Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

This electrophotographic photoreceptor is provided with a conductive base material (2), a photosensitive layer (3) and a protective layer (5). The photosensitive layer (3) contains a charge generating agent. The protective layer (5) is an outermost surface layer of the electrophotographic photoreceptor. The protective layer (5) contains a compound represented by formula (A). In formula (A), R21 represents a hydrogen atom, Li+, or K+, and R22 and R23 each independently represent a C1-4 alkyl group substituted by at least one halogen atom.

Description

[Technical Field]

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

[0002] When images are repeatedly formed using an image forming apparatus equipped with an electrophotographic photoreceptor, the electrophotographic photoreceptor may gradually wear out. In order to suppress wear and extend the life of the electrophotographic photoreceptor, a hard protective layer may be provided on the surface of the electrophotographic photoreceptor. For example, the electrophotographic photoreceptor described in Patent Document 1 has a photosensitive layer on a conductive support, and a protective layer is provided on the photosensitive layer. An example of Patent Document 1 describes the use of rutile titanium oxide in producing a dispersion for forming a protective layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-286707 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the electrophotographic photoreceptor described in Patent Document 1 uses titanium oxide, such as rutile titanium oxide, to form a protective layer. Titanium oxide is insoluble in solvents, making it difficult to form a protective layer in which titanium oxide is uniformly dispersed. The inventors' investigations have revealed that if titanium oxide is not uniformly dispersed within the protective layer, charges do not move smoothly within the protective layer, resulting in a decrease in sensitivity characteristics when multiple sheets are printed.

[0005] The present invention has been made in view of the above-mentioned problems, and its object is to provide an electrophotographic photosensitive member, a process cartridge, and an image forming apparatus that have excellent sensitivity characteristics when printing a large number of sheets, and further have excellent initial sensitivity characteristics and wear resistance. [Means for solving the problem]

[0006] The electrophotographic photoreceptor of the present invention comprises a conductive substrate, a photosensitive layer, and a protective layer. The photosensitive layer contains a charge generating agent. The protective layer is the outermost layer of the electrophotographic photoreceptor. The protective layer contains a compound represented by formula (A).

[0007] [ka]

[0008] In the formula (A), R 21 is a hydrogen atom, Li + , or K + represents R 22 and R 23 each independently represents an alkyl group having 1 to 4 carbon atoms substituted with at least one halogen atom.

[0009] The process cartridge of the present invention includes at least one selected from the group consisting of a charging device, an exposure device, a developing device, a transfer device, a cleaning member, a rubbing roller, and a static eliminator, and the electrophotographic photosensitive member.

[0010] The image forming apparatus of the present invention includes an image carrier, a charging device that charges the surface of the image carrier, an exposure device that exposes the charged surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier, a developing device that supplies toner to the surface of the image carrier to develop the electrostatic latent image as a toner image, and a transfer device that transfers the toner image from the image carrier to a transfer recipient. The image carrier is the electrophotographic photosensitive member described above. [Effects of the Invention]

[0011] The electrophotographic photosensitive member, process cartridge, and image forming apparatus of the present invention are excellent in sensitivity characteristics in the initial stage and after printing a large number of sheets, and are also excellent in wear resistance. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a partial cross-sectional view of a single-layer electrophotographic photosensitive member, which is an example of an electrophotographic photosensitive member according to a first embodiment of the present invention. [Figure 2] 1 is a partial cross-sectional view of a single-layer electrophotographic photosensitive member, which is an example of an electrophotographic photosensitive member according to a first embodiment of the present invention. [Figure 3] 1 is a partial cross-sectional view of a multilayer electrophotographic photosensitive member, which is an example of an electrophotographic photosensitive member according to a first embodiment of the present invention. [Figure 4] 1 is a partial cross-sectional view of a multilayer electrophotographic photosensitive member, which is an example of an electrophotographic photosensitive member according to a first embodiment of the present invention. [Figure 5] 1 is a partial cross-sectional view of a multilayer electrophotographic photosensitive member, which is an example of an electrophotographic photosensitive member according to a first embodiment of the present invention. [Figure 6] FIG. 10 is a diagram illustrating an example of an image forming apparatus according to a second embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing an example of the configuration of the developing device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments and can be practiced with appropriate modifications within the scope of the object of the present invention.

[0014] First, the terms used in this specification will be explained. Acrylic and methacrylic may be collectively referred to as "(meth)acrylic." Unless otherwise specified, the hydroxyl value is a value measured in accordance with "JIS (Japanese Industrial Standards) K0070-1992." Unless otherwise specified, the number average primary particle diameter is the number average value of the equivalent circle diameter of primary particles (Heywood diameter: the diameter of a circle having the same area as the projected area of ​​a primary particle) measured using a scanning electron microscope. The number average primary particle diameter is, for example, the number average value of the equivalent circle diameters of 100 primary particles. Unless otherwise specified, the BET specific surface area is a value measured by the BET method using nitrogen adsorption in accordance with "JIS (Japanese Industrial Standards) Z8830:2001 Method for Measuring the Specific Surface Area of ​​Powders (Solids) by Gas Adsorption." The term "based" may be added after the name of a compound to collectively refer to the compound and its derivatives. Furthermore, when the term "based" is added after the name of a compound to indicate the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, "general formula" and "chemical formula" are collectively referred to as "formula." In the explanation of the formula, "each independently" means that they may represent the same group or different groups. "At least one of a, b, and c" and "at least one of a, b, and c" mean "at least one selected from the group consisting of a, b, and c." Note that a, b, and c are examples and may be replaced with other terms as appropriate. Unless otherwise specified, each component described in this specification may be used alone or in combination of two or more. The terms used in this specification have been explained above.

[0015] [First embodiment: electrophotographic photoreceptor] The first embodiment of the present invention relates to an electrophotographic photoreceptor (hereinafter sometimes referred to as a photoreceptor). The photoreceptor of the first embodiment comprises a conductive substrate, a photosensitive layer, and a protective layer. The photosensitive layer contains a charge generating agent. The protective layer is the outermost layer of the photoreceptor. The protective layer contains a compound represented by formula (A). In formula (A), R 21 , R 22 , and R 23 Hereinafter, the "compound represented by formula (A)" may be referred to as the "conductive material (A)".

[0016] [ka]

[0017] By being provided with the above configuration, the photoconductor of the first embodiment has excellent sensitivity characteristics both initially and after printing a large number of sheets, and excellent wear resistance. The reason for this is presumed to be as follows. Hereinafter, the "sensitivity characteristics after printing a large number of sheets" may be referred to as the "repeated sensitivity characteristics."

[0018] Common conductive materials such as tin oxide and zinc oxide are metal oxides, and therefore are difficult to dissolve in the solvent of a coating liquid for forming a protective layer (hereinafter, sometimes referred to as a protective layer coating liquid). In contrast, the conductive material (A) used in the first embodiment is easily soluble in the solvent of the protective layer coating liquid. This makes it possible to prepare a protective layer coating liquid in which the conductive material (A) is dissolved, and to form a protective layer in which the conductive material (A) is uniformly dispersed. As a result, the initial sensitivity characteristics and repeated sensitivity characteristics of the photoreceptor of the first embodiment are improved. In addition, the photoreceptor of the first embodiment has a protective layer on its outermost surface. The protective layer is harder than the photosensitive layer, and therefore the photoreceptor of the first embodiment has excellent abrasion resistance.

[0019] The reasons why the photoreceptor of the first embodiment is excellent in initial sensitivity characteristics, repeated sensitivity characteristics, and abrasion resistance have been explained above. The photoreceptor will be further explained below.

[0020] The photoreceptor is, for example, a single-layer electrophotographic photoreceptor (hereinafter sometimes referred to as a single-layer photoreceptor) or a multi-layer electrophotographic photoreceptor (hereinafter sometimes referred to as a multi-layer photoreceptor).

[0021] The structure of a single-layer photoreceptor 1, which is an example of a photoreceptor, will be described below with reference to FIGS. 1 and 2. Each of FIGS. 1 and 2 shows a partial cross-sectional view of the single-layer photoreceptor 1. As shown in FIG. 1, the single-layer photoreceptor 1 includes, for example, a conductive substrate 2, a photosensitive layer 3, and a protective layer 5. The photosensitive layer 3 is a single layer. Hereinafter, the "single-layer photosensitive layer" may be referred to as a "single-layer photosensitive layer." In the example shown in FIG. 1, a single-layer photosensitive layer 3a is provided on the conductive substrate 2, and a protective layer 5 is provided on the single-layer photosensitive layer 3a. The single-layer photosensitive layer 3a is provided directly on the conductive substrate 2. The protective layer 5 is the outermost layer of the single-layer photoreceptor 1.

[0022] 2, the single-layer photoreceptor 1 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2, the single-layer photosensitive layer 3a, and the protective layer 5. In the example shown in FIG. 2, the intermediate layer 4 is provided on the conductive substrate 2, the single-layer photosensitive layer 3a is provided on the intermediate layer 4, and the protective layer 5 is provided on the single-layer photosensitive layer 3a. The single-layer photosensitive layer 3a is provided on the conductive substrate 2 via the intermediate layer 4.

[0023] The thickness of the single-layer photosensitive layer 3a is not particularly limited, but is preferably from 5 μm to 100 μm, and more preferably from 10 μm to 50 μm.

[0024] The thickness of the protective layer 5 is not particularly limited, but is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 4 μm or less, and particularly preferably 2 μm or more and 4 μm or less. If the thickness of the protective layer 5 is 1 μm or more, the sensitivity characteristics of the photoreceptor are improved. If the thickness of the protective layer 5 is 30 μm or less, the abrasion resistance of the photoreceptor is improved. In the example shown in FIGS. 1 and 2, the protective layer 5 is a single layer. However, the protective layer 5 may be multiple layers. If the protective layer 5 is multiple layers, at least the outermost layer of the multiple layers contains a photocurable resin. The structure of a single-layer photoreceptor 1, which is an example of a photoreceptor, has been described above with reference to FIGS. 1 and 2.

[0025] The structure of a laminated photoreceptor 10, which is an example of a photoreceptor, will be described below with reference to FIGS. 3 to 5. Each of FIGS. 3 to 5 shows a partial cross-sectional view of the laminated photoreceptor 10. As shown in FIG. 3, the laminated photoreceptor 10 includes, for example, a conductive substrate 2, a photosensitive layer 3, and a protective layer 5. The photosensitive layer 3 includes a charge generation layer 3b and a charge transport layer 3c. In the example shown in FIG. 3, the charge generation layer 3b is provided on the conductive substrate 2, the charge transport layer 3c is provided on the charge generation layer 3b, and the protective layer 5 is provided on the charge transport layer 3c. However, as shown in FIG. 4, in the laminated photoreceptor 10, the charge transport layer 3c may be provided on the conductive substrate 2, the charge generation layer 3b on the charge transport layer 3c, and the protective layer 5 on the charge generation layer 3b. In the examples shown in FIGS. 3 and 4, the photosensitive layer 3 is provided directly on the conductive substrate 2. The protective layer 5 is the outermost layer of the multi-layer photoreceptor 10 .

[0026] 5, the multi-layer photoreceptor 10 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2, photosensitive layer 3, and protective layer 5. In the example shown in FIG. 5, the intermediate layer 4 is provided on the conductive substrate 2, the charge generation layer 3b is provided on the intermediate layer 4, the charge transport layer 3c is provided on the charge generation layer 3b, and the protective layer 5 is provided on the charge transport layer 3c. The photosensitive layer 3 (for example, the charge generation layer 3b) is provided on the conductive substrate 2 via the intermediate layer 4.

[0027] The thickness of the charge generation layer 3b is not particularly limited, but is preferably from 0.01 μm to 5 μm, and more preferably from 0.1 μm to 3 μm. In the examples shown in Figures 3 to 5, the charge generation layer 3b is a single layer. However, the charge generation layer 3b may be a multi-layer layer.

[0028] The thickness of the charge transport layer 3c is not particularly limited, but is preferably from 2 μm to 100 μm, and more preferably from 5 μm to 50 μm. In the examples shown in Figures 3 to 5, the charge transport layer 3c is a single layer. However, the charge transport layer 3c may be a multi-layer layer.

[0029] The protective layer 5 of the multi-layer photoreceptor 10 is similar to the protective layer 5 of the single-layer photoreceptor 1, and therefore a description thereof will be omitted. The structure of the multi-layer photoreceptor 10, which is an example of a photoreceptor, has been described above with reference to Figs. 3 to 5.

[0030] <Protective layer> The protective layer contains, for example, a conductive material (A) and a resin. Hereinafter, the "resin contained in the protective layer" may be referred to as the "protective layer resin." The protective layer may further contain at least one of a metal oxide, a polymerization initiator, and an additive, as necessary.

[0031] (Conductive material (A)) As already mentioned, the conductive material (A) is represented by the following formula (A).

[0032] [ka]

[0033] In formula (A), R 21 is a hydrogen atom, Li + , or K + Represents R 22 and R 23 each independently represents an alkyl group having 1 to 4 carbon atoms substituted with at least one halogen atom.

[0034] In order to improve the initial sensitivity and repeat sensitivity characteristics, 21 Li + , or K + It is preferred that

[0035] R 22 and R 23 The alkyl group having 1 to 4 carbon atoms represented by R is, for example, a methyl group, an ethyl group, a propyl group, or a butyl group. 22 and R 23 The alkyl group having 1 to 4 carbon atoms represented by R is substituted with at least one halogen atom. 22 and R 23The alkyl group having 1 to 4 carbon atoms represented by is preferably substituted with 3 to 9 halogen atoms. The alkyl group having 1 to 4 carbon atoms substituted with at least one halogen atom is preferably a perfluoroalkyl group having 1 to 4 carbon atoms, more preferably a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, or a perfluorobutyl group. In order to improve the initial sensitivity characteristics and the repeated sensitivity characteristics, R 22 and R 23 Preferably, one or both of the groups represent a methyl group substituted with at least one halogen atom, and more preferably a trifluoromethyl group.

[0036] Suitable examples of the conductive material (A) include compounds represented by formulas (A-1) to (A-11) (hereinafter, these may be referred to as conductive materials (A-1) to (A-11), respectively).

[0037] [ka]

[0038] The content of the conductive material (A) in the protective layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less, based on the mass of the protective layer.

[0039] (protective layer resin) Examples of the protective layer resin include thermosetting resins and photocurable resins. The protective layer resin is preferably a photocurable resin. Examples of the photocurable resin include (meth)acrylic resins and epoxy resins. The photocurable resin is preferably a (meth)acrylic resin because the photocurable reaction stops when the ultraviolet irradiation is stopped, and the progress of the photocurable reaction is easily controlled.

[0040] The photocurable resin preferably has a repeating unit derived from a compound having one polymerizable functional group and a repeating unit derived from a compound having two or more polymerizable functional groups. Hereinafter, a "repeating unit derived from a compound having one polymerizable functional group" may be referred to as a "monofunctional group unit," and a "compound having one polymerizable functional group" may be referred to as a "monofunctional group monomer." Furthermore, a "repeating unit derived from a compound having two or more polymerizable functional groups" may be referred to as a "polyfunctional group unit," and a "compound having two or more polymerizable functional groups" may be referred to as a "polyfunctional group monomer."

[0041] The photocurable resin containing monofunctional and polyfunctional units offers the following advantages: During the protective layer formation process in photoreceptor manufacturing, the monofunctional monomers for forming the monofunctional units fill the voids in the polyfunctional monomers for forming the polyfunctional units, resulting in the formation of a photocurable resin in which the polyfunctional and monofunctional units are densely arranged. Furthermore, because the polyfunctional monomers contain two or more polymerizable functional groups, the photocuring reaction of the polymerizable functional groups proceeds smoothly during the protective layer formation process in photoreceptor manufacturing. As a result, a protective layer with high hardness can be formed, improving the abrasion resistance of the photoreceptor.

[0042] Examples of polymerizable functional groups contained in the monofunctional group unit and the polyfunctional group unit include vinyl groups and epoxy groups. When the photocurable resin is a (meth)acrylic resin, the (meth)acrylic resin has a vinyl group as a polymerizable functional group. When the photocurable resin is an epoxy resin, the epoxy resin has an epoxy group as a polymerizable functional group.

[0043] The photocurable resin may have one type of monofunctional group unit, or two or more (e.g., two) types of monofunctional group units. The photocurable resin may have one type of polyfunctional group unit, or two or more (e.g., two or three) types of polyfunctional group units.

[0044] The monofunctional group unit of the photocurable resin will be described below. The monofunctional group unit preferably further has a group containing a halogen atom in addition to one polymerizable functional group. The conductive material (A) has a halogen atom. Therefore, when the monofunctional group unit has a group containing a halogen atom, the compatibility between the conductive material (A) and the monofunctional group monomer is improved in the preparation of the coating liquid for the protective layer, and a protective layer in which the conductive material (A) is more uniformly dispersed can be formed.

[0045] Examples of the group containing a halogen atom include a fluoro group, a chloro group, a bromo group, an iodo group, a trichloromethyl group, and a group represented by formula (b1). In order to favorably harden the protective layer and improve the abrasion resistance of the photoreceptor, the group containing a halogen atom is preferably a group represented by formula (b1).

[0046] [ka]

[0047] In formula (b1), m represents 0 or 1. n represents an integer of 1 or more and 3 or less. R 3 represents a hydrogen atom or a fluorine atom. * represents a bond. In formula (b1), m preferably represents 1. n preferably represents 1 or 3. R 3 preferably represents a hydrogen atom.

[0048] A suitable example of the monofunctional group unit is a repeating unit derived from a compound represented by formula (EB-1).

[0049] [ka]

[0050] In formula (EB-1), R 1 represents a group represented by formula (b1), and R 2 represents a hydrogen atom or a methyl group. 2 preferably represents a hydrogen atom.

[0051] A monofunctional unit is formed by polymerizing the polymerizable functional group of the monofunctional monomer. For example, a compound represented by formula (EB-1), which is a monofunctional monomer, is subjected to a photocuring reaction (more specifically, an addition polymerization reaction of a vinyl group) to form a repeating unit represented by formula (EB-1a), which is a monofunctional unit.

[0052] [ka]

[0053] * in formula (EB-1a) 3 represents a bond, more specifically, represents a bond that bonds to another repeating unit. 1 and R 2 is R in formula (EB-1) 1 and R 2 is synonymous with.

[0054] The compound represented by formula (EB-1) is preferably a compound represented by formula (C-3), (C-4), or (C-6).

[0055] [ka]

[0056] Next, the polyfunctional group unit of the photocurable resin will be described. The polyfunctional group unit is preferably a repeating unit derived from a compound having 2 to 10 polymerizable functional groups, and more preferably a repeating unit derived from a compound having 3 to 6 polymerizable functional groups. Examples of the polymerizable functional group possessed by the polyfunctional group unit include the same polymerizable functional groups as the examples of the polymerizable functional groups possessed by the monofunctional group unit already described. The polyfunctional group unit of the photocurable resin may or may not have a group containing a halogen atom.

[0057] Examples of polyfunctional monomers for forming the polyfunctional unit include trimethylolpropane triacrylate, glycerin triacrylate, tris-(2-acryloxyethyl)isocyanurate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate. These polyfunctional monomers may be ethoxylated.

[0058] The polyfunctional monomer is preferably at least one selected from the group consisting of pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate, and more preferably one or two selected from the group consisting of pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

[0059] The above-mentioned pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate are compounds represented by the following formulae (EA-1), (EA-2), (EA-3), and (EA-4), respectively. Therefore, the polyfunctional group unit is preferably a repeating unit derived from at least one selected from the group consisting of compounds represented by formulae (EA-1), (EA-2), (EA-3), and (EA-4), and more preferably a repeating unit derived from one or two of these. The polyfunctional group unit is even more preferably a repeating unit derived from at least one selected from the group consisting of compounds represented by formulae (EA-3) and (EA-4), and particularly preferably a repeating unit derived from two of these.

[0060] [ka]

[0061] Polyfunctional units are formed by polymerizing the polymerizable functional groups of polyfunctional monomers. For example, by a photocuring reaction (more specifically, an addition polymerization reaction of vinyl groups), polyfunctional monomer compounds represented by formulae (EA-1), (EA-2), (EA-3), and (EA-4) are respectively converted into polyfunctional units represented by formulae (EA-1a), (EA-2a), (EA-3a), and (EA-4a).

[0062] [ka]

[0063] Y in formula (EA-1a) 1 ~Y 3 At least one of the groups represented by formula (Yb) is 1 ~Y 3 The remainder of the above represents a group represented by formula (Ya). 4 ~Y 7 At least one of the groups represented by formula (Yb) is 4 ~Y 7 The remainder of the above represents a group represented by formula (Ya). 8 ~Y 12 At least one of the groups represented by formula (Yb) is 8 ~Y 12 The remainder of the above represents a group represented by formula (Ya). 13 ~Y 18 At least one of the groups represented by formula (Yb) is 13 ~Y 18 The remainder represents a group represented by formula (Ya).

[0064] [ka]

[0065] * in formulas (Ya) and (Yb) 1is a bond bonded to the carbon atom of the carbonyl group in formulae (EA-1a) to (EA-4a). 2 represents a bond, more specifically, a bond that bonds to another repeating unit.

[0066] The photocuring reaction (more specifically, the addition polymerization reaction of the vinyl group) cleaves the double bond of the group represented by formula (Ya), forming a group represented by formula (Yb). Therefore, as the photocuring reaction (more specifically, the addition polymerization reaction of the vinyl group) progresses, the group represented by formula (Ya) decreases and the group represented by formula (Yb) increases.

[0067] The polyfunctional monomer is preferably a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate. The content of pentaerythritol triacrylate in the mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate is preferably 40% by mass or more and 60% by mass or less. The polyfunctional monomer is also preferably a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate.

[0068] The hydroxyl value of the polyfunctional monomer is preferably 1 mgKOH / g or more and 50 mgKOH / g or less, and more preferably 5 mgKOH / g or more and 15 mgKOH / g or less.

[0069] In order to allow the monofunctional monomer to suitably infiltrate the voids in the polyfunctional monomer and form a photocurable resin in which the polyfunctional unit and the monofunctional unit are densely arranged, the polyfunctional unit is preferably larger than the monofunctional unit. For the same reason, the molecular weight of the polyfunctional monomer is preferably higher than the molecular weight of the monofunctional monomer.

[0070] In order to promote the photocuring reaction and increase the hardness of the protective layer, the ratio M4 / M3 of the mass M4 of the monofunctional group unit to the mass M3 of the polyfunctional group unit is preferably 0.1 or more and 0.9 or less, more preferably 0.5 or more and 0.8 or less, and even more preferably 0.6 or more and 0.7 or less.

[0071] The content of polyfunctional group units in all repeating units of the photocurable resin is preferably 50% by mass or more and 90% by mass or less, and more preferably 60% by mass or more and 70% by mass or less. The content of monofunctional group units in all repeating units of the photocurable resin is preferably 10% by mass or more and 50% by mass or less, and more preferably 30% by mass or more and 40% by mass or less. The total content of polyfunctional group units and monofunctional group units in all repeating units of the photocurable resin is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 98% by mass or more and 99% by mass or less.

[0072] The content of the photocurable resin in the protective layer is preferably 50% by mass or more and 99% by mass or less, and more preferably 70% by mass or more and 90% by mass or less, based on the mass of the protective layer.

[0073] (metal oxides) Examples of metal oxides include alumina, zinc oxide, titanium oxide, and tin oxide. The metal oxide may be undoped. However, to increase the conductivity of the protective layer, the metal oxide is preferably doped. Examples of doped metal oxides include phosphorus-doped tin oxide and antimony-doped tin oxide. Alumina is preferred as the metal oxide. To improve the repeated use sensitivity of the photoreceptor, the protective layer preferably does not contain at least one of tin oxide, titanium oxide, and zinc oxide.

[0074] When the protective layer contains a metal oxide, the content of the conductive material (A) in the conductive material (A) and the metal oxide in the protective layer is preferably 60% by mass or more but less than 100% by mass, more preferably 70% by mass or more but 90% by mass or less, and even more preferably 75% by mass or more but 85% by mass or less, relative to the total mass of the conductive material (A) and the metal oxide. The content of the metal oxide in the protective layer is preferably 0.1% by mass or more but 10% by mass or less, more preferably 0.1% by mass or more but 3% by mass or less, relative to the mass of the protective layer.

[0075] (Polymerization initiator) The polymerization initiator is, for example, a photopolymerization initiator. Examples of photopolymerization initiators include acylphosphine oxide compounds, acetophenone compounds, ketal compounds, benzoin ether compounds, anthraquinone compounds, and thioxanthone compounds. Acylphosphine oxide compounds are preferred as photopolymerization initiators because of their high ultraviolet absorption efficiency. Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and lithium phenyl(2,4,6-trimethylbenzoyl)phosphonate. The content of the polymerization initiator in the protective layer is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 10% by mass or less, relative to the mass of the protective layer.

[0076] (additives) Additives contained in the protective layer include, for example, leveling agents and other known additives. As the leveling agent, a leveling agent having a halogen atom is preferred, an acrylic polymer having a halogen atom is more preferred, a fluorine silicone-modified acrylic polymer is even more preferred, and a UV-curable fluorine silicone-modified acrylic polymer is particularly preferred. The leveling agent may have a polymerizable functional group. When the leveling agent has a polymerizable functional group, the photocurable resin has a repeating unit derived from the leveling agent as a repeating unit. When the leveling agent has a polymerizable functional group, the polymerizable functional group equivalent (e.g., vinyl group equivalent) of the leveling agent is preferably 100 g / mol or more and 500 g / mol or less, more preferably 260 g / mol or more and 450 g / mol or less. It is preferable that the protective layer does not contain a charge generating agent, a hole transport agent, or an electron transport agent.

[0077] <Photosensitive layer> The photosensitive layer contains, for example, a charge generating agent, a hole transport agent, and a binder resin. When the photoreceptor is a single-layer photoreceptor, the single-layer photosensitive layer, which is the photosensitive layer, contains a charge generating agent, a hole transport agent, and a binder resin. The single-layer photosensitive layer preferably further contains an electron transport agent. The single-layer photosensitive layer may further contain additives as necessary.

[0078] When the photoreceptor is a multilayer photoreceptor, the charge generation layer included in the photosensitive layer contains a charge generating agent. The charge transport layer included in the photosensitive layer contains a hole transport agent and a binder resin. The charge generation layer may further contain a base resin, if necessary. The charge generation layer and the charge transport layer may each further contain an additive, if necessary. The charge generation layer and the charge transport layer may each contain a radical acceptor compound. However, the charge generation layer and the charge transport layer do not necessarily need to contain a radical acceptor compound.

[0079] (charge generating material) Examples of the charge generating agent include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, indigo pigments, azulenium pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g., selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon), pyrylium pigments, anthanthrone pigments, triphenylmethane pigments, threne pigments, toluidine pigments, pyrazoline pigments, and quinacridone pigments.

[0080] The phthalocyanine pigment has a phthalocyanine structure. Examples of the phthalocyanine pigment include metal phthalocyanine and metal-free phthalocyanine. Examples of the metal phthalocyanine include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. As the metal phthalocyanine, titanyl phthalocyanine is preferred. Titanyl phthalocyanine is represented by formula (CG-1). Metal-free phthalocyanine is represented by formula (CG-2).

[0081] [ka]

[0082] The phthalocyanine pigment may be crystalline or amorphous. Examples of metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter, sometimes referred to as X-type metal-free phthalocyanine). Examples of titanyl phthalocyanine crystals include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter, sometimes referred to as α-type, β-type, and Y-type titanyl phthalocyanine, respectively).

[0083] For example, a photoreceptor having sensitivity in the wavelength region of 700 nm or more is preferably used in a digital optical image forming apparatus (for example, a laser beam printer or a facsimile machine using a light source such as a semiconductor laser). As the charge generating agent, a phthalocyanine pigment is preferred because it has a high quantum yield in the wavelength region of 700 nm or more, with titanyl phthalocyanine or metal-free phthalocyanine being more preferred, and Y-type titanyl phthalocyanine or X-type metal-free phthalocyanine being particularly preferred.

[0084] The Y-type titanyl phthalocyanine has a main peak at a Bragg angle (2θ±0.2°) of 27.2° in its CuKα characteristic X-ray diffraction spectrum. The main peak in a CuKα characteristic X-ray diffraction spectrum is the peak with the first or second highest intensity in the Bragg angle (2θ±0.2°) range of 3° to 40°. The Y-type titanyl phthalocyanine does not have a peak at 26.2° in its CuKα characteristic X-ray diffraction spectrum.

[0085] The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, a sample (titanyl phthalocyanine) is loaded into a sample holder of an X-ray diffractometer (e.g., Rigaku Corporation's "RINT (registered trademark) 1100"), and the X-ray diffraction spectrum is measured under the conditions of a Cu X-ray tube, a tube voltage of 40 kV, a tube current of 30 mA, and a CuKα characteristic X-ray wavelength of 1.542 Å. The measurement range (2θ) is, for example, 3° to 40° (start angle 3°, stop angle 40°), and the scanning speed is, for example, 10° / min. The main peak is determined from the obtained X-ray diffraction spectrum, and the Bragg angle of the main peak is read.

[0086] When the photoreceptor is a single-layer photoreceptor, the content of the charge generating agent in the single-layer photoreceptor, which is the photosensitive layer, is preferably 0.1 to 50 parts by mass, and more preferably 0.5 to 30 parts by mass, relative to 100 parts by mass of the binder resin. When the photoreceptor is a multi-layer photoreceptor, the content of the charge generating agent in the photosensitive layer (specifically, the charge generating layer) is preferably 10 to 300 parts by mass, and more preferably 100 to 200 parts by mass, relative to 100 parts by mass of the base resin.

[0087] (hole transport agent) Examples of the hole transport agent include triphenylamine derivatives, diamine derivatives (e.g., N,N,N',N'-tetraphenylbenzidine derivatives, N,N,N',N'-tetraphenylphenylenediamine derivatives, N,N,N',N'-tetraphenylnaphthylenediamine derivatives, N,N,N',N'-tetraphenylphenanthrylenediamine derivatives, and di(aminophenylethenyl)benzene derivatives), oxadiazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazo Examples of the compound include phenylalanine compounds, styryl compounds (e.g., 9-(4-diethylaminostyryl)anthracene), carbazole compounds (e.g., polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (e.g., 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

[0088] In order to improve the sensitivity characteristics of the photoreceptor, the hole transport agent preferably contains at least one of the compounds represented by formulas (1), (2), and (3). Hereinafter, the compounds represented by formulas (1), (2), and (3) may be referred to as hole transport agents (1), (2), and (3), respectively.

[0089] [ka]

[0090] In formula (1), R 41 , R 42 , R 43 , R 44 , R 45 , and R 46 R each independently represents an alkyl group having 1 to 8 carbon atoms or a phenyl group. 47 and R 48 each independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group. e1, e2, e3, and e4 each independently represent an integer of 0 to 5. e5 and e6 each independently represent an integer of 0 to 4.

[0091] In formula (1), when e1 represents an integer of 2 or more and 5 or less, a plurality of R 41 may represent the same group or different groups. When e2 represents an integer of 2 or more and 5 or less, multiple R 42 may represent the same group or different groups. When e3 represents an integer of 2 or more and 5 or less, multiple R 43 may represent the same group or different groups. When e4 represents an integer of 2 or more and 5 or less, multiple R 44 may represent the same group or different groups. When e5 represents an integer of 2 or more and 4 or less, multiple R 45 may represent the same group or different groups. When e6 represents an integer of 2 or more and 4 or less, multiple R 46 may represent the same group or different groups.

[0092] In formula (1), R 41 ~R 46 R preferably each independently represents an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group or an ethyl group. 47 and R 48preferably represents a hydrogen atom. e1, e2, e3, and e4 each independently represent an integer of 0 to 2, more preferably e1 and e2 represent 0 and e3 and e4 represent 2. e5 and e6 preferably represent 0.

[0093] In formula (2), R 50 , R 51 , and R 54 R each independently represents an alkyl group having 1 to 8 carbon atoms or a phenyl group. 52 , and R 53 each independently represents a hydrogen atom, an alkyl group having from 1 to 8 carbon atoms, or a phenyl group which may be substituted with an alkyl group having from 1 to 8 carbon atoms. f3, f4, and f5 each independently represent an integer of from 0 to 5.

[0094] In formula (2), when f3 represents an integer of 2 or more and 5 or less, a plurality of R 50 may represent the same group or different groups. When f4 represents an integer of 2 or more and 5 or less, multiple R 51 may represent the same group or different groups. When f5 represents an integer of 2 or more and 5 or less, multiple R 54 may represent the same group or different groups.

[0095] In formula (2), R 50 , R 51 , and R 54 R each independently preferably represents an alkyl group having 1 to 8 carbon atoms, more preferably represents an alkyl group having 1 to 3 carbon atoms, and further preferably represents a methyl group. 52 and R 53 preferably each independently represent a hydrogen atom, an unsubstituted phenyl group, or a phenyl group substituted with an alkyl group having from 1 to 8 carbon atoms. When the phenyl group is substituted with an alkyl group having from 1 to 8 carbon atoms, the alkyl group having from 1 to 8 carbon atoms is preferably an alkyl group having from 1 to 3 carbon atoms, more preferably a methyl group. preferably each independently represent 0 or 1.

[0096] In formula (3), R 11 , R 12 , R 13 , and R 14 each independently represents an alkyl group having 1 to 8 carbon atoms or a phenyl group; a1, a2, a3, and a4 each independently represents an integer of 0 to 5;

[0097] In formula (3), when a1 represents an integer of 2 or more and 5 or less, a plurality of R 11 may represent the same group or different groups. When a2 represents an integer of 2 or more and 5 or less, multiple R 12 may represent the same group or different groups. When a3 represents an integer of 2 or more and 5 or less, multiple R 13 may represent the same group or different groups. When a4 represents an integer of 2 or more and 5 or less, multiple R 14 may represent the same group or different groups.

[0098] In formula (3), R 11 , R 12 , R 13 , and R 14 each independently preferably represents an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group or an ethyl group. a1, a2, a3, and a4 each independently preferably represent an integer of 1 to 3, more preferably 1.

[0099] Suitable examples of the hole transport agent include compounds represented by formulae (HT-2), (HT-3), and (HT-4) (hereinafter, these may be referred to as hole transport agents (HT-2), (HT-3), and (HT-4), respectively.) The photosensitive layer preferably contains one or both of the hole transport agents (HT-2) and (HT-3) as the hole transport agent.

[0100] [ka]

[0101] The content of the hole transport agents (1) to (3) in the total mass of the hole transport agents in the photosensitive layer is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 100 mass% relative to the total mass of the hole transport agents in the photosensitive layer.

[0102] When ultraviolet irradiation is performed in the protective layer forming step, in order to suppress decomposition of the hole transport agent due to ultraviolet irradiation, it is preferable that the hole transport agent has two or less (one or two) chain ethene-1,2-diyl groups or does not have any chain ethene-1,2-diyl groups. Hereinafter, a "chain ethene-1,2-diyl group" may be referred to as a "predetermined double bond." The predetermined double bond is a bond represented by the following formula (DB). In formula (DB), * represents a bond. The predetermined double bond is an unsubstituted ethene-1,2-diyl group. Since the predetermined double bond is a chain, it is a double bond that constitutes a chain group. Since the predetermined double bond is a chain, it is not a double bond that constitutes a ring such as a benzene ring.

[0103] [ka]

[0104] When ultraviolet irradiation is performed in the protective layer formation step, in order to suppress decomposition of the hole transport agent due to ultraviolet irradiation, the content of hole transport agents having two or less specified double bonds or having no specified double bonds in the total mass of the hole transport agents in the photosensitive layer is preferably 80 mass% or more, more preferably 90 mass% or more, and even more preferably 100 mass% relative to the total mass of the hole transport agents.

[0105] When the photoreceptor is a single-layer photoreceptor, the content of the hole transport agent in the single-layer photoreceptor, which is the photosensitive layer, is preferably 10 parts by mass or more and 200 parts by mass or less, and more preferably 80 parts by mass or more and 130 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0106] In order to improve the sensitivity characteristics of the photoreceptor, when the photoreceptor is a single-layer photoreceptor, the total content of the hole transport agent and the electron transport agent in the single-layer photosensitive layer is preferably 40% by mass or more, and more preferably 40% by mass or more and 60% by mass or less, relative to the mass of the single-layer photosensitive layer.

[0107] When the photoreceptor is a laminated photoreceptor, the content of the hole transport agent in the photosensitive layer (specifically, the charge transport layer) is preferably 10 parts by mass or more and 200 parts by mass or less, and more preferably 50 parts by mass or more and 100 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0108] In order to improve the sensitivity characteristics of the photoreceptor, when the photoreceptor is a laminated photoreceptor, the content of the hole transport agent in the charge transport layer is preferably 40.0 mass % or more, and more preferably 40.0 mass % or more and 60.0 mass % or less, relative to the mass of the charge transport layer.

[0109] (electron transport agent) Examples of electron transport agents include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride. Examples of quinone compounds include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds.

[0110] The electron transport agent preferably contains at least one of the compounds represented by formulas (11), (12), (13), (14), (15), and (16). Hereinafter, the compounds represented by formulas (11), (12), (13), (14), (15), and (16) may be referred to as electron transport agents (11), (12), (13), (14), (15), and (16), respectively.

[0111] [ka]

[0112] Q in equation (11) 1 and Q 2 , Q in Eq. (12) 21 , Q 22 , Q 23 , and Q 24 , Q in Eq. (13) 31 and Q 32 , Q in Eq. (14) 41 , Q 42 , and Q 43 , Q in Eq. (15) 71 , Q 72 , Q 73 , Q 74 , Q 75 , and Q 76 , and Q in equation (16) 61 and Q 62 each independently represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group having from 1 to 6 carbon atoms, an alkenyl group having from 2 to 6 carbon atoms, an alkoxy group having from 1 to 6 carbon atoms, or an aryl group having from 6 to 14 carbon atoms which may be substituted with at least one substituent selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms and a halogen atom. 1 and Y 2 represents an oxygen atom.

[0113] Q in equation (11) 1 and Q 2 , Q in Eq. (12) 21 , Q 22 , Q 23 , and Q 24 , Q in Eq. (13)31 and Q 32 , Q in Eq. (14) 41 , Q 42 , and Q 43 , Q in Eq. (15) 71 , Q 72 , Q 73 , Q 74 , Q 75 , and Q 76 , and Q in equation (16) 61 and Q 62 preferably each independently represents a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, or an aryl group having from 6 to 14 carbon atoms which may be substituted with at least one substituent selected from the group consisting of an alkyl group having from 1 to 6 carbon atoms and a halogen atom.

[0114] Q in equation (11) 1 and Q 2 , Q in Eq. (12) 21 , Q 22 , Q 23 , and Q 24 , Q in Eq. (13) 31 and Q 32 , Q in Eq. (14) 41 , Q 42 , and Q 43 , Q in Eq. (15) 71 , Q 72 , Q 73 , Q 74 , Q 75 , and Q 76 , and Q in equation (16) 61 and Q 62 The alkyl group having 1 to 6 carbon atoms represented by is preferably an alkyl group having 1 to 5 carbon atoms, more preferably a methyl group, an ethyl group, a propyl group, a butyl group, or a pentyl group, and particularly preferably a methyl group, a tert-butyl group, or a 1,1-dimethylpropyl group.

[0115] Q in equation (11) 1 and Q 2 , Q in Eq. (12) 21 , Q 22 , Q 23 , and Q 24 , Q in Eq. (13)31 and Q 32 , Q in Eq. (14) 41 , Q 42 , and Q 43 , Q in Eq. (15) 71 , Q 72 , Q 73 , Q 74 , Q 75 , and Q 76 , and Q in equation (16) 61 and Q 62 The aryl group having 6 to 14 carbon atoms represented by is preferably an aryl group having 6 to 10 carbon atoms, more preferably a phenyl group. The aryl group having 6 to 14 carbon atoms may be substituted with at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms and a halogen atom. As such an alkyl group having 1 to 6 carbon atoms, an alkyl group having 1 to 3 carbon atoms is preferred, and a methyl group or an ethyl group is more preferred. As the halogen atom substituent, a fluorine atom, a chlorine atom, or a bromine atom is preferred, and a chlorine atom is particularly preferred. When an aryl group having 6 to 14 carbon atoms is substituted with a substituent, the number of substituents is preferably one to five, more preferably one or two. As the aryl group having 6 to 14 carbon atoms and substituted with at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms and a halogen atom, a chlorophenyl group, a dichlorophenyl group, or an ethylmethylphenyl group is preferred, and a 4-chlorophenyl group, a 2,5-dichlorophenyl group, or a 2-ethyl-6-methylphenyl group is more preferred.

[0116] More preferred examples of the electron transfer agent include compounds represented by formulas (ET-1) to (ET-7) (hereinafter, these may be referred to as electron transfer agents (ET-1) to (ET-7), respectively).

[0117] [ka]

[0118] The content of the electron transport agents (11) to (16) in the total mass of the electron transport agents in the photosensitive layer is preferably 80 mass % or more, more preferably 90 mass % or more, and even more preferably 100 mass %, based on the total mass of the electron transport agents in the photosensitive layer.

[0119] When the photoreceptor is a single-layer photoreceptor, the content of the electron transport agent in the single-layer photoreceptor, which is the photosensitive layer, is preferably 5 parts by mass or more and 150 parts by mass or less, and more preferably 10 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0120] (binder resin) Examples of binder resins include thermoplastic resins (more specifically, polyarylate resins, polycarbonate resins, styrene-based resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, styrene-acrylic acid copolymers, acrylic copolymers, polyethylene resins, ethylene-vinyl acetate copolymers, chlorinated polyethylene resins, polyvinyl chloride resins, polypropylene resins, ionomers, vinyl chloride-vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyvinyl acetal resins, and polyether resins), thermosetting resins (more specifically, silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, and other crosslinkable thermosetting resins), and photocurable resins (more specifically, epoxy-acrylic acid based resins and urethane-acrylic acid based copolymers).

[0121] Among these resins, polycarbonate resins are preferred because they can provide single-layer photosensitive layers and charge transport layers that are excellent in balance between processability, mechanical strength, optical properties, and abrasion resistance. Examples of polycarbonate resins include bisphenol Z polycarbonate resins, bisphenol B polycarbonate resins, bisphenol ZC polycarbonate resins, bisphenol C polycarbonate resins, and bisphenol A polycarbonate resins. As the binder resin, bisphenol Z polycarbonate resins or bisphenol B polycarbonate resins are preferred. Bisphenol Z polycarbonate resins are resins having a repeating unit represented by the formula (BisZ). Bisphenol B polycarbonate resins are resins having a repeating unit represented by the formula (BisB).

[0122] [ka]

[0123] (base resin) Examples of the base resin contained in the charge generating layer are the same as the examples of the binder resin contained in the charge transport layer. However, in order to suitably form the charge generating layer and the charge transport layer, it is preferable to select a resin different from the resin used as the binder resin from the examples of the binder resins described above as the base resin. The base resin is, for example, a polyvinyl acetal resin.

[0124] (additives) Examples of additives contained in the photosensitive layer include ultraviolet absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, donors, surfactants, plasticizers, sensitizers, electron acceptor compounds, and leveling agents. Examples of leveling agents include silicone oil, more specifically dimethyl silicone oil.

[0125] <Middle class> The presence of the intermediate layer maintains an insulating state sufficient to suppress leakage, while facilitating the flow of current generated when the photoreceptor is exposed to light, thereby suppressing an increase in resistance. The intermediate layer (undercoat layer) contains, for example, one or both of inorganic particles and organic particles, and a resin used in the intermediate layer (hereinafter sometimes referred to as "intermediate layer resin"). Hereinafter, the inorganic particles and organic particles contained in the intermediate layer will be collectively referred to as intermediate layer particles. The ratio of the mass of the intermediate layer particles to the mass of the intermediate layer resin is, for example, 1 or more and 4 or less. The thickness of the intermediate layer is, for example, 0.1 μm or more and 5 μm or less.

[0126] Examples of inorganic particles for the intermediate layer include white pigments (more specifically, titanium oxide, zinc oxide, zinc oxide, zinc sulfide, white lead, and lithopone) and extender pigments (more specifically, alumina, calcium carbonate, and barium sulfate). Examples of organic particles for the intermediate layer include fluororesin particles, benzoguanamine resin particles, and styrene resin particles. The number-average primary particle size of the particles for the intermediate layer is preferably 100 nm or less, and more preferably 1 nm or more and 50 nm or less. The particles for the intermediate layer are preferably inorganic particles, and more preferably titanium oxide. Titanium oxide may be surface-treated. The surface treatment of titanium oxide may be performed once or multiple times (for example, twice). Examples of surface treatment agents used for the surface treatment of titanium oxide include alumina, silica, and organosilicon compounds (for example, polysiloxane, more specifically, methylhydrogenpolysiloxane).

[0127] Examples of the resin for the intermediate layer are the same as the examples of the binder resin contained in the photosensitive layer. However, in order to form the photosensitive layer favorably, it is preferable to select a resin for the intermediate layer that is different from the resin used as the binder resin among the examples of the binder resins described above. The resin for the intermediate layer is, for example, a polyamide resin.

[0128] <Conductive substrate> The conductive substrate is not particularly limited, as long as at least the surface portion is made of a conductive material. An example of a conductive substrate is a conductive substrate made of a conductive material. Another example of a conductive substrate is a conductive substrate coated with a conductive material. Examples of conductive materials include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, and indium. Two or more conductive materials may be combined and used as alloys (more specifically, aluminum alloys, stainless steel, brass, etc.). Aluminum and aluminum alloys are preferred as conductive materials because they facilitate good charge transfer from the photosensitive layer to the conductive substrate. The shape of the conductive substrate is appropriately selected according to the structure of the image forming apparatus. Examples of the shape of the conductive substrate include a sheet shape and a drum shape. The thickness of the conductive substrate is also appropriately selected according to the shape of the conductive substrate.

[0129] <Photoreceptor manufacturing method> Next, a description will be given of a method for manufacturing the photoreceptor of the first embodiment. The method for manufacturing the photoreceptor of the first embodiment includes, for example, a photosensitive layer forming step and a protective layer forming step.

[0130] (Photosensitive layer formation process for single-layer photoreceptor) The photosensitive layer forming process for a single-layer photosensitive body will be described. The photosensitive layer forming process for a single-layer photosensitive body includes a single-layer photosensitive layer forming step. In the single-layer photosensitive layer forming step, a coating liquid for forming a single-layer photosensitive layer (hereinafter, sometimes referred to as a single-layer photosensitive layer coating liquid) is prepared. The single-layer photosensitive layer coating liquid contains, for example, a charge generating agent, a hole transport agent, a binder resin, a solvent, and optionally an electron transport agent and optionally an additive. The single-layer photosensitive layer coating liquid is prepared by mixing these components. Next, the single-layer photosensitive layer coating liquid is applied onto a conductive substrate. Next, at least a portion of the solvent contained in the applied photosensitive layer coating liquid is removed to form a single-layer photosensitive layer.

[0131] (Photosensitive layer formation process for laminated photoreceptor) The photosensitive layer forming process for a multi-layer photoreceptor will be described below: The photosensitive layer forming process for a multi-layer photoreceptor includes a charge generating layer forming process and a charge transport layer forming process.

[0132] In the charge generation layer forming step, a coating liquid for forming the charge generation layer (hereinafter sometimes referred to as a charge generation layer coating liquid) is prepared. The charge generation layer coating liquid contains, for example, a charge generating agent, a base resin, a solvent, and, if necessary, additives. The charge generation layer coating liquid is prepared by mixing these. Next, the charge generation layer coating liquid is applied onto a conductive substrate. Next, at least a portion of the solvent contained in the applied charge generation layer coating liquid is removed to form a charge generation layer.

[0133] In the charge transport layer forming step, a coating liquid for forming the charge transport layer (hereinafter sometimes referred to as a charge transport layer coating liquid) is prepared. The charge transport layer coating liquid contains a hole transport agent, a binder resin, a solvent, and, if necessary, additives. The charge transport layer coating liquid is prepared by mixing these. Next, the charge transport layer coating liquid is applied onto the charge generating layer. Next, at least a portion of the solvent contained in the applied charge transport layer coating liquid is removed to form a charge transport layer.

[0134] (Protective layer formation process) In the protective layer forming step, a protective layer is formed on the photosensitive layer. First, a coating liquid for forming the protective layer (hereinafter sometimes referred to as protective layer coating liquid) is prepared. The protective layer coating liquid contains tin oxide particles, alumina particles, at least one compound for forming the protective layer resin, a solvent, and optionally a polymerization initiator and optionally an additive. The protective layer coating liquid is prepared by mixing these components. Next, the protective layer coating liquid is applied onto the photosensitive layer. Next, at least one compound for forming the protective layer resin contained in the protective layer coating liquid on the photosensitive layer is polymerized. By polymerization, a polymerized protective layer resin is formed.

[0135] When the protective layer resin is a photocurable resin, at least one of the compounds contained in the protective layer coating liquid for forming the protective layer is polymerized by irradiating the protective layer coating liquid with ultraviolet light. The ultraviolet light irradiated in the protective layer forming step is, for example, irradiated from a light-emitting diode light source. To ensure that the photocuring reaction proceeds smoothly, the wavelength of the ultraviolet light irradiated in the protective layer forming step is preferably 200 nm or more and 420 nm or less, more preferably 270 nm or more and 420 nm or less, and even more preferably 365 nm. The optical energy of the ultraviolet light irradiated in the protective layer forming step is preferably 10,000 mW·s or more and 100,000 mW·s or less, more preferably 60,300 mW·s or more and 86,400 mW·s or less. When the ultraviolet light energy is 10,000 mW·s or more, the photocuring reaction proceeds sufficiently, and the protective layer can be sufficiently cured. If the power is 100,000 mW·s or less, the decomposition of the hole transport agent contained in the photosensitive layer can be further suppressed, and the sensitivity characteristics of the photoreceptor can be improved.

[0136] The photosensitive layer forming step and the protective layer forming step have been described above. The method for manufacturing the photoreceptor of the first embodiment will now be described in further detail.

[0137] The solvent contained in the coating liquid for the single-layer type photosensitive layer, the coating liquid for the charge generating layer, the coating liquid for the charge transport layer, and the coating liquid for the protective layer (hereinafter, these may be collectively referred to as coating liquids) is not particularly limited as long as it can dissolve or disperse each component contained in the coating liquid. Examples of solvents include alcohols (more specifically, methanol, ethanol, isopropanol, and butanol), aliphatic hydrocarbons (more specifically, n-hexane, octane, and cyclohexane), aromatic hydrocarbons (more specifically, benzene, toluene, and xylene), halogenated hydrocarbons (more specifically, methylene chloride, chloroform, ethylene chloride, dichloromethane, dichloroethane, carbon tetrachloride, and chlorobenzene), ethers (more specifically, dioxane, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, and diethylene glycol dimethyl ether), ketones (more specifically, acetone, methyl ethyl ketone, 2-butanone, and cyclohexanone), esters (more specifically, ethyl acetate and methyl acetate), dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide.

[0138] The coating solution is prepared by mixing the respective components and dissolving or dispersing them in a solvent. For mixing, a bead mill, a ball mill, a roll mill, a paint shaker, or an ultrasonic disperser can be used, for example.

[0139] The method for applying the coating liquid is not particularly limited as long as it can uniformly apply the coating liquid, and examples of the coating method include dip coating, spray coating, bead coating, blade coating, and roller coating.

[0140] Methods for removing at least a portion of the solvent contained in the coating liquid for the single-layer photosensitive layer, the coating liquid for the charge generating layer, and the coating liquid for the charge transport layer include, for example, heating, reducing pressure, or a combination of heating and reducing pressure. More specifically, a method of heat treatment (hot air drying) using a high-temperature dryer or a reduced-pressure dryer is included. The heat treatment temperature is, for example, 40°C or higher and 150°C or lower. The heat treatment time is, for example, 3 minutes or higher and 150 minutes or lower.

[0141] The method for producing a photoreceptor according to the first embodiment may further include an intermediate layer forming step of forming an intermediate layer on the conductive substrate, as required. The intermediate layer forming step may be carried out by appropriately selecting a known method.

[0142] [Second embodiment: image forming apparatus] Next, an image forming apparatus 100, which is an example of an image forming apparatus according to a second embodiment of the present invention, will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of the configuration of the image forming apparatus 100. The image forming apparatus 100 is, for example, a tandem color printer.

[0143] As shown in FIG. 6, the image forming apparatus 100 includes a control unit 15, an operation unit 20, a paper feed unit 30, a conveyance unit 40, a toner supply unit 50, an image forming unit 60, a transfer device 70, a fixing device 80, and a discharge unit 90.

[0144] The control unit 15 controls the operation of each unit included in the image forming apparatus 100. The control unit 15 includes a processor (not shown) and a storage unit (not shown). The processor includes, for example, a CPU (Central Processing Unit). The storage unit includes a memory such as a semiconductor memory, and may also include an HDD (Hard Disk Drive). The processor controls the operation of the image forming apparatus 100 by executing a control program. The storage unit stores the control program.

[0145] Operation unit 20 receives instructions from a user. When operation unit 20 receives an instruction from a user, it transmits a signal indicating the instruction from the user to control unit 15. As a result, image forming operation by image forming apparatus 100 is started.

[0146] The paper feed unit 30 has a paper feed cassette 31 and a paper feed roller group 32. The paper feed cassette 31 can accommodate a plurality of recording media P (e.g., paper). The paper feed roller group 32 feeds the recording media P accommodated in the paper feed cassette 31 to the conveying unit 40 one by one.

[0147] The conveying section 40 includes rollers and guide members. The conveying section 40 extends from the paper feeding section 30 to the discharge section 90. The conveying section 40 conveys the recording medium P from the paper feeding section 30 to the discharge section 90, passing through the image forming section 60 and the fixing device 80.

[0148] The toner supply unit 50 supplies toner to the image forming unit 60. The toner supply unit 50 includes a first mounting unit 51Y, a second mounting unit 51C, a third mounting unit 51M, and a fourth mounting unit 51K.

[0149] A first toner container 52Y is attached to the first attachment portion 51Y. Similarly, a second toner container 52C is attached to the second attachment portion 51C, a third toner container 52M is attached to the third attachment portion 51M, and a fourth toner container 52K is attached to the fourth attachment portion 51K.

[0150] The first toner container 52Y, the second toner container 52C, the third toner container 52M, and the fourth toner container 52K each contain a toner. In the second embodiment, the first toner container 52Y contains yellow toner. The second toner container 52C contains cyan toner. The third toner container 52M contains magenta toner. The fourth toner container 52K contains black toner.

[0151] The image forming section 60 includes an exposure device 61, a first image forming unit 62Y, a second image forming unit 62C, a third image forming unit 62M, and a fourth image forming unit 62K.

[0152] Each of the first to fourth image forming units 62Y to 62K includes a charging device 63, a developing device 64, an image carrier 65, a cleaning device 66, and a discharging device 67.

[0153] The first to fourth image forming units 62Y to 62K have the same configuration except for the type of toner supplied from the toner supply section 50. Therefore, in Figure 6, the reference numerals are omitted for the components of the second to fourth image forming units 62C to 62K.

[0154] The image carrier 65 is the photoreceptor of the first embodiment (more specifically, the single-layer photoreceptor 1 and the multi-layer photoreceptor 10). As described in the first embodiment, the photoreceptor of the first embodiment is excellent in initial sensitivity characteristics, repeated sensitivity characteristics, and wear resistance. Therefore, the image forming apparatus 100 of the second embodiment, which is equipped with the photoreceptor of the first embodiment, is excellent in initial sensitivity characteristics, repeated sensitivity characteristics, and wear resistance of the photoreceptor.

[0155] In the second embodiment, the image carrier 65 rotates in the direction indicated by the arrow R1 in Fig. 6 (clockwise in Fig. 6). The charging device 63, the developing device 64, the cleaning device 66, and the static eliminator 67 are arranged along the circumferential surface of the image carrier 65 in the order listed from the upstream side in the rotation direction of the image carrier 65.

[0156] The charging device 63 charges the surface (circumferential surface) of the image carrier 65. The charging device 63 uniformly charges the image carrier 65 to a predetermined polarity by discharging. The charging device 63 is, for example, a charging roller.

[0157] The exposure device 61 exposes the surface of the charged image carrier 65. More specifically, the exposure device 61 irradiates the surface of the charged image carrier 65 with laser light. As a result, an electrostatic latent image is formed on the surface of the image carrier 65.

[0158] Toner is supplied to the developing device 64 from the toner supply unit 50. The developing device 64 supplies the toner supplied from the toner supply unit 50 to the surface of the image carrier 65. As a result, the electrostatic latent image formed on the surface of the image carrier 65 is developed into a toner image.

[0159] In the second embodiment, the developing device 64 of the first image forming unit 62Y is connected to the first toner container 52Y. Therefore, yellow toner is supplied to the developing device 64 of the first image forming unit 62Y. Therefore, a yellow toner image is formed on the surface of the image carrier 65 of the first image forming unit 62Y.

[0160] Similarly, the developing device 64 of the second image forming unit 62C, the developing device 64 of the third image forming unit 62M, and the developing device 64 of the fourth image forming unit 62K are connected to the second toner container 52C, the third toner container 52M, and the fourth toner container 52K, respectively. Therefore, the developing device 64 of the second image forming unit 62C, the developing device 64 of the third image forming unit 62M, and the developing device 64 of the fourth image forming unit 62K are replenished with cyan toner, magenta toner, and black toner, respectively. Therefore, a cyan toner image, a magenta toner image, and a black toner image are formed on the surface of the image carrier 65 of the second image forming unit 62C, the surface of the image carrier 65 of the third image forming unit 62M, and the surface of the image carrier 65 of the fourth image forming unit 62K, respectively.

[0161] The cleaning device 66 has a cleaning member 661 and a rubbing roller 662. After transfer by a primary transfer roller 71 (described later), the cleaning member 661 is pressed against the surface of the image carrier 65 to collect toner adhering to the surface of the image carrier 65. The cleaning member 661 is, for example, a cleaning blade. The rubbing roller 662 rubs against the surface of the image carrier 65 to polish the surface of the image carrier 65.

[0162] The static eliminator 67 irradiates the surface of the image carrier 65 with static elimination light to eliminate static electricity from the surface of the image carrier 65 .

[0163] The transfer device 70 transfers the toner image from the image carrier 65 to the recording medium P, which is the transfer recipient. More specifically, the transfer device 70 transfers each toner image formed on the surface of each image carrier 65 of the first image forming unit 62Y to the fourth image forming unit 62K, superimposed on the recording medium P. In the second embodiment, the transfer device 70 transfers each toner image superimposed on the recording medium P by a secondary transfer method (intermediate transfer method). The transfer device 70 has four primary transfer rollers 71, an intermediate transfer belt 72, a drive roller 73, a driven roller 74, and a secondary transfer roller 75.

[0164] The intermediate transfer belt 72 is an endless belt that is stretched around four primary transfer rollers 71, a drive roller 73, and a driven roller 74. The intermediate transfer belt 72 is driven in accordance with the rotation of the drive roller 73. The intermediate transfer belt 72 rotates counterclockwise in FIG. 6. The driven roller 74 is driven to rotate in accordance with the drive of the intermediate transfer belt 72.

[0165] The first to fourth image forming units 62Y to 62K are arranged facing the lower surface of the intermediate transfer belt 72. In the second embodiment, the first to fourth image forming units 62Y to 62K are arranged in this order from the upstream side to the downstream side of the lower surface of the intermediate transfer belt 72 in the driving direction D.

[0166] Each primary transfer roller 71 is disposed opposite one of the image carriers 65 via the intermediate transfer belt 72 and is pressed against the corresponding image carrier 65. Therefore, the toner images formed on the surfaces of the corresponding image carriers 65 are sequentially transferred to the intermediate transfer belt 72 by each primary transfer roller 71. In the second embodiment, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are transferred and superimposed in this order onto the intermediate transfer belt 72. Hereinafter, a toner image formed by superimposing a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image may be referred to as a "laminated toner image."

[0167] The secondary transfer roller 75 is disposed opposite the drive roller 73 across the intermediate transfer belt 72. The secondary transfer roller 75 is pressed against the drive roller 73. This forms a transfer nip between the secondary transfer roller 75 and the drive roller 73. When the recording medium P passes through the transfer nip, the secondary transfer roller 75 transfers the layered toner image on the intermediate transfer belt 72 to the recording medium P. In the second embodiment, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are transferred to the recording medium P in this order from top to bottom. The recording medium P onto which the layered toner images have been transferred is transported by the transport unit 40 toward the fixing device 80.

[0168] The fixing device 80 includes a heating member 81 and a pressure member 82. The heating member 81 and the pressure member 82 are disposed opposite each other to form a fixing nip. The recording medium P conveyed from the image forming section 60 is heated at a predetermined fixing temperature and pressurized as it passes through the fixing nip. As a result, the laminated toner image is fixed to the recording medium P. The recording medium P is conveyed from the fixing device 80 to the discharge section 90 by the conveying section 40.

[0169] The discharge section 90 has a discharge roller pair 91 and a discharge tray 93. The discharge roller pair 91 transports the recording medium P to the discharge tray 93 through a discharge opening 92. The discharge opening 92 is formed in the upper part of the image forming apparatus 100.

[0170] Next, the configuration of the developing device 64 will be described in detail with reference to FIG. 7. FIG. 7 is a diagram showing an example of the configuration of the developing device 64. In detail, FIG. 7 shows the developing device 64 provided in the first image forming unit 62Y. Note that in FIG. 7, the image carrier 65 is shown by a two-dot chain line for ease of understanding. In the second embodiment, the developing device 64 employs a two-component development method using a two-component developer and a touch-down development method.

[0171] 6, the developing container 640 of the developing device 64 is connected to the first toner container 52Y. Therefore, yellow toner is replenished to the developing container 640 of the developing device 64 through the toner replenishing port 640h.

[0172] 7, the developing device 64 has a developing roller 641, a magnetic roller 642, a first stirring screw 643, a second stirring screw 644, and a blade 645 inside a developing container 640. More specifically, the developing roller 641 is disposed opposite the magnetic roller 642. The magnetic roller 642 is disposed opposite the second stirring screw 644. The blade 645 is disposed opposite the magnetic roller 642.

[0173] The developing container 640 is divided into a first stirring chamber 640a and a second stirring chamber 640b by a partition wall 640c. The partition wall 640c extends in the axial direction of the developing roller 641. The first stirring chamber 640a and the second stirring chamber 640b communicate with each other on the outer sides of both longitudinal ends of the partition wall 640c.

[0174] A first stirring screw 643 is disposed in the first stirring chamber 640a. A carrier, which is a magnetic material, is accommodated in the first stirring chamber 640a. Toner, which is a non-magnetic material, is replenished to the first stirring chamber 640a through a toner replenishing port 640h. In the example shown in FIG. 7, yellow toner is replenished to the first stirring chamber 640a.

[0175] The second stirring chamber 640b is provided with a second stirring screw 644. The second stirring chamber 640b accommodates a carrier that is a magnetic body.

[0176] The yellow toner is mixed with the carrier by the first mixing screw 643 and the second mixing screw 644. As a result, a two-component developer containing the carrier and the yellow toner is formed. The two-component developer is then contained in the developing container 640 (more specifically, the first mixing chamber 640a and the second mixing chamber 640b).

[0177] The first stirring screw 643 and the second stirring screw 644 circulate and stir the two-component developer between the first stirring chamber 640a and the second stirring chamber 640b. As a result, the toner is charged to a predetermined polarity due to friction with the carrier.

[0178] When the image carrier 65 is a single-layer photoreceptor 1, the surface of the image carrier 65 and the toner are charged, for example, to a positive polarity. When the image carrier 65 is a multi-layer photoreceptor 10, the surface of the image carrier 65 and the toner are charged, for example, to a negative polarity.

[0179] The magnetic roller 642 is composed of a non-magnetic rotating sleeve 642a and a magnet body 642b. The magnet body 642b is fixedly disposed inside the rotating sleeve 642a. The magnet body 642b includes multiple magnetic poles. The two-component developer is attracted to the magnetic roller 642 by the magnetic force of the magnet body 642b. As a result, a magnetic brush is formed on the surface of the magnetic roller 642.

[0180] Blade 645 is disposed upstream of the position where magnetic roller 642 and developing roller 641 face each other in the rotation direction of magnetic roller 642. In the second embodiment, magnetic roller 642 rotates in the direction indicated by arrow R3 in FIG. 7 (counterclockwise in FIG. 7). Magnetic roller 642 transports the magnetic brush to a position facing blade 645 by rotating. Blade 645 is disposed so that a gap is formed between blade 645 and magnetic roller 642. Blade 645 is made of a magnetic material. Therefore, the thickness of the magnetic brush is regulated by the magnetic force of blade 645.

[0181] After the thickness of the magnetic brush on magnetic roller 642 is regulated, a predetermined voltage is applied to magnetic roller 642 and developing roller 641. When a predetermined voltage is applied and a predetermined potential difference is created between magnetic roller 642 and developing roller 641, yellow toner contained in the two-component developer migrates to developing roller 641. As a result, a thin toner layer made of yellow toner is formed on the surface of developing roller 641.

[0182] Developing roller 641 rotates in the direction indicated by arrow R2 in Fig. 7 (counterclockwise in Fig. 7). As a result, the thin layer of toner formed on the surface of developing roller 641 is transported to a position facing image carrier 65 and adheres to image carrier 65. In this way, developing device 64 supplies toner, which has been charged by friction with the carrier, to the surface of image carrier 65.

[0183] The developing device 64 of the first image forming unit 62Y has been described above with reference to Fig. 7. The configuration of the developing device 64 of each of the first image forming unit 62Y to the fourth image forming unit 62K is the same except that the type of toner replenished from the toner replenishing section 50 is different. Therefore, a description of the configuration of the developing device 64 of the second image forming unit 62C to the fourth image forming unit 62K will be omitted.

[0184] The image forming apparatus 100, which is an example of the image forming apparatus of the second embodiment, has been described above with reference to FIGS. 6 and 7. However, the image forming apparatus of the second embodiment is not limited to the image forming apparatus 100. For example, the image forming apparatus may be a monochrome image forming apparatus. In this case, the image forming apparatus may include only one image forming unit. The image forming apparatus may employ a rotary system. The charging device may be a charging device other than a charging roller (e.g., a scorotron charger, a charging brush, or a corotron charger). The image forming apparatus may employ a one-component development system using a one-component developer. The image forming apparatus may employ a development system other than a touchdown development system (e.g., a development system in which a magnetic roller serves as a developing roller without a developing roller). The image forming apparatus may employ a direct transfer system. When the image forming apparatus employs a direct transfer system, a toner image is directly transferred from an image carrier to a recording medium while the image carrier is in contact with the recording medium. The image forming apparatus may not include a cleaning device. The image forming apparatus may not include a static eliminator. The image forming apparatus according to the second embodiment has been described above.

[0185] [Third embodiment: process cartridge] Next, with continued reference to FIG. 6, a first process cartridge 101, a second process cartridge 102, a third process cartridge 103, and a fourth process cartridge 104, which are examples of process cartridges according to a third embodiment of the present invention, will be described. The first process cartridge 101 to the fourth process cartridge 104 of the third embodiment correspond to the first image forming unit 62Y to the fourth image forming unit 62K, respectively. The first process cartridge 101 to the fourth process cartridge 104 each include an image carrier 65. The image carrier 65 is the photosensitive member of the first embodiment (more specifically, the single-layer photosensitive member 1 and the multi-layer photosensitive member 10).

[0186] As described in the first embodiment, the photosensitive member of the first embodiment has excellent initial sensitivity characteristics, repeated sensitivity characteristics, and abrasion resistance. Therefore, the process cartridge of the third embodiment, which includes the photosensitive member of the first embodiment, has excellent initial sensitivity characteristics, repeated sensitivity characteristics, and abrasion resistance.

[0187] In addition to the image carrier 65, the process cartridge of the third embodiment may further include at least one (for example, one to seven) selected from the group consisting of a charging device 63, an exposure device 61, a developing device 64, a transfer device 70 (particularly, a primary transfer roller 71), a cleaning member 661, a rubbing roller 662, and a charge removal device 67.

[0188] The first process cartridge 101, second process cartridge 102, third process cartridge 103, and fourth process cartridge 104 shown in FIG. 6 each include an image carrier 65, a charging device 63, a developing device 64, a cleaning device 66 having a cleaning member 661 and a rubbing roller 662, and a static eliminator 67, similar to the first image forming unit 62Y, second image forming unit 62C, third image forming unit 62M, and fourth image forming unit 62K. However, the process cartridges of the third embodiment are not limited to the first process cartridge 101 to the fourth process cartridge 104. As described above, the process cartridge of the third embodiment may further include at least one of the exposure device 61 and the transfer device 70, or may include only one of the cleaning member 661 and the rubbing roller 662 (for example, only the cleaning member 661). In any case, the process cartridge of the third embodiment may include the photosensitive member of the first embodiment as the image carrier 65.

[0189] The process cartridge of the third embodiment is designed to be detachable from the image forming apparatus 100. Therefore, the process cartridge is easy to handle, and when the sensitivity characteristics of the image carrier 65 deteriorate, the process cartridge can be easily and quickly replaced, including the image carrier 65. The process cartridge of the third embodiment has been described above with reference to FIG. 6.

[0190] [Substituent] The substituents used in this specification will be described below. Examples of halogen atoms (halogen groups) include fluorine atoms (fluoro groups), chlorine atoms (chloro groups), bromine atoms (bromo groups), and iodine atoms (iodo groups).

[0191] Unless otherwise specified, alkyl groups having 1 to 8 carbon atoms, alkyl groups having 1 to 6 carbon atoms, alkyl groups having 1 to 5 carbon atoms, alkyl groups having 1 to 4 carbon atoms, and alkyl groups having 1 to 3 carbon atoms are each straight-chain or branched-chain and unsubstituted. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 2-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, n-hexyl, 1-methylpentyl, 2 ... Examples of alkyl groups having from 1 to 6 carbon atoms, from 1 to 5 carbon atoms, from 1 to 4 carbon atoms, and from 1 to 3 carbon atoms are the same as those groups listed above as examples of alkyl groups having from 1 to 8 carbon atoms, but having the corresponding number of carbon atoms.

[0192] Unless otherwise specified, the alkoxy group having 1 to 6 carbon atoms is linear or branched and unsubstituted. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, an n-pentoxy group, a 1-methylbutoxy group, a 2-methylbutoxy group, a 3-methylbutoxy group, a 1-ethylpropoxy group, a 2-ethylpropoxy group, a 1,1-dimethylpropoxy group, a 1,2-dimethylpropoxy group, a 2,2-dimethylpropoxy group, an n-hexyloxy group, a 1-methylbutoxy group, a 2-methylbutoxy group, a 3-methylbutoxy group, a 1-ethylpropoxy group, a 2-ethylpropoxy group, a 1,1-dimethylpropoxy group, a 1,2-dimethylpropoxy group, a 2,2-dimethylpropoxy group, an n-hexyloxy group, a 1-methylbutoxy group, a 2-methylbutoxy group, a 2,2-dimethylpropoxy group, a 2-methylbut ... Examples of alkyl ethers include 1,1-dimethylbutoxy, 2-methylpentyloxy, 3-methylpentyloxy, 4-methylpentyloxy, 1,1-dimethylbutoxy, 1,2-dimethylbutoxy, 1,3-dimethylbutoxy, 2,2-dimethylbutoxy, 2,3-dimethylbutoxy, 3,3-dimethylbutoxy, 1,1,2-trimethylpropoxy, 1,2,2-trimethylpropoxy, 1-ethylbutoxy, 2-ethylbutoxy, and 3-ethylbutoxy groups.

[0193] Unless otherwise specified, each of the aryl groups having 6 to 14 carbon atoms and the aryl groups having 6 to 10 carbon atoms is unsubstituted. Examples of aryl groups having 6 to 14 carbon atoms include a phenyl group, a naphthyl group, an indacenyl group, a biphenylenyl group, an acenaphthylenyl group, an anthryl group, and a phenanthryl group. Examples of aryl groups having 6 to 10 carbon atoms are groups having the corresponding number of carbon atoms among the groups mentioned as examples of aryl groups having 6 to 14 carbon atoms.

[0194] Unless otherwise specified, an alkenyl group having 2 to 6 carbon atoms is linear or branched and unsubstituted. An alkenyl group having 2 to 6 carbon atoms has one to three double bonds. Examples of alkenyl groups having 2 to 6 carbon atoms include ethenyl, propenyl, butenyl, butadienyl, pentenyl, hexenyl, hexadienyl, and hexatriyl groups. The substituents used in this specification have been described above. [Example]

[0195] The present invention will be explained in more detail below using examples, but the present invention is not limited to the scope of the examples.

[0196] [Conductive material] The following conductive materials were prepared to be contained in the protective layer. Conductive materials (A-1) to (A-11): the conductive materials (A-1) to (A-11) described in the first embodiment Conductive material (A-12): Tin oxide (Mitsubishi Materials Electronic Chemicals Co., Ltd. "S-2000", undoped tin oxide, BET specific surface area 52.5±7.5m 2 / g) Conductive material (A-13): Antimony-doped tin oxide (Mitsubishi Materials Electronic Chemicals Co., Ltd. "T-1", BET specific surface area 77.5±7.5m 2 / g, number average primary particle diameter 200nm) Conductive material (A-14): Zinc oxide (CIK NanoTek Co., Ltd. "NanoTek ZnO", number average primary particle diameter 65.9 nm)

[0197] [Multifunctional Monomers] The polyfunctional monomers used were as follows: Multifunctional monomer (B-1): "A-DPH" manufactured by Shin-Nakamura Chemical Co., Ltd. (a mixture of compounds represented by formulas (EA-3) and (EA-4) described in the first embodiment, the compound represented by formula (EA-3) having 5 polymerizable functional groups, the compound represented by formula (EA-4) having 6 polymerizable functional groups, and a hydroxyl value of 10 mgKOH / g)

[0198] [Monofunctional Monomer] The monofunctional monomers used were as follows: Monofunctional monomer (C-3): "Viscoat 8F" manufactured by Osaka Organic Chemical Industry Ltd. (a compound represented by formula (C-3) described in the first embodiment, having one polymerizable functional group)

[0199] [Manufacturing of multilayer photoreceptors] Multilayer photoreceptors (P-A1) to (P-A11) and (P-B1) to (P-B4) were manufactured by the following method. The configurations of these multilayer photoreceptors are shown in Table 1.

[0200] <Manufacturing of multilayer photoreceptor (P-A1)> (Formation of intermediate layer) Two parts by weight of titanium oxide, one part by weight of polyamide resin, 10 parts by weight of methanol, one part by weight of butanol, and one part by weight of toluene were mixed for five hours using a bead mill to obtain a mixed solution a. The titanium oxide used was a prototype "SMT-A" manufactured by Teika Corporation (number-average primary particle diameter: 10 nm, titanium oxide was primarily surface-treated with alumina and silica, and the primary surface-treated titanium oxide was then secondary-surface-treated with methylhydrogenpolysiloxane). The polyamide resin used was "Amilan (registered trademark) CM8000" manufactured by Toray Industries, Inc. (a tetrapolymer polyamide resin of polyamide 6, polyamide 12, polyamide 66, and polyamide 610). The resulting mixed solution a was filtered using a filter with a 5 μm mesh size to obtain a coating solution for an intermediate layer. The coating solution for an intermediate layer was then applied to the surface of a conductive substrate by dip coating. An aluminum drum-shaped support was used as the conductive substrate. Next, the applied intermediate layer coating liquid was dried at 130° C. for 30 minutes to form an intermediate layer (film thickness: 0.5 μm) on the conductive substrate.

[0201] (Formation of Charge Generation Layer) 1.5 parts by weight of Y-type titanyl phthalocyanine as a charge generating agent, 1.0 part by weight of polyvinyl acetal resin ("S-LEC BX-5" manufactured by Sekisui Chemical Co., Ltd.) as a base resin, 40.0 parts by weight of propylene glycol monomethyl ether, and 40.0 parts by weight of tetrahydrofuran were mixed for 12 hours using a bead mill to obtain a mixed solution d. The mixed solution d was filtered using a filter with a mesh size of 3 μm to obtain a charge generating layer coating solution. Next, the charge generating layer coating solution was applied to the intermediate layer on the conductive substrate by dip coating. The applied charge generating layer coating solution was dried at 50°C for 5 minutes to form a charge generating layer (film thickness: 0.3 μm) on the intermediate layer.

[0202] (Formation of charge transport layer) 60.00 parts by weight of hole transport agent (HT-2), 30.00 parts by weight of hole transport agent (HT-3), 100.00 parts by weight of bisphenol Z-type polycarbonate resin, 0.05 parts by weight of leveling agent, 340.00 parts by weight of tetrahydrofuran, and 60.00 parts by weight of toluene were mixed using a roll mill for 24 hours to obtain a coating liquid for a charge transport layer. The bisphenol Z-type polycarbonate resin used was "Iupizeta PCZ-200" manufactured by Mitsubishi Gas Chemical Company, Inc. The leveling agent used was dimethyl silicone oil ("KF96-50CS" manufactured by Shin-Etsu Chemical Co., Ltd.). The coating liquid for the charge transport layer was then applied onto the charge generation layer by dip coating. The applied coating liquid for the charge transport layer was dried at 120°C for 40 minutes to form a charge transport layer (film thickness: 25 μm) on the charge generation layer.

[0203] (Formation of protective layer) 4.2 parts by mass of conductive material (A-1), 1.1 parts by mass of alumina, 56.0 parts by mass of polyfunctional monomer (B-1), 33.0 parts by mass of monofunctional monomer (C-3), 1.0 part by mass of leveling agent, 10.0 parts by mass of polymerization initiator, and 110.0 parts by mass of methanol were mixed for 12 hours using a bead mill to obtain mixed solution c. As the alumina, "Nanotek Al2O3" (BET specific surface area 55 m) manufactured by CIK Nanotech Co., Ltd. was used. 2 / g, number average primary particle diameter 31 nm). A UV-curable fluorine silicone modified acrylic polymer with vinyl groups ("8FS-001" manufactured by Taisei Fine Chemical Co., Ltd., double bond equivalent (vinyl group equivalent): 420 g / mol) was used as the leveling agent. 2,4,6-trimethylbenzoyl-diphenylphosphine oxide ("OMNIRAD TPO" manufactured by IGM RESINS) was used as the polymerization initiator. The resulting mixed solution c was filtered using a filter with 5 μm openings to obtain a coating solution for the protective layer.

[0204] Next, the protective layer coating liquid was applied onto the charge transport layer by dip coating. The applied protective layer coating liquid was irradiated with UV light having a wavelength of 365 nm and an intensity of 2400 mW / cm. 2The protective layer was then irradiated with ultraviolet light for 36 seconds. The ultraviolet light irradiation caused the polyfunctional monomer, monofunctional monomer, and leveling agent in the protective layer coating liquid to polymerize (photocuring reaction) to form a photocurable resin. In this way, a protective layer (film thickness: 1.0 μm) was formed on the charge transport layer, and a multilayer photoreceptor (P-A1) was obtained. The protective layer contained the photocurable resin cured by the photocuring reaction, the conductive material (A-1), alumina, and a polymerization initiator.

[0205] <Manufacture of multilayer photoreceptors (P-A2) to (P-A11) and (P-B1) to (P-B3)> Except for using the conductive materials shown in Table 1, the multilayer photoreceptors (P-A2) to (P-A11) and (P-B1) to (P-B3) were manufactured in the same manner as the multilayer photoreceptor (P-A1).

[0206] <Manufacturing of multilayer photoreceptor (P-B4)> A multi-layer photoreceptor (P-B4) was produced in the same manner as in the production of the multi-layer photoreceptor (P-A1), except that the protective layer was not formed.

[0207] [Evaluation of multilayer photoreceptors] The initial sensitivity characteristics, repeated sensitivity characteristics, and abrasion resistance of the multilayer photoreceptors (P-A1) to (P-A11) and (P-B1) to (P-B4) were evaluated by the following methods.

[0208] <Initial sensitivity characteristics> The sensitivity characteristics of the photoreceptor were evaluated using a drum sensitivity tester (manufactured by Gentec) under an environment of 23°C temperature and 50% relative humidity. Using the drum sensitivity tester, the surface of the photoreceptor was charged to -550 V. Then, monochromatic light (wavelength: 780 nm, exposure dose: 0.87 μJ / cm) was applied. 2 ) was extracted from the light of a halogen lamp using a bandpass filter and irradiated onto the surface of the photoreceptor. The surface potential of the photoreceptor was measured 50 milliseconds after the end of irradiation with monochromatic light. The measured surface potential was taken as the post-exposure potential VL (unit: -V) of the photoreceptor. The post-exposure potential VL is shown in Table 1. The criteria for judging the initial sensitivity characteristics of the photoreceptor are as follows:

[0209] (Initial sensitivity characteristic criteria) Good: The absolute value of VL is 150V or less. Bad: The absolute value of VL is greater than 150V.

[0210] <Repetitive sensitivity characteristics> To evaluate the cyclic sensitivity of the laminated photoreceptor, a color multifunction printer (Kyocera Document Solutions Co., Ltd., "Taskalfa 356ci") modified to have a negative charging polarity was used. This evaluation machine was equipped with a charging roller made of epichlorohydrin resin with dispersed conductive carbon. The cyclic sensitivity evaluation was performed under normal temperature and humidity conditions of 23°C and 50% RH. Image I (solid image) was printed on one sheet of paper using the evaluation machine, and the post-exposure potential VL1 (unit: -V) during printing was measured. Next, Image II (a pattern image with a 3% printing rate) was printed on 5,000 sheets of paper using the evaluation machine. Next, Image I (solid image) was printed on one sheet of paper using the evaluation machine, and the post-exposure potential VL2 (unit: -V) during printing was measured. The change in post-exposure potential ΔVL (unit: V) was calculated using the formula "ΔVL = |VL2 - VL1|". Here, |VL2-VL1| indicates the absolute value of VL2-VL1. ΔVL is shown in Table 1. The criteria for the repeated sensitivity characteristics of the photosensitive member are shown below.

[0211] (Standard for repeat sensitivity characteristics) Good: ΔVL is 30V or less. Bad: ΔVL is greater than 30V.

[0212] <Wear resistance> A color printer (Oki Data Corporation, "C711dn") was used as an evaluation machine for the wear resistance of the laminated photoreceptor. The toner cartridge of the evaluation machine was filled with cyan toner. First, the film thickness T1 of the photosensitive layer of the photoreceptor was measured. Next, the photoreceptor was mounted on the evaluation machine. Next, Image III (a pattern image with a printing rate of 1%) was printed on 10,000 sheets of paper using the evaluation machine under a normal temperature and humidity environment of a temperature of 23°C and a relative humidity of 50%RH. Next, Image III was printed on 10,000 sheets of paper using the evaluation machine under a high temperature and high humidity environment of a temperature of 32°C and a relative humidity of 85%RH. Next, Image III was printed on 10,000 sheets of paper using the evaluation machine under a low temperature and low humidity environment of a temperature of 10°C and a relative humidity of 15%RH. After printing under the low temperature and low humidity environment, the evaluation machine was left to stand for 2 hours. Next, a solid image (an image with 100% image density) was printed on a sheet of paper using an evaluation machine in a low-temperature, low-humidity environment. The thickness T2 of the photosensitive layer of the photoreceptor was then measured. The amount of wear (T1-T2, unit: μm), which is the change in thickness of the photosensitive layer before and after printing, was then determined. The measured amount of wear is shown in Table 1. The criteria for judging the wear resistance of the photoreceptor are as follows:

[0213] (Abrasion resistance standard) Good: The amount of wear is 0.5 μm or less. Poor: The amount of wear exceeds 0.5 μm.

[0214] [Table 1]

[0215] In Table 1 and Table 2 described later, "Experiment" indicates an example, and "Comparison" indicates a comparative example.

[0216] As shown in Table 1, each of the protective layers of the multilayer photoreceptors (P-B1) to (P-B3) contained one of the conductive materials (A-12) to (A-14), but none of the conductive materials (A-12) to (A-14) was the conductive material (A). The repeated sensitivity characteristics of the multilayer photoreceptors (P-B1) to (P-B3) were evaluated as poor. The initial sensitivity characteristics of the multilayer photoreceptors (P-B1) and (P-B3) were evaluated as poor.

[0217] The multi-layer photoreceptor (P-B4) did not have a protective layer, as shown in Table 1. The abrasion resistance of the multi-layer photoreceptor (P-B4) was evaluated as poor.

[0218] As shown in Table 1, each of the protective layers of the multilayer photoreceptors (P-A1) to (P-A11) contained a conductive material (A). The initial sensitivity characteristics, repeated sensitivity characteristics, and abrasion resistance of the multilayer photoreceptors (P-A1) to (P-A11) were all evaluated to be good.

[0219] [Manufacturing of single-layer photoreceptors] A single-layer photoreceptor (P-C1) was produced by the following method: The structure of the protective layer of this single-layer photoreceptor is shown in Table 2 below.

[0220] <Manufacturing of single-layer photoreceptor (P-C1)> (Formation of a single-layer photosensitive layer) 2.85 parts by weight of Y-type titanyl phthalocyanine, 60.00 parts by weight of hole transport agent (HT-2), 30.00 parts by weight of hole transport agent (HT-3), 34.00 parts by weight of electron transport agent (ET-1), 34.00 parts by weight of electron transport agent (ET-6), 70.00 parts by weight of bisphenol Z-type polycarbonate resin, 0.02 parts by weight of leveling agent, and 500.00 parts by weight of tetrahydrofuran were mixed for 20 minutes using a rod-shaped ultrasonic oscillator to obtain mixed solution b. The bisphenol Z-type polycarbonate resin used was "Iupizeta PCZ-200" manufactured by Mitsubishi Gas Chemical Company, Inc. The leveling agent used was dimethyl silicone oil ("KF96-50CS" manufactured by Shin-Etsu Chemical Co., Ltd.). The resulting mixed solution b was filtered using a 5 μm filter to obtain a coating solution for a single-layer photosensitive layer. Next, the coating solution for the single-layer photosensitive layer was applied to a conductive substrate by dip coating. An aluminum drum-shaped support was used as the conductive substrate. The applied coating solution for the single-layer photosensitive layer was dried at 110°C for 60 minutes to form a single-layer photosensitive layer (film thickness: 25 μm) on the conductive substrate.

[0221] (Formation of protective layer) The protective layer for the single-layer photoreceptor (P-C1) was formed in the same manner as in the formation of the protective layer for the multilayer photoreceptor (P-A1), except that the protective layer coating liquid was applied onto the single-layer photosensitive layer instead of onto the charge transport layer.

[0222] [Evaluation of single-layer photoreceptors] The initial sensitivity characteristics, repeated sensitivity characteristics, and abrasion resistance of the single-layer photoreceptor (P-C1) were evaluated by the following methods.

[0223] <Initial sensitivity characteristics> The sensitivity characteristics of the single-layer photoreceptor were evaluated in the same manner as for evaluating the sensitivity characteristics of the multilayer photoreceptor, except that the surface of the photoreceptor was charged to +550 V instead of -550 V. The measured VL (unit: +V) is shown in Table 2.

[0224] <Repetitive sensitivity characteristics> The repeated sensitivity characteristics of the single-layer photoreceptor were evaluated in the same manner as in the evaluation of the abrasion resistance of the multilayer photoreceptor, except that the charging polarity of the evaluation machine was changed from negative to positive. The measured ΔVL (unit: V) is shown in Table 2.

[0225] <Wear resistance> The abrasion resistance of the single-layer photoreceptor was evaluated in the same manner as in the evaluation of the abrasion resistance of the multilayer photoreceptor, except that the evaluation machine was changed from a color printer ("C711dn" manufactured by OKI Data Corporation) to a modified color multifunction printer ("Taskalfa 356ci" manufactured by Kyocera Document Solutions Co., Ltd.) The measured abrasion amounts are shown in Table 2.

[0226] [Table 2]

[0227] As shown in Table 2, each of the protective layers of the single-layer photoreceptor (P-C1) contained a conductive material (A). The single-layer photoreceptor (P-C1) was evaluated as being good in terms of initial sensitivity, repeated sensitivity, and abrasion resistance.

[0228] From the above, it has been shown that the photoreceptors of the present invention, including the multilayer photoreceptors (P-A1) to (P-A11) and the single-layer photoreceptor (P-C1), are excellent in initial sensitivity characteristics, repeated sensitivity characteristics, and abrasion resistance. Furthermore, since such photoreceptors are provided, it is considered that the process cartridge and image forming apparatus of the present invention are excellent in initial sensitivity characteristics, repeated sensitivity characteristics, and abrasion resistance of the photoreceptor. [Industrial Applicability]

[0229] The photosensitive member and process cartridge according to the present invention can be used in an image forming apparatus, and the image forming apparatus according to the present invention can be used to form an image on a recording medium.

Claims

1. An electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer, and a protective layer, the photosensitive layer contains a charge generating agent, the protective layer is an outermost layer of the electrophotographic photoreceptor, The protective layer of the electrophotographic photoreceptor contains a compound represented by formula (A). 【Chemistry 1】 (In the formula (A), R 21 is a hydrogen atom, Li + , or K + represents R 22 and R 23 each independently represents an alkyl group having 1 to 4 carbon atoms substituted with at least one halogen atom.

2. In the formula (A), R 21 Li + , or K + The electrophotographic photoreceptor according to claim 1 , wherein

3. In the formula (A), R 22 and R 23 2. The electrophotographic photoreceptor according to claim 1, wherein one or both of represent a methyl group substituted with at least one halogen atom.

4. the protective layer further contains a photocurable resin, 2. The electrophotographic photoreceptor according to claim 1, wherein the photocurable resin has a repeating unit derived from a compound having one polymerizable functional group and a repeating unit derived from a compound having two or more polymerizable functional groups.

5. 5. The electrophotographic photoreceptor according to claim 4, wherein the repeating unit derived from the compound having one polymerizable functional group is a repeating unit derived from a compound represented by formula (EB-1). 【Chemistry 2】 (In the formula (EB-1), R 1 represents a group represented by formula (b1), and R 2 represents a hydrogen atom or a methyl group. 【Transformation 3】 (In the formula (b1), m represents 0 or 1, n represents an integer of 1 or more and 3 or less, R 3 represents a hydrogen atom or a fluorine atom, and * represents a bond.

6. The electrophotographic photoreceptor according to claim 4, wherein the repeating unit derived from the compound having two or more polymerizable functional groups is a repeating unit derived from at least one compound selected from the group consisting of compounds represented by formulas (EA-3) and (EA-4): 【Chemistry 4】

7. 2. The electrophotographic photoreceptor according to claim 1, wherein the protective layer has a thickness of 1 [mu]m or more and 4 [mu]m or less.

8. 2. The electrophotographic photoreceptor according to claim 1, wherein the charge generating agent contained in the photosensitive layer comprises titanyl phthalocyanine.

9. at least one selected from the group consisting of a charging device, an exposure device, a developing device, a transfer device, a cleaning member, a rubbing roller, and a static eliminator; A process cartridge comprising the electrophotographic photosensitive member according to claim 1.

10. an image carrier; a charging device that charges the surface of the image carrier; an exposure device that exposes the charged surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier; a developing device that supplies toner to the surface of the image carrier to develop the electrostatic latent image into a toner image; a transfer device that transfers the toner image from the image carrier to a transfer target, An image forming apparatus, wherein the image bearing member is the electrophotographic photoreceptor according to claim 1 .

11. a cleaning member that collects the toner adhering to the surface of the image carrier; a rubbing roller that rubs the surface of the image carrier; and a static eliminator for eliminating static electricity from the surface of the image carrier; The image forming apparatus according to claim 10 , further comprising at least one selected from the group consisting of:

12. The image forming apparatus according to claim 10 , wherein the charging device is a charging roller.

13. 11. The image forming apparatus according to claim 10, wherein the developing device supplies the toner, which has been charged by friction with a carrier, to the surface of the image carrier.

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