Manufacturing method for electrophotographic photoreceptors

Abstract

The object of the present invention is to provide a method for manufacturing an electrophotographic photoreceptor that has excellent electrical properties and durability. [Solution] A method for manufacturing an electrophotographic photoreceptor having a photosensitive layer and a protective layer, to be used in an image forming apparatus having a positively charged charging means, comprising: step S12 of forming the photosensitive layer; and step S13 of forming the protective layer on the photosensitive layer. Step S13 of forming the protective layer is to set the wavelength of light irradiated by a UV (ultraviolet)-LED (Light Emitting Diode) device to 385-405 nm, and the peak irradiance on the photoreceptor to 1000 mW / cm². 2 The above and 5000 mW / cm² 2 The following light energy is used to form a protective layer.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing an electrophotographic photoreceptor. [Background technology]

[0002] In recent years, there has been a demand for long-life electrophotographic photoreceptors (hereinafter referred to as "photoreceptors" as appropriate) from the perspectives of environmental friendliness and cost. To extend the lifespan of a photoreceptor, it is necessary to reduce the amount of wear on the photoreceptor during durability testing and to suppress the rise in residual potential. To address these challenges, methods have been proposed, such as those described in Patent Documents 1 and 2, in which a protective layer is formed on the charge transport layer of a photoreceptor by irradiating it with light to polymerize polymerizable compounds in the uncured film and cure it.

[0003] However, Patent Document 1 specifies that in forming the protective layer, a UV (ultraviolet)-LED (Light Emitting Diode) light source should be used, with the wavelength of light in the range of 360 to 405 nm. Furthermore, wavelengths shorter than 385 nm are included, and the irradiance is set to a maximum of 25,000 mW / cm². 2 Therefore, the outermost protective layer dries faster than the interior, making it easier for solvent to remain during curing and inhibiting the reaction of photopolymerizable compounds. As a result, the initial Vi potential of the photoreceptor after exposure becomes high, leading to deterioration of electrical properties such as electrostatic properties due to repeated copying processes, and a decrease in wear during durability, making it impossible to ensure durability.

[0004] In Patent Document 2, when forming the protective layer, the light source is a xenon lamp, resulting in greater heat generation than a UV-LED light source. Therefore, the outermost film of the protective layer dries faster than the interior, making it easier for solvent to remain during curing and inhibiting the reaction of the photopolymerizable compound. As a result, the initial Vi potential of the photoreceptor after exposure becomes high, leading to deterioration of electrical properties such as electrostatic properties due to repeated copying processes, and a decrease in wear during durability, making it impossible to ensure durability. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-74262 [Patent Document 2] Japanese Patent Publication No. 2014-77898 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The object of this invention is to provide a method for manufacturing an electrophotographic photoreceptor that has excellent electrical properties and durability. [Means for solving the problem]

[0007] The above-mentioned problems according to the present invention are solved by the following means.

[0008] (1) A method for manufacturing an electrophotographic photoreceptor having a photosensitive layer and a protective layer, to be used in an image forming apparatus having a positively charged charging means, comprising the steps of forming a photosensitive layer and forming a protective layer on the photosensitive layer, wherein the step of forming the protective layer is to use a UV (ultraviolet)-LED (Light Emitting Diode) device with a wavelength of light irradiated at 385 to 405 nm and a peak irradiance on the photoreceptor at 1000 mW / cm². 2 The above and 5000 mW / cm² 2 A method for manufacturing an electrophotographic photoreceptor, characterized by forming the protective layer by irradiating it with the following light energy.

[0009] (2) The method for manufacturing an electrophotographic photoreceptor according to (1), characterized in that the thickness of the protective layer is 2 to 5 μm.

[0010] (3) The method for manufacturing an electrophotographic photoreceptor according to (1) or (2), characterized in that the protective layer contains metal oxide particles.

[0011] (4) The method for manufacturing an electrophotographic photoreceptor according to (3), characterized in that the metal oxide particles are tin oxide.

Advantages of the Invention

[0012] According to the present invention, an electrophotographic photoreceptor excellent in electrical characteristics and durability can be provided.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic diagram showing an example of the electrophotographic photoreceptor of the embodiment. [Figure 2] It is a flowchart showing a method for manufacturing the electrophotographic photoreceptor of the embodiment. [Figure 3] It is a schematic diagram explaining an outline of a wear test by a wear tester.

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments of the present invention are not limited to the embodiments described below. In addition, dimensions, materials, shapes, relative arrangements, components, etc. of the components described in the embodiments are not intended to limit the scope of the present invention only thereto without specific description, but are merely examples. Note that the sizes and positional relationships of the members shown in each drawing may be exaggerated or simplified for clarity of explanation. In addition, in order to avoid excessive complexity of the drawings, illustration of some elements may be omitted. In the following description, "~" is used to mean including the numerical values described before and after it as lower and upper limits.

[0015] [Electrophotographic Photoreceptor] The electrophotographic photoreceptor (hereinafter, appropriately referred to as the photoreceptor) is used in an image forming apparatus having a positive charging means for charging the surface of the photoreceptor to a positive potential. As the positive charging means for charging the surface of the photoreceptor to a positive potential, generally known charging means can be applied. For example, charging means such as corotron charging using corona discharge and roller charging can be applied.

[0016] The photoreceptor is an organic photoreceptor, meaning an electrophotographic photoreceptor in which at least one of the charge generation function and charge transport function, which are essential for the structure of an electrophotographic photoreceptor, is expressed by an organic compound. The electrophotographic photoreceptor includes photoreceptors composed of known organic charge generation substances or organic charge transport substances, and photoreceptors in which the charge generation function and charge transport function are composed of polymer complexes.

[0017] As shown in Figure 1, the electrophotographic photoreceptor 10 has an intermediate layer 2 disposed on a conductive support 1, a photosensitive layer 3 disposed on the intermediate layer 2, and a protective layer 4 disposed on the photosensitive layer 3. Details of these will be explained in the method for manufacturing the electrophotographic photoreceptor.

[0018] [Manufacturing method for electrophotographic photoreceptors] The method for manufacturing an electrophotographic photoreceptor is used in an image forming apparatus having a positively charged charging means, and is a method for manufacturing an electrophotographic photoreceptor having a photosensitive layer and a protective layer. The method for manufacturing an electrophotographic photoreceptor comprises the steps of forming a photosensitive layer and forming a protective layer on the photosensitive layer.

[0019] As shown in Figure 2, the method for manufacturing an electrophotographic photoreceptor according to this embodiment will be described as including an intermediate layer formation step S11, a photosensitive layer formation step S12, and a protective layer formation step S13.

[0020] (Intermediate layer formation process) The intermediate layer formation step S11 is a step in which an intermediate layer (undercoat layer) is formed on a conductive support.

[0021] The conductive support used in this embodiment may be any material that is conductive. Examples of conductive supports include metals such as aluminum, copper, chromium, nickel, zinc, and stainless steel formed into drums or sheets; metal foils such as aluminum or copper laminated onto a plastic film; aluminum, indium oxide, and tin oxide vapor-deposited onto a plastic film; and metals, plastic films, and paper coated with a conductive material alone or together with a binder resin to form a conductive layer.

[0022] The intermediate layer is positioned between the conductive support and the photosensitive layer and has barrier and adhesive functions. The intermediate layer may be provided as needed, and the photosensitive layer may be placed directly on the conductive support.

[0023] The intermediate layer can be formed by dissolving binder resins such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane, and gelatin in a known solvent and applying them by immersion coating or the like. Among these, alcohol-soluble polyamide resins are preferred.

[0024] Furthermore, various conductive fine particles and metal oxides can be included to adjust the resistance of the intermediate layer. For example, various metal oxides such as alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, and bismuth oxide, as well as ultrafine particles such as tin-doped indium oxide, antimony-doped tin oxide, and zirconium oxide can be used.

[0025] These metal oxides may be used individually or in combination of two or more. When two or more are mixed, they may take the form of a solid solution or fusion. The average particle size of such metal oxides is preferably 0.3 μm or less, more preferably 0.1 μm or less.

[0026] As the solvent used for the intermediate layer, it is preferable to use one that disperses inorganic particles well and dissolves the polyamide resin. Specifically, C2-C4 alcohols such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, and sec-butanol are preferred because they have excellent solubility and coating performance for the polyamide resin. In addition, as cosolvents that can be used in combination with the above solvent to improve storage properties and particle dispersibility and obtain desirable effects, methanol, benzyl alcohol, toluene, methylene chloride, cyclohexanone, and tetrahydrofuran are examples of such solvents.

[0027] The concentration of the binder resin is appropriately selected according to the film thickness of the intermediate layer and the production speed. When inorganic particles are dispersed, the mixing ratio of inorganic particles to the binder resin is preferably 20 to 400 parts by mass of inorganic particles per 100 parts by mass of binder resin, and more preferably 50 to 200 parts by mass of inorganic particles. As means of dispersing inorganic particles, ultrasonic dispersers, ball mills, sand grinders, and homomixers can be used, but are not limited to these.

[0028] The intermediate layer can be coated using known methods such as immersion coating, spray coating, spinner coating, bead coating, blade coating, beam coating, or slide hopper coating. The drying method for the intermediate layer can be appropriately selected depending on the type of solvent and film thickness, but heat drying is preferred. The film thickness of the intermediate layer is preferably 0.1 to 15 μm, and more preferably 0.3 to 10 μm.

[0029] (Photosensitive layer formation process) The photosensitive layer formation step S12 is a step in which a photosensitive layer is formed on the intermediate layer.

[0030] The photosensitive layer has both the function of absorbing light and generating electric charge, and the function of transporting electric charge. The photosensitive layer may have a single-layer structure containing a charge-generating material and a charge-transporting material, provided that a protective layer is present on the outermost surface, or it may have a laminated structure consisting of a charge-generating layer containing a charge-generating material and a charge-transporting layer containing a charge-transporting material. The photosensitive layer in this embodiment is a single-layer photosensitive layer having positive charge properties, containing a charge-generating material and a hole-transporting charge-transporting material.

[0031] A single-layer photosensitive layer is essentially a single photosensitive layer in which both charge generation and charge transport functions are achieved. The following describes the charge transport materials and other materials used in single-layer photosensitive layers.

[0032] (Charge-generating material) As the charge-generating material, known charge-generating materials can be used. Preferably, examples include phthalocyanine pigments, polycyclic quinone pigments, perylene-based pigments, and bis-azo pigments. As phthalocyanine-based pigments, titanyl phthalocyanine, metal-free phthalocyanine, vanadium phthalocyanine, oxotitanium phthalocyanine, and gallium phthalocyanine are preferably used.

[0033] (charge transport material) It is preferable to use a combination of hole-transporting and electron-transporting charge-transporting materials as the charge-transporting material.

[0034] As hole-transporting charge-transporting substances, carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolon derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, and poly-9-vinylanthracene, triphenylamine derivatives, etc., can be used, and two or more of these may be used in combination.

[0035] On the other hand, electron-transporting charge transport materials (electron-transporting compounds) that can be used include 2-nitro-9-fluorenone, 2,7-dinitro-9-fluorenone, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2-nitrobenzothiophene, 2,4,8-trinitrothioxanthone, dinitroanthracene, dinitroacridine, dinitroanthraquinone, naphthoquinones, and 3,5-dimethyl-3',5'-di-t-butyldiphenoquinone.

[0036] (binder) Various resins can be used as binder resins to disperse charge generating agents and charge transporting agents. For example, various polymers can be exemplified, such as styrene polymers, acrylic polymers, styrene-acrylic polymers, ethylene-vinyl acetate copolymers, polypropylene, olefin polymers such as ionomers, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyesters, alkyd resins, polyamides, polyurethanes, epoxy resins, polycarbonates, polyarylates, polysulfones, diallyl phthalate resins, silicone resins, ketone resins, polyvinyl butyral resins, polyether resins, phenolic resins, and photocurable resins such as epoxy acrylates. These binder resins can be used individually or in mixtures of two or more. Preferred resins include styrene polymers, acrylic polymers, styrene-acrylic polymers, polyester resins, alkyd resins, polycarbonates, and polyarylates.

[0037] In a single-layer photoreceptor, the charge generating agent is blended in a ratio of 0.1 to 50 parts by mass, preferably 0.5 to 30 parts by mass, per 100 parts by mass of the binder resin, and the electron transporter is blended in a ratio of 5 to 100 parts by mass, preferably 10 to 80 parts by mass. In addition, the hole transporter is blended in a ratio of 5 to 500 parts by mass, preferably 25 to 200 parts by mass. Furthermore, the total amount of the hole transporter and electron transporter is appropriately 20 to 500 parts by mass, preferably 30 to 200 parts by mass, per 100 parts by mass of the binder resin. When an electron-accepting compound is included in the single-layer photoreceptor layer, it is appropriate to blend the electron-accepting compound in a ratio of 0.1 to 40 parts by mass, preferably 0.5 to 20 parts by mass, per 100 parts by mass of the binder resin.

[0038] In the case of a single-layer photoreceptor, the thickness of the photosensitive layer is generally 5 to 100 μm, and particularly 10 to 50 μm, which is preferable in terms of electrophotographic characteristics.

[0039] In this embodiment, polymerizable compounds refer to compounds that, when polymer formation reactions are broadly divided into chain polymerization and stepwise polymerization, have unsaturated polymerizable functional groups, ring-opening polymerizable functional groups, or isomerizing polymerizable functional groups that promote chain polymerization. On the other hand, in the latter stepwise polymerization reaction, they refer to compounds that have hydroxyl groups that can promote condensation reactions, or organosilicon compounds that have hydrolyzable groups.

[0040] Known methods such as immersion coating, spray coating, spinner coating, bead coating, blade coating, beam coating, and slide hopper coating can be used for applying the photosensitive layer.

[0041] (Protective layer formation process) The protective layer formation step S13 is a step in which a protective layer is formed on the photosensitive layer. The purpose of the protective layer is to improve the durability of the photoreceptor, and for this reason, a cured film formed from a polymer of a polymerizable compound is selected.

[0042] The protective layer is formed by polymerizing a polymerizable compound. Suitable polymerizable compounds include monomers that polymerize (cure) upon irradiation with active rays such as ultraviolet light to form resins commonly used as binder resins for photoreceptors, such as polystyrene and polyacrylate. Particularly preferred polymerizable compounds are styrene monomers, acrylic monomers, methacrylic monomers, vinyltoluene monomers, vinyl acetate monomers, and N-vinylpyrrolidone monomers.

[0043] In particular, curable compounds having an acryloyl group (CH2=CHCO-) ​​or a methacryloyl group (CH2=CCH3CO-) that can polymerize (cur) with low light intensity or short time and form an electrically neutral resin are preferred. In this embodiment, these polymerizable compounds may be used individually or in combination.

[0044] Furthermore, cationic polymerizable compounds include epoxy compounds, vinyl ether compounds, and oxetane compounds, but oxetane compounds are preferred.

[0045] Examples of polymerizable compounds include the exemplary compounds described in Japanese Patent Publication No. 2011-242574. Specific examples of preferred oxetane compounds include the oxetane compounds described in Japanese Patent Publication No. 2011-242574. Examples of epoxy compounds include aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

[0046] In this embodiment, it is preferable to use a polymerizable compound having three or more functional groups (reactive groups). Furthermore, two or more polymerizable compounds may be used in combination, but even in this case, it is preferable to use a polymerizable compound having three or more functional groups in an amount of 50% by mass or more.

[0047] The protective layer preferably contains metal oxide particles. The durability of the protective layer is improved by incorporating metal oxide particles and forming a nanocomposite. Generally known materials can be used as the metal oxide particles. Examples of metal oxide particles include silica (silicon oxide), magnesium oxide, zinc oxide, lead oxide, aluminum oxide, tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, tin oxide, titanium oxide, niobium oxide, molybdenum oxide, and vanadium oxide. Among these, tin oxide is preferred because of its excellent uniform dispersion within the protective layer film.

[0048] The metal oxide particles are preferably produced by known methods, such as general manufacturing methods including gas phase, chlorine, sulfuric acid, plasma, and electrolytic methods. The number-mean primary particle size of the metal oxide is preferably in the range of 1 to 300 nm, and particularly preferably 3 to 100 nm. The number-mean primary particle size of the metal oxide particles can be calculated by taking a 10,000x magnified photograph using a scanning electron microscope (JEOL Ltd.), and then scanning 300 randomly selected particles (excluding aggregated particles) to obtain the photographic image, which can then be used with the LUZEX AP (Nireco Corporation) automated image processing and analysis system software version 1.32.

[0049] It is preferable to use metal oxide particles whose surfaces have been surface-treated with a polymerizable compound having a surface treatment group. That is, metal oxide particles surface-treated with a polymerizable compound having a surface treatment group can be obtained by reacting a chain polymerizable compound having a surface treatment group with metal oxide particles having hydroxyl groups on their surface. Generally, metal oxide particles that have not undergone surface treatment have hydroxyl groups on their surface. Examples of chain polymerizable compounds having surface treatment groups include the exemplary compounds described in Japanese Patent Publication No. 2011-242574.

[0050] When polymerizable compounds are reacted, a method is used in which a radical polymerization initiator or a cationic polymerization initiator is added and the reaction is induced by light. A photopolymerization initiator can be used as the polymerization initiator.

[0051] As radical polymerization initiators for these photocurable compounds, photopolymerization initiators are preferred, and among them, alkylphenone compounds or phosphine oxide compounds are preferred. In particular, compounds having an α-hydroxyacetophenone structure or an acylphosphine oxide structure are preferred. Furthermore, as compounds that initiate cationic polymerization, for example, B(C6F5)4 aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, and phosphonium are preferred. - PF6 - AsF6 - SbF6- CF3SO3 - Examples of nonionic polymerization initiators include ionic polymerization initiators such as salts, sulfonates that generate sulfonic acid, halides that generate hydrogen halides, and nonionic polymerization initiators such as iron allene complexes. In particular, nonionic polymerization initiators such as sulfonates that generate sulfonic acid and halides that generate hydrogen halides are preferred. Examples of photopolymerization initiators include the exemplary compounds described in Japanese Patent Publication No. 2011-242574.

[0052] Examples of solvents for forming a protective layer include, but are not limited to, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol, benzyl alcohol, toluene, xylene, methylene chloride, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine.

[0053] The following method is preferred for polymerizing polymerizable compounds to form a protective layer. First, a protective layer coating solution (a composition containing polymerizable compounds or surface-treated metal oxide particles, etc.) is applied to the photosensitive layer. Then, after primary drying until the coating film loses its fluidity, the protective layer is cured by irradiation with an active ray such as ultraviolet light. Furthermore, secondary drying is performed to bring the amount of volatile substances in the coating film to a specified level.

[0054] The coating method can be any known method such as immersion coating, spray coating, spinner coating, bead coating, blade coating, beam coating, or slide hopper coating.

[0055] After the protective layer is applied, it is preferably allowed to dry naturally or by heat drying and then irradiated with actinic rays to cause a reaction. In the photoreceptor of the present invention, it is preferable that the coating film is irradiated with actinic rays to generate radicals and polymerize, and cross-linking bonds are formed by cross-linking reactions between and within molecules to cure and produce a cured resin. As the actinic rays, for example, ultraviolet rays are used. As described later, the actinic rays may be light up to 405 nm exceeding the upper limit of general ultraviolet rays.

[0056] As a device for irradiating ultraviolet rays or the like, a UV-LED device is used. And in the protective layer forming step S13, the wavelength of the light irradiated by the UV-LED device is set to 385 to 405 nm, and the peak irradiance on the photoreceptor is 1000 mW / cm 2 or more and 5000 mW / cm 2 or less of light energy is irradiated to form a protective layer. Here, the "photoreceptor" means the photoreceptor before the protective layer is cured by irradiating light energy.

[0057] In a method for manufacturing an electrophotographic photoreceptor provided with a photosensitive layer and a protective layer on a conductive substrate, when an ultraviolet lamp is used for irradiating light energy during the formation of the protective layer, the polymerizable compound deteriorates due to the light energy during light irradiation. It is known that this causes variations in the electrical characteristics and wear characteristics of the electrophotographic photoreceptor.

[0058] In an ultraviolet lamp, heat is generated during curing, so the film on the outermost surface of the protective layer dries faster than the inside, so that the solvent tends to remain during curing, inhibiting the reaction of the photopolymerizable compound and deteriorating the charge generating substance near the surface of the photosensitive layer. As a result, the initial Vi of the photoreceptor becomes high, and deterioration of electrical characteristics such as electrostatic characteristics due to repeated copying processes and deterioration of the wear amount in durability occur, and durability cannot be ensured. Therefore, in this embodiment, a UV-LED device considering the environment is used in the formation of the protective layer. Furthermore, the light irradiated by the UV-LED device has a wavelength of 385 to 405 nm that does not use the short-wavelength side wavelength where heat is generated, and the peak irradiance on the photoreceptor is "1000 mW / cm 2The above and 5000 mW / cm² 2 The protective layer is cured by irradiating it with the following light energy. This suppresses heat generation, and by drying and curing from the inside of the protective layer, the solvent can be easily removed, thus avoiding reaction inhibition of photopolymerizable compounds during curing and degradation of charge-generating materials near the surface of the photosensitive layer. As a result, it is possible to significantly reduce the initial Vi, which was a challenge until now, and we have been able to develop an electrophotographic photoreceptor that has excellent electrical properties such as electrostatic properties even after repeated copying processes, and ensures durability by stabilizing the amount of wear in terms of durability.

[0059] If the wavelength of light emitted by the UV-LED device is less than 385 nm, the solvent does not evaporate easily, leading to inhibition of the reaction during curing of the photopolymerizable compound and deterioration of the charge-generating material near the surface of the photosensitive layer. This deteriorates the electrical properties and durability of the photoreceptor. Therefore, the wavelength of light emitted by the UV-LED device should be 385 nm or higher. From the viewpoint of further improving the electrical properties and durability of the photoreceptor, the wavelength of light emitted by the UV-LED device is preferably 387 nm or higher, more preferably 390 nm or higher, and even more preferably 392 nm or higher. On the other hand, since the wavelength of light emitted by the UV-LED device is generally 405 nm or lower, the wavelength of light emitted by the UV-LED device should be 405 nm or lower. The wavelength of light emitted by the UV-LED device is preferably 402 nm or lower, more preferably 400 nm or lower.

[0060] Furthermore, at the peak irradiance of the UV-LED device, the peak irradiance on the photoreceptor is 1000 mW / cm². 2 Below this level, the solvent does not evaporate easily, leading to inhibition of the reaction during curing of photopolymerizable compounds and degradation of charge-generating materials near the surface of the photosensitive layer. This degrades the electrical properties and durability of the photoreceptor. Furthermore, if the peak irradiance on the photoreceptor is 5000 mW / cm², 2 If the irradiance exceeds 5500 mW / cm², the solvent becomes difficult to evaporate, leading to inhibition of the reaction during curing of photopolymerizable compounds and degradation of charge-generating materials near the surface of the photosensitive layer. This results in a deterioration of the electrical properties and durability of the photoreceptor. 2At this level, durability may not deteriorate significantly, but electrical properties will degrade. Therefore, if the peak irradiance on the photoreceptor is "1000 mW / cm²", 2 The above and 5000 mW / cm² 2 The following light energy shall be irradiated.

[0061] From the viewpoint of further improving the electrical characteristics and durability of the photoreceptor, the peak irradiance on the photoreceptor is preferably 1500 mW / cm². 2 More preferably, 2000 mW / cm² 2 More preferably 2500 mW / cm² 2 That concludes the explanation. Furthermore, from the viewpoint of further improving the electrical characteristics and durability of the photoreceptor, the peak irradiance on the photoreceptor is preferably 4500 mW / cm². 2 More preferably, 4000 mW / cm² 2 More preferably, 3500 mW / cm² 2 The following applies:

[0062] These polymerization initiators may be used individually or in a mixture of two or more. The content of the polymerization initiator is 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass, per 100 parts by mass of the polymerizable compound.

[0063] Furthermore, the protective layer of the present invention may also contain various charge transport substances and antioxidants, and various lubricant particles may be added. For example, fluorine atom-containing resin particles may be added. As the fluorine atom-containing resin particles, it is preferable to appropriately select one or more from tetrafluoroethylene resin, trifluoroethylene chloride resin, hexafluoroethylene chloride propylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluoroethylene chloride resin, and copolymers thereof, but tetrafluoroethylene resin and vinylidene fluoride resin are particularly preferred. The proportion of lubricant particles in the protective layer is preferably 5 to 70 parts by mass, more preferably 10 to 60% by mass, per 100 parts by mass of polymerizable compound. The particle size of the lubricant particles is preferably such that the average primary particle size is 0.01 to 1 μm. Particularly preferred is a particle size of 0.05 to 0.5 μm. The molecular weight of the resin can be appropriately selected and is not particularly limited.

[0064] The thickness of the protective layer is preferably 2 to 5 μm. Within this range, the durability of the protective layer is improved, and the impact on electrical properties during curing is minimized. From the viewpoint of further improving these effects, a protective layer thickness of 3 μm or more is more preferable. Furthermore, from the viewpoint of further improving these effects, a protective layer thickness of 4 μm or less is more preferable. [Examples]

[0065] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following text, "part" refers to "parts by mass". Positively charged photoreceptors were prepared by the following method. In Table 1, Nos. 1 to 10 are examples that satisfy the scope of the present invention, and Nos. 11 to 15 are comparative examples that do not satisfy the scope of the present invention.

[0066] [No.1] Photoreceptor No. 1 was prepared as shown below. A PET film support coated with aluminum was prepared.

[0067] <Middle class> An intermediate layer coating solution with the following composition was prepared. Polyamide resin X1010 (manufactured by Daicel Degussa Co., Ltd.) 1 piece Titanium dioxide SMT500SAS (manufactured by Teika Co., Ltd.) 1.1 part Ethanol 20 parts A sand mill was used as a disperser, and the dispersion was performed in a batch manner for 10 hours. Using the above coating solution, an intermediate layer was formed on the support by applying it with a wire bar to a film thickness of 2 μm after drying at 110°C for 20 minutes.

[0068] <Photosensitive layer> Charge-generating material: Titanyl phthalocyanine pigment (titanium phthalocyanine pigment having the maximum diffraction peak at at least 27.3° in Cu-Kα characteristic X-ray diffraction spectrum measurement) 10 parts Hole-transporting charge-transporting material: CTM (see CTM-A below) 100 copies Electron transport compound: CTM (compound H below) 50 parts Binder: Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Co., Ltd.) 200 copies Antioxidant (Irganox 1010: manufactured by Ciba Japan Co., Ltd.) 6 parts Toluene / tetrahydrofuran = 1 / 4 volume % 1600 parts Silicone oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part These were mixed and dispersed in a ball mill for 50 hours to prepare a coating solution for the photosensitive layer. This coating solution was then applied to the intermediate layer using a doctor blade to form a photosensitive layer with a thickness of 20 μm after drying at 110°C for 60 minutes.

[0069] <Protective layer> A protective layer coating solution was prepared by dissolving and dispersing the following composition. Metal oxide fine particles (tin oxide with an average primary particle size of 30 nm) 100 parts by mass Polymerizable compound (example compound Mc-31 below) 100 parts by mass Polymerization initiator (example compounds 1-6 below): 15 parts by mass Antioxidant (Irganox 1010: manufactured by Ciba Japan Co., Ltd.) 6 parts 2-Butyl alcohol 100 parts by mass This protective layer coating solution was applied onto the charge transport layer using a wire bar to form a protective layer. The protective layer was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 385 nm at an irradiance of 1000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 2 μm. This completed the fabrication of photoreceptor No. 1.

[0070] [ka]

[0071] The Mc group number (methacryloyl group number) represents the number of methacryloyl groups. The hydrogen atom in the electron-transporting compound is 3,5-dimethyl3′,5′-di-(t)butyldiphenoquinone.

[0072] [No.2] Photoreceptor No. 2 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 395 nm at an irradiance of 1000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 2 μm. This created photoreceptor No. 2.

[0073] [No.3] Photoreceptor No. 3 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 405 nm at an irradiance of 1000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 2 μm. This completed the fabrication of photoreceptor No. 3.

[0074] [No.4] Photoreceptor No. 4 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 385 nm at an irradiance of 3000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 4 μm. This completed the fabrication of photoreceptor No. 4.

[0075] [No.5] Photoreceptor No. 5 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 395 nm at an irradiance of 3000 mW / cm². 2 The material was then irradiated for 20 seconds to form a protective layer with a dry thickness of 4 μm. This completed the fabrication of photoreceptor No. 5.

[0076] [No.6] Photoreceptor No. 6 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 405 nm at an irradiance of 3000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry film thickness of 4 μm. This completed the fabrication of photoreceptor No. 6.

[0077] [No.7] Photoreceptor No. 7 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 385 nm at an irradiance of 5000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 5 μm. This completed the fabrication of photoreceptor No. 7.

[0078] [No.8] Photoreceptor No. 8 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 395 nm at an irradiance of 5000 mW / cm². 2The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 5 μm. This completed the fabrication of photoreceptor No. 8.

[0079] [No.9] Photoreceptor No. 9 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 405 nm at an irradiance of 5000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 5 μm. This completed the fabrication of photoreceptor No. 9.

[0080] [No.10] Photoreceptor No. 10 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 385 nm at an irradiance of 3000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 6 μm. This completed the fabrication of photoreceptor No. 10.

[0081] [No.11] Photoreceptor No. 11 was prepared as shown below. The protective layer of photoreceptor No. 1 was subjected to a nitrogen atmosphere using an ultraviolet lamp (xenon lamp) at a distance of 10 mm from the light source to the surface of the photoreceptor, with an irradiance of 5000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 4 μm. This completed the fabrication of photoreceptor No. 11.

[0082] [No.12] Photoreceptor No. 12 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 385 nm at an irradiance of 500 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 4 μm. This completed the fabrication of photoreceptor No. 12.

[0083] [No.13] Photoreceptor No. 13 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 385 nm at an irradiance of 7000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 4 μm. This resulted in the fabrication of photoreceptor No. 13.

[0084] [No.14] Photoreceptor No. 14 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 365 nm at an irradiance of 5000 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 4 μm. This completed the fabrication of photoreceptor No. 14.

[0085] [No.15] Photoreceptor No. 15 was prepared as shown below. The protective layer of photoreceptor No. 1 was cured using a UV-LED curing device under a nitrogen atmosphere, with the distance from the light source to the photoreceptor surface set to 10 mm, and irradiated with light of a wavelength of 385 nm at an irradiance of 5500 mW / cm². 2 The material was irradiated for 20 seconds to form a protective layer with a dry thickness of 4 μm. This resulted in the fabrication of photoreceptor No. 15. The fabricated photoreceptor was evaluated based on the following criteria.

[0086] (Electrical characteristics) The electrical properties of the fabricated positively charged photoreceptor were investigated, specifically focusing on Vi. The fabricated positively charged photoreceptor was charged to a surface potential of +800V (V0) using a charging test device EPA-8200 (manufactured by Kawaguchi Electric Works), and left in that state for 3 seconds. After that, a monochromatic light of 780nm at 1 μJ / cm² was applied. 2 The surface was irradiated with light at a specific intensity for 3 seconds to allow light attenuation. The light intensity at which the surface potential was halved was defined as the sensitivity (Vi). After standing for 5 seconds, the surface was irradiated with 5 lux white light for 3 seconds, and the residual potential (Vr) was measured.

[0087] Devices with a Vi of 70V or less were given an "A" rating, indicating excellent electrical characteristics. Devices with a Vi between 70V and 80V were given a "B" rating, indicating good electrical characteristics. Devices with a Vi between 80V and 90V were given a "C" rating, indicating slightly inferior electrical characteristics. Devices with a Vi above 90V were given a "D" rating, indicating poor electrical characteristics. Devices with an "A" or "B" rating passed, while those with a "C" or "D" rating failed.

[0088] (durability) The amount of wear on the fabricated positively charged photoreceptor was measured using a Taber abrasion tester. The fabricated positively charged photoreceptor was subjected to 10,000 counts using a rotary abrasion tester (manufactured by Toyo Seiki) with a load of 9.8N, a rotation speed of 60rpm, and a CS-17 abrasion wheel. The amount of wear was calculated as "START weight - weight after 10,000 counts = amount of wear". As shown in Figure 3, the abrasion testing machine abrades the test piece 20 by rotating the abrasion wheel 30 placed on the test piece 20 in the direction of the arrow, while simultaneously rotating the test piece 20 in the direction of the arrow. The outer diameter D of the abrasion area is approximately 88 mm.

[0089] Materials with an abrasion amount of 0.1 mg or less were rated "A" for excellent durability. Materials with an abrasion amount between 0.1 mg and 0.2 mg were rated "B" for good durability. Materials with an abrasion amount between 0.2 mg and 0.4 mg were rated "C" for slightly poor durability. Materials with an abrasion amount exceeding 0.4 mg were rated "D" for poor durability. Materials rated "A" and "B" were considered pass, while materials rated "C" and "D" were considered fail. These results are shown in Table 1. In Table 1, values ​​that cannot be determined are indicated with "-".

[0090] [Table 1]

[0091] As shown in Table 1, photoreceptors No. 1 to 10 passed the electrical characteristics and durability tests. No. 11 failed the electrical performance and durability test because it used an ultraviolet lamp as its light source. No. 12 failed the electrical performance and durability test because its peak irradiance was too low. No. 13 failed the electrical performance and durability test because its peak irradiance was too high. No. 14 failed the electrical performance and durability test because its wavelength was too low. No. 15 failed the electrical performance test because its peak irradiance was too high.

[0092] Although the embodiments for carrying out the invention have been described in more detail above, the spirit of the present invention is not limited to these descriptions and must be interpreted broadly based on the claims. Furthermore, various modifications and alterations based on these descriptions are also included in the spirit of the present invention. For example, the method for manufacturing an electrophotographic photoreceptor may include other steps between or before / after each of the aforementioned steps (S11 to S13), as long as these steps do not adversely affect the aforementioned steps. For example, it may include a step to remove foreign matter that has been introduced during the manufacturing process. [Explanation of Symbols]

[0093] 1. Conductive support 2. Middle class 3 Photosensitive layer 4 protective layer 10 Electrophotographic photoreceptor 20 test specimens 30 Wear wheels D Outer diameter

Claims

1. A method for manufacturing an electrophotographic photoreceptor having a photosensitive layer and a protective layer, used in an image forming apparatus having a positively charged charging means, The process of forming a photosensitive layer, The process includes forming a protective layer on the photosensitive layer, The process of forming the protective layer involves setting the wavelength of light irradiated by the UV (ultraviolet)-LED (Light Emitting Diode) device to 385-405 nm, and the peak irradiance on the photoreceptor to 1000 mW / cm². ２ The above and 5000 mW / cm² ２ A method for manufacturing an electrophotographic photoreceptor, characterized by forming the protective layer by irradiating it with the following light energy.

2. The method for manufacturing an electrophotographic photoreceptor according to claim 1, characterized in that the thickness of the protective layer is 2 to 5 μm.

3. A method for manufacturing an electrophotographic photoreceptor according to claim 1 or 2, characterized in that the protective layer contains metal oxide particles.

4. The method for producing an electrophotographic photoreceptor according to claim 3, characterized in that the metal oxide particles are tin oxide.

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