Electrophotographic photosensitive components, processing boxes, and electrophotographic equipment

Abstract

This invention relates to an electrophotographic photosensitive element, a processing cartridge, and an electrophotographic apparatus. An electrophotographic photosensitive element capable of maintaining its electrical charge during repeated use is provided. The electrophotographic photosensitive element sequentially comprises a support, a conductive layer, a photosensitive layer, and a protective layer, wherein the protective layer comprises an adhesive resin and metal oxide particles, the metal oxide particles having a core and a coating layer, the core and the coating layer each comprising titanium oxide, and the coating layer further comprising niobium.

Description

Technical Field

[0001] This invention relates to an electrophotographic photosensitive element, a processing box having an electrophotographic photosensitive element, and an electrophotographic apparatus. Background Technology

[0002] In electrophotographic photosensitive components used in electrophotographic devices, a protective layer is known to be provided to improve mechanical durability (wear resistance) in order to extend the life of the electrophotographic photosensitive component and improve image quality during repeated use.

[0003] In Japanese Patent Application Publication No. 2009-229495, it is known to add titanium oxide to the protective layer in order to improve the electrical properties of an electrophotographic photosensitive component using such a protective layer. Summary of the Invention

[0004] According to the inventor's research, there is room for improvement in the ability of the electrophotographic photosensitive component described in Japanese Patent Application Publication No. 2009-229495 to maintain its charge-carrying capacity during repeated use.

[0005] Therefore, one object of the present invention is to provide an electrophotographic photosensitive component capable of maintaining its charge-carrying capacity during repeated use.

[0006] The above objectives are achieved through the following invention.

[0007] That is, the first aspect of the present invention is an electrophotographic photosensitive component, which sequentially includes a support, a conductive layer, a photosensitive layer and a protective layer, wherein the protective layer comprises an adhesive resin and metal oxide particles, the metal oxide particles comprise a core and a coating layer covering the core, the core comprises titanium oxide, the coating layer comprises titanium oxide and niobium, and the niobium content based on the total mass of the coating layer is higher than the niobium content based on the total mass of the core.

[0008] A second aspect of the present invention is an electrophotographic photosensitive component comprising, in sequence, a support, a conductive layer, a photosensitive layer and a protective layer, wherein the protective layer comprises an adhesive resin and metal oxide particles, the metal oxide particles comprising a core and a coating layer covering the core, the core comprising titanium oxide, the coating layer comprising titanium oxide, and satisfying the following equations (1) and (2) when the oxygen deficiency rate of the metal oxide particles is represented by A (%), the oxygen deficiency rate of the core is represented by B (%) and the oxygen deficiency rate of the coating layer is represented by C (%).

[0009] A≤2.0 (1)

[0010] 10×B <C (2)

[0011] According to the first and second aspects of the present invention, an electrophotographic photosensitive component with good charge-carrying capacity can be provided.

[0012] Further features of the invention will become apparent from the following description of exemplary embodiments, with reference to the accompanying drawings. Attached Figure Description

[0013] Figure 1 It is a schematic structural diagram of an electrophotographic device including a processing box with an electrophotographic photosensitive element. Detailed Implementation

[0014] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0015] As a result of the research, the inventors found that there is room for improvement in maintaining charge-carrying capacity during repeated use of photosensitive components comprising titanium oxide particles used in the prior art and added to a protective layer.

[0016] When research was conducted in order to solve the technical problems that have arisen in the prior art, it was found that, as described in the first aspect of the present invention, the technical problem can be solved by including titanium oxide particles in the core and the coating layer and niobium in the coating layer.

[0017] As described in the second aspect of the invention, it has been found that in metal oxides containing titanium oxide in the core and the coating layer, when the oxygen vacancy rate has a specific relationship, the technical problems that have occurred in the prior art can be solved.

[0018] Although the reason is not yet clear, the inventor believes it to be as follows.

[0019] As in the first aspect, when metal oxide particles that typically contain titanium oxide include niobium as another element with a different valence, conductivity increases; however, the sites where niobium is present will have high polarity. Therefore, if there is a large amount of niobium in such sites, the sites act as traps, and electrical properties such as residual charge may deteriorate.

[0020] However, when the protective layer has metal oxide particles that preferentially contain niobium in the coating containing titanium oxide particles (the proportion of niobium in the coating is higher than that in the core), the conductive paths in the protective layer are more likely to connect. As a result, charge is less likely to remain in the protective layer, and thus charge deterioration can be prevented.

[0021] As in the second aspect, conductivity increases when metal oxide particles, typically containing titanium oxide, have oxygen vacancies in their crystal structure. However, sites with oxygen vacancies will exhibit high polarity, and if numerous oxygen vacancies exist, these sites act as traps. Consequently, electrical properties, such as residual charge, deteriorate.

[0022] However, when the protective layer contains titanium oxide particles, there is a specific relationship between the oxygen vacancy rate of the metal oxide particles, the core, and the coating layer. The conductive paths in the protective layer are connected, and it is less likely that charge will remain in the protective layer. Therefore, degradation of the charge-carrying capacity can be prevented.

[0023] From the viewpoint of the stability and uniformity of the conductive path performance of each particle, it is conceivable that the metal oxide particles of the present invention need to each contain titanium oxide in the core and the coating layer.

[0024] As per the above mechanism, the various components interact organically within the protective layer containing the binder resin, thereby achieving the effects of the present invention.

[0025] [Electronic photographic sensor]

[0026] The electrophotographic photosensitive component of the present invention includes a support, a conductive layer, a photosensitive layer, and a protective layer.

[0027] The method for producing the electrophotographic photosensitive component of the present invention includes, for example, the following steps: preparing a coating liquid for each layer described later, applying the liquid in the desired layer sequence, and drying the liquid. Examples of methods for applying the coating liquid include dip coating, spray coating, inkjet coating, roller coating, die coating, blade coating, curtain coating, wire rod coating, and ring coating. From the viewpoint of efficiency and productivity, dip coating is preferred.

[0028] The following will describe each layer.

[0029] <Support Body>

[0030] In this invention, the electrophotographic photosensitive component has a support. Preferably, the support is a conductive support. Examples of the support's shape include cylindrical, strip-shaped, and sheet-shaped. A cylindrical support is preferred. Furthermore, the surface of the support can be electrochemically treated, such as anodizing, sandblasting, or machining.

[0031] Metal, resin, or glass are preferred as materials for the support.

[0032] Examples of metals include aluminum, iron, nickel, copper, gold, stainless steel, and their alloys. Among these, aluminum supports are preferred.

[0033] For example, the resin or glass can be made conductive by mixing it with a conductive material or by coating the resin or glass with a conductive material.

[0034] <Conductive Layer>

[0035] In this invention, a conductive layer is disposed on the support. The conductive layer can cover defects and unevenness on the surface of the support and control light reflection on the surface of the support.

[0036] The conductive layer preferably comprises conductive particles and resin.

[0037] Examples of materials used for conductive particles include metal oxides, metals, and carbon black.

[0038] Examples of metal oxides include zinc oxide, aluminum oxide, indium oxide, silicon oxide, zirconium oxide, tin oxide, titanium oxide, magnesium oxide, antimony oxide, and bismuth oxide. Examples of metals include aluminum, nickel, iron, nickel-chromium alloys, copper, zinc, and silver.

[0039] Preferably, metal oxides are used as conductive particles, and more particularly, titanium oxide, tin oxide and zinc oxide are preferred.

[0040] When metal oxides are used as conductive particles, the surface of the metal oxide can be treated with silane coupling agents, or the metal oxide can be doped with elements such as phosphorus or aluminum or their oxides.

[0041] Conductive particles can also be a layered structure having a core particle and a coating layer of coating particles. Examples of core particles include titanium oxide, barium sulfate, and zinc oxide. Examples of coating layers include metal oxides such as tin oxide.

[0042] When metal oxides are used as conductive particles, their volume average particle size is preferably 1 nm or more and 500 nm or less, more preferably 3 nm or more and 400 nm or less.

[0043] Examples of resins include polyester resins, polycarbonate resins, polyvinyl acetal resins, acrylic resins, silicone resins, epoxy resins, melamine resins, polyurethane resins, phenolic resins, and alkyd resins.

[0044] The conductive layer may further contain a masking agent, such as silicone oil, resin particles, or titanium dioxide.

[0045] The average thickness of the conductive layer is preferably 1 μm or more and 50 μm or less, and particularly preferably 3 μm or more and 40 μm or less.

[0046] The conductive layer can be formed by preparing a coating liquid containing the above-mentioned materials and solvents, forming a liquid coating film, and drying the coating film. Examples of solvents used in the coating liquid include alcohol-based solvents, sulfoxide-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Examples of dispersion methods for dispersing conductive particles in the coating liquid for the conductive layer include methods using a paint mixer, a sand mill, a ball mill, or a liquid impact type high-speed disperser.

[0047] <Undercoat>

[0048] In this invention, an undercoat layer can be disposed on the conductive layer. The undercoat layer improves the adhesion between layers, thereby providing charge injection prevention.

[0049] The primer layer preferably comprises a resin. The primer layer can be formed into a cured film by polymerizing a composition comprising monomers having polymerizable functional groups.

[0050] Examples of resins include polyester resins, polycarbonate resins, polyvinyl acetal resins, acrylic resins, epoxy resins, melamine resins, polyurethane resins, phenolic resins, polyvinylphenol resins, alkyd resins, polyvinyl alcohol resins, polyethylene oxide resins, polypropylene oxide resins, polyamide resins, polyamic acid resins, polyimide resins, polyamide-imide resins, and cellulose resins.

[0051] Examples of polymerizable functional groups included in monomers with polymerizable functional groups include isocyanate groups, terminal isocyanate groups, hydroxymethyl groups, alkylated hydroxymethyl groups, epoxy groups, metal alkoxide groups, hydroxyl groups, amino groups, carboxyl groups, mercapto groups, carboxylic anhydride groups, and carbon-carbon double bond groups.

[0052] To improve electrical properties, the primer layer may further comprise electron transport materials, metal oxides, metals, and conductive polymers. Among these, electron transport materials and metal oxides are preferred.

[0053] Examples of electron transport materials include quinone compounds, imide compounds, benzimidazole compounds, cyclopentadienyl compounds, fluorenone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, halogenated aryl compounds, thiophene compounds, and boron-containing compounds. Electron transport materials with polymerizable functional groups can be used as electron transport materials and copolymerized with the aforementioned monomers having polymerizable functional groups to form a base coating as a cured film.

[0054] Examples of metal oxides include indium tin oxide, tin oxide, indium oxide, titanium oxide, zinc oxide, aluminum oxide, and silicon dioxide. Examples of metals include gold, silver, and aluminum.

[0055] The base coat may further contain additives.

[0056] The average thickness of the base coating is preferably 0.1 μm or more and 50 μm or less, more preferably 0.2 μm or more and 40 μm or less, and particularly preferably 0.3 μm or more and 30 μm or less.

[0057] The primer layer can be formed by preparing a primer coating liquid containing the above-mentioned materials and solvents, forming a liquid coating film, and drying and / or curing the coating film. Examples of solvents used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

[0058] <Photosensitive layer>

[0059] The photosensitive layer of an electrophotographic photosensitive component is mainly classified into (1) stacked photosensitive layer and (2) single-layer photosensitive layer. (1) Stacked photosensitive layer has a charge-generating layer containing charge-generating material and a charge-transporting layer containing charge-transporting material. (2) Single-layer photosensitive layer has a photosensitive layer containing both charge-generating material and charge-transporting material.

[0060] (1) Layered photosensitive layer

[0061] The stacked photosensitive layer has a charge generation layer and a charge transport layer.

[0062] (1-1) Charge generation layer

[0063] The charge-generating layer preferably comprises a charge-generating substance and a resin.

[0064] Examples of charge-generating substances include azo pigments, perylene pigments, polycyclic quinone pigments, indigo pigments, and phthalocyanine pigments. Among these, azo pigments and phthalocyanine pigments are preferred. Of the phthalocyanine pigments, titanium dioxide phthalocyanine pigments, gallium chloride phthalocyanine pigments, and hydroxy gallium phthalocyanine pigments are preferred.

[0065] The content of the charge-generating substance in the charge-generating layer is preferably 40% by mass or more and 85% by mass or less, more preferably 60% by mass or more and 80% by mass or less, based on the total mass of the charge-generating layer.

[0066] Examples of resins include polyester resins, polycarbonate resins, polyvinyl acetal resins, polyvinyl butyral resins, acrylic resins, silicone resins, epoxy resins, melamine resins, polyurethane resins, phenolic resins, polyvinyl alcohol resins, cellulose resins, polystyrene resins, polyvinyl acetate resins, and polyvinyl chloride resins. Among these, polyvinyl butyral resin is more preferred.

[0067] The charge-generating layer may further contain additives, such as antioxidants or UV absorbers. Specific examples include hindered phenolic compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, and benzophenone compounds.

[0068] The average thickness of the charge generation layer is preferably 0.1 μm or more and 1 μm or less, more preferably 0.15 μm or more and 0.4 μm or less.

[0069] The charge-generating layer can be formed by preparing a coating solution containing the above-mentioned materials and solvents, forming a liquid coating film, and drying the coating film. Examples of solvents used in the coating solution include alcohol solvents, sulfoxide solvents, ketone solvents, ether solvents, ester solvents, and aromatic hydrocarbon solvents.

[0070] (1-2) Charge transport layer

[0071] The charge transport layer preferably comprises a charge transport material and a resin.

[0072] Examples of charge-transporting substances include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styryl compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from each of these substances. Among these, triarylamine compounds and benzidine compounds are preferred.

[0073] The content of charge transport material in the charge transport layer is preferably 25% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 55% by mass or less, based on the total mass of the charge transport layer.

[0074] Examples of resins include polyester resins, polycarbonate resins, acrylic resins, and polystyrene resins. Among these, polycarbonate resins and polyester resins are preferred. As a polyester resin, polyarylate resins are particularly preferred.

[0075] The content ratio (mass ratio) between the charge transport material and the resin is preferably 4:10 to 20:10, more preferably 5:10 to 12:10.

[0076] The charge transport layer may contain additives such as antioxidants, UV absorbers, plasticizers, leveling agents, lubricants, or abrasion improvers. Specific examples include hindered phenolic compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluoropolymer particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

[0077] The average thickness of the charge transport 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.

[0078] The charge transport layer can be formed by preparing a coating solution containing the above-described materials and solvents, forming a liquid coating film, and drying the coating film. Examples of solvents used for the coating solution include alcohol-based solvents, ketone-based solvents, ether-based solvents, ester-based solvents, and aromatic hydrocarbon-based solvents. Among these solvents, ether-based solvents or aromatic hydrocarbon-based solvents are preferred.

[0079] (2) Single-layer photosensitive layer

[0080] A single-layer photosensitive layer can be prepared by preparing a coating solution containing a charge-generating substance, a charge-transporting substance, a resin, and a solvent, forming a liquid coating film, and then drying the coating film. Examples of charge-generating substances, charge-transporting substances, and resins are the same as those materials in the section "(1) Laminated Photosensitive Layers".

[0081] <Protective Layer>

[0082] In this invention, a protective layer is disposed on the photosensitive layer.

[0083] The protective layer comprises an adhesive resin and metal oxide particles according to the first or second aspect of the invention. In the second aspect, more preferably, niobium is further included in the coating layer of the metal oxide particles.

[0084] In a first aspect of the invention, the coating layer needs to contain niobium.

[0085] The core of the metal oxide particles may not contain niobium. If niobium is uniformly present throughout the metal oxide particles, the particles act as charge traps, thereby degrading their charging ability. Therefore, the niobium content based on the total mass of the coating layer needs to be higher than the niobium content based on the total mass of the core. In this case, the niobium content based on the total mass of the coating layer is preferably 10 times or more than the niobium content based on the total mass of the core. The niobium content based on the total mass of the coating layer is preferably 0.5% by mass or more, more preferably 2.0% by mass or more. This content is further preferably 5.0% by mass or more and 15.0% by mass or less.

[0086] The niobium content in the metal oxide particles is preferably 2.6% by weight or more based on the total mass of the metal oxide particles. More preferably, it is 2.6% by weight or more and 10.0% by weight or less.

[0087] In this invention, when the particles satisfy the above formulas (1) and (2), the oxygen vacancy rate A of the entire metal oxide particles is more preferably 1.0% or less, and more preferably 0.5% or less.

[0088] In the metal oxide particles of the present invention, the higher the oxygen vacancy rate of the coating layer, that is, the larger the C / B value, the more selectively oxygen vacant the coating layer is.

[0089] Considering that oxygen vacancies uniformly distributed throughout the metal oxide particles cause the particles to act as charge traps, thereby degrading their charging ability, the C / B ratio needs to be greater than 10, and more preferably greater than 20, in order to achieve the effect of the present invention. The core of the metal oxide particles can be completely free of oxygen vacancies.

[0090] In this invention, the amount of niobium in the coating of the metal oxide particles and the ratio between the oxygen vacancy rate of the coating of the metal oxide particles and the oxygen vacancy rate of the core can be measured by energy-dispersive X-ray analysis (EDX).

[0091] In this invention, the amount of niobium in the coating of the metal oxide particles and the ratio between the oxygen vacancy rate of the coating and the oxygen vacancy rate of the core are measured by SEM-EDX analysis on the cross-section of the metal oxide particles.

[0092] In this invention, the oxygen vacancy rate of the metal oxide particles can be determined by thermogravimetric analysis (TG). When the metal oxide particles of this invention are heated in an oxygen atmosphere, their mass decreases immediately after the start of heating due to the desorption of water and other substances adsorbed on the surface of the metal oxide particles. Subsequently, the mass begins to increase at a certain temperature. The mass at which the mass changes from decrease to increase is considered the minimum mass, and the difference between this minimum and maximum mass is obtained during subsequent heating. This difference is caused by the binding of oxygen to oxygen vacancies in the titanium oxide particles.

[0093] In this invention, the oxygen vacancy rate of the metal oxide particles is measured using a thermogravimetric analysis apparatus (trade name: Q5000IR, manufactured by TA Instruments). The heating rate during the measurement is 10°C / min, and the measurement is performed under an oxygen flow. The mass at which the mass increases within the range of 300°C to 900°C is considered the minimum mass, and the oxygen vacancy rate A is determined from the minimum mass and the maximum mass during subsequent heating.

[0094] The proportion (mass%) of titanium in the core of metal oxide particles can also be determined by ICP emission analysis of powder containing the same material as the particles used in the core. The measurement is performed using a solution obtained by dissolving the material in an acid such as sulfuric acid.

[0095] In this invention, cores of various shapes, such as spherical, polyhedral, ellipsoidal, sheet-like, and needle-like, can be used as the cores of the metal oxide particles. From the viewpoint of reducing image defects such as black spots, spherical, polyhedral, or ellipsoidal cores are preferred. Furthermore, spherical or near-spherical polyhedral cores are more preferred. Titanium oxide particles are preferably used as the cores of the metal oxide particles.

[0096] In this invention, the core and coating layer preferably comprise anatase titanium dioxide or rutile titanium dioxide. Furthermore, the core and coating layer more preferably comprise anatase titanium dioxide, and particularly preferably formed from anatase titanium dioxide. When anatase titanium dioxide is used, fluctuations in the bright region potential are less likely to occur.

[0097] In this invention, the average primary particle size of the metal oxide particles is preferably 30 nm or more and 500 nm or less. When the average primary particle size of the metal oxide particles is 30 nm or more, particle re-aggregation is less likely to occur after the coating liquid for the protective layer is prepared. If particle re-aggregation occurs, the stability of the coating liquid for the protective layer may decrease, or cracks may occur on the surface of the protective layer to be formed. When the average primary particle size of the metal oxide particles is 500 nm or less, the surface of the protective layer is less likely to become rough. If the surface of the protective layer becomes rough, image exposure scattering occurs, and image quality may be degraded as a result.

[0098] Furthermore, in this invention, the average primary particle size of the metal oxide particles is more preferably 30 nm or more and 400 nm or less.

[0099] In this invention, the average primary diameter D1 of metal oxide particles is determined using a scanning electron microscope as described below. The particles to be measured are observed using a scanning electron microscope S-4800 manufactured by Hitachi, Ltd., and the diameter of each of 100 particles selected from the images obtained through observation is measured. The arithmetic mean of the particle diameters is calculated and defined as the average primary diameter D1. Each particle diameter is defined as "(a+b) / 2", where a is the longest side of the primary particle and b is the shortest side of the primary particle. In needle-shaped metal oxide particles or flake-shaped titanium oxide particles, the average particle diameter is calculated for each major axis diameter and minor axis diameter to obtain the average primary diameter.

[0100] In this invention, the surface of metal oxide particles can be treated with silane coupling agents or the like.

[0101] In this invention, the content of metal oxide particles is preferably 33% or more by volume, more preferably 50% or more by volume, based on the total volume of the protective layer.

[0102] When this range is met, the probability of contact between metal oxide particles in the protective layer increases. Then, conductive paths created by niobium and oxygen vacancies in the coating layer are more likely to connect, thereby improving the prevention of charge retention.

[0103] The protective layer of the present invention may comprise a charge-transporting substance, and examples of charge-transporting substances include polycyclic aromatic compounds, heterocyclic compounds, hydrazone compounds, styrene compounds, enamine compounds, benzidine compounds, triarylamine compounds, and resins having groups derived from each of these substances. Triarylamine compounds and benzidine compounds are preferred.

[0104] Examples of adhesive resins include polyester resins, acrylic resins, phenoxy resins, polycarbonate resins, polystyrene resins, phenolic resins, melamine resins, and epoxy resins. Among these, polycarbonate resins, polyester resins, and acrylic resins are preferred.

[0105] The protective layer can be formed into a cured film by polymerizing a composition containing monomers with polymerizable functional groups. Examples of reactions include thermal polymerization, photopolymerization, and radiation polymerization. Examples of polymerizable functional groups included in the monomers with polymerizable functional groups include acrylic groups and methacrylic groups. Materials with charge-transporting capabilities can be used as monomers with polymerizable functional groups.

[0106] The protective layer of this invention may contain additives, such as antioxidants, ultraviolet absorbers, plasticizers, leveling agents, lubricants, or wear resistance improvers. Specific examples include hindered phenolic compounds, hindered amine compounds, sulfur compounds, phosphorus compounds, benzophenone compounds, siloxane-modified resins, silicone oils, fluoropolymer particles, polystyrene resin particles, polyethylene resin particles, silica particles, alumina particles, and boron nitride particles.

[0107] The average thickness of the protective layer is preferably 0.3 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 7 μm or less.

[0108] The protective layer can be formed by preparing a coating liquid containing the above-described materials and solvents, forming a liquid coating film, and drying and / or curing the coating film. Examples of solvents used in the coating liquid include alcohol solvents, ketone solvents, ether solvents, sulfoxide solvents, ester solvents, and aromatic hydrocarbon solvents.

[0109] [Processing box and electrophotographic equipment]

[0110] The processing box of the present invention integrally supports the aforementioned electrophotographic photosensitive component and at least one unit selected from the group consisting of a charging unit, a developing unit, a transfer unit, and a cleaning unit, and is detachably mounted on the main body of the electrophotographic device.

[0111] The electrophotographic apparatus of the present invention includes the above-mentioned electrophotographic photosensitive component, charging unit, exposure unit, developing unit and transfer unit.

[0112] An example of a schematic structure of an electrophotographic device having a processing box including an electrophotographic photosensitive element is shown in Figure 1 As shown in the image.

[0113] A cylindrical electrophotographic photosensitive element 1 is driven to rotate at a predetermined circumferential speed in the direction indicated by the arrow around a central axis 2. The surface of the electrophotographic photosensitive element 1 is charged to a predetermined positive or negative potential by a charging unit 3. The accompanying drawings show a roller charging system based on a roller-type charging element, but charging systems such as corona charging, proximity charging, or injection charging systems can also be used. The charged surface of the electrophotographic photosensitive element 1 is irradiated with exposure light 4 from an exposure unit (not shown), and an electrostatic latent image corresponding to the target image is formed thereon. The electrostatic latent image formed on the surface of the electrophotographic photosensitive element 1 is developed using toner stored in a developing unit 5, and a toner image is formed on the surface of the electrophotographic photosensitive element 1. The toner image formed on the surface of the electrophotographic photosensitive element 1 is transferred to a transfer material 7 by a transfer unit 6. The transfer material 7, on which the toner image is transferred, is conveyed to a fixing unit 8 for fixing the toner image and is printed onto the exterior of the electrophotographic device. Electrophotographic apparatus may include a cleaning unit 9 for removing deposits such as toner remaining on the surface of the electrophotographic photosensitive member 1 after transfer. Optionally, a so-called cleanerless system may be used, in which deposits are removed by a developing unit or the like without a separate cleaning unit. Electrophotographic apparatus may include a static elimination mechanism that uses pre-exposure light 10 from a pre-exposure unit (not shown) to static-eliminate the surface of the electrophotographic photosensitive member 1. Additionally, a guide unit 12, such as a guide rail, may be provided for detachably mounting the processing cartridge 11 of the present invention to the main body of the electrophotographic apparatus.

[0114] The electrophotographic photosensitive element of the present invention can be used in, for example, laser beam printers, LED printers, copiers, fax machines and multifunction printers.

[0115] [Example]

[0116] The invention is described in more detail below by way of examples and comparative examples. Unless departing from the spirit of the invention, the invention is by no means limited to the following examples. In the following examples, unless otherwise stated, "parts" are by weight.

[0117] [Production of metal oxide particles]

[0118] (Production Example 1)

[0119] (Metal oxide particles A1)

[0120] Titanium dioxide, as the core, can be produced using the known sulfuric acid process. Specifically, a metatitanic acid slurry is prepared by hydrolyzing a solution containing titanium sulfate and titanium oxysulfate through heating. Dehydration and calcination of the metatitanic acid slurry yield titanium dioxide.

[0121] Anatase-type titanium dioxide particles with an average primary diameter of 150 nm in which niobium was not detected were used as core particles. One hundred grams of core particles were dispersed in water to form a 1 L aqueous suspension, which was then heated to 60 °C. A titanium-niobate solution, prepared by mixing a niobium solution containing 3.1 g of niobium pentachloride (NbCl5) dissolved in 100 mL of 11.4 mol / L hydrochloric acid with 600 mL of a titanium sulfate solution containing 33.7 g of Ti and 10.7 mol / L sodium hydroxide solution, was simultaneously added dropwise (in parallel) to the suspension over 3 hours to bring the pH of the suspension to 2 to 3. After the addition was complete, the pH was adjusted to near neutral, and a flocculant was added to induce sedimentation of the solids. The supernatant was removed, the residue was filtered, and the residue was washed and dried at 110 °C to obtain an intermediate containing 0.1 wt% organic matter derived from the flocculant, calculated as C. The intermediate was treated in nitrogen at 800 °C to prepare metal oxide particles Al with an average primary particle size of 190 nm.

[0122] (Metal oxide particles A2 to A9, B1 to B6, and C1 to C6)

[0123] Except for changing the conditions used for the core and coating in the production of metal oxide particles A1, metal oxide particles A2 to A9, B1 to B6 and C1 to C6 having titanium oxide are produced in the same manner as in production example 1.

[0124] (Comparative Production Example 1)

[0125] According to Japanese Patent Application Publication No. 2007-334334, a powder containing titanium oxide particles R1 is obtained, wherein the particles R1 are rutile titanium oxide particles with an average primary particle size of 200 nm.

[0126] (Comparative Production Example 2)

[0127] According to Japanese Patent Application Publication No. 2005-17470, a powder containing titanium oxide particles R2 is obtained, wherein the particles R2 are anatase titanium oxide particles with an average primary particle size of 180 nm and a niobium content of 1.0% by weight.

[0128] [Table 1]

[0129]

[0130] [Preparation of coating solution for protective layer]

[0131] (Coating liquid A1 for protective layer)

[0132] Twenty-two parts of the compound represented by the following structural formula (1) were mixed with a mixed solvent of 144 parts of 2-propanol and 16 parts of tetrahydrofuran. 100 parts of metal oxide particles A1 were added to the solution and the mixture was stirred.

[0133] The resulting material was placed in a vertical sand mill using 200 parts of glass beads with an average particle size of 1.0 mm, and dispersed for 2 hours at a dispersion temperature of 23±3℃ and a rotation speed of 1,500 rpm (circumferential speed: 5.5 m / s) to obtain a dispersion.

[0134] Glass beads were removed from the dispersion using a sieve, and the resulting dispersion was filtered under pressure using PTFE filter paper (trade name: PF-060, manufactured by Advantec Toyo Kaisha, Ltd.) to prepare a coating solution A1 for the protective layer.

[0135]

[0136] (Coating solutions A2 to A13, B1 to B10, C1 to C10 and R1 to R2 for the protective layer)

[0137] Except for changing the type and amount (parts by mass) of the metal oxide particles used to prepare the protective coating liquid A1 to the ones shown in Table 2, protective coating liquids A2 to A13, B1 to B10, C1 to C10 and R1 to R2 are prepared by the same operation as in the preparation of protective coating liquid A1.

[0138] (Coating liquid A14 for protective layer)

[0139] Using 22 parts of an acrylic monomer represented by the above structural formula (1), 7 parts of 2-methylthioxanthone as a photoinitiator, 100 parts of metal oxide particles A1 and 160 parts of ethanol, a protective coating solution A14 was prepared by dispersing in the same manner as in the protective coating solution A1.

[0140] [Table 2]

[0141]

[0142] [Production of Electrophotographic Photosensitive Components]

[0143] (Electrophotographic photosensitive component 1)

[0144] An aluminum cylinder (JIS-A3003, aluminum alloy) with a diameter of 24 mm and a length of 257.5 mm was used as the support (conductive support).

[0145] An aluminum cylinder (JIS-A3003, aluminum alloy) with a length of 260.5 mm and a diameter of 30 mm was used as the support (conductive support).

[0146] Next, 50 parts of titanium dioxide particles coated with oxygen-deficient tin oxide (powder resistivity: 120 Ω·cm, tin oxide coating rate: 40%), 40 parts of phenolic resin (PLYOPHEN J-325, manufactured by DIC Corporation, resin solid content: 60%) and 55 parts of methoxypropanol were placed in a sand mill using glass beads with a diameter of 1 mm and dispersed for 3 hours to prepare a coating solution for the conductive layer.

[0147] The average particle size of titanium oxide particles coated with oxygen-deficient tin oxide in the conductive layer coating solution was measured by centrifugation sedimentation using a particle size distribution analyzer (trade name: CAPA700) manufactured by Horiba, Ltd., with tetrahydrofuran as the dispersion medium and a rotation speed of 5,000 rpm. The result was an average particle size of 0.30 μm.

[0148] The conductive layer is applied to the support by dip coating with a coating liquid, and the resulting coating is dried at 160°C for 30 minutes, thereby forming a conductive layer with a thickness of 30 μm.

[0149] Next, the following materials are dissolved in a mixed solvent of 50 parts 1-methoxy-2-propanol and 50 parts tetrahydrofuran.

[0150] The compound represented by formula (2): 3.36 parts

[0151] Styrene-acrylic resin as a polyolefin resin (trade name: UC-3920, manufactured by Toagosei Co., Ltd.): 0.35 parts

[0152] The terminal isocyanate compound (trade name: SBB-70P, manufactured by Asahi Kasei Corporation): 6.40 parts

[0153] 1.8 parts of silica slurry (trade name: IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solids concentration: 15% by mass, viscosity: 9 mPa·s) dispersed in isopropanol were added to the solution, and the mixture was stirred for 1 hour. The result was then filtered under pressure using a polytetrafluoroethylene filter (trade name: PF020) manufactured by ADVANTEC.

[0154] The resulting primer layer is applied to the conductive layer by dip coating with a coating liquid, and the resulting coating is cured (polymerized) by heating at 170°C for 40 minutes to form a primer layer with a thickness of 0.7 μm.

[0155]

[0156] Next, hydroxy gallium phthalocyanine crystals (charge-generating materials) in crystalline form, exhibiting peaks at Bragg angles (2θ±0.2°) of 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3° in CuKα characteristic X-ray diffraction, were provided. Eight parts of hydroxy gallium phthalocyanine crystals, four parts of polyvinyl butyral (trade name: S-LEC BX-1, manufactured by Sekisui Chemical Co., Ltd.), and 250 parts of cyclohexanone were placed in a sand mill using glass beads with a diameter of 1 mm and dispersed for 2 hours. Next, 250 parts of ethyl acetate were added to prepare a coating solution for the charge-generating layer.

[0157] The charge generation layer is applied to the base layer by dip coating to form a coating film, and the resulting coating film is dried at 95°C for 10 minutes, thereby forming a charge generation layer with a thickness of 0.2 μm.

[0158] Next, 6 parts of an amine compound (hole transport substance) represented by formula (3), 2 parts of an amine compound (hole transport substance) represented by formula (4), and 10 parts of a polyester resin having structural units represented by formulas (5) and (6) in a 5 / 5 ratio and having a weight average molecular weight (Mw) of 100,000 are dissolved in a mixed solvent of 40 parts of dimethoxymethane and 60 parts of chlorobenzene to prepare a coating solution for the charge transport layer.

[0159]

[0160]

[0161] The charge transport layer is applied to the charge generation layer by dip coating with a coating liquid, and the resulting coating is dried at 120°C for 40 minutes, thereby forming a charge transport layer with a thickness of 22 μm.

[0162] Next, the protective layer was applied to the charge transport layer using coating solution A1 by dip coating to form a coating film, and the resulting coating film was dried at 50°C for 6 minutes. Subsequently, under a nitrogen atmosphere, the coating film was irradiated with an electron beam for 1.6 seconds while the support (the object to be irradiated) was rotated at 300 rpm, with an accelerating voltage of 70 kV and a beam current of 2.0 mA. The oxygen concentration during electron beam irradiation was 810 ppm. Next, the coating film was allowed to cool naturally in the atmosphere until its temperature reached 25°C. Then, the coating film was heat-treated at 120°C for one hour, thereby forming a protective layer with a thickness of 3 μm. Thus, a cylindrical (drum-shaped) electron photographic photosensitive component with a protective layer as described in Example 1 was prepared.

[0163] (Electrophotographic photosensitive elements 2 to 33 and electrophotographic photosensitive elements R1 to R2)

[0164] Except for the protective coating liquid used in the production of the electrophotographic photosensitive component, which is replaced by the protective coating liquids A2 to A14, B1 to B10, C1 to C10 and R1 to R2 respectively, the electrophotographic photosensitive components are prepared in the same manner as in Example 1.

[0165] (Electrophotographic photosensitive component 34)

[0166] In addition to using a protective coating liquid 34 and applying it to the charge transport layer by dip coating, after the coating film dries, a high-pressure mercury lamp at 250W / cm is used. 2 The coating was irradiated with ultraviolet light of high intensity for 60 seconds and dried with hot air at 120°C for 2 hours to form a protective layer with a thickness of 3 μm. In addition, the electrophotographic photosensitive component was prepared in the same manner as in Example 1.

[0167] (Analysis of the protective layer of electrophotographic photosensitive components)

[0168] Five 5mm square slices were cut from each of the above-produced electrophotographic photosensitive components to prepare five sample slices for observation of each electrophotographic photosensitive component.

[0169] First, for each electron-photographic photosensitive component, the protective layer was sliced ​​to a thickness of 150 nm using one sample slide and a focused ion beam processing observation device (trade name: FB-2000A, manufactured by Hitachi High-Tech Manufacturing & Service Corporation) according to the FIB-μ sampling method. The composition of the protective layer was analyzed using a field emission electron microscope (HRTEM) (trade name: JEM-2100F, manufactured by JEOL, Ltd.) and an energy-dispersive X-ray spectrometer (EDX) (trade name: JED-2300T, manufactured by JEOL, Ltd.). The EDX measurement conditions were an accelerating voltage of 200 kV and a beam diameter of 1.0 nm.

[0170] One hundred metal oxide particles were selected from the obtained EDX images. The diameter of the core and the thickness of the coating layer of each particle were measured. The ratio between the average primary diameter of the core and the average thickness of the coating layer was calculated from their arithmetic mean. Thus, the average primary diameter of the metal oxide particles with an average coating thickness of 20 nm and an average primary diameter of 150 nm would be 190 nm.

[0171] Next, using the remaining four sample pieces from each electrophotographic photosensitive component, the protective layers were three-dimensionally rendered to dimensions of 2μm × 2μm × 2μm using FIB-SEM Slice & View. The particle content based on the total volume of the protective layer was calculated using the contrast difference in FIB-SEM Slice & View. In this embodiment, the Slice & View conditions were set as follows.

[0172] Sample preparation for analysis: FIB method

[0173] Processing and observation equipment: NVision 40 manufactured by SII / Zeiss

[0174] Slice spacing: 10nm

[0175] Observation conditions:

[0176] Accelerating voltage: 1.0kV

[0177] Sample tilt: 54°

[0178] WD: 5mm

[0179] Detector: BSE detector

[0180] Aperture: 60μm, high current.

[0181] ABC: ON

[0182] Image resolution: 1.25nm / pixel

[0183] Analysis was performed over a region of 2 μm length × 2 μm width, and information from each cross-section was integrated to determine the length of each 2 μm × width × thickness (8 μm) region. 3 The volume V of the sample was measured. The measurement environment was: temperature: 23℃ and pressure: 1×10⁻⁶. -4 Pa. As a processing and observation device, a Strata 400S (sample tilt: 52°) manufactured by FEI Company can also be used. Information on each cross-section is obtained by image analysis of the area of ​​specific titanium dioxide particles of the present invention or specific titanium dioxide particles used in each comparative example. Image analysis is performed using Image-Pro Plus image processing software manufactured by Media Cybernetics Inc.

[0184] The 2μm×2μm×2μm (unit volume: 8μm) dimensions in each of the four sample pieces 3 In this study, the volume V of the titanium oxide particles of the present invention or the titanium oxide particles used in each comparative example is determined based on the obtained information. Then, (V μm) is calculated. 3 / 8μm 3 (×100) values. The (Vμm) values ​​from the four sample pieces. 3 / 8μm 3 The average value of (×100) is defined as the content [volume %] of the titanium oxide particles of the present invention in the protective layer or the titanium oxide particles used in each comparative example, based on the total volume of the protective layer. The results are shown in Table 3.

[0185] <Evaluation>

[0186] First, the charge-carrying capacity during repeated use under the following conditions was evaluated using the prepared electrophotographic photosensitive elements 1 to 34 and R1 to R2.

[0187] When the charge-carrying capacity deteriorates, the dark area potential (Vd) decreases and fogging increases.

[0188] As an electrophotographic device, a modification of the HP LaserJet Enterprise Color M 553dn laser beam printer (trade name) manufactured by Hewlett-Packard Company was used. The modification was intended for evaluation of the electrophotographic equipment to adjust and measure image exposure and development bias.

[0189] First, the exposure was adjusted so that the bright area potential of the electrophotographic photosensitive element in each embodiment and comparative example was -180V, and then the dark area potential (Vd) was measured.

[0190] Then, the developing bias voltage Vdc was adjusted to -450V, and the photosensitive element was mounted on the cyan box of the electrophotographic equipment.

[0191] Subsequently, under an environment of 23°C and 50% relative humidity, a solid white image was printed on A4-sized plain paper using a single cyan color.

[0192] For fogging assessment, the reflectance of the white portion of the above image and the reflectance of the unused paper were measured using a white photometer (trade name: REFLECTMETER TC-6DS / A, manufactured by Tokyo Denshoku, Co., Ltd.), and the difference between the two reflectances was considered fogging. The formula was: Reflectance of unused paper - Reflectance of the white portion of the image = Fogging %. Fogging of 2.0% or higher was rated as NG (Not Good). The results are shown in Table 3.

[0193] [Table 3]

[0194]

[0195]

[0196] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be interpreted in the broadest sense to cover all such modifications and equivalent structures and functions.

Claims

1. An electrophotographic photosensitive component, comprising, in sequence, a support, a conductive layer, a photosensitive layer, and a protective layer, characterized in that, The protective layer comprises adhesive resin and metal oxide particles. The content of the metal oxide particles is at least 50% by volume based on the total volume of the protective layer. The metal oxide particles include a core and a coating layer covering the core. The core contains titanium oxide. The coating layer comprises titanium oxide and niobium, and The presence ratio of niobium based on the total mass of the cladding layer is higher than the presence ratio of niobium based on the total mass of the core.

2. An electrophotographic photosensitive component, comprising, in sequence, a support, a conductive layer, a photosensitive layer, and a protective layer, characterized in that, The protective layer comprises adhesive resin and metal oxide particles. The content of the metal oxide particles is at least 50% by volume based on the total volume of the protective layer. The metal oxide particles include a core and a coating layer covering the core. The core contains titanium oxide. The coating layer comprises titanium oxide, and When the oxygen vacancy rate of the metal oxide particles is represented by A%, the oxygen vacancy rate of the core is represented by B%, and the oxygen vacancy rate of the coating layer is represented by C%, the following equations (1) and (2) are satisfied. A≤2.0 (1) 10×B <C (2)。 3. The electrophotographic photosensitive component according to claim 2, wherein the coating layer further comprises niobium.

4. The electrophotographic photosensitive component according to claim 1 or 3, wherein the presence ratio of niobium based on the total mass of the cladding layer is more than 10 times the presence ratio of niobium based on the total mass of the core.

5. The electrophotographic photosensitive component according to claim 1 or 3, wherein the niobium content in the metal oxide particles is 2.6% by weight or more based on the total mass of the metal oxide particles.

6. The electrophotographic photosensitive component according to claim 1 or 3, wherein the titanium oxide contained in the core is anatase titanium oxide or rutile titanium oxide.

7. A processing box, characterized in that, It integrally supports the electrophotographic photosensitive element according to any one of claims 1 to 6 and at least one unit selected from the group consisting of a charging unit, a developing unit, and a cleaning unit, and is detachably mounted to the body of the electrophotographic device.

8. An electrophotographic device, characterized in that, It includes an electrophotographic photosensitive element, a charging unit, an exposure unit, a developing unit, and a transfer unit according to any one of claims 1 to 6.

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