Electrophotographic photoreceptor for contact charging by DC voltage, process cartridge and image formation device

Abstract

To provide an electrophotographic photoreceptor for contact charging by a DC voltage which is excellent in abrasion suppression property and image deletion suppression property.SOLUTION: An electrophotographic photoreceptor for contact charging by a DC voltage has a conductive substrate, an undercoat layer provided on the conductive substrate, a charge generating layer provided on the undercoat layer, a charge transport layer provided on the charge generating layer, and a surface protective layer provided on the charge transport layer, wherein the surface protective layer is a cured film of a composition containing a reactive charge transport material, has a hydroxy group and a benzene ring structure, and has a value of a peak area of the hydroxyl group to a peak area of the benzene ring structure in a total reflection measurement method of infrared spectroscopic analysis of more than 0.05 and 0.36 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrophotographic photosensitive member for contact charging by DC voltage, a process cartridge and an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses an electrophotographic photoreceptor having at least one photosensitive layer on a conductive support, wherein at least the outermost layer of the photosensitive layer is made of a crosslinked and cured film formed from a compound (I) represented by the following general formula (A) and a compound (II) having a plurality of substituents represented by the following general formula (B), and wherein the crosslinked and cured film has a residual OH group content ratio A defined by the following formula (1) of 2.0 or less and a residual OH group content ratio B defined by the following formula (2) of 0.3 or less. ·General formula (A) FD-Si(R 1 ) (3-a) (OR 2 ) a (wherein F represents a photoelectric subunit, D represents a flexible subunit, and R 1 represents hydrogen, an alkyl group, or a substituted or unsubstituted aryl group; R 2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group, and a represents an integer of 1 to 3. ·General formula (B) -Si(R 3 ) (3-b) (OR 4 ) b (In the formula, R 3 represents hydrogen, an alkyl group, or a substituted or unsubstituted aryl group; R 4 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group, and b represents an integer of 1 to 3. A = x1 / y (1) B = x2 / y (2) (In the formula, x1 is a 3500 to 3300 cm -1 represents the absorbance of the infrared absorption peak at 955-890 cm due to the OH stretching vibration.-1 represents the absorbance of the infrared absorption peak at 1740-1700 cm due to the CO stretching vibration of the carbonyl bond. -1 It represents the absorbance of the infrared absorption peak at [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-314980 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide an electrophotographic photoreceptor for contact-charging by DC voltage, which has a conductive substrate, an undercoat layer, a charge generating layer, a charge transport layer, and a surface protective layer, wherein the surface protective layer is a cured film of a composition containing a reactive charge transport material, and which, when contact-charging by DC voltage, is superior in wear suppression and image flow suppression properties compared to cases where the value of the peak area of ​​a hydroxy group / peak area of ​​a benzene ring structure, as determined by a total reflection measurement method in infrared spectroscopy, is 0.05 or less or exceeds 0.36. [Means for solving the problem]

[0005] Specific means for solving the above problems include the following aspects. <1> 1. An electrophotographic photoreceptor for contact charging by DC voltage, comprising: a conductive substrate; an undercoat layer provided on the conductive substrate; a charge generating layer provided on the undercoat layer; a charge transport layer provided on the charge generating layer; and a surface protective layer provided on the charge transport layer, wherein the surface protective layer is a cured film of a composition containing a reactive charge transport material, has a hydroxy group and a benzene ring structure, and has a value of a peak area of ​​the hydroxy group / a peak area of ​​the benzene ring structure that is greater than 0.05 and is not greater than 0.36 in total reflection measurement method of infrared spectroscopy. <2> The surface protective layer is a cured film of a composition containing a compound having a hydroxy group and a compound having no hydroxy group and a benzene ring structure. <1> 2. The electrophotographic photoreceptor for contact charging by a DC voltage according to claim 1. <3> The compound having a hydroxy group is the reactive charge transport material. <2> 2. The electrophotographic photoreceptor for contact charging by a DC voltage according to claim 1. <4> The compound having a hydroxy group is a compound having a triarylamine structure. <2> or <3> 2. The electrophotographic photoreceptor for contact charging by a DC voltage according to claim 1. <5> The compound having no hydroxy group and a benzene ring structure is a compound having a triarylamine structure. <2> ~ <4> 10. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 9, <6> The mass ratio MH / MB of the content MH of the compound having a hydroxy group to the content MB of the compound having no hydroxy group and a benzene ring structure in the composition is 5 or more and 20 or less. <2> ~ <5> 10. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 9, <7> The surface protective layer does not have a carboxy group. <1> ~ <6> 10. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 9, <8> The surface protective layer does not contain silicon atoms. <1> ~ <7> 10. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 9, <9> <1> ~ <8> 13. A process cartridge comprising the electrophotographic photosensitive member for contact charging by DC voltage according to any one of claims 1 to 12, which is detachably mountable to an image forming apparatus and contact-charges the electrophotographic photosensitive member by DC voltage. <10> <1> ~ <8> an electrophotographic photosensitive member for contact charging by DC voltage according to any one of claims 1 to 5, a charging device for contact-charging a surface of the electrophotographic photosensitive member by DC voltage, an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photosensitive member, a developing device for developing the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image, and a transfer device for transferring the toner image onto the surface of a recording medium. Effect of the Invention

[0006] <1> or <2> According to the invention, there is provided an electrophotographic photoreceptor for contact-charging by DC voltage, which has a conductive substrate, an undercoat layer, a charge generating layer, a charge transport layer, and a surface protective layer, wherein the surface protective layer is a cured film of a composition containing a reactive charge transport material, and which, when contact-charging by DC voltage, is superior in wear suppression and image flow suppression properties compared to a case in which the value of the peak area of ​​a hydroxy group / peak area of ​​a benzene ring structure is 0.05 or less or exceeds 0.36, as measured by a total reflection measurement method in infrared spectroscopy. <3> According to the present invention, there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in wear suppression and image deletion suppression properties than a case in which the reactive charge transport material is composed solely of a compound that does not have a hydroxy group and has a benzene ring structure. <4> According to the present invention, there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in wear suppression and image flow suppression properties than when the compound having a hydroxy group does not have a triarylamine structure but has a mono- or diarylamine structure. <5> According to the invention, there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in wear suppression and image flow suppression properties than a compound having no hydroxy group and a benzene ring structure but no triarylamine structure, and which has a mono- or diarylamine structure. <6> According to the invention, there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is superior in wear suppression and image flow suppression properties to those in which the mass ratio MH / MB of the content MH of the compound having a hydroxy group to the content MB of the compound having no hydroxy group and a benzene ring structure in the composition is less than 5 or exceeds 20. <7> According to the present invention, there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in terms of wear suppression and image deletion suppression properties than when the surface protective layer contains a carboxy group. <8> According to the present invention, there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in terms of wear suppression and image deletion suppression properties than when the surface protective layer contains silicon atoms. <9> or <10> According to the invention, there is provided a process cartridge or image forming apparatus, in which an electrophotographic photoreceptor which is contact-charged by a DC voltage has a conductive substrate, an undercoat layer, a charge generating layer, a charge transport layer, and a surface protective layer, and the surface protective layer is a cured film of a composition containing a reactive charge transport material, and which is superior in wear suppression and image flow suppression properties compared to cases in which the value of the hydroxyl group peak area / benzene ring structure peak area in a total reflection measurement method of infrared spectroscopy is 0.05 or less or exceeds 0.36. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a schematic partial cross-sectional view showing an example of a layer structure of the electrophotographic photoreceptor according to the present embodiment. [Diagram 2] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present embodiment will be described below. The description and examples are merely illustrative of the embodiment, and are not intended to limit the scope of the embodiment. In this specification, a numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in another step. In addition, in the numerical ranges described in this specification, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. In this specification, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this specification, if multiple substances corresponding to each component are present in the composition, the amount refers to the total amount of the multiple substances present in the composition, unless otherwise specified. In this specification, the term "main component" refers to a major component, for example, a component that accounts for 30% by mass or more of the total mass of a mixture of multiple components.

[0009] (Electrophotographic photoreceptor for contact charging using DC voltage) The electrophotographic photoreceptor for contact charging by DC voltage according to this embodiment (hereinafter also simply referred to as "electrophotographic photoreceptor" or "photoreceptor") has a conductive substrate, an undercoat layer provided on the conductive substrate, a charge generation layer provided on the undercoat layer, a charge transport layer provided on the charge generation layer, and a surface protective layer provided on the charge transport layer, wherein the surface protective layer is a cured film of a composition containing a reactive charge transport material, has a hydroxy group and a benzene ring structure, and the value of the peak area of ​​the hydroxy group / peak area of ​​the benzene ring structure in a total reflection measurement method of infrared spectroscopy is more than 0.05 and is not more than 0.36.

[0010] In conventional electrophotographic photoreceptors having a surface protective layer on the outermost surface to maintain quality over the long term, when contact charging is performed using a DC voltage, making the surface protective layer harder makes it less susceptible to wear, but this reduces the amount of discharge product that can be scraped off, making image flow defects more likely to occur, and so the wear continues to exceed a certain level, making it difficult to achieve both wear resistance and image flow resistance at the same time. In the electrophotographic photoreceptor for contact charging by DC voltage according to this embodiment, the value of the peak area of ​​hydroxyl groups / peak area of ​​benzene ring structure in the total reflection measurement method of infrared spectroscopy analysis of the surface protective layer is greater than 0.05 and not more than 0.36, so that the hydroxyl groups in the surface protective layer are crosslinked and reduced, improving hardness and reducing wear, and since there are fewer hydroxyl groups which are hydrophilic groups, adhesion of water to the surface of the electrophotographic photoreceptor is suppressed, and the combination of water and discharge products and adhesion to the electrophotographic photoreceptor surface is suppressed, the amount of discharge product adhesion is reduced, and the occurrence of image flow due to water and discharge products is suppressed, resulting in excellent wear suppression and image flow suppression.

[0011] Hereinafter, the layer structure of the electrophotographic photoreceptor according to the present embodiment will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of an electrophotographic photoreceptor according to the present embodiment. 1 has a structure in which an undercoat layer 1, a charge generating layer 2, a charge transport layer 3, and a surface protective layer 5 are laminated in this order on a conductive substrate 4. The charge generating layer 2 and the charge transport layer 3 constitute a photosensitive layer. The surface protective layer 5 is a cured film of a composition containing a reactive charge transport material, has a hydroxy group and a benzene ring structure, and has a value of the peak area of ​​the hydroxy group / peak area of ​​the benzene ring structure in a total reflection measurement method of infrared spectroscopy analysis of more than 0.05 and not more than 0.36.

[0012] In the electrophotographic photoreceptor according to the present embodiment, the photosensitive layer is a functionally separated type photosensitive layer in which a charge generating layer 2 and a charge transport layer 3 are separated, as in the photoreceptor 7A shown in Fig. 1. The electrophotographic photoreceptor may include layers other than these layers.

[0013] Hereinafter, the electrophotographic photoreceptor according to the present embodiment will be described in detail for each layer.

[0014] <Surface protective layer> The surface protective layer is provided on the charge transport layer. The surface protective layer is a cured film of a composition containing a reactive charge transport material having a reactive group and a charge transport skeleton in the same molecule. The surface protective layer has a hydroxy group and a benzene ring structure, and the value of the peak area of ​​the hydroxy group / peak area of ​​the benzene ring structure in total reflection infrared spectroscopy is more than 0.05 and not more than 0.36.

[0015] The surface protective layer has a hydroxy group. The hydroxy group may be an alcoholic hydroxy group (= a hydroxy group directly bonded to an aliphatic group) or a phenolic hydroxy group (= a hydroxy group directly bonded to an aromatic group), but the surface protective layer preferably has an alcoholic hydroxy group from the viewpoint of reducing the amount of hydroxy groups present due to the high nucleophilicity of the hydroxy group. The surface protective layer has a benzene ring structure. The substituent on the benzene ring is not particularly limited, and the benzene rings may be bonded to each other, such as in a biphenyl structure.

[0016] The surface protective layer has a hydroxy group and a benzene ring structure, and the value of the peak area of ​​the hydroxy group / peak area of ​​the benzene ring structure in an attenuated total reflectance (ATR) method of infrared spectroscopy (FT-IR analysis) is greater than 0.05 and not more than 0.36. From the viewpoint of abrasion suppression and image flow suppression, the value is preferably 0.07 or more and 0.36 or less, more preferably 0.10 or more and 0.30 or less, and particularly preferably 0.12 or more and 0.25 or less.

[0017] The peak area of ​​the hydroxy group / peak area of ​​the benzene ring structure in the total reflection measurement method of infrared spectroscopy is measured by the method shown below. Infrared spectroscopic analysis conditions Equipment: PerkinElmer Frontier ATR Crystal: Ge Resolution: 4cm -1 Number of scans: 32 The spectrum is ATR corrected. -Peak position- OH group: 3450cm -1 Baseline: 3705cm -1~3257cm -1 Draw with. Benzene ring structure: 820 cm -1 Baseline: 882cm -1 ~776cm -1 Draw with. Calculate the area enclosed by the baseline. The OH group area / benzene ring structure area is used as an index of the amount of residual OH groups.

[0018] The surface protective layer is a layer composed of a cured film of a composition containing a reactive charge transport material having a reactive group and a charge transport skeleton in the same molecule (i.e., a layer containing a polymer or crosslinked product of the reactive charge transport material). The surface protective layer may further contain a non-reactive charge transport material.

[0019] The reactive group of the reactive charge transport material may be a chain polymerizable group, an epoxy group, -OH, -OR (wherein R represents an alkyl group), -NH2, -SH, -COOH, or -SiR. Q1 3-Qn (OR Q2 ) Qn [However, R Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group; R Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group. Qn represents an integer of 1 or more and 3 or less.]. The reactive group in the reactive group-containing non-charge transport material can also be the above-mentioned known reactive groups.

[0020] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, and is, for example, a functional group having a group containing at least a carbon double bond.Specific examples include a group containing at least one selected from a vinyl group, a vinyl ether group, a vinyl thioether group, a styryl group, an acryloyl group, a methacryloyl group, and derivatives thereof.Among them, the chain polymerizable group is preferably a group containing at least one selected from a vinyl group, a styryl group (vinyl phenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof, because of its excellent reactivity.

[0021] Among these, from the viewpoints of abrasion suppression and image flow suppression, the reactive group of the reactive charge transport material is preferably a chain polymerizable group, an epoxy group, -OH, -OR, -NH2, or -SH, more preferably -OH, -OR, -NH2, or -SH, even more preferably -OH or -OR, and particularly preferably -OH.

[0022] The charge transporting skeleton is not particularly limited as long as it is a known structure in an image carrier, and examples thereof include a skeleton derived from a nitrogen-containing hole transporting compound, such as a triarylamine compound (a compound having a triarylamine skeleton), a benzidine compound (a compound having a benzidine skeleton), a hydrazone compound (a compound having a hydrazone skeleton), and the like, and a structure conjugated with a nitrogen atom. Among these, from the viewpoints of charge transportability, wear suppression, and image flow suppression, it is preferable that the charge transporting skeleton contains a triarylamine skeleton.

[0023] The reactive charge transport material having a reactive group and a charge transport skeleton, the non-reactive charge transport material, and the reactive non-charge transport material may be selected from well-known materials.

[0024] The reactive charge transport material may be a reactive charge transport material having a hydroxyl group as a reactive group (hereinafter, also referred to as "specific reactive charge transport material (a)"). The reactive non-charge transport material may be used alone or in combination of two or more kinds.

[0025] The specific reactive charge transport material (a) is preferably a compound represented by the following formula (A) because it has excellent charge transport properties.

[0026] [ka]

[0027] In the formula (A), Ar 1 ~Ar 4 each independently represents a substituted or unsubstituted aryl group; Ar 5 represents a substituted or unsubstituted aryl group or a substituted or unsubstituted arylene group, D represents an organic group having a hydroxy group, c1 to c5 each independently represent an integer of 0 or more and 2 or less, k represents 0 or 1, d represents an integer of 0 or more and 5 or less, e represents 0 or 1, and the total number of Ds is 4 or more.

[0028] In the general formula (A), Ar 1 ~Ar 4 Each independently represents a substituted or unsubstituted aryl group. 1 ~Ar 4 may be the same or different. Here, examples of the substituent in the substituted aryl group include, other than D: an organic group having a hydroxy group, an alkyl group or alkoxy group having 1 to 4 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 10 carbon atoms. Ar 1 ~Ar 4 is preferably any one of the following formulas (1) to (7). In addition, the following formulas (1) to (7) are Ar 1 ~Ar 4 "-(D) C1" or "-(D) C4 "-(D)" which shows the overall C " is shown.

[0029] [ka]

[0030] In the formulas (1) to (7), R 1 represents one selected from the group consisting of a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, a phenyl group substituted with an alkyl group having from 1 to 4 carbon atoms or an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, and an aralkyl group having from 7 to 10 carbon atoms; R 2 ~R 4 each independently represents one member selected from the group consisting of a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, a phenyl group substituted with an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having from 7 to 10 carbon atoms, and a halogen atom; Ar represents a substituted or unsubstituted arylene group; D represents an organic group having a hydroxyl group; c represents 1 or 2; s represents 0 or 1; and t represents an integer of 0 to 3.

[0031] Here, Ar in the formula (7) is preferably represented by the following structural formula (8) or (9).

[0032] [ka]

[0033] In the formulas (8) and (9), R 5 and R 6 each independently represents one member selected from the group consisting of a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms, a phenyl group substituted with an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having from 7 to 10 carbon atoms, and a halogen atom, and each t' represents an integer of from 0 to 3.

[0034] In the formula (7), Z′ represents a divalent organic linking group, and is preferably represented by any one of the following formulas (10) to (17): In the formula (7), each s represents 0 or 1.

[0035] [ka]

[0036] In the formulas (10) to (17), R 7 and R 8 each independently represents one member selected from the group consisting of a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, an alkoxy group having from 1 to 4 carbon atoms or a phenyl group substituted with an alkoxy group having from 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having from 7 to 10 carbon atoms, and a halogen atom; W represents a divalent group; q and r each independently represent an integer of 1 to 10, and each independently represent an integer of 0 to 3.

[0037] W in the formulas (16) to (17) is preferably any one of the divalent groups represented by the following formulas (18) to (26), where u in formula (25) represents an integer of 0 to 3.

[0038] [ka]

[0039] In addition, in formula (A), Ar 5 When k is 0, it is a substituted or unsubstituted aryl group, and the aryl group is Ar 1 ~Ar 4 The aryl groups are the same as those exemplified in the description of Ar 5 When k is 1, it is a substituted or unsubstituted arylene group, and the arylene group is Ar 1 ~Ar 4 From the aryl groups exemplified in the description of -N(Ar 3 -(D) C3 )(Ar4 -(D) C4 ) is an arylene group in which one hydrogen atom is removed from the position where it is substituted.

[0040] The content of the reactive charge transport material is preferably 30% by mass or more and 100% by mass or less, more preferably 40% by mass or more and 100% by mass or less, and even more preferably 50% by mass or more and 100% by mass or less, based on the composition (solid content) used to form the surface protective layer. By setting it in this range, the electrical properties of the cured film are excellent, and the cured film can be made thick.

[0041] Examples of non-reactive charge transport materials include electron transport compounds such as p-benzoquinone, chloranil, bromanil, anthraquinone, and the like; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds. Examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. The non-reactive charge transport materials may be used alone or in combination of two or more. Among these, triarylamine compounds are preferred as non-reactive charge transport materials from the viewpoints of wear suppression and image flow suppression.

[0042] From the viewpoints of abrasion suppression and image flow suppression, the surface protective layer is preferably a cured film of a composition containing a compound having a hydroxy group, and a compound having no hydroxy group and a benzene ring structure, and more preferably a cured film of a composition containing a compound having a hydroxy group and a benzene ring structure, and a compound having no hydroxy group and a benzene ring structure.

[0043] From the viewpoints of abrasion suppression and image flow suppression, the compound having a hydroxy group is preferably a reactive charge transport material having a reactive group and a charge transport skeleton, and more preferably a reactive charge transport material having a hydroxy group and a charge transport skeleton. From the viewpoints of charge transportability, wear suppression, and image flow suppression, the compound having a hydroxy group is preferably a compound having a triarylamine structure.

[0044] From the viewpoints of abrasion suppression and image flow suppression, the compound having no hydroxy group and a benzene ring structure is preferably a reactive charge transport material having a reactive group and a charge transport skeleton, and more preferably a reactive charge transport material having an alkoxy group and a charge transport skeleton. The compound having no hydroxy group and a benzene ring structure is preferably a compound having a triarylamine structure from the viewpoints of charge transportability, wear suppression, and image flow suppression.

[0045] The mass ratio MH / MB of the content MH of the compound having a hydroxy group to the content MB of the compound having no hydroxy group and having a benzene ring structure in the composition that forms the cured film is, from the viewpoints of abrasion suppression and image flow suppression, preferably from 2 to 30, more preferably from 3 to 25, even more preferably from 5 to 20, and particularly preferably from 5 to 10.

[0046] From the viewpoints of suppressing abrasion and improving image deletion suppression by reducing moisture absorption, it is preferable that the surface protective layer does not have a carboxy group. From the viewpoints of improving the abrasion suppression property and the image flow suppression property by reducing the moisture absorption property, the surface protective layer preferably does not contain silicon atoms, and more preferably does not contain carboxy groups and silicon atoms.

[0047] Examples of the reactive non-charge transporting material include a thermosetting resin, a curing agent, etc. The reactive group-containing non-charge transporting material may be used alone or in combination of two or more kinds. Examples of the thermosetting resin include guanamine resin, melamine resin, phenol resin, urea resin, and alkyd resin. Examples of the curing agent include a compound having a guanamine structure (hereinafter also referred to as a "guanamine compound") and a compound having a melamine structure (hereinafter also referred to as a "melamine compound"). When the surface protective layer is a cured film comprising, for example, a crosslinked product (crosslinked product) of a reactive charge transport material and at least one selected from the group consisting of a thermosetting resin (more preferably a guanamine resin, a melamine resin, etc.), a guanamine compound, and a melamine compound, a cured film with a high degree of curing is easily obtained and has excellent abrasion suppression properties, compared to a case in which a thermosetting resin (more preferably a guanamine resin, a melamine resin, etc.), a guanamine compound, and a melamine compound are not included.

[0048] The surface protective layer may further contain fluororesin particles. When the surface protective layer further contains fluororesin particles, appropriate irregularities are formed on the outer peripheral surface of the surface protective layer, resulting in better wear suppression properties. The surface protective layer contains fluororesin particles in an amount of 5% by mass or more and 15% by mass or less based on the total solid content of the surface protective layer. The content of the fluororesin particles is preferably from 5% by mass to 15% by mass, and more preferably from 7% by mass to 12% by mass, based on the total constituent components of the layer (total solid content).

[0049] The fluororesin particles are not particularly limited, but examples include particles of polytetrafluoroethylene (PTFE, also known as "tetrafluoroethylene resin"), perfluoroalkoxy fluororesin, polychlorotrifluoroethylene, polyvinylidene fluoride, polydichlorodifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, and the like.

[0050] Among these, polytetrafluoroethylene and copolymers of tetrafluoroethylene and perfluoroalkoxyethylene are preferred from the viewpoints of wear suppression and cleaning properties of the electrophotographic photoreceptor. The fluororesin particles may be used alone or in combination of two or more kinds.

[0051] The weight average molecular weight of the fluororesin constituting the fluororesin particles is preferably, for example, 3,000 or more and 5,000,000 or less.

[0052] The average primary particle size of the fluororesin particles is, for example, preferably 0.05 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 5 μm or less. The average primary particle size of the fluororesin particles refers to the value measured using a laser diffraction / scattering type particle size distribution analyzer LA-920 (manufactured by Horiba, Ltd.) at a refractive index of 1.35 on a measurement liquid diluted with the same solvent as the dispersion liquid in which the fluororesin particles are dispersed.

[0053] Examples of commercially available fluororesin particles include the Lubron (registered trademark) series (manufactured by Daikin Industries, Ltd.), the Teflon (registered trademark) series (manufactured by DuPont), and the Dyneon series (manufactured by 3M Japan Ltd.).

[0054] -Method for forming surface protective layer- The formation of the surface protection layer is not particularly limited, and a well-known formation method can be used. For example, it is preferable to form a coating film of a coating liquid for forming the surface protection layer (= the composition) in which the above components are added to a solvent, dry the coating film, and, if necessary, subject it to a curing treatment such as heating. From the viewpoints of coating strength, abrasion suppression, and image flow suppression, the drying temperature when drying the coating film is preferably 150° C. or higher, more preferably 150° C. or higher and 200° C. or lower, even more preferably 150° C. or higher and 180° C. or lower, and particularly preferably 155° C. or higher and lower than 170° C. The drying time when drying the coating film is related to the drying temperature, but from the viewpoints of coating film strength, abrasion suppression, and image flow suppression, it is preferably 10 minutes or more, more preferably 20 minutes or more, even more preferably 20 minutes or more and 120 minutes or less, and particularly preferably 20 minutes or more and 60 minutes or less.

[0055] Examples of solvents for preparing a coating liquid for forming a surface protective layer include aromatic solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, ether solvents such as tetrahydrofuran and dioxane, cellosolve solvents such as ethylene glycol monomethyl ether, and alcohol solvents such as isopropyl alcohol and butanol. These solvents may be used alone or in combination of two or more. The content of the solvent is preferably 30% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and particularly preferably 60% by mass or more and 80% by mass or less, based on the total mass of the coating liquid for forming the surface protective layer.

[0056] Examples of a method for applying the coating liquid for forming a surface protective layer onto a photosensitive layer (e.g., a charge transport layer) include conventional methods such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating.

[0057] -Film thickness- The thickness of the surface protective layer is set, for example, preferably in the range of 1 μm or more and 20 μm or less, and more preferably in the range of 2 μm or more and 10 μm or less.

[0058] <Conductive substrate> Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Examples of conductive substrates include paper, resin films, belts, etc., coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys. Here, "conductive" refers to a material having a volume resistivity of 10 13 This means that the resistance is less than Ωcm.

[0059] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center line average roughness Ra of 0.04 μm to 0.5 μm in order to suppress interference fringes that occur when irradiating with laser light. When non-interfering light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for extending the life of the conductive substrate since it suppresses the occurrence of defects due to unevenness on the surface.

[0060] Examples of methods for roughening the surface include wet honing, which involves spraying an abrasive suspended in water onto the conductive substrate; centerless grinding, in which the conductive substrate is pressed against a rotating grindstone and continuously ground; and anodizing.

[0061] As a method for roughening the surface, there can be mentioned a method in which, without roughening the surface of the conductive substrate, a conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the surface is roughened by the particles dispersed in the layer.

[0062] In the roughening treatment by anodization, an oxide film is formed on the surface of a conductive substrate by anodizing the conductive substrate made of metal (e.g., aluminum) in an electrolyte solution using the conductive substrate as the anode. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodization is chemically active in its original state, easily contaminated, and has a large resistance variation depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film, in which the micropores of the oxide film are filled by volume expansion caused by hydration reaction in pressurized steam or boiling water (metal salts such as nickel may be added) to change the film into a more stable hydrated oxide.

[0063] The thickness of the anodic oxide film is preferably, for example, from 0.3 μm to 15 μm. If the thickness is within this range, the film tends to exhibit a barrier property against injection and tends to suppress an increase in residual potential due to repeated use.

[0064] The conductive substrate may be subjected to a treatment with an acidic treatment solution or a boehmite treatment. Treatment with an acid treatment liquid is carried out, for example, as follows. First, an acid treatment liquid containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The compounding ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acid treatment liquid are, for example, in the range of 10% by mass to 11% by mass for phosphoric acid, 3% by mass to 5% by mass for chromic acid, and 0.5% by mass to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% by mass to 18% by mass. The treatment temperature is preferably, for example, 42° C. to 48° C. The film thickness of the coating is preferably 0.3 μm to 15 μm.

[0065] The boehmite treatment is carried out, for example, by immersing the plate in pure water at 90° C. to 100° C. for 5 to 60 minutes, or by contacting the plate with heated steam at 90° C. to 120° C. for 5 to 60 minutes. The thickness of the coating is preferably 0.1 μm to 5 μm. This may be further anodized using an electrolyte solution having low coating solubility, such as adipic acid, boric acid, borates, phosphates, phthalates, maleates, benzoates, tartrates, or citrates.

[0066] <Sublayer> The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0067] As inorganic particles, for example, powder resistivity (volume resistivity) of 10 2 Ωcm or more 10 11 Examples of such particles include inorganic particles with a particle size of Ωcm or less. Among these, examples of inorganic particles having the above-mentioned resistance value include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, and zinc oxide particles are particularly preferred.

[0068] The specific surface area of ​​inorganic particles by the BET method is, for example, 10 m 2 / g or higher is preferable. The volume average particle size of the inorganic particles is, for example, 50 nm or more and 2,000 nm or less (preferably 60 nm or more and 1,000 nm or less).

[0069] The content of the inorganic particles is, for example, preferably from 10% by mass to 80% by mass, more preferably from 40% by mass to 80% by mass, based on the binder resin.

[0070] The inorganic particles may be surface-treated. Two or more types of inorganic particles having different surface treatments or different particle sizes may be used in combination.

[0071] Examples of the surface treatment agent include a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, etc. In particular, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

[0072] Examples of silane coupling agents having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0073] Silane coupling agents may be used in combination of two or more kinds. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0074] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

[0075] The amount of the surface treatment agent to be used is preferably, for example, 0.5% by mass or more and 10% by mass or less based on the inorganic particles.

[0076] Here, it is preferable that the undercoat layer contains an electron accepting compound (acceptor compound) together with the inorganic particles, from the viewpoints of improving the long-term stability of electrical properties and carrier blocking properties.

[0077] Examples of the electron-accepting compound include electron-transporting substances such as quinone compounds such as chloranil and bromoanil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; and diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone. In particular, the electron-accepting compound is preferably a compound having an anthraquinone structure. Examples of the compound having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds. Specifically, for example, anthraquinone, alizarin, quinizarin, anthraphin, purpurin, etc. are preferred.

[0078] The electron accepting compound may be contained in the undercoat layer in a dispersed state together with the inorganic particles, or may be contained in a state of being attached to the surfaces of the inorganic particles.

[0079] The method for attaching the electron accepting compound to the surface of the inorganic particles may be, for example, a dry method or a wet method.

[0080] The dry method is, for example, a method in which an electron-accepting compound is attached to the surface of inorganic particles by dropping an electron-accepting compound directly or dissolved in an organic solvent or spraying it together with dry air or nitrogen gas while stirring inorganic particles with a mixer or the like that exerts a large shearing force. The dropping or spraying of the electron-accepting compound is preferably performed at a temperature below the boiling point of the solvent. After dropping or spraying the electron-accepting compound, baking may be performed at 100° C. or higher. The temperature and time of baking are not particularly limited as long as electrophotographic properties can be obtained.

[0081] The wet method is a method in which, for example, an electron-accepting compound is added while dispersing inorganic particles in a solvent by stirring, ultrasonic waves, a sand mill, an attritor, a ball mill, etc., and the inorganic particles are stirred or dispersed, and then the solvent is removed to attach the electron-accepting compound to the surface of the inorganic particles. The solvent is removed, for example, by filtration or distillation. After the solvent is removed, baking may be performed at 100°C or higher. The baking temperature and time are not particularly limited as long as electrophotographic properties are obtained. In the wet method, moisture contained in the inorganic particles may be removed before adding the electron-accepting compound, and examples of such methods include a method of removing the moisture while stirring and heating in a solvent, and a method of removing the moisture by azeotropy with the solvent.

[0082] The attachment of the electron accepting compound may be carried out before or after the inorganic particles are subjected to a surface treatment with a surface treatment agent, or the attachment of the electron accepting compound and the surface treatment with the surface treatment agent may be carried out simultaneously.

[0083] The content of the electron accepting compound is, for example, from 0.01% by mass to 20% by mass, and preferably from 0.01% by mass to 10% by mass, based on the inorganic particles.

[0084] Examples of the binder resin used in the undercoat layer include known materials such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; and silane coupling agents. Examples of the binder resin used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline, etc.), and the like.

[0085] Among these, the binder resin used in the undercoat layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and in particular, a resin obtained by reacting at least one resin selected from the group consisting of thermosetting resins such as urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins with a curing agent is preferred. When two or more of these binder resins are used in combination, the mixing ratio is set as necessary.

[0086] The undercoat layer may contain various additives for improving electrical properties, environmental stability, and image quality. Examples of the additives include known materials such as polycyclic condensation and azo-based electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, silane coupling agents, etc. As described above, silane coupling agents are used for surface treatment of inorganic particles, and may also be added to the undercoat layer as an additive.

[0087] Examples of silane coupling agents as additives include vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, and the like.

[0088] Examples of the zirconium chelate compound include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0089] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0090] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0091] These additives may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0092] The undercoat layer preferably has a Vickers hardness of 35 or more. The surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to between 1 / (4n) (n is the refractive index of the upper layer) and 1 / 2 of the wavelength λ of the exposure laser used in order to suppress moire images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of the resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. The surface of the undercoat layer may be polished to adjust the surface roughness. Examples of the polishing method include buffing, sandblasting, wet honing, grinding, and the like.

[0093] The formation of the undercoat layer is not particularly limited, and a well-known formation method can be used. For example, the undercoat layer can be formed by forming a coating film of a coating solution for forming the undercoat layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary.

[0094] Examples of the solvent for preparing the coating liquid for forming the undercoat layer include known organic solvents, such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include ordinary organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0095] Examples of the method for dispersing the inorganic particles when preparing the coating liquid for forming the undercoat layer include known methods such as those using a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0096] Examples of the method for applying the coating liquid for forming the undercoat layer onto the conductive substrate include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0097] The thickness of the undercoat layer is set, for example, preferably at least 15 μm, and more preferably within the range of from 20 μm to 50 μm.

[0098] <Middle Class> Although not shown, an intermediate layer may be further provided between the undercoat layer and the charge generating layer. The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include polymer compounds such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, and melamine resins. The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used in the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in the intermediate layer may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0099] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0100] The formation of the intermediate layer is not particularly limited, and a well-known formation method can be used. For example, the intermediate layer can be formed by forming a coating film of a coating liquid for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it if necessary. The coating method for forming the intermediate layer includes dip coating, push-up coating, and wire bar coating. Conventional coating methods such as spray coating, blade coating, knife coating, curtain coating, etc. may be used.

[0101] The thickness of the intermediate layer is preferably set in the range of, for example, 0.1 μm to 3 μm. The intermediate layer may also be used as an undercoat layer.

[0102] <Charge generation layer> The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. The charge generation layer may also be a vapor deposition layer of the charge generation material. The vapor deposition layer of the charge generation material is suitable for use with a non-coherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array.

[0103] Examples of the charge generating material include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0104] Among these, in order to accommodate laser exposure in the near infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material, specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, or titanyl phthalocyanine.

[0105] On the other hand, in order to accommodate laser exposure in the near ultraviolet region, preferred charge generating materials include condensed aromatic pigments such as dibromoanthanthrone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and bisazo pigments.

[0106] The above charge generating materials may be used when using incoherent light sources such as LEDs and organic EL image arrays that emit light at a central wavelength of 450 nm to 780 nm, but from the viewpoint of resolution, when using a thin photosensitive layer of 20 μm or less, the electric field strength in the photosensitive layer becomes high, and a decrease in charging due to charge injection from the substrate, so-called black spots, is likely to occur as an image defect. This becomes more noticeable when using charge generating materials that are p-type semiconductors such as trigonal selenium and phthalocyanine pigments and are prone to generating dark current.

[0107] In contrast, when an n-type semiconductor such as a fused aromatic pigment, a perylene pigment, or an azo pigment is used as the charge generating material, dark current is unlikely to occur, and image defects called black spots can be suppressed even when the material is made into a thin film. The n-type is determined by the polarity of the photocurrent that flows using the commonly used time-of-flight method, and those that easily pass electrons as carriers rather than holes are considered to be n-type.

[0108] The binder resin used in the charge generating layer may be selected from a wide range of insulating resins, and may also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, polysilane, and the like. Examples of the binder resin include polyvinyl butyral resin, polyarylate resin (polycondensation product of bisphenols and aromatic dicarboxylic acid, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinylpyrrolidone resin, etc. Here, "insulating" means a material having a volume resistivity of 10 13 This means that the resistance is Ωcm or more. These binder resins may be used alone or in combination of two or more.

[0109] The compounding ratio of the charge generating material to the binder resin is preferably within a range of 10:1 to 1:10 by mass.

[0110] The charge generating layer may contain other well-known additives.

[0111] The formation of the charge generation layer is not particularly limited, and a known formation method is used, for example, by forming a coating film of a coating solution for forming a charge generation layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary. The formation of the charge generation layer may be performed by vapor deposition of a charge generation material. The formation of the charge generation layer by vapor deposition is particularly suitable when a condensed ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0112] Examples of the solvent for preparing the coating liquid for forming the charge generating layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene, etc. These solvents may be used alone or in combination of two or more.

[0113] Examples of methods for dispersing particles (e.g., charge generating material) in the coating liquid for forming a charge generating layer include media dispersers such as ball mills, vibration ball mills, attritors, sand mills, and horizontal sand mills, and medialess dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion liquid is dispersed by penetrating a fine flow path under high pressure. During this dispersion, it is effective to adjust the average particle size of the charge generating material in the coating liquid for forming the charge generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0114] Examples of a method for applying the coating liquid for forming the charge generating layer onto the undercoat layer (or onto the intermediate layer) include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0115] The thickness of the charge generating layer is set, for example, preferably in the range of 0.1 μm or more and 5.0 μm or less, and more preferably in the range of 0.2 μm or more and 2.0 μm or less.

[0116] <Charge transport layer> The charge transport layer is, for example, a layer containing a charge transport material and a binder resin, and may be a layer containing a polymer charge transport material.

[0117] Examples of the charge transport material include electron transporting compounds such as quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds. Examples of the charge transport material include hole transporting compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination, but are not limited to these.

[0118] As the charge transport material, from the viewpoint of charge mobility, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2) are preferable.

[0119] [ka]

[0120] In structural formula (a-1), Ar T1 , Ar T2 , and Ar T3 each independently represents a substituted or unsubstituted aryl group, -CH-C(R T4 )=C(R T5 )(R T6 ), or -CH-CH=CH-CH=C(R T7 )(R T8 ) is shown. T4 , R T5 , R T6 , R T7 , and R T8 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Examples of the substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0121] [ka]

[0122] In structural formula (a-2), R T91 and R T92 R each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. T101 , R T102 , R T111 and R T112 each independently represents a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, an amino group substituted with an alkyl group having from 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ) and R T12 , R T13 , R T14 , R T15 and R T16 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, ​​Tn1, and Tn2 each independently represent an integer of 0 or more and 2 or less. Examples of the substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0123] Among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), in particular, "-C6H4-CH=CH-CH=C(RT7 )(R T8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 ) is preferable from the viewpoint of charge mobility.

[0124] As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane are used. In particular, polyester polymer charge transport materials are particularly preferred. The polymer charge transport material may be used alone or in combination with a binder resin.

[0125] Examples of the binder resin used in the charge transport layer include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polysilane, etc. Among these, polycarbonate resin or polyarylate resin is suitable as the binder resin. These binder resins are used alone or in combination of two or more. The compounding ratio of the charge transport material to the binder resin is preferably from 10:1 to 1:5 by mass.

[0126] The charge transport layer may contain other well-known additives.

[0127] The formation of the charge transport layer is not particularly limited, and a known formation method can be used. For example, the charge transport layer can be formed by forming a coating film of a coating liquid for forming the charge transport layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0128] Examples of solvents for preparing the coating liquid for forming the charge transport layer include ordinary organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene, ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride, and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents may be used alone or in combination of two or more.

[0129] Examples of a coating method for coating the coating liquid for forming the charge transport layer on the charge generating layer include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating and curtain coating.

[0130] The thickness of the charge transport layer is set, for example, preferably in the range of 5 μm or more and 50 μm or less, and more preferably in the range of 10 μm or more and 30 μm or less.

[0131] (Image forming apparatus (and process cartridge)) The image forming apparatus according to the present embodiment includes an electrophotographic photoreceptor, a charging device that contact-charges the surface of the electrophotographic photoreceptor with a DC voltage, an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing toner to form a toner image, and a transfer device that transfers the toner image to the surface of a recording medium. The electrophotographic photoreceptor for contact charging with a DC voltage according to the present embodiment is applied as the electrophotographic photoreceptor.

[0132] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as an apparatus provided with a fixing means for fixing a toner image transferred onto the surface of a recording medium; an apparatus of a direct transfer type for directly transferring a toner image formed on the surface of an electrophotographic photosensitive member onto a recording medium; an apparatus of an intermediate transfer type for primarily transferring a toner image formed on the surface of an electrophotographic photosensitive member onto the surface of an intermediate transfer member, and then secondarily transferring the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium; an apparatus provided with a cleaning means for cleaning the surface of an electrophotographic photosensitive member before charging after the transfer of a toner image; an apparatus provided with a discharging means for irradiating the surface of an electrophotographic photosensitive member with discharging light to discharge the surface before charging after the transfer of a toner image; and an apparatus provided with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

[0133] In the case of an intermediate transfer type device, the transfer means has, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer means which primarily transfers the toner image formed on the surface of the electrophotographic photosensitive body onto the surface of the intermediate transfer body, and a secondary transfer means which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

[0134] The image forming apparatus according to the present embodiment may be either a dry development type image forming apparatus or a wet development type image forming apparatus (a development type using a liquid developer).

[0135] In the image forming apparatus according to the present embodiment, for example, a portion including an electrophotographic photosensitive member may be detachably attached to the image forming apparatus and may have a cartridge structure (process cartridge) for contact-charging the electrophotographic photosensitive member with a DC voltage. As the process cartridge, for example, a process cartridge including an electrophotographic photosensitive member for contact charging with a DC voltage according to the present embodiment is preferably used. In addition to the electrophotographic photosensitive member, the process cartridge may include at least one selected from the group consisting of a charging means, an electrostatic latent image forming means, a developing means, and a transfer means.

[0136] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. Note that only the main parts shown in the drawings will be described, and descriptions of the rest will be omitted.

[0137] FIG. 2 is a schematic diagram showing an example of the image forming apparatus according to the present embodiment. As shown in FIG. 2, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming means), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 via the intermediate transfer body 50, and the intermediate transfer body 50 is disposed with a part of it in contact with the electrophotographic photoreceptor 7. Although not shown, the image forming apparatus 100 also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown) correspond to an example of a transfer means.

[0138] 2 supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging means), a developing device 11 (an example of a developing means), and a cleaning device 13 (an example of a cleaning means) integrally within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is disposed so as to come into contact with the surface of the electrophotographic photoreceptor 7. The cleaning member may not be in the form of the cleaning blade 131, but may be a conductive or insulating fibrous member, which may be used alone or in combination with the cleaning blade 131.

[0139] FIG. 2 shows an example of an image forming apparatus equipped with a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists in cleaning, which may be arranged as needed.

[0140] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0141] -Charging device- As the charging device 8, for example, a contact type charger using a conductive or semiconductive charging roller, charging brush, charging film, charging rubber blade, charging tube, or the like is used.

[0142] -Exposure equipment- The exposure device 9 may be, for example, an optical device that exposes the surface of the electrophotographic photoreceptor 7 with light such as semiconductor laser light, LED light, or liquid crystal shutter light in a predetermined image. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photoreceptor. The wavelength of the semiconductor laser is mainly near infrared light having an oscillation wavelength of about 780 nm. However, it is not limited to this wavelength, and a laser having an oscillation wavelength of 600 nm or a blue laser having an oscillation wavelength of 400 nm to 450 nm may also be used. In addition, a surface-emitting laser light source capable of outputting multiple beams is also effective for forming a color image.

[0143] -Developing device- The developing device 11 may be, for example, a general developing device that develops by contacting or non-contacting a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected according to the purpose. For example, it may be a known developing device that has a function of attaching a one-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, roller, or the like. Among them, it is preferable to use a developing roller that holds a developer on its surface.

[0144] The developer used in the developing device 11 may be a one-component developer containing only toner, or may be a two-component developer containing toner and a carrier. The developer may be magnetic or non-magnetic. Well-known developers are used.

[0145] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131 . In addition to the cleaning blade system, a fur brush cleaning system or a simultaneous development and cleaning system may also be used.

[0146] -Transfer device- Examples of the transfer device 40 include a contact type transfer charger using a belt, roller, film, rubber blade, etc., and a scorotron transfer charger or corotron transfer charger that utilizes corona discharge.

[0147] -Intermediate transfer body- A belt-like intermediate transfer belt containing semiconductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. is used as the intermediate transfer body 50. The intermediate transfer body may be in the form of a drum other than a belt.

[0148] FIG. 3 is a schematic diagram showing another example of the image forming apparatus according to the present embodiment. 3 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one electrophotographic photosensitive body is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem type. EXAMPLES

[0149] The electrophotographic photoreceptor according to the present embodiment will be described in more detail below with reference to examples. The materials, amounts, ratios, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present embodiment. Therefore, the scope of the electrophotographic photoreceptor according to the present embodiment should not be interpreted as being limited by the specific examples shown below.

[0150] (Examples 1 to 8 and Comparative Examples 1 to 6) <Preparation of photoreceptor> [Preparation of Photoreceptor] - Preparation of undercoat layer - Zinc oxide: (average particle size 70 nm: manufactured by Teika Co., Ltd.: specific surface area value 15 m 2 100 parts by mass of zinc oxide (100 parts by mass of 1 / g) was stirred and mixed with 500 parts by mass of toluene, and 1.3 parts by mass of a silane coupling agent (KBM503: manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto, followed by stirring for 2 hours. Thereafter, the toluene was distilled off under reduced pressure, and the resulting mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with a silane coupling agent. 110 parts by mass of zinc oxide that had been subjected to surface treatment was stirred and mixed with 500 parts by mass of tetrahydrofuran, and a solution in which 0.6 parts by mass of alizarin was dissolved in 50 parts by mass of tetrahydrofuran was added, followed by stirring for 5 hours at 50° C. Thereafter, the zinc oxide to which alizarin had been added was filtered off by filtration under reduced pressure, and further dried under reduced pressure at 60° C. to obtain zinc oxide to which alizarin had been added.

[0151] 60 parts by mass of this alizarin-added zinc oxide, 13.5 parts by mass of a curing agent (blocked isocyanate, Sumidur 3175, manufactured by Sumitomo Bayern Urethane Co., Ltd.), and 15 parts by mass of a butyral resin (S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) were dissolved in 85 parts by mass of methyl ethyl ketone, and 38 parts by mass of a solution of this was mixed with 25 parts by mass of methyl ethyl ketone, and the mixture was dispersed in a sand mill using 1 mmφ glass beads for 2 hours to obtain a dispersion. To the resulting dispersion, 0.005 parts by mass of dioctyltin dilaurate as a catalyst and 40 parts by mass of silicone resin particles (Tospearl 145, manufactured by GE Toshiba Silicones Co., Ltd.) were added to obtain a coating liquid for forming an undercoat layer.

[0152] A cylindrical aluminum substrate having a diameter of 30 mm, a length of 340 mm, and a thickness of 1 mm was prepared as a conductive substrate. The obtained coating liquid for forming an undercoat layer was applied onto the cylindrical aluminum substrate by a dip coating method, and the coating liquid was dried and cured at 170°C for 40 minutes to obtain an undercoat layer having a thickness of 18.7 μm.

[0153] -Creating the charge generating layer- A mixture of 15 parts by mass of hydroxygallium phthalocyanine as a charge generating material having diffraction peaks at Bragg angles (2θ±0.2°) at least 7.3°, 16.0°, 24.9°, and 28.0° in an X-ray diffraction spectrum using Cukα characteristic X-rays, 10 parts by mass of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nippon Unicar Co., Ltd.) as a binder resin, and 200 parts by mass of n-butyl acetate was dispersed in a sand mill using glass beads with a diameter of 1 mm for 4 hours. 175 parts by mass of n-butyl acetate and 180 parts by mass of methyl ethyl ketone were added to the obtained dispersion and stirred to obtain a coating liquid for forming a charge generating layer. The obtained coating liquid for forming a charge generating layer was dip-coated on the undercoat layer previously formed on the cylindrical aluminum substrate, and dried at room temperature (25° C.) to form a charge generating layer having a thickness of 0.2 μm.

[0154] -Creating the charge transport layer- First, a polycarbonate copolymer (1) was obtained as follows. In a flask equipped with a phosgene inlet tube, a thermometer, and a stirrer, 106.9 g (0.398 mol) of 1,1-bis(4-hydroxyphenyl)cyclohexane (hereinafter referred to as "Z"), 24.7 g (0.133 mol) of 4,4'-dihydroxybiphenyl (hereinafter referred to as "BP"), 0.41 g of hydrosulfite, 825 ml of 9.1% aqueous sodium hydroxide solution (2.018 mol of sodium hydroxide), and 500 ml of methylene chloride were charged and dissolved under a nitrogen atmosphere, and while maintaining the temperature in the range of 18°C ​​to 21°C with stirring, 76.2 g (0.770 mol) of phosgene was blown in over 75 minutes to carry out a phosgenation reaction. After the phosgenation reaction was completed, 1.11 g (0.0075 mol) of p-tert-butylphenol and 54 ml of 25% aqueous sodium hydroxide solution (0.266 mol of sodium hydroxide) were added and stirred, and 0.18 mL (0.0013 mol) of triethylamine was added during the reaction, and the mixture was reacted at a temperature of 30°C to 35°C for 2.5 hours. The separated methylene chloride phase was washed with acid and with water until inorganic salts and amines were eliminated, and then the methylene chloride was removed to obtain polycarbonate copolymer (1). The molar ratio of Z to BP units in this polycarbonate was 75:25.

[0155] Next, 25 parts by mass of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1']biphenyl-4,4'-diamine (TPD), 20 parts by mass of the compound represented by structural formula (A), and 55 parts by mass of polycarbonate copolymer (1) (viscosity average molecular weight: 50,000) as a binder resin were dissolved in 560 parts by mass of tetrahydrofuran and 240 parts by mass of toluene to obtain a coating liquid for a charge transport layer. This coating liquid was applied onto the charge generation layer and dried at 135°C for 45 minutes to form a charge transport layer with a thickness of 20 μm.

[0156] [ka]

[0157] -Creating a protective layer- As a reactive charge transport material and a compound having a hydroxyl, the compound shown in Table 1 was used in the amount shown in Table 1, as a compound having no hydroxyl and a benzene ring, the compound shown in Table 1 was used in the amount shown in Table 1, and 4.4 parts by mass of a curable resin containing a reactive group: benzoguanamine resin (Nikarac BL-60, manufactured by Sanwa Chemical Co., Ltd.) was added to 220 parts by mass of a solvent shown in Table 1, mixed and dissolved, and then 0.1 parts by mass of NACURE5225 (manufactured by King Industry Co., Ltd.) was added as a curing catalyst to obtain a coating liquid for forming a surface protective layer. This surface protective layer forming coating liquid was dip-coated on the charge transport layer, and air-dried at room temperature (25°C) for 30 minutes, and then heated under a nitrogen stream with an oxygen concentration of 110 ppm from room temperature to the drying temperature (achieved temperature) shown in Table 1, and held for the drying time (holding time) shown in Table 1 to perform heat treatment and hardening. Thus, a surface protective layer with a film thickness of 10 µm was formed. In this manner, each electrophotographic photoreceptor was obtained.

[0158] <Image streaming suppression evaluation> As an image forming device, a DocuCentre VC2263 manufactured by Fujifilm Business Innovation, containing an electrostatic image developer, was prepared, the electrophotographic photoreceptor prepared was set, 100,000 sheets of A4 paper were passed through, and the device was left at high temperature and high humidity (28°C, 85% RH) for more than 12 hours. After leaving it, 10 halftone images (image density 30%) were printed, and image flow (toner whiteout) was evaluated. The evaluation criteria are as follows. A: No image distortion at all B: No image flow that is problematic in terms of image quality C: Image quality is affected by image streaking.

[0159] <Wear Inhibition Evaluation> The film thickness of the prepared electrophotographic photoreceptor was measured with an eddy current film thickness meter before and after passing 100,000 sheets of A4 paper in the image flow suppression evaluation, and the average film thickness difference before and after passing the paper was divided by the running distance to calculate the average wear rate. The smaller the average wear rate (nm / kcyc, wear amount per 1000 sheets of A4 paper), the better the wear suppression. The average wear rate is preferably less than 4.0 nm / kcyc, and more preferably less than 3.0 nm / kcyc.

[0160] The details of each example and the evaluation results are shown in Table 1 below.

[0161] [Table 1]

[0162] Details of the abbreviations listed in Table 1 are given below. H-1: The following compound H-2: The following compound H-3: The following compound

[0163] [ka]

[0164] B-1: The following compound

[0165] [ka]

[0166] As shown in Table 1, the electrophotographic photoreceptors of Examples are superior in both wear suppression and image flow suppression, as compared with the electrophotographic photoreceptors of Comparative Examples.

[0167] (((1))) An electrophotographic photoreceptor for contact charging by DC voltage, comprising: a conductive substrate; an undercoat layer provided on the conductive substrate; a charge generating layer provided on the undercoat layer; a charge transport layer provided on the charge generating layer; and a surface protective layer provided on the charge transport layer, wherein the surface protective layer is a cured film of a composition containing a reactive charge transport material, has a hydroxy group and a benzene ring structure, and has a value of hydroxy group peak area / benzene ring structure peak area of ​​more than 0.05 and not more than 0.36 in total reflection measurement method of infrared spectroscopy. (((2))) The electrophotographic photoreceptor for contact charging by DC voltage according to (((1))), wherein the surface protective layer is a cured film of a composition containing a compound having a hydroxy group and a compound having no hydroxy group and a benzene ring structure. (((3))) The electrophotographic photoreceptor for contact charging by DC voltage according to (((2))), wherein the compound having a hydroxy group is the reactive charge transport material. (((4))) The electrophotographic photoreceptor for contact charging by DC voltage according to (((2))) or (((3))), wherein the compound having a hydroxy group is a compound having a triarylamine structure. (((5))) The electrophotographic photoreceptor for contact charging by DC voltage according to any one of (((2))) to (((4))), wherein the compound having no hydroxy group and a benzene ring structure is a compound having a triarylamine structure. (((6))) The electrophotographic photoreceptor for contact charging by DC voltage according to any one of (((2))) to (((5))), wherein the mass ratio MH / MB of the content MH of compounds having a hydroxy group in the composition to the content MB of compounds having no hydroxy group and having a benzene ring structure in the composition is 5 or more and 20 or less. (((7))) The electrophotographic photoreceptor for contact charging by DC voltage according to any one of (((1))) to (((6))), wherein the surface protective layer does not have a carboxy group. (((8))) The electrophotographic photoreceptor for contact charging by DC voltage according to any one of (((1))) to (((7))), wherein the surface protective layer does not contain silicon atoms. (((9))) A process cartridge comprising an electrophotographic photosensitive member for contact charging by DC voltage described in any one of (((1))) to (((8))), which is detachably attached to an image forming apparatus and contact-charges the electrophotographic photosensitive member by DC voltage. (((10))) An image forming apparatus comprising: an electrophotographic photosensitive member for contact charging by DC voltage described in any one of (((1))) to (((8))); a charging device which contact-charges a surface of the electrophotographic photosensitive member by DC voltage; an electrostatic latent image forming device which forms an electrostatic latent image on the charged surface of the electrophotographic photosensitive member; a developing device which develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image; and a transfer device which transfers the toner image onto the surface of a recording medium.

[0168] According to the invention related to (((1))) or (((2))), there is provided an electrophotographic photoreceptor for contact-charging by DC voltage, which has a conductive substrate, an undercoat layer, a charge generating layer, a charge transport layer, and a surface protective layer, wherein the surface protective layer is a cured film of a composition containing a reactive charge transport material, and which, when contact-charging by DC voltage, is performed, has excellent wear suppression and image flow suppression properties compared to when the value of the hydroxy group peak area / benzene ring structure peak area, as determined by total reflection measurement method in infrared spectroscopy, is 0.05 or less or exceeds 0.36. According to the invention related to (((3))), there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in wear suppression and image deletion suppression properties than when the reactive charge transport material is composed solely of a compound that does not have a hydroxy group and has a benzene ring structure. According to the invention related to (((4))), there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in wear suppression and image flow suppression properties than when the compound having a hydroxy group does not have a triarylamine structure but has a mono- or diarylamine structure. According to the invention related to (((5))), there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in wear suppression and image flow suppression properties than when the compound having no hydroxy group and a benzene ring structure is a compound having no triarylamine structure but a mono- or diarylamine structure. According to the invention related to (((6))), there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is superior in wear suppression and image flow suppression properties to those in which the mass ratio MH / MB of the content MH of the compound having a hydroxy group to the content MB of the compound having no hydroxy group and having a benzene ring structure in the composition is less than 5 or exceeds 20. According to the invention related to (((7))), there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in wear suppression and image deletion suppression properties than when the surface protective layer has a carboxy group. According to the invention related to (((8))), there is provided an electrophotographic photoreceptor for contact charging by DC voltage, which is more excellent in wear suppression and image deletion suppression properties than when the surface protective layer contains silicon atoms. According to the invention pertaining to (((9))) or (((10))), there is provided a process cartridge or image forming apparatus, in which an electrophotographic photoreceptor which is contact-charged by a DC voltage has a conductive substrate, an undercoat layer, a charge generating layer, a charge transport layer and a surface protective layer, the surface protective layer being a cured film of a composition containing a reactive charge transport material, and which is superior in wear suppression and image flow suppression properties compared to cases in which the value of the hydroxyl group peak area / benzene ring structure peak area in a total reflection measurement method in infrared spectroscopy is 0.05 or less or exceeds 0.36. [Explanation of symbols]

[0169] 1 undercoat layer, 2 charge generating layer, 3 charge transport layer, 4 conductive substrate, 5 surface protective layer, 7A, 7 electrophotographic photoreceptor, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 40 transfer device, 50 intermediate transfer body, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll-shaped), 133 fibrous member (flat brush-shaped), 300 process cartridge

Claims

1. A conductive substrate; an undercoat layer provided on the conductive substrate; a charge generating layer provided on the undercoat layer; a charge transport layer provided on the charge generating layer; a surface protective layer provided on the charge transport layer, the surface protective layer is a cured film of a composition containing a reactive charge transport material, has a hydroxy group and a benzene ring structure, and has a value of a peak area of ​​the hydroxy group / a peak area of ​​the benzene ring structure in a total reflection measurement method of infrared spectroscopy exceeding 0.05 and not exceeding 0.36; An electrophotographic photoreceptor for contact charging using DC voltage.

2. 2. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 1, wherein the surface protective layer is a cured film of a composition containing a compound having a hydroxyl group and a compound having no hydroxyl group and a benzene ring structure.

3. 3. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 2, wherein the compound having a hydroxy group is the reactive charge transport material.

4. 3. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 2, wherein the compound having a hydroxy group is a compound having a triarylamine structure.

5. 3. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 2, wherein the compound having no hydroxy group and a benzene ring structure is a compound having a triarylamine structure.

6. 3. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 2, wherein the mass ratio MH / MB of the content MH of the compound having a hydroxyl group in the composition to the content MB of the compound having no hydroxyl group and a benzene ring structure in the composition is 5 or more and 20 or less.

7. 2. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 1, wherein the surface protective layer does not have a carboxy group.

8. 2. The electrophotographic photoreceptor for contact charging by DC voltage according to claim 1, wherein the surface protective layer does not contain silicon atoms.

9. The electrophotographic photoreceptor for contact charging by DC voltage according to any one of claims 1 to 8 is provided, A process cartridge that is detachably attached to an image forming apparatus and contact-charges the electrophotographic photosensitive member with a DC voltage.

10. The electrophotographic photoreceptor for contact charging by DC voltage according to any one of claims 1 to 8, a charging device that contact-charges the surface of the electrophotographic photoreceptor by a DC voltage; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; a transfer device for transferring the toner image onto a surface of a recording medium; An image forming apparatus comprising:

Images