Electrophotographic device

Abstract

This invention provides an electrophotographic apparatus that features a toner containing strontium titanate as an external additive and a highly durable electrophotographic photoreceptor, resulting in excellent transfer performance even in low-temperature, low-humidity environments. [Solution] An electrophotographic apparatus is provided, comprising: an electrophotographic photoreceptor having a surface layer containing resin X as a binder resin; charging means for charging the surface of the electrophotographic photoreceptor; exposure means for irradiating the charged surface of the electrophotographic photoreceptor with light to form an electrostatic latent image; developing means for supplying toner to the electrostatic latent image to form a toner image; and transfer means for transferring the toner image to a transfer medium, wherein the toner contains strontium titanate as an external additive, and the resin X contains a specific structural unit.

Description

Technical Field

[0001] The present invention relates to an electrophotographic apparatus using an electrophotographic photoreceptor.

Background Art

[0002] As the electrophotographic photoreceptor mounted in an electrophotographic apparatus or a process cartridge, an organic electrophotographic photoreceptor containing an organic photoconductive substance (charge generating substance) (hereinafter, also simply referred to as "electrophotographic photoreceptor" or "photoreceptor") is used. In recent years, longer-life electrophotographic apparatuses have been demanded. Therefore, it is desired to provide an electrophotographic apparatus using an electrophotographic photoreceptor with improved image quality and abrasion resistance (mechanical durability).

[0003] In addition, in recent electrophotographic apparatuses, in addition to coping with the above-mentioned longer life, by improving the efficiency of the transfer process, it is required to suppress the scattering of toner during transfer to improve the image quality and reduce the waste toner.

[0004] Conventionally, polycarbonate resin has been often used as the binder resin of the surface layer of the electrophotographic photoreceptor. Further, strontium titanate has been used as an external additive of the toner for electrostatic latent image development for the purpose of controlling the charging property of the toner. In Patent Document 1, an electrophotographic apparatus has been proposed in which polycarbonate resin is used as the binder resin of the charge transport layer serving as the surface layer of the photoreceptor, and strontium titanate is used as an external additive of the toner.

[0005] In addition, a proposal has been made to improve the durability of the electrophotographic photoreceptor by using a polyarylate resin having higher mechanical strength than polycarbonate resin as the binder resin of the surface layer. Polyarylate resin is a kind of aromatic dicarboxylic acid polyester resin. In Patent Document 2, a photoreceptor has been proposed in which polyarylate resin is contained in the photosensitive layer serving as the surface layer, thereby improving the durability and electrical characteristics.

Prior Art Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-131520 [Patent Document 2] Japanese Patent Publication No. 2011-227486 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In the electrophotographic photoreceptor described in Patent Document 1, it is conceivable to replace the polycarbonate resin used as a binder with the polyarylate resin described in Patent Document 2 in order to improve the durability of the photoreceptor. However, according to the inventors' studies, there was room for improvement in the transferability of electrophotographic devices using such electrophotographic photoreceptors when repeatedly used in low-temperature, low-humidity environments.

[0008] Therefore, the object of the present invention is to provide an electrophotographic apparatus that has excellent transfer properties even in low-temperature, low-humidity environments, comprising a toner having strontium titanate as an external additive and an electrophotographic photoreceptor with excellent durability. [Means for solving the problem]

[0009] The above objective is achieved by the present invention as follows: That is, the electrophotographic apparatus according to the present invention is An electrophotographic photoreceptor having a surface layer containing resin X as a binder resin, A charging means for charging the surface of the electrophotographic photoreceptor, An exposure means for irradiating light onto the surface of the charged electrophotographic photoreceptor to form an electrostatic latent image, A developing means that supplies toner to the electrostatic latent image to form a toner image, A transfer means for transferring the toner image onto a transfer medium, It has, The toner contains strontium titanate as an external additive, The resin X is a polyarylate resin having structural units represented by formula (1), formula (2), formula (3), and formula (4). It is characterized by the following: [ka] [ka] [ka] [ka] (The asterisk (*) in equations (1) to (4) represents the bonding site with an adjacent structural unit.) [Effects of the Invention]

[0010] According to the present invention, an electrophotographic apparatus can be provided that includes a toner containing strontium titanate as an external additive and an electrophotographic photoreceptor with excellent durability, and exhibits excellent transfer performance even in low-temperature, low-humidity environments. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example of a schematic configuration of an electrophotographic apparatus according to the present invention, which includes a process cartridge. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below with reference to preferred embodiments. In the electrophotographic apparatus described in Patent Document 1, which uses an electrophotographic photoreceptor with a surface layer containing polycarbonate resin and a toner with strontium titanate added externally, no deterioration in transfer performance occurs. However, in an electrophotographic apparatus using an electrophotographic photoreceptor in which the polycarbonate resin has been changed to polyarylate resin for the purpose of improving durability, and a toner with strontium titanate added externally, deterioration in transfer performance occurred in a low-temperature, low-humidity environment. The inventors speculate as follows on why transfer performance deteriorates when an electrophotographic photoreceptor with a surface layer containing polyarylate resin is used.

[0013] When the surface of a photoreceptor is charged, a discharge occurs from the charging component to the photoreceptor. This discharge energy causes discharge degradation of the substances contained on the surface of the photoreceptor. Specifically, the bonds of the binder resin on the surface of the photoreceptor may be broken by the discharge energy.

[0014] Polyarylate resins are prone to COOH groups being formed when ester bonds are broken by electrical discharge. Especially in low-temperature, low-humidity environments, the discharge is unstable, which can lead to strong discharges and significant discharge degradation. Therefore, it is likely that a large number of COOH groups are formed on the surface of the photoreceptor during prolonged repeated use.

[0015] Furthermore, strontium titanate has a perovskite crystal structure, which allows for easy interaction between the metallic titanium and its functional groups. In particular, the COOH group exhibits a strong interaction through coordinate bonding between its lone pair of electrons and the orbitals of the metallic titanium.

[0016] Therefore, it is thought that during repeated use, the adhesion between the toner with strontium titanate added and the surface layer of the photoreceptor containing polyarylate resin becomes stronger, resulting in a deterioration of transferability.

[0017] On the other hand, polycarbonate resin is less prone to generating COOH groups even when subjected to discharge energy, and also has lower mechanical strength compared to polyarylate resin, making it easier for COOH groups to be removed by friction on the photoreceptor surface. Therefore, it is presumed that when a toner containing strontium titanate was combined with a conventional photoreceptor whose surface layer contains polycarbonate resin, no deterioration in transferability occurred.

[0018] Based on the above speculation, the inventors of the present invention investigated various methods for using strontium titanate as an external additive for toner to improve the durability of the electrophotographic photoreceptor without deteriorating its transferability, and as a result arrived at the configuration of the present invention.

[0019] In other words, the electrophotographic apparatus according to the present invention comprises a developing means for supplying a toner containing strontium titanate as an external additive to an electrostatic latent image to form a toner image, and an electrophotographic photoreceptor having a surface layer containing resin X as a binder resin. Here, resin X is a polyarylate resin having structural units represented by formula (1), formula (2), formula (3), and formula (4).

[0020] [ka] [ka] [ka] [ka] (The asterisk (*) in equations (1) to (4) represents the bonding site with an adjacent structural unit.)

[0021] Polyarylate resins have a structure in which a structure derived from a dicarboxylic acid having an aromatic ring and a structure derived from a diol (bisphenol) having an aromatic ring are bonded to each other. The inventors have found that when polyarylate resins have an ether structure in the bond between the aromatic rings, they are resistant to discharge degradation. Furthermore, we found that when polyarylate resins were used in which both the dicarboxylic acid-derived structure and the bisphenol-derived structure simultaneously possessed ether structures between their aromatic rings, the structure became particularly resistant to discharge degradation and less prone to the formation of COOH groups. The resin X contained in the surface layer of the photoreceptor according to the present invention has a structural unit represented by formula (1) derived from dicarboxylic acid and a structural unit represented by formula (2) derived from bisphenol, both of which have an ether structure between aromatic rings. Therefore, the photoreceptor according to the present invention is considered to have high resistance to discharge degradation. In addition, since resin X simultaneously possesses both a small, flexible structure of structural units represented by formula (3) and a bulky, skeletal structure of structural units represented by formula (4), the surface layer can be made homogeneous. This allows the discharge degradation suppression effect of the structural units represented by formulas (1) and (2) to be fully realized, improving both wear resistance and discharge degradation suppression. In this way, it is presumed that the adhesion force with the toner to which strontium titanate is added is prevented from becoming too strong, and the transferability is improved even in low-temperature, low-humidity environments. The components of the present invention will be described in more detail below.

[0022] [Electrophotographic photoconductor] The electrophotographic photoreceptor according to the present invention comprises at least a support and a photosensitive layer formed on the support. Furthermore, the electrophotographic photoreceptor according to the present invention comprises a surface layer containing resin X as a binder resin. A method for manufacturing an electrophotographic photoreceptor according to the present invention involves preparing coating solutions for each layer, as described later, applying them in the desired layer order, and drying them. Methods for applying the coating solutions include immersion coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, immersion coating is preferred from the viewpoint of efficiency and productivity. The support structure and each layer will be described below.

[0023] <Support> In the present invention, the electrophotographic photoreceptor has a support. In the present invention, the support is preferably a conductive support. The shape of the support can be cylindrical, belt-shaped, or sheet-shaped. Among these, a cylindrical support is preferred. Furthermore, the surface of the support may be subjected to electrochemical treatments such as anodizing, blasting, or cutting.

[0024] Suitable materials for the support include metal, resin, and glass. Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among these, an aluminum support made of aluminum is preferred. Furthermore, conductivity may be imparted to resins and glass by processing such as mixing or coating them with conductive materials.

[0025] <Conductive layer> In the present invention, a conductive layer may be provided on the support. Providing a conductive layer makes it possible to cover unevenness and defects in the support and prevent interference fringes. The average thickness of the conductive layer is preferably 5 μm or more and 40 μm or less.

[0026] The conductive layer preferably contains conductive particles and a binder resin. Examples of conductive particles include carbon black, metal particles, and metal oxide particles. Examples of metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of metals include aluminum, nickel, iron, nichrome, copper, zinc, and silver. Among these, it is preferable to use metal oxides as conductive particles, and it is more preferable to use titanium oxide, tin oxide, or zinc oxide.

[0027] When using metal oxides as conductive particles, the surface of the metal oxide may be treated with a silane coupling agent or doped with elements such as phosphorus or aluminum, or their oxides. Examples of elements and oxides that can be doped include phosphorus, aluminum, niobium, and tantalum.

[0028] Furthermore, the conductive particles may have a laminated structure comprising core material particles and a coating layer covering those particles. Examples of core material particles include titanium oxide, barium sulfate, and zinc oxide. Examples of coating layers include metal oxides such as tin oxide and titanium oxide. Furthermore, when using metal oxides as conductive particles, it is preferable that their volume-average particle diameter be between 1 nm and 500 nm.

[0029] Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, and alkyd resin. Furthermore, the conductive layer may further contain silicone oil, resin particles, a concealing agent such as titanium dioxide, etc.

[0030] The average thickness of the conductive layer is preferably 1 μm or more and 50 μm or less. A conductive layer can be formed by preparing a coating solution for a conductive layer containing the above-mentioned materials and solvents, forming a coating film, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Methods for dispersing conductive particles in the coating solution for a conductive layer include using a paint shaker, sand mill, ball mill, or liquid impaction type high-speed disperser.

[0031] <Underlayer> In the present invention, an undercoat layer may be provided on the support or conductive layer. By providing an undercoat layer, the interlayer adhesion function is enhanced and a charge injection prevention function can be provided. The undercoat layer preferably contains a resin. Alternatively, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having polymerizable functional groups.

[0032] Examples of resins include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenolic resin, polyvinylphenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin, polyimide resin, polyamide-imide resin, and cellulose resin.

[0033] Polymerizable functional groups found in monomers possessing polymerizable functional groups include isocyanate groups, blocked isocyanate groups, methylol groups, alkylated methylol groups, epoxy groups, metal alkoxide groups, hydroxyl groups, amino groups, carboxyl groups, thiol groups, carboxylic acid anhydride groups, and carbon-carbon double bond groups.

[0034] Furthermore, the undercoat layer may further contain electron transport materials, metal oxides, metals, conductive polymers, etc., for the purpose of improving electrical properties. Among these, electron transport materials and metal oxides are preferred.

[0035] Examples of electron transport materials include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienylidene compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, aryl halides, silole compounds, and boron-containing compounds. An electron transport material having polymerizable functional groups may be used as the electron transport material, and a base layer may be formed as a cured film by copolymerizing it with the above-mentioned monomers having polymerizable functional groups.

[0036] Examples of metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide. Examples of metals include gold, silver, and aluminum. Furthermore, the underlayer may contain additional additives.

[0037] The average thickness of the undercoat layer is preferably 0.1 μm or more and 50 μm or less, more preferably 0.2 μm or more and 40 μm or less, and particularly preferably 0.3 μm or more and 30 μm or less.

[0038] The undercoat can be formed by preparing an undercoat coating solution containing the above-mentioned materials and solvents, forming a coating film, and then drying and / or curing it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0039] <Photosensitive layer> The photosensitive layer of an electrophotographic photoreceptor is mainly classified into (1) a multilayer photosensitive layer and (2) a single-layer photosensitive layer. (1) A multilayer photosensitive layer has a charge generating layer containing a charge generating material and a charge transport layer containing a charge transport material. (2) A single-layer photosensitive layer has a photosensitive layer containing both a charge generating material and a charge transport material. The electrophotographic photoreceptor according to the present invention preferably has a multilayer photosensitive layer.

[0040] (1) Stacked photosensitive layer The stacked photosensitive layer comprises a charge generation layer and a charge transport layer.

[0041] (1-1) Charge generation layer The charge generation layer preferably contains a charge generation material and a binder resin. As the charge-generating material used in the charge-generating layer, phthalocyanine pigments are preferred. Examples of phthalocyanines include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine, with titanyl phthalocyanine being more preferred.

[0042] Examples of binder resins used in the charge generation layer include polyvinyl butyral resin, polyvinyl acetal resin, polyarylate resin, polycarbonate resin, polyester resin, polyvinyl acetate resin, polysulfone resin, polystyrene resin, phenoxy resin, acrylic resin, phenoxy resin, polyacrylamide resin, polyvinylpyridine resin, urethane resin, agarose resin, cellulose resin, casein resin, polyvinyl alcohol resin, polyvinylpyrrolidone resin, vinylidene chloride resin, acrylonitrile copolymer, and polyvinylbenzal resin (insulating resins). Organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene can also be used. Furthermore, only one type of binder resin may be used, or two or more types may be used in combination as a mixture or copolymer.

[0043] Examples of solvents used in the coating solution for the charge generation layer include toluene, xylene, tetralin, chlorobenzene, dichloromethane, chloroform, trichloroethylene, tetrachloroethylene, carbon tetrachloride, methyl acetate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, acetone, methyl ethyl ketone, cyclohexanone, diethyl ether, dipropyl ether, propylene glycol monomethyl ether, dioxane, methylal, tetrahydrofuran, water, methanol, ethanol, n-propanol, isopropanol, butanol, methyl cellosolve, methoxypropanol, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. Furthermore, the solvents can be used individually or in combination of one or more types.

[0044] The charge generation layer is obtained by dispersing a phthalocyanine pigment as a charge generation material and, if necessary, a binder resin in a solvent to prepare a coating solution for the charge generation layer, forming a coating film of the charge generation layer coating solution, and then drying it.

[0045] The coating solution for the charge generation layer may be prepared by adding only the charge generation substance to a solvent and dispersing it, followed by the addition of a binder resin, or by adding the charge generation substance and the binder resin together to a solvent and dispersing them.

[0046] For the above dispersion, media-type dispersers such as sand mills and ball mills, or dispersers such as liquid impact type dispersers and ultrasonic dispersers can be used.

[0047] (1-2) Charge transport layer The charge transport layer preferably contains a charge transport material and a binder resin. In one embodiment of the present invention, the charge transport layer may be a surface layer. When the charge transport layer is a surface layer, the charge transport layer contains a charge transport material and resin X as a binder resin. In this case, the flexibility of the structural unit represented by formula (3) and the bulkiness due to the structural unit represented by formula (4) can suppress the uneven distribution of the binder resin and the charge transport material. This makes it possible to obtain a high level of discharge degradation suppression effect due to the structural unit represented by formula (1) and the structural unit represented by formula (2) that resin X possesses. The following provides further details about the binder resin and charge transport material contained in the charge transport layer, assuming that the charge transport layer is the surface layer.

[0048] [Binding resin] When the charge transport layer is a surface layer, the charge transport layer contains a resin X as a binder resin having structural units represented by formula (1), formula (2), formula (3), and formula (4).

[0049] [ka] [ka] [ka] [ka] (The asterisk (*) in equations (1) to (4) represents the bonding site with an adjacent structural unit.)

[0050] The ratio n2 / n1 of the number of structural units represented by formula (4) in resin X to the number of structural units represented by formula (2) in resin X to the number of structural units represented by formula (4) in resin X is preferably 1.0 or greater. If n2 / n1 is 10.0 or greater, it is difficult to obtain the effects of wear resistance and suppression of discharge degradation. More preferably, n2 / n1 is between 1.0 and 4.0.

[0051] The viscosity-average molecular weight of resin X is preferably 10,000 or more, and more preferably 40,000 or more. When the viscosity-average molecular weight of resin X is 10,000 or more, the abrasion resistance of the photoreceptor is improved. On the other hand, the viscosity-average molecular weight of resin X is preferably 80,000 or less, and more preferably 70,000 or less. When the viscosity-average molecular weight of resin X is 80,000 or less, resin X dissolves easily in the solvent for forming the photosensitive layer.

[0052] Examples of bisphenols used to construct the structural units represented by formula (2) and formula (4), which are repeating units derived from bisphenols, include the compound represented by formula (BP-2) and the compound represented by formula (BP-5), respectively. Hereinafter, the compound represented by formula (BP-2) will also be referred to as compound (BP-2), and the compound represented by formula (BP-5) will also be referred to as compound (BP-5).

[0053] Furthermore, examples of dicarboxylic acids used to constitute the structural units represented by formula (1) and formula (3), which are repeating units derived from dicarboxylic acids, include the compound represented by formula (DC-1) and the compound represented by formula (DC-4), respectively. Hereinafter, the compound represented by formula (DC-1) will also be referred to as compound (DC-1), and the compound represented by formula (DC-4) will also be referred to as compound (DC-4).

[0054] The bisphenol ratio in polyarylate resin can be adjusted by changing the amounts of compound (BP-2) and compound (BP-5) added during the manufacturing process. Similarly, the dicarboxylic acid ratio in polyarylate resin can be adjusted by changing the amounts of compound (DC-1) and compound (DC-4) added during the manufacturing process.

[0055] [ka] [ka] [ka] [ka]

[0056] Bisphenols (e.g., compounds (BP-2) and (BP-5)) may be used after derivatization to aromatic diacetates. Dicarboxylic acids (e.g., compounds (DC-1) and (DC-4)) may be used after derivatization. Examples of dicarboxylic acid derivatives include dicarboxylic acid dichlorides, dicarboxylic acid dimethyl esters, dicarboxylic acid diethyl esters, and dicarboxylic acid anhydrides. Dicarboxylic acid dichlorides are compounds having a structure in which the two "-C(=O)-OH" groups of the dicarboxylic acid are each replaced by "-C(=O)-Cl" groups.

[0057] In the condensation polymerization of bisphenol and dicarboxylic acid, one or both of a base and / or a catalyst may be added. Examples of bases include sodium hydroxide. Examples of catalysts include benzyltributylammonium chloride, ammonium chloride, ammonium bromide, quaternary ammonium salts, triethylamine, and trimethylamine.

[0058] The charge transport layer may further contain other resins besides resin X, which is a polyarylate resin having structural units represented by formula (1), formula (2), formula (3), and formula (4) as a binder resin. Examples of other resins include other polyarylate resins, polyester resins, polycarbonate resins, styrene resins, acrylic resins, etc. The polyarylate resin may be, for example, a random copolymer, an alternating copolymer, a periodic copolymer, or a block copolymer. Other structural units of polyarylate resins include the following examples.

[0059] [ka] [ka] [ka] [ka]

[0060] Furthermore, resin X may have other structural units. For example, resin X may be a copolymer containing structural units consisting of groups derived from other divalent carboxylic acids and divalent organic residues, different from the structural units represented by formula (1), formula (2), formula (3), and formula (4). In the binder resin in the surface layer, the total content of structural units represented by formula (1), formula (2), formula (3), and formula (4) of resin X is preferably 50% by mass or more and 100% by mass or less.

[0061] The method for producing resin X is not particularly limited. For example, one method involves polycondensation of bisphenol to constitute a bisphenol-derived structure and a dicarboxylic acid to constitute a dicarboxylic acid-derived structure. Known methods can be used for synthesis by polycondensation. Derivatives of bisphenol and dicarboxylic acid may be used. Aromatic diacetates may be used as derivatives of bisphenol. Examples of dicarboxylic acid derivatives include dicarboxylic acid dichlorides, dicarboxylic acid dimethyl esters, dicarboxylic acid diethyl esters, and dicarboxylic acid anhydrides.

[0062] The ratio n2 / n1 can be adjusted by changing the type and amount of bisphenol and dicarboxylic acid when manufacturing resin X. The ratio n² / n¹ can be analyzed and calculated using nuclear magnetic resonance analysis or pyrolysis GC-MS analysis.

[0063] Component analysis of polymer components recovered from the photosensitive layer in deuterated chloroform 1 This can be obtained by subjecting the analysis to 1H nuclear magnetic resonance (NMR) analysis. 1 The structure of resin X can be determined by 1H nuclear magnetic resonance spectroscopy. The specific methods are explained below.

[0064] ■Reprecipitation of the binder resin in the surface layer of the photoreceptor • Cut the photoreceptor (hereinafter also simply referred to as the "drum"). Cut the drum using a coping saw 10 cm from the end of the drum in the direction of the generatrix. • Wash the 10cm section of the drum's interior. Wipe the inside of the cylinder with lens tissue soaked in chloroform. • It elutes the surface layer. Immerse the 3 cm end of the drum on the cut side in chloroform. (Pour approximately 60 mL of chloroform into a 100 mL beaker and immerse it at room temperature for 5 minutes.) • To concentrate (to make into a thick liquefying solution). The solution is concentrated using a rotary evaporator until it reaches 2 mL, then the evaporator is stopped. • To sink again. Prepare 50 mL of methanol / acetone mixture (volume ratio 1:1) and add the entire concentrated solution dropwise while stirring. Filter. Perform suction filtration using a Kiriyama funnel. (Funnel: SU-40, Filter paper: No. 5C-40, both manufactured by Kiriyama Seisakusho Co., Ltd.) • To dry out The residue on the filter paper is collected with a spatula and vacuum-dried (70°C for 1 hour).

[0065] ■ NMR measurement • Sample preparation Dissolve 20 mg of the sample in 1 g of deuterated chloroform containing the reference substance tetramethylsilane, and transfer the entire volume to an NMR tube. (Deuterated chloroform: Manufactured by Sigma-Aldrich Japan Co., Ltd., Chloroform-d, Model No. 612200) (NMR tube: Norell, ST500-7, model number S3010) ·NMR measurement Equipment: Bruker AVANCE500 Conditions: Automated measurement using proton NMR and ICON-NMR. Total number of times: 32 Reference peak: The methyl group peak of tetramethylsilane is set to 0 ppm.

[0066] [Charge transport material] The charge transport material preferably contains at least one selected from the group consisting of the compound represented by formula (20), the compound represented by formula (21), the compound represented by formula (22), the compound represented by formula (23), the compound represented by formula (24), and the compound represented by formula (25).

[0067] [ka] [ka] [Chemical] [Chemical] [Chemical] [Chemical]

[0068] In formula (20), R 11 , R 12 , R 13 , and R 14 each independently represent an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms. a1, a2, a3, and a4 each independently represent an integer of 0 to 5. In formula (20), when a1 represents an integer of 2 to 5, the plurality of R 11 may represent the same group as each other or different groups. When a2 represents an integer of 2 to 5, the plurality of R 12 may represent the same group as each other or different groups. When a3 represents an integer of 2 to 5, the plurality of R 13 may represent the same group as each other or different groups. When a4 represents an integer of 2 to 5, the plurality of R 14 may represent the same group as each other or different groups. In formula (20), R 11 , R 12 , R 13 , and R 14 each independently preferably represent an alkyl group having 1 to 3 carbon atoms, more preferably represent a methyl group or an ethyl group. a1, a2, a3, and a4 each independently preferably represent an integer of 1 to 3, more preferably represent 1.

[0069] In formula (21), R 21 , R 22 , and R 23 each independently represent an alkyl group having 1 to 6 carbon atoms. R 24 , R25 , and R 26 Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Each independently represents 0 or 1. In formula (21), R 21 , R 22 , and R 23 Each of these preferably independently represents an alkyl group having 1 to 3 carbon atoms, and more preferably represents a methyl group. 21 , R 22 , and R 23 It is preferable that the phenyl group is bonded to the meta position of the ethenyl group or the butadienyl group. 24 , R 25 , and 26 Each of these preferably represents a hydrogen atom. It is preferable that b1, b2, and b3 all represent 0 or all represent 1.

[0070] In formula (22), R 31 , R 32 , and R 33 Each of these independently represents an alkyl group having 1 to 6 carbon atoms. 34 represents an alkyl group or hydrogen atom having 1 to 6 carbon atoms. d1, d2, and d3 each independently represent an integer between 0 and 5. In formula (22), when d1 represents an integer between 2 and 5, multiple R 31 These may represent the same base or different bases. When d2 represents an integer between 2 and 5, multiple R 32 These may represent the same base or different bases. When d3 represents an integer between 2 and 5, multiple R 33 These may represent the same group or different groups. In equation (22), R 34 It is preferable that represents a hydrogen atom. It is preferable that d1, d2, and d3 each represent 0.

[0071] In formula (23), R 41 , R 42 , R 43 , R 44 , R 45 , and R 46Each of these independently represents an alkyl group having 1 to 6 carbon atoms, or a phenyl group. 47 and R 48 Each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group. Each independently represents an integer between 0 and 5. Each independently represents an integer between 0 and 4. Each independently represents an integer between 0 and 4. Each independently represents 0 or 1. In formula (23), when e1 represents an integer between 2 and 5, multiple R 41 These may represent the same base or different bases. When e2 represents an integer between 2 and 5, multiple R 42 These may represent the same base or different bases. When e3 represents an integer between 2 and 5, multiple R 43 These may represent the same base or different bases. When e4 represents an integer between 2 and 5, multiple R 44 These may represent the same base or different bases. When e5 represents an integer between 2 and 4, multiple R 45 These may represent the same base or different bases. When e6 represents an integer between 2 and 4, multiple R 46 These may represent the same group or different groups. In equation (23), R 41 ~R 46 Each of these groups preferably independently represents an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group or an ethyl group. 47 and R 48 e1 preferably represents a hydrogen atom. Each of e1, e2, e3, and e4 preferably independently represents an integer between 0 and 2, with e1 and e2 representing 0 and e3 and e4 representing 2. e5 and e6 preferably represent 0. e7 and e8 preferably both represent 0 or both represent 1.

[0072] In formula (24), R 50 and R 51Each of these independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group. 52 , R 53 , R 54 , R 55 , R 56 , R 57 , and R 58 Each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group which may be substituted with an alkyl group having 1 to 6 carbon atoms. Each independently represents an integer between 0 and 2. Each independently represents an integer between 0 and 5. In formula (24), when f3 represents an integer between 2 and 5, multiple R 50 These may represent the same base or different bases. When f4 represents an integer between 2 and 5, multiple R 51 These may represent the same group or different groups. In equation (24), R 50 and R 51 Preferably, each of these independently represents an alkyl group having 1 to 6 carbon atoms. 52 and R 53 Each of these preferably represents a phenyl group which may be substituted with a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. 54 ~R 58 Each of these preferably independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. It is preferable that both f1 and f2 represent 0, both represent 1, or both represent 2. It is preferable that each of f3 and f4 independently represents 0 or 1. 50 and R 51 The alkyl group represented by has 1 to 6 carbon atoms is preferably an alkyl group with 1 to 3 carbon atoms, and a methyl group is more preferably preferred. 52 and R 53The phenyl group that may be substituted with an alkyl group having 1 to 6 carbon atoms is preferably a phenyl group, or a phenyl group in which 1 to 5 positions are substituted with an alkyl group having 1 to 3 carbon atoms. The phenyl group substituted with an alkyl group having 1 to 3 carbon atoms is preferably a methylphenyl group, and more preferably a 4-methylphenyl group. 54 ~R 58 The alkyl group having 1 to 6 carbon atoms represented by is preferably an alkyl group having 1 to 4 carbon atoms, and preferably represents a methyl group, an ethyl group, or an n-butyl group. 54 ~R 58 The alkoxy group represented by has 1 to 6 carbon atoms is preferably an alkoxy group with 1 to 3 carbon atoms, and more preferably an ethoxy group.

[0073] In formula (25), R 61 , R 62 , R 63 , R 64 , R 65 , and R 66 Each of the following independently represents an alkyl group, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms; each of the following independently represents an integer between 0 and 5; and each of the following independently represents an integer between 0 and 4.

[0074] A preferred example of the compound represented by formula (20) is the compound represented by formula (H-11). Preferred examples of the compound represented by formula (21) are the compounds represented by formula (H-7) and (H-8). A preferred example of the compound represented by formula (22) is the compound represented by formula (H-6). Preferred examples of the compound represented by formula (23) are the compounds represented by formula (H-9) and (H-10). Preferred examples of the compound represented by formula (24) are the compounds represented by formula (H-1), formula (H-2), formula (H-3), and formula (H-5). A preferred example of the compound represented by formula (25) is the compound represented by formula (H-4). Hereinafter, the compounds represented by formulas (H-1) to (H-11) may be referred to as charge transporter (H-1) to charge transporter (H-11), respectively.

[0075] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0076] The charge transport material content in the charge transport layer is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 30 parts by mass or more and 120 parts by mass or less, and even more preferably 50 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the binder resin.

[0077] The photosensitive layer may contain only one type of charge transporting material, or it may contain two or more types of charge transporting materials. Furthermore, the photosensitive layer may further contain charge transporting materials other than the compounds represented by formulas (20), (21), (22), (23), (24), or (25) (hereinafter sometimes referred to as other charge transporting materials).

[0078] Other charge transport materials include, for example, triphenylamine derivatives, diamine derivatives (e.g., N,N,N',N'-tetraphenylbenzidine derivatives, N,N,N',N'-tetraphenylphenylenediamine derivatives, N,N,N',N'-tetraphenylnaphthylenediamine derivatives, N,N,N',N'-tetraphenylphenantolylenediamine derivatives, and di(aminophenylethenyl)benzene derivatives), oxadiazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazoles), and oxadiazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazoles). Examples include diazoles, styryl compounds (e.g., 9-(4-diethylaminostyryl)anthracene), carbazole compounds (e.g., polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (e.g., 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

[0079] The charge transport layer may contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, lubrication agents, and wear resistance enhancers. Specifically, examples include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

[0080] The average thickness of the charge transport layer is preferably 5 μm to 50 μm, and more preferably 8 μm to 40 μm.

[0081] The charge transport layer can be formed by preparing a coating solution for the charge transport layer containing the above-mentioned materials and solvents, forming a coating film, and drying it. Examples of solvents used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents or aromatic hydrocarbon-based solvents are preferred.

[0082] (2) Single-layer photosensitive layer A single-layer photosensitive layer can be formed by preparing a coating solution for a photosensitive layer containing a charge generating substance, a charge transporting substance, a binder resin, and a solvent, forming this coating film, and drying it. In one embodiment of the present invention, the single-layer photosensitive layer may be a surface layer. The charge generating material, charge transport material, and binder resin contained in the single-layer photosensitive layer can be the same as those exemplified in "(1) Multilayer photosensitive layer" above.

[0083] [toner] The toner according to the present invention comprises toner particles containing a binder resin and an external additive, the external additive being strontium titanate. Strontium titanate can adjust the chargeability and fluidity of the toner. The ratio of the mass of strontium titanate to the mass of toner particles in the toner is preferably 0.05% by mass or more and 5.0 parts by mass or less, and more preferably 0.1% by mass or more and 1.0% by mass or less.

[0084] <Binding resin> The binder resin contained in the toner particles according to the present invention is not particularly limited, and known resins can be used, but vinyl resins, polyester resins, etc. are preferred. Examples of vinyl resins, polyester resins, and other binder resins include the following resins or polymers.

[0085] Monopolymers of styrene and its substituted products such as polystyrene and polyvinyltoluene; styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers, styrene-methyl acrylate copolymers, styrene-ethyl acrylate copolymers, styrene-butyl acrylate copolymers, styrene-octyl acrylate copolymers, styrene-dimethylaminoethyl acrylate copolymers, styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-butyl methacrylate copolymers, styrene-dimethylaminoethyl methacrylate copolymers, styrene-vinyl methyl ether copolymers, styrene-vinyl ethyl ether copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-maleic acid copolymers, styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resins, polyamide resins, epoxy resins, polyacrylic resins, rosin, modified rosin, terpene resins, phenolic resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins. These binder resins can be used individually or in combination. Preferably, the binder resin is a styrene copolymer.

[0086] The binder resin preferably has carboxyl groups, and is preferably a resin manufactured using a polymerizable monomer having carboxyl groups. Examples of polymerizable monomers having a carboxyl group include acrylic acid, methacrylic acid; α-alkyl 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 monoacryloyloxyethyl succinate, monoacryloyloxyethylene succinate, monoacryloyloxyethyl phthalate, and monomethacryloyloxyethyl phthalate.

[0087] As the polyester resin, a material obtained by condensation polymerization of the carboxylic acid component and alcohol component listed below can be used.

[0088] Examples of carboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, fumaric acid, maleic acid, cyclohexanedicarboxylic acid, and trimellitic acid. Examples of alcohol components include bisphenol A, hydrogenated bisphenol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, glycerin, trimethylolpropane, and pentaerythritol. Furthermore, the polyester resin may be a polyester resin containing urea groups. It is preferable that the carboxyl groups at the ends of the polyester resin are not capped.

[0089] <wax> The toner according to the present invention may contain wax. The wax is not particularly limited and known waxes can be used. Preferably, the wax content is 5.0 parts by mass or more and 20.0 parts by mass or less per 100.0 parts by mass of the binder resin or polymerizable monomer that produces the binder resin.

[0090] <Coloring agent> The coloring agent is not particularly limited, and any known coloring agent can be used.

[0091] Yellow pigments 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, as well as isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and allylamide compounds. Specifically, the following can be mentioned: CI Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 155, 168, 180, 185, and 193.

[0092] Examples of red pigments include condensed azo compounds such as red iron oxide, permanent red 4R, lysol 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, as well as diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Specifically, the following are examples: CI 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, and 254.

[0093] Examples of blue pigments include alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chloride, first sky blue, copper phthalocyanine compounds and their derivatives such as induthlene blue BG, anthraquinone compounds, and basic dye lake compounds. Specifically, the following can be mentioned: CI Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, 66.

[0094] Examples of black pigments include carbon black, aniline black, non-magnetic ferrite, magnetite, and pigments colored black using the aforementioned yellow, red, and blue colorants. These colorants can be used individually, in combination, or even in solid solution form.

[0095] If necessary, the colorant may be surface-treated with a substance that does not inhibit polymerization. Preferably, the colorant content is 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 polymerizable monomer that produces the binder resin.

[0096] <Charge control agent> The toner according to the present invention may contain a charge control agent. Known charge control agents can be used. In particular, charge control agents that have a fast charging speed and can stably maintain a constant amount of charge are preferred. Furthermore, when toner particles are manufactured by a direct polymerization method, charge control agents that have low polymerization inhibitory properties and substantially no solubilizes in aqueous media are preferred.

[0097] Examples of charge control agents that control the charge properties of toner particles according to the load include the following: Examples of organometallic compounds and chelates include monoazo metal compounds, acetylacetone metal compounds, aromatic oxycarboxylic acids, aromatic dicarboxylic acids, and metal compounds of oxycarboxylic and dicarboxylic acid systems. Other examples include aromatic oxycarboxylic acids, aromatic mono and polycarboxylic acids and their metal salts, anhydrides or esters, and phenol derivatives such as bisphenol. Furthermore, examples include urea derivatives, metal-containing salicylic acid compounds, metal-containing naphthoic acid compounds, boron compounds, quaternary ammonium salts, and calixarenes.

[0098] These charge control agents can be included individually or in combination of two or more types. Preferably, the content of the charge control agent is 0.01 parts by mass or more and 10.0 parts by mass or less per 100.0 parts by mass of the binder resin.

[0099] <Toner additive> The toner used in the present invention may contain, in addition to strontium titanate, other external additives for the purpose of improving fluidity, chargeability, blocking properties, etc.

[0100] Examples of external additives that may be included in the toner include inorganic fine particles such as silica fine particles, alumina fine particles, and titanium oxide fine particles. These can be used individually or in combination of two or more. It is preferable that these inorganic fine particles are surface-treated with silane coupling agents, titanium coupling agents, higher fatty acids, silicone oils, etc., to improve heat resistance and environmental stability.

[0101] 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 toner particles. The content of strontium titanate is preferably 0.1 parts by mass or more and 1.0 part by mass or less per 100.0 parts by mass of toner particles. The presence of strontium titanate in toner additives can be confirmed by X-ray diffraction or by energy-dispersive X-ray spectroscopy (EDS) using the electron gun of a scanning electron microscope (SEM) or transmission electron microscope (TEM). When using strontium titanate particles separated from the surface of the toner as the measurement sample, the separation of strontium titanate particles from the toner is performed using the following procedure.

[0102] Add 160g of sucrose (manufactured by Kishida Chemical Co., Ltd.) to 100mL of deionized water and dissolve it in a water bath to prepare a concentrated sucrose solution. Place 31g of this concentrated sucrose solution and 6mL of Contaminon N (a 10% by mass aqueous solution of a pH 7.0 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) into a centrifuge tube to prepare a dispersion. Add 1g of toner to this dispersion and break up any clumps of toner with a spatula or similar tool.

[0103] Set the centrifuge tube on the "KM Shaker" (model: V.SX) manufactured by Iwaki Sangyo Co., Ltd. and shake it for 20 minutes under the condition of 350 reciprocations per minute. After shaking, replace the solution with a glass tube (50 mL) for a swinging rotor and centrifuge it at 3500 rpm for 30 minutes using a centrifuge. In the glass tube after centrifugation, toner exists in the uppermost layer, and particles separated from the toner surface exist on the aqueous solution side of the lower layer. Collect the aqueous solution in the lower layer, and if necessary, repeat centrifugation. After sufficient separation, separate the strontium titanate particles, dry them, and collect the strontium titanate particles. Repeat until the required amount of strontium titanate particles can be collected.

[0104] The specific conditions of X-ray diffraction method and EDS for confirming that the external additive of the toner contains strontium titanate are as follows.

[0105] <X-ray diffraction method> As measurement samples, use those obtained by isolating strontium titanate particles from the toner and a standard sample of strontium titanate particles, and measure them according to the following procedure. Thus, it can be confirmed by analysis that the external additive of the toner contains strontium titanate.

[0106] The diffraction peak of strontium titanate particles is specified using a powder X-ray diffractometer "SmartLab" (manufactured by Rigaku Corporation, a sample horizontal type high-power X-ray diffractometer). When specifying the diffraction peak, use "PDXL2 (version 2.2.2.0)" of the analysis software attached to the above device.

[0107] (Sample preparation) The measurement sample is measured after being uniformly placed in a Boro-Silicate capillary with a diameter of 0.5 mm (manufactured by W. Muller).

[0108] (Measurement conditions) · Tube ball: Cu · Optical system: CBO-E ·Sample stage: Capillary sample stage ·Detector: D / tex Ultra250 detector ·Voltage: 45 kV ·Current: 200 mA ·Start angle: 10° ·End angle: 90° ·Sampling width: 0.02° ·Speed measurement time setting value: 10 ·IS: 1 mm ·RS1: 20 mm ·RS2: 20 mm ·Attenuator: Open ·Capillary rotation number setting value: 100 For other conditions, use the initial setting values of the device.

[0109] (Analysis) First, perform peak separation processing on the obtained peaks using the software "PDXL2" attached to the device. Peak separation is obtained by performing optimization using the "split-type Voigt function" that can be selected in PDXL, and the value of the obtained integrated intensity is used.

[0110] <STEM-EDS method> Confirmation that the external additive is strontium titanate is also possible by STEM-EDS measurement. The measurement conditions are as follows. JEM2800 type transmission electron microscope: Acceleration voltage 200 kV EDS detector: JED-2300T (JEOL, element area 100 mm 2 ) EDS analyzer: Noran System7 (Thermo Fisher Scientific) X-ray storage rate: 10000 - 15000 cps Adjust the electron dose so that the dead time is 20 - 30%, and perform EDS analysis (integration count 100 times or measurement time 5 min).

[0111] As a method for calculating the mass of the strontium titanate with respect to the toner particles, fluorescence X-ray analysis can be used. <X-ray fluorescence analysis> ·Analysis conditions Equipment: Wavelength-dispersive fully automated X-ray fluorescence analyzer (product name: Axios advanced, manufactured by Malvern Panalytical) Quantitative method: Fundamental parameter method (FP method) Analysis element: B~U Measurement atmosphere: Vacuum Measurement sample: Solid Collimator mask diameter: 27mm Measurement time: Approximately 20 minutes For the measurements, an automated program pre-set to the optimal excitation conditions for each element is used.

[0112] For other values, use the general values ​​recommended by the device. • Sample pretreatment Approximately 3g of toner is placed in a 27mm diameter polyvinyl chloride ring and pressed with 200kN to form the sample. The weight and thickness of the toner used are recorded. ·analysis Analysis program: SpectraEvaluation (version 5.0L) Analysis conditions: oxide form Balanced ingredients: CH2 (The CHO ratio of the resin is measured in advance using analytical methods such as NMR, and then balanced.) For other values, use the general values ​​recommended by the device. ·Analysis condition details Spectroscopic crystal: LiF220, LiF200, Ge111, TIAP, PX1 Tube current: Adjust within the range of 40-80mA depending on the element. Tube voltage: Varies within the range of 30-60kV depending on the element. However, the product of the tube current and tube voltage should always be 2.4 kW. Tube filter: Brass (400 μm) is used depending on the element.

[0113] Measurements are performed under the above conditions, and elements originating from strontium titanate are identified based on the peak positions of the obtained X-rays. The strontium titanate content is then calculated from the count rate (unit: cps), which is the number of X-ray photons per unit time.

[0114] The toner particles can be manufactured using known methods, including kneading and grinding methods and wet manufacturing methods. From the viewpoint of uniform particle size and shape control, wet manufacturing methods are preferred. Examples of wet manufacturing methods include suspension polymerization, dissolution and suspension, emulsion polymerization and agglutination, and emulsion and agglutination, with emulsion and agglutination being more preferred. In other words, it is preferable that the toner particles are emulsion and agglutination toner particles.

[0115] The emulsification and coagulation method first involves preparing dispersions of various materials, such as binder resin fine particles and colorants. These dispersions are then mixed and dispersed, with the addition of a dispersion stabilizer as needed. Subsequently, a coagulation agent is added to achieve the desired toner particle size, and then, or simultaneously with coagulation, fusion occurs between the resin fine particles. Furthermore, if necessary, heat is used to control the shape and form the toner particles.

[0116] The following can be used as dispersion stabilizers: Known cationic surfactants, anionic surfactants, and nonionic surfactants can be used as surfactants.

[0117] Examples of inorganic dispersion stabilizers include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate, bentonite, silica, and alumina.

[0118] Examples of organic dispersion stabilizers include polyvinyl alcohol, gelatin, methylcellulose, methylhydroxypropylcellulose, ethylcellulose, sodium salts of carboxymethylcellulose, and starch.

[0119] As flocculants, in addition to surfactants with opposite polarity to those used in the dispersion stabilizers mentioned above, inorganic salts and inorganic metal salts with a valency of 2 or higher can be suitably used. In particular, inorganic metal salts are preferred because they allow for easy control of flocculation and toner charging by ionizing polyvalent metal elements in an aqueous medium.

[0120] Preferred inorganic metal salts include metal salts of calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, iron chloride, aluminum chloride, and aluminum sulfate, as well as inorganic metal salt polymers of polyferrous chloride, polysilica iron, polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Among these, aluminum salts and their polymers, and polysilica iron are particularly preferred.

[0121] Generally, to obtain a sharper particle size distribution, it is preferable that the inorganic metal salt has a valency of 2 rather than 1, and 3 or higher rather than 2. Furthermore, even with the same valency, an inorganic metal salt polymer is more suitable.

[0122] Examples of external additive devices include double-con mixers, V-type mixers, drum-type mixers, super mixers, FM mixers (manufactured by Nippon Coke Industries Co., Ltd.), Nauter mixers, and mechanohybrid mixers. To control the coating state of the external additive, the rotation speed, processing time, jacket water temperature, and water volume of the above-mentioned external additive device can be adjusted to prepare the toner.

[0123] From the viewpoint of high image resolution and detail, it is preferable that the weight-average particle size of the toner particles be between 3.0 μm and 10.0 μm.

[0124] <Process cartridges and electrophotographic equipment> Figure 1 shows an example of a schematic configuration of an electrophotographic apparatus according to the present invention, which includes a process cartridge.

[0125] In Figure 1, the cylindrical (drum-shaped) electrophotographic photoreceptor 1 is rotated around axis 2 in the direction of the arrow at a predetermined peripheral speed (process speed). During the rotation process, the surface of the electrophotographic photoreceptor 1 is charged to a predetermined positive or negative potential by the charging means 3. Next, the charged surface of the electrophotographic photoreceptor 1 is irradiated with image exposure light 4 from an exposure means (not shown), and an electrostatic latent image corresponding to the desired image information is formed. The image exposure light 4 is, for example, light output from an exposure means such as slit exposure or laser beam scanning exposure, which is intensity-modulated in accordance with the time-series electrodigital image signal of the desired image information.

[0126] The electrostatic latent image formed on the surface of the electrophotographic photoreceptor 1 is developed (normal development or reverse development) by toner supplied from the developing means 5, and a toner image is formed on the surface of the electrophotographic photoreceptor 1. The toner image formed on the surface of the electrophotographic photoreceptor 1 is transferred to the transfer medium 7 by the transfer means 6. At this time, a bias voltage with the opposite polarity to the charge held by the toner is applied to the transfer means 6 from a bias power supply (not shown). If the transfer medium 7 is paper, the transfer medium 7 is taken out from the paper feed unit (not shown) and fed between the electrophotographic photoreceptor 1 and the transfer means 6 in synchronization with the rotation of the electrophotographic photoreceptor 1.

[0127] The transfer medium 7, onto which the toner image has been transferred from the electrophotographic photoreceptor 1, is separated from the surface of the electrophotographic photoreceptor 1 and then transported to the fixing means 8, where it undergoes a toner image fixing process and is printed out as an image-forming product (print, copy) outside the electrophotographic device. After the toner image has been transferred to the transfer medium 7, the surface of the electrophotographic photoreceptor 1 is cleaned by the cleaning means 9, which removes any attached substances such as toner (transfer residue toner). With cleanerless systems developed in recent years, the transfer residue toner can also be removed directly with a developer or similar device. Furthermore, the surface of the electrophotographic photoreceptor 1 is subjected to static discharge treatment by pre-exposure light 10 from a pre-exposure means (not shown) and then used repeatedly for image formation.

[0128] Furthermore, 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, a process cartridge is formed by housing and supporting together multiple components from the above-mentioned components such as the electrophotographic photoreceptor 1, charging means 3, developing means 5, and cleaning means 9 in a container. This process cartridge can be configured to be detachably attached to the electrophotographic apparatus body. For example, at least one selected from the charging means 3, developing means 5, and cleaning means 9 is supported together with the electrophotographic photoreceptor 1 to form a cartridge. Using guide means 12 such as rails on the electrophotographic apparatus body, a process cartridge 11 can be made detachably attached to the electrophotographic apparatus body.

[0129] The image exposure light 4 may be reflected or transmitted light from the original document if the electrophotographic device is a copier or printer. Alternatively, it may be light emitted by scanning a laser beam, driving an LED array, or driving a liquid crystal shutter array, which are performed according to a signal obtained by reading the original document with a sensor. The electrophotographic photoreceptor 1 can be widely applied to electrophotographic application fields such as laser beam printers, CRT printers, LED printers, fax machines, liquid crystal printers, and laser plate making. [Examples]

[0130] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples unless it exceeds the gist of the invention. In the following examples, "parts" refers to mass unless otherwise specified.

[0131] [Manufacturing of polyarylate resin (PAR)] (Synthesis of resin (PAR-1)) The following shows the synthesis method for resin (PAR-1) as an example of resin X synthesis.

[0132] A three-necked flask equipped with a thermometer, a three-way stopcock, and a dropping funnel was used as the reaction vessel. The following materials were prepared. • Monomer compound (BP-2): 12.3 mmol • Monomer compound (BP-5): 28.7 mmol • End-termination agent: 2,6-dimethylphenol (DMP): 0.413 mmol Sodium hydroxide: 98 mmol • Benzyltributylammonium chloride: 0.384 mmol These were placed in a reaction vessel, and the air inside the vessel was replaced with argon gas. 300 mL of water was added to the contents of the reaction vessel. The contents of the reaction vessel were stirred at 50°C for 1 hour. The contents of the reaction vessel were cooled to 10°C to obtain alkaline aqueous solution A.

[0133] Next, 20.8 mmol of dicarboxylic acid dichloride of monomer compound (DC-1) and 11.2 mmol of dicarboxylic acid dichloride of monomer compound DC-4 were dissolved in 150 mL of chloroform. This yielded chloroform solution B.

[0134] To an alkaline aqueous solution A, chloroform solution B was slowly added dropwise over 110 minutes using a dropping funnel. The contents of the reaction vessel were stirred for 4 hours while adjusting the temperature (liquid temperature) to 15±5°C to allow the polymerization reaction to proceed. The upper layer (aqueous layer) of the contents of the reaction vessel was removed using a decanter to obtain the organic layer.

[0135] Next, 400 mL of deionized water was added to the Erlenmeyer flask. The obtained organic layer was then added to the Erlenmeyer flask. 400 mL of chloroform and 2 mL of acetic acid were then added to the Erlenmeyer flask. The contents of the Erlenmeyer flask were stirred at room temperature (25°C) for 30 minutes. The upper layer (aqueous layer) of the contents of the Erlenmeyer flask was removed using a decanter to obtain the organic layer. The obtained organic layer was washed with 1 L of deionized water using a separatory funnel. The washing with deionized water was repeated 5 times to obtain a water-washed organic layer.

[0136] Next, the water-washed organic layer was filtered to obtain a filtrate. The filtrate was slowly added dropwise to 1 L of methanol to obtain a precipitate. The precipitate was removed by filtration. The removed precipitate was vacuum-dried at 70°C for 12 hours. As a result, a resin (PAR-1) with a viscosity-average molecular weight of 54,000 was obtained.

[0137] (Synthesis of resin (PAR-2) to resin (PAR-13)) Except for changing the ratio of bisphenol and dicarboxylic acid, and the end-stop agent, the resins were synthesized using the same method as for resin (PAR-1), and the resins listed in Table 1 were obtained. Note that the viscosity-average molecular weight of the polyarylate resin (PAR) increases as the amount of end-stop agent added decreases.

[0138] [Table 1]

[0139] The proportions of bisphenols in Table 1 represent the ratio of the amount of each bisphenol to the total amount of two types of bisphenols in each resin (PAR-1) to resin (PAR-13). Similarly, the proportions of dicarboxylic acids represent the ratio of the amount of each dicarboxylic acid to the total amount of two types of dicarboxylic acids.

[0140] Furthermore, BP-6 and DC-5 in Table 1 are compounds represented by the following formulas (BP-6) and (DC-5), respectively. [ka] [ka]

[0141] <Manufacturing of electrophotographic photoconductors> The film thickness of each layer in the electrophotographic photoreceptor, excluding the charge generation layer, was determined either by using an eddy current film thickness gauge (Fischerscope, Fischer Instruments) or by converting the specific gravity from the mass per unit area. The film thickness of the charge generation layer was measured by pressing a spectrophotometer (product name: X-Rite504 / 508, X-Rite) against the surface of the photoreceptor and converting the Macbeth density value. For the conversion, a calibration curve obtained in advance from the film thickness measurements of the charge generation layer obtained by observing cross-sectional SEM images of the photoreceptor was used.

[0142] [Photoconductor 1] <Conductive layer> An aluminum cylinder (JIS-A3003, aluminum alloy) with a diameter of 24 mm and a length of 257.5 mm was used as the support (conductive support).

[0143] Next, I prepared the following materials. 214 titanium oxide (TiO2) particles (average primary particle size 230 nm) coated with oxygen-deficient tin oxide (SnO2) as a metal oxide particle. • Phenolic resin as a binding material (phenolic resin monomer / oligomer) (product name: Priofen J-325, manufactured by DIC Corporation, resin solids content: 60% by mass) 132 parts 98 parts of 1-methoxy-2-propanol as a solvent

[0144] These materials were placed in a sand mill using 450 glass beads with a diameter of 0.8 mm, and dispersed under the following conditions: rotation speed: 2000 rpm, dispersion processing time: 4.5 hours, and cooling water temperature set at 18°C ​​to obtain a dispersion. The glass beads were removed from this dispersion using a mesh (mesh opening: 150 μm). Silicone resin particles (product name: Tospearl 120, manufactured by Momentive Performance Materials Co., Ltd., average particle size 2 μm) were added to the obtained dispersion as a surface roughening agent. The amount of silicone resin particles added was set to 10% by mass relative to the total mass of metal oxide particles and binder material in the dispersion after the glass beads were removed. In addition, silicone oil (product name: SH28PA, manufactured by Toray Dow Corning Co., Ltd.) was added to the dispersion as a leveling agent at a concentration of 0.01% by mass relative to the total mass of metal oxide particles and binder material in the dispersion.

[0145] 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 metal oxide particles, binder, and surface roughening agent (i.e., the mass of solids) in the dispersion was 67% by mass relative to the mass of the dispersion. After that, the mixture was stirred to prepare a coating solution for the conductive layer. This coating solution for the conductive layer was applied to a support by immersion, and the support was heated at 140°C for 1 hour to form a conductive layer with a film thickness of 30 μm.

[0146] <Underlayer> Surface-treated titanium dioxide (number-mean primary particle size 10 nm) was prepared. The titanium dioxide was surface-treated using alumina and silica, and the surface-treated titanium dioxide was further surface-treated using methyl hydrogen polysiloxane while wet-dispersing it. Next, I prepared the following materials. • 2 parts by mass of surface-treated titanium oxide • Polyamide resin (Toray Industries, Inc.'s "Amiran CM8000," a quatern-copolymer polyamide resin of polyamide 6, polyamide 12, polyamide 66, and polyamide 610) 1 part by mass • 10 parts by mass of methanol • 1 part by mass of butanol · 1 part by mass of toluene These were mixed using a bead mill for 5 hours to obtain a coating solution for the undercoat layer. Then, the obtained coating solution for the undercoat layer was dip-coated onto the conductive layer formed as described above to form a coating film, and the coating film was heat-dried at 130 °C for 30 minutes to form an undercoat layer with a film thickness of 1.5 μm.

[0147] <Charge generation layer> The following materials were prepared. · 1.5 parts by mass of Y-type titanyl phthalocyanine as a charge generating substance · 1 part by mass of polyvinyl acetal resin ("Esrec BX-5" manufactured by Sekisui Chemical Co., Ltd.) These were added to a solvent containing 40 parts by mass of propylene glycol monomethyl ether and 40 parts by mass of tetrahydrofuran. Using a bead mill, these materials and the solvent were mixed for 12 hours to disperse the materials in the solvent and prepare a coating solution for the charge generation layer. The obtained coating solution for the charge generation layer was dip-coated onto the undercoat layer to form a coating film, and the coating film was heat-dried at a temperature of 100 °C for 10 minutes to form a charge generation layer with a film thickness of 0.25 μm.

[0148] <Charge transport layer (surface layer)> The following materials were prepared. · 6 parts by mass of charge transport substance (H-1) · 4.5 parts by mass of resin X (resin PAR-1) as a binder resin · 5.5 parts by mass of a polyarylate resin containing a structural unit represented by the following formula (P16) · 67.5 parts by mass of tetrahydrofuran · 22.5 parts by mass of toluene These were mixed to prepare a coating solution for the charge transport layer. The obtained coating solution for the charge transport layer was dip-coated onto the charge generation layer to form a coating film, and the coating film was heat-dried at a temperature of 120 °C for 30 minutes to form a charge transport layer (surface layer) with a film thickness of 18 μm.

[0149]

Chemical formula

[0150] (Analysis of the resin component of the photoreceptor 1) By 1H-nuclear magnetic resonance analysis in deuterated chloroform of the polymer component recovered from the obtained photoreceptor, 1 an H-NMR spectrum was obtained. The obtained 1 H-NMR spectrum had peaks at 8.22 ± 0.02, 7.18 ± 0.02, 7.16 ± 0.02, 7.10 ± 0.02, 7.06 ± 0.02, 7.04 ± 0.02, 2.28 ± 0.02, 2.20 ± 0.02, 1.59 ± 0.02, and 1.54 ± 0.02 ppm. As a result, it was specified that the photoreceptor contained each structural unit represented by Formula (1), Formula (2), Formula (3), and Formula (4). Further, the ratios of the amounts of substance of each structural unit represented by Formula (1), Formula (2), Formula (3), and Formula (4) were as shown in Table 1 based on the integration ratio of the above peaks.

[0151] [Photoreceptors 2 to 18, Photoreceptors A to F] Photoreceptors 2 to 18 and Photoreceptors A to F were produced in the same manner as the method described in the above <Photoreceptor 1>, except that the types and amounts of Resin X and the charge transport material used for forming the charge transport layer (surface layer) were changed as shown in Table 2.

[0152] [Table 2]

[0153] Hereinafter, production examples of toner will be described. [Preparation Example of the Binder Resin Particle Dispersion Liquid] 78.0 parts of styrene, 20.7 parts of butyl acrylate, 1.3 parts of acrylic acid as a carboxyl group-introducing monomer, and 3.2 parts of n-lauryl mercaptan were mixed and dissolved. An aqueous solution prepared by mixing 1.5 parts of Neogen RK (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) with 150 parts of ion-exchanged water was added to this solution and dispersed.

[0154] While slowly stirring for another 10 minutes, an aqueous solution of 0.3 parts potassium persulfate mixed with 10 parts deionized water was added. After nitrogen purging, emulsion polymerization was carried out at 70°C for 6 hours. After polymerization was complete, the reaction solution was cooled to room temperature, and deionized water was added to obtain resin particle dispersion 1 with a solid content concentration of 12.5% ​​by mass and a volume-based median diameter of 0.2 μm.

[0155] To measure the acid value, some of the obtained resin particles were washed with pure water to remove the surfactant and then dried under reduced pressure. The acid value of the resin was measured and confirmed to be 9.5 mg KOH / g.

[0156] <Example of preparation of release agent dispersion> 100 parts of behenyl behenate (melting point: 72.1°C) and 15 parts of Neogen RK were mixed with 385 parts of deionized water and dispersed for approximately 1 hour using a wet jet mill JN100 (manufactured by Jokoh Co., Ltd.) to obtain a release agent dispersion. The concentration of the release agent dispersion was 20% by mass.

[0157] <Example of preparation of a colorant dispersion> As a coloring agent, 100 parts of carbon black "Nipex35 (manufactured by Orion Engineered Carbons)" and 15 parts of Neogen RK were mixed with 885 parts of ion-exchanged water, and the mixture was dispersed for approximately 1 hour using a wet jet mill JN100 to obtain a coloring agent dispersion.

[0158] <Example of Toner 1 manufacturing> 265 parts of resin particle dispersion, 10 parts of mold release agent dispersion, and 10 parts of colorant dispersion were dispersed using a homogenizer (IKA Ultra-Turrax T50). The temperature inside the container was adjusted to 30°C while stirring, and a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 8.0.

[0159] As a flocculant, an aqueous solution prepared by dissolving 0.25 parts of aluminum chloride in 10 parts of ion-exchanged water was added over 10 minutes while stirring at 30°C. After leaving it standing for 3 minutes, the temperature was raised, and the temperature was raised to 50°C to generate aggregated particles. In that state, the particle size of the aggregated particles was measured using a "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter). When the weight-average particle size reached 6.0 μm, 0.9 parts of sodium chloride and 5.0 parts of neogen RK were added to stop particle growth.

[0160] A 1 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 9.0, and then the temperature was raised to 95°C to spheroidize the aggregated particles. When the average circularity reached 0.980, the temperature was lowered, and it was cooled to room temperature to obtain a toner particle dispersion.

[0161] Hydrochloric acid was added to the obtained toner particle dispersion to adjust the pH to 1.5 or less, and it was left stirring for 1 hour and then solid-liquid separated using a pressure filter to obtain a toner cake. This was reslurried with ion-exchanged water to make a dispersion again, and then solid-liquid separated using the aforementioned filter. Reslurrying and solid-liquid separation were repeated until the electrical conductivity of the filtrate became 5.0 μS / cm or less, and finally solid-liquid separation was performed 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) became 6.0 μm to obtain toner particles.

[0162] With respect to 100 parts of the toner particles obtained above, 0.7 parts of strontium titanate particles (number-average primary particle diameter 70 nm) and 2.5 parts of silica particles (number-average primary particle diameter 12 nm) surface-treated with dimethyl silicone oil were externally added and mixed as external additives. FM10C (manufactured by Nippon Coke & Engineering Co., Ltd.) was used for external addition mixing. The external addition conditions were set such that the lower blade was an A0 blade, the distance from the wall of the deflector was 20 mm, the charged amount of toner particles was 2.0 kg, the rotation speed was 66.6 s -1 , the external addition time was 10 minutes, and cooling water was used at a temperature of 20°C and a flow rate of 10 L / min. Thereafter, it was sieved with a mesh having an opening of 200 μm to obtain toner.

[0163] <Production Example of Toner 2> It was prepared in the same manner as Toner 1, except that aluminum chloride was changed to polysilicon iron PSI-100 (manufactured by Suido Kiko Co., Ltd.) as the flocculant.

[0164] <Production Example of Toner 3> It was prepared in the same manner as Toner 1, except that aluminum chloride was changed to magnesium chloride as the flocculant.

[0165] <Example 1> <Evaluation> Using the electrophotographic photoreceptor and toner prepared above, the following evaluations were carried out. The evaluation results are shown in Table 3.

[0166] As the electrophotographic apparatus, a modified machine of a laser beam printer (trade name HP LaserJet Enterprise Color M553dn) manufactured by Hewlett-Packard Company was used. The modifications were made so that the applied voltage to the charging roller could be adjusted and measured, the image exposure light amount could be adjusted and measured, and the applied voltage in the transfer process could be adjusted and measured.

[0167] The toner was removed from the black toner cartridge and replaced with the prepared Toner 1. Also, Photoreceptor 1 was installed in the black toner cartridge. Subsequently, in a low-temperature and low-humidity environment of 15°C and 10% RH, 12,000 image outputs were performed on A4-sized plain paper using a test chart with a printing ratio of 1.2%. As the charging conditions, the dark potential was -560V, and as the exposure conditions, the image exposure light amount was adjusted to 0.27 μJ / cm 2 to. The paper used was plain paper CS-680 (68 g / m 2 [[ID=Z1]])(Canon Marketing Japan Inc.).

[0168] [Evaluation of Abrasion Resistance] The wear amount of the charge transport layer was determined from the difference in the photoreceptor film thickness before and after 12,000 repeated image outputs.

[0169] [Evaluation of Transferability] After 12,000 repeated image outputs, a 30mm wide solid image was printed vertically on plain paper CS-680. Subsequently, the output during solid image formation was stopped, and the remaining toner on the electrophotographic photoreceptor was collected using transparent polyester tape (Polyester Tape 5511 Nichiban).

[0170] The density of residual toner was measured using the following method. A transparent tape containing residual toner peeled from the surface of an electrophotographic photoreceptor and a new transparent tape were each attached to high-whiteness paper (GFC081 Canon). The density D1 of the transparent tape containing the residual toner and the density D0 of the new transparent tape were then measured using an X-Rite color reflectance densitometer (X-rite 500 Series).

[0171] The difference "D1-D0" obtained from the measurement was defined as the concentration of the remaining toner after transfer. A smaller value for the remaining toner after transfer indicates less toner remaining. (Evaluation Criteria) A: Transcription residue concentration is less than 0.02 B: Transcription residue concentration is 0.02 or higher and less than 0.06 C: Transcription residue concentration is 0.06 or higher and less than 0.10 D: Transcription residue concentration is 0.10 or higher The results are shown in Table 3.

[0172] [Table 3]

[0173] <Examples 2-22> In Examples 2-22, process cartridges were prepared using photoreceptors 2-18 and toners 1-3, respectively, as shown in Table 3, and image output tests similar to those in Example 1 were performed. The evaluation results for each are shown in Table 3.

[0174] <Comparative Examples 1-6> In Comparative Examples 1 to 6, process cartridges were prepared using photoreceptors A to F and toner 1, respectively, as shown in Table 3, and image output tests similar to those in Example 1 were performed. The evaluation results for each are shown in Table 3.

[0175] Embodiments according to the present invention include the following configurations. [Configuration 1] An electrophotographic photoreceptor having a surface layer containing resin X as a binder resin, A charging means for charging the surface of the electrophotographic photoreceptor, An exposure means for irradiating light onto the surface of the charged electrophotographic photoreceptor to form an electrostatic latent image, A developing means that supplies toner to the electrostatic latent image to form a toner image, A transfer means for transferring the toner image onto a transfer medium, It has, The toner contains strontium titanate as an external additive, The resin X is a polyarylate resin having structural units represented by formula (1), formula (2), formula (3), and formula (4). An electrophotographic apparatus characterized by the following features. [ka] [ka] [ka] [ka] (The asterisk (*) in equations (1) to (4) represents the bonding site with an adjacent structural unit.) [Configuration 2] The electrophotographic apparatus according to configuration 1, wherein the ratio n2 / n1 of the number of structural units represented by formula (4) contained in the resin X to the number of structural units represented by formula (2) contained in the resin X is 1.0 or greater. [Configuration 3] The electrophotographic apparatus according to configuration 1 or 2, wherein the total content of structural units represented by formula (1), formula (2), formula (3), and formula (4) in the binder resin in the surface layer is 50% by mass or more and 100% by mass or less. [Structure 4] An electrophotographic apparatus according to any one of configurations 1 to 3, wherein the ratio of the mass of strontium titanate to the mass of toner particles in the toner is 0.1% by mass or more and 1.0% by mass or less. [Explanation of Symbols]

[0176] 1: Electrophotographic photoreceptor 2: Axis 3: Charging means 4: Image exposure light 5: Development method 6: Transfer method 7: Transfer medium 8: Image fixing means 9: Cleaning methods 10: Pre-exposure light 11: Process Cartridge 12: Means of Guidance

Claims

1. An electrophotographic photoreceptor having a surface layer containing resin X as a binder resin, A charging means for charging the surface of the electrophotographic photoreceptor, An exposure means for irradiating light onto the surface of the charged electrophotographic photoreceptor to form an electrostatic latent image, A developing means that supplies toner to the electrostatic latent image to form a toner image, A transfer means for transferring the toner image onto a transfer medium, It has, The toner contains strontium titanate as an external additive, The resin X is a polyarylate resin having structural units represented by formula (1), formula (2), formula (3), and formula (4). An electrophotographic apparatus characterized by the following features. 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 【Chemistry 4】 (The asterisk (*) in equations (1) to (4) represents the bonding site with an adjacent structural unit.)

2. The electrophotographic apparatus according to claim 1, wherein the ratio n2 / n1 of the number of structural units represented by formula (4) contained in the resin X to the number of structural units represented by formula (2) contained in the resin X is 1.0 or more.

3. The electrophotographic apparatus according to claim 1 or 2, wherein the total content of the structural units represented by formula (1), formula (2), formula (3), and formula (4) in the binder resin in the surface layer is 50% by mass or more and 100% by mass or less.

4. The electrophotographic apparatus according to claim 1 or 2, wherein the ratio of the mass of strontium titanate to the mass of toner particles in the toner is 0.1% by mass or more and 1.0% by mass or less.

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