JP2009128544A - Electrophotographic photoreceptor, electrophotographic cartridge, image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive charge type electrophotographic photoreceptor having good compatibility with peripheral members thereof and good electric properties, to provided an electrophotographic photoreceptor cartridge and an image forming apparatus each using the photoreceptor, and to provided an image forming method. <P>SOLUTION: The positive charge type electrophotographic photoreceptor has a single layer type photosensitive layer containing at least a binder resin, a charge generating material, an electron transport material and a hole transport material, wherein the electron transport material is selected from compounds represented by formula (1), formula (2), etc. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member used for a copying machine, a printer, and the like, an electrophotographic photosensitive member cartridge and an image forming apparatus including the photosensitive member, and an image forming method.

  Electrophotographic technology is widely used in fields such as copiers and various printers because of its immediacy and high quality images. For the electrophotographic photoreceptor (hereinafter referred to as “photoreceptor” as appropriate) which is the core of the electrophotographic technology, an organic photoconductive material having advantages such as non-polluting, easy film formation and easy production was used. A photoconductor is used.

  In organic electrophotographic photoconductors, so-called function-separated photoconductors that share charge carrier generation and transfer functions with different compounds have much room for material selection and easy control of the photoconductor properties. Has become the mainstream of development. In addition, from the viewpoint of the layer configuration, a single-layer type photoreceptor having a charge generating agent and a charge transport agent in the same layer and a separate layer (charge generation layer and charge transport layer) are provided separately. There is known a laminate type photoreceptor formed by laminating these layers.

  Of these, the multilayer photoconductors are easy to measure the function of each layer from the viewpoint of designing the photoconductors, and the characteristics can be easily controlled, so that most of the current photoconductors are multilayer photoconductors. . Further, most of the laminated type photoreceptors have at least a charge generation layer and a charge transport layer in this order on a substrate.

  As the electron transporting material in the charge transporting layer, there are very few suitable materials, but many hole transporting materials are known with good characteristics. In the case where a multilayer photoreceptor is formed using a hole transport material, a negative charging method is employed. In the negative charging method, when the photosensitive member is charged by negative corona discharge, the generated ozone may adversely affect the environment and the photosensitive member characteristics.

  On the other hand, a single-layer positively charged photoreceptor is considered to have one advantage that such ozone generation is reduced, and in terms of electrical characteristics, it is inferior to a negatively charged laminated photoreceptor. Although many, some have been put to practical use. In addition, the single-layer type photoreceptor has advantages such as fewer application processes and less interference fringes with semiconductor laser light.

  Further, in a single-layer type photoreceptor, most of the incident light is absorbed near the surface of the photosensitive layer and charges are generated, so that the diffusion of irradiated light in the photosensitive layer can be almost ignored. Further, there is an advantage that the distance of charge movement until neutralization of the surface charge after charging is smaller than that of the multilayer type photoreceptor. For this reason, in a single-layer type photoreceptor, image blur due to diffusion of light and charge carriers hardly occurs, and high resolution can be expected. Further, even when the photosensitive layer is made thicker, the degree of diffusion of charge and incident light does not change so much and the resolution does not decrease much (Patent Documents 1 to 5).

  In addition to this, mechanical degradation such as abrasion of the photosensitive layer surface due to rubbing of the cleaning blade, magnetic brush, developer, contact with the transfer member or paper, scratches, film peeling, etc. is there. In particular, the damage generated on the surface of the photosensitive layer is likely to appear on the image and directly impairs the image quality, which is a major factor that limits the life of the photoreceptor. That is, in order to develop a long-life photoconductor, it is desired to increase the mechanical strength as well as the electrical and chemical durability.

  In addition, with the increasing demand for high-speed printing, materials that can cope with higher-speed electrophotographic processes have been demanded. In this case, in addition to high sensitivity and long life, the photosensitive member is also desired to have good responsiveness because the time from exposure to development is shortened. It is known that the responsiveness of the photoreceptor is influenced by the charge transport layer, particularly by the combination of the charge transport material and the binder resin.

  Further, in recent years, not only the above-described characteristics such as high sensitivity and long life of the photoconductor but also a photoconductor having high adaptability to the peripheral members of the photoconductor has been demanded as the electrophotographic process is accelerated. ing. Among them, the biggest problem is matching between the photoreceptor and the cleaning blade. If the matching between the photoconductor and the cleaning blade is poor, problems such as poor cleaning due to turning of the cleaning blade and abnormal noise due to the cleaning blade's creeping may occur, especially in the high-speed printing process. Since it appears prominently, it is a very big problem.

  In the case of a general photoreceptor having no functional layer such as a surface protective layer, the photosensitive layer is usually composed of a binder resin and a photoconductive substance. Examples of the binder resin for the photosensitive layer include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymers thereof, thermoplastic resins such as polycarbonate, polyester, polysulfone, phenoxy, epoxy, and silicone resin, and various kinds of heat. A curable resin is used. Among the various binder resins, the polycarbonate resin has relatively excellent performance, and various polycarbonate resins have been developed and put into practical use (for example, see Patent Documents 6 to 9).

Matching between the photoreceptor and the cleaning blade largely depends on the physical properties of the outermost layer of the photosensitive layer and the compatibility of the cleaning blade. The physical properties of the outermost layer of the photosensitive layer largely depend on the combination with the binder resin, charge transport material, charge generation material and other additives used. By changing these combinations, it is possible to adjust the physical properties of the outermost layer of the photosensitive layer. However, the combination of materials that have been used so far has limited optimization. At present, in order to meet the requirements of the physical properties of the outermost layer of the photosensitive layer, the characteristics of sensitivity and life must be sacrificed, and all the characteristics of matching between the photoconductor and its peripheral members, high sensitivity, and long life are required. It was very difficult to meet.
JP-A-61-77054 JP-A 61-188543 JP-A-2-228670 Japanese Examined Patent Publication No. 7-97223 Japanese Examined Patent Publication No. 7-97225 JP 50-98332 A JP 59-71057 A JP 59-184251 JP-A-5-21478

  As described above, the conventional photoconductor does not satisfy all of the plurality of requirements of high sensitivity, long life, and compatibility with peripheral members. For this reason, the printing performance in the case of using the conventional photoconductor is practically limited.

  In order to solve such problems, the present invention provides an electrophotographic photosensitive member having good compatibility with peripheral members of the electrophotographic photosensitive member and good electrical characteristics, an electrophotographic photosensitive member cartridge using the photosensitive member, and An object is to provide an image forming apparatus and an image forming method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have included an electron transport material having a specific structure in the photosensitive layer, so that the electrophotographic photosensitive member has good compatibility with peripheral members and good electrical properties. The inventors have found that an electrophotographic photosensitive member exhibiting characteristics can be provided, and have completed the present invention described below.

  A first aspect of the present invention is an electrophotographic photosensitive member having a photosensitive layer on a conductive support, and the photosensitive layer includes at least a binder resin, a charge generating material, an electron transporting material, and a hole transporting material in the same layer. An electrophotographic photosensitive member that is contained in the electron transporting material and is one or more compounds selected from compounds represented by the following formulas (1) to (3).

(In the formulas (1) to (3), R ¹ represents a substituent having a prescribed substitution number σ _p based on Hammett's rule of 0.450 or more, and Y represents an optionally substituted carbon number of 4 or more. Represents an alicyclic structure of 8 or less, Z represents an optionally substituted cyclic structure having a molecular weight of 400 or less, and M ¹ represents a linking group having a molecular weight of 300 or less.)

  In the first aspect of the present invention, the electron transport material is preferably at least one compound selected from compounds represented by the following formulas (4) to (6).

［式（４）〜（６）中、Ｒ^２はＨａｍｍｅｔｔ則に基づく置換規定数σ_ｐが０．４５０以上である置換基を表し、Ｒ^３〜Ｒ^５は同一でも異なっていてもよい有機基を表し、Ｍ^２は分子量３００以下の連結基を表し、Ｘは以下の（Ｘ１）〜（Ｘ３）のいずれかを表し、

[In the formulas (4) to (6), R ² represents a substituent whose substitution prescribed number σ _p based on Hammett's rule is 0.450 or more, and R ^{3 to} R ⁵ may be the same or different organic groups. M ² represents a linking group having a molecular weight of 300 or less, X represents any of the following (X1) to (X3),

（式（Ｘ２）中、Ｒ^６、Ｒ^７は同一でも異なっていてもよいＨａｍｍｅｔｔ則に基づく置換規定数σ_ｐが０．４５０以上である置換基を表す。）

(In formula (X2), R ⁶ and R ⁷ may be the same or different and each represents a substituent having a prescribed substitution number σ _p based on Hammett's rule of 0.450 or more.)

また、ｎは０〜４の整数を表す。］

N represents an integer of 0 to 4. ]

  In the first aspect of the present invention, the hole transport material is preferably a compound represented by the following formula (7).

（式（７）において、Ａｒ^１〜Ａｒ^６は置換基を有しても良い芳香族残基、または、置換基を有しても良い脂肪族残基を表し、Ｘ’は有機残基を表し、Ｒ^１’〜Ｒ^４’は有機基を表し、ｎ１〜ｎ６は、０〜２の整数を表す。）

(In Formula (7), Ar ^{1 to} Ar ⁶ represent an aromatic residue that may have a substituent or an aliphatic residue that may have a substituent, and X ′ represents an organic residue. represents, ^{R 1} '~R ^4' represents an organic group, n1 to n6 represents an integer of 0 to 2.)

  In the first invention, the binder resin preferably contains a polycarbonate resin containing a monomer unit derived from an aromatic diol component represented by the following formula (8) or a polyarylate resin. .

（式（８）中、Ｌは、下記（Ｌ１）〜（Ｌ５）

(In the formula (8), L represents the following (L1) to (L5)

（式（Ｌ１）中、Ｒ^５'及びＲ^６’は水素原子、炭素数１〜２０のアルキル基、置換されていてもよいアリール基、又は、ハロゲン化アルキル基を表す。）

(In formula (L1), R ⁵ ′ and R ⁶ ′ represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group, or a halogenated alkyl group.)

または単結合を表し、Ｙ¹〜Ｙ⁸は、各々独立に、水素原子、ハロゲン原子、炭素数１〜２０のアルキル基、置換されていてもよいアリール基、又は、ハロゲン化アルキル基を表す。）

Alternatively, it represents a single bond, and Y ^{1 to} Y ⁸ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group, or a halogenated alkyl group. )

In addition, the aromatic diol component represented by the formula (8) preferably excludes the case where R ₅ ′ and R ₆ ′ are bonded to each other to form a ring structure.

The electrophotographic photoreceptor of the first invention preferably uses monochromatic light having an exposure wavelength in the range of 380 nm to 500 nm.
The electrophotographic photoreceptor of the first invention is preferably a positively charged electrophotographic photoreceptor.

  The second aspect of the present invention is an electrophotographic photosensitive member cartridge comprising the electrophotographic photosensitive member of the first aspect of the present invention and a charging device for positively charging the electrophotographic photosensitive member.

  According to a third aspect of the present invention, there is provided an electrophotographic photosensitive member according to the first aspect of the present invention, a charging device for positively charging the electrophotographic photosensitive member, and exposing the charged electrophotographic photosensitive member to produce an electrostatic latent image. An image forming apparatus comprising: an exposure device to be formed; a developing device that develops the electrostatic latent image with toner; and a transfer device that transfers the toner to a transfer target.

  In the third aspect of the present invention, the exposure is preferably monochromatic light having a wavelength of 380 nm to 500 nm.

The fourth aspect of the present invention is a charging step for positively charging the electrophotographic photosensitive member of the first aspect of the present invention, and an exposure step for forming an electrostatic latent image by exposing the charged positively charged electrophotographic photosensitive member An image forming method comprising: a developing step of developing the electrostatic latent image with toner; and a transferring step of transferring the toner to a transfer target.
In the third and fourth inventions, the toner is preferably a toner having an average circularity of 0.95 or more.

  According to the first aspect of the present invention, there is provided an electrophotographic photosensitive member that has good electrical characteristics and good compatibility with peripheral members of the electrophotographic photosensitive member by including an electron transport material having a specific structure in the photosensitive layer. can get. In particular, the effect is remarkably exhibited in the case of a positively charged photoreceptor.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, In the range which does not deviate from the summary, it can change arbitrarily and can implement.

<Electrophotographic photoreceptor>
The electrophotographic photoreceptor of the present invention comprises a photoreceptor on a conductive support, and at least a binder resin, a charge generation material, an electron transport material, and a hole in the same layer of the photoreceptor. Contains transport materials.

  The specific structure of the photosensitive layer is a type in which the charge generation material, the charge transport material, and the hole transport material are present in the same layer and dispersed or dissolved in a binder resin (single layer type or dispersed type). Type). Hereinafter, the charge transport material, the charge generation material, the hole transport material, and the binder resin that exist in the same layer and constitute the photosensitive layer will be described.

(Electron transport material)
The electron transport material that can be used in the present invention includes at least any compound represented by the following formulas (1) to (3). In addition, you may use the compound represented by Formula (1)-(3) in mixture of 2 or more types.

In the formulas (1) to (3), R ¹ represents a substituent having a substitution prescribed number σ _p based on Hammett's rule of 0.450 or more, and Y represents an optionally substituted carbon number of 4 or more and 8 The following alicyclic structures are represented, Z represents an optionally substituted cyclic structure having an aromaticity of a molecular weight of 400 or less, and M ¹ represents a linking group having a molecular weight of 300 or less.

R ¹ in the formulas (1) to (3) will be described. Hammett's rule is an empirical rule used to explain the effect of substituents on aromatic compounds on the electronic state of the aromatic ring. The value of the substitution prescribed number σ _p of the substituted benzene is 0 in the case of a hydrogen atom, and becomes a large positive value as the electron withdrawing property becomes high, and becomes a negative large value as the electron donating property becomes high. Therefore, by using this prescribed substitution number σ _p , it is possible to predict and express the electron density of the electronic state of the aromatic compound having a substituent. The value of the substitution prescribed number σ _p of substituted benzene in Hammett's rule for typical substituents is shown below (The Chemical Society of Japan, “Chemical Handbook, Basic Edition II, Rev. 4” (September 30, 1993, Maruzen ( Issued))).

In formulas (1) to (3), σ _p of R ¹ is usually 0.450 or more, but considering electron transport performance as an electron transport material and characteristics as an electrophotographic photosensitive member, 0.500 or more. More preferably, it is 0.550 or more. Examples of sigma _p is 0.450 or more substituents, an alkyloxycarbonyl group, an aralkyloxycarbonyl group, an ester group such as an aryloxycarbonyl group; a ketone group; a nitrile group; a nitro group; a fluoroalkyl group; alkoxysulfonyl An aralkyloxysulfonyl group, a sulfonyl group of an aryloxysulfonyl group, and the like. Among these, considering electron transport ability and electrophotographic photoreceptor characteristics, R ¹ is preferably a nitrile group, a nitro group, a fluoroalkyl group, or a sulfonyl group, more preferably a nitrile group, a fluoroalkyl group, or a sulfonyl group. More preferably a nitrile group.

When R ¹ in the formulas (1) to (3) is composed of a plurality of carbon atoms, the number of carbon atoms constituting R ¹ is usually 10 or less. If the number of carbon atoms is too large, the bulk of the substituent may increase and the electron transport ability may decrease. Therefore, the number of carbon atoms constituting R ¹ is preferably 8 or less, more preferably 6 or less. More preferably, it is 4 or less.

  In the above formulas (1) to (3), Y represents an alicyclic structure having 4 to 8 carbon atoms which may have a substituent. If the carbon number of the alicyclic structure is too small, the carbon-carbon bond angle becomes small, the distortion of the cyclic structure may increase, and the stability of the compound may decrease. Is preferably 5 or more. In addition, if the number of carbon atoms constituting the alicyclic structure is too large, the molecular volume becomes large, the intermolecular interaction between the electron transport materials in the photosensitive layer may be reduced, and the electron transport ability may be reduced. The carbon number is preferably 7 or less, more preferably 6 or less. Considering both the stability of the compound and the electron transport ability, the alicyclic structure preferably has 5 carbon atoms.

  In said formula (1)-(3), Z represents the cyclic structure which has the aromaticity of the molecular weight 400 or less which may have a substituent. The molecular weight of Z is usually 400 or less, but if it is too large, the solubility is lowered and there is a possibility of adversely affecting the stability of the coating solution. Therefore, it is preferably 350 or less, more preferably 300 or less, More preferably, it is 250 or less, Most preferably, it is 200 or less. Examples of the cyclic structure having aromaticity include a benzenoid aromatic ring, a non-benzenoid aromatic ring, a heteroaromatic ring, etc. Among them, a benzenoid aromatic ring or a heteroaromatic ring is preferable. The number of rings that the cyclic structure having aromaticity has is preferably 5 or less, more preferably 3 or less, and particularly preferably 2 or less. Examples of the benzenoid aromatic ring include benzene, naphthalene, anthracene, pyrene, and perylene, and benzene or naphthalene is preferable, and benzene is more preferable. Examples of non-benzenoid aromatic rings include azulene and ferrocene. Examples of the heteroaromatic ring include pyridine, thiophene, pyrrole, quinoline, indole and the like, and pyridine or quinoline is preferable.

  Y and Z may have a substituent. As the substituent, a substituent composed of 20 or less atoms is preferable, and a substituent composed of 15 or less atoms is more preferable. Specifically, alkyl groups such as alkyl groups, ethyl groups, and propyl groups; alkoxy groups such as methoxy groups, ethoxy groups, and propoxy groups; aryloxy groups such as phenoxy groups; aryl groups such as phenyl groups and naphthyl groups; formyl Groups; alkoxycarbonyl groups such as methoxycarbonyl and ethoxycarbonyl; substituted oxycarbonyl groups such as phenoxycarbonyl; acyloxy groups such as acetoxy group; substituted sulfonyl groups such as methoxysulfonyl and ethoxysulfonyl; acyl groups such as acetyl group and mesyl group; Examples thereof include halogen groups such as fluorine, chlorine and bromine, nitro groups, cyano groups and azo groups.

M ¹ in the above formulas (2) to (3) represents a linking group having a molecular weight of 300 or less. If the molecular weight of M ¹ is too large, the amount of the electron transport unit per unit quantity may decrease, and the characteristics of the electrophotographic photosensitive member may deteriorate. Therefore, the molecular weight of M ¹ is preferably 250 or less, more preferably 200 or less, more preferably 150 or less, particularly preferably 100 or less.

Examples of M ¹ that is a linking group include an alkylene group that may have a substituent, an arylene group that may have a substituent, an oxygen atom, a sulfur atom, and a carbonyl group. Can be mentioned. Among them, an alkylene group which may have a substituent, an arylene group which may have a substituent, a linking group composed of an oxygen atom and a carbonyl group is preferable, and an alkylene which may have a substituent A linking group composed of a group, an arylene group which may have a substituent, and a carbonyl group is more preferable.

  The electron transport materials represented by the formulas (1) to (3) are more preferably represented by the following formulas (4) to (6).

In the formulas (4) to (6), R ² represents a substituent having a substitution prescribed number σ _p based on Hammett's rule of 0.450 or more, and R ^{3 to} R ⁵ represent an organic group which may be the same or different. M ² represents a linking group having a molecular weight of 300 or less,
X represents any of the following (X1) to (X3),

（Ｒ^６、Ｒ^７は同一でも異なっていてもよいＨａｍｍｅｔｔ則に基づく置換規定数σ_ｐが０．４５０以上である置換基を表す）ｎは０〜４の整数を表す。

(R ⁶ and R ⁷ may be the same or different and each represents a substituent having a substitution prescribed number σ _p based on Hammett's rule of 0.450 or more) n represents an integer of 0 to 4.

R ² is the same as ^{R 1} in the formulas (1) to (3).

In the above formulas (4) to (6), R ³ to R ⁵ are organic groups which may be the same or different. The organic group usually has 30 or less carbon atoms, more preferably 20 or less, still more preferably 15 or less, and particularly preferably 10 or less.

Since R ³ is directly bonded to the aromatic ring and affects the electronic state of the aromatic ring and the electron transport ability of the electron transport material, the substitution prescribed number σ _p based on the Hammett rule is 0.200 or more. Preferably, it is 0.450 or more. In view of the electron transport performance as the electron transport material and the characteristics as the electrophotographic photosensitive member, it is more preferably 0.500 or more, and particularly preferably 0.550 or more. Examples of sigma _p is 0.450 or more substituents, the above-mentioned formula (1) include those similar to the examples of ^{R 1} to (3).

  In formulas (4) to (6), n represents an integer of 0 to 4. When the number of n is too large, the versatility of the raw material is lowered, so n is preferably 3 or less, more preferably 2 or less, and even more preferably 1 or less.

Preferable examples of the organic groups represented by R ⁴ and R ⁵ in formulas (4) to (6) include an alkyl group that may have a substituent and an aromatic group that may have a substituent. Can be mentioned. Examples of the alkyl group which may have a substituent include a linear alkyl group such as a methyl group, an ethyl group and a propyl group, and a branched alkyl group such as an isopropyl group, a sec-butyl group and a t-butyl group. And cyclic alkyl groups such as a cyclopentyl group and a cyclohexyl group. Since having a bulky substituent may reduce the interaction with adjacent molecules and reduce the electron transport ability, a linear alkyl group is more preferable among these substituents. Among linear alkyl groups, those having 10 or less carbon atoms are preferred, those having 7 or less carbon atoms are more preferred, and those having 5 or less carbon atoms are more preferred.

  Examples of the aromatic group that may have a substituent include a benzenoid aromatic group, a non-benzenoid aromatic group, and a heteroaromatic ring group. Among these, a benzenoid aromatic group or a heteroaromatic ring group is preferable. The number of rings that the aromatic group has is preferably 5 or less, more preferably 3 or less, and particularly preferably 2 or less. Examples of the benzenoid aromatic group include benzene, naphthalene, anthracene, pyrene, perylene and the like, and among them, benzene or naphthalene is preferable. Examples of the non-benzenoid aromatic group include azulene and ferrocene. In addition, examples of the heteroaromatic ring group include pyridine, thiophene, pyrrole, quinoline, indole and the like, and among them, pyridine or quinoline is preferable. As the condensed polycyclic group, those having 5 or less condensed rings are preferable, and those having 3 or less are more preferable. Specific examples include naphthalene, anthracene, pyrene, perylene, tetralin, carbazole, anthraquinone, and the like, and naphthalene or anthraquinone is preferable.

  Examples of the substituent of the alkyl group which may have a substituent and the aromatic group which may have a substituent include a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a cyclopentyl group, and a cyclohexyl group. Alkyl groups such as phenyl groups; aryl groups such as phenyl groups, naphthyl groups, phenanthyl groups, biphenyl groups, fluorenyl groups; thiophenyl groups, pyrrolyl groups, furanyl groups, benzothiophenyl groups, benzopyrrolyl groups, benfuranyl groups, carbazolyl groups, pyridyl groups Heterocyclic aryl groups such as quinolyl group and phenanthryl group; alkoxy groups such as methoxy group, ethoxy group, isopropoxy group and tert-butoxy group; alkenyl groups such as allyl group; benzyl group, naphthylmethyl group and phenethyl group Aralkyl groups such as phenoxy groups, phenoxy groups, triloxy groups, etc. Aryloxy group; a benzyloxy group, aralkyloxy groups such as phenethyloxy; diaryl alkyl group such as a diphenylmethyl group; a dimethylamino group, a diethylamino group, and a substituted amino group such as a methyl propylamino group. Among these substituents, an alkyl group, an aryl group, an allyl group, an aralkyl group, an alkoxy group, an aryloxy group, and an aralkyloxy group are preferable, and an alkyl group, an aryl group, and an allyl group are more preferable.

  In the formulas (4) to (6), X is preferably the above (X1) or (X2) in consideration of the versatility of the reagent, and more preferably (X2) in consideration of the electron transport ability. .

^R 6, ^{R 7} in formula (X2) are the same as ^{R 1} in the formulas (1) to (3).

^{M 2} in the formula (4) to (5) is the same as ^{M 1} in the above equations (2) to (3).

  Specific examples of the electron transport materials represented by the above formulas (1) to (3), preferably the formulas (4) to (6) are given below. The electron transport material according to the present invention is not limited to the compounds exemplified below.

  As the electron transport material, other electron transport materials other than the compounds represented by the formulas (1) to (6) can be used in combination. Examples of the electron transport material used in combination include aromatic nitro compounds such as 2,4,7-trinitrofluorenone, and electron withdrawing substances such as quinone compounds such as diphenoquinone.

(Charge generation material)
Examples of the charge generation material include selenium and its alloys, cadmium sulfide, other inorganic photoconductive materials, phthalocyanine pigments, azo pigments, dithioketopyrrolopyrrole pigments, squalene (squarylium) pigments, quinacridone pigments, indigo pigments, perylene pigments, Various photoconductive materials such as organic pigments such as polycyclic quinone pigments, anthanthrone pigments, and benzimidazole pigments can be used. Especially, an organic pigment is preferable and a phthalocyanine pigment and an azo pigment are more preferable.

  Specific examples of the phthalocyanine pigment include metals such as metal-free phthalocyanine, copper, indium, gallium, tin, titanium, zinc, vanadium, silicon, and germanium, or oxides, halides, hydroxides, and alkoxides thereof. Various crystal forms of coordinated phthalocyanines are used. In particular, titanyl phthalocyanines (also known as oxytitanium) such as X-type, τ-type metal-free phthalocyanine, A-type (also known as β-type), B-type (also known as α-type), and D-type (also known as Y-type), which are highly sensitive crystal types Phthalocyanine), vanadyl phthalocyanine, chloroindium phthalocyanine, chlorogallium phthalocyanine such as type II, hydroxygallium phthalocyanine such as type V, μ-oxo-gallium phthalocyanine dimer such as type G and type I, μ-oxo such as type II -Aluminum phthalocyanine dimer is preferred. Of these, metal-containing phthalocyanines containing a metal at the center of the phthalocyanine ring are preferable. Among metal-containing phthalocyanines, A-type (β-type), B-type (α-type), D-type (Y-type) oxytitanium phthalocyanine, and II-type chlorogallium. Phthalocyanine, V-type hydroxygallium phthalocyanine, G-type μ-oxo-gallium phthalocyanine dimer and the like are more preferable, and A-type (β-type), B-type (α-type), and D-type (Y-type) oxytitanium phthalocyanine are more preferable. .

  In particular, as the oxytitanium phthalocyanine, those having a clear diffraction peak mainly at a Bragg angle (2θ ± 0.2 °) of 27.2 ° in a powder X-ray diffraction spectrum by CuKα characteristic X-ray are preferable.

  The oxytitanium phthalocyanine has a clear diffraction peak at a Bragg angle (2θ ± 0.2 °) of 9.0 ° to 9.7 ° in a powder X-ray diffraction spectrum by CuKα characteristic X-ray. preferable.

  As the azo pigment, various known bisazo pigments and trisazo pigments are preferably used. Examples of preferred azo pigments are shown below.

  The type of pigment used as the charge generation material may be determined by the exposure wavelength used. When the exposure wavelength is in the short wavelength region of about 380 nm to 500 nm, the above azo pigment is preferably used. On the other hand, when near-infrared light of about 630 nm to 780 nm is used, a phthalocyanine pigment having high sensitivity also in that region and a part of azo pigments are preferably used. On the other hand, when environmental characteristics such as humidity dependency are required to be small, the Bragg angle (2θ ± 0.2 °) is set to 9.0 ° to 9.7 ° in the powder X-ray diffraction spectrum by CuKα characteristic X-ray. Since oxytitanium phthalocyanine having a clear diffraction peak is highly dependent on humidity, the above azo pigment is preferably used.

  The particle size of the charge generating material used is preferably sufficiently small, specifically, usually 1 μm or less, preferably 0.5 μm or less.

  The amount of the charge generating material in the monolayer type photosensitive layer is usually 0.5% by mass or more, preferably 1% by mass or more, and the upper limit is based on the whole monolayer type photosensitive layer (100% by mass). Usually, it is 50 mass% or less, Preferably it is 20 mass% or less. If the amount of the charge generating material dispersed in the photosensitive layer is too small, sufficient sensitivity may not be obtained. If the amount is too large, there is a risk of adverse effects such as a decrease in chargeability and a decrease in sensitivity.

(Hole transport material)
The hole transport material is not particularly limited, and any known hole transport material can be used. Examples of known hole transport materials include carbazole derivatives, indole derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, thiadiazole derivatives, heterocyclic compounds such as benzofuran derivatives, aniline derivatives, hydrazone derivatives, aromatic amine derivatives, stilbene derivatives. , Butadiene derivatives, enamine derivatives, and those obtained by bonding a plurality of these compounds, or electron donating substances such as polymers having groups composed of these compounds in the main chain or side chain. Among these, carbazole derivatives, aromatic amine derivatives, stilbene derivatives, butadiene derivatives, enamine derivatives, and those in which a plurality of these compounds are bonded are preferable. In addition, any 1 type may be used independently for a hole transport material, and 2 or more types may be used together by arbitrary combinations and a ratio.

  A preferred structure for the hole transport material is shown in the following formula (7).

In Formula (7), Ar ^{1 to} Ar ⁶ represent an aromatic residue that may have a substituent or an aliphatic residue that may have a substituent, and X ′ represents an organic residue. , R ¹ ′ to R ⁴ ′ represent an organic group, and n1 to n6 represent an integer of 0 to 2.

In formula (7), Ar ^{1 to} Ar ⁶ represent an aromatic residue that may have a substituent or an aliphatic residue that may have a substituent. Specific aromatic residues include aromatic hydrocarbon residues such as benzene, naphthalene, anthracene, pyrene, perylene, phenanthrene, and fluorene, and aromatic heterocyclic residues such as thiophene, pyrrole, carbazole, and imidazole. It is done. The number of carbon atoms of these aromatic residues is preferably 5 to 20, more preferably 16 or less, and even more preferably 10 or less. The lower limit is more preferably 6 or more from the viewpoint of electrical characteristics. As the aromatic residue, an aromatic hydrocarbon residue is preferable, and among them, a benzene residue is particularly preferable.

  Moreover, as a specific aliphatic residue, a C1-C20 aliphatic residue is preferable, A C16 or less aliphatic residue is more preferable, A C10 or less aliphatic residue is still more preferable . In the case of a saturated aliphatic residue, 6 or less carbon atoms are particularly preferred, and in the case of an unsaturated aliphatic residue, 2 or more carbon atoms are particularly preferred. Examples of the saturated aliphatic residue include branched and straight-chain alkyl residues such as methane, ethane, propane, isopropane, and isobutane. Examples of the unsaturated aliphatic residue include alkene residues such as ethylene and butylene.

  In addition, the substituent of the aromatic residue or aliphatic residue is not particularly limited, and examples thereof include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, and allyl group; methoxy group, ethoxy group And alkoxy groups such as propoxy group; aryl groups such as phenyl group, indenyl group, naphthyl group, acenaphthyl group, phenanthryl group and pyrenyl group; and heterocyclic groups such as indolyl group, quinolyl group and carbazolyl group. Moreover, these substituents may combine with each other to form a ring.

By introducing the above-described substituent into the aromatic residue or aliphatic residue of Ar ^{1 to} Ar ⁶ , there is an effect of adjusting the intramolecular charge and increasing the charge mobility. However, on the other hand, if the bulk becomes too large, the charge mobility is lowered due to the distortion of the conjugated surface in the molecule and the intermolecular steric repulsion. Therefore, the lower limit of the number of carbon atoms of the substituent is preferably 1 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and still more preferably 2 or less.

In addition, when the aromatic residue or the aliphatic residue of Ar ^{1 to} Ar ⁶ has a substituent, it is preferable to have a plurality of substituents because it avoids crystal precipitation. However, when there are too many substituents, the charge mobility is lowered due to the distortion of the conjugated surface in the molecule and the intermolecular steric repulsion. For this reason, when Ar ^{1 to} Ar ⁶ are aromatic residues, the number of substituents is preferably 2 or less per aromatic residue. In order to improve the stability in the photosensitive layer and improve the electrical characteristics, the substituent is preferably not sterically bulky. More specifically, a methyl group, an ethyl group, a butyl group, an isopropyl group, A methoxy group is preferred.

In particular, when Ar ^{1 to} Ar ⁴ are benzene residues, it is preferable that Ar ^{1 to} Ar ⁴ have a substituent, and in this case, a preferable substituent is an alkyl group, and among them, an ethyl group and a methyl group are more preferable. A methyl group is more preferable. Moreover, when Ar < ⁵ > -Ar < ⁶ > is a benzene residue, the preferable substituent of Ar < ⁵ > -Ar < ⁶ > is a methyl group, an ethyl group, and a methoxy group, and a more preferable substituent is a methyl group and a methoxy group.

  X ′ is an organic residue, for example, an aromatic residue, a saturated aliphatic residue, a heterocyclic residue, an organic residue having an ether structure, or a divinyl structure, which may have a substituent. Examples thereof include organic residues. Among them, an organic residue having 1 to 15 carbon atoms is preferable, and an organic residue having 1 to 15 carbon atoms having an aromatic residue, a saturated aliphatic residue, an ether structure, or a divinyl structure is preferable. , Aromatic residues, saturated aliphatic residues, or organic residues having an ether structure and having 1 to 15 carbon atoms. In the case of an aromatic residue, the number of carbon atoms is preferably 6 or more and 14 or less, more preferably 12 or less, and even more preferably 10 or less. In the case of a saturated aliphatic residue, the number of carbon atoms is preferably 1 or more and 10 or less, and more preferably 8 or less. In the case of an organic residue having a divinyl structure, the carbon number is preferably 6 or more and 14 or less, more preferably 12 or less, and even more preferably 10 or less. In the case of an organic residue having an ether structure, the number of carbon atoms is preferably 1 or more and 10 or less, and more preferably 8 or less.

  The organic residue X ′ may have a substituent. There are no particular restrictions on the substituent, but alkyl groups such as methyl, ethyl, propyl, isopropyl, and allyl groups; alkoxy groups such as methoxy, ethoxy, and propoxy groups; phenyl groups, indenyl groups, and naphthyl groups And aryl groups such as acenaphthyl, phenanthryl, and pyrenyl; and heterocyclic groups such as indolyl, quinolyl, and carbazolyl.

  Further, the substituent of X ′ may be bonded to each other to form a ring. Further, the lower limit of the number of carbon atoms of the substituent for X ′ is preferably 1 or more, and the upper limit is preferably 10 or less, more preferably 6 or less, and even more preferably 3 or less. More specifically, the substituent is preferably a methyl group, an ethyl group, a butyl group, an isopropyl group, a methoxy group, or the like.

  In addition, when X ′ has a substituent, it is preferable to have a plurality of substituents because it avoids crystal precipitation. However, when the number of substituents is too large, the charge mobility is lowered due to distortion of the conjugated surface in the molecule and steric repulsion between molecules. Therefore, the number of substituents for X ′ is preferably 2 or less for each X ′.

  n1-n4 represents the integer of 0-2. n1 is preferably 1, and n2 is preferably 0 or 1.

R ¹ ′ to R ⁴ ′ in formula (7) are organic groups. The carbon number of the organic group is usually 30 or less, more preferably 20 or less, further preferably 15 or less, and particularly preferably 13 or less. Preferred organic groups as R ¹ ′ to R ⁴ ′ are alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and an allyl group; an alkoxy group such as a methoxy group, an ethoxy group, and a propoxy group; The organic group represented is mentioned.

R ¹ ″ to R ¹⁵ ″ may be the same or different. R ¹ ″ to R ¹⁵ ″ are preferably a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, or the like, and more preferably a methyl group or a phenyl group.

  n5 or n6 represents an integer of 0 to 2. When n5 is 0, it represents a direct bond, and when n6 is 0, n5 is preferably 0.

When both n5 and n6 are 1, X ′ is preferably an alkylidene group, an arylene group, or an organic residue having an ether structure. As the alkylidene group, phenylmethylidene, 2-methylpropylidene, 2-methylbutylidene, cyclohexylidene and the like are preferable. As the arylene group, phenylene, naphthylene and the like are preferable. Moreover, as an organic residue having an ether structure, —O— (CH ₂ ) _n7 —O— or the like is preferable, and n7 is preferably 1.

When n5 and n6 are both 0, Ar ⁵ is preferably a benzene residue or a fluorene residue. When it is a benzene residue, it preferably has an alkyl group or an alkoxy group as a substituent, and more preferably has a methyl group or a methoxy group as a substituent. The substitution position of the substituent is preferably the para position of the nitrogen atom.

  When n6 is 2, X ′ is preferably a benzene residue.

  Examples of specific combinations of n1 to n6 are summarized in Table 2 below.

  A preferred structure of the general formula (7) is shown below.

  In the above general formulas (7-1) to (7-17), Q may be the same or different, and specifically, is preferably a hydrogen atom, an alkyl group, an alkoxy group, or an aryl group, More preferred are a methyl group and a phenyl group. n8-n10 is an integer of 0-2.

  Preferred specific examples of the general formula (7) are shown below as C-1 to C-27.

  Among these hole transport materials, monostilbene-based C-12 to C-17 tends to have a high potential after exposure. Therefore, it is preferable to use distilbene C-18 and C-20 or butadiene C-19, C-21 and C-22 as the hole transport material. In addition, benzidine-based C-1 to C-5, when used alone, may cause crystals to precipitate in the coating solution or the photosensitive layer, and therefore it is preferable to use a mixture of two or more.

  The amount of the hole transport material used is arbitrary as long as the effects of the present invention are not significantly impaired, but the lower limit is usually 30 parts by mass or more, preferably 40 parts by mass or more with respect to 100 parts by mass of the binder resin in the photosensitive layer. The upper limit is usually 200 parts by mass or less, preferably 150 parts by mass or less. If the amount of the hole transport material is too small, the electrical characteristics may be deteriorated. If the amount is too large, the coating film becomes brittle and the wear resistance may be deteriorated.

(Binder resin)
In the present invention, the single-layer type photosensitive layer is formed by applying a coating solution obtained by dissolving or dispersing a charge generating material, a charge transporting material, a hole transporting material, and a binder resin in a solvent on a conductive support. Can be obtained by drying. Examples of the binder resin include polymers and copolymers of vinyl compounds such as butadiene resin, styrene resin, vinyl acetate resin, vinyl chloride resin, acrylic ester resin, methacrylic ester resin, vinyl alcohol resin, ethyl vinyl ether, and polyvinyl butyral. Resin, polyvinyl formal resin, partially modified polyvinyl acetal, polycarbonate resin, polyester resin, polyarylate resin, polyamide resin, polyurethane resin, cellulose ester resin, phenoxy resin, silicone resin, silicone-alkyd resin, poly-N-vinylcarbazole resin, etc. Is mentioned. These resins may be modified with a silicon reagent or the like.

  In particular, in the present invention, the binder resin preferably contains one or more kinds of polymers obtained by interfacial polymerization. Interfacial polymerization is a polymerization method that utilizes a polycondensation reaction that proceeds at the interface of two or more solvents (mostly organic solvents-water systems) that do not mix with each other. For example, a dicarboxylic acid chloride is dissolved in an organic solvent, a glycol component is dissolved in alkaline water, etc., and both liquids are mixed at room temperature to be separated into two phases. At the interface, a polycondensation reaction proceeds to produce a polymer. Let Examples of other two components include phosgene and an aqueous glycol solution. Further, as in the case of condensing a polycarbonate oligomer by interfacial polymerization, the two components are not divided into two phases, but the interface may be used as a polymerization field.

  As the reaction solvent for interfacial polymerization, it is preferable to use two layers of an organic phase and an aqueous phase. Methylene chloride is preferable as the organic phase, and an alkaline aqueous solution is preferable as the aqueous phase.

  During the interfacial polymerization reaction, it is preferable to use a catalyst, and the amount of the catalyst to be used is about 0.005 mol% to 0.1 mol%, preferably 0.03 mol% to 0.08 mol%, based on the diol component. is there. If it exceeds 0.1 mol%, a great deal of labor is required to extract and remove the catalyst in the washing step after polycondensation, which is not preferable.

  The reaction temperature of the interfacial polymerization is preferably 80 ° C. or lower, more preferably 60 ° C. or lower, and further preferably 10 ° C. to 50 ° C. The reaction time depends on the reaction temperature, but is usually 0.5 minutes to 10 hours, preferably 1 minute to 2 hours. If the reaction temperature is too high, the side reaction cannot be controlled. On the other hand, if the reaction temperature is too low, the reaction control is preferable, but the refrigeration load increases and the cost increases accordingly.

  Moreover, the density | concentration in an organic phase should just be a range with which the composition obtained is soluble, and is specifically about 10 mass%-40 mass%.

  Moreover, it is preferable that the amount of the solvent is adjusted so that the concentration of the generated resin in the organic phase obtained by polycondensation is 5% by mass to 30% by mass based on the whole organic phase (100% by mass). . Thereafter, an aqueous phase containing water and alkali metal hydroxide is newly added, and in order to further adjust the polycondensation conditions, a condensation catalyst is preferably added and the desired polycondensation is completed according to the interfacial polycondensation method. The ratio of the organic phase to the aqueous phase during polycondensation is preferably about 1: 0.2 to 1 in terms of volume ratio.

  The binder resin preferably contains a polycarbonate resin and / or a polyester resin (in particular, a polyarylate resin is preferable) obtained by the interfacial polymerization.

  The polycarbonate resin and polyarylate resin preferably include a monomer unit derived from an aromatic diol component represented by the following formula (8).

  In formula (8), L represents the following (L1) to (L5)

（式（Ｌ１）中、Ｒ^５’およびＲ^６’は水素原子、炭素数１〜２０のアルキル基、置換されていてもよいアリール基、又は、ハロゲン化アルキル基を表す。）

(In the formula (L1), R ⁵ ′ and R ⁶ ′ represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group, or a halogenated alkyl group.)

Alternatively, it represents a single bond, and Y ^{1 to} Y ⁸ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group, or a halogenated alkyl group. .

  In formula (8), L is preferably (L1), (L2) or a single bond, more preferably (L1) or a single bond from the surface property of the photosensitive layer.

In formula (8), R ^{5 ′} and R ^{6 ′} may be the same or different, a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group which may have a substituent, or an alkyl halide. Represents a group. Among these structures, a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an optionally substituted aryl group are preferable. When R ^{5 ′} and R ^{6 ′} are an alkyl group, the alkyl group may be a linear alkyl group, a branched alkyl group, or a cyclic alkyl group such as a cycloalkyl group, but is preferably a chain alkyl group. Even more preferred are chain alkyl groups. When R ^{5 ′} and R ^{6 ′} are alkyl groups, the carbon number is usually in the range of 1 to 20, preferably 8 or less, more preferably 5 or less, and even more preferably 4 or less. Examples of the case where R ^{5 ′} and R ^{6 ′} are an alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a nonyl group, A dodecyl group, and the like, more preferably a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, and an octyl group, and more preferably a methyl group and an ethyl group. Propyl group, butyl group, pentyl group and hexyl group, particularly preferably methyl group, ethyl group, propyl group and butyl group. This is because if the number of carbon atoms is excessively increased, the effect obtained by the present invention may be reduced. R ^{5 ′} and R ^{6 ′} can be bonded to each other to form a ring structure such as cyclohexylidene. However, when the ring structure is formed, the surface slipperiness of the photosensitive layer tends to deteriorate. It is preferable not to form a ring structure.

Examples of the aryl group which may have a substituent of R ^{5 ′} and R ^{6 ′} include a phenyl group, an indenyl group, a naphthyl group, an acenaphthyl group, a phenanthryl group, a pyrenyl group, and the like. From the viewpoint of liquid stability, a phenyl group is more preferable. Examples of the substituent which the aryl group which may have a substituent may have include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group and allyl group; methoxy group, ethoxy group, propoxy group and the like Of the alkoxy group. Moreover, these substituents may combine with each other to form a ring. These substituents preferably have 1 or more carbon atoms, preferably 10 or less carbon atoms, more preferably 6 or less carbon atoms, and particularly 3 or less carbon atoms. More specifically, a methyl group, an ethyl group, a butyl group, an isopropyl group, a methoxy group, and the like are preferable.

In Formula (8), Y ^{1 to} Y ⁸ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group which may have a substituent, or a halogenated alkyl group. Indicates. Of these structures, a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an aryl group which may have a substituent are preferable from the viewpoint of the characteristics of the electrophotographic photoreceptor. When Y ^{1 to} Y ⁸ are alkyl groups, the alkyl group may be a chain alkyl group or a cycloalkyl group, and may be a linear alkyl group or a branched alkyl group, but a chain alkyl group is preferred, and A chain alkyl group is particularly preferred. The number of carbon atoms of the alkyl group in Y ^{1 to} Y ⁸ is not particularly limited, but is preferably 8 or less, more preferably 6 or less, still more preferably 4 or less, and particularly preferably 2 or less. Examples of the alkyl group for Y ^{1 to} Y ⁸ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a nonyl group, and a dodecyl group. If the number of carbon atoms is too large, the abrasion resistance of the photosensitive layer may be lowered. Therefore, when Y ¹ to Y ⁸ are alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is preferable. Groups are more preferred.

Examples of the aryl group that may have a substituent of Y ^{1 to} Y ⁸ include a phenyl group, an indenyl group, a naphthyl group, an acenaphthyl group, a phenanthryl group, and a pyrenyl group. Among these structures, a coating solution A phenyl group is more preferable from the viewpoint of stability. Examples of the substituent that the aryl group may have include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, and allyl group; and alkoxy groups such as methoxy group, ethoxy group, and propoxy group. Moreover, these substituents may combine with each other to form a ring. The lower limit of the number of carbon atoms of these substituents is preferably 1 or more, and the upper limit is preferably 10 or less, more preferably 6 or less, and further preferably 3 or less. Specifically, the substituent is preferably a methyl group, an ethyl group, a butyl group, an isopropyl group, a methoxy group, or the like.

When the proportion of the alkyl group having 1 to 20 carbon atoms, the optionally substituted aryl group, or the halogenated alkyl group in Y ^{1 to} Y ⁸ increases, the solubility of the binder resin in the coating solvent decreases. Therefore, at least two of Y ¹ to Y ⁸ are preferably hydrogen atoms, more preferably four or more are hydrogen atoms, and six or more are hydrogen atoms. More preferably.

  Among the polycarbonate resin containing the monomer unit derived from the aromatic diol component represented by the above formula (8) and the polyarylate resin, the polycarbonate resin containing the monomer unit derived from the aromatic diol component having the following structural formula, Polyarylate resin is preferred from the viewpoint of sensitivity and residual potential. Among these, from the viewpoint of mobility, a polycarbonate resin containing a monomer unit derived from an aromatic diol component having the following structural formula is more preferable.

  Moreover, it is preferable to use the thing of the following structures as a dicarboxylic acid component used for the polyarylate resin of this application.

  Moreover, when using the said terephthalic acid and isophthalic acid together, it is preferable that the ratio of terephthalic acid is 40 mol% or more on the basis of the total amount of terephthalic acid and isophthalic acid (100 mol%), and the ratio of terephthalic acid Is more preferably 50 mol% or more. In particular, it is preferable to use a dicarboxylic acid component having the following structure from the viewpoint of durability of the photoreceptor.

  The photosensitive layer may contain an additive. These additives are used to improve film formability, flexibility, mechanical strength, etc., for example, plasticizers, residual potential inhibitors for suppressing residual potential, and for improving dispersion stability. Dispersion aids, leveling agents for improving coating properties (for example, silicone oil, fluorine oil, etc.), surfactants and the like. In addition, 1 type may be used for an additive and it may use 2 or more types together by arbitrary combinations and a ratio.

  In the photoreceptor of the present invention, the thickness of the photosensitive layer is not particularly limited as long as the effect of the present invention is not significantly impaired, but is usually 5 μm or more, preferably 10 μm or more, and usually 50 μm or less, preferably 45 μm or less. It is.

  Note that the photoconductor of the present application is a single-layer photoconductor for positive charging, and charge pairs are generated mainly at a depth position near the surface of the photoconductor by light irradiation. Therefore, the movement distance required for electrons to cancel the positive charge on the surface is short, and the lateral diffusion during movement is small. For this reason, even if the film thickness is increased, the image is not easily blurred. Even when coherent light such as a laser is used, it is difficult for light to reach the substrate, so that defects such as interference fringes are hardly generated. Another feature is that even if the substrate has a defect, it is difficult to affect the image. On the other hand, in the laminated type (having a charge generation layer and a charge transport layer in this order on a substrate) described in the examples of JP-A-5-210253, the image blur due to the diffusion of charges is thick. This is more likely to occur, which is also disadvantageous in terms of interference fringes and substrate defects.

  On the other hand, in the case of a single layer type photoreceptor, there are few suitable combinations of a charge generation material and an electron transport material, and selection of materials is often difficult even when compared with a laminated type photoreceptor. This is because, in a positively charged laminated photoconductor (when a charge generation layer and a charge transport layer are provided in this order on a substrate), holes generated in the charge generation material immediately escape to the substrate. In contrast to the need for a transport material, in the case of a positively charged single layer type photoconductor, the charge transport material is generated to a certain depth from the surface of the photosensitive layer (for example, 5 μm from the surface of the photoconductor having a film thickness of 25 μm). It is necessary to transport each positive and negative charge pair, and both hole transport material and electron transport material are necessary. In this case, since the sensitivity decreases when the holes transported by the hole transport material and the electrons transported by the electron transport material are recombined before moving to the surface of the substrate and the photosensitive layer, respectively, the combination is difficult to recombine. Is required.

  In addition, when a new electron transport material is selected for the positively charged single-layer type photoreceptor, it is necessary for the electron transport material to accept the electrons generated in the charge generation material with high efficiency, and the LUMO level of both is high. It becomes important. In this case, it is preferable that the LUMO level of the electron transport material is lower than the LUMO level of the charge generation material.

(Conductive support)
As the conductive support, for example, a metal material such as aluminum, aluminum alloy, stainless steel, copper, nickel or the like, a resin material added with conductivity by adding conductive powder such as metal, carbon, tin oxide, or aluminum, Mainly used are resin, glass, paper, or the like obtained by depositing or coating a conductive material such as nickel or ITO (indium tin oxide alloy) on its surface. As a form, a drum shape, a sheet shape, a belt shape or the like is used. A conductive material having an appropriate resistance value may be coated on a conductive support made of a metal material for controlling conductivity, surface property, etc., or for covering defects.

  When a metal material such as an aluminum alloy is used as the conductive support, it may be used after an anodized film is applied. When an anodized film is applied, it is desirable to perform a sealing treatment by a known method.

For example, an anodic oxidation film is formed by anodizing in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, boric acid, sulfamic acid, etc. give. In the case of anodic oxidation in sulfuric acid, the sulfuric acid concentration is 100 g / l to 300 g / l, the dissolved aluminum concentration is 2 g / l to 15 g / l, the liquid temperature is 15 ° C. to 30 ° C., the electrolysis voltage is 10 V to 20 V, and the current density. Is preferably set within the range of 0.5 A / dm ^{2 to 2} A / dm ² , but is not limited to the above conditions.

  It is preferable to perform a sealing treatment on the anodic oxide film thus formed. The sealing treatment may be performed by a known method. For example, the low-temperature sealing treatment is performed by immersing in an aqueous solution containing nickel fluoride as a main component, or an aqueous solution containing a metal salt such as nickel acetate as a main component. It is preferable to perform a high temperature sealing treatment to be immersed therein.

  The concentration of the nickel fluoride aqueous solution used in the case of the low-temperature sealing treatment can be appropriately selected, but more preferable results can be obtained when it is used in the range of 3 to 6 g / l. In order to smoothly proceed with the sealing treatment, the treatment temperature is 25 ° C. to 40 ° C., preferably 30 ° C. to 35 ° C., and the pH of the nickel fluoride aqueous solution is 4.5 to 6.5, preferably Is preferably processed in the range of 5.5 to 6.0. As the pH adjuster, oxalic acid, boric acid, formic acid, acetic acid, sodium hydroxide, sodium acetate, aqueous ammonia and the like can be used. The treatment time is preferably in the range of 1 to 3 minutes per 1 μm of film thickness. In order to further improve the physical properties of the film, cobalt fluoride, cobalt acetate, nickel sulfate, a surfactant or the like may be added to the nickel fluoride aqueous solution. Subsequently, it is washed with water and dried to finish the low temperature sealing treatment.

  As the sealing agent in the case of the high-temperature sealing treatment, an aqueous solution of a metal salt such as nickel acetate, cobalt acetate, lead acetate, nickel acetate-cobalt, and barium nitrate can be used. Among these, nickel acetate is used. preferable. The concentration in the case of using an aqueous nickel acetate solution is preferably in the range of 5 g / l to 20 g / l. The treatment temperature is 80 ° C. to 100 ° C., preferably 90 ° C. to 98 ° C., and the pH of the nickel acetate aqueous solution is preferably 5.0 to 6.0. Here, ammonia water, sodium acetate, or the like can be used as the pH adjuster. The treatment time is 10 minutes or longer, preferably 15 minutes or longer. In this case as well, sodium acetate, organic carboxylic acid, anionic and nonionic surfactants may be added to the nickel acetate aqueous solution in order to improve the film properties. Furthermore, you may process with high temperature water and high temperature steam which do not contain salt substantially. Subsequently, it is washed with water and dried to finish the high temperature sealing treatment. When the average film thickness is thick, stronger sealing conditions are required due to the higher concentration of the sealing liquid and high temperature / long-time treatment. Accordingly, productivity is deteriorated and surface defects such as spots, dirt, and dusting are likely to occur on the coating surface. From such a point, it is preferable that the average film thickness of the anodic oxide coating is usually 20 μm or less, particularly 7 μm or less.

  The surface of the conductive support may be smooth, or may be roughened by using a special cutting method or performing a polishing treatment. Further, it may be roughened by mixing particles having an appropriate particle diameter with the material constituting the support. An undercoat layer may be provided between the conductive support and the photosensitive layer in order to improve adhesion and blocking properties.

  As the undercoat layer, a resin layer, a layer in which metal oxide particles are dispersed in a resin, or the like is used. Examples of metal oxide particles used for the undercoat layer include metal oxide particles containing one metal element such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zinc oxide, iron oxide, calcium titanate, titanium Examples thereof include metal oxide particles containing a plurality of metal elements such as strontium acid and barium titanate. Only one type of particle may be used, or a plurality of types of particles may be mixed and used. Among these metal oxide particles, titanium oxide and aluminum oxide are preferable, and titanium oxide is particularly preferable. The surface of the titanium oxide particles may be treated with an inorganic material such as tin oxide, aluminum oxide, antimony oxide, zirconium oxide, or silicon oxide, or an organic material such as stearic acid, polyol, or silicone. As the crystal form of the titanium oxide particles, any of rutile, anatase, brookite, and amorphous can be used. Moreover, the thing of a several crystal state may be contained.

  In addition, various particle sizes of metal oxide particles can be used. Among them, from the viewpoint of characteristics and liquid stability, the average temporary particle size is preferably 10 nm or more and 100 nm or less, and particularly preferably 10 nm or more. 50 nm or less.

  The undercoat layer is preferably a layer formed by dispersing metal oxide particles in a binder resin. Examples of the binder resin used for the undercoat layer include phenoxy resin, epoxy resin, polyvinyl pyrrolidone, polyvinyl alcohol, casein, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, and polyamide. These binder resins may be used alone or in admixture of two or more. Moreover, you may use in the form hardened | cured with the hardening | curing agent. Among these, alcohol-soluble copolymerized polyamide, modified polyamide, and the like are preferable because they exhibit good dispersibility and coatability.

  The content ratio of the metal oxide particles is not particularly limited, but the range of 0% by mass to 1000% by mass with respect to the stability of the dispersion and coatability is based on the total binder resin used in the undercoat layer (100% by mass). In terms of surface. Furthermore, the range of 10 mass% to 700 mass% is more preferable, and the range of 100 mass% to 400 mass% is particularly preferable.

  In the case of a photoreceptor containing at least a binder resin, a charge generation material, an electron transport material, and a hole transport material in the same layer as in the present invention, only the photosensitive layer is provided on a conductive support. In such a case, the adhesion between the support and the photosensitive layer is poor, and the photosensitive layer may peel off during use. In order to prevent this, a layer having a charge generating material can be used as a subbing layer. In this case, as the undercoat layer, a phthalocyanine pigment or an azo pigment dispersed and applied in a binder resin is preferably used. In this case, electrical characteristics may be particularly excellent, which is preferable.

  The thickness of the undercoat layer can be arbitrarily selected, but is preferably 0.1 μm to 20 μm from the characteristics and applicability of the photoreceptor. The undercoat layer may contain a known antioxidant or the like.

(Other layers)
In addition to the above-described undercoat layer and single-layer type photosensitive layer, the positively charged electrophotographic photosensitive member of the present invention may further include other layers. For example, for the purpose of preventing wear of the single layer type photosensitive layer on the single layer type photosensitive layer, or preventing or reducing deterioration of the single layer type photosensitive layer due to discharge products generated from a charger or the like. A layer may be provided. In addition, the outermost surface layer may contain, for example, a fluorine-based resin, a silicone resin, or the like for the purpose of reducing frictional resistance and wear on the surface of the single-layer type photoreceptor, and particles made of these resins. Or particles of inorganic compounds may be included.

(Method for forming each layer)
There is no limitation on the method of forming each layer such as the undercoat layer, the single-layer type photosensitive layer, and the protective layer. For example, a known method such as applying a coating solution obtained by dissolving or dispersing a substance to be contained in a layer to be formed in a solvent on a conductive support directly or sequentially via another layer is applied. it can. For example, the single-layer type photosensitive layer can be formed by the following method. That is, a coating liquid containing an electron transport material, a charge generation material, a binder resin, a hole transport material, and a solvent, a binder resin to be used in combination, an additive, and the like as necessary is prepared. Then, the coating solution is applied directly on the conductive support or on the undercoat layer when an undercoat layer is provided. Thereafter, the solvent is removed by drying, whereby a single-layer type photosensitive layer can be formed.

  At this time, the coating method is not limited and is arbitrary, and for example, a dip coating method, a spray coating method, a nozzle coating method, a bar coating method, a roll coating method, a blade coating method and the like can be used. Among these, the dip coating method is preferable because of its high productivity. In addition, these coating methods may perform only one method and may combine two or more methods.

(Charge type of photoconductor)
The photoreceptor of the present invention is used for image forming applications by being used in an image forming apparatus described later. However, the photoreceptor of the present invention is a positively charged photoreceptor, and is used by being positively charged in the charging step of the electrophotographic process.

(Exposure wavelength of photoconductor)
In the photoconductor of the present invention, when an image is formed, exposure is performed by writing light from an exposure unit to form an electrostatic latent image. The writing light used at this time is arbitrary as long as an electrostatic latent image can be formed, but the exposure wavelength is preferably 380 nm or more, more preferably 400 nm or more, and preferably 800 nm or less, more preferably 700 nm or less. More preferably, monochromatic light of 500 nm or less is used. Among them, it is preferable to expose with monochromatic light of 480 nm or less when a high quality image is desired. In this case, the photosensitive member can be exposed with light having a smaller spot size, and a high-quality image having high resolution and high gradation can be formed.

<Image forming apparatus>
Next, an embodiment of an image forming apparatus using the electrophotographic photosensitive member of the present invention (an image forming apparatus of the present invention) will be described with reference to FIG.

  As shown in FIG. 1, an image forming apparatus of the present invention includes a positively charged electrophotographic photosensitive member 1, a charging device (charging means) 2, an exposure device (exposure means; image exposure means) 3, and a developing device (developing means). 4, a transfer device (transfer means) 5, a cleaning device (cleaning means) 6, and a fixing device (fixing means) 7 are provided as necessary.

  The positively charged electrophotographic photosensitive member 1 is not particularly limited as long as it is the above-described positively charged electrophotographic photosensitive member of the present invention, but in FIG. 1, as an example, the surface of the cylindrical conductive support is described above. 2 shows a drum-shaped photoreceptor on which a single-layer type photosensitive layer is formed. A charging device 2, an exposure device 3, a developing device 4, a transfer device 5, and a cleaning device 6 are arranged along the outer peripheral surface of the positively charged electrophotographic photosensitive member 1.

  The charging device 2 charges the positively charged electrophotographic photosensitive member 1 positively, and uniformly charges the surface of the positively charged electrophotographic photosensitive member 1 to a predetermined potential. In FIG. 1, a roller type charging device (charging roller) is shown as an example of the charging device 2, but a corona charging device such as a corotron or a scorotron, a contact type charging device such as a charging brush, etc. are often used.

  In many cases, the positively charged electrophotographic photosensitive member 1 and the charging device 2 are cartridges having both of them (the electrophotographic photosensitive member cartridge of the present invention; hereinafter referred to as “photosensitive member cartridge”). It is designed to be removable from the main body of the image forming apparatus. However, the charging device 2 may be provided separately from the cartridge, for example, in the main body of the image forming apparatus. For example, when the positively charged electrophotographic photoreceptor 1 or the charging device 2 deteriorates, the photoreceptor cartridge can be removed from the image forming apparatus body and another new photoreceptor cartridge can be mounted on the image forming apparatus body. It can be done. Also, the toner described later is often stored in the toner cartridge and designed to be removable from the main body of the image forming apparatus. When the toner in the used toner cartridge runs out, this toner cartridge is removed. It can be removed from the main body of the image forming apparatus and another new toner cartridge can be mounted. Further, a cartridge equipped with all of the electrophotographic photosensitive member 1, the charging device 2, and toner may be used.

  The exposure device 3 can perform any exposure (image exposure) on the positively charged electrophotographic photoreceptor 1 to form an electrostatic latent image on the photosensitive surface of the positively charged electrophotographic photoreceptor 1. There is no particular limitation on the type. Specific examples include halogen lamps, fluorescent lamps, lasers such as semiconductor lasers and He—Ne lasers, and LEDs (light emitting diodes). Further, exposure may be performed by a photoreceptor internal exposure method. The light at the time of exposure is arbitrary, but generally monochromatic light is preferable. For example, monochromatic light having a wavelength (exposure wavelength) of 700 nm to 850 nm, monochromatic light having a wavelength of 600 nm to 700 nm and slightly shorter wavelength, wavelength of 300 nm to 500 nm The exposure may be performed with a short wavelength monochromatic light or the like.

  The developing roller 44 is disposed between the electrophotographic photosensitive member 1 and the supply roller 43, and is in contact with the positively charged electrophotographic photosensitive member 1 and the supply roller 43. However, the developing roller 44 and the electrophotographic photosensitive member 1 may not be in contact with each other but may be close to each other. The supply roller 43 and the developing roller 44 are rotated by a rotation drive mechanism (not shown). The supply roller 43 carries the stored toner T and supplies it to the developing roller 44. The developing roller 44 carries the toner T supplied by the supply roller 43 and contacts the surface of the electrophotographic photosensitive member 1.

  The regulating member 45 is formed of a resin blade such as a silicone resin or a urethane resin, a metal blade such as stainless steel, aluminum, copper, brass, phosphor bronze, or a blade obtained by coating such a metal blade with a resin. This regulating member 45 normally abuts on the developing roller 44 and is pressed against the developing roller 44 side with a predetermined force by a spring or the like (general blade linear pressure is 0.05 N / cm to 5 N / cm). If necessary, this regulating member 45 may be provided with a function of charging the toner T by friction with the toner T.

  The agitator 42 is provided as necessary, and is rotated by a rotation driving mechanism, and agitates the toner T and conveys the toner T to the supply roller 43 side. A plurality of agitators 42 may be provided with different blade shapes and sizes.

  The type of the toner T is arbitrary, and besides the pulverization method, a polymerized toner by a suspension polymerization method, an emulsion polymerization method, or the like can be used. In particular, when a polymerized toner is used, a toner having a small particle diameter of about 4 μm to 8 μm is preferable, and the toner particle shape varies from a nearly spherical shape to a potato-like shape. Can be used. The polymerized toner is excellent in charge uniformity and transferability, and is preferably used when high image quality is required. Among them, the average circularity of the toner to be used is preferably 0.95 or more, more preferably 0.96 or more, and still more preferably 0.98 or more.

<Measuring method and definition of average circularity>
The “average circularity” in the present invention is measured as follows and is defined as follows. That is, the toner base particles are dispersed in a dispersion medium (Isoton II, manufactured by Beckman Coulter, Inc.) so as to be in the range of 5720 to 7140 particles / μL. (Manufactured by FPIA 2100), measurement is performed under the following apparatus conditions, and the value is defined as “average circularity”. In the present invention, the same measurement is performed three times, and an arithmetic average value of three “average circularity” is adopted as the “average circularity”.
・ Mode: HPF
-HPF analysis amount: 0.35 μL
-HPF detection number: 2000-2500

The following is measured by the above device and automatically calculated and displayed in the above device, and “circularity” is defined by the following formula.
[Circularity] = [Perimeter of a circle with the same area as the projected particle area] / [Perimeter of projected particle image]
And 2000-2500 which is the number of HPF detection is measured, and the arithmetic average (arithmetic mean) of the circularity of each individual particle is displayed on the apparatus as “average circularity”.

  The type of the transfer device 5 is not particularly limited, and an apparatus using an arbitrary system such as an electrostatic transfer method such as corona transfer, roller transfer, or belt transfer, a pressure transfer method, or an adhesive transfer method can be used. . In FIG. 1, it is assumed that the transfer device 5 includes a transfer charger, a transfer roller, a transfer belt, and the like disposed so as to face the electrophotographic photosensitive member 1. The transfer device 5 applies a predetermined voltage value (transfer voltage) having a polarity opposite to the charging potential of the toner T, and transfers a toner image formed on the electrophotographic photosensitive member 1 to a recording paper (paper, medium, transfer target). Transfer to P.

  There is no restriction | limiting in particular about the cleaning apparatus 6, Arbitrary cleaning apparatuses, such as a brush cleaner, a magnetic brush cleaner, an electrostatic brush cleaner, a magnetic roller cleaner, a blade cleaner, can be used. The cleaning device 6 is for scraping off residual toner adhering to the photoreceptor 1 with a cleaning member and collecting the residual toner. However, when there is little or almost no toner remaining on the surface of the photoreceptor, the cleaning device 6 may be omitted.

  The fixing device 7 includes an upper fixing member (fixing roller) 71 and a lower fixing member (fixing roller) 72, and a heating device 73 is provided inside the fixing member 71 or 72. FIG. 1 shows an example in which a heating device 73 is provided inside the upper fixing member 71. As the upper and lower fixing members 71 and 72, known heat such as a fixing roll in which a metal base tube such as stainless steel or aluminum is coated with silicone rubber, a fixing roll in which Teflon (registered trademark) resin is coated, or a fixing sheet is used. A fixing member can be used. Further, the fixing members 71 and 72 may be configured to supply a release agent such as silicone oil in order to improve the releasability, or may be configured to forcibly apply pressure to each other by a spring or the like.

  The toner transferred onto the recording sheet P is heated to a molten state when passing between the upper fixing member 71 and the lower fixing member 72 heated to a predetermined temperature. Then, the toner is fixed on the recording paper P after being cooled.

  The type of the fixing device is not particularly limited, and a fixing device of an arbitrary system such as heat roller fixing, flash fixing, oven fixing, pressure fixing, or the like can be provided.

  The image forming method of the present invention comprises a charging step for positively charging the positively charged electrophotographic photosensitive member of the present invention, and exposing the charged positively charged electrophotographic photosensitive member to form an electrostatic latent image. An exposure process, a developing process for developing the electrostatic latent image with toner, and a transfer process for transferring the toner to a transfer medium. That is, first, the surface (photosensitive surface) of the photoreceptor 1 is charged to a predetermined positive potential (for example, +600 V) by the charging device 2 (charging process). At this time, charging may be performed by a DC voltage, or charging may be performed by superimposing an AC voltage on the DC voltage.

  Subsequently, the photosensitive member is exposed to form an electrostatic latent image (exposure process). That is, the photosensitive surface of the charged photoreceptor 1 is exposed by the exposure device 3 according to the image to be recorded, and an electrostatic latent image is formed on the photosensitive surface.

  The toner image is transferred to the recording paper P by the transfer device 5 (transfer process). Thereafter, the toner remaining on the photosensitive surface of the photoreceptor 1 without being transferred is removed by the cleaning device 6.

  After the transfer of the toner image onto the recording paper P, the final image is obtained by passing the fixing device 7 and thermally fixing the toner image onto the recording paper P.

  Note that the image forming apparatus of the present invention may have a configuration capable of performing, for example, a static elimination process in addition to the above-described configuration. The charge eliminating step is a step of discharging the electrophotographic photosensitive member by exposing the electrophotographic photosensitive member. A fluorescent lamp, LED, etc. are used as a static elimination apparatus. In addition, the light used in the static elimination process is often light having an exposure energy that is at least three times that of the exposure light.

<Electrophotographic photosensitive member cartridge>
The positively charged photosensitive member 1 can be configured as an electrophotographic photosensitive member cartridge in combination with the charging device 2 as described above, as well as an exposure device 3, a developing device 4, a transfer device 5, a cleaning device 6, and In combination with one or more selected from the group consisting of the fixing device 7, an integrated cartridge (electrophotographic photosensitive member cartridge) can also be configured. The electrophotographic photosensitive member cartridge is configured to be detachable from an electrophotographic apparatus main body such as a copying machine or a laser beam printer. The photosensitive member 1 is preferably combined with at least one selected from the group consisting of a charging device 2, an exposure device 3, a developing device 4 and a transfer device 5 to form an integral cartridge. Also in this case, similarly to the cartridge described in the above embodiment, when the electrophotographic photosensitive member 1 and other members deteriorate, for example, the electrophotographic photosensitive member cartridge is removed from the main body of the image forming apparatus, and another new electrophotographic image is obtained. By attaching the photosensitive cartridge to the image forming apparatus main body, maintenance and management of the image forming apparatus are facilitated.

  Hereinafter, the embodiment of the present invention will be described more specifically with reference to examples. The description of “parts” in the following production examples, examples and comparative examples indicates “parts by mass” unless otherwise specified. Moreover, the electron transport substance used in the following examples can be synthesized based on, for example, the method described in JP-A No. 5-210253.

<Manufacture of photoreceptor sheet>
(Photoreceptor Production Example 1 (P-1))
First, the coating solution for forming the undercoat layer prepared as described below was applied to a polyethylene terephthalate sheet with aluminum deposited on the surface with a wire bar so that the film thickness after drying was about 0.3 μm, and dried. An undercoat layer was provided.

  A method for adjusting the coating solution for forming the undercoat layer will be described. 10 parts of Y-type oxytitanium phthalocyanine showing a strong diffraction peak with a Bragg angle (2θ ± 0.2) of 27.3 ° in X-ray diffraction using CuKα rays was added to 150 parts of 1,2-dimethoxyethane, The mixture was pulverized and dispersed for 1 hour to prepare a pigment dispersion. Next, 10 parts of polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name Denkabutyral # 6000C) was dissolved in 100 parts of 1,2-dimethoxyethane to prepare a binder solution. 160 parts of the pigment dispersion is mixed with 100 parts of the binder solution, an appropriate amount of 1,2-dimethoxyethane is added, and finally a coating liquid for forming an undercoat layer (dispersion) with a solid content concentration of 4.0% is obtained. Prepared.

  A method for forming a monolayer type photosensitive layer will be described. First, oxytitanium phthalocyanine (CG-1) 4 having a strong diffraction peak at 27.3 ° in the Bragg angle (2θ ± 0.2) in X-ray diffraction by CuKα ray and having a powder X-ray diffraction spectrum shown in FIG. Part and 100 parts of toluene were dispersed by a sand grind mill to prepare a pigment dispersion. In addition, 70 parts of the hole transport material represented by the structural formula (C-1), 16 parts of the electron transport material represented by the structural formula (A-1), and the following structural formula (B-1) 100 parts of a binder resin (m: n = 51: 49, viscosity average molecular weight 30,000) and 8 parts of an antioxidant (trade name: IRGANOX1076, manufactured by Ciba Specialty Chemicals) are dissolved in 500 parts of tetrahydrofuran. Furthermore, 0.05 part of silicone oil (manufactured by Shin-Etsu Silicone Co., Ltd .: trade name KF96) was added as a leveling agent. Then, the above-mentioned pigment dispersion was added thereto, and mixed uniformly by a homogenizer to prepare a single-layer type photosensitive layer forming coating solution. This coating solution was applied onto the above undercoat layer so that the film thickness after drying was 25 μm, to obtain a positively charged single layer type electrophotographic photosensitive member P-1.

(Photoreceptor Production Example 2 (P-2))
Photoconductor P-2 was obtained in the same manner as in Photoconductor Production Example 1 except that C-12 was used instead of C-1 as the hole transport material.

(Photoreceptor Production Example 3 (P-3))
As the binder resin, in the same manner as in Photoconductor Production Example 2 except that instead of B-1, a binder resin (viscosity average molecular weight 40,000) having only the monomer unit represented by B-2 below as a repeating unit was used. Thus, a photoreceptor P-3 was obtained.

(Photoreceptor Production Example 4 (P-4))
Photoreceptor production except that instead of B-1, a binder resin having a monomer unit represented by B-3 below (viscosity average molecular weight 35,000, m: n = 20: 80) was used as the binder resin. In the same manner as in Example 2, a photoreceptor P-4 was obtained.

(Photoreceptor Production Example 5 (P-5))
Photoconductor production, except that instead of B-1, a binder resin having a monomer unit represented by B-4 below (viscosity average molecular weight 30,000, m: n = 90: 10) was used as the binder resin. In the same manner as in Example 2, a photoreceptor P-5 was obtained.

(Photoreceptor Production Example 6 (P-6))
In the same manner as in Photoconductor Production Example 2, except that a binder resin having a monomer unit represented by B-5 below (viscosity average molecular weight 40,000) was used instead of B-1 as the binder resin. Body P-6 was obtained.

(Photoreceptor Production Example 7 (P-7))
In the same manner as in Photoconductor Production Example 2, except that a binder resin (viscosity average molecular weight 43,000) having a monomer unit represented by B-6 below was used instead of B-1, as the binder resin. Body P-7 was obtained.

(Photoreceptor Production Examples 8 to 17 (P-8 to P-17))
As an electron transport material, instead of A-1, A-2, A-3, A-6, A-11, A-15, A-16, A-25, A-26, A-27, A- Photoreceptors P-8 to P-17 were produced in the same manner as Photoreceptor Production Example 1 except that No. 31 was used.

(Photoreceptor Production Example 18 (P-18))
As hole transport material, in place of 70 parts of (C-1), 35 parts of (C-1) and 35 parts of (C-2) were mixed and used, as in Photoconductor Production Example 1. In this manner, a photoreceptor P-18 was obtained.

(Photoreceptor Production Example 19 (P-19))
As hole transport material, in the same manner as in Photoconductor Production Example 1 except that (C-1) 70 parts instead of (C-1) 70 parts, (C-6) 50 parts and (C-13) 10 parts were mixed and used. In this manner, a photoreceptor P-19 was obtained.

(Photoreceptor Production Examples 20 to 26 (P-20 to P-26))
Photoconductor production examples except that C-16, C-18, C-19, C-20, C-22, C-24, and C-26 were used as the hole transport material instead of C-1. In the same manner as in Example 1, photoreceptors P-20 to P-26 were obtained.

(Photoreceptor Production Example 27 (P-27))
In place of oxytitanium phthalocyanine (CG-1) in the single-layer type photosensitive layer, Photoreceptor P-27 was prepared in the same manner as Photoreceptor Production Example 1 except that an azo pigment (CG-2) having the following structural formula was used. Obtained.

(Photoreceptor Production Example 28 (P-28))
In place of oxytitanium phthalocyanine (CG-1) in the single-layer type photosensitive layer, photoconductor P-28 was prepared in the same manner as in photoconductor production example 1 except that an azo pigment (CG-3) having the following structural formula was used. Obtained.

(Photoreceptor Production Example 29 (P-29))
In place of oxytitanium phthalocyanine (CG-1) in the single layer type photosensitive layer, an azo pigment (CG-4) having the following structural formula was used, and the photoreceptor P-29 was prepared in the same manner as in photoreceptor production example 1. Obtained.

(Photoreceptor Production Example 30 (P-30))
Photoreceptor P-30 was obtained in the same manner as in Photoreceptor Production Example 1 except that τ-type metal-free phthalocyanine (CG-5) was used instead of oxytitanium phthalocyanine (CG-1) in the single-layer type photosensitive layer. .

(Comparative Photoconductor Production Example 1 (AP-1))
Comparative photoconductor AP-1 was prepared in the same manner as in Photoconductor Production Example 1 except that E-1 below was used instead of A-1 as the electron transport material.

(Comparative Photoconductor Production Example 2 (AP-2))
Comparative photoconductor AP-2 was prepared in the same manner as in Photoconductor Production Example 1 except that E-2 below was used instead of A-1 as the electron transport material.

(Comparative Photoconductor Production Example 3 (AP-3))
An undercoat layer was formed in the same manner as in Photoconductor Production Example 1, and a monolayer type photosensitive layer was formed thereon as described below to produce a photoconductor.

In X-ray diffraction by CuKα ray, a Bragg angle (2θ ± 0.2) shows a strong diffraction peak at 27.3 °, and 4 parts of oxytitanium phthalocyanine having a powder X-ray diffraction spectrum shown in FIG. The dispersion was prepared by dispersing with a grind mill. Similarly, 8 parts of an electron transport material represented by the following structural formula (E-3) and 112 parts of toluene were dispersed by a sand grind mill to prepare a dispersion.
Also, 70 parts of the hole transport material represented by the structural formula (C-1) and the binder resin represented by the structural formula (B-1) (m: n = 51: 49, viscosity average molecular weight 30, 000) 100 parts and 8 parts of an antioxidant (trade name: IRGANOX 1076, manufactured by Ciba Specialty Chemicals) dissolved in 400 parts of tetrahydrofuran, and a silicone oil as a leveling agent (trade name: KF96) 0.05 The two pigment dispersions described above were further added thereto, and mixed with a homogenizer so as to be uniform. The coating solution prepared in this manner was applied on the undercoat layer so that the film thickness after drying was 25 μm, thereby preparing a comparative photoreceptor AP-3.

(Comparative Photoconductor Production Example 4 (AP-4))
A laminated photosensitive layer was formed as follows.
First, a charge generation layer was formed. 10 parts of Y-type oxytitanium phthalocyanine showing a strong diffraction peak with a Bragg angle (2θ ± 0.2) of 27.3 ° in X-ray diffraction using CuKα rays was added to 150 parts of 1,2-dimethoxyethane, The mixture was pulverized and dispersed for 1 hour to prepare a pigment dispersion. Next, 10 parts of polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name Denkabutyral # 6000C) was dissolved in 100 parts of 1,2-dimethoxyethane to prepare a binder solution. Then, 160 parts of the pigment dispersion was mixed with 100 parts of the binder solution, and an appropriate amount of 1,2-dimethoxyethane was added to finally prepare a dispersion having a solid concentration of 4.0% by mass.

  The charge generation layer forming coating solution obtained in this way is applied to a polyethylene terephthalate sheet with aluminum deposited on the surface so that the film thickness after drying is about 0.3 μm and dried to generate charge. A layer was provided.

  Next, a charge transport layer was formed. 40 parts of electron transport material A-1, 100 parts of binder resin B-2, and 500 parts of dichloroethane are dissolved, and coated on the charge generation layer and dried so that the film thickness after drying is 25 μm. Photoconductor AP-4 was produced.

<Evaluation of photoreceptor>
The produced photoreceptor sheets P-1 to P-30 and AP-1 to AP-4 were subjected to the following electrical property test and wear test. The results of the electrical property test are summarized in Table 3, and the results of the wear test are summarized in Table 4.

<Electrical property test 1>
An electrophotographic characteristic evaluation apparatus manufactured according to the electrophotographic society measurement standard (basic and applied electrophotographic technology, edited by the Electrophotographic Society, Corona, pages 404 to 405) is used, and the photosensitive sheet is 80 mm in diameter. Attached to an aluminum drum to form a cylindrical shape, the aluminum drum and the aluminum base of the photosensitive sheet are electrically connected, and then the drum is rotated at a constant rotational speed of 60 rpm to perform charging, exposure, potential measurement, and static elimination cycle. An electrical property evaluation test was conducted. At that time, the surface potential after exposure (when the initial surface potential of the photosensitive member is charged to +700 V and the light of the halogen lamp is changed to 780 nm monochromatic light with an interference filter at 1.5 μJ / cm ² is exposed. Hereinafter referred to as VL1). In the VL1 measurement, the time required from the exposure to the potential measurement was 100 ms. The measurement environment was a temperature of 25 ° C. and a relative humidity of 50%. Table 3 shows the measurement results.

<Electrical property test 2>
An electrophotographic characteristic evaluation apparatus manufactured according to the electrophotographic society measurement standard (basic and applied electrophotographic technology, edited by the Electrophotographic Society, Corona, pages 404 to 405) is used, and the photosensitive sheet is 80 mm in diameter. Attached to an aluminum drum to form a cylindrical shape, the aluminum drum and the aluminum base of the photosensitive sheet are electrically connected, and then the drum is rotated at a constant rotational speed of 60 rpm to perform charging, exposure, potential measurement, and static elimination cycle. An electrical property evaluation test was conducted. At that time, the surface potential after exposure when the initial surface potential of the photosensitive member is charged to +700 V and the light of the halogen lamp is changed to monochromatic light of 405 nm by an interference filter at 2.0 μJ / cm ² ( Hereinafter, this is referred to as VL2. In the VL2 measurement, the time required from the exposure to the potential measurement was 100 ms. The measurement environment was a temperature of 25 ° C. and a relative humidity of 50%. Table 3 shows the measurement results.

表３中のＶＬ１およびＶＬ２は、低い方が好ましい。また、「光減衰なし」は、露光による帯電量の低下が観察されなかったことを意味する。

VL1 and VL2 in Table 3 are preferably lower. Further, “no light attenuation” means that no decrease in charge amount due to exposure was observed.

<Friction test>
A photosensitive sheet is set on a dynamic friction and wear tester (manufactured by Kyowa Interface Chemical Co., Ltd., DFPM-SS), and toner (Hulette Packard Co., LaserJet 4 toner) is 0.1 mg / cm ² on the photosensitive member surface. After evenly placed, a urethane rubber cleaning blade (manufactured by Sharp, SF-7800 cleaning blade cut to 1 cm width) is applied to the sample at an angle of 45 degrees, weight 200 g, speed 5 mm / second, stroke 20 mm The dynamic friction coefficient of the photoconductor when the blade was moved was measured. Table 4 shows the measurement results of the dynamic friction coefficient when this measurement was repeated 100 times.

  Table 4 shows that the dynamic friction coefficients of the photoconductors P1 to P7 of the present invention are smaller than those of the photoconductor AP-4 of the comparative example, and the photoconductor of the present invention has a good matching with the cleaning blade. .

<Image test 1>
Using an undercoat layer (adhesive layer) coating solution prepared in Photoconductor Production Example 1 on an aluminum tube having a diameter of 3 cm and a length of 24.7 cm cut, the film thickness after drying is 0. An undercoat layer was formed by dip coating and drying to a thickness of 3 μm. On top of this, a coating solution for a single layer type photoreceptor produced in the same manner as in photoreceptor production example 1 was applied by a dip coating method to produce an electrophotographic photosensitive drum having a dried photosensitive layer thickness of 25 μm. When this drum was mounted on a drum cartridge of a monochrome laser printer HL1240 manufactured by Brother Industries, and an image test was performed, a good image free from image defects and noise was obtained. Subsequently, 20,000 sheets were continuously printed, but no image deterioration such as ghost and fog was observed, and a stable image was formed.

  When the shape of the toner used in the printer was analyzed by a flow type particle image analyzer FPIA-2000 manufactured by Sysmex Corporation, the 50% circularity was 1.00. Further, when particle size analysis was performed using a precision particle size distribution measuring device Coulter Counter Multisizer 3 manufactured by Beckman Coulter, the volume average particle size (Dv) was 9.1 μm, and the number average particle size (DN). Was 7.7 μm and Dv / DN was 1.19. As described above, since the present toner has a true spherical shape and a uniform particle size, it can be understood that the toner is a toner produced by a suspension polymerization method.

<Image test 2>
An electrophotographic photosensitive drum was produced in the same manner as in the image test 1 except that the aluminum tube was changed to a non-cutting one having a diameter of 2.4 cm and a length of 24.5 cm. When this drum was mounted on a drum cartridge of a tandem color type laser printer HL4040 manufactured by Brother Industries, an image test was performed, and a good image free from image defects and noise was obtained in any color. Subsequently, 20,000 sheets were continuously printed, but no image deterioration such as ghost and fog was observed, and a stable image was formed.

<Image test 3>
An image test was conducted in the same manner as the image test 2 except that the single-layer type photosensitive layer was changed to the AP-3. The potential of the exposed portion did not drop sufficiently, and the image density was low from the beginning, and a positive ghost was generated after printing 5000 sheets.

<Image test 4>
An image test was carried out in the same manner as the image test 1 except that the photosensitive layer was changed to the above-mentioned laminated AP-4. It was confirmed that the image density was low from the beginning without the potential of the exposed part being sufficiently lowered, and the fine black spots and thin lines were blurred.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. Rather, it can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification, and a positively charged electrophotographic photosensitive member with such a change, and an electrophotographic apparatus having the photosensitive member It should be understood that the photoreceptor cartridge and the image forming apparatus, and the image forming method are also included in the technical scope of the present invention.

1 is a schematic diagram illustrating a main configuration of an embodiment of an image forming apparatus including an electrophotographic photosensitive member of the present invention. X-ray powder diffraction spectrum of oxytitanium phthalocyanine contained in the single-layer type photosensitive layer of photoreceptor production example 1 of the present invention

Explanation of symbols

1 Photoconductor 2 Charging device (charging roller)
DESCRIPTION OF SYMBOLS 3 Exposure apparatus 4 Developing apparatus 5 Transfer apparatus 6 Cleaning apparatus 7 Fixing apparatus 41 Developing tank 42 Agitator 43 Supply roller 44 Developing roller 45 Control member 71 Upper fixing member (pressure roller)
72 Lower fixing member (fixing roller)
73 Heating device T Toner P Recording paper (paper, medium)

Claims (12)

An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer contains at least a binder resin, a charge generation material, an electron transport material, and a hole transport material in the same layer. An electrophotographic photoreceptor, wherein the electron transport material is one or more compounds selected from compounds represented by the following formulas (1) to (3).

(In the formulas (1) to (3), R ¹ represents a substituent having a prescribed substitution number σ _p based on Hammett's rule of 0.450 or more, and Y represents an optionally substituted carbon number of 4 or more. Represents an alicyclic structure of 8 or less, Z represents an optionally substituted cyclic structure having a molecular weight of 400 or less, and M ¹ represents a linking group having a molecular weight of 300 or less.) The electrophotographic photoreceptor according to claim 1, wherein the electron transport material is one or more compounds selected from compounds represented by the following formulas (4) to (6).

[In the formulas (4) to (6), R ² represents a substituent whose substitution prescribed number σ _p based on Hammett's rule is 0.450 or more, and R ^{3 to} R ⁵ may be the same or different organic groups. M ² represents a linking group having a molecular weight of 300 or less, X represents any of the following (X1) to (X3),

(In formula (X2), R ⁶ and R ⁷ may be the same or different and each represents a substituent having a prescribed substitution number σ _p based on Hammett's rule of 0.450 or more.)

N represents an integer of 0 to 4. ] The electrophotographic photosensitive member according to claim 1, wherein the hole transport material is a compound represented by the following formula (7).

(In Formula (7), Ar ^{1 to} Ar ⁶ represent an aromatic residue that may have a substituent or an aliphatic residue that may have a substituent, and X ′ represents an organic residue. represents, ^{R 1} '~R ^4' represents an organic group, n1 to n6 represents an integer of 0 to 2.) The binder resin contains a polycarbonate resin containing a monomer unit derived from an aromatic diol component represented by the following formula (8) and / or a polyarylate resin. The electrophotographic photosensitive member described.

(In the formula (8), L represents the following (L1) to (L5)

(In formula (L1), R ⁵ ′ and R ⁶ ′ represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group, or a halogenated alkyl group.)

Alternatively, it represents a single bond, and Y ^{1 to} Y ⁸ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group, or a halogenated alkyl group. ) The electrophotographic photosensitive member according to claim 4, wherein the aromatic diol component represented by the formula (8) is one excluding the case where R ₅ ′ and R ₆ ′ are bonded to each other to form a ring structure. The electrophotographic photosensitive member according to claim 1, wherein monochromatic light having an exposure wavelength in the range of 380 nm to 500 nm is used. The electrophotographic photosensitive member according to claim 1, which is a positively charged type photosensitive member. An electrophotographic photosensitive member cartridge comprising the electrophotographic photosensitive member according to claim 1 and a charging device that positively charges the electrophotographic photosensitive member. An electrophotographic photosensitive member according to any one of claims 1 to 7, a charging device for positively charging the electrophotographic photosensitive member, and exposing the charged electrophotographic photosensitive member to form an electrostatic latent image. An image forming apparatus comprising: an exposure device; a developing device that develops the electrostatic latent image with toner; and a transfer device that transfers the toner to a transfer target. The image forming apparatus according to claim 9, wherein the toner is a toner having an average circularity of 0.95 or more. A charging step for positively charging the electrophotographic photosensitive member according to any one of claims 1 to 7, an exposure step for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image, An image forming method comprising: a developing step of developing an image with toner; and a transferring step of transferring the toner to a transfer target. The image forming method according to claim 11, wherein the toner is a toner having an average circularity of 0.95 or more.

Images