductive particles into the surface protective layer of the photoreceptor and controlling the volume resistivity of the surface protective layer, a small portion of the charge on the photoreceptor surface can be injected into the toner during development. Furthermore, by controlling the amount of polyvalent metal elements present in the toner particles, the balance between charge injection and charge leakage can be appropriately controlled. Furthermore, by combining these, it has been found that a small portion of the charge on the photoreceptor surface can be injected into the toner during development, increasing the charge amount of the toner and sharpening the charge amount distribution. This makes it possible to provide a process cartridge that can obtain images with excellent gradation regardless of the usage environment and suppress the occurrence of fogging even after long-term use.

The photoreceptor according to the present invention has a conductive support, a photosensitive layer, and a protective layer which is a surface layer. The protective layer contains conductive particles, and the content of the conductive particles is 20.0 volume % or more and 70.0 volume % or less of the total volume of the protective layer. Furthermore, the protective layer is characterized in that the volume resistivity is 1.0×10 ⁹ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less. Although the protective layer contains a large amount of conductive particles, the volume resistivity is maintained relatively high, so that it is possible to inject electric charge into the toner according to the present invention through the conductive particles while ensuring charge retention.

If the content of conductive particles is less than 20.0% by volume, the charge injection ability into the toner according to the present invention is reduced, so the charge amount of the toner during development is low, and the toner is more likely to lose gradation and fog. On the other hand, if the content of conductive particles exceeds 70%, the protective layer itself becomes brittle, and the surface of the photoconductor is more likely to be scraped off over long-term use. This reduces the charging uniformity of the photoconductor, making it more likely to lose gradation and fog. A more preferable content of conductive particles is 40.0% to 70.0% by volume of the protective layer.

Another feature is that the volume resistivity of the protective layer is 1.0×10 ⁹ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less. If the volume resistivity of the protective layer is less than 1.0×10 ⁹ Ω·cm, the resistance of the protective layer is too low, making it difficult to maintain the potential and gradation is likely to decrease. If the volume resistivity of the protective layer exceeds 1.0×10 ¹⁴ Ω·cm, the resistance of the protective layer is too high, significantly deteriorating the charging property of the toner.

More preferably, the volume resistivity of the protective layer is 1.0×10 ¹⁰ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less. The volume resistivity of the protective layer can be controlled, for example, by the particle diameter of the conductive particles. The particle diameter of the conductive particles is preferably 40 nm or more and 300 nm or less, more preferably 100 nm or more and 250 nm or less, in terms of number average particle diameter. If the number average particle diameter of the conductive particles is less than 40 nm, the specific surface area of the conductive particles increases, and moisture adsorption increases in the vicinity of the conductive particles on the surface of the protective layer, which tends to reduce the volume resistivity of the protective layer. If the number average particle diameter of the conductive particles exceeds 300 nm, the dispersion of the particles in the protective layer deteriorates and the area of the interface with the binder resin decreases, which increases the resistance at the interface and tends to deteriorate the charge injection property.

Examples of conductive particles contained in the protective layer include particles of metal oxides such as titanium oxide, zinc oxide, tin oxide, and indium oxide, among which titanium oxide is preferred. In particular, anatase-type titanium oxide facilitates charge transfer within the protective layer, resulting in good charge injection. The degree of anatase conversion of anatase-type titanium oxide is preferably 90% or more. The metal oxide particles may be doped with atoms such as niobium, phosphorus, and aluminum, or their oxides, and titanium oxide particles containing niobium and having a configuration in which niobium is unevenly distributed near the particle surface are particularly preferred. By unevenly distributing niobium near the surface, charges can be efficiently exchanged. More specifically, the titanium oxide particles have a concentration ratio calculated as "niobium atomic concentration/titanium atomic concentration" at 5% inside the maximum diameter of the particle from the surface of the particle, which is 2.0 times or more, compared to the concentration ratio calculated as "niobium atomic concentration/titanium atomic concentration" at the center of the particle. The niobium atom concentration and titanium atom concentration are obtained by EDS analysis using a scanning transmission electron microscope (STEM). FIG. 4 shows an STEM image of an example of the niobium-containing titanium oxide particles used in the examples of the present invention. Details will be described later, but the niobium-containing titanium oxide particles used in the examples of the present invention are produced by coating the titanium oxide particles, which serve as the core material, with niobium-containing titanium oxide and then firing the coated titanium oxide. Therefore, it is considered that the coated niobium-containing titanium oxide grows as niobium-doped titanium oxide by so-called epitaxial growth along the crystals of the titanium oxide core material. The niobium-containing titanium oxide produced in this way has a smaller density near the surface compared to the density at the center of the particle, as shown in FIG. 4, and is controlled to have a core-shell-like shape.

The STEM image of FIG. 4 is shown in FIG. 5. In such niobium-containing titanium oxide particles, the niobium/titanium atomic concentration ratio near the surface of the particle is larger than the niobium/titanium atomic concentration ratio at the center of the particle, and niobium atoms are unevenly distributed near the particle surface. Specifically, the niobium/titanium atomic concentration ratio at 5% of the maximum diameter of the particle from the surface of the particle is 2.0 times or more compared to the niobium/titanium atomic concentration ratio at the center of the particle. By making it 2.0 times or more, the charge can be easily moved in the protective layer, and the charge injection property can be improved. If it is less than 2.0 times, the transfer of charge becomes difficult. In FIG. 5, the reference numeral 31 indicates the center of the conductive particle, the reference numeral 32 indicates the vicinity of the surface of the conductive particle, the reference numeral 33 indicates an X-ray that analyzes the center of the conductive particle, and the reference numeral 34 indicates an X-ray that analyzes 5% of the particle diameter from the surface of the conductive particle.

The preferred niobium atom content is 0.5% by mass or more and 15.0% by mass or less, and more preferably 2.6% by mass or more and 10.0% by mass or less, based on the mass of the niobium atom-containing titanium oxide particles.

The toner according to the present invention will now be described.
The toner according to the present invention comprises toner particles containing a binder resin and an external additive, the toner particles contain at least one polyvalent metal element selected from the group consisting of aluminum, magnesium, calcium and iron, and is characterized in that the total content of the polyvalent metal element in the toner particles, as measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), is 0.10 μmol/g or more and 1.25 μmol/g or less.

The toner particles contain at least one polyvalent metal element selected from the group consisting of aluminum, magnesium, calcium, and iron as an injection site for injecting electric charge from a photoreceptor. The electrical resistivities of these metal elements at 20° C. are 2.7×10 ⁻⁸ Ω·m for aluminum, 4.2×10 ⁻⁸ Ω·m for calcium, 4.5×10 ⁻⁸ Ω·m for magnesium, and 9.7×10 ⁻⁸ Ω·m for iron (quoted from “Chemical Handbook: Basics II” (Revised 4th Edition, edited by the Chemical Society of Japan, Maruzen, 1993, p. 490)). The present inventors have confirmed that by incorporating an appropriate amount of these metal elements in the toner, stable charge injection properties and charge retention properties are exhibited. Although not used in the toner according to the present invention, for reference, metal elements with lower electric resistance include copper (1.7× ¹⁰ Ω·m) and silver (1.6× ¹⁰ Ω·m) (quoted from "Chemical Handbook: Basics II" (4th revised edition, edited by the Chemical Society of Japan, Maruzen, 1993, p. 490)).

If the content of at least one polyvalent metal element selected from the group consisting of aluminum, magnesium, calcium and iron in the toner particles is 0.10 μmol/g or more and 1.25 μmol/g or less, by combining it with the photoconductor of the present invention, it is possible to exhibit the injection charging performance from the photoconductor to the toner, and obtain an image with excellent gradation. If the content of the polyvalent metal element is less than 0.10 μmol/g, the charge injection property is significantly reduced, so that the charge is not imparted to the toner, and excellent gradation is not obtained. In addition, since the toner is easily charged up, the charge distribution of the toner becomes broad in a low-temperature, low-humidity environment, and fogging is easily generated. If the content of the polyvalent metal element exceeds 1.25 μmol/g, although the charge injection property is excellent, the charge is easily leaked, and gradation and fogging are easily deteriorated.

More specifically, the content of the above polyvalent metal elements is 0.50 μmol/g or less for aluminum, and more preferably 0.10 μmol/g or more and 0.32 μmol/g or less. For magnesium, it is 0.80 μmol/g or less, for calcium, it is 0.90 μmol/g or less, and for iron, it is 1.25 μmol/g or less, and it is preferable that the total content of these four polyvalent metal elements is 0.10 μmol/g or more and 1.25 μmol/g or less. The reason why the preferable range of the content of polyvalent metal elements differs depending on the substance is thought to be related to the resistance value of the metal. Among the above, aluminum is preferable because it has a low electrical resistance value and shows excellent injectability even in small amounts.

It is preferable that the polyvalent metal element is present on the surface of the toner particles and dispersed inside the toner particles. The presence of the polyvalent metal element inside the toner particles allows the charge applied to the surface of the toner particles to be accumulated inside as well. If the above-mentioned polyvalent metal element is present only on the surface of the toner particles, for example by externally adding metal oxide particles to the toner particles, the leakage property becomes too high and the injected charge leaks through members such as the toner carrier, making it difficult to achieve the desired effect. Furthermore, with long-term use, the external additive is embedded in the toner surface or is removed, which can easily cause the charging characteristics of the toner to fluctuate, making it difficult to obtain images of stable quality.

The means for making the polyvalent metal element exist inside the toner particle is preferably to produce the toner particle by emulsion aggregation method and to incorporate the polyvalent metal element into the particle via an aqueous medium. In the emulsion aggregation method, the metal element is ionized in an aqueous medium and then incorporated into the toner particle, so that the metal element can be uniformly dispersed. Furthermore, in emulsion aggregation toner, a carboxy group is generally present in the molecular chain constituting the binder resin. The metal ion added as an aggregating agent forms a coordinate bond with the carboxy group, so that an excellent conductive path can be formed in the resin fine particles. In addition, trivalent aluminum can be coordinated with the carboxy group in a smaller amount than divalent magnesium and calcium, and iron that can have a mixed valence, and can exhibit better charge injection properties.

The toner according to the present invention may contain a wax. Known substances can be used as the wax, and examples of such wax include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, or block copolymers thereof, waxes obtained by grafting aliphatic hydrocarbon waxes with vinyl monomers such as styrene or acrylic acid, and saturated fatty acid ester compounds such as stearyl stearate, behenyl behenate, dibehenyl sebacate, distearyl dodecanedioate, distearyl octadecanedioate, nonanediol dibehenate, ethylene glycol distearate, ethylene glycol dibehenate, butanediol dibehenate, butanediol distearate, pentaerythritol tetrabehenate, and dipentaerythritol hexastearate. Among these, ester compounds are preferred because they have higher polarity and lower electrical resistance than hydrocarbon waxes, and therefore help inject charge into the toner particles.

The configuration of the photoreceptor according to the present invention will be described in detail below.
<Protective Layer>
When the protective layer is a surface layer, the conductive particles according to the present invention are contained on the surface of the protective layer. The protective layer may contain a polymer of a compound having a polymerizable functional group and a resin. Examples of the polymerizable functional group include 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 carboxy group, a thiol group, a carboxylic anhydride group, a carbon-carbon double bond group, an alkoxysilyl group, and a silanol group. A monomer having a charge transporting ability may be used as the compound having a polymerizable functional group. The compound having a polymerizable functional group may have a charge transporting structure in addition to the chain polymerizable functional group.

Examples of the resin include polyester resin, acrylic resin, phenoxy resin, polycarbonate resin, polystyrene resin, phenol resin, melamine resin, and epoxy resin. Among them, polycarbonate resin, polyester resin, and acrylic resin are preferable. The protective layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the reaction include thermal polymerization reaction, photopolymerization reaction, and radiation polymerization reaction. Examples of the polymerizable functional group possessed by the monomer having a polymerizable functional group include an acryloyl group and a methacryloyl group. A material having a charge transport function may be used as the monomer having a polymerizable functional group.

The protective layer can be formed by preparing a coating solution for the protective layer containing the above-mentioned materials and solvent, forming this coating film on the photosensitive layer, and drying and/or curing it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, sulfoxide-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

The protective layer may contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slipping agents, abrasion resistance improvers, etc. Specific examples of such additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.
The average thickness of the protective layer is preferably from 0.2 μm to 5 μm, and more preferably from 0.5 μm to 3 μm.
The material and particle size of the conductive particles contained in the protective layer are as described above.

<Conductive Support>
The photoreceptor according to the present invention has a conductive support having electrical conductivity. The shape of the support may be cylindrical, belt-like, or sheet-like, and is preferably a cylindrical support. The surface of the support may be subjected to electrochemical treatment such as anodization, blasting, cutting, or the like. The material of the support is preferably metal, resin, glass, or the like. Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among these, an aluminum support using aluminum is preferable. It is also preferable to impart electrical conductivity to resin or glass by a treatment such as mixing or coating a conductive material.

<Conductive Layer>
In the photoreceptor according to the present invention, a conductive layer may be provided on the support. By providing the conductive layer, scratches and unevenness on the support surface can be concealed and light reflection on the support surface can be controlled. The conductive layer preferably contains conductive particles and a resin. Examples of the material of the conductive particles include metal oxides, metals, and carbon black. Examples of the metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of the metals include aluminum, nickel, iron, nichrome, copper, zinc, and silver. Among these, it is preferable to use metal oxides as the conductive particles, and it is particularly preferable to use titanium oxide, tin oxide, and zinc oxide.

When metal oxides are used as 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 elements such as niobium, phosphorus, or aluminum, or their oxides. In particular, titanium oxide particles with niobium atoms distributed unevenly on or near the surface are preferred.

In addition, when metal oxides are used as conductive particles, the number-average particle size is preferably 1 nm or more and 500 nm or less, and more preferably 3 nm or more and 400 nm or less.

Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, and alkyd resin. The conductive layer may further contain silicone oil, resin particles, and a masking agent such as titanium oxide.

The conductive layer can be formed by preparing a coating solution for the conductive layer containing the above-mentioned materials and solvent, forming this coating film on a support, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Examples of dispersion methods for dispersing the conductive particles in the coating solution for the conductive layer include methods using a paint shaker, a sand mill, a ball mill, and a liquid collision type high-speed disperser.

The average thickness of the conductive layer is preferably 1 μm or more and 40 μm or less, and particularly preferably 3 μm or more and 30 μm or less.

<Undercoat layer>
In the photoreceptor according to 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 layers is improved, and a charge injection blocking function can be imparted. The undercoat layer preferably contains a resin. The undercoat layer may also be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group.

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

Polymerizable functional groups possessed by monomers having polymerizable functional groups include isocyanate groups, blocked isocyanate groups, methylol groups, alkylated methylol groups, epoxy groups, metal alkoxide groups, hydroxyl groups, amino groups, carboxy groups, thiol groups, carboxylic anhydride groups, and carbon-carbon double bond groups.

For the purpose of improving electrical properties, the undercoat layer may further contain an electron transporting material, a metal oxide, a metal, a conductive polymer, etc. Among these, it is preferable to use an electron transporting material or a metal oxide.
Examples of the electron transport substance include a quinone compound, an imide compound, a benzimidazole compound, a cyclopentadienylidene compound, a fluorenone compound, a xanthone compound, a benzophenone compound, a cyanovinyl compound, an aryl halide compound, a silole compound, a boron-containing compound, etc. An electron transport substance having a polymerizable functional group may be used as the electron transport substance, and the undercoat layer may be formed as a cured film by copolymerizing the electron transport substance with the monomer having the polymerizable functional group described above.
Examples of metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, silicon dioxide, etc. Examples of metals include gold, silver, aluminum, etc.

The metal oxide particles contained in the undercoat layer may be surface-treated with a surface treatment agent such as a silane coupling agent. The method for surface-treating the metal oxide particles is a general method. For example, a dry method or a wet method may be used.
In the dry method, metal oxide particles are stirred in a mixer capable of high-speed stirring, such as a Henschel mixer, while an alcohol aqueous solution, an organic solvent solution, or an aqueous solution containing a surface treatment agent is added to the metal oxide particles to uniformly disperse them, and then the particles are dried.
In the wet method, the metal oxide particles and the surface treatment agent are stirred in a solvent or dispersed in a sand mill using glass beads or the like, and the solvent is removed by filtration or distillation under reduced pressure. After the solvent is removed, it is preferable to further perform baking at 100° C. or higher.

The undercoat layer may further contain additives, for example, known materials such as metal powder such as aluminum, conductive materials such as carbon black, charge transport materials, metal chelate compounds, and organometallic compounds.
Examples of the charge transport substance include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, aryl halide compounds, silole compounds, boron-containing compounds, etc. A charge transport substance having a polymerizable functional group may be used as the charge transport substance, and the undercoat layer may be formed as a cured film by copolymerizing the charge transport substance with the monomer having the polymerizable functional group.

The undercoat layer can be formed by preparing a coating solution for the undercoat layer containing the above-mentioned materials and solvent, forming this coating film on the support or conductive layer, and drying and/or curing it.

Examples of the solvent used in the coating solution for the undercoat layer include organic solvents such as alcohols, sulfoxides, ketones, ethers, esters, halogenated aliphatic hydrocarbons, aromatic compounds, etc. In the present invention, it is preferable to use alcohol-based and ketone-based solvents.
Examples of a dispersion method for preparing a coating solution for the undercoat layer include methods using a homogenizer, an ultrasonic disperser, a ball mill, a sand mill, a roll mill, a vibration mill, an attritor, and a liquid collision type high-speed disperser.

The average thickness of the undercoat layer is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 5 μm or less.

<Photosensitive layer>
The photosensitive layer of the photoreceptor according to the present invention is mainly classified into (1) a laminated type photosensitive layer and (2) a single-layer type photosensitive layer. (1) The laminated type photosensitive layer is a photosensitive layer having a charge generating layer containing a charge generating material and a charge transport layer containing a charge transport material. (2) The single-layer type photosensitive layer is a photosensitive layer containing both a charge generating material and a charge transport material.

(1) Multi-Layer Photosensitive Layer The multi-layer photosensitive layer has a charge generating layer and a charge transport layer.

(1-1) Charge Generation Layer The charge generation layer preferably contains a charge generation material and a resin.

Examples of the charge generating material include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferred. Among phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferred.
The content of the charge generating material in the charge generating layer is preferably from 40% by weight to 85% by weight, and more preferably from 60% by weight to 80% by weight, based on the total weight of the charge generating layer.

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

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

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

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

(1-2) Charge Transport Layer The charge transport layer preferably contains a charge transport material and a resin.

Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, resins having groups derived from these materials, etc. Among these, triarylamine compounds and benzidine compounds are preferred.
The content of the charge transport material in the charge transport layer is preferably from 25% by weight to 70% by weight, and more preferably from 30% by weight to 55% by weight, based on the total weight of the charge transport layer.

Examples of the resin include polyester resin, polycarbonate resin, acrylic resin, polystyrene resin, etc. Among these, polycarbonate resin and polyester resin are preferable. As the polyester resin, polyarylate resin is particularly preferable.
The content ratio (mass ratio) of the charge transport material to the resin is preferably from 4:10 to 20:10, and more preferably from 5:10 to 12:10.

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

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

The average thickness of the charge transport layer is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less.

(2) Single-layer type photosensitive layer The single-layer type photosensitive layer can be formed by preparing a coating solution for the photosensitive layer containing a charge generating substance, a charge transporting substance, a resin and a solvent, forming the coating film on a support or a conductive layer or an undercoat layer, and drying it. The charge generating substance, the charge transporting substance and the resin are the same as the examples of materials in the above "(1) Multi-layer type photosensitive layer".

The binder resin, wax as a release agent, colorant, charge control agent, and external additives that make up the toner of the present invention are described in detail below.

<Binder resin>
The binder resin of the toner according to the present invention is not particularly limited and may be any known resin, but is preferably a vinyl resin, a polyester resin, etc. Examples of the vinyl resin, polyester resin, and other binder resins include the following resins or polymers.
Homopolymers of styrene and its substitutes such as polystyrene and polyvinyltoluene; styrene-based copolymers such as styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, and styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyamide resin, epoxy resin, polyacrylic resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, and aromatic petroleum resin. These binder resins can be used alone or in combination, and styrene copolymers are preferred.

If these binder resins contain a carboxy group, they are preferred because they coordinate with polyvalent metal ions to form an excellent conductive path, as described above.
Examples of the polymerizable monomer containing a carboxy group include acrylic acid, methacrylic acid; α-alkyl derivatives or β-alkyl derivatives of acrylic acid or methacrylic acid, such as α-ethylacrylic acid and crotonic acid; unsaturated dicarboxylic acids, such as fumaric acid, maleic acid, citraconic acid and itaconic acid; and unsaturated dicarboxylic acid monoester derivatives, such as succinic acid monoacryloyloxyethyl ester, succinic acid monoacryloyloxyethylene ester, phthalic acid monoacryloyloxyethyl ester, and phthalic acid monomethacryloyloxyethyl ester.

As the polyester resin, a resin obtained by polycondensation of a carboxylic acid component and an alcohol component as described below can be used.
Examples of the carboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, fumaric acid, maleic acid, cyclohexanedicarboxylic acid, and trimellitic acid. Examples of the alcohol component include bisphenol A, hydrogenated bisphenol, an ethylene oxide adduct of bisphenol A, a propylene oxide adduct of bisphenol A, glycerin, trimethylolpropane, and pentaerythritol.
The polyester resin may be a polyester resin containing a urea group. It is preferable that the carboxyl groups at the terminals of the polyester resin are not capped.

<Wax>
The toner according to the present invention may contain a wax as a release agent. The wax that is preferably used is as described above. The content of the wax is preferably 5.0 parts by mass or more and 20.0 parts by mass or less with respect to 100.0 parts by mass of the binder resin or the polymerizable monomer that forms the binder resin.

<Coloring Agent>
The colorant is not particularly limited, and any known colorant can be used.

Examples of yellow pigments that can be used include condensed azo compounds such as yellow iron oxide, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, and tartrazine lake, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds. Specific examples include the following.
C.I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 155, 168, 180, 185, 193.

Red pigments include condensed azo compounds such as red iron oxide, permanent red 4R, lithol red, pyrazolone red, watching red calcium salt, lake red C, lake red D, brilliant carmine 6B, brilliant carmine 3B, eoxin lake, rhodamine lake B, and alizarin lake, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Specific examples include the following. C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 150, 166, 169, 177, 184, 185, 202, 206, 220, 221, 254.

Blue pigments include alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chloride, fast sky blue, copper phthalocyanine compounds such as indanthrene blue BG and their derivatives, anthraquinone compounds, basic dye lake compounds, etc. Specific examples include the following: C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, 66.

Black pigments include carbon black, aniline black, non-magnetic ferrite, magnetite, and pigments toned to black using the above yellow, red, and blue colorants. These colorants can be used alone or in mixtures, or even in the form of a solid solution.

If necessary, the colorant may be surface-treated with a substance that does not inhibit polymerization. The content of the colorant is preferably 3.0 parts by mass or more and 15.0 parts by mass or less per 100.0 parts by mass of the binder resin or the polymerizable monomer that produces the binder resin.

<Charge Control Agent>
The toner according to the present invention may contain a charge control agent. Any known charge control agent can be used. In particular, a charge control agent that has a high charging speed and can stably maintain a constant charge amount is preferred. Furthermore, when the toner particles are produced by a direct polymerization method, a charge control agent that has low polymerization inhibition properties and is substantially free of solubilized matter in an aqueous medium is preferred. Examples of charge control agents that control the toner particles to be negatively charged include the following.

Organometallic compounds and chelating compounds include monoazo metal compounds, acetylacetone metal compounds, aromatic oxycarboxylic acids, aromatic dicarboxylic acids, oxycarboxylic acids and dicarboxylic acid-based metal compounds. Other examples include aromatic oxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides or esters, and phenol derivatives such as bisphenol. Further examples include urea derivatives, metal-containing salicylic acid compounds, metal-containing naphthoic acid compounds, boron compounds, quaternary ammonium salts, and calixarenes.

These charge control agents can be used alone or in combination of two or more. The amount of charge control agent added is preferably 0.01 parts by weight or more and 10.0 parts by weight or less per 100.0 parts by weight of the binder resin.

<External Additives>
The toner according to the present invention may contain an external additive for the purpose of improving the fluidity, chargeability, blocking property, and the like.
Examples of the external additive include inorganic fine particles such as silica fine particles, alumina fine particles, and titanium oxide fine particles. These may be used alone or in combination of two or more. These inorganic fine particles are preferably surface-treated with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, or the like to improve heat-resistant storage properties and environmental stability.

The BET specific surface area of the external additive is preferably 10.0 m ² /g or more and 450.0 m ² /g or less. The BET specific surface area can be determined by a low-temperature gas adsorption method using a dynamic constant pressure method according to the BET method (preferably the BET multipoint method). For example, a specific surface area measuring device (product name: Gemini 2375 Ver. 5.0, manufactured by Shimadzu Corporation) is used to adsorb nitrogen gas onto the sample surface, and the BET multipoint method is used to measure, thereby calculating the BET specific surface area (m ² /g).

The total content of these various external additives is preferably 0.05 parts by mass or more and 5.0 parts by mass or less per 100.0 parts by mass of the toner particles. The type and content of the external additives can be appropriately selected as long as the effect of the present invention is not impaired.

<Method of Manufacturing Toner Particles>
The toner particles can be produced by known means, and a kneading and grinding method or a wet production method can be used. From the viewpoint of uniform particle size and shape controllability, a wet production method is preferred. Examples of the wet production method include a suspension polymerization method, a dissolution suspension method, an emulsion polymerization aggregation method, and an emulsion aggregation method, and the emulsion aggregation method is more preferred. In other words, the toner particles are preferably emulsion aggregation toner particles. This is because polyvalent metal elements can be easily ionized in an aqueous medium, and polyvalent metal elements can be easily contained in the toner particles when the binder resin is aggregated.
In the emulsion aggregation method, toner particles are produced through the steps of emulsifying resin particles, aggregating, fusing, cooling, and washing. If necessary, a shell-forming step can be added after the cooling step to produce a core-shell toner.

Resin particle emulsification process Resin particles mainly composed of a binder resin can be prepared by a known method. For example, the binder resin is dissolved in an organic solvent and added to an aqueous medium, and dispersed in particles in the aqueous medium together with a surfactant and a polymer electrolyte using a dispersing machine such as a homogenizer, and then the solvent is removed by heating or reducing pressure to prepare a resin particle dispersion. Any organic solvent that dissolves the resin can be used as the organic solvent used for dissolving, but tetrahydrofuran, ethyl acetate, chloroform, etc. are preferred from the viewpoint of high solubility.
From the viewpoint of environmental load, it is preferable to add the resin, a surfactant, a base, etc. to an aqueous medium, and emulsify and disperse the resin in an aqueous medium that is substantially free of organic solvents using a dispersing machine that applies high-speed shear force, such as a Clearmix, a Homomixer, or a Homogenizer.

The surfactant used during emulsification is not particularly limited, but examples include the following: anionic surfactants such as sulfate ester salts, sulfonate salts, carboxylate salts, phosphate esters, and soap-based surfactants; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. The surfactants may be used alone or in combination of two or more.

The volume distribution median diameter of the resin microparticles is preferably 0.05 to 1.0 μm, and more preferably 0.05 to 0.4 μm. If it is 1.0 μm or less, it is easy to obtain toner particles with a volume distribution median diameter of 4.0 to 7.0 μm, which is an appropriate size for toner particles. The volume distribution median diameter can be measured using a dynamic light scattering particle size distribution analyzer (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.).

The aggregation process is a process in which the above-mentioned resin microparticles and, if necessary, colorant microparticles, wax microparticles, etc. are mixed to prepare a mixed liquid, and then the particles contained in the prepared mixed liquid are aggregated to form aggregates.
As the flocculant, in addition to surfactants having the polarity opposite to that of the above-mentioned surfactants, inorganic salts and inorganic metal salts having a valence of 2 or more can be suitably used. In particular, inorganic metal salts can be ionized by adding a polyvalent metal element to an aqueous medium, and can easily form a coordinate bond with a carboxyl group contained in the binder resin. This makes it easier to control the flocculation property and the toner charge property. Specific examples of preferred inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, iron chloride, aluminum chloride, and aluminum sulfate, and inorganic metal salt polymers such as polyiron chloride, polyaluminum chloride, and polyaluminum hydroxide. Among them, trivalent aluminum salts and their polymers are particularly suitable. In general, in order to obtain a sharper particle size distribution, it is preferable that the valence of the inorganic metal salt is divalent rather than monovalent, and trivalent or more rather than divalent.

The addition of the flocculant is not particularly limited, but it is preferable to add it at 25 to 35°C, and then heat and increase the temperature at a temperature below the glass transition temperature (Tg) of the resin particles. When mixing is performed at a temperature below Tg, fusion between the resin particles is suppressed and aggregation proceeds in a stable state. As a result, the metal element derived from the flocculant can be coordinated uniformly with the carboxyl groups in the resin. The above mixing can be performed using a known mixing device, homogenizer, mixer, etc.

The weight average particle size of the aggregates formed here is not particularly limited, but it is usually best to control it to 4.0 μm to 7.0 μm so that it is roughly the same as the weight average particle size of the toner particles to be obtained. This can be easily controlled, for example, by appropriately setting and changing the temperature when the above-mentioned aggregating agent is added and mixed, and the above-mentioned stirring and mixing conditions. The particle size distribution of the toner particles can be measured using a particle size distribution analyzer (Coulter Multisizer III: manufactured by Beckman Coulter, Inc.) using the Coulter method.

Fusion process The fusion process is a process in which the aggregates are heated to a temperature equal to or higher than the glass transition temperature (Tg) of the resin to fuse them, thereby producing particles having smooth aggregate surfaces. Prior to the primary fusion process, a chelating agent, a pH adjuster, a surfactant, etc. may be appropriately added to prevent fusion between toner particles.
Examples of chelating agents include: ethylenediaminetetraacetic acid (EDTA) and its alkali metal salts such as the Na salt, sodium gluconate, sodium tartrate, potassium and sodium citrate, nitrotriacetate (NTA) salts, many water-soluble polymers containing both COOH and OH functionality (polyelectrolytes).
The heating temperature may be between the glass transition temperature (Tg) of the resin contained in the aggregate and the temperature at which the resin thermally decomposes. The heating/fusion time is short if the heating temperature is high, and long if the heating temperature is low. That is, the heating/fusion time depends on the heating temperature and cannot be generally specified, but is generally 10 minutes to 10 hours.

The cooling step is a step of cooling the temperature of the aqueous medium containing the particles to a temperature lower than the glass transition temperature (Tg) of the resin used. If the cooling is not performed to a temperature lower than the Tg, coarse particles may be generated. The specific cooling rate is 0.1 to 50°C/min.

-Shelling step If necessary, a shelling step can be inserted before the washing and drying step described below. The shelling step is a step in which fine resin particles are newly added to and attached to the particles produced in the previous steps to form a shell.
The resin particles added here may have the same structure as the binder resin particles used in the core, or may have a different structure.

The particles produced through the above steps are washed and filtered with ion-exchanged water whose pH has been adjusted with sodium hydroxide or potassium hydroxide, and then washed and filtered with ion-exchanged water several times. Thereafter, the particles are dried to obtain emulsion aggregate toner particles.

<Toner Manufacturing Method>
The toner according to the present invention may be toner particles to which an external additive has been added. Examples of the external additive device include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, an FM mixer (manufactured by Nippon Coke & Engineering Co., Ltd.), a Nauta mixer, and a Mechano Hybrid. In order to control the coating state of the external additive, the toner can be prepared by adjusting the rotation speed, processing time, and water temperature and amount of water in the jacket of the external additive device.

<Process cartridge>
The process cartridge of the present invention comprises the photosensitive member described above, a toner storage section which stores toner, and a developing means which supplies toner to the surface of the photosensitive member, and can be configured to be freely attached to and detached from the main body of the electrophotographic device.

FIG. 1 shows an example of the schematic configuration of an electrophotographic apparatus having a process cartridge according to the present invention.
A cylindrical (drum-shaped) photoconductor 1 is driven to rotate around an axis 2 in the direction of an arrow at a predetermined peripheral speed (process speed). The surface of the photoconductor 1 is charged to a predetermined positive or negative potential by a charging means 3 during the rotation process. Although FIG. 1 shows a roller charging method using a roller-type charging member, a corona charging method, a proximity charging method, an injection charging method, or other charging methods may be adopted. Exposure light 4 is irradiated from an exposure means (not shown) onto the charged surface of the photoconductor 1, and an electrostatic latent image corresponding to the target image information is formed. The exposure light 4 is light whose intensity is modulated in response to a time-series electric digital image signal of the target image information, and is output from an image exposure means such as a slit exposure or a laser beam scanning exposure. The electrostatic latent image formed on the surface of the photoconductor 1 is developed (normal development or reversal development) with toner contained in a developing means 5, and a toner image is formed on the surface of the photoconductor 1. The toner image formed on the surface of the photoconductor 1 is transferred to a transfer material 7 by a transfer means 6. At this time, a bias voltage of the opposite polarity to the charge held by the toner is applied from a bias power source (not shown) to the transfer means 6. When the transfer material 7 is paper, the transfer material 7 is taken out from a paper feed section (not shown) and fed between the photoconductor 1 and the transfer means 6 in synchronization with the rotation of the photoconductor 1. The transfer material 7 onto which the toner image has been transferred from the photoconductor 1 is separated from the surface of the photoconductor 1 and transported to a fixing means 8, where the toner image is fixed, and the image is printed out outside the electrophotographic device as an image formed product (print, copy).

After the toner image is transferred to the transfer material 7, the surface of the electrophotographic photoreceptor 1 is cleaned by removing adhesions such as toner (transfer residual toner) by the cleaning means 9. The transfer residual toner can also be removed directly by a developing device or the like by a cleanerless system that has been developed in recent years. Furthermore, the surface of the electrophotographic photoreceptor 1 is repeatedly used for image formation after being subjected to a charge removal process by pre-exposure light 10 from a pre-exposure means (not shown). In addition, if the charging means 3 is a contact charging means using a charging roller or the like, the pre-exposure means is not necessarily required. In the present invention, among the components such as the electrophotographic photoreceptor 1, the charging means 3, the developing means 5, and the cleaning means 9 described above, a plurality of components are placed in a container and supported as one unit to form a process cartridge. This process cartridge can be configured to be detachable from the main body of the electrophotographic device. For example, at least one selected from the charging means 3, the developing means 5, and the cleaning means 9 is supported as one unit together with the electrophotographic photoreceptor 1 to form a cartridge. A guide means 12 such as a rail of the main body of the electrophotographic device can be used to form a process cartridge 11 that can be detachable from the main body of the electrophotographic device. When the electrophotographic device is a copier or printer, the exposure light 4 may be reflected or transmitted light from the original. Alternatively, the exposure light 4 may be light emitted by scanning a laser beam, driving an LED array, or driving a liquid crystal shutter array in accordance with a signal read from the original by a sensor.

The methods for measuring the various physical properties of the photoreceptor and toner according to the present invention will be described below.
<Calculation of primary particle size of conductive particles>
First, the entire electrophotographic photoreceptor was placed in methyl ethyl ketone (MEK) in a graduated cylinder and irradiated with ultrasonic waves to peel off the resin layer, and then the substrate of the electrophotographic photoreceptor was taken out. Next, the insoluble matter (photosensitive layer and protective layer containing conductive particles) that does not dissolve in MEK was filtered and dried in a vacuum dryer. Furthermore, the obtained solid was suspended in a mixed solvent of tetrahydrofuran (THF)/methylal at a volume ratio of 1:1, the insoluble matter was filtered, and the filtered matter was collected and dried in a vacuum dryer. This operation obtained conductive particles and the resin of the protective layer. Furthermore, the filtered matter was heated to 500°C in an electric furnace so that the solid was only the conductive particles, and the conductive particles were collected. In order to ensure the amount of conductive particles required for measurement, the same treatment was performed on multiple electrophotographic photoreceptors.
A part of the collected conductive particles was dispersed in isopropanol (IPA), and the dispersion was dropped onto a grid mesh with a support film (manufactured by JEOL, Cu150J), and the conductive particles were observed in STEM mode of a scanning transmission electron microscope (JEOL, JEM2800). The observation was performed at a magnification of 500,000 to 1.2 million times to easily calculate the particle diameter of the conductive particles, and STEM images of 100 conductive particles were taken. At this time, the acceleration voltage was set to 200 kV, the probe size was set to 1 nm, and the image size was set to 1024 x 1024 pixels.
Using the obtained STEM image, the primary particle diameter was measured using the image processing software "Image-Pro Plus (manufactured by Media Cybernetics)". First, the straight line tool (Straight Line) on the toolbar was used to select the scale bar displayed at the bottom of the STEM image. In that state, when Set Scale is selected from the Analyze menu, a new window opens and the pixel distance of the selected straight line is entered in the Distance in Pixels field. The value of the scale bar (e.g., 100) is entered in the Known Distance field of the window, the unit of the scale bar (e.g., nm) is entered in the Unit of Measurement field, and the scale setting is completed by clicking OK. Next, a straight line was drawn using the straight line tool so as to be the maximum diameter of the conductive particles, and the particle diameter was calculated. The same operation was carried out for 100 conductive particles, and the number average value of the obtained values (maximum diameter) was taken as the primary particle diameter of the conductive particles.

<Calculation of Niobium Atom/Titanium Atom Concentration Ratio>
A sample piece of 5 mm square was cut from the photoreceptor and cut to a thickness of 200 nm at a cutting speed of 0.6 mm/s using an ultrasonic ultramicrotome (Leica, UC7) to prepare a thin sample. This thin sample was observed at magnifications of 500,000 to 1.2 million times using a scanning transmission electron microscope (JEOL, JEM2800) in STEM mode connected to an EDS analyzer (energy dispersive X-ray analyzer).
Among the cross sections of the observed conductive particles, the cross sections of the conductive particles having a maximum diameter of approximately 0.9 to 1.1 times the primary particle diameter calculated above were visually selected. Then, the constituent elements of the cross sections of the selected conductive particles were collected using an EDS analyzer to prepare EDS mapping images. The collection and analysis of the spectra were performed using an NSS (Thermo Fischer Scientific). The collection conditions were an acceleration voltage of 200 kV, a probe size of 1.0 nm or 1.5 nm was appropriately selected so that the dead time was 15 to 30, the mapping resolution was 256 x 256, and the number of frames was 300. The EDS mapping images were obtained for 100 cross sections of the conductive particles.

By analyzing the EDS mapping image thus obtained, the ratio of the niobium atomic concentration (atomic %) to the titanium atomic concentration (atomic %) at the particle center and within 5% of the maximum diameter of the measured particle from the particle surface is calculated. Specifically, the "line extraction" button of NSS is first pressed, a straight line is drawn so as to be the maximum diameter of the particle, and information on the atomic concentration (atomic %) on the straight line from one surface through the inside of the particle to the other surface is obtained. If the maximum diameter of the particle obtained at this time is in the range of less than 0.9 times or more than 1.1 times the primary particle diameter calculated above, it is excluded from the subsequent analysis. That is, the analysis shown below is performed only on particles having a maximum diameter in the range of 0.9 times or more and less than 1.1 times the primary particle diameter. Next, the niobium atomic concentration (atomic %) at the particle surface on both sides within 5% of the maximum diameter of the measured particle from the particle surface is read, and the arithmetic mean value of the two values obtained is calculated to obtain the "niobium atomic concentration (atomic %) within 5% of the maximum diameter of the measured particle from the particle surface". Similarly, the "titanium atom concentration (atomic %) within 5% of the maximum diameter of the measured particle from the particle surface" is obtained. Next, using these values, the "concentration ratio of niobium atoms to titanium atoms within 5% of the maximum diameter of the measured particle from the particle surface" on both particle surfaces is obtained by the following formula.
(Concentration ratio of niobium atoms to titanium atoms within 5% of the maximum diameter of the measured particle from the particle surface)=
(Niobium atomic concentration (atomic %) within 5% of the maximum diameter of the measured particle from the particle surface)/(Titanium atomic concentration (atomic %) within 5% of the maximum diameter of the measured particle from the particle surface)
Of the two concentration ratios obtained, the smaller value is adopted as the "concentration ratio of niobium atoms to titanium atoms within 5% of the maximum diameter of the measured particle from the particle surface" in the present invention. Note that in normal particles, there is no significant difference between the two concentration ratios.
Also, the niobium atom concentration (atomic %) and titanium atom concentration (atomic %) are read at the position on the straight line that is the midpoint of the maximum diameter. Using these values, the "concentration ratio of niobium atoms to titanium atoms at the center of the particle" is calculated using the following formula.
Concentration ratio of niobium atoms to titanium atoms in the particle center =
(Niobium atom concentration (atomic %) at the center of the particle)/(Titanium atom concentration (atomic %) at the center of the particle)
The "concentration ratio calculated as niobium atomic concentration/titanium atomic concentration at a distance 5% from the particle surface to the maximum diameter of the measured particle to the concentration ratio calculated as niobium atomic concentration/titanium atomic concentration at the particle center" is calculated by the following formula.
(a concentration ratio calculated as niobium atomic concentration/titanium atomic concentration at a portion 5% inside the maximum diameter of the measured particle from the particle surface to a concentration ratio calculated as niobium atomic concentration/titanium atomic concentration at the center of the particle)=
(concentration ratio of niobium atoms to titanium atoms within 5% of the maximum diameter of the measured particle from the particle surface)/(concentration ratio of niobium atoms to titanium atoms at the particle center)

<Calculation of Conductive Particle Content>
Next, four sample pieces of 5 mm square were cut out from the photoreceptor, and the protective layer was three-dimensionalized to 2 μm x 2 μm x 2 μm using Slice & View of FIB-SEM. The content of the conductive particles in the total volume of the protective layer was calculated from the difference in contrast of Slice & View of FIB-SEM. The conditions of Slice & View were as follows.
Analytical sample processing: FIB processing and observation equipment: SII/Zeiss NVision 40
Slice interval: 10 nm
Observation conditions:
Acceleration voltage: 1.0 kV
Sample tilt: 54°
WD: 5mm
Detector: BSE detector Aperture: 60 μm, high current
ABC:ON
Image resolution: 1.25 nm/pixel
The analysis area is 2 μm long x 2 μm wide, and the information for each cross section is integrated to obtain the volume V per 2 μm long x 2 μm wide x 2 μm thick (8 μm ³ ). The measurement environment is temperature: 23° C. and pressure: 1×10 ⁻⁴ Pa. As a processing and observation device, a Strata 400S (sample tilt: 52°) manufactured by FEI can also be used. The information for each cross section was obtained by image analysis of the area of the specified conductive particles of the present invention. The image analysis was performed using image processing software: Image-Pro Plus manufactured by Media Cybernetics.
Based on the obtained information, the volume V of the conductive particles of the present invention in a volume of 2 μm × 2 μm × 2 μm (unit volume: 8 μm ³ ) was determined for each of the four sample pieces, and the conductive particle content [volume %] (= V μm ³ / 8 μm ³ × 100) was calculated. The average value of the conductive particle content values in the four sample pieces was taken as the conductive particle content [volume %] of the present invention in the protective layer relative to the total volume of the protective layer.
At this time, for all four sample pieces, processing was performed up to the boundary between the protective layer and the lower layer to measure the film thickness t (cm) of the protective layer, and the value of the film thickness of the protective layer was used to calculate the volume resistivity ρ _v in the <Method for measuring the volume resistivity of the protective layer> described below.

<Quantitative Determination of Niobium Atoms Contained in Conductive Particles>
The amount of niobium atoms contained in the conductive particles is determined as follows.
The conductive particles collected from the photoconductor in the above <Calculation of the primary particle diameter of the conductive particles> are pelletized by the press molding described below to prepare a sample. The prepared sample is measured with an X-ray fluorescence analyzer (XRF) and the niobium atom content of the entire conductive particles is quantified by the FP method.
Specifically, the amount of niobium pentoxide is determined and converted into the content of niobium atoms.
(i) Example of equipment used: X-ray fluorescence analyzer 3080 (Rigaku Denki Co., Ltd.)
(ii) Sample Preparation Samples are prepared using a sample press molding machine, MAEKAWA Testing Machine (manufactured by MFG Co, Ltd.) 0.5 g of conductive particles are placed in an aluminum ring (model number: 3481E1), and the load is set to 5.0 tons, and the particles are pressed for 1 minute to form pellets.
(iii) Measurement conditions Measurement diameter: 10φ
Measurement potential, voltage: 50 kV, 50-70 mA
2θ angle 25.12°
Crystal plate LiF
Measurement time: 60 seconds

<Powder X-ray diffraction measurement of conductive particles>
A method for determining whether the conductive particles used in the electrophotographic photoreceptor of the present invention contain anatase type titanium oxide or rutile type titanium oxide will be described below.
Identification is performed using the inorganic materials database (AtomWork) of the National Institute for Materials Science (NIMS) from a chart obtained by powder X-ray diffraction using CuKα X-rays. The conductive particles contained in the protective layer of the electrophotographic photoreceptor of the present invention are subjected to the above-mentioned process (quantitative determination of Nb atoms contained in the conductive particles) as an example.
Measuring equipment used: Rigaku Electric Co., Ltd., X-ray diffraction device RINT-TTRII
X-ray tube: Cu
Tube voltage: 50KV
Tube current: 300mA
Scan method: 2θ/θ scan Scan speed: 4.0°/min
Sampling interval: 0.02°
Start angle (2θ): 5.0°
Stop angle (2θ): 40.0°
Attachment: Standard sample holder Filter: Not used Incident monochrome: Used Counter monochromator: Not used Divergence slit: Open Divergence vertical limit slit: 10.00 mm
Scattering slit: open Receiving slit: open Flat plate monochromator: Counter used: Scintillation counter

<Method for measuring volume resistivity of protective layer>
In the present invention, a pA (picoampere) meter was used to measure the volume resistivity.
First, comb-shaped gold electrodes having an interelectrode distance (D) of 180 μm and a length (L) of 59 mm as shown in FIG. 2 were prepared by deposition on a PET film, and a protective layer having a thickness (T1) of 2 μm was provided thereon. Next, a DC voltage (V) of 100 V was applied between the comb-shaped electrodes in environments of temperature 23° C./humidity 50% RH and temperature 32.5° C./humidity 80% RH, and the DC current (I) was measured, and the volume resistivity ρ _v (Ω cm) was calculated using the following formula (1).
Volume resistivity ρ _v (Ω cm) = V (V) × T1 (cm) × L (cm) / {I (A) × D (cm)} (1)

When it is difficult to identify the composition of the conductive particles, binder resin, etc. of the protective layer, the surface resistivity is measured on the surface of the electrophotographic photoreceptor and converted into volume resistivity. When measuring the volume resistivity of the protective layer in a state in which it is coated on the surface of the photoreceptor, rather than the protective layer alone, it is desirable to measure the surface resistivity of the protective layer and convert it into volume resistivity.
In the present invention, comb-shaped electrodes having an interelectrode distance (D) of 180 μm and a length (L) of 59 mm as shown in Fig. 2 are formed by gold deposition on the surface of the protective layer of the electrophotographic photoreceptor. Next, a DC voltage (V) of 1000 V is applied between the comb-shaped electrodes in an environment of a temperature of 23°C and a humidity of 50% RH, and the DC current (I) is measured, and the surface resistivity _ρs of the protective layer is calculated from the DC voltage (V)/DC current (I).
Furthermore, the volume resistivity ρ _v (Ω·cm) was calculated according to the following formula (2) using the film thickness t (cm) of the protective layer measured in the above-mentioned <Calculation of the conductive particle content>.
ρ _v = ρ _s × t (2)
(ρ _v : volume resistivity, ρ _s : surface resistivity, t : thickness of protective layer)
In this measurement, since a minute amount of current is measured, it is preferable to use a device capable of measuring minute current as the resistance measurement device. For example, a picoammeter 4140B manufactured by Hewlett-Packard can be used. It is preferable to select the comb-shaped electrode to be used and the voltage to be applied so as to obtain an appropriate S/N ratio depending on the material and resistance value of the charge injection layer.

<Measurement of Polyvalent Metal Element Content in Toner Particles (ICP-AES)>
(1) Method of Obtaining Toner Particles by Washing External Additive Particles from Toner When the toner contains external additives such as silica fine particles, the external additives are removed from the surfaces of the toner particles through the following process.
5 g of toner is weighed into a 200 ml plastic cup with a lid using a precision balance, 100 ml of methanol is added, and the mixture is dispersed for 5 minutes using an ultrasonic disperser. The toner is confirmed to have been sufficiently precipitated using a centrifuge, and the supernatant liquid is discarded. After repeating the operation of dispersing with methanol and discarding the supernatant three times, 100 ml of 10% NaOH and a few drops of "Contaminon N" (a 10% by weight aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) are added, lightly mixed, and then allowed to stand for 24 hours. Then, the mixture is separated using a centrifuge. In addition, the mixture is repeatedly rinsed with distilled water so that no NaOH remains. The collected toner particles are thoroughly dried using a vacuum dryer to obtain toner particles. The above operation dissolves and removes the external additives from the silica fine particles.

(2) Measurement of the Content of Polyvalent Metal Element in Toner Particles The content of polyvalent metal element in toner particles is quantified by an inductively coupled plasma atomic emission spectrometer (ICP-AES (manufactured by Seiko Instruments Inc.)).
As a pretreatment, 100.0 mg of the toner particles are subjected to acid decomposition using 8.00 ml of 60% nitric acid (manufactured by Kanto Chemical, for atomic absorption analysis).
During acid decomposition, the sample is treated in a sealed container at an internal temperature of 220° C. for 1 hour using a microwave high-power sample pretreatment device ETHOS1600 (Milestone General Co., Ltd.) to prepare a polyvalent metal element-containing solution sample.
Then, ultrapure water is added to make the total weight 50.00 g to obtain the measurement sample. A calibration curve is created for each polyvalent metal element, and the amount of metal contained in each sample is quantified. Note that ultrapure water is added to 8.00 ml of nitric acid to make a total weight of 50.00 g, and the blank metal amount is subtracted from the blank metal amount.

<Identification of wax in toner>
(1) Method of Separating Wax from Toner Although the wax in the toner can be measured even when it is in the form of a toner, it is more preferable to carry out a separation operation.
First, the melting point of the wax in the toner is measured using a thermal analyzer (DSC Q2000, manufactured by TA Instruments Japan, Inc.). Approximately 3.0 mg of the toner sample is placed in a sample container in an aluminum pan (KIT NO. 0219-0041), the sample container is placed on a holder unit, and set in an electric furnace. In a nitrogen atmosphere, the sample is heated from 30°C to 200°C at a temperature increase rate of 10°C/min, and a DSC curve is measured using a differential scanning calorimeter (DSC), and the melting point of the wax in the toner sample is calculated.
Next, the toner is dispersed in ethanol, which is a poor solvent for the toner, and the temperature is raised to a temperature above the melting point of the wax. At this time, pressure may be applied if necessary. By this operation, the wax that has exceeded its melting point is melted and extracted into the ethanol. The wax can be separated from the toner by heating and, if pressure is applied, by performing solid-liquid separation while still under pressure. Next, the extracted liquid is dried and solidified to obtain the wax.

(2) Identification of wax by pyrolysis GCMS Specific conditions for identifying wax by pyrolysis GCMS are shown below.
Mass spectrometer: ThermoFisher Scientific ISQ
GC equipment: ThermoFisher Scientific FocusGC
Ion source temperature: 250° C.
Ionization method: EI
Mass range: 50-1000 m/z
Column: HP-5MS [30 m]
Pyrolysis equipment: Japan Analytical Industry Co., Ltd. JPS-700
A small amount of the wax separated by the extraction operation and 1 μL of tetramethylammonium hydroxide (TMAH) are added to a pyrofoil at 590°C. The prepared sample is subjected to pyrolysis GCMS measurement under the above conditions to obtain a peak derived from the wax. If the wax is an ester compound, peaks are obtained for the alcohol component and the carboxylic acid component. Due to the action of TMAH, a methylating agent, the alcohol component and the carboxylic acid component are detected as methylated products. The molecular weight can also be obtained by analyzing the obtained peaks and identifying the structure of the ester compound.

<Method of Measuring Weight Average Particle Size (D4) of Toner>
The weight average particle diameter (D4) of the toner is calculated as follows.
The measuring device used is a precision particle size distribution measuring device using a capillary electrical resistance method equipped with a 100 μm aperture tube, “Coulter Counter Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.).
The measurement conditions are set and the measurement data is analyzed using the accompanying dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.) The measurement is performed with an effective measurement channel count of 25,000 channels.
The aqueous electrolyte solution used for the measurement is prepared by dissolving special grade sodium chloride in ion-exchanged water to a concentration of 1.0%, for example, "ISOTON II" (manufactured by Beckman Coulter, Inc.).

Before performing measurements and analysis, the dedicated software is set up as follows.
On the "Change standard measurement method (SOMME)" screen of the dedicated software, set the total count number in the control mode to 50,000 particles, the number of measurements to 1, and the Kd value to the value obtained using "Standard particle 10.0 μm" (manufactured by Beckman Coulter, Inc.). Press the "Threshold/Noise level measurement button" to automatically set the threshold and noise level. Also, set the current to 1,600 μA, the gain to 2, the electrolyte to ISOTON II, and check "Flush aperture tube after measurement."
In the "Pulse to particle size conversion setting" screen of the dedicated software, the bin interval is set to logarithmic particle size, the particle size bin is set to 256 particle size bins, and the particle size range is set to 2 μm to 60 μm.

The specific measurement method is as follows.
(1) Pour 200.0 mL of the electrolyte solution into a 250 mL round-bottom glass beaker made exclusively for the Multisizer 3, set it on the sample stand, and stir the stirrer rod counterclockwise at 24 revolutions per second. Then, remove dirt and air bubbles from inside the aperture tube using the "aperture tube flush" function of the dedicated software.
(2) 30.0 mL of the aqueous electrolyte solution is placed in a 100 mL flat-bottom glass beaker, and 0.3 mL of a dilution of "Contaminon N" (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) diluted 3 times by mass with ion-exchanged water is added as a dispersant.
(3) Prepare an ultrasonic disperser "Ultrasonic Dispersion System Tetra150" (manufactured by Nikkaki Bios Co., Ltd.) that has two built-in oscillators with an oscillation frequency of 50 kHz and a phase shift of 180 degrees and an electrical output of 120 W. Place 3.3 L of ion-exchanged water in the water tank of the ultrasonic disperser, and add 2.0 mL of Contaminon N to this water tank.
(4) The beaker from (2) above is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid surface of the electrolytic solution in the beaker is maximized.
(5) While the electrolyte solution in the beaker in (4) is being irradiated with ultrasonic waves, 10 mg of toner or the like is added little by little to the electrolyte solution and dispersed. Then, ultrasonic dispersion treatment is continued for another 60 seconds. During ultrasonic dispersion, the water temperature in the water tank is appropriately adjusted to be 10°C or higher and 40°C or lower.
(6) Using a pipette, the electrolytic solution (5) in which the toner or the like is dispersed is dropped into the round-bottom beaker (1) placed in the sample stand, and the measurement concentration is adjusted to 5%. Then, the measurement is continued until the number of particles measured reaches 50,000.
(7) The measurement data is analyzed using the dedicated software that comes with the device, and the weight-average particle size (D4) is calculated. Note that when the dedicated software is set to Graph/Volume %, the "Average diameter" on the "Analysis/Volume Statistics (Arithmetic Mean)" screen is the weight-average particle size (D4).

(Example)
The photoreceptor and toner according to the present invention will be described in detail below using examples and comparative examples. In the following description of the examples, "parts" are by weight unless otherwise specified.

An example of the production of a photoreceptor will now be described.
<Production Examples of Titanium Oxide Particles 1 to 3>
The titanium oxide particles contained in the surface protective layer of the present invention preferably have an anatase degree of 90 to 100%, and titanium oxide particles having an anatase degree of nearly 100% can be prepared by the following method.
Here, the degree of anatase is a value calculated by measuring the intensity IA of the strongest interference ray of anatase (plane index 101) and the intensity IR of the strongest interference ray of rutile (plane index 110) in powder X-ray diffraction of titanium oxide particles, and using the following formula:
Anatase degree (%)=100/(1+1.265×IR/IA)
In the present invention, a solution containing titanyl sulfate was heated to hydrolyze the slurry of hydrous titanium dioxide, which was then dehydrated and fired to obtain anatase-type titanium dioxide particles. The concentration of the titanyl sulfate solution was controlled to control the number-average particle size of the anatase-type titanium dioxide particles, and titanium dioxide particles 1 having a number-average particle size of 150 nm, titanium dioxide particles 2 having a number-average particle size of 160 nm, and titanium dioxide particles 3 having a number-average particle size of 130 nm were obtained.

<Production Example of Niobium Atom-Containing Titanium Oxide Particles 1>
100 g of titanium oxide particles 1 were dispersed in water, and heated to 60° C. as 1 L of water suspension. A titanium niobate solution (mass ratio of niobium to titanium in the solution is 1.0/33.7) in which niobium solution in which 3 g of niobium pentachloride (NbCl ₅ ) was dissolved in 100 mL of 11.4 mol/L hydrochloric acid and 600 mL of titanium sulfate solution containing 33.7 g of titanium were mixed and a 10.7 mol/L aqueous sodium hydroxide solution was added dropwise (parallel addition) over 3 hours so that the pH of the suspension was 2 to 3. After the dropwise addition was completed, the suspension was filtered, washed, and dried at 110° C. for 8 hours. The dried product was subjected to a heat treatment (calcination treatment) at 800° C. for 1 hour in an air atmosphere to obtain niobium atom-containing titanium oxide particles 1 in which niobium atoms were unevenly distributed near the surface. Table 1 shows the physical properties of the niobium atom-containing titanium oxide particles 1.

<Production Example of Niobium Atom-Containing Titanium Oxide Particles 2>
Niobium atom-containing titanium oxide particles 2 were obtained in the same manner as in the production of niobium atom-containing titanium oxide particles 1, except that titanium oxide particles 1 were changed to titanium oxide particles 2 and the coating conditions were appropriately changed. Table 1 shows the physical properties of niobium atom-containing titanium oxide particles 2.

<Production Example of Niobium Atom-Containing Titanium Oxide Particles 3>
Niobium sulfate (a water-soluble niobium compound) was added to a hydrous titanium dioxide slurry obtained by hydrolysis of an aqueous titanyl sulfate solution in an amount of 0.20 mass% in terms of niobium ions relative to the amount of titanium in the slurry (calculated as titanium dioxide).
The above was hydrolyzed and dehydrated, and then calcined at a calcination temperature of 1000° C. As a result, anatase type titanium oxide particles (niobium atom-containing titanium oxide particles before coating) containing 0.20 mass % of niobium atoms and having a number average particle size of 150 nm were obtained.
Niobium atom-containing titanium oxide particles 3 were obtained in the same manner as in the production of niobium atom-containing titanium oxide particles 1, except that titanium oxide particles 1 were replaced with the above niobium atom-containing titanium oxide particles and the coating conditions were appropriately changed. The obtained niobium atom-containing titanium oxide particles 3 were particles in which niobium atoms were present also inside the particles. Table 1 shows the physical properties of niobium atom-containing titanium oxide particles 3.

<Production Examples of Niobium Atom-Containing Titanium Oxide Particles 4 to 9>
Niobium atom-containing titanium oxide particles 4 to 9 were obtained in the same manner as in the production of niobium atom-containing titanium oxide particles 3, except that the titanyl sulfate aqueous solution was changed to change the number average particle size of the niobium atom-containing titanium oxide particles before coating and that the conditions for coating were appropriately changed. Table 1 shows the physical properties of niobium atom-containing titanium oxide particles 4 to 9.

<Production Example of Niobium Atom-Containing Titanium Oxide Particles 10>
Niobium atom-containing titanium oxide particles 10 were obtained in the same manner as in the production of niobium atom-containing titanium oxide particles 3, except that the amount of niobium ions was changed and that a niobium solution prepared by dissolving 3 g of niobium pentachloride (NbCl ₅ ) in 100 mL of 11.4 mol/L hydrochloric acid was not used during coating. Table 1 shows the physical properties of niobium atom-containing titanium oxide particles 10.

<Niobium Atom-Containing Titanium Oxide Particles 11>
Niobium atom-containing titanium oxide particles 11 were obtained in the same manner as in the production of niobium atom-containing titanium oxide particles 3, except that the concentration of the titanyl sulfate aqueous solution and the amount of niobium ions were changed and no coating was performed. Table 1 shows the physical properties of the niobium atom-containing titanium oxide particles 11.

これらを、トルエン２００．０部に混合し、攪拌装置で４時間攪拌した後、ろ過、洗浄後、さらに１３０℃で３時間加熱処理を行った。このようにして表面処理を行い、導電性粒子１を得た。導電性粒子１の物性を表２に示す。なお、表２中のニオブ原子含有量は、導電性粒子におけるニオブ原子の含有量であり、蛍光Ｘ線による元素分析法（ＸＲＦ）により測定して得た値である。 <Production Example of Conductive Particle 1>
The following materials were prepared:
Niobium atom-containing titanium oxide particles 1 (specific gravity: 4 g/cm ³ ) 100.0 parts; A compound represented by the following formula (S-1) as a silane coupling agent (product name: KBM-3033, manufactured by Shin-Etsu Chemical Co., Ltd.) 3.0 parts:

These were mixed with 200.0 parts of toluene, stirred with a stirrer for 4 hours, filtered, washed, and then heat-treated at 130° C. for 3 hours. Surface treatment was performed in this manner to obtain conductive particles 1. The physical properties of conductive particles 1 are shown in Table 2. The niobium atom content in Table 2 is the content of niobium atoms in the conductive particles, and is a value obtained by measurement using X-ray fluorescence elemental analysis (XRF).

表中、Ａは、「粒子表面から粒子の最大径の５％内部におけるニオブ原子とチタン原子との濃度比率」であり、Ｂは、「粒子中心部におけるニオブ原子とチタン原子との濃度比率」である。

In the table, A is the "concentration ratio of niobium atoms to titanium atoms within 5% of the maximum diameter of the particle from the particle surface," and B is the "concentration ratio of niobium atoms to titanium atoms in the particle center."

<Production Examples of Conductive Particles 2 to 6 and 8 to 13>
Conductive particles 2 to 6 and 8 to 13 were obtained in the same manner as in the production example of conductive particle 1, except that the niobium atom-containing titanium oxide particles used in the production example of conductive particle 1 were changed as shown in Table 2 and the conditions for the surface treatment were appropriately changed. The physical properties of conductive particles 2 to 6 and 8 to 13 are shown in Table 2.

これらを、トルエン２００．０部に混合し、攪拌装置で４時間攪拌した後、ろ過、洗浄後、さらに１３０℃で３時間加熱処理を行った。このようにして、導電性粒子７を得た。導電性粒子７の物性を表２に示す。 <Production Example of Conductive Particles 7>
The following materials were prepared:
Tin oxide particles (product name: S-2000, manufactured by Mitsubishi Materials Corporation, number average particle size 100 nm) 100.0 parts Compound represented by formula (S-2) 20.0 parts

These were mixed with 200.0 parts of toluene, stirred with a stirrer for 4 hours, filtered, washed, and then heat-treated at 130° C. for 3 hours. In this way, conductive particles 7 were obtained. The physical properties of conductive particles 7 are shown in Table 2.

<Production Example of Electrophotographic Photoreceptor 1>
An aluminum cylinder (JIS-A3003, aluminum alloy) having a diameter of 24 mm and a length of 257.5 mm was used as a support (conductive support).

(Example of the production of conductive layer)
Next, the following materials were prepared:
214.0 parts of titanium oxide (TiO ₂ ) particles (number average particle size 230 nm) coated with oxygen-deficient tin oxide (SnO ₂ ) as metal oxide particles; 132.0 parts of phenolic resin (monomer/oligomer of phenolic resin) as binding material (product name: Plyofen J-325, manufactured by DIC Corporation, resin solid content: 60% by mass); 98.0 parts of 1-methoxy-2-propanol as solvent. These were placed in a sand mill using 450.0 parts of glass beads with a diameter of 0.8 mm, and dispersion treatment was carried out under the conditions of rotation speed: 2000 rpm, dispersion treatment time: 4.5 hours, and cooling water temperature setting: 18°C, to obtain a dispersion. The glass beads were removed from this dispersion using a mesh (mesh size: 150 μm).
Silicone resin particles (trade name: Tospearl 120, manufactured by Momentive Performance Materials, Inc., average particle size 2 μm) were added as a surface roughening agent to the obtained dispersion. The amount of silicone resin particles added was 10% by mass relative to the total mass of the metal oxide particles and the binding material in the dispersion after removing the glass beads. Silicone oil (trade name: SH28PA, manufactured by Dow Corning Toray Co., Ltd.) was added as a leveling agent to the dispersion so as to be 0.01% by mass relative to the total mass of the metal oxide particles and the binding material in the dispersion.
Next, a mixed solvent of methanol and 1-methoxy-2-propanol (mass ratio 1:1) was added to the dispersion so that the total mass of the metal oxide particles, the binder material, and the surface roughening agent in the dispersion (i.e., the mass of the solid content) was 67 mass% relative to the mass of the dispersion. Thereafter, the mixture was stirred to prepare a coating liquid for a conductive layer.
This conductive layer coating liquid was dip-coated onto the support and heated at 140° C. for 1 hour to form a conductive layer having a thickness of 30 μm.

(Example of preparation of undercoat layer)
Next, the following materials were prepared:
3.1 parts of electron transport material represented by the following formula (E-1) 6.5 parts of blocked isocyanate (product name: Duranate SBB-70P, manufactured by Asahi Kasei Chemicals Corporation) 0.40 parts of styrene-acrylic resin (product name: UC-3920, manufactured by Toagosei Co., Ltd.) 1.8 parts of silica slurry (product name: IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid content concentration: 15% by mass, viscosity: 9 mPa·s) These were dissolved in a mixed solvent of 48.0 parts of 1-butanol and 24.0 parts of acetone to prepare an undercoat layer coating liquid. This undercoat layer coating liquid was dip-coated on the conductive layer and heated at 170° C. for 30 minutes to form an undercoat layer having a film thickness of 0.7 μm.

(Example of the production of the photosensitive layer)
Next, 10.0 parts of hydroxygallium phthalocyanine in a crystalline form having peaks at 7.5° and 28.4° in a chart obtained by CuKα characteristic X-ray diffraction and 5 parts of polyvinyl butyral resin (product name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.) were prepared.
These were added to 200.0 parts of cyclohexanone and dispersed for 6 hours in a sand mill using glass beads with a diameter of 0.9 mm, and then diluted with 150.0 parts of cyclohexanone and 350.0 parts of ethyl acetate to obtain a coating liquid for a charge generating layer.
The resulting coating liquid was dip-coated on the undercoat layer and dried at 95° C. for 10 minutes to form a charge generating layer having a thickness of 0.20 μm.

The X-ray diffraction measurements were carried out under the following conditions.
[Powder X-ray diffraction measurement]
Measuring equipment used: Rigaku Electric Co., Ltd., X-ray diffraction device RINT-TTRII
X-ray tube: Cu
Tube voltage: 50KV
Tube current: 300mA
Scan method: 2θ/θ scan Scan speed: 4.0°/min
Sampling interval: 0.02°
Start angle (2θ): 5.0°
Stop angle (2θ): 40.0°
Attachment: Standard sample holder Filter: Not used Incident monochrome: Used Counter monochromator: Not used Divergence slit: Open Divergence vertical limit slit: 10.00 mm
Scattering slit: open Receiving slit: open Flat plate monochromator: Counter used: Scintillation counter

Next, the following materials were prepared:
6.0 parts of charge transport material (hole transport material) represented by the following formula (C-1) 3.0 parts of charge transport material (hole transport material) represented by the following formula (C-2) 1.0 part of charge transport material (hole transport material) represented by the following formula (C-3) 10.0 parts of polycarbonate (product name: Iupilon Z400, manufactured by Mitsubishi Engineering Plastics Corporation) 0.02 parts of polycarbonate resin (x/y=0.95/0.05: viscosity average molecular weight=20000) having copolymerized units represented by the following formulas (C-4) and (C-5) These were dissolved in a mixed solvent of 25.0 parts of orthoxylene/25.0 parts of methyl benzoate/25.0 parts of dimethoxymethane to prepare a coating solution for the charge transport layer. This charge transport layer coating liquid was dip coated onto the charge generating layer to form a coating film, and the coating film was dried at 120° C. for 30 minutes to form a charge transport layer having a thickness of 12 μm.

・導電性粒子として導電性粒子１：４．０部
これらを、１－プロパノール５．０部／シクロヘキサン５．０部の混合溶媒に混合し、攪拌装置で６時間攪拌した。このようにして、保護層用塗布液を調製した。
この保護層用塗布液を電荷輸送層上に浸漬塗布して塗膜を形成し、得られた塗膜を６分間５０℃で乾燥させた。その後、窒素雰囲気下にて、加速電圧７０ｋＶ、ビーム電流５．０ｍＡの条件で支持体（被照射体）を３００ｒｐｍの速度で回転させながら、１．６秒間電子線を塗膜に照射した。保護層位置の線量は１５ｋＧｙであった。
その後、窒素雰囲気下にて、塗膜の温度を１１７℃に昇温させた。電子線照射から、その後の加熱処理までの酸素濃度は１０ｐｐｍであった。
次に、大気中において塗膜の温度が２５℃になるまで自然冷却した後、塗膜の温度が１２０℃になる条件で１時間加熱処理を行い、膜厚２μｍの表面保護層を形成した。
このようにして、電子写真感光体１を製造した。電子写真感光体の１の物性を表３に示す。 (Example of manufacturing the surface protective layer)
Next, the following materials were prepared:
A compound represented by the following structural formula (O-1) as a binder resin: 1.0 part

Conductive particles: 1: 4.0 parts These were mixed in a mixed solvent of 5.0 parts 1-propanol/5.0 parts cyclohexane, and stirred for 6 hours with a stirrer. In this way, a coating solution for a protective layer was prepared.
The protective layer coating liquid was dip-coated on the charge transport layer to form a coating film, and the resulting coating film was dried at 50° C. for 6 minutes. Thereafter, the coating film was irradiated with an electron beam for 1.6 seconds under a nitrogen atmosphere while rotating the support (irradiation target) at a speed of 300 rpm under conditions of an acceleration voltage of 70 kV and a beam current of 5.0 mA. The dose at the protective layer position was 15 kGy.
Thereafter, in a nitrogen atmosphere, the temperature of the coating film was raised to 117° C. The oxygen concentration from the electron beam irradiation to the subsequent heat treatment was 10 ppm.
Next, the coating film was naturally cooled in the atmosphere until the temperature of the coating film reached 25° C., and then heat-treated for 1 hour under conditions such that the temperature of the coating film reached 120° C., to form a surface protective layer with a thickness of 2 μm.
In this manner, electrophotographic photoreceptor 1 was produced. The physical properties of electrophotographic photoreceptor 1 are shown in Table 3.

<Production Examples of Electrophotographic Photoreceptors 2 to 6, 8 to 13, 15, and 16>
Electrophotographic photoreceptors 2 to 6, 8 to 13, 15, and 16 were produced in the same manner as in Production Example of Electrophotographic Photoreceptor 1, except that the type and content (volume %) of the conductive particles used in (Production Example of Surface Protective Layer) in Production Example of Electrophotographic Photoreceptor 1 were changed as shown in Table 3. The physical properties of electrophotographic photoreceptors 2 to 6, 8 to 13, 15, and 16 are shown in Table 3.

<Production Example of Electrophotographic Photoreceptor 7>
An electrophotographic photoreceptor 7 was obtained in the same manner as in the production example of the electrophotographic photoreceptor 1, except that (production example of the surface protective layer) was changed as follows.
A coating solution for a surface protective layer was prepared as follows.
First, the following materials were prepared:
Conductive particles 5: 16.0 parts Compound represented by the following formula (H-7): 10.0 parts Polymerization initiator (1-hydroxycyclohexyl(phenyl)methanone): 1.0 part These were mixed with 40 parts of n-propyl alcohol and dispersed in a sand mill for 2 hours to prepare a coating solution for the protective layer.
Except for using this protective layer coating liquid, electrophotographic photoreceptor 7 was produced in the same manner as in electrophotographic photoreceptor 1. The physical properties of electrophotographic photoreceptor 7 are shown in Table 3.

<Production Example of Electrophotographic Photoreceptor 14>
An electrophotographic photoreceptor 14 was obtained in the same manner as in the production example of the electrophotographic photoreceptor 7, except that the amount of the conductive particles 5 added in (production example of the surface protective layer) was changed to 10.0 parts by mass in the production example of the electrophotographic photoreceptor 7. The physical properties of the electrophotographic photoreceptor 14 are shown in Table 3.

これらをテトラヒドロフラン１００．０部に混合し、攪拌装置で６時間攪拌し、これにより保護層用塗布液を調製した。
この保護層用塗布液を窒素気流中でスプレー塗工法により電荷輸送層上に塗布して塗膜を形成し、１０分間窒素気流中に放置して、乾燥した。その後、酸素濃度が２％以下となるようにブース内を窒素ガスで置換した紫外線光照射ブースにて、紫外線照射を以下の条件で行った。
メタルハライドランプ：１６０Ｗ／ｃｍ
照射距離：１２０ｍｍ
照射強度：７００ｍＷ／ｃｍ^２
照射時間：６０秒
さらに、１３０℃で２０分間乾燥することで、膜厚が５μｍの表面保護層を形成した。
このようにして、電子写真感光体１７を得た。電子写真感光体１７の物性を表３に示す。 <Production Example of Electrophotographic Photoreceptor 17>
An electrophotographic photoreceptor 17 was obtained in the same manner as in the production example of the electrophotographic photoreceptor 1, except that (production example of the surface protective layer) in the production example of the electrophotographic photoreceptor 1 was changed as follows.
A coating solution for a surface protective layer was prepared as follows.
First, the following materials were prepared:
Radical polymerizable monomer (product name: TMPTA, manufactured by Tokyo Chemical Industry Co., Ltd.) 10.0 parts; Compound represented by the following formula (H-1) 5 parts; Compound represented by the following formula (H-2) 0.15 parts; Compound represented by the following formula (H-3) 0.15 parts; Fluororesin particles (product name: MPE-056, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) 1.5 parts; Photopolymerization initiator (product name: Irgacure 184, manufactured by BASF Japan Co., Ltd.) 0.75 parts

These were mixed with 100.0 parts of tetrahydrofuran and stirred for 6 hours with a stirrer to prepare a coating solution for the protective layer.
The protective layer coating solution was applied on the charge transport layer by spray coating in a nitrogen gas flow to form a coating film, which was then left in a nitrogen gas flow for 10 minutes to dry. Thereafter, ultraviolet light was irradiated under the following conditions in an ultraviolet light irradiation booth in which the inside of the booth was replaced with nitrogen gas so that the oxygen concentration was 2% or less.
Metal halide lamp: 160 W/cm
Irradiation distance: 120 mm
Irradiation intensity: 700mW/ ^cm2
Irradiation time: 60 seconds. Further, the coating was dried at 130° C. for 20 minutes to form a surface protective layer with a thickness of 5 μm.
In this manner, an electrophotographic photoreceptor 17 was obtained. The physical properties of the electrophotographic photoreceptor 17 are shown in Table 3.

An example of toner production will now be described.
<Preparation Example of Binder Resin Particle Dispersion>
78.0 parts of styrene, 20.7 parts of butyl acrylate, 1.3 parts of acrylic acid as a carboxyl group-imparting monomer, and 3.2 parts of n-lauryl mercaptan were mixed and dissolved in the solution, and an aqueous solution of 1.5 parts of NEOGEN RK (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) in 150.0 parts of ion-exchanged water was added to the solution and dispersed.
An aqueous solution of 0.3 parts of potassium persulfate and 10.0 parts of ion-exchanged water was added while slowly stirring for another 10 minutes. After nitrogen replacement, emulsion polymerization was carried out for 6 hours at 70° C. After the polymerization was completed, the reaction solution was cooled to room temperature, and ion-exchanged water was added to obtain a resin particle dispersion 1 having a solid content of 12.5% by mass and a volume-based median diameter of 0.2 μm.
A part of the obtained resin particles was washed with pure water to remove the surfactant and dried under reduced pressure in order to measure the acid value. The acid value of the resin was measured and found to be 9.5 mgKOH/g.

<Preparation Example of Release Agent Dispersion 1>
100.0 parts of behenyl behenate (melting point: 72.1° C.) and 15.0 parts of NEOGEN RK were mixed with 385.0 parts of ion-exchanged water, and dispersed for about 1 hour using a wet jet mill JN100 (manufactured by Jokou Co., Ltd.) to obtain a release agent dispersion 1. The wax concentration of the release agent dispersion 1 was 20.0% by mass.

<Preparation Example of Release Agent Dispersion 2>
100.0 parts of pentaerythritol tetrabehenate (melting point: 84.2° C.) and 15 parts of NEOGEN RK were mixed with 385.0 parts of ion-exchanged water, and dispersed for about 1 hour using a wet jet mill JN100 (manufactured by Jokou Co., Ltd.) to obtain a release agent dispersion 2. The wax concentration of the release agent dispersion 2 was 20.0% by mass.

<Preparation Example of Release Agent Dispersion 3>
100.0 parts of a hydrocarbon wax HNP-9 (manufactured by Nippon Seiro Co., Ltd., melting point: 75.5° C.) and 15 parts of NEOGEN RK were mixed with 385.0 parts of ion-exchanged water, and dispersed for about 1 hour using a wet jet mill JN100 (manufactured by Jokou Co., Ltd.) to obtain a release agent dispersion 3. The wax concentration of the release agent dispersion 3 was 20.0% by mass.

<Preparation Example of Colorant Dispersion>
As a colorant, 100.0 parts of carbon black "Nipex 35 (manufactured by Orion Engineered Carbons)" and 15 parts of Neogen RK were mixed with 885.0 parts of ion-exchanged water, and dispersed for about 1 hour using a wet jet mill JN100 to obtain a colorant dispersion.

<Production Example of Silica Particles 1>
Untreated dry silica having a primary particle number average particle size of 18 nm was placed in a reactor equipped with a stirrer and heated to 200° C. in a fluidized state by stirring.
The inside of the reactor is replaced with nitrogen gas, the reactor is sealed, 25.0% by mass of dimethyl silicone oil (viscosity= ^100mm2 /sec) is sprayed to 100.0% by mass of dry silica, and stirring is continued for 30 minutes.Then, the temperature is raised to 300°C while stirring, and after stirring for another 2 hours, the mixture is taken out and crushed to obtain silica particles 1.The hydrophobicity of silica particles 1 is 94.0%.

<Production Example of Toner 1>
265.0 parts of the resin particle dispersion, 10.0 parts of the release agent dispersion 1, and 10.0 parts of the colorant dispersion were dispersed using a homogenizer (Ultra Turrax T50 manufactured by IKA Corporation). The temperature inside the container was adjusted to 30° C. while stirring, and a 1 mol/L aqueous sodium hydroxide solution was added to adjust the pH to 8.0.
As a flocculant, an aqueous solution of 0.25 parts of aluminum chloride dissolved in 10.0 parts of ion-exchanged water was added over 10 minutes under stirring at 30°C. After leaving it for 3 minutes, the temperature was raised to 50°C to generate associated particles. In this state, the particle size of the associated particles was measured using a "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.). When the weight average particle size reached 6.0 μm, 0.90 parts of sodium chloride and 5.0 parts of Neogen RK were added to stop particle growth.
A 1 mol/L aqueous solution of sodium hydroxide was added to adjust the pH to 9.0, and the temperature was then raised to 95° C. to spheronize the aggregated particles. When the average circularity reached 0.980, the temperature was lowered and the mixture was cooled to room temperature, thereby obtaining toner particle dispersion 1.
Hydrochloric acid was added to the obtained toner particle dispersion 1 to adjust the pH to 1.5 or less, and the mixture was left to stir for 1 hour, and then the mixture was subjected to solid-liquid separation using a pressure filter to obtain a toner cake. This was reslurried with ion-exchanged water to make a dispersion again, and then the mixture was subjected to solid-liquid separation using the above-mentioned filter. The reslurry and solid-liquid separation were repeated until the electrical conductivity of the filtrate became 5.0 μS/cm or less, and finally the mixture was subjected to solid-liquid separation to obtain a toner cake. The obtained toner cake was dried and further classified using a classifier so that the weight average particle size (D4) was 6.0 μm, and toner particles 1 were obtained.
Toner particles 1 (100.0 parts) obtained above were externally mixed with silica particles 1 (1.0 part) using FM10C (manufactured by Nippon Coke and Engineering Co., Ltd.) The external addition conditions were as follows: the lower blade was set to A0 blade, the gap between the blade and the wall of the deflector was set to 20 mm, the amount of toner particles charged was 2.0 kg, the rotation speed was 66.6 s ^-1 , the external addition time was 10 minutes, and the cooling water temperature was 20°C and the flow rate was 10 L/min.
Thereafter, the mixture was sieved through a mesh having an opening of 200 μm to obtain toner 1. Table 4 shows the physical properties of toner 1 obtained.

<Production Example of Toner 2>
Toner 2 was obtained in the same manner as in the production example of toner 1, except that release agent dispersion liquid 2 was used. Table 4 shows the physical properties of toner 2 obtained.

<Production Example of Toner 3>
Toner 3 was obtained in the same manner as in the production example of toner 1, except that release agent dispersion liquid 3 was used. Table 4 shows the physical properties of toner 3 obtained.

<Production Examples of Toners 4 to 6 and 15>
Toners 4 to 6 and 15 were obtained in the same manner as in the production example of Toner 1, except that the amount of aluminum chloride added as an aggregating agent was changed as shown in Table 4. Table 4 shows the physical properties of Toners 4 to 6 and 15 obtained.

<Production Examples of Toners 7 to 9>
Toners 7 to 9 were obtained in the same manner as in the production example of Toner 1, except that the aluminum chloride added as the coagulant was changed to magnesium chloride and the amount of addition was changed as shown in Table 4. Table 4 shows the physical properties of the obtained Toners 7 to 9.

<Production Examples of Toners 10 and 11>
Toners 10 and 11 were obtained in the same manner as in the production example of Toner 1, except that aluminum chloride added as an aggregating agent was changed to calcium chloride and the amount of addition was changed as shown in Table 4. Table 4 shows the physical properties of the obtained Toners 10 and 11.

<Production Examples of Toners 12 to 14 and 16>
Toners 12 to 14 and 16 were obtained in the same manner as in the production example of Toner 1, except that aluminum chloride added as a coagulant was changed to iron (III) chloride and the amount of addition was changed as shown in Table 4. Table 4 shows the physical properties of the obtained Toners 12 to 14 and 16.

Example 1
A commercially available color laser printer, HP LaserJet Enterprise Color m553dn, was partially modified for evaluation. The modification involved modifying the process speed of the main body to 300 mm/sec, and making necessary adjustments so that image formation was possible under these conditions.
In addition, the toner was removed from the black toner cartridge and replaced with Toner 1: 320 g. Furthermore, the photoconductor was changed to Photoconductor 1 of the present invention. This toner cartridge was installed in the black station, and dummy cartridges were installed in the other stations, and the following image output test was carried out. The results of the following evaluations 1 to 3 are shown in Table 5.

(Evaluation 1: Gradation evaluation under high temperature and high humidity environment)
An office 70 (Canon) was set as a medium in the printer, and 10,000 sheets of a character pattern image with a printing rate of 1% were printed at 30.0° C./80% RH. At this time, the printing was performed in a mode in which the machine was stopped between jobs and the next job was started, with 2 sheets per job.
After passing the paper, images of patterns 1 to 8 having the image density gradations shown in FIG. 3 were output, and the image density was measured and evaluated using an X-Rite color reflection densitometer (X-Rite 404A).
In this evaluation, an image was output in black alone. From the viewpoint of gradation reproducibility, it is preferable that the density range of each pattern image is within the following range, and the evaluation was performed from this viewpoint.
Pattern 1: 0.10 or more and less than 0.15 Pattern 2: 0.15 or more and less than 0.20 Pattern 3: 0.20 or more and less than 0.30 Pattern 4: 0.25 or more and less than 0.40 Pattern 5: 0.55 or more and less than 0.70 Pattern 6: 0.65 or more and less than 0.80 Pattern 7: 0.75 or more and less than 0.90 Pattern 8: 1.40 or more
(Evaluation criteria)
A: All pattern images satisfy the above density range.
B: One pattern image falls outside the above density range.
C: Two pattern images are outside the above density range.
D: Three or more pattern images are outside the above density range.
E: Four or more pattern images are outside the above density range.
In this case, the effect is recognized to be achieved up to level D.

(Evaluation 2: Capri evaluation under high temperature and humidity conditions)
XEROX 4200 paper (75 g/ ^m2 manufactured by XEROX) was set as the media in the printer described above, and an all-white image was output at 30.0°C/80% RH using the paper with a sticky note attached to part of the printed surface of the image to mask it (white image 1). Then, 10,000 sheets of a character pattern image with a print rate of 1% were printed. At this time, the paper was printed in a mode set to 2 sheets/1 job, where the machine stopped between jobs before starting the next job. After printing the 10,000 sheets, the printer was left for 3 days, and then another all-white image was output using the paper with a sticky note attached to part of the printed surface of the image to mask it (white image 2).
For white image 1, after removing the sticky note, the reflectance (%) was measured at five points for the part with the sticky note and the part without the sticky note, and the average value was calculated. The difference between the average values was then calculated and this was regarded as the initial fog.
Similarly, the difference in the average values was calculated for white image 2, and this was taken as the fog after durability testing. The difference between the initial fog and the fog after durability testing was calculated, and the fog after durability testing was evaluated according to the following evaluation criteria.
The reflectance was measured using a digital white light photometer (TC-6D, manufactured by Tokyo Denshoku Co., Ltd., using a green filter).
(Evaluation criteria)
A: The fog difference between the initial stage and after the durability test is less than 0.5%. B: The fog difference between the initial stage and after the durability test is 0.5% or more and less than 1.5%. C: The fog difference between the initial stage and after the durability test is 1.5% or more and less than 2.5%. D: The fog difference between the initial stage and after the durability test is 2.5% or more. In this case, the level up to C is recognized as having an effect.

(Evaluation 3: Fog evaluation in a low temperature and low humidity environment)
The fogging after continuous use in a low temperature and low humidity environment (15° C./10% RH) was evaluated. XEROX 4200 paper (75 g/m ² manufactured by XEROX Corporation) was used as the evaluation paper.
In a low temperature and low humidity environment, a completely white image was output using paper with a sticky note attached to a part of the printed surface of the image as a mask (white image 3). After that, 10,000 sheets of a character pattern image with a print rate of 1% were passed through. At this time, the paper was passed through in a mode set to 2 sheets/1 job, where the machine stopped between jobs before starting the next job. After that, a completely white image was output again using paper with a sticky note attached to a part of the printed surface of the image as a mask (white image 4).
For white image 3, after removing the sticky note, the reflectance (%) was measured at five points for the part with the sticky note and the part without the sticky note, and the average value was calculated. The difference between the average values was then calculated and this was regarded as the initial fog.
Similarly, the difference in the average values was calculated for white image 4, and this was taken as the fog after durability testing. The difference between the initial fog and the fog after durability testing was calculated, and the fog after durability testing was evaluated according to the following evaluation criteria.
The reflectance was measured using a digital white light photometer (TC-6D, manufactured by Tokyo Denshoku Co., Ltd., using a green filter).
(Evaluation criteria)
A: The fog difference between the initial stage and after durability is less than 0.5%. B: The fog difference between the initial stage and after durability is 0.5% or more and less than 1.5%. C: The fog difference between the initial stage and after durability is 1.5% or more and less than 2.5%. D: The fog difference between the initial stage and after durability is 2.5% or more. In this case, the level up to C is recognized as having an effect.

<Examples 2 to 26 and Comparative Examples 1 to 6>
An image output test was carried out in the same manner as in Example 1, except that the combination of the electrophotographic photoreceptor and the toner was changed as shown in Table 5, and evaluations 1 to 3 were carried out. The results of the evaluations are shown in Table 5.

The disclosure of this embodiment includes the following configuration.
(Configuration 1)
A process cartridge that is detachably attached to a main body of an electrophotographic apparatus,
The process cartridge comprises:
An electrophotographic photoreceptor;
a developing means having a toner storage section for storing toner and supplying the toner to the surface of the electrophotographic photoreceptor;
having
The electrophotographic photoreceptor has a conductive support, and a photosensitive layer and a surface protective layer formed on the conductive support in this order;
The surface protective layer contains conductive particles,
the content of the conductive particles is 20.0 vol% or more and 70.0 vol% or less of the total volume of the surface protective layer,
the volume resistivity of the surface protective layer is 1.0×10 ⁹ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less;
The toner contained in the toner container has toner particles containing a binder resin and an external additive,
the toner particles have at least one polyvalent metal element selected from the group consisting of aluminum, magnesium, calcium, and iron;
a total content of the polyvalent metal elements in the toner particles, as measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), being 0.10 μmol/g or more and 1.25 μmol/g or less;
(Configuration 2)
Regarding the polyvalent metal element contained in the toner particles,
The aluminum content is 0.50 μmol/g or less,
The magnesium content is 0.80 μmol/g or less,
The calcium content is 0.90 μmol/g or less,
The iron content is 1.25 μmol/g or less,
The total content of these polyvalent metal elements is 0.10 μmol/g or more and 1.25 μmol/g or less.
2. The process cartridge according to claim 1.
(Configuration 3)
the toner particles contain aluminum as the polyvalent metal element in an amount of 0.10 μmol/g or more and 0.32 μmol/g or less;
3. The process cartridge according to claim 1 or 2.
(Configuration 4)
4. The process cartridge according to any one of configurations 1 to 3, wherein the toner particles contain a wax, and the wax is an ester compound.
(Configuration 5)
The process cartridge according to any one of configurations 1 to 4, characterized in that a carboxyl group is present in the molecular chain constituting the binder resin, and the carboxyl group and the polyvalent metal element are present in the toner particles by coordinate bonding.
(Configuration 6)
6. The process cartridge according to any one of configurations 1 to 5, wherein the toner particles are emulsion aggregation toner particles.
(Configuration 7)
7. The process cartridge according to any one of Configurations 1 to 6, wherein the conductive particles are titanium oxide particles.
(Configuration 8)
8. The process cartridge according to claim 7, wherein the titanium oxide particles are niobium atom-containing titanium oxide particles.
(Configuration 9)
The process cartridge according to Configuration 8, wherein the niobium-atom-containing titanium oxide particles have a concentration ratio calculated as niobium atom concentration/titanium atom concentration at a portion within 5% of the maximum diameter of the measured particle from the particle surface, which is 2.0 times or more, relative to a concentration ratio calculated as niobium atom concentration/titanium atom concentration at a center of the particle.
(Configuration 10)
10. The process cartridge according to claim 8, wherein the niobium atom-containing titanium oxide particles contain 2.6% by mass or more and 10.0% by mass or less of niobium atoms.
(Configuration 11)
In the electrophotographic photoreceptor,
The content of the conductive particles is 40.0 vol% or more and 70.0 vol% or less of the surface protective layer,
11. The process cartridge according to any one of configurations 1 to 10, wherein the volume resistivity of the surface protective layer is 1.0×10 ¹⁰ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less.

REFERENCE SIGNS LIST 1 Photoconductor 2 Shaft 3 Charging means 4 Exposure light 5 Toner storage section and developing means 6 Transfer means 7 Transfer material 8 Fixing means 9 Cleaning means 10 Pre-exposure light 11 Process cartridge 12 Guide means

Claims (11)

A process cartridge that is detachably attached to a main body of an electrophotographic apparatus,
The process cartridge comprises:
An electrophotographic photoreceptor;
a developing means having a toner storage section for storing toner and supplying the toner to the surface of the electrophotographic photoreceptor;
having
The electrophotographic photoreceptor has a conductive support, and a photosensitive layer and a surface protective layer formed on the conductive support in this order;
The surface protective layer contains conductive particles,
the content of the conductive particles is 20.0 vol% or more and 70.0 vol% or less of the total volume of the surface protective layer,
the volume resistivity of the surface protective layer is 1.0×10 ⁹ Ω·cm or more and 1.0×10 ¹⁴ Ω·cm or less;
The toner contained in the toner container has toner particles containing a binder resin and an external additive,
the toner particles have at least one polyvalent metal element selected from the group consisting of aluminum, magnesium, calcium, and iron;
a total content of the polyvalent metal elements in the toner particles, as measured by inductively coupled plasma atomic emission spectrometry (ICP-AES), being 0.10 μmol/g or more and 1.25 μmol/g or less; Regarding the polyvalent metal element contained in the toner particles,
The aluminum content is 0.50 μmol/g or less,
The magnesium content is 0.80 μmol/g or less,
The calcium content is 0.90 μmol/g or less,
The iron content is 1.25 μmol/g or less,
The total content of these polyvalent metal elements is 0.10 μmol/g or more and 1.25 μmol/g or less.
2. The process cartridge according to claim 1. the toner particles contain aluminum as the polyvalent metal element in an amount of 0.10 μmol/g or more and 0.32 μmol/g or less;
2. The process cartridge according to claim 1. The process cartridge according to claim 1, wherein the toner particles contain a wax, and the wax is an ester compound. The process cartridge according to claim 1, characterized in that a carboxyl group is present in the molecular chain constituting the binder resin, and the carboxyl group and the polyvalent metal element are present in the toner particles by coordinate bonding. The process cartridge according to claim 1, wherein the toner particles are emulsion aggregation toner particles. The process cartridge according to claim 1, wherein the conductive particles are titanium oxide particles. The process cartridge according to claim 7, wherein the titanium oxide particles are titanium oxide particles containing niobium atoms. The process cartridge according to claim 8, wherein the niobium atom-containing titanium oxide particles have a concentration ratio calculated as niobium atom concentration/titanium atom concentration at the center of the particle, the concentration ratio calculated as niobium atom concentration/titanium atom concentration at an area 5% inside the particle surface from the maximum diameter of the measured particle, which is 2.0 times or more. The process cartridge according to claim 8, wherein the niobium atom-containing titanium oxide particles contain 2.6% by mass or more and 10.0% by mass or less of niobium atoms. In the electrophotographic photoreceptor,
The content of the conductive particles is 40.0 vol% or more and 70.0 vol% or less of the surface protective layer,
2. The process cartridge according to claim 1, wherein the volume resistivity of the surface protective layer is from 1.0×10 ¹⁰ Ω·cm to 1.0×10 ¹⁴ Ω·cm.

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