Electrophotographic photoreceptor, process cartridge and electrophotographic device

Abstract

To provide an electrophotographic photoreceptor which suppresses cracking while being transported at low temperature to provide good images.SOLUTION: An electrophotographic photoreceptor is provided, comprising a surface layer containing a polycarbonate resin (α) having structural units represented by formulas (A) and (B) below, and a polyarylate resin (β) having a structure with a dimethylsiloxane moiety.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Electrophotographic photoreceptors used in electrophotographic devices may be transported at temperatures below 0°C when they are shipped from the place of production to the area where they are used, and if the electrophotographic photoreceptor is subjected to impact during this low-temperature transport, there is a risk that cracks will occur in the surface layer (hereinafter referred to as "cracks"). In contrast, siloxane resins are known to have high fluidity and do not lose fluidity even at temperatures below 0°C, and introducing siloxane resins into the surface layer of an electrophotographic photoreceptor is expected to have the effect of suppressing the occurrence of cracks in the surface layer. However, polycarbonate resin, which is generally used as a material for the surface layer of an electrophotographic photoreceptor, has a high stacking tendency, and it is difficult to effectively introduce siloxane resin into the surface layer, so there is still room for improvement in suppressing the occurrence of cracks in the surface layer during low-temperature transportation (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-128106 A Summary of the Invention [Problem to be solved by the invention]

[0004] According to the investigations of the present inventors, the electrophotographic photoreceptor described in the examples of Patent Document 1 has improved abrasion resistance as a polycarbonate resin and can accommodate a longer life. However, the polycarbonate resin has a high stacking tendency, making it difficult to effectively introduce a siloxane resin into the surface layer. As a result, there was an issue that cracks were generated in the surface layer when the polycarbonate resin was subjected to impact during low-temperature transportation.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an electrophotographic photoreceptor which is capable of suppressing the occurrence of cracks in the surface layer of the electrophotographic photoreceptor during low-temperature transportation and which makes it possible to obtain good images. [Means for solving the problem]

[0006] The above object can be achieved by the present invention described below. That is, the electrophotographic photoreceptor according to the present invention is an electrophotographic photoreceptor having a surface layer, The surface layer contains a polycarbonate resin (α) and a polycarbonate resin (β), The polycarbonate resin (α) has a structural unit represented by the following formula (A) and a structural unit represented by the following formula (B), The polycarbonate resin (β) has a structure having a dimethylsiloxane moiety. The electrophotographic photoreceptor is characterized in that [ka] Effect of the Invention

[0007] According to the present invention, it is possible to provide an electrophotographic photoreceptor which is capable of suppressing the occurrence of cracks in the surface layer of the electrophotographic photoreceptor during transportation at low temperatures and which makes it possible to obtain good images. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a schematic configuration of an electrophotographic apparatus having a process cartridge equipped with an electrophotographic photosensitive member of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described in detail below with reference to preferred embodiments. The inventors of the present invention have found that the photoconductor described in Patent Document 1 is likely to crack on the surface layer when it is stored in a low-temperature environment of 0°C or less while attached to an electrophotographic cartridge and subjected to impact. In order to solve this problem, they tried to see if the occurrence of cracks could be suppressed by introducing a siloxane resin, which is known to not lose fluidity even at 0°C or less, into the surface layer of the photoconductor. However, as a result of the inventors' investigation, they found that although a small amount of siloxane resin could be introduced into the surface layer, the effect of suppressing cracks was insufficient, and it was difficult to introduce a large amount of siloxane resin. The inventors of the present invention thought that this was due to the high stacking property of polycarbonate resin, which makes it difficult to dissolve other resins.

[0010] Therefore, we conducted a study to effectively introduce siloxane resin into the surface layer by breaking down the stacking property of polycarbonate resin to a degree that does not impair the abrasion resistance of polycarbonate resin. As a result, it was found that if the surface layer of a photoreceptor contains polycarbonate resin (α) and polycarbonate resin (β), the polycarbonate resin (α) has a structural unit represented by the following formula (A) and a structural unit represented by the following formula (B), and the polycarbonate resin (β) has a structure having a dimethylsiloxane moiety, the occurrence of cracks in the surface layer under a low-temperature transportation environment can be suppressed. [ka]

[0011] This is because the conventional polycarbonate resin, which is only the structure of the above formula (A), has a high stacking property, whereas the structure of the above formula (B), which has a different arrangement of methyl groups, is mixed in an appropriate amount, which moderately breaks down the stacking property of the polycarbonate resin and generates gaps between molecules. It is assumed that the siloxane resin will be more likely to enter the gaps than before, and as a result, the inventors believe that the effect of the siloxane resin ensures the flowability of the resin, making it a more flexible resin and therefore excellent in crack resistance. As a result of the effects described above, the present invention can achieve suppression of the occurrence of cracks in the surface layer of an electrophotographic photoreceptor during transportation at low temperatures.

[0012] [Electrophotographic photoreceptor] The electrophotographic photoreceptor of the present invention is characterized by having a surface layer, and specifically, it preferably has an undercoat layer, a charge generating layer, and a surface layer on a support. The method for producing the electrophotographic photoreceptor of the present invention includes a method of preparing the coating liquid for each layer described later, coating the layers in the desired order, and drying the liquid. At this time, the coating liquid can be applied by dip coating, spray coating, inkjet coating, roll coating, die coating, blade coating, curtain coating, wire bar coating, ring coating, etc. Among these, dip coating is preferred from the viewpoint of efficiency and productivity. The support and each layer will be described below.

[0013] <Support> In the present invention, the electrophotographic photoreceptor has a support. In the present invention, the support is preferably a conductive support having electrical conductivity. The shape of the support may be a cylinder, a belt, a sheet, or the like. Among them, a cylindrical support is preferable. The surface of the support may be subjected to electrochemical treatment such as anodization, blasting, cutting, or the like. The support is preferably made of a metal, a resin, or a glass. Examples of the metal include aluminum, iron, nickel, copper, gold, stainless steel, and alloys thereof. Among them, an aluminum support using aluminum is preferable. Furthermore, the resin or glass may be made conductive by a process such as mixing with or coating with a conductive material.

[0014] <Undercoat layer> In the present invention, an undercoat layer may be provided on the support. By providing the undercoat layer, the adhesion function between layers is improved and a charge injection blocking function can be imparted. The electrophotographic photoreceptor of the present invention preferably contains a polyamide resin and titanium oxide particles. The undercoat layer preferably contains a resin. Alternatively, the undercoat layer may be formed as a cured film by polymerizing a composition containing a monomer having a polymerizable functional group. Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, acrylic resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl phenol resin, alkyd resin, polyvinyl alcohol resin, polyethylene oxide resin, polypropylene oxide resin, polyamide resin, polyamic acid resin, polyimide resin, polyamideimide resin, and cellulose resin. Examples of the polymerizable functional group contained in the monomer having a polymerizable functional group include an isocyanate group, a blocked isocyanate group, a methylol group, an alkylated methylol group, an epoxy group, a metal alkoxide group, a hydroxyl group, an amino group, a carboxyl group, a thiol group, a carboxylic anhydride group, and a carbon-carbon double bond group.

[0015] For the purpose of improving electrical properties, the undercoat layer may further contain an electron transporting material, a metal oxide, a metal, a conductive polymer, etc. Among these, it is preferable to use an electron transporting material or a metal oxide. Examples of the electron transport substance include a quinone compound, an imide compound, a benzimidazole compound, a cyclopentadienylidene compound, a fluorenone compound, a xanthone compound, a benzophenone compound, a cyanovinyl compound, an aryl halide compound, a silole compound, a boron-containing compound, etc. An electron transport substance having a polymerizable functional group may be used as the electron transport substance, and the undercoat layer may be formed as a cured film by copolymerizing the electron transport substance with the monomer having the polymerizable functional group described above. Examples of metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, silicon dioxide, etc. Examples of metals include gold, silver, aluminum, etc., and it is preferable to use titanium oxide particles. The undercoat layer may further contain additives such as an antioxidant and an ultraviolet absorber. Specific examples of such additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0016] The average thickness of the undercoat layer is preferably from 0.1 μm to 50 μm, more preferably from 0.2 μm to 40 μm, and particularly preferably from 0.3 μm to 30 μm. The undercoat layer can be formed by preparing a coating solution for the undercoat layer containing the above-mentioned materials and solvent, forming the coating film on a support, and drying and / or curing the coating film. Examples of the solvent used in the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0017] <Charge generation layer> The electrophotographic photoreceptor preferably further comprises a charge generating layer on the support and the undercoat layer. The charge generating layer preferably contains a charge generating material and a resin. Examples of the charge generating material include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferred. Among phthalocyanine pigments, oxytitanium phthalocyanine pigments, chlorogallium phthalocyanine pigments, and hydroxygallium phthalocyanine pigments are preferred. In particular, it is preferred to contain an oxytitanium phthalocyanine pigment having a peak at a Bragg angle 2θ of 27.2°±0.2° in a CuKα characteristic X-ray diffraction spectrum. The content of the charge generating material in the charge generating layer is preferably from 40% by mass to 85% by mass, and more preferably from 60% by mass to 80% by mass, based on the total mass of the charge generating layer.

[0018] Examples of the resin include polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, acrylic resin, silicone resin, epoxy resin, melamine resin, polyurethane resin, phenol resin, polyvinyl alcohol resin, cellulose resin, polystyrene resin, polyvinyl acetate resin, polyvinyl chloride resin, etc. Among these, polyvinyl butyral resin is more preferable. The charge generating layer may further contain additives such as an antioxidant and an ultraviolet absorbing agent, etc. Specific examples of such additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0019] The average thickness of the charge generating layer is preferably from 0.1 μm to 1 μm, and more preferably from 0.15 μm to 0.4 μm. The charge generating layer can be formed by preparing a coating solution for the charge generating layer containing the above-mentioned materials and solvent, forming a coating film of this on the undercoat layer, and drying it. Examples of the solvent used in the coating solution include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents.

[0020] <Surface layer> The electrophotographic photoreceptor of the present invention has a surface layer on the charge generating layer. The surface layer is characterized by having a polycarbonate resin (α) and a polycarbonate resin (β). It is preferable that the surface layer further contains a charge transport material. The polycarbonate resin (α) has a structural unit represented by the following formula (A) and a structural unit represented by the following formula (B). The polycarbonate resin (α) may also contain one or more structural units represented by the following general formula (C) within a range that does not impair the effects of the present invention. Among these, it is more preferable that the polycarbonate resin (α) has a structural unit represented by formula (C-1), since this can improve the crack resistance of the surface layer without impairing the solubility of the resin. [ka] [ka] (In the general formula (C), X 101 represents a single bond or a divalent group, R 101 ~R 104 each independently represents a hydrogen atom, an alkyl group, or an aryl group.

[0021] Specific examples (C-1) to (C-13) of the structure represented by general formula (C) are shown below. [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka] [ka]

[0022] In the present invention, the copolymerization form of the polycarbonate resin (α) may be any form such as block copolymerization, random copolymerization, alternating copolymerization, etc. The structure of the polycarbonate resin (α) can be analyzed by analyzing the structural units using a known analytical device such as NMR, GPC, or MALDI.

[0023] The polycarbonate resin (β) of the present invention is characterized by having a structure having a dimethylsiloxane moiety. The polycarbonate resin (β) has a structure represented by the following formula (PC-β). [ka]

[0024] Specific examples of the structure represented by formula (PC-β) are shown below. In particular, it is preferable to have a structure represented by the following formula (D) or (E), which has been found by the inventors to be more effective in suppressing cracking in the surface layer. [ka] In formula (D), R 21 and R 22 each independently represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms; R 23 is a methyl group, n1 is an integer of 2 to 4, and n2 is an integer of 1 to 600. [ka] In formula (E), R 31 represents a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms; R 32 is a methyl group, and R 33 are each independently the same or different monovalent hydrocarbon groups containing no aliphatic unsaturated bonds, R34 are each independently the same or different monovalent hydrocarbon groups containing no aliphatic unsaturated bonds, Y and Y' are alkylene groups having 2 or more carbon atoms, alkyleneoxyalkylene groups, or oxygen atoms, na is 0 or 1, nb is 1 or 2, and nc is 1 or 2, with the proviso that the sum of na, nb, and nc is 3, n1 to n4 are each an integer of 0 or more, the sum of n1, n2, n3, and n4 is an integer of 2 to 600, the sum of n3 and n4 is an integer of 1 or more, and a is an integer of 0 to 4. The chemical structure of the present invention can be structurally analyzed by a nuclear magnetic resonance (NMR) apparatus.

[0025] Specific examples of formulae (D) and (E) include the following: [ka] [ka] [ka] [ka] [ka] [ka]

[0026] In the above formulas (D-1) to (D-5) and (E-1), n, which is the number of repeating units of the dimethylsilxylene group, is preferably 1 or more and 600 or less, more preferably 10 or more and 300 or less, particularly preferably 20 or more and 200 or less, and most preferably 30 or more and 150 or less. By setting n, which is the number of repeating units of the dimethylsiloxylene group, to 600 or less, compatibility with the polycarbonate resin (α) is improved, and the reaction can be completed in the polymerization step. Therefore, since it is possible to prevent unreacted organosiloxane-modified phenolic compounds from remaining in the final polycarbonate copolymer after polymerization, the resin does not become cloudy, and when used as a resin for an electrophotographic photoreceptor, an increase in the residual potential on the surface of the electrophotographic photoreceptor can be suppressed. On the other hand, by setting n, which is the number of repeating units of the dimethylsilxylene group, to 1 or more, sufficient surface energy can be imparted to the electrophotographic photosensitive member, and further adhesion of foreign matter can be effectively prevented.

[0027] In the polycarbonate resin (α) of the present invention, the total amount of the structural unit represented by the formula (A) and the structural unit represented by the formula (B) is 40 mol% or more and 60 mol% or less relative to the total amount of the structural unit represented by the formula (A), the structural unit represented by the formula (B), and the structural unit represented by the formula (C), and the amount of the structural unit represented by the formula (C) in the polycarbonate resin (α) is 40 mol% or more and 60 mol% or less relative to the total amount of the structural unit represented by the formula (A), the structural unit represented by the formula (B), and the structural unit represented by the formula (C), from the viewpoint of moderately destroying the stacking property of the polycarbonate resin (α) and moderately introducing the polycarbonate resin (β) into the surface layer. Such values ​​can be obtained by structural analysis by NMR and quantitative analysis by gas chromatography mass spectrometry (GC / MS).

[0028] Furthermore, the content of the structure having the dimethylsiloxane moiety in the polycarbonate resin (β) is preferably 3% by mass or more and 20% by mass or less with respect to the total mass of the polycarbonate resin (β), and the content of the polycarbonate resin (β) in the surface layer is preferably 5% by mass or more and 15% by mass or less with respect to the polycarbonate resin (α). Such values ​​can be determined by structural analysis using NMR and quantitative analysis using gas chromatography mass spectrometry (GC / MS).

[0029] In addition to the polycarbonate resin, the surface layer may use other resins as the binder resin as long as the effects of the present invention are not impaired. Specific examples include polyester resins, siloxane resins, polymethacrylate resins, polysulfone resins, polystyrene resins, etc. The other resins may be blended or copolymerized in plural kinds. The surface layer may also contain additives such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, slipping agents, and abrasion resistance improvers. Specific examples of such additives include hindered phenol compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluororesin particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles. The average thickness of the surface layer is preferably 5 μm or more and 50 μm or less, more preferably 8 μm or more and 40 μm or less, and particularly preferably 10 μm or more and 30 μm or less. The average thickness of the surface layer can be determined, for example, by observing the cross section with a scanning electron microscope (SEM).

[0030] The surface layer can be formed by preparing a coating solution for the surface layer containing the above-mentioned materials and solvent, forming the coating film on the charge generating layer, and drying it. Examples of the solvent used in the coating solution for forming the surface layer include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon solvents.

[0031] The surface layer preferably contains a charge transport material. Examples of the charge transport material include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from these materials. Among these, triarylamine compounds and benzidine compounds are preferred. In addition, a plurality of types of charge transport materials may be contained together. Specific examples of charge transport materials (CTM-1) to (CTM-19) are shown below.

[0032] [ka] [ka]

[0033] Examples of the resin include polyester resin, polycarbonate resin, acrylic resin, polystyrene resin, etc. Among these, polycarbonate resin and polyester resin are preferable. As the polyester resin, polyarylate resin is particularly preferable. The content ratio (mass ratio) of the charge transport material to the resin is preferably from 4:10 to 20:10, and more preferably from 5:10 to 12:10. The content of the charge transport material in the surface layer is preferably from 25% by weight to 70% by weight, and more preferably from 30% by weight to 55% by weight, based on the total weight of the surface layer.

[0034] The surface layer can be formed by forming a coating film of a coating liquid for the surface layer, which is prepared by dissolving a charge transport material, a polycarbonate resin (α), a polycarbonate resin (β), a binder resin, etc. in a solvent, on the charge generating layer, and drying the coating film. Examples of the solvent used in the coating liquid for forming the surface layer include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon solvents. These solvents may be used alone, or two or more types may be mixed and used. Among these solvents, it is preferable to use an ether-based solvent or an aromatic hydrocarbon solvent from the viewpoint of resin solubility.

[0035] [Process cartridges, electrophotographic devices] The process cartridge of the present invention is characterized in that it integrally supports the electrophotographic photosensitive member described above and at least one means selected from the group consisting of a charging means, a developing means, a transfer means and a cleaning means, and is detachably attachable to the main body of the electrophotographic apparatus. That is, the process cartridge of the present invention is a process cartridge detachably mountable to the main body of an electrophotographic apparatus, and includes a cylindrical electrophotographic photosensitive member, charging means for charging the electrophotographic photosensitive member, and developing means for developing the electrophotographic photosensitive member with toner to form a toner image, the developing means recovering transfer residual toner remaining on the electrophotographic photosensitive member after the toner image has been transferred to a transfer material, the electrophotographic photosensitive member being the electrophotographic photosensitive member described above, The electrophotographic photoreceptor has a surface layer, the surface layer contains a polycarbonate resin (α) and a polycarbonate resin (β), the polycarbonate resin (α) has a structural unit represented by the above formula (A) and a structural unit represented by the above formula (B), The process cartridge is characterized in that the polycarbonate resin (β) has a structure having a dimethylsiloxane moiety. Further, the electrophotographic apparatus of the present invention is an electrophotographic photosensitive member having the electrophotographic photosensitive member, charging means, exposure means, developing means and transfer means described above, characterized in that the electrophotographic photosensitive member is the electrophotographic photosensitive member described above, and the developing means recovers transfer residual toner remaining on the electrophotographic photosensitive member after a toner image is transferred from the electrophotographic photosensitive member to a transfer material.

[0036] FIG. 1 shows an example of a schematic configuration of an electrophotographic apparatus having a process cartridge equipped with an electrophotographic photosensitive member. A cylindrical electrophotographic photoreceptor 1 is driven to rotate around an axis 2 at a predetermined peripheral speed in the direction of the arrow. The surface of the electrophotographic photoreceptor 1 is charged to a predetermined positive or negative potential by a charging means 3. Although the figure shows a roller charging method using a roller-type charging member, a corona charging method, a proximity charging method, an injection charging method, or other charging methods may be adopted. Exposure light 4 is irradiated from an exposure means (not shown) onto the charged surface of the electrophotographic photoreceptor 1, and an electrostatic latent image corresponding to the target image information is formed. The electrostatic latent image formed on the surface of the electrophotographic photoreceptor 1 is developed with toner contained in a developing means 5, and a toner image is formed on the surface of the electrophotographic photoreceptor 1. The toner image formed on the surface of the electrophotographic photoreceptor 1 is transferred to a transfer material 7 by a transfer means 6. The transfer material 7 to which the toner image has been transferred is transported to a fixing means 8, where the toner image is fixed, and the transfer material is printed out outside the electrophotographic device. The electrophotographic device may have a cleaning means 9 for removing deposits such as toner remaining on the surface of the electrophotographic photoreceptor 1 after transfer. Also, a so-called cleanerless system may be used in which the deposits are removed by a developing means or the like without providing a separate cleaning means. The electrophotographic apparatus may have a charge eliminating mechanism that eliminates charge on the surface of the electrophotographic photoreceptor 1 by pre-exposure light 10 from a pre-exposure means (not shown). Also, in order to mount and remove the process cartridge 11 of the present invention to and from the main body of the electrophotographic apparatus, a guide means 12 such as a rail may be provided. The electrophotographic photoreceptor of the present invention can be used in laser beam printers, LED printers, copiers, and the like. EXAMPLES

[0037] The present invention will be described in more detail below using examples and comparative examples. The present invention is not limited to the following examples without departing from the gist of the present invention. In the following examples, "parts" are by mass unless otherwise specified.

[0038] (Examples 1 to 26) <Production Example of Coating Solution for Undercoat Layer> 10 parts of polyamide resin CM-8000 (manufactured by Toray Industries, Inc.), 30 parts of titanium oxide SMT-500SAS (manufactured by Teika Co., Ltd.), and 100 parts by mass of methanol were mixed, and then placed in a vertical sand mill using glass beads having a diameter of 1.0 mm, and dispersed at a rotation speed of 800 rpm for a dispersion treatment time of 5 hours and a cooling water temperature of 18° C. to obtain a dispersion. The glass beads were removed from this dispersion using a mesh (opening: 150 μm), and the dispersion was filtered through a 4.5 μm filter to prepare a coating liquid for an undercoat layer.

[0039] <Production Example of Coating Solution for Charge Generating Layer> A coating solution for the charge generating layer was prepared by mixing and dispersing 12 parts of a charge generating material (oxytitanium phthalocyanine pigment having a maximum peak at a Bragg angle 2θ of 27.2 degrees in X-ray diffraction), 24 parts of polyvinyl butyral resin (S-LEC BL-1), and 300 parts of t-butyl acetate using a sand grinder.

[0040] <Specific examples of polycarbonate resin (α)> Specific examples of polycarbonate resins (α) represented by the structural unit represented by formula (A), the structural unit represented by formula (B) and the structural unit represented by formula (C) are shown in Table 1. In Table 1, resin 1 represents the structural unit represented by formula (A), resin 2 represents the structural unit represented by formula (B) and resin 3 represents the structural unit represented by formula (C). The polycarbonate resins were synthesized by known methods.

[0041] [Table 1]

[0042] <Specific examples of polycarbonate resin (β)> Specific examples of polycarbonate resins (β) having a dimethylsiloxane moiety are shown in Table 2. In Table 2, resin 1 is a structural unit of polycarbonate, and resin 2 is a structural unit represented by the formula (PC-β). The polycarbonate resins were synthesized by known methods.

[0043] [Table 2]

[0044] <Production Example of Surface Layer Coating Solution> (Production Example of Surface Layer Coating Solution (1)) A coating solution (1) for the surface layer was prepared by dissolving 10 parts of the amine compound (charge transport material) represented by the aforementioned CTM-10, 10 parts of the structural unit of the polycarbonate resin (α) represented by the aforementioned PC-α-01, and 1 part of the structural unit of the polycarbonate resin (β) represented by PC-β-1 in a mixed solvent of 30 parts of tetrahydrofuran and 70 parts of toluene.

[0045] (Production Examples of Surface Layer Coating Solutions (2) to (26)) Surface layer coating solutions (2) to (26) were prepared in the same manner as in the production example of surface layer coating solution (1), except for changes as shown in the following Table 3. Table 3 shows the prepared coating solutions.

[0046] [Table 3]

[0047] <Production Example of Electrophotographic Photoreceptor> (Production Example of Electrophotographic Photoreceptor (1)) An aluminum cylinder (JIS H 4000:2006 A3003P, aluminum alloy) with a diameter of 20 mm and a length of 254.8 mm was machined (JIS B 0601:2014, ten-point average roughness Rzjis: 0.8 μm) and used as a support. The coating liquid for the undercoat layer was dip-coated onto the support, and the resulting coating film was dried at 150° C. for 20 minutes to form an undercoat layer with a thickness of 4.2 μm. Next, the coating liquid for the charge generating layer was dip-coated onto the undercoat layer, and the resulting coating was dried at 140° C. for 10 minutes to form a charge generating layer having a thickness of 0.3 μm. Subsequently, the surface layer coating solution (1) was dip-coated on the charge generating layer, and the resulting coating was dried for 30 minutes at 125° C. to form a surface layer having a thickness of 23.0 μm. The thickness of the surface layer can be measured, for example, by SEM observation of the cross section.

[0048] (Production Examples of Electrophotographic Photoreceptors (2) to (26)) In the production example of the electrophotographic photoreceptor (1), the coating liquid for the surface layer was changed, and the viscosity of the coating liquid for the surface layer, or the coating speed during dip coating, or both the viscosity and the coating speed during dip coating were changed so as to be optimized for the film thickness as shown in Table 4. Except for this, the electrophotographic photoreceptors (2) to (26) were produced in the same manner as in the production example of the electrophotographic photoreceptor (1), as shown in Table 4.

[0049] [Table 4]

[0050] [Evaluation method for crack testing during low temperature transportation] The degree of cracking in the surface layer of the electrophotographic photoreceptor during low-temperature transportation was alternatively evaluated by the following evaluation method. The electrophotographic photoreceptor was replaced from the cartridge of a LaserJet Pro M-452dw (manufactured by Hewlett-Packard Co., Ltd.) and the evaluation was carried out. Any of the cartridges installed in the printer may be used for the evaluation. After the cartridge was taken out, the electrophotographic photoreceptor mounted on the product was removed, and the various electrophotographic photoreceptors manufactured in the present invention were attached to reassemble the cartridge. The assembled cartridge was left standing in an environment of 0°C / 15% RH for 30 days, and then left standing in an environment of 23°C / 50% RH for 1 day. Thereafter, the electrophotographic photoreceptor was removed from the cartridge again, and the surface of the electrophotographic photoreceptor was observed using a laser microscope (e.g., Keyence VK-X3000) to observe the state of cracks occurring on the surface. Thereafter, the electrophotographic photoreceptor was attached to the cartridge again, and attached to the LaserJet Pro M-452dw, and a halftone image was output in an environment of 23°C / 50% RH, and the image was evaluated. The occurrence of cracks in the surface layer and the image were evaluated according to the following rankings. Rank A: When observed with a laser microscope, no cracks were found on the surface of the electrophotographic photoreceptor, and the image was not affected. Rank B: When observed with a laser microscope, slight cracks were found on the surface of the electrophotographic photoreceptor, but the image was not affected. Rank C: Cracks are found on the surface of the electrophotographic photoreceptor when observed with a laser microscope, but they have no effect on images in practical use. Rank D: Cracks were found on the surface of the electrophotographic photosensitive member when observed with a laser microscope, and images were affected in practical use.

[0051] The evaluation results are shown in Table 5 below. [Table 5]

[0052] (Comparative Examples 1 to 3) <Specific examples of comparative polycarbonate resin (α)> Specific examples of comparative polycarbonate resins (α) represented by the structural unit represented by formula (A), the structural unit represented by formula (B) and the structural unit represented by formula (C-1) are shown in Table 6. In Table 6, resin 1 represents the structural unit represented by formula (A), resin 2 represents the structural unit represented by formula (B) and resin 3 represents the structural unit represented by formula (C). Comparative polycarbonate resins (α) were synthesized by a known method. [Table 6]

[0053] <Specific examples of comparative polycarbonate resin (β)> Specific examples of comparative polycarbonate resins (β) having a dimethylsiloxane moiety are shown in Table 7. In Table 7, resin 1 shows a polycarbonate structural unit, and resin 2 shows a structural unit represented by formula (PC-β). Comparative polycarbonate resins (β) were synthesized by a known method. [Table 7]

[0054] <Production Example of Coating Solution for Surface Layer for Comparative Example> Comparative surface layer coating solutions (1) to (3) were prepared in the same manner as in the production example of surface layer coating solution (1), except for the changes shown in Table 8. Table 8 shows the prepared coating solutions.

[0055] [Table 8]

[0056] <Production Example of Comparative Electrophotographic Photoreceptor> In the manufacturing example of the electrophotographic photoreceptor (1), the surface layer coating liquid was changed to the comparative surface layer coating liquid, and the viscosity of the comparative surface layer coating liquid, or the coating speed during dip coating, or both the viscosity and the coating speed during dip coating were changed so as to be optimized for the target film thickness. In the same manner as in the manufacturing example of the electrophotographic photoreceptor (1), comparative electrophotographic photoreceptors (1) to (3) were manufactured according to the combinations shown in Table 9.

[0057] [Table 9]

[0058] The electrophotographic photoreceptors for comparison were also subjected to a crack test at low temperature in the same manner as the electrophotographic photoreceptors. The results are shown in Table 10. The electrophotographic photoreceptors for comparison were all rated as D, and cracks occurred on the surface of the electrophotographic photoreceptor, resulting in images that were problematic in practical use.

[0059] [Table 10]

[0060] The disclosure of this embodiment includes the following configuration. (Configuration 1) An electrophotographic photoreceptor having a surface layer, The surface layer contains a polycarbonate resin (α) and a polycarbonate resin (β), The polycarbonate resin (α) has a structural unit represented by the following formula (A) and a structural unit represented by the following formula (B), The electrophotographic photoreceptor, wherein the polycarbonate resin (β) has a structure having a dimethylsiloxane moiety. [ka] (Configuration 2) The electrophotographic photoreceptor according to Configuration 1, wherein the polycarbonate resin (α) further has a structural unit represented by the following formula (C): [ka] (In formula (C), X 101 represents a single bond or a divalent group, R 101 ~R 104 each independently represents a hydrogen atom, an alkyl group, or an aryl group. (Configuration 3) In the polycarbonate resin (α), the total amount of the structural unit represented by the formula (A) and the structural unit represented by the formula (B) is 40 mol % or more and 60 mol % or less based on the total amount of the structural unit represented by the formula (A), the structural unit represented by the formula (B), and the structural unit represented by the formula (C); the amount of the structural unit represented by the formula (C) in the polycarbonate resin (α) is 40 mol % or more and 60 mol % or less based on the total amount of the structural unit represented by the formula (A), the structural unit represented by the formula (B), and the structural unit represented by the formula (C); 3. The electrophotographic photoreceptor according to configuration 2. (Configuration 4) The electrophotographic photoreceptor according to any one of configurations 1 to 3, wherein the structure having a dimethylsiloxane moiety is a structure represented by the following formula (D) or (E): [ka] (In formula (D), R 21 and R 22 each independently represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms; R 23 is a methyl group, n1 is an integer from 2 to 4, and n2 is an integer from 1 to 600. [ka] (In formula (E), R 31 represents a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms; R 32 is a methyl group, and R 33 are each independently the same or different monovalent hydrocarbon groups containing no aliphatic unsaturated bonds, R 34 are each independently the same or different monovalent hydrocarbon groups containing no aliphatic unsaturated bonds, Y and Y' each represent an alkylene group having 2 or more carbon atoms, an alkyleneoxyalkylene group, or an oxygen atom; na is 0 or 1, nb is 1 or 2, and nc is 1 or 2, with the proviso that the sum of na, nb, and nc is 3; n1 to n4 each represent an integer of 0 or more; the sum of n1, n2, n3, and n4 represents an integer of 2 to 600; the sum of n3 and n4 represents an integer of 1 or more; and a represents an integer of 0 to 4. (Configuration 5) The electrophotographic photoreceptor according to any one of configurations 1 to 4, wherein the content of the structure having the dimethylsiloxane moiety in the polycarbonate resin (β) is 3% by mass or more and 20% by mass or less with respect to the total mass of the polycarbonate resin (β). (Configuration 6) 6. The electrophotographic photoreceptor according to any one of Configurations 1 to 5, wherein the content of the polycarbonate resin (β) in the surface layer is 5% by mass or more and 15% by mass or less based on the content of the polycarbonate resin (α). (Configuration 7) 7. The electrophotographic photoreceptor according to any one of Configurations 1 to 6, which has an undercoat layer containing a polyamide resin and titanium oxide particles. (Configuration 8) The electrophotographic photoreceptor according to any one of configurations 1 to 7, which has a charge generating layer containing oxytitanium phthalocyanine having a peak at a Bragg angle 2θ of 27.2°±0.2° in a CuKα characteristic X-ray diffraction spectrum. (Configuration 9) A process cartridge which integrally supports an electrophotographic photosensitive member and a developing means and is detachably mountable to a main body of an electrophotographic apparatus, The electrophotographic photoreceptor is an electrophotographic photoreceptor according to any one of Configurations 1 to 8, the developing means recovers transfer residual toner remaining on the electrophotographic photosensitive member after the toner image has been transferred from the electrophotographic photosensitive member to a transfer material; A process cartridge comprising: (Configuration 10) An electrophotographic apparatus having an electrophotographic photoreceptor, a charging unit, an exposure unit, a developing unit, and a transfer unit, The electrophotographic photoreceptor is an electrophotographic photoreceptor according to any one of Configurations 1 to 8, the developing means recovers transfer residual toner remaining on the electrophotographic photosensitive member after the toner image has been transferred from the electrophotographic photosensitive member to a transfer material; Electrophotographic apparatus characterized in that [Explanation of symbols]

[0061] 1. Electrophotographic photoreceptor 2-axis 3. Charging means 4 Exposure light 5. Developing method 6 Transfer Method 7 Transfer material 8 Fixing Method 9 Cleaning Method 10 Pre-exposure light 11 Process cartridge 12 Guidance means

Claims

1. An electrophotographic photoreceptor having a surface layer, The surface layer contains a polycarbonate resin (α) and a polycarbonate resin (β), The polycarbonate resin (α) has a structural unit represented by the following formula (A) and a structural unit represented by the following formula (B), The polycarbonate resin (β) has a structure having a dimethylsiloxane moiety.

1. An electrophotographic photoreceptor comprising: 【Chemistry 1】

2. The electrophotographic photoreceptor according to claim 1 , wherein the polycarbonate resin (α) further has a structural unit represented by the following formula (C): 【Chemistry 2】 (In formula (C), X １０１ represents a single bond or a divalent group, R １０１ ~R １０４ each independently represents a hydrogen atom, an alkyl group, or an aryl group.

3. in the polycarbonate resin (α), the total amount of the structural unit represented by the formula (A) and the structural unit represented by the formula (B) is 40 mol % or more and 60 mol % or less based on the total amount of the structural unit represented by the formula (A), the structural unit represented by the formula (B), and the structural unit represented by the formula (C); the amount of the structural unit represented by the formula (C) in the polycarbonate resin (α) is 40 mol % or more and 60 mol % or less based on the total amount of the structural unit represented by the formula (A), the structural unit represented by the formula (B), and the structural unit represented by the formula (C); The electrophotographic photoreceptor according to claim 2 .

4. 2. The electrophotographic photoreceptor according to claim 1, wherein the structure having a dimethylsiloxane moiety is a structure represented by the following formula (D) or (E): 【Chemistry 3】 (In formula (D), R ２１ and R ２２ each independently represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms; R ２３ is a methyl group, n1 is an integer from 2 to 4, and n2 is an integer from 1 to 600. 【Chemistry 4】 (In formula (E), R ３１ represents a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms; R ３２ is a methyl group, R ３３ are each independently the same or different monovalent hydrocarbon groups containing no aliphatic unsaturated bonds, R ３４ are each independently the same or different monovalent hydrocarbon groups containing no aliphatic unsaturated bonds, Y and Y' are an alkylene group having 2 or more carbon atoms, an alkyleneoxyalkylene group, or an oxygen atom, na is 0 or 1, nb is 1 or 2, and nc is 1 or 2, with the proviso that the sum of na, nb, and nc is 3, n1 to n4 are each an integer of 0 or more, the sum of n1, n2, n3, and n4 is an integer of 2 to 600, the sum of n3 and n4 is an integer of 1 or more, and a is an integer of 0 to 4.

5. 2. The electrophotographic photoreceptor according to claim 1, wherein the content of the structure having a dimethylsiloxane moiety in the polycarbonate resin (β) is 3% by mass or more and 20% by mass or less with respect to the total mass of the polycarbonate resin (β).

6. 2 . The electrophotographic photoreceptor according to claim 1 , wherein the content of the polycarbonate resin (β) in the surface layer is from 5% by mass to 15% by mass with respect to the content of the polycarbonate resin (α).

7. The electrophotographic photoreceptor according to claim 1 , further comprising an undercoat layer containing a polyamide resin and titanium oxide particles.

8. 2. The electrophotographic photoreceptor according to claim 1, which has a charge generating layer containing oxytitanium phthalocyanine having a peak at a Bragg angle 2θ of 27.2°±0.2° in a CuKα characteristic X-ray diffraction spectrum.

9. A process cartridge which integrally supports an electrophotographic photosensitive member and a developing means and is detachably mountable to a main body of an electrophotographic apparatus, The electrophotographic photoreceptor is the electrophotographic photoreceptor according to any one of claims 1 to 8, the developing means recovers transfer residual toner remaining on the electrophotographic photosensitive member after the toner image has been transferred from the electrophotographic photosensitive member to a transfer material; A process cartridge comprising:

10. An electrophotographic apparatus having an electrophotographic photoreceptor, a charging unit, an exposure unit, a developing unit, and a transfer unit, The electrophotographic photoreceptor is the electrophotographic photoreceptor according to any one of claims 1 to 8, the developing means recovers transfer residual toner remaining on the electrophotographic photosensitive member after the toner image has been transferred from the electrophotographic photosensitive member to a transfer material; Electrophotographic apparatus characterized in that

Images