Electrophotographic photoreceptor, process cartridge, and electrophotographic apparatus

Abstract

To provide an electrophotographic photoreceptor that can achieve a high level of both suppression of potential fluctuations and suppression of ghosting phenomena even during long-term repeated use. [Solution] An electrophotographic photoreceptor having a support, an undercoat layer formed on the support, and a charge generating layer formed on the undercoat layer, wherein the undercoat layer contains a polymer of a compound represented by formula (1), a compound represented by formula (2), a crosslinking agent having a group that can bond to a hydroxyl group or a carboxyl group, and metal oxide particles.

Description

[Technical Field]

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

[0002] In recent years, there has been a need to improve the stability of sensitivity of electrophotographic photoreceptors (hereinafter also simply referred to as photoreceptors) used in electrophotography, especially during long-term use. Organic electrophotographic photoreceptors are often used as such, and organic electrophotographic photoreceptors have a charge generation layer on a support.

[0003] In a photoreceptor having a charge generation layer on a support, an undercoat layer may be provided between the charge generation layer and the support to improve electron transport. One of the causes of decreased sensitivity during long-term use is the accumulation of charge in the undercoat layer.

[0004] Patent Document 1 describes a method for improving the electron transport performance of the undercoat layer by incorporating an electron transport material into the undercoat layer. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-183166 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, when using the technology described in Patent Document 1, the potential difference between the exposed and unexposed areas when outputting an image sometimes affected the next image output, resulting in a noticeable ghosting phenomenon that manifested as a difference in image density. The present invention has been made in view of the above problems. That is, an object of the present invention is to provide an electrophotographic photoreceptor capable of achieving high-level compatibility between suppression of potential fluctuations and suppression of ghost phenomena even in long-term repeated use.

Means for Solving the Problems

[0007] An electrophotographic photoreceptor according to an aspect of the present invention is an electrophotographic photoreceptor having a support, an undercoat layer formed on the support, and a charge generation layer formed on the undercoat layer, wherein the undercoat layer contains a polymer of a compound represented by the following formula (1), a compound represented by the following formula (2), and a crosslinking agent having a group capable of bonding to a hydroxy group or a carboxy group, and metal oxide particles.

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0008] According to the present invention, it is possible to provide an electrophotographic photoreceptor that can achieve a high level of both suppression of potential fluctuations and suppression of ghosting phenomena even during long-term repeated use. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of a schematic configuration of an electrophotographic apparatus having a process cartridge equipped with an electrophotographic photoreceptor. [Figure 2] This figure shows an example of the layer structure of an electrophotographic photoreceptor. [Figure 3] This figure shows the output image for ghost evaluation. [Figure 4] This figure shows the halftone image included in the output image for ghost evaluation. [Modes for carrying out the invention]

[0010] The electrophotographic photoreceptor according to the present invention is an electrophotographic photoreceptor having a support, an undercoat layer formed on the support, and a charge generating layer formed on the undercoat layer, wherein the undercoat layer contains a specific polymer and metal oxide particles. The specific polymer is a polymer of a compound represented by the following formula (1), a compound represented by the following formula (2), and a crosslinking agent having a group that can bond to a hydroxyl group or a carboxyl group. [ka] [ka] (In equations (1) and (2), R 1 and R 2 These show different groups from each other, and multiple R 1 They may be the same or different from each other, R 1 and R 2 Each of these is independently a substituted or unsubstituted alkyl group having 2 to 6 carbon atoms, a group derived by replacing at least one CH2 atom in the main chain of a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms with an oxygen atom, a group derived by replacing at least one CH2 atom in the main chain of a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms with NRa, a group derived by replacing at least one C2H4 atom in the main chain of a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms with COO, or a substituted aryl group. Ra represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The substituents of the substituted alkyl group, the group derived by replacing at least one CH2 in the main chain of the substituted alkyl group with an oxygen atom, the group derived by replacing at least one CH2 in the main chain of the substituted alkyl group with NRa, and the group derived by replacing at least one C2H4 in the main chain of the substituted alkyl group with COO are groups selected from the group consisting of alkyl groups having 1 to 5 carbon atoms, benzyl groups, alkoxycarbonyl groups, phenyl groups, hydroxyphenyl groups, hydroxyl groups, thiol groups, amino groups, and carboxyl groups. The substituents of the substituted aryl group are groups selected from the group consisting of halogen atoms, cyano groups, nitro groups, methyl groups, ethyl groups, isopropyl groups, n-propyl groups, n-butyl groups, acyl groups, alkoxy groups, alkoxycarbonyl groups, hydroxyl groups, thiol groups, amino groups, and carboxyl groups. R 1 and R 2 Each contains at least one hydroxyl group or carboxyl group. In equations (1) and (2), X is independently selected from the structure shown in equation (X1), the structure shown in equation (X2), and the structure shown in equation (X3). [ka] [ka] [ka] In equations (X1), (X2), and (X3), R 11 ~R 18 , R 21 ~R 24 , R 31 , and R 32 Each of these independently represents a hydrogen atom, a halogen atom, a cyano group, or a nitro group.

[0011] It is believed that by including polymers having the structures shown in formula (1) and formula (2) as electron-transporting materials in the undercoat layer, the penetration of holes generated in the charge generation layer into the undercoat layer is inhibited, thereby improving electron transport. Therefore, it is thought that potential fluctuations during long-term repeated use of electrophotographic photoreceptors can be effectively suppressed.

[0012] In the electrophotographic process, when an electric field opposite to the development bias (such as in the transfer process) is applied to the photoreceptor, holes that would normally remain there are released into the support. However, if the undercoat layer contains a polymer with the structure described above, it is thought that the holes are less likely to release into the support. Therefore, it is expected that holes will be trapped between layers, making ghosting more likely.

[0013] As a result of their extensive research, the inventors have found that a base layer containing polymers having the structures shown in formula (1) and formula (2), further containing metal oxide particles, can suppress both potential fluctuations and ghosting phenomena even during long-term repeated use. This is thought to be because, in a base layer containing polymers having the structures shown in formula (1) and formula (2), the inclusion of metal oxide particles in the base layer creates sites where holes can move, making it easier for holes to escape to the support side. The configuration of the electrophotographic photoreceptor according to the present invention will be described in more detail below.

[0014] [Electrophotographic photoconductor] Figure 2 shows an example of the layer structure of an electrophotographic photoreceptor. In Figure 2, a support 101, a conductive layer 102 on the support 101, an undercoat layer 103 on the conductive layer 102, a charge generation layer 104 on the undercoat layer 103, and a charge transport layer 105 on the charge generation layer 104 are formed. That is, the electrophotographic photoreceptor shown in Figure 2 has a support 101, a conductive layer 102, an undercoat layer 103, a charge generation layer 104, and a charge transport layer 105 in this order. Note that the layer structure of the electrophotographic photoreceptor may also be such that the conductive layer 102 is not present in the example shown in Figure 2, and the undercoat layer is directly provided on the support 101. Cylindrical electrophotographic photoreceptors are widely used, but they can also be in other shapes such as belts or sheets.

[0015] <Support> The support is preferably made of a conductive material (conductive support). For example, a support made of metal or alloy such as aluminum, nickel, copper, gold, or iron can be used. Alternatively, a conductive support may be made by forming a thin film of a conductive material such as a metal or metal oxide on an insulating support. Examples include a support made by forming a thin film of a metal such as aluminum, silver, or gold on an insulating support such as polyester resin, polycarbonate resin, polyimide resin, or glass, or a support made by forming a thin film of a conductive material such as indium oxide or tin oxide. The surface of the support may be subjected to electrochemical treatments such as anodizing, wet honing, blasting, or cutting to improve electrical properties and suppress interference fringes.

[0016] <Underlayer> The thickness of the undercoat layer is preferably 0.2 μm or more and 5.0 μm or less, and more preferably 0.5 μm or more and 3.0 μm or less.

[0017] The undercoat can be formed by forming a coating film of an undercoat coating solution containing a compound represented by formula (1), a compound represented by formula (2), a crosslinking agent having a group that can bond to a hydroxyl group or a carboxyl group, and metal oxide particles, and then drying the coating film. When polymerizing polymerizable monomers contained in the undercoat coating solution during the drying of the coating film, the polymerization reaction (curing reaction) is accelerated by applying heat or light energy. Solvents used in the undercoat coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon solvents.

[0018] (electron transport material) In the present invention, the compound represented by formula (1) and the compound represented by formula (2), which are electron transport materials, are used to form the undercoat layer. Derivatives of electron transport materials can be purchased from Tokyo Chemical Industry Co., Ltd., Sigma-Aldrich Japan, and Johnson Matthey Japan LLC. Derivatives having the structure of formula (X1) can be synthesized by the reaction of perylenetetracarboxylic dianhydride, which can be purchased from Tokyo Chemical Industry Co., Ltd. or Sigma-Aldrich Japan, with a monoamine derivative. Derivatives having the structure of formula (X2) can be synthesized by the reaction of naphthalenetetracarboxylic dianhydride, which can be purchased from Tokyo Chemical Industry Co., Ltd. or Johnson Matthey Japan LLC, with a monoamine derivative. Derivatives having the structure of formula (X3) can be synthesized by the reaction of benzenetetracarboxylic dianhydride, which can be purchased from Tokyo Chemical Industry Co., Ltd. or Sigma-Aldrich Japan, with a monoamine derivative.

[0019] As electron transport materials, compounds represented by formula (1) and formula (2) are preferred, where X in formulas (1) and (2) has the structure represented by formula (X1).

[0020] Furthermore, from the viewpoint of film-forming properties and electrical properties, the content of structural units derived from electron transport materials is preferably 40% to 80% by mass of the entire undercoat layer, and more preferably 50% to 70% by mass.

[0021] Furthermore, from the viewpoint of electrical properties, the mass-based content ratio (formula (1) / formula (2)) of structural units derived from the compound represented by formula (1) to structural units derived from the compound represented by formula (2) in the undercoat layer is preferably 0.13 or more and 4.0 or less. More preferably, the above content ratio is 0.25 or more and 2.0 or less.

[0022] (metal oxide particles) The average primary particle size of the metal oxide particles, measured by observing the cross-section of the undercoat layer using a scanning electron microscope (SEM), is preferably between 20 nm and 150 nm. When the average primary particle size of the metal oxide particles is between 20 nm and 150 nm, ghost performance can be effectively improved without hindering potential fluctuation characteristics.

[0023] The metal oxide particles preferably contain a metal oxide selected from titanium oxide, zinc oxide, strontium titanate, and barium titanate. When metal oxide particles containing these metal oxides are used, the potential fluctuation suppression effect tends to be improved.

[0024] The metal oxide particles are preferably surface-treated, and more preferably treated with an organosilane compound. When treated with an organosilane compound, their dispersibility in the coating film is easily improved, thus improving the potential fluctuation suppression effect.

[0025] In the undercoat layer, the mass ratio of metal oxide particles to the polymer (metal oxide particles / polymer) is preferably 0.009 or more and 0.160 or less. When the mass ratio is 0.009 or more, the hole trapping properties are easily reduced and the ghost performance is easily improved. When the mass ratio is 0.160 or less, the performance of the electron transport material is not hindered and the potential fluctuation performance is easily maintained.

[0026] (Crosslinking agent) Any known material can be used as the crosslinking agent having a group capable of bonding to a hydroxyl group or a carboxyl group. Preferably, the crosslinking agent is an isocyanate compound having an isocyanate group or a blocked isocyanate group, or an amine compound having an N-methylol group or an alkyl etherified N-methylol group. In particular, it is preferable that the crosslinking agent is an isocyanate compound having 2 to 6 isocyanate groups or blocked isocyanate groups.

[0027] <Charge generation layer> The charge generation layer preferably contains a charge generation material and a binder resin. Examples of charge-generating materials include azo pigments, perylene pigments, anthraquinone derivatives, anthantrone derivatives, dibenzpyrenequinone derivatives, pyrantrone derivatives, quinone pigments, indigoid pigments, phthalocyanine pigments, and perinone pigments. Among these, phthalocyanine pigments are preferred. Among phthalocyanine pigments, oxytitanium phthalocyanine, chlorogallium phthalocyanine, and hydroxygallium phthalocyanine are preferred, and chlorogallium phthalocyanine and hydroxygallium phthalocyanine are more preferred. The charge-generating layer preferably contains chlorogallium phthalocyanine or hydroxygallium phthalocyanine, in which case the potential fluctuation suppression effect tends to be improved.

[0028] Examples of binder resins include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylic acid esters, methacrylic acid esters, vinylidene fluoride, and trifluoroethylene, as well as polyvinyl alcohol, polyvinyl acetal, polycarbonate, polyester, polysulfone, polyphenylene oxide, polyurethane, cellulose resin, phenolic resin, melamine resin, silicon resin, and epoxy resin. Among these, polyester, polycarbonate, and polyvinyl acetal are preferred.

[0029] In the charge generation layer, the mass-based content ratio of the charge generation material to the binder resin (charge generation material / binder resin) is preferably in the range of 10 / 1 to 1 / 10, and more preferably in the range of 5 / 1 to 1 / 5.

[0030] Solvents used in the coating solution for the charge generation layer include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon solvents. The thickness of the charge generation layer is preferably 0.05 μm or more and 5 μm or less.

[0031] <Charge transport layer> The charge transport layer preferably contains a charge transport material and a binder resin. Examples of charge transport materials include hydrazone compounds, styryl compounds, benzidine compounds, butadiene compounds, enamine compounds, triarylamine compounds, and triphenylamines. Polymers having groups derived from these compounds in their main chain or side chains are also examples.

[0032] Examples of binder resins include polyester, polycarbonate, polymethacrylate, polyarylate, polysulfone, and polystyrene. Among these, polycarbonate and polyarylate are preferred. Furthermore, the weight-average molecular weight (Mw) of these materials is preferably in the range of 10,000 to 300,000.

[0033] In the charge transport layer, the mass-based content ratio of the charge transport material to the binder resin (charge transport material / binder resin) is preferably in the range of 10 / 5 to 5 / 10, and more preferably in the range of 10 / 8 to 6 / 10.

[0034] The thickness of the charge transport layer is preferably 5 μm or more and 40 μm or less. Examples of solvents used in the coating solution for the charge transport layer include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon solvents.

[0035] <Other layers> A protective layer containing conductive particles or a charge transport material and a binder resin may be provided on the charge transport layer. The protective layer may further contain additives such as lubricants. The binder resin of the protective layer may also have conductivity or charge transport properties, in which case the protective layer does not need to contain conductive particles or charge transport materials other than the binder resin. The binder resin of the protective layer may be a thermoplastic resin or a curable resin that is cured by heat, light, radiation (such as electron beams).

[0036] [Process cartridges and electrophotographic equipment] Figure 1 shows a schematic configuration of an electrophotographic apparatus having a process cartridge equipped with an electrophotographic photoreceptor. The electrophotographic apparatus shown in Figure 1 includes an electrophotographic photoreceptor 1, a charging means 3, an exposure means (not shown), a developing means 5, and a transfer means 6.

[0037] In Figure 1, the cylindrical electrophotographic photoreceptor 1 is driven to rotate at a predetermined peripheral speed in the direction of the arrow around axis 2. The surface (circumferential surface) of the rotating electrophotographic photoreceptor 1 is charged to a predetermined positive or negative potential by a charging means 3 (e.g., a contact charger, a non-contact charger, etc.). Next, it is exposed with exposure light (image exposure light) 4 from an exposure means such as slit exposure or laser beam scanning exposure. In this way, an electrostatic latent image corresponding to the desired image is sequentially formed on the surface of the electrophotographic photoreceptor 1.

[0038] The electrostatic latent image formed on the surface of the electrophotographic photoreceptor 1 is then developed by the toner contained in the developer of the developing means 5 to form a toner image. The toner image formed and supported on the surface of the electrophotographic photoreceptor 1 is sequentially transferred to the transfer material (paper, etc.) P by the transfer bias from the transfer means (transfer roller, etc.) 6. The transfer material P is supplied from a transfer material supply means (not shown) to the space between the electrophotographic photoreceptor 1 and the transfer means 6 (contact area) in synchronization with the rotation of the electrophotographic photoreceptor 1.

[0039] After transferring the toner image, the transfer material P is separated from the surface of the electrophotographic photoreceptor 1 and introduced to the fixing means 8, where it undergoes image fixing and is printed out outside the device as an image-formed product (print, copy).

[0040] After the toner image is transferred, the surface of the electrophotographic photoreceptor 1 is cleaned by a cleaning means (such as a cleaning blade) 7 to remove any remaining developer (transferred toner). Then, it is subjected to static discharge treatment by pre-exposure light (not shown) from a pre-exposure means (not shown) and used repeatedly for image formation. Note that, as shown in Figure 1, if the charging means 3 is a contact charging means using a charging roller, pre-exposure is not necessarily required.

[0041] A process cartridge can house and integrally support an electrophotographic photoreceptor 1 and at least one means selected from the group consisting of a charging means 3, a developing means 5, and a cleaning means 7 in a container. This process cartridge may be configured to be detachable from the electrophotographic apparatus body. In Figure 1, the electrophotographic photoreceptor 1, the charging means 3, the developing means 5, and the cleaning means 7 are integrally supported and formed into a cartridge, which is a process cartridge 9 that can be detachably attached to the electrophotographic apparatus body using guide means 10 such as rails on the electrophotographic apparatus body.

[0042] The toner, cleaning blade, and developing roller in the aforementioned process cartridge are not particularly restricted and can be used as long as they are compatible with general electrophotographic processes.

[0043] Toners can be manufactured using methods such as pulverization, suspension polymerization, and emulsification and agglutination, but among these, toners manufactured by suspension polymerization and emulsification and agglutination are preferred from the viewpoint of image quality stability. [Examples]

[0044] The present invention will be described in more detail below with reference to examples. In the examples, "parts" refers to "parts by mass".

[0045] (Synthesis of electron transport material E1) To 20 parts of dimethylacetamide, 2.0 parts of perylenetetracarboxylic dianhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) and 2.2 parts of L-(+)-leucinol (manufactured by Tokyo Chemical Industry Co., Ltd.) were added under a nitrogen atmosphere. The mixture was then refluxed for 10 hours, separated by silica gel column chromatography (eluent: THF / toluene), and the fraction containing the target substance was concentrated. The concentrate was recrystallized in a THF / n-hexane mixed solution to obtain 2.0 parts of electron transport material E1.

[0046] The structure of the obtained electron transport material E1 was identified by NMR (nuclear magnetic resonance spectroscopy) under the following conditions. The structure is shown in Table 1. Measuring instrument used: BRUKER, AVANCEIII500 Solvent: Deuterated chloroform (CDCl3) Total count: 256

[0047] (Synthesis of electron transport materials E2-E5) In the example of the synthesis of electron transport material E1, electron transport materials E2 to E5 were synthesized by appropriately changing the raw materials. The structures of electron transport materials E2 to E5 are shown in Table 1.

[0048] (Manufacturing of titanium dioxide particles A1) As the substrate, anatase-type titanium dioxide with an average primary particle size of 200 nm was used. A titanium-niobium sulfate solution containing 33.7 parts titanium (in TiO2 equivalent) and 2.9 parts niobium (in Nb2O5 equivalent) was prepared. 100 parts of the substrate were dispersed in pure water to make a 1000-part suspension, which was heated to 60°C. The titanium-niobium sulfate solution and 10 mol / L sodium hydroxide were added dropwise over 3 hours until the pH of the suspension reached 2-3. After the entire amount had been added, the pH was adjusted to near neutral, and a polyacrylamide-based flocculant was added to settle the solids. The supernatant was removed, filtered, washed, and dried at 110°C to obtain an intermediate containing 0.1% by mass of organic matter derived from the flocculant (in C equivalent). This intermediate was calcined at 750°C in nitrogen for 1 hour, and then calcined at 450°C in air to produce titanium dioxide particles A1. The obtained particles, measured using the scanning electron microscope method described above, had an average particle size (average primary particle size) of 220 nm.

[0049] (Manufacturing of metal oxide particles C1) 100 parts of untreated rutile-type titanium oxide particles (average primary particle size: 50 nm, manufactured by Teika) were stirred and mixed with 400 parts methanol and 100 parts methyl ethyl ketone, and 5.0 parts of vinyltrimethoxysilane were added. Subsequently, the mixture was dispersed for 8 hours using 1.0 mm diameter glass beads in a vertical sand mill. After removing the glass beads, methanol and methyl ethyl ketone were removed by vacuum distillation, and the mixture was dried at 120°C for 3 hours to obtain rutile-type titanium oxide particles surface-treated with an organosilicon compound. These were designated as metal oxide particles C1.

[0050] (Manufacturing of metal oxide particles C2) In the method for producing metal oxide particles C1, metal oxide particles C2 were produced by performing the same treatment, except that the particle size of the untreated titanium oxide particles was changed.

[0051] (Manufacturing of metal oxide particles C3) Metal oxide particles C3 were produced in the same manner as in the method for producing metal oxide particles C1, except that vinyltrimethoxysilane was replaced with isobutyltrimethoxysilane and the particle size of the untreated titanium oxide particles was changed.

[0052] (Metal oxide particles C4) For the metal oxide particles C4, zinc oxide particles (particle size 35 nm, manufactured by Teika Co., Ltd.) were used.

[0053] (Metal oxide particles C5) As the metal oxide particles C5, strontium titanate particles (particle size 100 nm, manufactured by Sakai Chemical Co., Ltd.) were used.

[0054] (Metal oxide particles C6) Barium titanate particles (particle size 50 nm, manufactured by Sakai Chemical Co., Ltd.) were used as the metal oxide particles C6.

[0055] (Metal oxide particles C7) As the metal oxide particles C7, titanium oxide particles treated with alumina (manufactured by Teika Co., Ltd.) were used. Alumina treatment is one of the surface treatment methods using inorganic compounds, and was specifically carried out as follows: A water-soluble aluminum compound was added to the titanium oxide particles and neutralized to precipitate alumina on the surface of the titanium oxide particles. After that, filtration, washing, and drying were performed.

[0056] (Metal oxide particles C8) Untreated rutile-type titanium oxide particles (average primary particle size: 50 nm, manufactured by Teika Co., Ltd.) were used as metal oxide particles C8.

[0057] <Example 1> [Manufacturing of electrophotographic photoreceptors] (Support) An aluminum cylinder (JIS-A3003, aluminum alloy) with a length of 260.5 mm and a diameter of 30 mm was machined (JIS B0601:2014, 10-point average roughness Rzjis: 0.8 μm) and used as a support (conductive support).

[0058] (Formation of the underlayer) Next, I prepared the following materials. • 3.00 parts of electron transport material E1 as the first electron transport material. • 3.00 parts of electron transport material E2 as the second electron transport material. • Polyolefin resin (product name: UC-3920, manufactured by Toagosei Co., Ltd.) 0.10 parts • Polyvinyl acetal resin (product name: KS-5Z, manufactured by Sekisui Chemical Co., Ltd.) 0.10 parts • Blocked isocyanate compound as a crosslinking agent (product name: SBB-70P, manufactured by Asahi Kasei Corporation) 8.20 parts

[0059] These were dissolved in a mixed solvent of 88 parts THF and 12 parts orthoxylene. To this solution, 0.30 parts of metal oxide particles C1 were added, and the mixture was dispersed for 2 hours at 1800 rpm using a vertical sand mill with 1.0 mm diameter glass beads. Subsequently, the mixture was filtered under pressure using an ADVANTEC Teflon® filter (product name: PF020). The obtained undercoat coating solution was applied to a support by immersion, and the resulting coating film was heated at 170°C for 40 minutes to cure (polymerize), thereby forming an undercoat layer with a thickness of 1.5 μm.

[0060] (Formation of charge generation layer) Next, hydroxygallium phthalocyanine crystals (charge-generating material) in a crystalline form having strong peaks at Bragg angles (2θ±0.2°) of 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in CuKα characteristic X-ray diffraction were prepared. Ten parts of these hydroxygallium phthalocyanine crystals, five parts of polyvinyl butyral resin (product name: S-Rec BX-1, manufactured by Sekisui Chemical Co., Ltd.), and 250 parts of cyclohexanone were placed in a sand mill using 1 mm diameter glass beads and dispersed for 2 hours. Next, 250 parts of ethyl acetate were added to prepare a coating solution for the charge-generating layer. This coating solution for the charge-generating layer was applied to the undercoat layer by immersion to form a coating film, and the resulting coating film was dried at 95°C for 10 minutes to form a charge-generating layer with a thickness of 0.15 μm.

[0061] (Formation of a charge transport layer) Next, I prepared the following materials. 5 parts of charge transport material represented by the following formula (B-1) 5 parts of the charge transport material represented by the following formula (B-2) • Polycarbonate (product name: Yupiron Z-400, manufactured by Mitsubishi Engineering Plastics) 10 pieces These were dissolved in a mixed solvent of 25 parts orthoxylene, 25 parts methyl benzoate, and 25 parts dimethoxymethane to prepare a coating solution for the charge transport layer. [ka] [ka]

[0062] The charge transport layer coating solution prepared in this manner was applied to the aforementioned charge generation layer by immersion to form a coating film, and the coating film was heated and dried at 120°C for 30 minutes to form a charge transport layer with a thickness of 25 μm.

[0063] In this way, an electrophotographic photoreceptor having an undercoat layer, a charge generation layer, and a charge transport layer on a support was manufactured. After fabricating the electrophotographic photoreceptor, the particle size of the metal oxide particles was determined from microscopic images of the cross-section of the electrophotographic photoreceptor using a field emission scanning electron microscope (FE-SEM, product name: S-4800, manufactured by Hitachi High-Technologies).

[0064] [Evaluation of potential fluctuation characteristics] An electrophotographic photoreceptor was mounted in a modified Canon laser beam printer (product name: LBP-2510), and the following process conditions were set. The surface potential (evaluation of potential fluctuation characteristics) was then performed. The modifications included changing the process speed to 200 mm / s, setting the dark area potential to -700 V, and making the exposure light (image exposure light) variable. Further details are as follows.

[0065] Under conditions of 23°C and 50% RH humidity, the developing cartridge was removed from the evaluation unit, and a potential measuring device was inserted to perform the measurement. The potential measuring device consisted of a potential measuring probe positioned at the developing location of the developing cartridge, with the probe positioned in the center of the drum axis relative to the electrophotographic photoreceptor. Sensitivity was evaluated based on the potential of the bright area when irradiated with a predetermined amount of light. A smaller absolute value of the bright area potential indicates good sensitivity, while a larger value indicates low sensitivity.

[0066] First, the light intensity is 0.3 μJ / cm². 2 The settings were adjusted, and the initial potential of the bright area was measured. Next, the bright area potential after 40,000 prints was measured, and the difference (change) from the initial potential was calculated and evaluated as the potential fluctuation amount. A smaller potential fluctuation amount indicates that the potential fluctuation was more suppressed and the sensitivity was more stable. The evaluation results for Examples 1 to 16 and Comparative Examples 1 and 2 are shown in Table 3.

[0067] [Ghost's evaluation] The fabricated electrophotographic photoreceptor was mounted in the cyan process cartridge of the laser beam printer described above, and the process cartridge was then placed in the cyan process cartridge station to print an image.

[0068] First, images were output sequentially in the following order: a solid white image (1 image), five images for ghost evaluation, a solid black image (1 image), and five images for ghost evaluation.

[0069] As shown in Figure 3, the image used for ghost evaluation was created by outputting a solid square image 301 within a white image 302 at the beginning of the image, and then creating a halftone image 304 of a one-dot knight pattern as shown in Figure 4. In Figure 3, the ghost area 303 is the part where positive ghosting may occur. Positive ghosting was evaluated by measuring the density difference (Macbeth density difference) between the Macbeth density of the one-dot knight pattern halftone image 304 and the Macbeth density of the ghost area 303.

[0070] A spectrophotometer (product name: X-Rite504 / 508, manufactured by X-Rite Corporation) was used to measure the Macbeth density difference at 10 points in a single image used for ghost evaluation.

[0071] This operation was performed on all 10 images used for ghost evaluation, and the average of the total 100 points was calculated as the Macbeth density difference. A larger density difference (Macbeth density difference) indicates stronger positive ghosting. A smaller density difference (Macbeth density difference) indicates suppressed positive ghosting. The density difference (Macbeth density difference) obtained in Comparative Example 2 was evaluated as a relative value, designated as Ghost Evaluation Value 1. The evaluation results are shown in Table 3.

[0072] <Examples 2-10, 13, 14> Except for changing the type and amount of electron transport material mixed into the undercoat coating solution as shown in Table 2, electrophotographic photoreceptors 2-10, 13, and 14 were manufactured and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3. In Table 2, "ETM" indicates the electron transport material.

[0073] <Example 11> An electrophotographic photoreceptor 11 was manufactured in the same manner as in Example 1, except that hydroxygallium phthalocyanine used in the charge generation layer was replaced with chlorogallium phthalocyanine. The evaluation was performed in the same manner as in Example 1, and the evaluation results are shown in Table 3.

[0074] <Example 12> An electrophotographic photoreceptor 12 was manufactured in the same manner as in Example 1, except that the method for preparing the coating solution for the charge generation layer was changed as follows. The evaluation was performed in the same manner as in Example 1, and the evaluation results are shown in Table 3.

[0075] (Preparation of coating solution for charge generation layer) First, I prepared the following materials. 15 parts of crystalline titanyl phthalocyanine pigment (CG-01H, manufactured by ITchem) showing peaks at Bragg angles 2θ of 9.8°±0.3° and 27.1°±0.3° in the X-ray diffraction spectrum using CuKα rays. • Polyvinyl butyral (product name: Esrec BX-1, manufactured by Sekisui Chemical Co., Ltd.) 10 units 139 parts cyclohexanone 354 glass beads with a diameter of 0.9 mm

[0076] These materials were dispersed for 4 hours at a cooling water temperature of 18°C ​​using a sand mill (K-800, manufactured by Igarashi Machinery Manufacturing (now AIMEX), with a disc diameter of 70 mm and 5 discs). This process was carried out under conditions of 1,800 rotations per minute. By adding 326 parts of cyclohexanone and 465 parts of ethyl acetate to this dispersion, a coating solution for the charge generation layer was prepared.

[0077] <Example 15> An electrophotographic photoreceptor 15 was manufactured in the same manner as in Example 1, except that the following conductive layer was formed between the support and the undercoat layer.

[0078] (Formation of conductive layer) First, as a binding material, we use phenolic resin (phenolic resin monomer / oligomer) (product name: Priofen J-325, manufactured by DIC, resin solids content: 60%, density after curing: 1.3 g / cm³). 2 Fifty copies were prepared. This phenolic resin was dissolved in 35 parts of 1-methoxy-2-propanol as a solvent to obtain a solution.

[0079] Sixty parts of titanium dioxide particles A1 were added to this solution, and this was placed in a vertical sand mill using 120 parts of glass beads with an average particle size of 1.0 mm as the dispersion medium. The dispersion was carried out for 4 hours at a dispersion temperature of 23±3°C and a rotation speed of 1500 rpm (peripheral speed of 5.5 m / s) to obtain a dispersion. The glass beads were removed from this dispersion using a mesh.

[0080] Next, I prepared the following materials. • 0.01 part of silicone oil (product name: SH28 PAINT ADDITIVE, manufactured by Toray Dow Corning) as a leveling agent. • Silicone resin particles (product name: KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., average particle size: 2 μm, density: 1.3 g / cm³) are used as a surface roughening agent. 3 ) 8 copies These were added to the dispersion after the glass beads had been removed, stirred, and then pressure filtered using PTFE filter paper (product name: PF060, manufactured by Advantec Toyo) to prepare a coating solution for the conductive layer.

[0081] The conductive layer coating solution prepared in this manner was applied to the aforementioned support by immersion to form a coating film, and the coating film was heated at 150°C for 20 minutes to cure it, thereby forming a conductive layer with a thickness of 25 μm.

[0082] <Example 16> In Example 1, the polyvinyl acetal resin (product name: KS-5Z, manufactured by Sekisui Chemical Co., Ltd.) used in the preparation of the undercoat coating solution was replaced with polyvinyl butyral resin (product name: S-Rec BX-1, manufactured by Sekisui Chemical Co., Ltd.). Otherwise, the electrophotographic photoreceptor 16 was manufactured in the same manner as in Example 1.

[0083] <Comparative Example 1> An electrophotographic photoreceptor was manufactured in the same manner as in Example 1, except that the undercoating solution was prepared and used as described below. The results are shown in Table 3.

[0084] (Preparation of coating solution for the undercoat) A coating solution for the undercoat layer was prepared by dissolving 3.00 parts of electron transport material E1, 0.36 parts of polyolefin resin (product name: UC-3920, manufactured by Toagosei Co., Ltd.), and 6.41 parts of blocked isocyanate compound (product name: SBB-70P, manufactured by Asahi Kasei Corporation) in a mixed solvent of 50 parts 1-methoxy-2-propanol / 50 parts tetrahydrofuran.

[0085] <Comparative Example 2> An electrophotographic photoreceptor was manufactured in the same manner as in Example 1, except that the undercoating solution was prepared as follows.

[0086] (Preparation of coating solution for the undercoat) First, I prepared the following materials. ·Electron transport material E1 3.00 parts • Polyolefin resin (product name: UC-3920, manufactured by Toagosei Co., Ltd.) 0.10 parts • Polyvinyl acetal resin (product name: KS-5Z, manufactured by Sekisui Chemical Co., Ltd.) 0.10 parts • Blocked isocyanate compound as a crosslinking agent (product name: SBB-70P, manufactured by Asahi Kasei Corporation) 8.20 parts

[0087] These were dissolved in a mixed solvent of 88 parts THF and 12 parts orthoxylene. To this solution, 0.30 parts of metal oxide particles C1 were added, and the mixture was dispersed for 2 hours at 1800 rpm using a vertical sand mill with 1.0 mm diameter glass beads. Subsequently, the mixture was filtered under pressure using an ADVANTEC Teflon® filter (product name: PF020).

[0088] [Table 1]

[0089] [Table 2]

[0090] [Table 3]

[0091] The disclosure of embodiments of the present invention includes the following configurations. (Composition 1) An electrophotographic photoreceptor having a support, an undercoat formed on the support, and a charge generating layer formed on the undercoat, The lower layer is The compound represented by the following formula (1), The compound represented by the following formula (2), A crosslinking agent having a group that can bond to a hydroxyl group or a carboxyl group, Polymers of, and metal oxide particles An electrophotographic photoreceptor characterized by containing [something]. [ka] [ka] (In equations (1) and (2), R 1 and R 2 These show different groups from each other, and multiple R 1 They may be the same or different from each other, R 1 and R 2 Each of these is independently a substituted or unsubstituted alkyl group having 2 to 6 carbon atoms, a group derived by replacing at least one CH2 atom in the main chain of a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms with an oxygen atom, a group derived by replacing at least one CH2 atom in the main chain of a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms with NRa, a group derived by replacing at least one C2H4 atom in the main chain of a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms with COO, or a substituted aryl group. Ra represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The substituents of the substituted alkyl group, the group derived by replacing at least one CH2 in the main chain of the substituted alkyl group with an oxygen atom, the group derived by replacing at least one CH2 in the main chain of the substituted alkyl group with NRa, and the group derived by replacing at least one C2H4 in the main chain of the substituted alkyl group with COO are groups selected from the group consisting of alkyl groups having 1 to 5 carbon atoms, benzyl groups, alkoxycarbonyl groups, phenyl groups, hydroxyphenyl groups, hydroxyl groups, thiol groups, amino groups, and carboxyl groups. The substituents of the substituted aryl group are groups selected from the group consisting of halogen atoms, cyano groups, nitro groups, methyl groups, ethyl groups, isopropyl groups, n-propyl groups, n-butyl groups, acyl groups, alkoxy groups, alkoxycarbonyl groups, hydroxyl groups, thiol groups, amino groups, and carboxyl groups. R 1 and R 2 Each contains at least one hydroxyl group or carboxyl group. In equations (1) and (2), X is independently selected from the structure shown in equation (X1), the structure shown in equation (X2), and the structure shown in equation (X3). [ka] [ka] [ka] In equations (X1), (X2), and (X3), R 11 ~R 18 , R 21 ~R 24 , R 31 , and R 32 Each of these independently represents a hydrogen atom, a halogen atom, a cyano group, or a nitro group. (Configuration 2) The electrophotographic photoreceptor according to configuration 1, characterized in that the average primary particle size of the metal oxide particles, measured by observing the cross-section of the undercoat layer with a scanning electron microscope (SEM), is 20 nm or more and 150 nm or less. (Composition 3) The electrophotographic photoreceptor according to configuration 1 or 2, characterized in that the metal oxide particles contain a metal oxide selected from titanium oxide, zinc oxide, strontium titanate, and barium titanate. (Composition 4) The electrophotographic photoreceptor according to any one of configurations 1 to 3, characterized in that the metal oxide particles are treated with an organosilane compound. (Composition 5) The electrophotographic photoreceptor according to any one of configurations 1 to 4, characterized in that the charge generating layer contains hydroxygallium phthalocyanine or chlorogallium phthalocyanine. (Composition 6) An electrophotographic photoreceptor according to any one of configurations 1 to 5, characterized in that the mass ratio of the metal oxide particles to the polymer (metal oxide particles / polymer) is 0.009 or more and 0.160 or less. (Composition 7) A process cartridge characterized by integrally supporting an electrophotographic photoreceptor as described in any of configurations 1 to 6, and at least one means selected from the group consisting of a charging means, a developing means, and a cleaning means, and being detachably attached to the main body of an electrophotographic apparatus. (Composition 8) An electrophotographic apparatus characterized by comprising an electrophotographic photoreceptor according to any of configurations 1 to 6, and a charging means, an exposure means, a developing means, and a transfer means. [Explanation of symbols]

[0092] 1. Electrophotographic photoreceptor 2 axes 3. Charging means 4 Exposure light 5. Developing means 6. Transfer means 7. Cleaning methods 8 Fixing means 9 Process Cartridges 10 Guidance methods P Transfer Material

Claims

1. An electrophotographic photoreceptor having a support, an undercoat formed on the support, and a charge generating layer formed on the undercoat, The lower layer is The compound represented by the following formula (1), The compound represented by the following formula (2), A crosslinking agent having a group that can bond to a hydroxyl group or a carboxyl group, Polymers of, and metal oxide particles An electrophotographic photoreceptor characterized by containing [something]. 【Chemistry 1】 【Chemistry 2】 (In Formula (1) and Formula (2), R １ and R ２ represent different groups from each other, and a plurality of R １ may be the same as or different from each other. R １ and R ２ are each independently a substituted or unsubstituted alkyl group having 2 to 6 carbon atoms, a group derived by replacing at least one CH ２ in the main chain of a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms in the main chain with an oxygen atom, a group derived by replacing at least one CH ２ in the main chain of a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms in the main chain with NRa, a group derived by replacing at least one C ２ H ４ in the main chain of a substituted or unsubstituted alkyl group having 3 to 6 carbon atoms in the main chain with COO, or a substituted aryl group.) Ra represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The substituted alkyl group, the CH in the main chain of the substituted alkyl group ２ A group derived by replacing at least one of the atoms with an oxygen atom, CH in the main chain of the substituted alkyl group ２ A group derived by replacing at least one of with NRa, and C in the main chain of the substituted alkyl group. ２ H ４ The substituents of the group derived by replacing at least one of the COO groups are groups selected from the group consisting of alkyl groups having 1 to 5 carbon atoms, benzyl groups, alkoxycarbonyl groups, phenyl groups, hydroxyphenyl groups, hydroxyl groups, thiol groups, amino groups, and carboxyl groups. The substituents of the substituted aryl group are groups selected from the group consisting of halogen atoms, cyano groups, nitro groups, methyl groups, ethyl groups, isopropyl groups, n-propyl groups, n-butyl groups, acyl groups, alkoxy groups, alkoxycarbonyl groups, hydroxyl groups, thiol groups, amino groups, and carboxyl groups. R １ and R ２ Each contains at least one hydroxyl group or carboxyl group. In equations (1) and (2), X is independently selected from the structure shown in equation (X1), the structure shown in equation (X2), and the structure shown in equation (X3). 【Transformation 3】 【Chemistry 4】 【Transformation 5】 In equations (X1), (X2), and (X3), R １１ ~R １８ , R ２１ ~R ２４ , R ３１ , and R ３２ Each of these independently represents a hydrogen atom, a halogen atom, a cyano group, or a nitro group.

2. The electrophotographic photoreceptor according to claim 1, characterized in that the average primary particle size of the metal oxide particles, measured by observing the cross-section of the undercoat layer with a scanning electron microscope (SEM), is 20 nm or more and 150 nm or less.

3. The electrophotographic photoreceptor according to claim 1, characterized in that the metal oxide particles contain a metal oxide selected from titanium oxide, zinc oxide, strontium titanate, and barium titanate.

4. The electrophotographic photoreceptor according to claim 1, characterized in that the metal oxide particles are treated with an organosilane compound.

5. The electrophotographic photoreceptor according to claim 1, characterized in that the charge generating layer contains hydroxygallium phthalocyanine or chlorogallium phthalocyanine.

6. The electrophotographic photoreceptor according to claim 1, characterized in that the mass ratio of the metal oxide particles to the polymer (metal oxide particles / polymer) is 0.009 or more and 0.160 or less.

7. A process cartridge characterized by integrally supporting an electrophotographic photoreceptor according to any one of claims 1 to 6 and at least one means selected from the group consisting of a charging means, a developing means, and a cleaning means, and being detachably attached to the main body of an electrophotographic apparatus.

8. An electrophotographic apparatus characterized by comprising an electrophotographic photoreceptor according to any one of claims 1 to 6, and a charging means, an exposure means, a developing means, and a transfer means.

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