Electrophotographic device

Abstract

The present invention provides an electrophotographic apparatus comprising a corona charger and an electrophotographic photoreceptor capable of suppressing fluctuations in post-exposure potential during long-term repeated use. [Solution] An electrophotographic apparatus comprising an electrophotographic photoreceptor and a corona charger for positively charging the electrophotographic photoreceptor, wherein the electrophotographic photoreceptor has a single-layer photosensitive layer, the photosensitive layer contains a charge generating substance, a hole transporting substance, an electron transporting substance, and a binder resin, and the binder resin contains a polyester resin having a specific structural unit.

Description

[Technical Field]

[0001] This invention relates to an electrophotographic apparatus. [Background technology]

[0002] An electrophotographic photoreceptor (hereinafter also referred to as a photoreceptor) is used as an image carrier in an electrophotographic image forming apparatus (for example, a printer or multifunction device) (hereinafter also referred to as an electrophotographic apparatus).

[0003] In electrophotographic image forming devices such as photocopiers and printers, a photoreceptor is uniformly charged to a predetermined polarity, and an electrostatic latent image is formed by exposure to light based on predetermined image information. Subsequently, this electrostatic latent image is developed by a development method such as contact development to form a toner image on the surface of the image carrier. The toner image thus formed on the surface of the image carrier is transferred to transfer paper using electrostatic force with a transfer roller or a corona charger for transfer. The transfer paper with the transferred toner image is introduced into a fixing device, and image formation is performed by fixing the toner image to the surface of the transfer paper using heat and pressure.

[0004] In the image forming apparatus described above, corona chargers are widely used as the charging devices for charging the photoreceptor. Because corona charging does not involve contact between the charging component and the photoreceptor, the charging component remains clean even after prolonged repeated use, uniform charging can be achieved, and high image quality can be maintained even after prolonged repeated use. However, corona charging has drawbacks, such as the generation of discharge products like ozone, NOx, and ions due to its charging mechanism, which can accelerate the degradation of the photoreceptor.

[0005] Examples of electrophotographic photoreceptors include single-layer electrophotographic photoreceptors and multilayer electrophotographic photoreceptors. A single-layer electrophotographic photoreceptor has a single photosensitive layer that has both charge generation and charge transport functions. Compared to electrophotographic photoreceptors with multilayer photosensitive layers, electrophotographic photoreceptors with a single-layer photosensitive layer have a simpler layer structure, resulting in lower manufacturing costs, and also excel in high resolution because charge is generated near the surface of the photosensitive layer.

[0006] As mentioned above, single-layer photoreceptors have charge-generating material near the surface, making them susceptible to the influence of gaseous and ionic components. When combined with corona charging, this leads to degradation of the photosensitive layer, resulting in a problem of low potential stability during long-term repeated use.

[0007] Patent Document 1 describes how electrostatic degradation can be suppressed by using a polyarylate resin having a specific structure in combination with an electron transport material and a hole transport material in an electrophotographic photoreceptor. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2020-118706 [Overview of the project] [Problems that the invention aims to solve]

[0009] According to the inventors' investigation, while the electrophotographic photoreceptor described in Patent Document 1 can suppress the deterioration of its charge properties during long-term repeated use, it has become clear that fluctuations occur in the post-exposure potential in electrophotographic devices using corona charging.

[0010] Therefore, an object of the present invention is to provide an electrophotographic apparatus comprising a corona charger and an electrophotographic photoreceptor capable of suppressing fluctuations in post-exposure potential during repeated use over a long period of time. [Means for solving the problem]

[0011] The above objective is achieved by the present invention as follows: That is, the electrophotographic apparatus according to the present invention is An electrophotographic apparatus comprising an electrophotographic photoreceptor and a corona charger for positively charging the electrophotographic photoreceptor, The electrophotographic photoreceptor has a single-layer photosensitive layer, The photosensitive layer contains a charge generating material, a hole transporting material, an electron transporting material, and a binder resin. The binder resin comprises a polyester resin having structural units represented by the following formula (a) and structural units represented by the following formula (1). The polyester resin is characterized in that 70 mol% or more of the structural units represented by the following formula (a) are structural units represented by the following formula (2). [ka] (In formula (a), X represents a divalent organic group that does not have an ester bond.) [ka] [ka] [Effects of the Invention]

[0012] According to the present invention, an electrophotographic apparatus can be provided that comprises a corona charger and an electrophotographic photoreceptor capable of suppressing fluctuations in post-exposure potential during repeated use over a long period of time. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example of the layer structure of the electrophotographic photoreceptor used in the present invention. [Figure 2] This figure shows an example of the layer structure of the electrophotographic photoreceptor used in the present invention. [Figure 3] This figure shows an example of a schematic configuration of an electrophotographic apparatus according to the present invention. [Figure 4]This figure shows an example of a schematic configuration of an image forming unit included in an electrophotographic apparatus according to the present invention. [Modes for carrying out the invention]

[0014] The present invention will be described in detail below with reference to preferred embodiments. As a result of diligent research, the inventors have found that the above problem can be solved by configuring the electrophotographic apparatus as follows.

[0015] Specifically, the electrophotographic apparatus comprises an electrophotographic photoreceptor and a corona charger for positively charging the electrophotographic photoreceptor, wherein the electrophotographic photoreceptor has a single-layer photosensitive layer. The photosensitive layer contains a charge generating material, a hole transporting material, an electron transporting material, and a binder resin. The binder resin contains a polyester resin having structural units represented by the following formula (a) and structural units represented by the following formula (1). Furthermore, 70 mol% or more of the structural units represented by the following formula (a) contained in the polyester resin are structural units represented by the following formula (2). [ka] (In formula (a), X represents a divalent organic group that does not have an ester bond.) [ka] [ka]

[0016] The inventors believe that the electrophotographic apparatus with the above configuration is effective in achieving both the suppression of charge degradation during long-term repeated use and the suppression of fluctuations in post-exposure potential, as follows.

[0017] First, by using a corona charger as the charging method, contamination of the charging components can be suppressed, allowing the photoreceptor to be uniformly charged even with long-term repeated use. However, corona charging generates discharge products such as ozone, NOx, and ions, which degrade the photoreceptor. Specifically, the charge-generating materials, electron-transporting materials, and hole-transporting materials contained in the photosensitive layer degrade, causing fluctuations in the post-charging potential and post-exposure potential.

[0018] Patent Document 1 describes how combining a polyarylate resin of a specific structure with a hole transport material and an electron transport material can prevent the intrusion of gas components generated by corona charging, thereby suppressing the decrease in chargeability. However, the present inventors have found that in the electrophotographic photoreceptor described in Patent Document 1, fluctuations in the post-exposure potential occur during long-term repeated use in an electrophotographic device using corona charging. The present inventors surmise that this is because positive ions generated by positively polarized corona charging attack the electron transport material in the photosensitive layer, thereby degrading its ability.

[0019] As a result of diligent research, the inventors have found that by including a polyester resin having the above-mentioned structural unit in the photosensitive layer of an electrophotographic photoreceptor, fluctuations in the post-exposure potential during long-term repeated use can be suppressed.

[0020] The structural unit represented by formula (2) has a highly electron-accepting structure. Furthermore, when the structural unit represented by formula (2) is bonded with the structural unit represented by formula (1), it undergoes resonance stabilization, resulting in even higher electron-acceptance. The inventors surmise that an electrophotographic photoreceptor containing a polyester resin having the structural units represented by formula (1) and formula (2) prevents positive ions from entering the photosensitive layer, thereby preventing degradation of the electron transport material.

[0021] Furthermore, the polyester resin described above has high packing properties and high density because it contains many identical ether structures. Therefore, the inventors surmise that it can prevent the attack of positive ion components on electron transport materials, particularly those present near the surface of the photoreceptor, and as a result, it can suppress fluctuations in potential after exposure. The configuration of the electrophotographic photoreceptor in the electrophotographic apparatus according to the present invention will be described in detail below.

[0022] [Electrophotographic photoconductor] The electrophotographic photoreceptor used in the present invention is a single-layer electrophotographic photoreceptor (hereinafter sometimes referred to as a single-layer photoreceptor) having at least a support and a single-layer photosensitive layer formed on the support. One method for manufacturing the electrophotographic photoreceptor of the present invention is to prepare coating solutions for each layer, as described later, apply them in the desired order, and then dry them. Methods for applying the coating solutions include immersion coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, and ring coating. Among these, immersion coating is preferred from the viewpoint of efficiency and productivity.

[0023] The single-layer photoreceptor used in the present invention will be described below with reference to Figures 1 and 2. Figures 1 and 2 are partial cross-sectional views showing examples of the layer structure of a single-layer photoreceptor, respectively.

[0024] As shown in Figure 1, the single-layer photoreceptor 1 comprises, for example, a conductive support 2 and a photosensitive layer 3. The photosensitive layer 3 of the single-layer photoreceptor 1 is a single-layer (1-layer) single-layer photosensitive layer. The photosensitive layer 3 contains a charge generating material, a hole transporting material, an electron transporting material, and a binder resin.

[0025] As shown in Figure 2, the single-layer photoreceptor 1 may further include an undercoat layer 4 (intermediate layer) in addition to the conductive support 2 and the photosensitive layer 3. That is, in the single-layer photoreceptor 1, the photosensitive layer 3 may be provided directly on the support 2 as shown in Figure 1, or it may be provided on the support 2 via an undercoat layer 4 as shown in Figure 2.

[0026] The thickness of the photosensitive layer 3 is not particularly limited, but is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less. The support structure and each layer will be described below.

[0027] <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. 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.

[0028] <Underlayer> In the present invention, an undercoat layer may be provided on the support. 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The 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.

[0035] 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.

[0036] <Single-layer photosensitive layer> The electrophotographic photoreceptor used in the present invention has a single-layer photosensitive layer on a support, or on an undercoat layer provided on the support. The single-layer photosensitive layer in the present invention comprises at least a binder resin, a charge generating material, a hole transport material, and an electron transport material.

[0037] [Binder resin] The binder resin used in the photosensitive layer contains a polyester resin having structural units represented by formula (a) and structural units represented by formula (1), wherein 70 mol% or more of the structural units represented by formula (a) contained in the polyester resin are structural units represented by formula (2). [ka] (In formula (a), X represents a divalent organic group that does not have an ester bond.) [ka] [ka]

[0038] The structural unit represented by formula (2) is a highly electron-accepting structure. Furthermore, when the structural unit represented by formula (2) is bonded with the structural unit represented by formula (1), it undergoes resonance stabilization, resulting in even higher electron-acceptance. An electrophotographic photoreceptor containing a polyester resin having the structural units represented by formula (1) and formula (2) is thought to prevent positive ions from entering the photosensitive layer, thereby preventing degradation of the electron transport material.

[0039] In addition to the structural unit represented by the formula (1) and the structural unit represented by the formula (2), the above polyester resin may further contain a structural unit represented by the following formula (3). [Chemical formula]

[0040] Also, in addition to the structural unit represented by the formula (1) and the structural unit represented by the formula (2), the above polyester resin may further contain a structural unit represented by the following formula (4) as the structural unit represented by the formula (a). [Chemical formula]

[0041] By containing the structural unit represented by the formula (3) or the structural unit represented by the formula (4) in the above polyester resin, the solubility of the polyester resin in a solvent is improved, and a photosensitive layer can be formed well.

[0042] Let the ratio of the amount of substance of the structural unit represented by the formula (1) to the total amount of substance of the structural units constituting the above polyester resin be M1, and the ratio of the amount of substance of the structural unit represented by the formula (3) be M3. At this time, M1 / (M1 + M3) is preferably larger from the viewpoint of the block of the positive ion component. On the other hand, M1 / (M1 + M3) is preferably 0.50 or less from the viewpoint of solubility in a solvent. That is, it is preferable that the M1 and the M3 satisfy the relationship represented by 0 < M1 / (M1 + M3) ≤ 0.50. By improving the solubility in a solvent, a photosensitive layer can be formed well.

[0043] In the above polyester resin, the sum of the ratio of the amount of substance of the structural unit represented by the formula (2) and the ratio of the amount of substance of the structural unit represented by the formula (4) to the total amount of substance of the structural units derived from dicarboxylic acid constituting the polyester resin is preferably 0.50 or more. In the above-mentioned polyester resin, it is preferable that the sum of the ratio of the amount of substance of the structural unit represented by formula (1) and the ratio of the structure represented by formula (3) to the total amount of substance of the bisphenol-derived structural units constituting the polyester resin is greater than 0 and 0.50 or less.

[0044] The photosensitive layer may contain resins other than the polyester resin described above, to the extent that they do not impair the effects of the present invention. Examples of other resins include polycarbonate resin, styrene resin, and acrylic resin. The polyester resin may be, for example, a random copolymer, an alternating copolymer, a periodic copolymer, or a block copolymer. It is preferable that the proportion of polyester resin having structural units represented by formula (1) and structural units represented by formula (a) is 50% by mass or more, relative to the total mass of binder resin contained in the photosensitive layer.

[0045] The viscosity-average molecular weight of the polyester resin is preferably 10,000 or more, more preferably 30,000 or more, and even more preferably 50,000 or more. When the viscosity-average molecular weight of the polyester resin is 10,000 or more, the abrasion resistance of the photoreceptor is improved. On the other hand, the viscosity-average molecular weight of the polyester resin is preferably 80,000 or less, and more preferably 70,000 or less. When the viscosity-average molecular weight of the polyester resin is 80,000 or less, the polyester resin dissolves easily in the solvent for forming the photosensitive layer.

[0046] In the present invention, the polyester resin is composed of a structural unit represented by formula (1) as a bisphenol-derived repeating unit and a structural unit represented by formula (2) as a dicarboxylic acid-derived repeating unit. Furthermore, in the present invention, it is preferable that the polyester resin is further composed of a structural unit represented by formula (3) as a bisphenol-derived repeating unit and a structural unit represented by formula (4) as a dicarboxylic acid-derived repeating unit.

[0047] Examples of bisphenols used to construct bisphenol-derived repeating units include the compound represented by the following formula (BP-1) and the compound represented by the following formula (BP-2). Hereinafter, these may be referred to as compound (BP-1) and compound (BP-2), respectively. Examples of dicarboxylic acids used to construct repeating units derived from dicarboxylic acids include the compound represented by the following formula (DC-1) and the compound represented by the following formula (DC-2). Hereinafter, these may be referred to as compound (DC-1) and compound (DC-2), respectively.

[0048] The amounts of compound (BP-1) and compound (BP-2) added when manufacturing the above polyester resin can be appropriately changed. This allows for adjustment of the bisphenol ratio in the polyester resin (i.e., the content ratio of structural units represented by formula (1) and formula (3)). Similarly, the amount of dicarboxylic acid can be appropriately changed by appropriately changing the amounts of compound (DC-1) and compound (DC-2) added when manufacturing the above polyester resin. This allows for adjustment of the dicarboxylic acid ratio in the polyester resin (i.e., the content ratio of structural units represented by formula (2) and formula (4)). [ka] [ka] [ka] [ka]

[0049] Bisphenols (e.g., compounds (BP-1) and (BP-2)) may be used after being derivatized to aromatic diacetates. Dicarboxylic acids (e.g., compounds (DC-1) and (DC-2)) may also be used after being derivatized. 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 a dicarboxylic acid are each replaced by "-C(=O)-Cl" groups.

[0050] 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.

[0051] The photosensitive layer may contain only a polyester resin having structural units represented by formula (2) and formula (1) as the binder resin, or it may further contain other binder resins. Hereinafter, the polyester resin having structural units represented by formula (2) and formula (1) may be referred to as other binder resins contained in the photosensitive layer.

[0052] Other binder resins contained in the photosensitive layer include, for example, thermoplastic resins, thermosetting resins, and photocurable resins. More specifically, thermoplastic resins include polyester resins other than the polyester resins mentioned above, polycarbonate resins, styrene-based resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, styrene-acrylic acid copolymers, acrylic copolymers, polyethylene resins, ethylene-vinyl acetate copolymers, chlorinated polyethylene resins, polyvinyl chloride resins, polypropylene resins, ionomers, vinyl chloride-vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyvinyl acetal resins, and polyether resins. More specifically, thermosetting resins include silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, and other crosslinkable thermosetting resins. More specifically, photocurable resins include epoxy-acrylic acid resins and urethane-acrylic acid copolymers.

[0053] Component analysis of polymer components recovered from the photosensitive layer in deuterated chloroform 1 Obtained by subjecting to 1H nuclear magnetic resonance analysis. 1 The structure of the polyester resin used in this invention can be determined by 1H nuclear magnetic resonance spectroscopy. The following describes a specific analytical method for the polyester resin in the photosensitive layer when the photoreceptor is cylindrical.

[0054] (Reprecipitation of resin in the photosensitive layer) Cut the photoreceptor using a coping saw at a point 10 cm from the edge of the photoreceptor in the direction of the generatrix. • Wipe the inner surface of the cut 10cm cylinder using a piece of lens tissue soaked in chloroform. To elute the photosensitive layer, immerse a 3cm section of the cut end of the cylindrical body in chloroform. (Pour approximately 60ml of chloroform into a 100mL beaker and immerse the section at room temperature for 5 minutes.) The chloroform solution from which the photosensitive layer has been eluted is concentrated using a rotary evaporator until it reaches 2 mL, at which point the process is stopped. Prepare 50 mL of methanol / acetone mixture (volume ratio 1:1), add the entire concentrated solution dropwise while stirring, and re-settle. • Perform suction filtration using a funnel. (Funnel: SU-40, Filter paper: No. 5C-40, both manufactured by Kiriyama Seisakusho Co., Ltd.) • Collect the residue on the filter paper with a spatula and vacuum dry it (70°C for 1 hour). (NMR measurement) • To prepare the sample for measurement, 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: Sigma-Aldrich Japan Co., Ltd., Chloroform-d, Model No. 612200) (NMR tube: Norell, ST500-7, Model No. S3010) • Perform NMR measurements. 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.

[0055] [Charge-generating material] Examples of charge-generating materials include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metallic naphthalocyanine pigments, squaline pigments, indigo pigments, azulenium pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g., selenium, selenium-tellurium, selenium-arsenide, cadmium sulfide, and amorphous silicon), pyryllium pigments, ancencelon pigments, triphenylmethane pigments, surene pigments, toluidine pigments, pyrazoline pigments, and quinacridone pigments. The photosensitive layer may contain only one type of charge-generating material, or it may contain two or more types of charge-generating materials.

[0056] Phthalocyanine pigments are pigments having a phthalocyanine structure. Examples of phthalocyanine pigments include metal-free phthalocyanines and metal phthalocyanines. Examples of metal phthalocyanines include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. Titanyl phthalocyanine is preferred as the metal phthalocyanine. Titanyl phthalocyanine is a compound represented by the following formula (CGM-1), and metal-free phthalocyanines are compounds represented by the following formula (CGM-2). [ka] [ka]

[0057] Phthalocyanine pigments may be crystalline or amorphous. Examples of metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter sometimes referred to as X-type metal-free phthalocyanine). Examples of titanyl phthalocyanine crystals include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter sometimes referred to as α-type, β-type, and Y-type titanyl phthalocyanine, respectively). For example, in digital optical electrophotographic devices (for example, laser beam printers or facsimiles using light sources such as semiconductor lasers), it is preferable to use a photoreceptor that is sensitive to wavelengths of 700 nm or more. Because they have a high quantum yield in the wavelength range of 700 nm or more, phthalocyanine pigments are preferred as charge generating materials, and metal-free phthalocyanine or titanyl phthalocyanine are more preferred. Furthermore, titanyl phthalocyanine is even more preferred as the charge generating material, and Y-type titanyl phthalocyanine is particularly preferred.

[0058] Y-type titanyl phthalocyanine has a major peak at, for example, 27.2° of the Bragg angle (2θ±0.2°) in its CuKα-characterized X-ray diffraction spectrum. The major peak in a CuKα-characterized X-ray diffraction spectrum is the peak with the first or second highest intensity in the range where the Bragg angle (2θ±0.2°) is between 3° and 40°. Y-type titanyl phthalocyanine does not have a peak at 26.2° in its CuKα-characterized X-ray diffraction spectrum.

[0059] The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, the sample (titanyl phthalocyanine) is placed in the sample holder of an X-ray diffractometer (for example, RIGAK Corporation's "RINT(registered trademark) 1100"). Next, the X-ray diffraction spectrum is measured under the following conditions: X-ray tube Cu, tube voltage 40kV, tube current 30mA, and CuKα characteristic X-ray wavelength 1.542Å. The measurement range (2θ) is, for example, 3° to 40° (start angle 3°, stop angle 40°), and the scanning speed is, for example, 10° / min. The main peak is determined from the obtained X-ray diffraction spectrum, and the Bragg angle of the main peak is read.

[0060] The amount of charge-generating substance in the photosensitive layer is preferably 0.1 parts by mass or more and 50 parts by mass or less, and more preferably 0.5 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of binder resin.

[0061] [Electron transport material] The electron transport material may include at least one selected from the group consisting of the compound represented by formula (10), the compound represented by formula (11), the compound represented by formula (12), the compound represented by formula (13), the compound represented by formula (14), the compound represented by formula (15), and the compound represented by formula (16). It is believed that by including the above electron transport material in the photosensitive layer, the compatibility between the binder resin and the hole transport material described later in the present invention is increased, the homogeneity inside the photosensitive layer is enhanced, and the effects of the present invention can be obtained to a greater extent. [ka] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] (Q in formula (10) 1 and Q 2 , Q in formula (11) 11 , Q 12 , and Q 13 , Q in formula (12) 21 , Q 22 , Q 23 , and Q 24 , Q in formula (13) 31 and Q 32 , Q in formula (14) 41 , Q 42 , Q 43 , and Q 44 , Q in formula (15) 51 , Q 52 , Q 53 , Q 54 , Q 55 , and Q 56 , and Q in formula (16) 61 and Q 62 each independently represents an aryl group having 6 to 14 carbon atoms which may be substituted with at least one substituent selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms and a halogen atom. Y in formula (15) 1 and Y 2 each independently represents an oxygen atom or a sulfur atom.)

[0062] Q in equation (10) 1 and Q 2 Q in equation (11) 11 ~Q 13 Q in equation (12) 21 ~Q 24 Q in equation (13) 31 and Q 32 Q in equation (14) 41 ~Q 44 Q in equation (15) 51 ~Q 56 , and Q in equation (16) 61 and Q 62 Preferably, each independently represents an aryl group having 6 to 14 carbon atoms, which may be substituted with a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms and a halogen atom. 1 and Y 2 It is preferable that this represents an oxygen atom.

[0063] Q in equation (10) 1 and Q 2 Q in equation (11) 11 ~Q 13 Q in equation (12) 21 ~Q 24 Q in equation (13) 31 and Q 32 Q in equation (14) 41 ~Q 44 Q in equation (15) 51 ~Q 56 , and Q in equation (16) 61 and Q 62 When each represents an alkyl group having 1 to 6 carbon atoms, it is preferable that each represents an alkyl group having 1 to 5 carbon atoms, and it is preferable that each represents a methyl group, an ethyl group, a propyl group, a butyl group, or a pentyl group, and it is particularly preferable that each represents a methyl group, an isopropyl group, a tert-butyl group, or a 1,1-dimethylpropyl group.

[0064] Q in equation (10) 1 and Q 2 Q in equation (11) 11~Q 13 Q in equation (12) 21 ~Q 24 Q in equation (13) 31 and Q 32 Q in equation (14) 41 ~Q 44 Q in equation (15) 51 ~Q 56 , and Q in equation (16) 61 and Q 62 When each represents an aryl group having 6 to 14 carbon atoms, it is preferable that each represents an aryl group having 6 to 10 carbon atoms, and more preferably that each represents a phenyl group.

[0065] Here, the alkyl group having 1 to 6 carbon atoms, which may have an aryl group having 6 to 14 carbon atoms as a substituent, is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group or an ethyl group. Furthermore, as halogen atoms that may be substituted for an aryl group having 6 to 14 carbon atoms, fluorine atoms, chlorine atoms, or bromine atoms are preferred, with chlorine atoms being particularly preferred. When an aryl group having 6 to 14 carbon atoms is substituted with substituents, the number of substituents is preferably 1 to 5, and more preferably 1 or 2.

[0066] The aryl group having 6 to 14 carbon atoms, substituted with at least one substituent selected from the group consisting of alkyl groups having 1 to 6 carbon atoms and halogen atoms, is preferably a chlorophenyl group, a dichlorophenyl group, or an ethylmethylphenyl group, and more preferably a 4-chlorophenyl group, a 2,5-dichlorophenyl group, or a 2-ethyl-6-methylphenyl group.

[0067] A preferred example of the compound represented by formula (10) is the compound represented by formula (E-4) below. A preferred example of the compound represented by formula (11) is the compound represented by formula (E-5) below. A preferred example of the compound represented by formula (12) is the compound represented by formula (E-7) below. A preferred example of the compound represented by formula (13) is the compound represented by formula (E-6) below. A preferred example of the compound represented by formula (14) is the compound represented by formula (E-8) below. A preferred example of the compound represented by formula (15) is the compound represented by formula (E-2) and the compound represented by formula (E-3) below. A preferred example of the compound represented by formula (16) is the compound represented by formula (E-1) below. Hereinafter, the compounds represented by formulas (E-1) to (E-8) below may be referred to as electron transport material (E-1) to electron transport material (E-8), respectively. [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0068] The content of electron transport material in the photosensitive layer is preferably 5 parts by mass or more and 150 parts by mass or less, more preferably 10 parts by mass or more and 100 parts by mass or less, and even more preferably 30 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of binder resin. The photosensitive layer may contain only one type of electron transport material, or it may contain two or more types of electron transport materials.

[0069] [Hole transport material] The hole 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), and the compound represented by formula (24). It is believed that by including the above hole transport material in the photosensitive layer, the compatibility between the polyester resin and the electron transport material is increased, the homogeneity inside the photosensitive layer is enhanced, and the effects of the present invention can be obtained to a greater extent. [ka] [ka] [ka] [ka] [ka] (In formula (20), R 11 , R 12 , R 13 , and R 14 Each independently represents an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, and each independently represents an integer between 0 and 5, in formula (21), R 21 , R 22 , and R 23 Each of these independently represents an alkyl group having 1 to 6 carbon atoms, and R 24 , R 25 , and R 26each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, b1, b2, and b3 each independently represent 0 or 1, and in formula (22), R 31 , R 32 , and R 33 each independently represents an alkyl group having 1 to 6 carbon atoms, R 34 represents an alkyl group having 1 to 6 carbon atoms or a hydrogen atom, d1, d2, and d3 each independently represent an integer of 0 or more and 5 or less, and in formula (23), R 41 , R 42 , R 43 , R 44 , R 45 , and R 46 each independently represents an alkyl group having 1 to 6 carbon atoms or a phenyl group, R 47 and R 48 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group, e1, e2, e3, and e4 each independently represent an integer of 0 or more and 5 or less, e5 and e6 each independently represent an integer of 0 or more and 4 or less, e7 and e8 each independently represent 0 or 1, and in formula (24), R 50 and R 51 each independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group, R 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 optionally substituted with an alkyl group having 1 to 6 carbon atoms, f1 and f2 each independently represent an integer of 0 or more and 2 or less, and f3 and f4 each independently represent an integer of 0 or more and 5 or less.)

[0070] In formula (20), when a1 represents an integer of 2 or more and 5 or less, a plurality of R 11 may represent the same group as each other or different groups. When a2 represents an integer of 2 or more and 5 or less, a plurality of R 12These may represent the same base or different bases. When a3 represents an integer between 2 and 5, multiple R 13 These may represent the same base or different bases. When a4 represents an integer between 2 and 5, multiple R 14 R may represent the same group or different groups. In equation (20), 11 , R 12 , R 13 , and R 14 Each of these preferably independently represents an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group or an ethyl group. Each of a1, a2, a3, and a4 preferably independently represents an integer between 1 and 3, and more preferably 1.

[0071] 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 The bonding position on the phenyl group is preferably the meta position relative to the bonding position of the phenyl group to the triphenylamine structure. 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.

[0072] In equation (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.

[0073] In equation (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.

[0074] In equation (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 R53 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 When each represents an alkyl group having 1 to 6 carbon atoms, it is preferable that each represents an alkyl group having 1 to 3 carbon atoms, and more preferably that each represents a methyl group. 52 and R 53 When each represents a phenyl group which may be substituted with an alkyl group having 1 to 6 carbon atoms, it is preferable to represent a phenyl group or a phenyl group substituted with an alkyl group having 1 to 3 carbon atoms. A methylphenyl group is preferred as the phenyl group substituted with an alkyl group having 1 to 3 carbon atoms, and a 4-methylphenyl group is more preferred. 54 ~R 58 When each represents an alkyl group having 1 to 6 carbon atoms, it is preferable that each represents an alkyl group having 1 to 4 carbon atoms, and it is preferable that each represents a methyl group, an ethyl group, or an n-butyl group. 54 ~R 58 When each represents an alkoxy group having 1 to 6 carbon atoms, it is preferable that each represents an alkoxy group having 1 to 3 carbon atoms, and more preferably that each represents an ethoxy group.

[0075] A suitable example of the compound represented by formula (20) is the compound represented by formula (H-11) below. Suitable examples of the compound represented by formula (21) are the compound represented by formula (H-7) below and the compound represented by formula (H-8) below. A suitable example of the compound represented by formula (22) is the compound represented by formula (H-6) below. Suitable examples of the compound represented by formula (23) are the compound represented by formula (H-9) below and the compound represented by formula (H-10) below. Suitable examples of the compound represented by formula (24) are the compound represented by formula (H-1), formula (H-2), formula (H-3), formula (H-4), and formula (H-5) below. Hereinafter, the compounds represented by formulas (H-1) to (H-11) may be referred to as hole transporter (H-1) to hole transporter (H-11), respectively. [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0076] The content of hole transport material in the photosensitive 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 90 parts by mass or less, per 100 parts by mass of binder resin.

[0077] The photosensitive layer may contain only one type of hole transporter, or it may contain two or more types of hole transporters. Furthermore, the photosensitive layer may further contain hole transporters other than the compounds represented by formulas (20), (21), (22), (23), or (24) (hereinafter sometimes referred to as other hole transporters). Examples of other hole transporters include 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-oxadi Examples include azoles, 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.

[0078] [Additives] The photosensitive layer may contain additives as needed. Examples of additives include ultraviolet absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, bulking agents, thickening agents, waxes, donors, surfactants, plasticizers, sensitizers, and leveling agents. In particular, the photosensitive layer preferably contains a compound represented by the following formula (T-1) as an additive. [ka]

[0079] (Vickers hardness) The Vickers hardness of the photosensitive layer is preferably 18.0 HV or higher, and more preferably 19.0 HV or higher. When the Vickers hardness of the photosensitive layer is 19.0 HV or higher, the uniformity of the photoreceptor film is improved, and the effect of smoothing out pressure unevenness is greatly enhanced. There is no particular upper limit to the Vickers hardness of the photosensitive layer, but for example, the Vickers hardness of the photosensitive layer is 25.0 HV or lower. If the Vickers hardness of the photosensitive layer is too high, it may actually increase pressure unevenness. The Vickers hardness of the photosensitive layer is measured by a method conforming to JIS (Japanese Industrial Standards) Z2244. The Vickers hardness of the photosensitive layer can be adjusted, for example, by changing the type of binder resin, hole transport material, and electron transport material.

[0080] [Electrophotographic device] The electrophotographic apparatus according to the present invention comprises an electrophotographic photoreceptor, a charging means, an exposure means, a developing means, and a transfer means as described above. The charging means charges the surface of the electrophotographic photoreceptor. The exposure means irradiates light onto the charged surface of the photoreceptor to form an electrostatic latent image on the surface of the photoreceptor. The developing means contains toner and develops the electrostatic latent image formed on the surface of the photoreceptor with the toner to form a toner image on the surface of the photoreceptor.

[0081] We will explain using the tandem-type color electrophotographic apparatus shown in Figure 3 as an example. The electrophotographic apparatus 100 shown in Figure 3 comprises image forming units 50a, 50b, 50c, and 50d, a transfer belt 60, and a fixing device 61. Hereafter, unless otherwise necessary, each of the image forming units 50a, 50b, 50c, and 50d will be referred to as image forming unit 50.

[0082] The image forming unit 50 comprises an image carrier 40, a charging device 41 as a charging means, an exposure device 34 for irradiating exposure light 34a as an exposure means, a developing device 33 as a developing means, and a transfer device 45 as a transfer means. The image carrier 40 is a photosensitive material. The electrophotographic apparatus 100 is also configured to accommodate a recording medium P in its lower part. The image carrier 40 is located in the center of the image forming unit 50. The image carrier 40 is rotatable in the direction of the arrow (clockwise in Figure 3). Around the image carrier 40, in the order listed from the upstream side in the rotational direction of the image carrier 40, are the charging device 41, the exposure device 34, the developing device 33, and the transfer device 45.

[0083] Each of the image forming units 50a to 50d sequentially superimposes toner images of multiple colors (for example, four colors: black, cyan, magenta, and yellow) onto the recording medium P on the transfer belt 60. The charging device 41 charges the surface (e.g., the peripheral surface) of the image carrier 40 with positive polarity. The exposure device 34 irradiates the surface of the charged image carrier 40 with exposure light. That is, the exposure device 34 exposes the surface of the charged image carrier 40. As a result, an electrostatic latent image is formed on the surface of the image carrier 40. The electrostatic latent image is formed based on the image data input to the electrophotographic device 100.

[0084] The developing device 33 has toner and supplies toner to the surface of the image carrier 40, developing the electrostatic latent image as a toner image. The developing device 33 has a developing roller 30, a layering blade 31, and a toner supply roller 32. The toner supply roller 32 supplies toner to the developing roller 30. The layering blade 31 contacts the developing roller 30 to regulate the amount of toner coated by the toner supply roller 32 and to impart charge. The developing roller 30 (for example, the surface of the developing roller 30, more specifically the circumferential surface of the developing roller 30) is in contact with the surface of the image carrier 40. That is, the electrophotographic apparatus 100 employs a contact developing method. When the developer is a one-component developer, the developing device 33 supplies toner, which is a one-component developer, to the electrostatic latent image formed on the image carrier 40. When the developer is a two-component developer, the developing device 33 supplies toner from the toner and carrier contained in the two-component developer to the electrostatic latent image formed on the image carrier 40. In this way, the image carrier 40 carries the toner image.

[0085] The transfer belt 60 transports the recording medium P between the image carrier 40 and the transfer device 45. The transfer belt 60 is an endless belt. The transfer belt 60 is rotatable in the direction of the arrow (counterclockwise in Figure 3). The transfer device 45 transfers the toner image developed by the developing device 33 from the surface of the image carrier 40 to the transfer target. The transfer target is the recording medium P. When the toner image is transferred, the image carrier 40 is in contact with the recording medium P. That is, the electrophotographic apparatus 100 employs a direct transfer method. The transfer device 45 is, for example, a transfer roller. The recording medium P onto which the toner image has been transferred by the transfer device 45 is transported to the fixing device 61 by the transfer belt 60.

[0086] The fixing device 61 is, for example, a heating roller and / or a pressure roller. The unfixed toner image transferred by the transfer device 45 is heated and / or pressurized by the fixing device 61. The heating and / or pressurization of the toner image fixes the toner image to the recording medium P. As a result, an image is formed on the recording medium P.

[0087] The above describes an example of an electrophotographic apparatus, but the electrophotographic apparatus is not limited to the electrophotographic apparatus 100 already described. Although the electrophotographic apparatus 100 described above was a color electrophotographic apparatus, the electrophotographic apparatus may also be a monochrome electrophotographic apparatus. In this case, the electrophotographic apparatus may be equipped with, for example, only one image forming unit.

[0088] As shown in detail in Figure 4, the charging device 41 includes a corona charger as a corona charging member that charges without contact with the photoreceptor 40. The corona charging member has a charging control means 41b for controlling the charging potential and a discharge electrode 41a. A metal wire, preferably having a diameter of 10 to 500 μm, and more preferably 50 to 200 μm, is used as the discharge electrode 41a of the corona charging member. As the material of the metal wire, tungsten coated with a precious metal such as gold, stainless steel, etc., can be used as needed. In addition, a needle-shaped discharge electrode may be used as the discharge electrode 41a.

[0089] When a metal wire or needle-shaped electrode is used as the discharge electrode 41a, a charge control means 41b, such as a voltage-applied grid line, is provided between the discharge electrode 41a and the image carrier 40, as in a scorotron charger, allowing the charge potential of the image carrier 40 to be set to a desired level. As the charge control means 41b, instead of a grid line, a thin metal plate such as stainless steel (SUS) that has been etched and configured to allow ion flow to pass through is also preferably used. In contrast, in the case of a corotron charger, the charge potential is controlled by the amount of current, but when pursuing high image quality, control tends to be difficult. Therefore, it is preferable that the corona charger be a scorotron charger equipped with a discharge electrode and a grid.

[0090] Furthermore, although the electrophotographic apparatus 100 described above employs a tandem system, the electrophotographic apparatus may employ, for example, a rotary system. Although the electrophotographic apparatus 100 described above employs a contact development system, the electrophotographic apparatus may employ a non-contact development system. Although the electrophotographic apparatus 100 described above employs a direct transfer system, the electrophotographic apparatus may employ an intermediate transfer system. When the electrophotographic apparatus employs an intermediate transfer system, the object to be transferred corresponds to an intermediate transfer belt.

[0091] Furthermore, a cleaning roller 42a for removing residual toner from the surface of the image carrier 40 after transfer, and a pre-exposure device 43 for static electricity removal from the image carrier 40 are arranged around the image carrier 40. In addition, a conductor 42b for applying voltage to the cleaning roller 42a is in contact with the cleaning roller 42a.

[0092] [Processing cartridge] Next, with reference to Figure 4, an example of a process cartridge that can be used in the present invention will be described. Each process cartridge corresponds to an image forming unit 50a to 50d. The process cartridge comprises an image carrier 40, which is a photoreceptor. In addition to the image carrier 40, the process cartridge further comprises at least one selected from the group consisting of a charging device 41, an exposure device 34, and a developing device 33. The process cartridge may further include a cleaning member (such as a cleaning roller 42a) and a static eliminator (such as a pre-exposure device 43). The process cartridge is designed to be detachably attached to the electrophotographic apparatus 100. Therefore, the process cartridge is easy to handle, and if the sensitivity characteristics of the image carrier 40 deteriorate, it can be easily and quickly replaced, including the image carrier 40. [Examples]

[0093] 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.

[0094] <Manufacturing of polyester resin> As a polyester resin, we manufactured a polyarylate resin (PAR) having structural units derived from dicarboxylic acid and structural units derived from bisphenol. [Synthesis of resin (PAR-1)] 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 placed in the reaction vessel. • The monomer compound (BP-1) (41.0 mmol) • The terminal inhibitor is 2,6-dimethylphenol (DMP) (0.625 mmol). • Sodium hydroxide (98 mmol) • Benzyltributylammonium chloride (0.384 mmol)

[0095] The air in the reaction vessel was replaced with argon gas. Water (300 mL) 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 A1. Next, dicarboxylic acid dichloride (32.0 mmol), a derivative of the monomer compound (DC-1), was dissolved in chloroform (150 mL). This yielded chloroform solution B1.

[0096] To an alkaline aqueous solution A1, chloroform solution B1 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. Next, 400 mL of deionized water was added to an 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. Next, the water-washed organic layer was filtered to obtain the filtrate. The obtained filtrate was slowly added dropwise to 1 L of methanol to obtain a precipitate. The precipitate was removed by filtration. The extracted precipitate was vacuum-dried at 70°C for 12 hours. As a result, a resin (PAR-1) with a viscosity-average molecular weight of 35,000 was obtained.

[0097] [Synthesis of resin (PAR-30)] 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 placed in the reaction vessel. • The monomer compound (BP-1) (20.5 mmol) • The monomer compound (BP-2) (20.5 mmol) • The terminal inhibitor is 2,6-dimethylphenol (DMP) (0.413 mmol). • Sodium hydroxide (98 mmol) • Benzyltributylammonium chloride (0.384 mmol)

[0098] The air in the reaction 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 A2.

[0099] Next, 32.8 mmol of dicarboxylic acid dichloride, a derivative of the monomer compound (DC-1), and 8.2 mmol of dicarboxylic acid dichloride, a derivative of the monomer compound (DC-2), were dissolved in 150 mL of chloroform. This yielded chloroform solution B2.

[0100] To an alkaline aqueous solution A2, chloroform solution B2 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. Next, 400 mL of deionized water was added to an 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. Next, the water-washed organic layer was filtered to obtain the filtrate. The obtained filtrate was slowly added dropwise to 1 L of methanol to obtain a precipitate. The precipitate was removed by filtration. The extracted precipitate was vacuum-dried at 70°C for 12 hours. As a result, a resin (PAR-30) with a viscosity-average molecular weight of 53,600 was obtained.

[0101] [Synthesis of resins (PAR-2) to (PAR-29), (PAR-31) to (PAR-44), and (PAR-101) to (PAR-107)] Except for changing the relative ratio of bisphenol to dicarboxylic acid, and the type and amount of end-stopper used, the resin (PAR-30) was synthesized using the same method as the resin (PAR-30), and resins with viscosity-average molecular weights shown in Tables 1, 2, and 3 were obtained. Note that the viscosity-average molecular weight of the resin (PAR) increases as the amount of end-stopper used decreases.

[0102] [Table 1]

[0103] [Table 2]

[0104] [Table 3]

[0105] The values ​​for bisphenols in Tables 1, 2, and 3 represent the ratio of the amount of each bisphenol to the total amount of two bisphenols in resins (PAR-1) to (PAR-44) and resins (PAR-101) to (PAR-107). The values ​​for dicarboxylic acids represent the ratio of the amount of each dicarboxylic acid to the total amount of two dicarboxylic acids. PFH refers to 1H,1H-perfluoro-1-heptanol. Molecular weight is the viscosity-average molecular weight.

[0106] <Manufacturing of electrophotographic photoconductors> [Manufacturing of Photoreceptor 1] The following materials were prepared. • 2.0 parts by mass of Y-type crystals of titanylphthalocyanine represented by formula (CGM-1), which is a charge-generating material. • Hole transport material (H-11) 70.0 parts by mass ·Electron transport material (E-4) 40.0 parts by mass • Additive (compound represented by formula (T-1)) 14.0 parts by mass • Binder resin (PAR-1) 100.0 parts by mass • 500.0 parts by mass of tetrahydrofuran, which is a solvent. The above materials were mixed for 20 minutes using a rod-shaped sonic oscillator to obtain a dispersion. The dispersion was filtered using a 5 μm mesh filter to obtain a coating solution for the photosensitive layer. The coating solution for the photosensitive layer was applied to a conductive support (aluminum drum-shaped support) by dip coating and dried with hot air at 120°C for 50 minutes. In this way, a photosensitive layer (film thickness 30 μm) was formed on the conductive support to obtain photoreceptor 1.

[0107] (Analysis of the resin components of photoreceptor 1) For the polymer component recovered from the obtained photoreceptor, by 1 1H-nuclear magnetic resonance analysis in deuterated chloroform, 1 an 1H-NMR spectrum was obtained. The obtained 1 1H-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, and 7.04 ± 0.02 ppm. From this, it was specified that the photoreceptor contains the structural unit represented by formula (1) and the structural unit represented by formula (2). Also, the ratio of the amount of substance of the structural unit represented by formula (1) to the structural unit represented by formula (2) was 1:1 based on the integral ratio of the above-mentioned peaks, as shown in Table 1.

[0108] [Manufacture of photoreceptors 2 to 90, 101 to 107] Photoreceptors 2 to 90 and 101 to 107 were manufactured in the same manner as the manufacture of photoreceptor 1, except that the types of the charge generating substance, additive, hole transporting substance, electron transporting substance, and binder resin were changed. Tables 4, 5, and 6 show the types of the charge generating substance, additive, hole transporting substance, electron transporting substance, and binder resin used. The mass of each material used was the same as that of photoreceptor 1. Photoreceptor production examples are shown in Tables 4, 5, and 6. In the tables, CGM indicates the charge generating substance, HTM indicates the hole transporting substance, and ETM indicates the electron transporting substance, and each shows a compound number. Also, the ratio values described for the resin are the mass ratio values of resin 1 and resin 2 in the entire binder resin.

[0109] (Analysis of the resin components of photoreceptor 16) For the polymer component recovered from the obtained photoreceptor, by 1H-nuclear magnetic resonance analysis in deuterated chloroform, 1 an 1H-NMR spectrum was obtained. The obtained 1The 1H-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. This identified that the photoreceptor contained structural units represented by formula (1), formula (2), formula (3), and formula (4). Furthermore, the proportions of the amounts of substance of the structural units represented by formula (1), formula (2), formula (3), and formula (4) were as shown in Table 1, based on the integral ratio of the above peaks.

[0110] <Measurement of Vickers hardness> The Vickers hardness of the photosensitive layer was measured for the photosensitive materials shown in Tables 4, 5, and 6. Specifically, the Vickers hardness of the photosensitive layer was measured according to the method compliant with JIS (Japanese Industrial Standards) Z2244. A hardness tester ("Micro Vickers Hardness Tester DMH-1" manufactured by Matsuzawa Co., Ltd. (formerly Matsuzawa Seiki Co., Ltd.)) was used to measure the Vickers hardness. The Vickers hardness was measured under the following conditions: temperature 23°C, diamond indenter load (test force) 10 gf, time required to reach the test force 5 seconds, diamond indenter approach speed 2 mm / second, and holding time of the test force 1 second. The measured Vickers hardness is shown in Tables 4, 5, and 6.

[0111] [Table 4]

[0112] [Table 5]

[0113] [Table 6]

[0114] [evaluation] A Brother HL-5200 monochrome laser printer was modified to serve as the electrophotographic device. A high-voltage power control system (product name: Model 615-3, manufactured by Trek) was used as the power supply to provide power for the corona charger from outside the printer. The electrophotographic photoreceptor in the drum unit of the printer's cartridge was removed and replaced with photoreceptor 1. This image forming apparatus was left in an environment of 10°C and 15% RH for more than 24 hours, and the following evaluations were performed.

[0115] <Evaluation of the charge stability and sensitivity stability of photoreceptors> First, using the evaluation machine, a completely blank image was printed onto three recording media (A4 size paper). The surface potential of the photoreceptor was measured at the development position during printing on each sheet. Since no exposure occurs when printing a blank image, the measured surface potential corresponds to the charge potential. The surface potential was measured once for each sheet printed, for a total of three measurements. The average of the three measured surface potentials was used as the charge potential V before the printing test. d0 (Unit: +V)

[0116] Similarly, three completely black images were printed, and the surface potential was measured at the development position. Since exposure occurs when printing a completely black image, the measured surface potential corresponds to the post-exposure potential. The surface potential was measured once per sheet of paper, for a total of three measurements. The average of the three measured surface potentials was used as the post-exposure potential (V) before the printing test. L0 (Unit: +V)

[0117] Next, a print test was conducted. The print test involved printing a print pattern image with a 3% print density onto 30,000 sheets of recording media (A4 size paper) using an evaluation machine. Immediately after the print test, a completely blank image was printed. The surface potential of the photoreceptor was measured at the development position during printing on each sheet of paper. The surface potential was measured once per sheet of paper, for a total of three measurements. The average of the three measured surface potentials was used as the charged potential V after the print test. d1 (Unit: +V)

[0118] Also, the initial charging potential is charging potential V d0 Three completely black images were printed with the charging potential adjusted to achieve the desired result. Similarly, three more completely black images were printed, and the surface potential was measured at the development position. The surface potential was measured once per sheet of paper, for a total of three measurements. The average of the three measured surface potentials was used as the post-exposure potential V after the printing test. L1 (Unit: +V)

[0119] Charge potential V before printing test d0 From the electrostatic potential V after the printing test d1 The value obtained by subtracting (V d0 -V d1 ) is the amount of charge potential decrease ΔV d (Unit: V) Charge potential drop ΔV d This is shown in Table 7. Charge potential decrease ΔV d A smaller value (in V) indicates better charging stability of the photoreceptor. Note that the charge potential drop ΔV d Photoreceptors with a voltage (in V) of 20V or higher were evaluated as having poor charge stability. Also, the post-exposure potential V before the printing test. L0 From the exposure potential V after the printing test L1 The value obtained by subtracting (V L1 -V L0 ) is the post-exposure potential change ΔV L (Unit: V) Potential change after exposure ΔV L This is shown in Table 7. Post-exposure potential change ΔV L A smaller value (in V) indicates better sensitivity stability of the photoreceptor. Note that ΔV represents the potential change after exposure. L Photoreceptors with a voltage (in V) of 30V or higher were evaluated as having poor sensitivity stability. [Table 7]

[0120] The disclosure of embodiments of the present invention includes the following configurations. (Composition 1) An electrophotographic apparatus comprising an electrophotographic photoreceptor and a corona charger for positively charging the electrophotographic photoreceptor, The electrophotographic photoreceptor has a single-layer photosensitive layer, The photosensitive layer contains a charge generation substance, a hole transport substance, an electron transport substance, and a binder resin, The binder resin includes a polyester resin having a structural unit represented by the following formula (a) and a structural unit represented by the following formula (1), An electrophotographic apparatus, characterized in that 70 mol% or more of the structural units represented by the following formula (a) contained in the polyester resin are structural units represented by the following formula (2).

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0121] 1: Single-layer photoreceptor 2:Support 3: Photosensitive layer 4: Lower layer 30: Developing Roller 31: Stratified blade 32: Toner supply roller 33: Developing equipment 34: Exposure equipment 41: Charging device 41a:Discharge electrode 41b: Charge control means 42a: Cleaning roller 42b: Conductor 43: Pre-exposure device 45: Transfer device 50: Image forming unit 60: Transfer belt 61: Fixing device 100: Electrophotographic device

Claims

1. An electrophotographic apparatus comprising an electrophotographic photoreceptor and a corona charger for positively charging the electrophotographic photoreceptor, The electrophotographic photoreceptor has a single-layer photosensitive layer, The photosensitive layer contains a charge generating material, a hole transporting material, an electron transporting material, and a binder resin. The binder resin comprises a polyester resin having structural units represented by the following formula (a) and structural units represented by the following formula (1). An electrophotographic apparatus characterized in that 70 mol% or more of the structural units represented by the following formula (a) contained in the polyester resin are structural units represented by the following formula (2). 【Chemistry 1】 (In formula (a), X represents a divalent organic group that does not have an ester bond.) 【Chemistry 2】 【Transformation 3】

2. The electrophotographic apparatus according to claim 1, wherein the polyester resin further comprises a structural unit represented by the following formula (3). 【Chemistry 4】

3. The electrophotographic apparatus according to claim 1, wherein the polyester resin further comprises a structural unit represented by formula (a) as a structural unit represented by the following formula (4). 【Transformation 5】

4. The electrophotographic apparatus according to claim 2, wherein M1 is the ratio of the amount of substance of the structural units represented by formula (1) to the total amount of substance of the structural units constituting the polyester resin, and M3 is the ratio of the amount of substance of the structural units shown by formula (3), and M1 and M3 satisfy the relationship expressed as 0 < M1 / ​​(M1 + M3) ≤ 0.

5.

5. The electrophotographic apparatus according to claim 1, wherein the proportion of the polyester resin to the total mass of the binder resin is 50% by mass or more.

6. The electrophotographic apparatus according to claim 1, wherein the electron transport material contains at least one compound selected from the group consisting of a compound represented by the following formula (10), a compound represented by the following formula (11), a compound represented by the following formula (12), a compound represented by the following formula (13), a compound represented by the following formula (14), a compound represented by the following formula (15), and a compound represented by the following formula (16). 【Transformation 6】 【Transformation 7】 【Transformation 8】 【Chemistry 9】 【Chemistry 10】 【Chemistry 11】 【Chemistry 12】 (Q in formula (10) １ and Q ２ , Q in formula (11) １１ , Q １２ , and Q １３ , Q in formula (12) ２１ , Q ２２ , Q ２３ , and Q ２４ , Q in formula (13) ３１ and Q ３２ , Q in formula (14) ４１ , Q ４２ , Q ４３ , and Q ４４ , Q in formula (15) ５１ , Q ５２ , Q ５３ , Q ５４ , Q ５５ , and Q ５６ , and Q in formula (16) ６１ and Q ６２ each independently represents an aryl group having 6 to 14 carbon atoms which may be substituted with at least one substituent selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms and a halogen atom; Y in formula (15) １ and Y ２ each independently represents an oxygen atom or a sulfur atom.)

7. The electrophotographic apparatus according to claim 6, wherein the electron transport material contains at least one compound selected from the group consisting of a compound represented by the following formula (E-1), a compound represented by the following formula (E-2), a compound represented by the following formula (E-3), a compound represented by the following formula (E-4), a compound represented by the following formula (E-5), a compound represented by the following formula (E-6), a compound represented by the following formula (E-7), and a compound represented by the following formula (E-8). 【Chemistry 13】 【Chemistry 14】 【Chemistry 15】 【Chemistry 16】 【Chemistry 17】 [Chemistry 18] 【Chemistry 19】 【Chemistry 20】

8. The electrophotographic apparatus according to claim 1, wherein the hole transport material contains at least one compound selected from the group consisting of a compound represented by the following formula (20), a compound represented by the following formula (21), a compound represented by the following formula (22), a compound represented by the following formula (23), and a compound represented by the following formula (24). 【Chemistry 21】 【Chemistry 22】 【Chemistry 23】 【Chemistry 24】 【Chemistry 25】 (In formula (20), R １１ , R １２ , R １３ , and R １４ Each independently represents an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms, a １ a ２ a ３ , and a ４ Each of these independently represents an integer between 0 and 5, and in equation (21), R ２１ , R ２２ , and R ２３ Each of these independently represents an alkyl group having 1 to 6 carbon atoms, and R ２４ , R ２５ , and R ２６ Each of these independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and b １ , b ２ , and b ３ Each independently represents either 0 or 1, and in equation (22), R ３１ , R ３２ , and R ３３ Each of these independently represents an alkyl group having 1 to 6 carbon atoms, and R ３４ represents an alkyl group or hydrogen atom having 1 to 6 carbon atoms, d １ d ２ , and d ３ Each of these independently represents an integer between 0 and 5, and in equation (23), R ４１ , R ４２ , R ４３ , R ４４ , R ４５ , and R ４６ Each independently represents an alkyl group having 1 to 6 carbon atoms, or a phenyl group, R ４７ and R ４８ Each of these independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group, and e １ , e ２ , e ３ , and e ４ Each of these independently represents an integer between 0 and 5, and e ５ and e ６ Each of these independently represents an integer between 0 and 4, and e ７ and e ８ Each independently represents either 0 or 1, and in equation (24), R ５０ and R ５１ Each independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a phenyl group, R 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, and f １ and f ２ Each of these independently represents an integer between 0 and 2, and f ３ and f ４ Each of these independently represents an integer between 0 and 5 (inclusive).

9. The electrophotographic apparatus according to claim 8, wherein the hole transport material contains at least one compound selected from the group consisting of a compound represented by the following formula (H-1), a compound represented by the following formula (H-2), a compound represented by the following formula (H-3), a compound represented by the following formula (H-4), a compound represented by the following formula (H-5), a compound represented by the following formula (H-6), a compound represented by the following formula (H-7), a compound represented by the following formula (H-8), a compound represented by the following formula (H-9), a compound represented by the following formula (H-10), and a compound represented by the following formula (H-11). 【Chemistry 26】 【Chemistry 27】 【Chemistry 28】 【Chemistry 29】 【Transformation 30】 【Chemistry 31】 【Chemistry 32】 【Transformation 33】 【Transformation 34】 【Chemistry 35】 【Transformation 36】

10. The electrophotographic apparatus according to any one of claims 1 to 9, wherein the charge generating material comprises titanylphthalocyanine.

11. The electrophotographic apparatus according to claim 1, wherein the photosensitive layer contains a compound represented by the following formula (T-1) as an additive. 【Chemistry 37】

12. The electrophotographic apparatus according to claim 1, wherein the corona charger is a scorotron charger comprising a discharge electrode and a grid.

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