Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

The present invention provides an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus that can suppress the occurrence of image flow. [Solution] An electrophotographic photoreceptor according to one embodiment of the present invention comprises a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer. The polar component γp of the surface free energy of the protective layer is 23 mJ / m 2 More than 31mJ / m 2 The following is true: The nonpolar component γd of the surface free energy of the protective layer is 12 mJ / m 2 More than 19mJ / m 2 The following applies:

Description

Technical Field

[0001] The present invention relates to an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus.

Background Art

[0002] When repeatedly forming an image using an image forming apparatus provided with an electrophotographic photoreceptor, the surface of the electrophotographic photoreceptor may gradually wear. For this reason, a hard protective layer is provided on the surface of the photoreceptor. In the electrophotographic photoreceptor described in Patent Document 1, the durability is improved by adjusting the hardness of the outermost layer (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, by providing a hard protective layer, the removability of foreign substances (such as discharge products and aqueous substances) adhering to the surface of the photoreceptor decreases, and image flow (image blurring) is likely to occur. For this reason, there is room for improvement in suppressing image flow in the electrophotographic photoreceptor of Patent Document 1.

[0005] In view of the above circumstances, an object of the present invention is to provide an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus capable of suppressing the occurrence of image flow.

Means for Solving the Problems

[0006] To achieve the above object, an electrophotographic photoreceptor according to one embodiment of the present invention includes a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer. The polar component γp of the surface free energy of the above protective layer is 23 mJ / m 2 More than 31mJ / m 2 The following: The nonpolar component γd of the surface free energy of the above protective layer is 12 mJ / m 2 More than 19mJ / m 2 The following applies:

[0007] A process cartridge according to one embodiment of the present invention comprises the electrophotographic photoreceptor described above.

[0008] An image forming apparatus according to one embodiment of the present invention comprises: an image carrier made of the electrophotographic photoreceptor; a charging device for charging the surface of the image carrier; an exposure device for exposing the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier; a developing device for supplying toner to the surface of the image carrier to develop the electrostatic latent image as a toner image; and a transfer device for transferring the toner image from the image carrier to a transfer target. [Effects of the Invention]

[0009] This invention provides an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus that can suppress the occurrence of image flow. [Brief explanation of the drawing]

[0010] [Figure 1] This is a partial cross-sectional view of a single-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 2] This is a partial cross-sectional view of a stacked electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 3] This figure shows an example of an image forming apparatus according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0011] <First Embodiment: Electrophotographic Photoreceptor> [Overall structure] A 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 provided (directly or indirectly) on the conductive substrate, and a protective layer provided on the photosensitive layer. The protective layer is the outermost surface layer of the photoreceptor. The polar component γp of the surface free energy of the protective layer is 23 mJ / m 2 More than 31mJ / m 2 The following is true: The nonpolar component γd of the surface free energy of the protective layer is 12 mJ / m 2 More than 19mJ / m 2 The following applies:

[0012] In the first embodiment of the photoreceptor, by controlling the polar component γp and the non-polar component γd of the surface free energy of the protective layer, which is the outermost surface, foreign matter on the surface of the photoreceptor can be easily removed, and the occurrence of image blur can be suppressed.

[0013] In this invention, the polar component γp and the nonpolar component γd of the surface free energy are calculated by measuring the contact angles with water, polyethylene glycol with a number-average molecular weight of 200 (hereinafter also referred to as "PEG200"), and tricresyl phosphate on the surface of the protective layer, and using the OWRK method (Owens-Wendt-Rable-Kaelble method) to determine these contact angles. More specifically, they are calculated using the measurement method described in the examples below. Water is a liquid with a very high polar component, PEG200 has a medium to high polar component different from water, and tricresyl phosphate has a relatively large nonpolar component. By using these three types of liquids, the surface free energy of the photoreceptor surface can be evaluated more accurately over a wide range from nonpolar to highly polar.

[0014] Furthermore, surface free energy is composed of the sum of intermolecular force components. Intermolecular forces are classified into dispersion forces, orientation forces, induced forces, and hydrogen bonding forces, and these constitute the surface free energy as nonpolar components (dispersion), polar components (polar), induced components (induction), and hydrogen bonding components (hydrogen), respectively. Since the induced component is very weak, its influence can be ignored. Also, since the hydrogen bonding component, like the polar component (orientation force), is due to polar interactions between molecules, the hydrogen bonding component can be considered as a polar component. For this reason, the influence of the overall polar interactions between molecules can be evaluated from only the nonpolar component γd and the polar component γp.

[0015] The photoreceptor of the first embodiment, by having the above configuration, can suppress the occurrence of image blurring. The reason for this is presumed to be as follows.

[0016] When the polar component γp is greater than the non-polar component γd within the above range, the fatty acid metal salt, which is an external additive for toner, adheres more easily to the surface of the photoreceptor, and the aliphatic moieties are oriented to the surface. As a result, the water resistance of the photoreceptor surface can be improved. This suppresses the adhesion of aqueous substances (especially moisture in high-temperature and high-humidity environments) and prevents image blurring caused by a decrease in the surface resistance of the photoreceptor. Furthermore, because the non-polar component γd is smaller than the polar component γp within the above range, the adhesion of the toner's wax component to the surface of the photoreceptor is prevented, and filming is suppressed. As a result, the surface potential of the photoreceptor is maintained, and image flow can be suppressed. Thus, with the surface of the photoreceptor of the present invention, in which the surface free energy is controlled, the refreshability (cleanability) of the photoreceptor is improved, and image blurring is suppressed more effectively.

[0017] The reason why the photoreceptor of the first embodiment can suppress the occurrence of image blurring has been explained above. The photoreceptor will be described further below.

[0018] The photoreceptor is, for example, a single-layer electrophotographic photoreceptor (hereinafter sometimes referred to as a single-layer photoreceptor) or a multilayer electrophotographic photoreceptor (hereinafter sometimes referred to as a multilayer photoreceptor).

[0019] The structure of a single-layer photoreceptor 1, an example of a photoreceptor, will be described below with reference to Figure 1. Figures 1(a) and 1(b) show partial cross-sectional views of the single-layer photoreceptor 1. As shown in Figure 1(a), the single-layer photoreceptor 1 comprises, 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 the "single-layer photosensitive layer 3a." In the example shown in Figure 1(a), the single-layer photosensitive layer 3a is provided on the conductive substrate 2, and the protective layer 5 is provided on the single-layer photosensitive layer 3a. The single-layer photosensitive layer 3a is directly provided on the conductive substrate 2. The protective layer 5 is the outermost layer of the single-layer photoreceptor 1.

[0020] As shown in Figure 1(b), the single-layer photoreceptor 1 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2, the single-layer photoreceptor layer 3a, and the protective layer 5. In the example shown in Figure 1(b), the intermediate layer 4 is provided on the conductive substrate 2, the single-layer photoreceptor layer 3a is provided on the intermediate layer 4, and the protective layer 5 is provided on the single-layer photoreceptor layer 3a. The single-layer photoreceptor layer 3a is provided on the conductive substrate 2 via the intermediate layer 4.

[0021] The thickness of the single-layer photosensitive layer 3a is not particularly limited, but is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0022] The thickness of the protective layer 5 is not particularly limited, but is more preferably 1 μm to 30 μm, even more preferably 1 μm to 4 μm, and particularly preferably 2 μm to 4 μm. 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 Figures 1(a) to (b), 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, the outermost layer among the multiple layers is the surface layer. The structure of a single-layer photoreceptor 1, which is an example of a photoreceptor, has been described above with reference to Figures 1(a) to (b).

[0023] The structure of a multilayer photoreceptor 10, an example of a photoreceptor, will be described below with reference to Figure 2. Figures 2(a) to (c) each show a partial cross-sectional view of the multilayer photoreceptor 10. As shown in Figure 2(a), the multilayer photoreceptor 10 comprises, 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 Figure 2(a), 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 Figure 2(b), in the multilayer photoreceptor 10, the charge transport layer 3c may be provided on the conductive substrate 2, the charge generation layer 3b may be provided on the charge transport layer 3c, and the protective layer 5 may be provided on the charge generation layer 3b. In the examples shown in Figures 2(a) to (b), the photosensitive layer 3 is directly provided on the conductive substrate 2. The protective layer 5 is the outermost layer of the stacked photoreceptor 10.

[0024] As shown in Figure 2(c), the stacked photoreceptor 10 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2, the photosensitive layer 3, and the protective layer 5. In the example shown in Figure 2(c), 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.

[0025] The thickness of the charge generation layer 3b is not particularly limited, but is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 3 μm or less. In the examples shown in FIGS. 2(a) to (c), the charge generation layer 3b is a single layer. However, the charge generation layer 3b may be a plurality of layers.

[0026] The thickness of the charge transport layer 3c is not particularly limited, but is preferably 2 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less. In the examples shown in FIGS. 2(a) to (c), the charge transport layer 3c is a single layer. However, the charge transport layer 3c may be a plurality of layers.

[0027] The protective layer 5 provided in the layered photoreceptor 10 is the same as the protective layer 5 provided in the single-layer photoreceptor 1, and thus the description thereof is omitted. As described above, referring to FIGS. 2(a) to (c), the structure of the layered photoreceptor 10, which is an example of a photoreceptor, has been described. Hereinafter, each component will be further described.

[0028] [Protective layer] The polar component γp of the surface free energy of the protective layer is 25 mJ / m 2 or more and 29 mJ / m 2 or less, and the non-polar component γd of the surface free energy of the protective layer is 13 mJ / m 2 or more and 17 mJ / m 2 or less, which is preferable.

[0029] The protective layer is typically composed of a resin. Hereinafter, the "resin contained in the protective layer" may be simply referred to as "protective layer resin". The protective layer resin may further contain metal oxide particles, and may further contain one or both of a polymerization initiator and an additive as required. The protective layer is adjusted such that the polar component γp and the non-polar component γd of the surface free energy are within the above ranges, particularly the resin component.

[0030] As the protective layer resin, a photocurable resin is preferable from the viewpoint of ease of controlling the polar component γp and the non-polar component γd. Examples of photocurable resins include (meth)acrylic resin and epoxy resin. (Meth)acrylic resin is preferred as the photocurable resin because the photocuring reaction stops when UV irradiation is stopped, and the progress of the photocuring reaction is easy to control. While it is known that using a photocurable resin as the protective layer resin can easily achieve high hardness and excellent durability by improving the crosslinking density, it has the problem of being prone to image flow. In contrast, the present invention makes it possible to suppress image flow even when using a photocurable resin as the protective layer resin by controlling the polar component γp and the nonpolar component γd of the surface free energy, thereby achieving both durability and suppression of image flow.

[0031] The photocurable resin preferably has repeating units derived from a compound having one polymerizable functional group and repeating units derived from a compound having two or more polymerizable functional groups. Hereinafter, "repeating units derived from a compound having one polymerizable functional group" may be referred to as "monofunctional unit," and "a compound having one polymerizable functional group" may be referred to as "monofunctional monomer." Furthermore, "repeating units derived from a compound having two or more polymerizable functional groups" may be referred to as "polyfunctional unit," and "a compound having two or more polymerizable functional groups" may be referred to as "polyfunctional monomer." This makes it easier to adjust the magnitudes of the polar component γp and the nonpolar component γd of the surface free energy.

[0032] Furthermore, the presence of monofunctional and polyfunctional units in the photocurable resin offers the following advantages. Specifically, in the protective layer formation process of photoreceptor manufacturing, monofunctional monomers for forming monofunctional units fill the voids of polyfunctional monomers for forming polyfunctional units, forming a photocurable resin in which polyfunctional and monofunctional units are densely arranged. In addition, since the polyfunctional monomer has two or more polymerizable functional groups, the photocuring reaction in which the polymerizable functional groups react proceeds favorably in the protective layer formation process of photoreceptor manufacturing. As a result, the hardness can be sufficiently increased not only inside the protective layer but also near the surface of the protective layer, which is susceptible to the effects of radicals caused by oxygen in the atmosphere.

[0033] Examples of polymerizable functional groups in monofunctional and polyfunctional units include vinyl groups and epoxy groups. When the photocurable resin is a (meth)acrylic resin, the (meth)acrylic resin has vinyl groups as polymerizable functional groups. When the photocurable resin is an epoxy resin, the epoxy resin has epoxy groups as polymerizable functional groups.

[0034] The photocurable resin may have one monofunctional group unit, or two or more (for example, two) monofunctional group units. Furthermore, the photocurable resin may have one polyfunctional group unit, or two or more (for example, two) polyfunctional group units.

[0035] A preferred example of a polymerizable functional group is a (meth)acryloyl group. A preferred example of a monofunctional unit is a repeating unit derived from the compound represented by formula (EB-1).

[0036] [ka]

[0037] In formula (EB-1), R 1 R represents a chain-like or cyclic alkyl group having 1 to 10 carbon atoms, which may have substituents. 2 R represents a hydrogen atom or a methyl group. 1Substituents include alkoxy groups, saturated heterocyclic groups, aryl groups, halogen atoms, fluoroalkyl groups, or cyano groups. Examples of cyclic alkyl groups include the polycyclic alkyl group isobornyl group and the monocyclic alkyl group cyclohexyl group. Examples of chain alkyl groups include the linear alkyl group n-octyl group and the branched alkyl group isopropyl group. Examples of aryl groups include the phenyl group and the naphthyl group.

[0038] Monofunctional units are formed by polymerizing the polymerizable functional groups of monofunctional monomers. For example, by subjecting a compound represented by formula (EB-1), which is a monofunctional monomer, to a photocuring reaction (more specifically, an addition polymerization reaction of vinyl groups), repeating units represented by formula (EB-1a), which are monofunctional units, are formed.

[0039] [ka]

[0040] * in equation (EB-1a) 3 * represents a bond. * in a repeating unit represented by equation (EB-1a) 3 * in other repeating units represented by formula (EB-1a) 3 , or * in formula (Yb) described later 2 It is bonded to R in equation (EB-1a). 1 and R 2 R in equation (EB-1) 1 and R 2 It is synonymous with [the above].

[0041] As an example of a monofunctional group monomer, compounds represented by formula (EB-1) are preferred, specifically those represented by formulas (CA-1), (CA-2), (CA-3), (CA-4), (CA-5), (CA-6), or (CA-7). Hereinafter, compounds represented by formulas (CA-1), (CA-2), (CA-3), (CA-4), (CA-5), (CA-6), and (CA-7) may be referred to as monofunctional group monomers (CA-1), (CA-2), (CA-3), (CA-4), (CA-5), (CA-6), and (CA-7), respectively. This makes it easier to adjust the polar component γp and the nonpolar component γd of the surface free energy of the protective layer (outermost layer) of the photoreceptor.

[0042] [ka]

[0043] Next, the polyfunctional group units of the photocurable resin will be described. The polyfunctional group units are preferably repeating units derived from a compound having 2 to 10 polymerizable functional groups, and more preferably repeating units derived from a compound having 3 to 6 polymerizable functional groups. Examples of polymerizable functional groups that the polyfunctional group units have are the same as the examples of polymerizable functional groups that the monofunctional group units have already been described.

[0044] Examples of polyfunctional monomers for forming polyfunctional units 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.

[0045] 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.

[0046] The above-mentioned pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate are compounds represented by the following formulas (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 formulas (EA-1), (EA-2), (EA-3), and (EA-4), and more preferably a repeating unit derived from one or two. Hereinafter, the compounds represented by formulas (EA-1), (EA-2), (EA-3), and (EA-4) may be referred to as polyfunctional group monomers (EA-1), (EA-2), (EA-3), and (EA-4), respectively.

[0047] [ka]

[0048] 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), repeating units represented by formulas (EA-1a), (EA-2a), (EA-3a), and (EA-4a), which are polyfunctional units, are formed from compounds represented by formulas (EA-1), (EA-2), (EA-3), and (EA-4), which are polyfunctional monomers.

[0049] [ka]

[0050] Y in equation (EA-1a)1 ~Y 3 At least one of them represents a group represented by formula (Yb), and Y 1 ~Y 3 The remaining part represents the base expressed by equation (Ya). Y in equation (EA-2a) 4 ~Y 7 At least one of them represents a group represented by formula (Yb), and Y 4 ~Y 7 The remaining part represents the group expressed by equation (Ya). Y in equation (EA-3a) 8 ~Y 12 At least one of them represents a group represented by formula (Yb), and Y 8 ~Y 12 The remaining part represents the group represented by equation (Ya). Y in equation (EA-4a) 13 ~Y 18 At least one of them represents a group represented by formula (Yb), and Y 13 ~Y 18 The remaining part represents the base expressed by formula (Ya).

[0051] [ka]

[0052] * in equations (Ya) and (Yb) 1 * is a bond that attaches to the carbon atom of the carbonyl group in formulas (EA-1a) to (EA-4a). 2 This is the * that other repeating units have 2 or * 3 This is a bond that connects to the group represented by formula (Yb) of a repeating unit. 2 and the base represented by formula (Yb) of the other repeating units * 2 Or the * in formula (EB-1a) 3 They are connected to each other.

[0053] Through a photocuring reaction (more specifically, an addition polymerization reaction of vinyl groups), the double bond of the group represented by formula (Ya) is cleaved, and the group represented by formula (Yb) is formed. Therefore, as the photocuring reaction (more specifically, the addition polymerization reaction of vinyl groups) proceeds, the number of groups represented by formula (Ya) decreases and the number of groups represented by formula (Yb) increases.

[0054] The content of the photocurable resin 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, relative to the mass of the protective layer.

[0055] Preferably, the metal oxide particles include alumina particles in addition to tin oxide particles. Tin oxide particles and alumina particles have relatively high hardness, which can improve the wear resistance of the photoreceptor. Furthermore, since the electrical resistance of alumina particles is higher than that of tin oxide particles, the inclusion of alumina particles in the protective layer allows the photoreceptor to be sufficiently charged, improving the charging characteristics of the photoreceptor and contributing to the suppression of image blurring.

[0056] 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. Due to their high UV absorption efficiency, acylphosphine oxide compounds are preferred as photopolymerization initiators. Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and lithiumphenyl(2,4,6-trimethylbenzoyl)phosphonate. The content of the polymerization initiator is preferably 1% to 20% by mass, and more preferably 5% to 10% by mass, relative to the mass of the protective layer.

[0057] Examples of additives contained in the protective layer include leveling agents (e.g., silicone oil and leveling agents having halogen atoms) and other known additives. As for the leveling agent, a leveling agent having halogen atoms is preferred, an acrylic polymer having halogen atoms is more preferred, a fluorosilicone-modified acrylic polymer is even more preferred, and a UV-curable fluorosilicone-modified acrylic polymer is particularly preferred. The leveling agent preferably has polymerizable functional groups. When the leveling agent has polymerizable functional groups, the photocurable resin has repeating units derived from the leveling agent as repeating units. When the leveling agent has polymerizable functional groups, 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, and more preferably 260 g / mol or more and 450 g / mol or less. Furthermore, it is preferable that the protective layer does not contain charge generating agents, hole transporters, and electron transporters.

[0058] [Photosensitive layer] The photosensitive layer typically contains a hole transporter, a charge generator, and a binder resin. When the photoreceptor is a single-layer photoreceptor, the single-layer photosensitive layer contains a charge generator, a hole transporter, and a binder resin. Preferably, the single-layer photosensitive layer further contains an electron transporter. The single-layer photosensitive layer may further contain additives as needed.

[0059] If 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 as needed. The charge generation layer and the charge transport layer may each further contain additives as needed. 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 each contain a radical acceptor compound.

[0060] Examples of hole transporters 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'-tetraphenylphenantolylenediamine derivatives, and di(aminophenylethenyl)benzene derivatives), oxadiazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazo Examples of hole transporters include triphenylamine derivatives or diamine derivatives. These include styrene 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. The hole transporter contained in the photosensitive layer of the electrophotographic photoreceptor of the present invention is preferably a triphenylamine derivative or a diamine derivative.

[0061] In particular, from the viewpoint of improving the sensitivity characteristics of the photoreceptor, it is preferable that the hole transporter 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 transporters (1), (2), and (3), respectively. Improving the sensitivity characteristics of the photoreceptor makes it easier to suppress the occurrence of image blurring.

[0062] [ka]

[0063] In general formula (1), R 11 , R 12 , R 13 and R 14 Each of these independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a hydrogen atom.

[0064] In general formula (1), R 11 , R 12 , R 13 and R 14 Each of these groups is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group.

[0065] In general formula (2), R 21 and R 22 Each of these independently represents an alkyl group or hydrogen atom having 1 to 6 carbon atoms.

[0066] In general formula (2), R 21 and R 22 Each of these groups is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group.

[0067] In general formula (3), R 31 , R 32 , R 33 , R 34 , R 35 , and R 36 Each of the following independently represents an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms; each of the following independently represents an integer between 0 and 5; and each of the following independently represents an integer between 0 and 4.

[0068] In general formula (3), R 31 , R 32 , R 33 , R 34 , R 35 and R 36 r, s, v, w, t, and u preferably represent an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group.

[0069] The compound represented by general formula (1) is preferably the compound represented by chemical formula (HT-3), which will be described later in the examples (hereinafter sometimes referred to as compound (HT-3)). The compound represented by general formula (2) is preferably the compound represented by chemical formula (HT-4), which will be described later in the examples (hereinafter sometimes referred to as compound (HT-4)). The compound represented by general formula (3) is preferably the compound represented by chemical formula (HT-6) or (HT-7), which will be described later in the examples (hereinafter sometimes referred to as compound (HT-6) or (HT-7)).

[0070] When the photoreceptor is a single-layer photoreceptor, the hole transporter content 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, per 100 parts by mass of binder resin.

[0071] To improve the sensitivity characteristics of the photoreceptor, when the photoreceptor is a single-layer type photoreceptor, the total content of hole transporters and electron transporters 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 photoreceptor.

[0072] When the photoreceptor is a laminated photoreceptor, the hole transporter content 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, per 100 parts by mass of binder resin.

[0073] To improve the sensitivity characteristics of the photoreceptor, when the photoreceptor is a multilayer photoreceptor, the content of the hole transporter is preferably 40.0% by mass or more, and more preferably 40.0% by mass or more and 60.0% by mass or less, relative to the mass of the charge transport layer.

[0074] Examples of charge generating agents include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metallic naphthalocyanine pigments, squaline pigments, indigo pigments, azulenium pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g., selenium, selenium-tellurium, selenium-arsenide, cadmium sulfide, and amorphous silicon), pyryllium pigments, ancencelon pigments, triphenylmethane pigments, surene pigments, toluidine pigments, pyrazoline pigments, and quinacridone pigments.

[0075] Phthalocyanine pigments have a phthalocyanine structure. Examples of phthalocyanine pigments include metallic phthalocyanines and metal-free phthalocyanines. Examples of metallic phthalocyanines include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. Titanyl phthalocyanine is preferred as the metallic phthalocyanine. Titanyl phthalocyanine is represented by formula (CG-1). Metal-free phthalocyanines are represented by formula (CG-2).

[0076] [ka]

[0077] Phthalocyanine pigments 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).

[0078] For example, in digital optical image forming apparatuses (e.g., laser beam printers or facsimile machines using light sources such as semiconductor lasers), it is preferable to use a photoreceptor that is sensitive to wavelengths of 700 nm or more. As a charge generating agent, phthalocyanine-based pigments are preferred because they have a high quantum yield in the wavelength range 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.

[0079] Y-type titanyl phthalocyanine has a major peak at, for example, 27.2° of the Bragg angle (2θ±0.2°) in its CuKα-characterized X-ray diffraction spectrum. The major peak in a CuKα-characterized X-ray diffraction spectrum is the peak with the first or second highest intensity in the range where the Bragg angle (2θ±0.2°) is between 3° and 40°. Y-type titanyl phthalocyanine does not have a peak at 26.2° in its CuKα-characterized X-ray diffraction spectrum.

[0080] The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, the sample (titanyl phthalocyanine) is placed in the sample holder of an X-ray diffractometer (for example, RIGAK Corporation's "RINT(registered trademark) 1100"), and the X-ray diffraction spectrum is measured under the following conditions: X-ray tube Cu, tube voltage 40kV, tube current 30mA, and CuKα characteristic X-ray wavelength 1.542Å. 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.

[0081] When the photoreceptor is a single-layer photoreceptor, the charge generating agent content is preferably 0.1 parts by mass or more and 50 parts by mass or less, and more preferably 0.5 parts by mass or more and 30 parts by mass or less, per 100 parts by mass of the binder resin. When the photoreceptor is a multilayer photoreceptor, the charge generating agent content is preferably 10 parts by mass or more and 300 parts by mass or less, and more preferably 100 parts by mass or more and 200 parts by mass or less, per 100 parts by mass of the base resin.

[0082] 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.

[0083] When the photoreceptor is a single-layer photoreceptor, the content of the electron transport agent is preferably 5 parts by mass or more and 150 parts by mass or less, and preferably 10 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the binder resin.

[0084] 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 resins and urethane-acrylic acid copolymers).

[0085] Among these resins, polycarbonate resin is preferred because it provides a single-layer photosensitive layer and charge transport layer with an excellent balance of processability, mechanical strength, optical properties, and abrasion resistance. Examples of polycarbonate resins include bisphenol Z type polycarbonate resin, bisphenol B type polycarbonate resin, bisphenol ZC type polycarbonate resin, bisphenol C type polycarbonate resin, and bisphenol A type polycarbonate resin. As the binder resin, bisphenol Z type polycarbonate resin or bisphenol B type polycarbonate resin is preferred. Bisphenol Z type polycarbonate resin is a resin having repeating units represented by the formula (BisZ). Bisphenol B type polycarbonate resin is a resin having repeating units represented by the formula (BisB).

[0086] [ka]

[0087] The base resin contained in the charge generation layer is the same as the binder resin contained in the charge transport layer. However, in order to suitably form the charge generation layer and the charge transport layer, it is preferable to select a resin as the base resin that is different from the resin used as the binder resin from the above examples of binder resins. The base resin is, for example, polyvinyl acetal resin.

[0088] Additives contained in the photosensitive layer include, for example, UV absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, bulking agents, thickening agents, dispersion stabilizers, waxes, donors, surfactants, plasticizers, sensitizers, electron acceptor compounds, and leveling agents. Examples of leveling agents include silicone oil, and more specifically, dimethyl silicone oil.

[0089] [Middle class] The presence of an intermediate layer allows for a degree of insulation sufficient to suppress leakage, while facilitating the flow of current generated when the photoreceptor is exposed, thereby suppressing an increase in resistance. The intermediate layer (undercoat) contains, for example, one or both of inorganic particles and organic particles, and a resin used in the intermediate layer (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 intermediate layer particles to the mass of intermediate layer resin is, for example, 1 to 4. The thickness of the intermediate layer is, for example, 0.1 μm to 5 μm.

[0090] Examples of inorganic particles for the intermediate layer include white pigments (more specifically, titanium dioxide, zinc oxide, zinc oxide, zinc sulfide, lead white, and lithopone, etc.) and extender pigments (more specifically, alumina, calcium carbonate, and barium sulfate, etc.). Examples of organic particles for the intermediate layer include fluororesin particles, benzoguanamine resin particles, and styrene resin particles. The number-mean primary particle size of the intermediate layer particles is preferably 100 nm or less, and more preferably 1 nm to 50 nm. Inorganic particles are preferred for the intermediate layer particles, and titanium dioxide is more preferred. Titanium dioxide may be surface-treated. Surface treatment of titanium dioxide may be performed once or multiple times (for example, twice). Examples of surface treatment agents used for surface treatment of titanium dioxide include alumina, silica, and organosilicon compounds (for example, polysiloxane, more specifically, methylhydrogenpolysiloxane).

[0091] Examples of intermediate layer resins are the same as examples of binder resins contained in the photosensitive layer. However, in order to suitably form the photosensitive layer, it is preferable to select an intermediate layer resin from the above examples of binder resins that is different from the resin used as the binder resin. The intermediate layer resin is, for example, a polyamide resin.

[0092] [Conductive substrate] The conductive substrate is not particularly limited, and only needs to be composed of a material whose surface is conductive. An example of a conductive substrate is a conductive substrate composed 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 to form an alloy (more specifically, an aluminum alloy, stainless steel, or brass, etc.). Aluminum and aluminum alloys are preferred as conductive materials because they allow for 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 conductive substrate shapes include sheet-like and drum-like shapes. The thickness of the conductive substrate is appropriately selected according to the shape of the conductive substrate.

[0093] [Method for manufacturing photoreceptors] Next, an example of a method for manufacturing a photoreceptor according to the first embodiment will be described. The method for manufacturing a photoreceptor according to the first embodiment includes, for example, a photosensitive layer formation step and a protective layer formation step.

[0094] (Photosensitive layer formation process for single-layer photoreceptors) The photosensitive layer formation process for a single-layer photoreceptor is described below. The photosensitive layer formation process for a single-layer photoreceptor includes a single-layer photosensitive layer formation process. In the single-layer photosensitive layer formation process, a coating solution for forming a single-layer photosensitive layer (hereinafter sometimes referred to as a single-layer photosensitive layer coating solution) is prepared. The single-layer photosensitive layer coating solution contains, for example, a charge generating agent, a hole transporter, a binder resin, a solvent, an electron transporter if necessary, and additives if necessary. The single-layer photosensitive layer coating solution is prepared by mixing these. Next, the single-layer photosensitive layer coating solution is applied onto a conductive substrate. Then, at least a portion of the solvent contained in the applied photosensitive layer coating solution is removed to form a single-layer photosensitive layer.

[0095] (Photosensitive layer formation process for stacked photoreceptors) The photosensitive layer formation process for a stacked photoreceptor will be described below. The photosensitive layer formation process for a stacked photoreceptor includes a charge generation layer formation process and a charge transport layer formation process.

[0096] In the charge generation layer formation step, a coating solution for forming the charge generation layer (hereinafter sometimes referred to as the charge generation layer coating solution) is prepared. The charge generation layer coating solution contains, for example, a charge generating agent, a base resin, a solvent, and additives as needed. The charge generation layer coating solution is prepared by mixing these components. Next, the charge generation layer coating solution is applied onto a conductive substrate. Then, at least a portion of the solvent contained in the applied charge generation layer coating solution is removed to form the charge generation layer.

[0097] In the charge transport layer formation process, a coating solution for forming the charge transport layer (hereinafter sometimes referred to as the charge transport layer coating solution) is prepared. The charge transport layer coating solution contains a hole transport agent, a binder resin, a solvent, and additives as needed. The charge transport layer coating solution is prepared by mixing these components. Next, the charge transport layer coating solution is applied onto the charge generating layer. Then, at least a portion of the solvent contained in the applied charge transport layer coating solution is removed to form the charge transport layer.

[0098] (Protective layer formation process) In the protective layer formation process, a protective layer is formed on the photosensitive layer. First, a coating solution for forming the protective layer (hereinafter sometimes referred to as the protective layer coating solution) is prepared. The protective layer coating solution contains at least one compound for forming the protective layer resin, a solvent, and optionally a polymerization initiator, metal oxide particles, and / or additives. The protective layer coating solution is prepared by mixing these. Next, the protective layer coating solution is applied onto the photosensitive layer. Then, at least one compound for forming the protective layer resin contained in the protective layer coating solution on the photosensitive layer is polymerized. By polymerization, the polymerized protective layer resin is formed.

[0099] When the protective layer resin is a photocurable resin, irradiating the protective layer coating solution with ultraviolet light polymerizes at least one of the compounds for forming the protective layer resin contained in the protective layer coating solution. The ultraviolet light irradiated in the protective layer formation step is, for example, irradiated from a light-emitting diode light source. In order to allow the photocuring reaction to proceed favorably, the wavelength of the ultraviolet light irradiated in the protective layer formation step is preferably 200 nm to 420 nm, more preferably 270 nm to 420 nm, even more preferably 270 nm to 400 nm, and particularly preferably 365 nm. The light energy of the ultraviolet light irradiated in the protective layer formation step is preferably 10,000 mW·s to 100,000 mW·s, and more preferably 60,300 mW·s to 86,400 mW·s. If the light energy of the ultraviolet light is 10,000 mW·s or more, the photocuring reaction will proceed sufficiently and the protective layer can be sufficiently cured. If the power output is 100,000 mW·s or less, the decomposition of the hole transporter contained in the photosensitive layer can be further suppressed, improving the sensitivity characteristics of the photoreceptor.

[0100] The photosensitive layer formation process and the protective layer formation process have been described above. The method for manufacturing the photoreceptor according to the first embodiment will now be described further.

[0101] The solvents contained in the above-mentioned single-layer photosensitive layer coating solution, charge generation layer coating solution, charge transport layer coating solution, and protective layer coating solution (hereinafter, these may be collectively referred to as "coating solution") are not particularly limited, as long as they can dissolve or disperse each component contained in the coating solution. 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.

[0102] The coating solution is prepared by mixing each component and dissolving or dispersing them in a solvent. For mixing, for example, a bead mill, ball mill, roll mill, paint shaker, or ultrasonic disperser can be used.

[0103] The method of applying the coating solution is not particularly limited, as long as it allows for uniform application of the coating solution. Examples of application methods include dip coating, spray coating, bead coating, blade coating, and roller coating.

[0104] Methods for removing at least a portion of the solvent contained in the above-mentioned single-layer photosensitive layer coating solution, charge generation layer coating solution, and charge transport layer coating solution include, for example, heating, reduced pressure, or a combination of heating and reduced pressure. More specifically, a method of heat treatment (hot air drying) using a high-temperature dryer or a reduced-pressure dryer is used. The heat treatment temperature is, for example, 40°C to 150°C. The heat treatment time is, for example, 3 minutes to 150 minutes.

[0105] The method for manufacturing a photoreceptor according to the first embodiment may further include an intermediate layer formation step of forming an intermediate layer on a conductive substrate, if necessary. The intermediate layer formation step may be carried out by appropriately selecting a known method.

[0106] [Substituent] The substituents used in this specification are described below. Examples of halogen atoms (halogen groups) include fluorine atoms (fluoro groups), chlorine atoms (chloro groups), bromine atoms (bromo groups), and iodine atoms (iodine groups).

[0107] Unless otherwise specified, alkyl groups having 1 to 6 carbon atoms are linear or branched and unsubstituted. Examples of alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-ethylpropyl group, 2-ethylpropyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group, 1-ethylbutyl group, 2-ethylbutyl group, and 3-ethylbutyl group. Examples of alkyl groups having 1 to 3 carbon atoms are, each, groups among those listed as examples of alkyl groups having 1 to 6 carbon atoms that have the corresponding number of carbon atoms.

[0108] Unless otherwise specified, alkoxy groups having 1 to 6 carbon atoms are linear or branched and unsubstituted. Examples of alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, 1-methylbutoxy, 2-methylbutoxy, 3-methylbutoxy, 1-ethylpropoxy, 2-ethylpropoxy, 1,1-dimethylpropoxy, 1,2-dimethylpropoxy, 2,2-dimethylpropoxy, n-hexyloxy, and 1-methylpropoxy. Examples include the methylpentyloxy group, 2-methylpentyloxy group, 3-methylpentyloxy group, 4-methylpentyloxy group, 1,1-dimethylbutoxy group, 1,2-dimethylbutoxy group, 1,3-dimethylbutoxy group, 2,2-dimethylbutoxy group, 2,3-dimethylbutoxy group, 3,3-dimethylbutoxy group, 1,1,2-trimethylpropoxy group, 1,2,2-trimethylpropoxy group, 1-ethylbutoxy group, 2-ethylbutoxy group, and 3-ethylbutoxy group.

[0109] <Second Embodiment: Image Forming Apparatus> Next, with reference to Figure 3, an image forming apparatus 100, which is an example of an image forming apparatus of a second embodiment of the present invention, will be described. Figure 3 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-type color printer.

[0110] As shown in Figure 3, the image forming apparatus 100 comprises a control unit 15, an operating unit 20, a paper feeding unit 30, a transport 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.

[0111] The control unit 15 controls the operation of each part of 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 memory such as 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.

[0112] The operation unit 20 receives instructions from the user. Upon receiving instructions from the user, the operation unit 20 transmits a signal indicating the user's instructions to the control unit 15. As a result, the image forming operation by the image forming apparatus 100 is started.

[0113] The paper feeding unit 30 includes a paper feeding cassette 31 and a group of paper feeding rollers 32. The paper feeding cassette 31 can accommodate multiple recording media P (for example, paper). The group of paper feeding rollers 32 feeds the recording media P stored in the paper feeding cassette 31 one sheet at a time to the transport unit 40.

[0114] The transport unit 40 is equipped with rollers and guide members. The transport unit 40 extends from the paper feeding unit 30 to the discharge unit 90. The transport unit 40 transports the recording medium P from the paper feeding unit 30 to the discharge unit 90, passing through the image forming unit 60 and the fixing device 80.

[0115] The toner supply unit 50 supplies toner to the image forming unit 60. The toner supply unit 50 comprises a first mounting unit 51Y, a second mounting unit 51C, a third mounting unit 51M, and a fourth mounting unit 51K.

[0116] The first toner container 52Y is mounted in the first mounting section 51Y. Similarly, the second toner container 52C is mounted in the second mounting section 51C, the third toner container 52M is mounted in the third mounting section 51M, and the fourth toner container 52K is mounted in the fourth mounting section 51K.

[0117] The first toner container 52Y, the second toner container 52C, the third toner container 52M, and the fourth toner container 52K each contain 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.

[0118] The image forming unit 60 comprises an exposure apparatus 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.

[0119] Each of the first image forming units 62Y to the fourth image forming unit 62K includes a charging device 63, a developing device 64, an image carrier 65, a cleaning device 66, and a static elimination device 67.

[0120] Note that the configurations of the first image forming unit 62Y to the fourth image forming unit 62K are the same except for the type of toner supplied from the toner supply unit 50. Therefore, in Figure 3, the reference numerals are omitted for the components of the second image forming unit 62C to the fourth image forming unit 62K.

[0121] The image carrier 65 is the photoreceptor of the first embodiment (more specifically, the single-layer photoreceptor 1 and the stacked photoreceptor 10). As described in the first embodiment, the photoreceptor of the first embodiment can suppress the occurrence of image flow. Therefore, the image forming apparatus 100 of the second embodiment can suppress the occurrence of image flow. The image forming apparatus 100 of the second embodiment may include an image carrier 65, a charging device for charging the surface of the image carrier, an exposure device 61 for exposing the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier, a developing device 64 for supplying toner to the surface of the image carrier to develop the electrostatic latent image as a toner image, and a transfer device 70 for transferring the toner image from the image carrier to a transfer target. Furthermore, the image forming apparatus 100 of the second embodiment may further include, from the viewpoint of further suppressing the occurrence of image flow, one or both of a cleaning device 66 for collecting toner adhering to the surface of the image carrier and a static elimination device 67 for removing static electricity from the surface of the image carrier.

[0122] In the second embodiment, the image carrier 65 rotates in the direction indicated by arrow R1 in Figure 3 (clockwise in Figure 3). The charging device 63, developing device 64, cleaning device 66, and static elimination device 67 are arranged along the circumferential surface of the image carrier 65 in the order listed from the upstream side in the rotational direction of the image carrier 65.

[0123] 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 discharge. The charging device 63 is, for example, a charging roller.

[0124] The exposure apparatus 61 exposes the surface of the charged image carrier 65. More specifically, the exposure apparatus 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.

[0125] The developing device 64 receives toner 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 as a toner image.

[0126] 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. As a result, a yellow toner image is formed on the surface of the image carrier 65 of the first image forming unit 62Y.

[0127] 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 devices 64 of the second image forming unit 62C, the third image forming unit 62M, and the fourth image forming unit 62K are supplied with cyan toner, magenta toner, and black toner, respectively. As a result, cyan toner images, magenta toner images, and black toner images are formed on the surfaces of the image carrier 65 of the second image forming unit 62C, the third image carrier 65 of the third image forming unit 62M, and the fourth image carrier 65 of the fourth image forming unit 62K, respectively.

[0128] The cleaning device 66 includes a cleaning member 661 and a scraping roller 662. After transfer by the primary transfer roller 71, which will be 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 scraping roller 662 scrapes the surface of the image carrier 65 to polish the surface of the image carrier 65.

[0129] The static elimination device 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.

[0130] The transfer device 70 transfers the toner image from the image carrier 65 to the recording medium P, which is the object to be transferred. 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 onto the recording medium P. In the second embodiment, the transfer device 70 transfers each toner image onto the recording medium P using 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.

[0131] The intermediate transfer belt 72 is an endless belt stretched over 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 Figure 3. The driven roller 74 is rotationally driven in accordance with the drive of the intermediate transfer belt 72.

[0132] The first image forming unit 62Y to the fourth image forming unit 62K are arranged facing the lower surface of the intermediate transfer belt 72. In the second embodiment, the first image forming unit 62Y to the fourth image forming unit 62K are arranged in the order of the first image forming unit 62Y to the fourth image forming unit 62K from the upstream side to the downstream side in the driving direction D of the lower surface of the intermediate transfer belt 72.

[0133] Each primary transfer roller 71 is positioned opposite each image carrier 65 via an intermediate transfer belt 72 and is pressed toward each image carrier 65. As a result, the toner images formed on the surface of each image carrier 65 are sequentially transferred to the intermediate transfer belt 72 by each primary transfer roller 71. In the second embodiment, yellow toner images, cyan toner images, magenta toner images, and black toner images are transferred to the intermediate transfer belt 72 in this order. Hereinafter, the toner image formed by the superimposition of yellow toner images, cyan toner images, magenta toner images, and black toner images may be referred to as a "layered toner image".

[0134] The secondary transfer roller 75 is positioned opposite the drive roller 73 via the intermediate transfer belt 72. The secondary transfer roller 75 is pressed toward the drive roller 73. This forms a transfer nip between the secondary transfer roller 75 and the drive roller 73. As the recording medium P passes through the transfer nip, the secondary transfer roller 75 transfers the laminated toner image on the intermediate transfer belt 72 to the recording medium P. In the second embodiment, the yellow toner image, cyan toner image, magenta toner image, and black toner image are transferred to the recording medium P in this order, from top to bottom. The recording medium P on which the laminated toner image has been transferred is transported toward the fuser 80 by the transport unit 40.

[0135] The fixing device 80 includes a heating element 81 and a pressurizing element 82. The heating element 81 and the pressurizing element 82 are arranged facing each other to form a fixing nip. The recording medium P, transported from the image forming unit 60, is heated to a predetermined fixing temperature and pressurized as it passes through the fixing nip. As a result, the stacked toner image is fixed to the recording medium P. The recording medium P is transported from the fixing device 80 to the discharge unit 90 by the transport unit 40.

[0136] The discharge unit 90 includes a pair of discharge rollers 91 and a discharge tray 93. The pair of discharge rollers 91 transports the recording medium P to the discharge tray 93 via a discharge port 92. The discharge port 92 is formed on the upper part of the image forming apparatus 100.

[0137] The image forming apparatus 100, an example of an image forming apparatus of the second embodiment, has been described above with reference to Figure 3. 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 only needs to have 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 (for example, a scorotron charger, a charging brush, or a scorotron charger). The image forming apparatus may employ a one-component development method using a one-component developer. The image forming apparatus may employ a development method other than the touchdown development method (for example, a development method in which there is no developing roller and the magnetic roller also serves as the developing roller). The image forming apparatus may employ a direct transfer method. When the image forming apparatus employs a direct transfer method, the toner image is directly transferred from the image carrier to the recording medium while the image carrier is in contact with the recording medium. The image forming apparatus does not need to be equipped with a cleaning device. The image forming apparatus does not need to be equipped with a static elimination device. The image forming apparatus of the second embodiment has been described above.

[0138] <Third Embodiment: Process Cartridge> Next, with continued reference to Figure 3, a process cartridge of a third embodiment of the present invention will be described. The process cartridge of the third embodiment corresponds to each of the first image forming units 62Y to the fourth image forming unit 62K. The process cartridge comprises an image carrier 65, the image carrier 65 being the photoreceptor of the first embodiment (more specifically, a single-layer photoreceptor 1 and a stacked photoreceptor 10). As described in the first embodiment, the photoreceptor of the first embodiment can suppress the occurrence of image flow. Therefore, the process cartridge of the third embodiment, which comprises the photoreceptor of the first embodiment, can suppress the occurrence of image flow.

[0139] In addition to the image carrier 65, the process cartridge 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 (especially a primary transfer roller 71), a cleaning device (cleaning member 661, abrasive roller 662), and a static elimination device 67. The transfer device 70 (especially the primary transfer roller 71) and the exposure device 61 do not need to be included in the process cartridge. The process cartridge is designed to be detachably attached to the image forming apparatus 100. Therefore, the process cartridge is easy to handle, and if the sensitivity characteristics of the image carrier 65 deteriorate, the process cartridge, including the image carrier 65, can be easily and quickly replaced. The process cartridge of the third embodiment has been described above with reference to Figure 3. [Examples]

[0140] <Examples and Comparative Examples> As examples and comparative examples of this disclosure, photoreceptors were fabricated and evaluated. Note that the following examples are merely illustrative of this disclosure, and this disclosure is not limited to the configurations of the following examples. The following materials were prepared.

[0141] <Prepared raw materials> [Monofunctional monomers] The monofunctional group monomers (CA-1) to (CA-7) described in the embodiment were prepared.

[0142] [Polyfunctional monomers] As polyfunctional monomers, a mixture of polyfunctional monomer (EA-1) and polyfunctional monomer (EA-2) (hereinafter also referred to as polyfunctional monomer (EA-1 / EA-2)) and a mixture of polyfunctional monomer (EA-3) and polyfunctional monomer (EA-4) (hereinafter also referred to as polyfunctional monomer (EA-3 / EA-4)) were prepared as described in the embodiments. Polyfunctional monomer (EA-1 / EA-2): "A-TMM-3LM-N" manufactured by Shin-Nakamura Chemical Industry Co., Ltd. (mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate; 3 polymerizable functional groups of pentaerythritol triacrylate, 4 polymerizable functional groups of pentaerythritol tetraacrylate, 57% by mass of pentaerythritol triacrylate in the mixture) Polyfunctional monomer (EA-3 / EA-4): "A-DPH" manufactured by Shin-Nakamura Chemical Industry Co., Ltd. (a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate; 5 polymerizable functional groups of dipentaerythritol pentaacrylate, 6 polymerizable functional groups of dipentaerythritol hexaacrylate, hydroxyl value 10 mg KOH / g)

[0143] [Hole transport agent (HTM)] The following hole transporters (HT-1) to (HT-7) were prepared.

[0144] [ka]

[0145] [Other materials] The following polymerization initiator (ST-1) (hereinafter also referred to as polymerization initiator (ST-1)) was prepared as a polymerization initiator to be used in the protective layer. As the binder resin used in the charge transport layer, a resin consisting only of repeating units represented by formula (BisZ) as described in the embodiment (hereinafter also simply referred to as polycarbonate resin (BisZ)) was prepared.

[0146] [ka]

[0147] <Manufacturing of stacked photoconductors> By adjusting the types of monofunctional and polyfunctional monomers in the resin component of the protective layer, we manufactured stacked photoreceptors (A-1) to (A-13) in which the nonpolar component γp and polar component γd of the surface free energy of the protective layer were adjusted.

[0148] [Manufacturing of stacked photoreceptor (A-1)] (1) Preparation of the intermediate layer (lower layer) Two parts by mass of titanium dioxide, one part by mass of polyamide resin, ten parts by mass of methanol, one part by mass of butanol, and one part by mass of toluene were mixed using a bead mill for 5 hours to obtain a mixture. As the titanium dioxide, prototype "SMT-A" manufactured by Teika Co., Ltd. (number average particle size 10 nm, titanium dioxide primary surface-treated with alumina and silica, and then secondary surface-treated with methylhydrogenpolysiloxane) was used. As the polyamide resin, "Amiran® ​​CM8000" manufactured by Toray Industries, Inc. (a quaternary copolymer polyamide resin of polyamide 6, polyamide 12, polyamide 66, and polyamide 610) was used. The obtained mixture was filtered using a 5 μm mesh filter to obtain an intermediate layer coating solution. Next, the intermediate layer coating solution was 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 solution was dried at 130°C for 30 minutes to form an intermediate layer (film thickness: 2 μm) on the conductive substrate.

[0149] (2) Fabrication of the charge generation layer 1.5 parts by mass of Y-type titanyl phthalocyanine, 1 part by mass of polyvinyl acetal resin (Sekisui Chemical Co., Ltd.'s "Eslec BX-5") as a base resin, 40 parts by mass of propylene glycol monomethyl ether, and 40 parts by mass of tetrahydrofuran were mixed using a bead mill for 12 hours to obtain a mixture. The obtained mixture was filtered using a 3 μm mesh filter to obtain a coating solution for the charge generation layer. Next, the coating solution for the charge generation layer was applied to the intermediate layer on a conductive substrate by dip coating. The applied coating solution for the charge generation layer was dried at 50°C for 5 minutes to form a charge generation layer (film thickness: 0.3 μm) on the intermediate layer.

[0150] (3) Fabrication of a charge transport layer 70 parts by mass of a hole transport agent (HT-4), 100 parts by mass of a bisphenol Z-type polycarbonate resin (BisZ), 0.05 parts by mass of a leveling agent (Shin-Etsu Chemical Co., Ltd. "KF96-50CS"), and 400 parts by mass of tetrahydrofuran were mixed using a roll mill for 24 hours to obtain a coating solution for the charge transport layer. Next, the coating solution for the charge transport layer was applied onto the charge generation layer by dip coating. The applied coating solution for the charge transport layer was dried at 120°C for 40 minutes to form a charge transport layer (film thickness: 20 μm) on the intermediate layer.

[0151] (4) Preparation of protective layer 9.3 parts by mass of tin oxide, 3.5 parts by mass of alumina, 56 parts by mass of polyfunctional monomer (EA-1 / EA-2) (A-TMM-3LM-N, manufactured by Shin-Nakamura Chemical Industry Co., Ltd.: polyfunctional acrylic acid ester), 34 parts by mass of monofunctional monomer (CA-1) (2-MTA, manufactured by Osaka Organic Chemical Industry Co., Ltd.: monofunctional acrylic acid ester), 10 parts by mass of polymerization initiator (ST-1) (OMNIRAD TPO, manufactured by IGM RESINS), leveling agent (KP-423, manufactured by Shin-Etsu Silicone Co., Ltd.), and 110 parts by mass of methanol were mixed using a bead mill for 10 hours to obtain a mixture. The obtained mixture was filtered using a 5 μm mesh filter to obtain a protective layer coating solution. Next, the protective layer coating solution was applied onto the photosensitive layer by dip coating. The applied protective coating solution was irradiated with ultraviolet light at a wavelength of 365 nm under conditions of light energy of 86400 mW·s. Upon irradiation with ultraviolet light, the polyfunctional group monomers (polyfunctional group acrylic acid esters) and monofunctional group monomers (monofunctional group acrylic acid esters) in the protective coating solution polymerized (photocuring reaction), forming a photocurable resin. In this way, a protective layer (film thickness: 3 μm) was formed on the laminated photosensitive layer.

[0152] (5) Measurement of surface free energy Using a contact angle meter (Kyowa Interface Science Co., Ltd., Model DMo-501), 1 μL each of water, PEG200, and tricresyl phosphate were dropped onto a protective layer (the outermost layer of the photoreceptor) that had been humidified for more than 24 hours at 23°C and 50% RH, and the contact angle was read after 3 seconds. Using the obtained contact angles for each solution and the surface tension component values ​​of each solution shown in Table 1 below, the polar component γp and nonpolar component γd of the surface free energy of the protective layer were calculated using the Owens-Wendt-Rable-Kaelble (OWRK) theoretical formula.

[0153] [Table 1]

[0154] [Manufacturing of stacked photoreceptors (A-2) to (A-17)] Except for using the types of monofunctional monomers (CA-1) to (CA-7) and polyfunctional monomers (EA-1) to (EA-4), as well as hole transporters (HT-1) to (HT-7) shown in Table 2, each of the multilayer photoreceptors (A-2) to (A-17) was manufactured using the same method as for the multilayer photoreceptor (A-1), and the polar component γp and nonpolar component γd of their surface free energy were calculated. The results are shown in Table 2. In (A-13) to (A-16), two types of monofunctional monomers were blended in a 1:1 weight ratio. For example, in photoreceptor (A-13), 17 parts by mass each of monofunctional monomer (CA-4) and monofunctional monomer (CA-3) were blended in a 1:1 ratio, for a total of 34 parts by mass of monofunctional monomers.

[0155] [Table 2]

[0156] [Evaluation of stacked photoreceptors] To evaluate the suppression of image flow in the fabricated photoreceptors (A-1) to (A-13), image evaluation (dot reproducibility) and sensitivity characteristics were assessed. For image evaluation and sensitivity characteristic evaluation, a modified color multifunction printer ("Taskalfa 356ci" manufactured by Kyocera Document Solutions Inc.) was used as the evaluation machine. This evaluation machine was equipped with a charging roller made of epichlorohydrin resin with dispersed conductive carbon. The charging polarity of the charging roller was negative, and the applied voltage to the charging roller was a DC voltage. The development method was a two-component development method. The transfer method was an intermediate transfer method. This evaluation machine was equipped with a cleaning device (cleaning blade and friction roller) and a static elimination device. For these evaluations, copy paper ("Multi Paper Super Economy+" sold by ASKUL Corporation) was used as the paper.

[0157] (1) Sensitivity characteristics The sensitivity characteristics were evaluated under low-temperature, low-humidity conditions of 10°C and 10% RH relative humidity. A photoreceptor was mounted in the evaluation machine, and the machine was set so that the photoreceptor's charge potential was -500V. The exposure dose of the exposure device when printing a solid image was set to 1.08 μJ / cm². 2 The settings were adjusted as follows. Using an evaluation machine, image G2 (solid image) was printed on a single sheet of paper, and the surface potential of the photoreceptor after exposure (post-exposure potential VL: negative potential) was measured. Then, the sensitivity characteristics of the photoreceptor were evaluated from the post-exposure potential according to the following criteria. The results are shown in Table 3.

[0158] (Sensitivity characteristics standard) Excellent: The absolute value of VL is 200V or less. Good: The absolute value of VL is greater than 200V and less than 270V. Defect: The absolute value of VL is 270V or higher.

[0159] (2) Image evaluation (reproducibility of dots) The developing container of the evaluation machine described above was filled with cyan developer, and the toner cartridge was filled with cyan toner. The photoreceptors (A-1) to (A-13) manufactured above were mounted in the evaluation machine. Under high temperature and high humidity conditions of 32°C and 80% RH relative humidity, the evaluation machine was used to print image G1 (a pattern image with an image density of 1.6%) onto a single sheet of paper. The dots constituting the printed image G1 were observed using a microscope. The image was then evaluated according to the following criteria. The results are shown in Table 3.

[0160] (Image evaluation criteria) Excellent (A): All dots that should appear within the microscope field of view are printed. Good (B): Some dots are missing from the total number of dots that should be visible in the microscope field of view, but the number of missing dots is less than half. Defective (C): Some of the dots that should appear in the microscope field of view are missing, and the number of missing dots is more than half.

[0161] [Table 3]

[0162] In the photoreceptors (A-1) to (A-13) of Examples 1 to 13, the polar component γp of the surface free energy of the protective layer (outermost layer) is 23 mJ / m 2 More than 31mJ / m 2 The following is true: The nonpolar component γd is 12 mJ / m 2 More than 19mJ / m 2 The results were as follows: These photoreceptors (A-1) to (A-13) showed good image evaluation (dot reproducibility) and sensitivity characteristics, and it was confirmed that image blurring could be effectively suppressed. In particular, the polar component γp of the surface free energy of the outermost layer is 25 mJ / m 2 More than 29mJ / m 2 The following is the result: the nonpolar component γd is 13 mJ / m 2 More than 17mJ / m 2 The following conditions were observed, and it was confirmed that photoreceptors containing hole transporters (HT-3), (HT-4), (HT-6), or (HT-7) exhibited very good sensitivity characteristics, very good image evaluation, and effectively suppressed image flow.

[0163] In the photoreceptor (A-14) of Comparative Example 1, the polar component γp of the surface free energy of the protective layer (outermost layer) is 23 mJ / m 2 More than 31mJ / m 2 The following was observed, but the nonpolar component γd of the surface free energy of the protective layer (outermost layer) was 19 mJ / m 2 It exceeded expectations. In the photoreceptor (A-15) of Comparative Example 2, the polar component γp of the surface free energy of the protective layer (outermost layer) is 23 mJ / m 2 More than 31mJ / m 2 The following was observed, but the nonpolar component γd of the surface free energy of the protective layer (outermost layer) was 12 mJ / m 2 It was less than [amount missing]. In the photoreceptor (A-16) of Comparative Example 3, the nonpolar component γd of the surface free energy of the protective layer (outermost layer) is 12 mJ / m 2 More than 19mJ / m 2 The following was observed, but the polar component γp of the surface free energy of the protective layer (outermost layer) was 31 mJ / m2 exceeded In the photoreceptor (A-17) according to Comparative Example 4, the non-polar component γd of the surface free energy of the protective layer (the outermost surface layer) was 12 mJ / m 2 or more and 19 mJ / m 2 or less, but the polar component γp of the surface free energy of the protective layer (the outermost surface layer) was less than 23 mJ / m 2 and less. Therefore, it was confirmed that there was a defect in the image evaluation and the image flow could not be effectively suppressed.

Industrial Applicability

[0164] The photoreceptor according to the present invention can be used in an image forming apparatus. The process cartridge and the image forming apparatus according to the present invention can be used for forming an image on a recording medium.

Explanation of Signs

[0165] 1: Single-layer photoreceptor 2: Conductive substrate 3: Photosensitive layer 3a: Single-layer photosensitive layer 3b: Charge generation layer 3c: Charge transport layer 4: Intermediate layer 5: Protective layer 10: Laminated photoreceptor 61: Exposure device 63: Charging device 64: Developing device 65: Image carrier 67: Discharging device 70: Transfer device 100: Image forming apparatus 661: Cleaning member 662: Rubbing roller

Claims

1. It comprises a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer, The polar component γp of the surface free energy of the protective layer is 23 mJ / m ２ 31mJ / m or more ２ The following: The nonpolar component γd of the surface free energy of the protective layer is 12 mJ / m ２ 19mJ / m or more ２ The following: The protective layer contains a (meth)acrylic resin having repeating units derived from a compound represented by formula (EB-1), and does not contain a charge generator, a hole transporter, or an electron transporter. Electrophotographic photoreceptor. 【Chemistry 1】 (In formula (EB-1), R1 represents a substituted chain or cyclic alkyl group having 1 to 10 carbon atoms, and R2 represents a hydrogen atom or a methyl group. The substituent of R1 is an alkoxy group, a saturated heterocyclic group, an aryl group, a halogen atom, a fluoroalkyl group, or a cyano group.)

2. An electrophotographic photoreceptor according to Claim 1, The substituent of R1 is an alkoxy group, a saturated heterocyclic group, an aryl group, or a fluoroalkyl group. Electrophotographic photoreceptor.

3. The electrophotographic photoreceptor according to claim 1, The polar component γp of the surface free energy of the protective layer is 25 mJ / m ２ 29mJ / m or more ２ The following: The nonpolar component γd of the surface free energy of the protective layer is 13 mJ / m ２ 17mJ / m or more ２ The following is Electrophotographic photoreceptor.

4. The electrophotographic photoreceptor according to claim 1, The photosensitive layer contains a hole transport agent, The hole transporter comprises at least one compound represented by general formulas (1), (2), and (3). Electrophotographic photoreceptor. 【Chemistry 2】 (In the general formula (1), R １１ , R １２ , R １３ and R １４ each independently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a hydrogen atom.) In the above general formula (2), R ２１ and R ２２ Each of these independently represents an alkyl group or hydrogen atom having 1 to 6 carbon atoms. In the above general formula (3), R ３１ , R ３２ , R ３３ , R ３４ , R ３５ , and R ３６ Each of the following independently represents an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms; each of the following independently represents an integer between 0 and 5; and each of the following independently represents an integer between 0 and 4.

5. A process cartridge comprising an electrophotographic photoreceptor as described in any one of claims 1 to 4.

6. An image carrier comprising an electrophotographic photoreceptor as described in any one of claims 1 to 4, A charging device for charging the surface of the image carrier, An exposure apparatus for exposing the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier, A developing apparatus that supplies toner to the surface of the image carrier and develops the electrostatic latent image as a toner image, A transfer device for transferring the toner image from the image carrier to the transfer target, An image forming apparatus comprising:

7. An image forming apparatus according to claim 6, The system further comprises a cleaning device for collecting the toner adhering to the surface of the image carrier, and one or both of the static elimination device for removing static electricity from the surface of the image carrier. Image forming apparatus.

Images