JP5040319B2 - Positively charged electrophotographic photosensitive member, image forming apparatus, image forming method, and electrophotographic photosensitive member cartridge - Google Patents

Description

  The present invention relates to a positively charged electrophotographic photosensitive member, an image forming apparatus, an image forming method, and an electrophotographic photosensitive member cartridge used for a copying machine, a printer, and the like. More specifically, the present invention relates to a positively charged electrophotographic photoreceptor excellent in wear resistance and electrical characteristics, and to an image forming apparatus, an image forming method, and an electrophotographic photoreceptor cartridge using the same.

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 photoreceptors, so-called function-separated photoreceptors that share charge carrier generation and transfer functions with different compounds have a large room for material selection, making it easy to control the characteristics of the photoreceptor. Therefore, it has become the mainstream of development. Further, from the viewpoint of the layer configuration, a single layer type photoreceptor having a charge generating agent and a charge transporting agent in the same layer, and a laminate in which they are separated and stacked in separate layers (charge generating layer and charge transporting layer) Type photoreceptors are known.

  Of these, the laminated type photoreceptors are of this type because most of the current photoreceptors are of this type because the functions of each layer can be easily optimized and the characteristics can be easily controlled. Most of such laminated photoreceptors have at least a charge generation layer and a charge transport layer in this order on a substrate.

  In the charge transport layer, there are very few suitable electron transport materials, whereas many hole transport materials having a good characteristic are known. For this reason, in a laminated photoreceptor using such a hole transport material, a negative charging method is adopted for charging. In such a 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, when using a single layer type positively charged photoconductor, it is considered to be one of the advantages to reduce such ozone generation. Although many are inferior, some have been put into practical use. In addition to the effect on the generation of ozone, the single-layer type photosensitive member has advantages such as fewer coating steps and hardly causing interference fringes with semiconductor laser light.

  Furthermore, in addition to the advantages described above, in the 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 is almost negligible. Furthermore, 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, image blur due to diffusion of light and charge carriers is difficult to occur in a single-layer type photoreceptor, and not only high resolution can be expected, but also when the photosensitive layer is made thicker, diffusion of charge and incident light is expected. However, the resolution does not decrease much (Patent Documents 1 to 5).

  By the way, the electrophotographic photosensitive member is repeatedly used in an electrophotographic process, that is, a cycle of charging, exposure, development, transfer, cleaning, static elimination, and the like, and is deteriorated by various stresses during that time. Such deterioration includes, for example, strong oxidizing ozone and NOx generated from the corona charger used as a charger as described above, which causes chemical damage to the photosensitive layer, or is generated by image exposure or static elimination light. Examples of such chemical and electrical degradation include the fact that the exposed carrier flows in the photosensitive layer and the photosensitive layer composition is decomposed by light from the outside.

  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, and film peeling. 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 the case of a general photoreceptor having no functional layer such as a surface protective layer, it is the photosensitive layer that receives such a load. The photosensitive layer is usually composed of a binder resin and a photoconductive substance, and the binder resin substantially determines the strength. However, since the doping amount of the photoconductive substance is considerably large, the conventional technique has not yet provided sufficient mechanical strength.

  In addition, due to the increasing demand for high-speed printing, materials for a higher-speed electrophotographic process are required. 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 governed by the charge transport layer, particularly the charge transport material, but varies greatly depending on the binder resin.

  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 resins, and various kinds of heat. A curable resin is used. Among the various binder resins, the polycarbonate resin has a relatively excellent performance, and various polycarbonate resins have been developed and put into practical use (see, for example, Patent Documents 6 to 9).

On the other hand, a technique of an electrophotographic photoreceptor using a polyarylate resin marketed as a trade name “U-polymer” as a binder is disclosed, and among them, it is shown that sensitivity is particularly excellent as compared with polycarbonate. (For example, see Patent Document 10).
Also disclosed is a technique for an electrophotographic photoreceptor using a polyarylate resin using a dihydric phenol component having a specific structure as a binder resin, improving the solution stability during the production of the photoreceptor, mechanical strength, It is known that the wear resistance is excellent (see, for example, Patent Documents 11 and 12).

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 JP-A-56-135844 Japanese Patent Laid-Open No. 3-6567 Japanese Patent Laid-Open No. 10-288845

Conventional photoreceptors have problems such as surface wear due to practical loads such as development with toner, friction with a transfer member or paper, friction with a cleaning member (blade), and scratches on the surface. . For this reason, the present situation is that the printing performance is limited in practical use.
In addition, the electrophotographic photosensitive member using the conventionally known polyester resin is improved in strength and the like, but has poor stability when used as a coating solution for forming a photosensitive layer, becomes cloudy, precipitates, or insolubilizes. There are issues such as. In particular, the positively charged photoreceptor has a problem that the wear resistance is greatly reduced because it contains not only the charge transport material but also the charge generating material together with the binder resin.

  The present invention has been made to solve such problems. That is, an object of the present invention is to provide a positively charged electrophotographic photosensitive member in which a coating solution for forming a photosensitive layer is stable, has excellent wear resistance with respect to practical load, and has good electrical characteristics. It is an object of the present invention to provide an image forming apparatus, an image forming method, and an electrophotographic photosensitive member cartridge.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have included a polyester resin having a specific structure in a single-layer type photosensitive layer, thereby having sufficient mechanical characteristics and good electrical properties. It has been found that it exhibits characteristics, and the present invention has been completed.

（式（２）中、Ａｒ⁵〜Ａｒ⁸は、それぞれ独立に置換基を有していてもよいフェニレン基を表わし、Ｒ¹は水素原子またはメチル基を表わす。）
ただし、該単層型感光層が、ポリ三フッ化エチレンおよびパーフルオロポリエーテルのいずれか一種またはそれらの混合物を含有する場合を除く。 That is, the gist of the present invention is a positively charged electrophotographic photosensitive member having a single layer type photosensitive layer on a conductive support, wherein the single layer type photosensitive layer is represented by the following formula (2). The present invention resides in a positively charged electrophotographic photosensitive member characterized by containing a polyester resin containing

(In Formula (2), Ar ^{5 to} Ar ⁸ each independently represent a phenylene group which may have a substituent, and R ¹ represents a hydrogen atom or a methyl group.)
However, the case where the single-layer type photosensitive layer contains any one of polytrifluoroethylene and perfluoropolyether or a mixture thereof is excluded.

Further, positive charging type electrophotographic photoconductor of the is preferably intended to be used with monochromatic writing light of wavelength 380 to 500 nm (claim 2).

Another gist of the present invention is that the positively charged electrophotographic photosensitive member, a charging means for positively charging the electrophotographic photosensitive member, and exposing the charged electrophotographic photosensitive member to form an electrostatic latent image. and forming exposure unit, a developing unit for developing the electrostatic latent image with toner, characterized by comprising a transfer means for transferring the toner to a transfer object, resides in an image forming apparatus (claim 3) .

At this time, the exposure means, which performs exposure by monochromatic light 380nm~500nm the exposure wavelength is preferably (claim 4).

Still another subject matter of the present invention is an image forming method for forming an image using the positively chargeable electrophotographic photosensitive member, wherein the positively charged electrophotographic photosensitive member is charged positively; An exposure process for exposing the formed electrophotographic photosensitive member to form an electrostatic latent image, a developing process for developing the electrostatic latent image with toner, and a transfer process for transferring the toner to a transfer target. The present invention resides in an image forming method (claim 5 ).

Still another subject matter of the present invention lies in an electrophotographic photosensitive member cartridge comprising the positively charged electrophotographic photosensitive member and charging means for positively charging the electrophotographic photosensitive member (claim). Item 6 ).

  According to the present invention, a positively charged electrophotographic photoreceptor having a stable coating solution for forming a photosensitive layer and having excellent wear resistance and electrical characteristics, and an image forming apparatus, an image forming method, and an electrophotographic photosensitive member using the same. A body cartridge can be obtained.

  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.

（式（１）中、Ａｒ¹〜Ａｒ⁴は、それぞれ独立に、置換基を有していてもよいアリーレン基を表わし、Ｘ¹は単結合または二価基を表わす。） [I. Polyester resin of the present invention]
The polyester resin of the present invention is a polyester resin containing a repeating structure represented by the following formula (1).

(In formula (1), Ar ^{1 to} Ar ⁴ each independently represents an arylene group which may have a substituent, and X ¹ represents a single bond or a divalent group.)

Details will be described below.
In the formula (1), Ar ^{1 to} Ar ⁴ each independently represents an arylene group.
The carbon number of Ar ^{1 to} Ar ⁴ is arbitrary as long as the effects of the present invention are not significantly impaired. However, the carbon number of Ar ¹ and Ar ² is usually 6 or more, usually 20 or less, preferably 12 or less, particularly preferably 7. Ar ³ and Ar ⁴ usually have 6 or more carbon atoms, usually 20 or less, preferably 12 or less, and particularly preferably 6.

The number of rings Ar ^{1 to} Ar ⁴ is arbitrary as long as the effects of the present invention are not significantly impaired, but is usually 1 or more, usually 3 or less, preferably 2 or less, and particularly preferably 1.
Specific examples of Ar ^{1 to} Ar ⁴ include a phenylene group, a naphthylene group, a 3-methylphenylene group, and a 3-phenylphenylene group. In addition, examples include an anthrylene group, a phenanthrylene group, a pyrenylene group, and the like. Among these, a phenylene group and a naphthylene group are particularly preferable from the viewpoint of production cost. Further, when a phenylene group and a naphthylene group are compared, a phenylene group is more preferable in terms of ease of synthesis in addition to manufacturing cost.

Moreover, the arylene group which comprises Ar < ¹ > -Ar < ⁴ > may have a substituent each independently. Specific examples of the substituent include an alkyl group, an aryl group, a halogen group, an alkoxy group, and a condensed polycyclic group. Of these, considering the mechanical properties as a binder resin for the photosensitive layer and the solubility in the coating solution for forming the photosensitive layer, the aryl group is preferably a phenyl group, a naphthyl group, etc., and the halogen group is a fluorine atom, chlorine An atom, a bromine atom, an iodine atom and the like are preferable, and examples of the alkoxy group include a methoxy group, an ethoxy group and a butoxy group. In addition, when the substituent is an alkyl group, the carbon number of the alkyl group is usually 1 or more, and usually 10 or less, preferably 8 or less, more preferably 2 or less, and specifically, a methyl group is particularly preferred. . Moreover, there is no restriction | limiting in particular in the number of each substituent of Ar < ¹ > -Ar < ⁴ >, Preferably it is 3 or less, It is more preferable that it is 2 or less, It is especially preferable that it is 1 or less.

Further, in the formula (1), when Ar ¹ and Ar ² have a substituent, Ar ¹ and Ar ² are preferably the same arylene group having the same substituent, and phenylene having a methyl group as a substituent. More preferably, it is a group. Ar ³ and Ar ⁴ are preferably the same arylene group, and particularly preferably a phenylene group having no substituent.

In the formula (1), X ¹ represents a single bond or a divalent group. Preferable examples of X ¹ include a sulfur atom, an oxygen atom, a sulfonyl group, a cycloalkylene group, —CR ² R ³ — and the like. Here, R ² and R ³ each independently represent a hydrogen atom, an alkyl group, an aryl group, a halogen group, or an alkoxy group. Of R ² and R ³ , considering the mechanical properties as a binder resin for the photosensitive layer and the solubility in the coating solution for forming the photosensitive layer, the aryl group is preferably a phenyl group, a naphthyl group, As the halogen group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like are preferable, and as the alkoxy group, a methoxy group, an ethoxy group, a butoxy group and the like are preferably exemplified. When R ² or R ³ is an alkyl group, the alkyl group usually has 1 or more carbon atoms, usually 10 or less, preferably 8 or less, more preferably 2 or less.

Furthermore, considering the simplicity of production of the divalent hydroxy compound used for producing the polyester resin of the present invention, examples of preferable groups as X ¹ include —O—, —S—, and —SO—.
_{, -SO 2 -, - CO -} , - CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, include cyclohexylidene. Among these, —CH ₂ —, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ —, and cyclohexylidene are preferable, and —CH ₂ —, —CH (CH ₃ ) —, cyclohexylene are particularly preferable. Den.

（式（３），（４）において、Ａｒ¹〜Ａｒ⁴は、それぞれ独立に、置換基を有していてもよいアリーレン基を表わし、Ｘ¹は単結合または二価基を表わす。） By the way, the repeating structure represented by the above formula (1) is represented by a divalent hydroxy residue (partial structure represented by the following formula (3)) and a dicarboxylic acid residue (the following formula (4)). Partial structure). The structures of these divalent hydroxy residues and dicarboxylic acid residues have various effects on the polyester resin of the present invention. Therefore, it is desirable that the structures of the divalent hydroxy residue and the dicarboxylic acid residue are appropriately preferred.

(In formulas (3) and (4), Ar ^{1 to} Ar ⁴ each independently represent an arylene group which may have a substituent, and X ¹ represents a single bond or a divalent group.)

Hereinafter, preferred structures of the above divalent hydroxy residue and dicarboxylic acid residue will be described.
First, the divalent hydroxy residue is represented by the formula (3). In the formula (3), Ar ¹ , Ar ² and X ¹ are the same as those described in the formula (1).

（式（５）中、Ａｒ⁵、Ａｒ⁶は、それぞれ独立に、置換基を有していてもよいフェニレン基を表わし、Ｒ¹は水素原子またはメチル基を表わす。） Among the divalent hydroxy residues represented by the above formula (3), a divalent phenol residue represented by the following formula (5) is particularly preferable.

(In Formula (5), Ar ⁵ and Ar ⁶ each independently represent a phenylene group which may have a substituent, and R ¹ represents a hydrogen atom or a methyl group.)

In the formula (5), Ar ⁵ and Ar ⁶ each independently represent a phenylene group which may have a substituent. At this time, the substituents of Ar ⁵ and Ar ⁶ are the same as those described above as the substituents of Ar ^{1 to} Ar ⁴ .
In the formula (5), R ¹ represents a hydrogen atom or a methyl group.

Specific examples of the formula (5) include divalent phenol residues having a structure in which a hydrogen atom is removed from the hydroxyl group of the divalent phenol compound exemplified below.
That is, when R ¹ is a hydrogen atom, examples of the dihydric phenol compound corresponding to the dihydric phenol residue represented by the formula (5) include bis (2-hydroxyphenyl) methane, (2-hydroxyphenyl). ) (3-hydroxyphenyl) methane, (2-hydroxyphenyl) (4-hydroxyphenyl) methane, bis (3-hydroxyphenyl) methane, (3-hydroxyphenyl) (4-hydroxyphenyl) methane, bis (4- Hydroxyphenyl) methane, bis (2-hydroxy-3-methylphenyl) methane, bis (2-hydroxy-3-ethylphenyl) methane, (2-hydroxy-3-methylphenyl) (3-hydroxy-4-methylphenyl) ) Methane, (2-hydroxy-3-ethylphenyl) (3-hydroxy-4-ethylphenyl) Tan, (2-hydroxy-3-methylphenyl) (4-hydroxy-3-methylphenyl) methane, (2-hydroxy-3-ethylphenyl) (4-hydroxy-3-ethylphenyl) methane, bis (3- Hydroxy-4-methylphenyl) methane, bis (3-hydroxy-4-ethylphenyl) methane, (3-hydroxy-4-methylphenyl) (4-hydroxy-3-methylphenyl) methane, (3-hydroxy-4 -Ethylphenyl) (4-hydroxy-3-ethylphenyl) methane, bis (4-hydroxy-3-methylphenyl) methane, bis (4-hydroxy-3-ethylphenyl) methane, bis (4-hydroxy-3, 5-dimethylphenyl) methane, (4-hydroxy-3,5-dimethylphenyl) (3-hydroxy-2,4 -Dimethylphenyl) methane, bis (3-hydroxy-2,4-dimethylphenyl) methane, and the like.

When R ¹ is a methyl group, examples of the dihydric phenol compound corresponding to the dihydric phenol residue represented by the formula (5) include 1,1-bis (2-hydroxyphenyl) ethane, 1- (2-hydroxyphenyl) -1- (3-hydroxyphenyl) ethane, 1- (2-hydroxyphenyl) -1- (4-hydroxyphenyl) ethane, 1,1-bis (3-hydroxyphenyl) ethane 1- (3-hydroxyphenyl) -1- (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (2-hydroxy-3-methylphenyl) ethane, 1,1-bis (2-hydroxy-3-ethylphenyl) ethane, 1- (2-hydroxy-3-methylphenyl) -1- (3-hydroxy-4-methylphenyl) ethane 1- (2-hydroxy-3-ethylphenyl) -1- (3-hydroxy-4-ethylphenyl) ethane, 1- (2-hydroxy-3-methylphenyl) -1- (4-hydroxy-3) -Methylphenyl) ethane, 1- (2-hydroxy-3-ethylphenyl) -1- (4-hydroxy-3-ethylphenyl) ethane, 1,1-bis (3-hydroxy-4-methylphenyl) ethane, 1,1-bis (3-hydroxy-4-ethylphenyl) ethane, 1- (3-hydroxy-4-methylphenyl) -1- (4-hydroxy-3-methylphenyl) ethane, 1- (3-hydroxy -4-ethylphenyl) -1- (4-hydroxy-3-ethylphenyl) ethane, 1,1-bis (4-hydroxy-3-methylphenyl) ethane, 1,1-bis (4- Hydroxy-3-ethylphenyl) ethane, 1,1-bis (4-hydroxy-3,5-dimethylphenyl) ethane, 1- (4-hydroxy-3,5-dimethylphenyl) -1- (3-hydroxy- 2,4-dimethylphenyl) ethane, 1,1-bis (3-hydroxy-2,4-dimethylphenyl) ethane, and the like.

Among these, considering the simplicity of production of the dihydric phenol compound, when R ¹ is a hydrogen atom, bis (4-hydroxyphenyl) methane, (2-hydroxyphenyl) (4-hydroxyphenyl) methane, bis ( 2-hydroxyphenyl) methane, bis (4-hydroxy-3-methylphenyl) methane, bis (4-hydroxy-3-ethylphenyl) methane, bis (4-hydroxy-3,5-dimethylphenyl) methane are particularly preferred. . When R ¹ is a methyl group, 1,1-bis (4-hydroxyphenyl) ethane, 1- (2-hydroxyphenyl) -1- (4-hydroxyphenyl) ethane, 1,1-bis ( 2-hydroxyphenyl) ethane, 1,1-bis (4-hydroxy-3-methylphenyl) ethane, 1,1-bis (4-hydroxy-3-ethylphenyl) ethane, 1,1-bis (4-hydroxy) -3,5-dimethylphenyl) ethane and the like are preferred.

  Further, in the formula (3), when an example of a divalent hydroxy residue not included in the formula (5) is given, divalent hydroxy having a structure in which a hydrogen atom is removed from the hydroxyl group of the divalent hydroxy compound exemplified below. Residue.

  That is, examples of the divalent hydroxy compound corresponding to the divalent hydroxy residue represented by the formula (3) include 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxybiphenyl, 2 , 4,3 ′, 5′-tetramethyl-3,4′-dihydroxybiphenyl, 2,2 ′, 4,4′-tetramethyl-3,3′-dihydroxybiphenyl,

1,1-bis (4-hydroxyphenyl) propane, 1,1-bis (4-hydroxy-3-methylphenyl) propane, 1,1-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2 -(4-hydroxy-3,5-dimethylphenyl) -2- (3-hydroxy-2,4-dimethylphenyl) propane, 1,1-bis (3-hydroxy-2,4-dimethylphenyl) propane, 2 , 2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2- (4-hydroxy-3,5-dimethylphenyl) -2- (3-hydroxy-2,4-dimethylphenyl) propane, 2,2-bis (3-hydroxy-2,4 Dimethylphenyl) propane,

Bis- (4-hydroxyphenyl) phenylmethane, 1,1-bis- (4-hydroxyphenyl) -1-phenylethane, 1,1-bis- (4-hydroxyphenyl) -1-phenylpropane, bis- ( 4-hydroxyphenyl) diphenylmethane, bis- (4-hydroxyphenyl) dibenzylmethane,

1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxy-3-methylphenyl) cyclohexane, 1,1-bis (4-hydroxy-3,5-dimethylphenyl) cyclohexane, -(4-hydroxy-3,5-dimethylphenyl) -1- (3-hydroxy-2,4-dimethylphenyl) cyclohexane, 1,1-bis (3-hydroxy-2,4-dimethylphenyl) cyclohexane,

Bis (2-hydroxyphenyl) ether, (2-hydroxyphenyl) (3-hydroxyphenyl) ether, (2-hydroxyphenyl) (4-hydroxyphenyl) ether, bis (3-hydroxyphenyl) ether, (3-hydroxy Phenyl) (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) ether, bis (2-hydroxy-3-methylphenyl) ether, bis (2-hydroxy-3-ethylphenyl) ether, (2-hydroxy- 3-methylphenyl) (3-hydroxy-4-methylphenyl) ether, (2-hydroxy-3-ethylphenyl) (3-hydroxy-4-ethylphenyl) ether, (2-hydroxy-3-methylphenyl) ( 4-hydroxy-3-methylphenyl) ether (2-hydroxy-3-ethylphenyl) (4-hydroxy-3-ethylphenyl) ether, bis (3-hydroxy-4-methylphenyl) ether, bis (3-hydroxy-4-ethylphenyl) ether, (3 -Hydroxy-4-methylphenyl) (4-hydroxy-3-methylphenyl) ether, (3-hydroxy-4-ethylphenyl) (4-hydroxy-3-ethylphenyl) ether, bis (4-hydroxy-3- Methylphenyl) ether, bis (4-hydroxy-3-ethylphenyl) ether, bis (4-hydroxy-3,5-dimethylphenyl) ether, (4-hydroxy-3,5-dimethylphenyl) (3-hydroxy- 2,4-dimethylphenyl) ether, bis (3-hydroxy-2,4-dimethylphenol Le) ether,

Bis (4-hydroxyphenyl) ketone, etc. are mentioned.

  Among these, considering the simplicity of production of the divalent hydroxy compound, 3,3 ′, 5,5′-tetramethyl-4,4′-dihydroxybiphenyl, 2,2-bis (4-hydroxy-3) , 5-dimethylphenyl) propane, 1,1-bis (4-hydroxy-3,5-dimethylphenyl) cyclohexane, or bis (4-hydroxyphenyl) ether, (2-hydroxyphenyl) (4-hydroxyphenyl) Ether, bis (2-hydroxyphenyl) ether, bis (4-hydroxy-3-methylphenyl) ether, bis (4-hydroxy-3-ethylphenyl) ether, bis (4-hydroxy-3,5-dimethylphenyl) Ether, etc. are preferred.

  In addition, the bivalent hydroxy compound and divalent hydroxy residue mentioned above may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

On the other hand, the dicarboxylic acid residue is represented by the formula (4). In the formula (4), Ar ³ and Ar ⁴ are the same as those described in the formula (1). Specific examples of the dicarboxylic acid residue having the structure represented by the above formula (4) include dicarboxylic acid residues having a structure in which the hydroxyl group is removed from the carboxyl group of the dicarboxylic acid compound exemplified below.
That is, for example, examples of the dicarboxylic acid compound corresponding to the dicarboxylic acid residue represented by the formula (4) include diphenyl ether-2,2′-dicarboxylic acid, diphenyl ether-2,3′-dicarboxylic acid, diphenyl ether- Examples include 2,4′-dicarboxylic acid, diphenyl ether-3,3′-dicarboxylic acid, diphenyl ether-3,4′-dicarboxylic acid, diphenyl ether-4,4′-dicarboxylic acid. Among these, diphenyl ether-2,2′-dicarboxylic acid, diphenyl ether-2,4′-dicarboxylic acid, and diphenyl ether-4,4′-dicarboxylic acid are preferable, considering the simplicity of production of the dicarboxylic acid compound. -4,4'-dicarboxylic acid is particularly preferred.
In addition, the dicarboxylic acid compound and dicarboxylic acid residue mentioned above may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

（式（２）中、Ａｒ⁵〜Ａｒ⁸は、それぞれ独立に、置換基を有していてもよいフェニレン基を表わし、Ｒ¹は水素原子またはメチル基を表わす。） Therefore, it is preferable to appropriately select the aforementioned Ar ^{1 to} Ar ⁴ and X ¹ so that the structure of the divalent hydroxy residue and the dicarboxylic acid residue is the preferable structure.
From the above points, among the above-described polyester resins of the present invention, those containing a repeating structure represented by the following formula (2) are particularly preferable.

(In formula (2), Ar ^{5 to} Ar ⁸ each independently represents a phenylene group which may have a substituent, and R ¹ represents a hydrogen atom or a methyl group.)

In the formula (2), Ar ⁵ , Ar ⁶ and R ¹ are the same as those described in the formula (5).
In the formula (2), Ar ⁷ and Ar ⁸ each independently represent a phenylene group which may have a substituent. At this time, the substituents of Ar ⁷ and Ar ⁸ are the same as those described above as the substituents of Ar ^{1 to} Ar ⁴ .

Moreover, the repeating structure represented by the formula (1) may be one type in the polyester resin of the present invention, or two or more types may be used in any combination and ratio. Therefore, the above divalent hydroxy residue and dicarboxylic acid residue may be used alone or in combination of two or more in any combination and ratio. Ar ^{1 to} Ar ⁴ and X ¹ may each be used alone or in combination of two or more in any combination and ratio.

  Furthermore, the polyester resin of the present invention may contain a component other than the divalent hydroxy residue represented by the above formula (3) or the dicarboxylic acid residue represented by the formula (4) as its partial structure. For example, a resin that includes another dicarboxylic acid residue of the dicarboxylic acid residue represented by the formula (4) and includes the repeating structure of the formula (1) in a part of the structure may be used. Specific examples of other dicarboxylic acid residues include adipic acid residues, suberic acid residues, sebacic acid residues, phthalic acid residues, isophthalic acid residues, terephthalic acid residues, toluene-2,5-dicarboxylic acid Residue, p-xylene-2,5-dicarboxylic acid residue, pyridine-2,3-dicarboxylic acid residue, pyridine-2,4-dicarboxylic acid residue, pyridine-2,5-dicarboxylic acid residue, pyridine -2,6-dicarboxylic acid residue, pyridine-3,4-dicarboxylic acid residue, pyridine-3,5-dicarboxylic acid residue, naphthalene-1,4-dicarboxylic acid residue, naphthalene-2,3-dicarboxylic acid Examples include acid residues, naphthalene-2,6-dicarboxylic acid residues, biphenyl-2,2′-dicarboxylic acid residues, biphenyl-4,4′-dicarboxylic acid residues and the like. Among these, preferably, adipic acid residue, sebacic acid residue, phthalic acid residue, isophthalic acid residue, terephthalic acid residue, naphthalene-1,4-dicarboxylic acid residue, naphthalene-2,6-dicarboxylic acid residue Group, biphenyl-2,2′-dicarboxylic acid residue, biphenyl-4,4′-dicarboxylic acid residue, and particularly preferred are isophthalic acid residue and terephthalic acid residue. In addition, as for the repeating unit (residue) other than the divalent hydroxy residue represented by the above formula (3) or the dicarboxylic acid residue represented by the formula (4), one type may be used alone, or two types may be used. The above may be used in any combination and ratio.

  However, in the polyester resin of the present invention, it is preferable that the number of repeating units other than the divalent hydroxy residue represented by the formula (3) or the dicarboxylic acid residue represented by the formula (4) is small. Therefore, it is preferable that the amount of divalent hydroxy residues other than those represented by formula (3) and dicarboxylic acid residues other than those represented by formula (4) is also small. Although the specific ratio is not limited, for example, for the dicarboxylic acid residue, the ratio of the dicarboxylic acid residue represented by the formula (4) in the total amount of the dicarboxylic acid residue is usually 70 by the ratio of the number of repeating units. % Or more, preferably 80% or more, more preferably 90% or more, and particularly preferably 100%.

  Next, the manufacturing method of the polyester resin of this invention is demonstrated. As a method for producing the polyester resin of the present invention, a known polymerization method can be used. Examples thereof include an interfacial polymerization method, a melt polymerization method, and a solution polymerization method.

  For example, in the case of production by the interfacial polymerization method, a solution in which a divalent hydroxy compound is dissolved in an alkaline aqueous solution and a halogenated hydrocarbon solution in which an aromatic dicarboxylic acid chloride is dissolved are mixed. At this time, a quaternary ammonium salt or a quaternary phosphonium salt may be present as a catalyst. The polymerization temperature is preferably in the range of 0 to 40 ° C., and the polymerization time is preferably in the range of 2 to 20 hours from the viewpoint of productivity. After completion of the polymerization, the water phase and the organic phase are separated, and the polymer dissolved in the organic phase is washed and recovered by a known method, whereby the intended resin can be obtained.

  Examples of the alkali component used in the interfacial polymerization method include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. As the usage-amount of an alkali, the range of 1.01-3 times equivalent of the phenolic hydroxyl group contained in a reaction system is preferable.

  Examples of the halogenated hydrocarbon include dichloromethane, chloroform, 1,2-dichloroethane, trichloroethane, tetrachloroethane, dichlorobenzene, and the like. In addition, a halogenated hydrocarbon may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  Furthermore, examples of the quaternary ammonium salt or quaternary phosphonium salt used as the catalyst include, for example, salts of tertiary alkylamines such as tributylamine and trioctylamine such as hydrochloric acid, bromic acid, and iodic acid; benzyltriethylammonium chloride, benzyl Trimethylammonium chloride, benzyltributylammonium chloride, tetraethylammonium chloride, tetrabutylammonium chloride, tetrabutylammonium bromide, trioctylmethylammonium chloride, tetrabutylphosphonium bromide, triethyloctadecylphosphonium bromide, N-laurylpyridinium chloride, laurylpicolinium chloride, etc. Is mentioned. In addition, a catalyst may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and ratios.

  In the interfacial polymerization method, a molecular weight regulator can be used. Examples of the molecular weight regulator include phenol, o, m, p-cresol, o, m, p-ethylphenol, o, m, p-propylphenol, o, m, p- (tert-butyl) phenol, and pentyl. Phenol, hexylphenol, octylphenol, nonylphenol, alkylphenols such as 2,6-dimethylphenol derivatives and 2-methylphenol derivatives, monofunctional phenols such as o, m, p-phenylphenol, acetic acid chloride, butyric acid chloride, octyl Examples thereof include monofunctional acid halides such as acid chloride, benzoyl chloride, benzenesulfonyl chloride, benzenesulfinyl chloride, sulfinyl chloride, benzenephosphonyl chloride, and substituted products thereof.

  Among these molecular weight regulators, o, m, p- (tert-butyl) phenol, 2,6-dimethylphenol derivatives, 2-methylphenol derivatives are preferred because of their high molecular weight controllability and solution stability. Particularly preferred are p- (tert-butyl) phenol, 2,3,6-tetramethylphenol, and 2,3,5-tetramethylphenol. In addition, a molecular weight regulator may also be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  Further, in the polyester resin of the present invention, the viscosity average molecular weight is usually 10,000 or more, preferably 15,000 or more, more preferably 20,000 or more, and usually 300 so as to be suitable for coating and forming a photosensitive layer. , 000 or less, preferably 200,000 or less, more preferably 100,000 or less. If the viscosity average molecular weight is less than 10,000, the mechanical strength of the resin may be lowered and may not be practical. If the viscosity average molecular weight is more than 300,000, it is difficult to apply and form the photosensitive layer to an appropriate film thickness. There is a possibility.

<Other binder resins>
The above-described polyester resin of the present invention acts as a binder resin in the photosensitive layer. However, in addition to the polyester resin of the present invention, other resins may be used in combination for the photosensitive layer. As the other resin used in combination, any resin can be used as long as the effects of the present invention are not significantly impaired. For example, vinyl polymers such as polymethyl methacrylate, polystyrene, polyvinyl chloride, and the like can be used. Examples thereof include thermoplastic resins such as a polymer, polycarbonate, polyester, polyester polycarbonate, polysulfone, phenoxy, epoxy, and silicone resin, and various thermosetting resins. Of these resins, polycarbonate resin is preferable.

In addition, other resin may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.
Moreover, although the usage rate of the resin used together is not specifically limited, in order to fully obtain the effect of this invention, it is preferable to use together in the range which does not exceed the ratio of the polyester resin of this invention. In particular, it is preferable not to use other resins in combination.

[II. Electrophotographic photoreceptor]
The photoreceptor of the present invention comprises a photosensitive layer containing the polyester resin of the present invention. The photosensitive layer is usually provided on a conductive support (also referred to as “conductive substrate”). Further, the polyester resin of the present invention acts as a binder resin in the photosensitive layer.

  Here, as a specific structure of the photosensitive layer, a charge generating substance and a charge transporting substance are present in the same layer and dispersed or dissolved in a binder resin (single layer type or dispersed type). It is a layer. A photoreceptor having a single layer type photosensitive layer is a so-called single layer type photoreceptor (or a dispersion type photoreceptor). And the polyester resin of this invention is contained in said single layer type photosensitive layer, and acts as binder resin.

[II-1. Conductive support]
There are no particular restrictions on the conductive support, but for example, metallic materials such as aluminum, aluminum alloy, stainless steel, copper and nickel; conductive powders such as metal, carbon and tin oxide were mixed to impart conductivity. Resin material: Resin, glass, paper, or the like obtained by depositing or coating a conductive material such as aluminum, nickel, ITO (indium-tin oxide) on its surface is mainly used. Moreover, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
Furthermore, as a form of the conductive support, for example, a drum shape, a sheet shape, a belt shape or the like is used. Further, a conductive material having an appropriate resistance value may be coated on a conductive support made of a metal material in order to control conductivity and surface properties or to cover defects.

Further, when a metal material such as an aluminum alloy is used as the conductive support, it may be used after anodizing, chemical conversion coating or the like. When the anodizing treatment is performed, it is desirable to perform a sealing treatment by a known method.
The surface of the 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 conductive support.

[II-2. Undercoat layer]
An undercoat layer may be provided between the conductive support and the photosensitive layer described later for improving adhesion and blocking properties. As the undercoat layer, a resin alone or a resin in which a metal oxide particle (usually inorganic particles) or an organic pigment is dispersed in the resin 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. One kind of these particles may be used alone, or a plurality of kinds 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 substance such as tin oxide, aluminum oxide, antimony oxide, zirconium oxide, or silicon oxide, or an organic substance 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. As for the crystal type, a plurality of crystal states may be included in any combination and ratio.

  In addition, various particle sizes of the metal oxide particles can be used. Among these, from the viewpoint of characteristics and liquid stability, the average primary particle size is usually 1 nm or more, preferably 10 nm or more, and usually 100 nm. Below, preferably 50 nm or less.

  The undercoat layer is preferably formed in a form in which metal oxide particles are dispersed in a binder resin. Examples of the binder resin used for the undercoat layer include phenoxy, epoxy, polyvinyl pyrrolidone, polyvinyl alcohol, casein, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, and polyamide. Among these, alcohol-soluble copolymerized polyamide, modified polyamide, and the like are preferable because they exhibit good dispersibility and coating properties. The binder resin for the undercoat layer may be used alone or in combination of two or more in any combination and ratio. Furthermore, the binder resin can be used in the form of being cured together with the curing agent, in addition to being used only with the binder resin.

  In the case of a single layer type photoreceptor such as the photoreceptor of the present invention, the charge generation layer in the laminated type photoreceptor can be substituted for the undercoat 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.

In addition, the use ratio of the particles with respect to the binder resin can be arbitrarily selected, but it is usually preferable in the range of 10% by weight to 500% by weight in view of the stability of the dispersion and the coating property.
Furthermore, the thickness of the undercoat layer is arbitrary as long as the effects of the present invention are not significantly impaired, but from the photoreceptor characteristics and applicability, it is usually preferably from 0.1 μm to 25 μm. The undercoat layer may contain an additive such as an antioxidant.

[II-3. Photosensitive layer]
The photoreceptor of the present invention has a single-layer type photosensitive layer. This single-layer type photosensitive layer is constituted by dissolving or dispersing a charge transport material in a binder resin and further dispersing a charge generation material.

  The charge transport material is not particularly limited, and any material can be used. Examples of known charge transport materials include electron-withdrawing materials such as aromatic nitro compounds such as 2,4,7-trinitrofluorenone, cyano compounds such as tetracyanoquinodimethane, and quinone compounds such as diphenoquinone, 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 multiple types of these compounds Or an electron donating substance such as a polymer having a group consisting 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 one kind of charge transport materials may be used alone, or two or more kinds may be used in any combination and ratio.

  Specific examples of suitable structures of the charge transport material are shown below. However, these specific examples are shown for illustration, and any known charge transport material may be used in the present invention as long as it does not contradict the gist of the present invention. Note that Bu represents a butyl group, and t-Bu represents a tertiary butyl group.

  The amount of the charge transport material used is arbitrary as long as the effects of the present invention are not significantly impaired. However, the amount of the charge transport material is usually 30 parts by weight or more, preferably 40 parts by weight or more, and usually 200 parts by weight or less, preferably 150 parts by weight or less with respect to 100 parts by weight of the binder resin in the photosensitive layer. is there. If the amount of the charge 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.

  On the other hand, examples of the charge generating substance include selenium and its alloys, cadmium sulfide, and other inorganic photoconductive materials; Various photoconductive materials such as organic pigments such as imidazole pigments can be used. Among these, organic pigments are particularly preferable, and phthalocyanine pigments and azo pigments are more preferable.

  In particular, when a phthalocyanine compound is used as the charge generation material, specifically, a metal such as metal-free phthalocyanine, copper, indium, gallium, tin, titanium, zinc, vanadium, silicon, germanium, or an oxide or halide thereof. Coordinated phthalocyanines are used. Examples of the ligand to the trivalent or higher metal atom include a hydroxyl group and an alkoxy group in addition to the oxygen atom and chlorine atom shown above. Among them, particularly sensitive X-type, τ-type metal-free phthalocyanine, A-type, B-type, D-type titanyl phthalocyanine, vanadyl phthalocyanine, chloroindium phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, and the like are preferable.

  Of the crystal forms of titanyl phthalocyanine mentioned here, A type and B type are described in W.W. It has been shown by Heller et al. As phase I and phase II (Zeit. Kristallogr. 159 (1982) 173), respectively, and type A is known as a stable type. The D-type is a crystal type characterized by a clear peak at a diffraction angle 2θ ± 0.2 ° of 27.3 ° in powder X-ray diffraction using CuKα rays.

  In addition, the charge generation material may be used alone or in combination of two or more in any combination and ratio. Furthermore, when two or more charge generation materials are used in combination, the charge generation material used in combination and the mixed state in the crystalline state may be used by mixing the respective constituent elements later, or synthesis, pigmentation Alternatively, a mixed state may be generated and used in the charge generation material production / treatment process such as crystallization. As such treatment, acid paste treatment, grinding treatment, solvent treatment and the like are known.

In this case, it is desirable that the particle size of the charge generation material is sufficiently small. Specifically, it is usually 1 μm or less, preferably 0.5 μm or less.
Furthermore, if the amount of the charge generating material dispersed in the photosensitive layer is too small, there is a possibility that sufficient sensitivity cannot be obtained, and if it is too large, there are problems such as a decrease in chargeability and a decrease in sensitivity. Therefore, the amount of the charge generating substance in the single-layer type photosensitive layer is usually 0.5% by weight or more, preferably 1% by weight or more, and usually 50% by weight or less, preferably 20% by weight or less.

  The photosensitive layer contains the polyester resin of the present invention as a binder resin in addition to these charge transport materials and charge generation materials. That is, the photosensitive layer is formed in such a manner that the charge transport material and the charge generation material are bound to the binder resin containing the polyester resin of the present invention. At this time, as the binder resin, as described above, a resin other than the polyester resin of the present invention may be used in combination.

  In addition, the photosensitive layer is preferably composed of a single layer, but a plurality of layers having different constituent components or composition ratios may be stacked. Even in the latter case, it is called a single-layer type photoreceptor because of the function of the material in the layer. At this time, in the photoreceptor of the present invention, the polyester resin of the present invention may be contained in one or more of the layers constituting the photosensitive layer.

  Furthermore, 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 (eg, 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.

[II-4. Other layers]
In addition to the undercoat layer and the photosensitive layer, other layers may be further provided on the photoreceptor.
For example, a protective layer may be provided on the photosensitive layer for the purpose of preventing the photosensitive layer from being worn out or preventing or reducing the deterioration of the photosensitive layer due to discharge products generated from a charger or the like. In addition, the outermost surface layer may contain, for example, a fluorine resin, a silicone resin, or the like for the purpose of reducing frictional resistance and wear on the surface of the photoreceptor, and further, particles and inorganic compounds made of these resins. Particles may be included.

[II-5. Formation method of each layer]
There are no limitations on the method of forming each layer such as the undercoat layer, the photosensitive layer, and the protective layer. For example, a known method of applying a coating solution obtained by dissolving or dispersing a substance to be contained in a layer to be formed in a solvent directly on a conductive support or through another layer is applied. it can. Therefore, for example, in the case of a photosensitive layer containing the polyester resin of the present invention, it can be formed by the following method. That is, a coating liquid containing a charge transport material, a charge generation material, the polyester resin of the present invention, and a solvent, a binder resin to be used in combination, an additive, and the like as necessary is prepared. And the said coating liquid is apply | coated on an electroconductive support body directly or through another layer (For example, when providing an undercoat layer, it is on an undercoat layer.). Then, the photosensitive layer can be formed by removing the solvent by drying.

  In this case, the coating method is not limited and may be arbitrary. 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, or the like can be used. Among these, the dip coating method is preferable because of its high productivity. Note that these coating methods may be performed by only one method, or may be performed by combining two or more methods.

  When the polyester resin of the present invention is used as the binder resin, it is possible to obtain the advantages that the coating solution for forming the photosensitive layer can prevent the binder resin from being deposited and suppress the cloudiness of the coating solution. The reason why such an advantage can be obtained is not clear, but is presumed to be due to the chemical structure unique to the polyester resin of the present invention.

[II-6. Photoconductor charging type]
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. As described above, by using the photoconductor of the present invention, it is possible to improve the wear resistance and the electric characteristics against the practical load of the photoconductor. That is, conventionally, positively charged photoconductors have advantages such as reduced ozone generation and high resolution, but the photosensitive layer contains not only a charge transporting material but also a charge generating material together with a binder resin. Although the wear resistance was low, the use of the polyester resin of the present invention improves both the wear resistance and the electrical properties. The reason why such an advantage can be obtained is not clear, but is presumed to be due to the chemical structure unique to the polyester resin of the present invention.

[II-7. Photoconductor exposure wavelength]
When forming an image, the photosensitive member of the present invention is exposed to 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. Among them, monochromatic light having an exposure wavelength of usually 380 nm or more, particularly 400 nm or more, and usually 500 nm or less, particularly 480 nm or less. It is preferable to use it. Thereby, a photoconductor excellent in wear resistance can be exposed with light having a smaller spot size, and a high-quality image having high resolution and high gradation can be formed.

[III. 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. However, the embodiment is not limited to the following description, and can be arbitrarily modified without departing from the gist of the present invention.

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

  The electrophotographic photoreceptor 1 is not particularly limited as long as it is the above-described electrophotographic photoreceptor of the present invention, but in FIG. 1, as an example, a drum in which the above-described photosensitive layer is formed on the surface of a cylindrical conductive support. The photoconductor is shown. 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 electrophotographic photoreceptor 1.

  The charging device 2 charges the electrophotographic photoreceptor 1 positively, and uniformly charges the surface of the electrophotographic photoreceptor 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 other corona charging devices such as corotron and scorotron, and contact-type charging devices such as charging brushes are often used.

  In many cases, the electrophotographic photosensitive member 1 and the charging device 2 are cartridges having both of them (the electrophotographic photosensitive member cartridge of the present invention. Designed to be removable from. 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 electrophotographic photoreceptor 1 or the charging device 2 deteriorates, the photoreceptor cartridge can be removed from the image forming apparatus main body, and another new photosensitive cartridge can be mounted on the image forming apparatus main body. ing. 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 the toner may be used.

  The type of exposure apparatus 3 is not particularly limited as long as it can form an electrostatic latent image on the photosensitive surface of the electrophotographic photosensitive member 1 by performing exposure (image exposure) on the electrophotographic photosensitive member 1. Absent. 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 used for the exposure is arbitrary, but is generally preferably monochromatic light. For example, monochromatic light with a wavelength (exposure wavelength) of 700 nm to 850 nm, monochromatic light with a wavelength of 600 nm to 700 nm slightly shorter, or with a wavelength of 300 nm to 500 nm. Exposure may be performed with short-wave monochromatic light or the like. Among these, [II-7. As described in [Exposure Wavelength of Photoreceptor], exposure is preferably performed with monochromatic light having a wavelength of 380 nm to 500 nm.

  The type of the developing device 4 is not particularly limited as long as it can develop the exposed electrostatic latent image on the electrophotographic photosensitive member 1 into a visible image. As a specific example, an arbitrary apparatus such as a dry development system such as cascade development, one-component conductive toner development, or two-component magnetic brush development, or a wet development system can be used. In FIG. 1, the developing device 4 includes a developing tank 41, an agitator 42, a supply roller 43, a developing roller 44, and a regulating member 45, and has a configuration in which toner T is stored inside the developing tank 41. . Further, a replenishing device (not shown) for replenishing the toner T may be attached to the developing device 4 as necessary. The replenishing device is configured to be able to replenish toner T from a container such as a bottle or a cartridge.

  The supply roller 43 is formed from a conductive sponge or the like. The developing roller 44 is made of a metal roll such as iron, stainless steel, aluminum, or nickel, or a resin roll obtained by coating such a metal roll with a silicone resin, a urethane resin, a fluorine resin, or the like. The surface of the developing roller 44 may be smoothed or roughened as necessary.

  The developing roller 44 is disposed between the electrophotographic photoreceptor 1 and the supply roller 43 and is in contact with the electrophotographic photoreceptor 1 and the supply roller 43, respectively. 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 silicone resin or urethane resin, a metal blade such as stainless steel, aluminum, copper, brass, phosphor bronze, or a blade obtained by coating such metal blade with resin. The 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 (a general blade linear pressure is 0.05 to 5 N / cm). If necessary, the regulating member 45 may be provided with a function of imparting charging to the toner T by frictional charging 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 in addition to the powdery toner, a polymerized toner using 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 to 8 μm is preferable, and the toner particles are used in various shapes ranging from a nearly spherical shape to a shape outside the spherical shape on the potato. be able to. The polymerized toner is excellent in charging uniformity and transferability and is suitably used for high image quality.

  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. . Here, 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 photoreceptor 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. Each of the upper and lower fixing members 71 and 72 includes a fixing roll in which a metal base tube such as stainless steel or aluminum is coated with silicon rubber, a fixing roll in which Teflon (registered trademark) resin is coated, and a fixing sheet. A member can be used. Further, each of the fixing members 71 and 72 may be configured to supply a release agent such as silicone oil in order to improve releasability, or may be configured to forcibly apply pressure to each other by a spring or the like.

When the toner transferred onto the recording paper P passes between the upper fixing member 71 and the lower fixing member 72 heated to a predetermined temperature, the toner is heated to a molten state and cooled after passing through the recording paper. Toner is fixed on P.
The type of the fixing device is not particularly limited, and a fixing device of any type such as heat roller fixing, flash fixing, oven fixing, pressure fixing, etc. can be provided including those used here.

In the electrophotographic apparatus configured as described above, the charging process for positively charging the photoconductor, the exposure process for exposing the charged photoconductor to form an electrostatic latent image, and the electrostatic latent image as toner. The image is recorded by performing a developing process for developing the toner and a transferring process for transferring the toner to the transfer target. 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.

  Then, development of the electrostatic latent image formed on the photosensitive surface of the photoreceptor 1 is performed by the developing device 4 (developing process). The developing device 4 thins the toner T supplied by the supply roller 43 by a regulating member (developing blade) 45 and has a predetermined polarity (here, the same polarity as the charging potential of the photosensitive member 1) and positive polarity. ), And conveyed while being carried on the developing roller 44 to be brought into contact with the surface of the photoreceptor 1. When the charged toner T carried on the developing roller 44 comes into contact with the surface of the photoreceptor 1, a toner image corresponding to the electrostatic latent image is formed on the photosensitive surface of the photoreceptor 1.

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.

  In addition to the above-described configuration, the image forming apparatus may have a configuration capable of performing, for example, a static elimination process. The neutralization step is a step of neutralizing the electrophotographic photosensitive member by exposing the electrophotographic photosensitive member, and a fluorescent lamp, an LED, or the like is used as the neutralizing device. 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.

  The image forming apparatus may be further modified. For example, the image forming apparatus may be configured to perform a pre-exposure process, an auxiliary charging process, or the like, or may be configured to perform offset printing. A full-color tandem system configuration using toner may be used.

  The photosensitive member 1 is configured as a cartridge in combination with the charging device 2 as described above, and one or two of the exposure device 3, the developing device 4, the transfer device 5, the cleaning device 6, and the fixing device 7 are used. In combination with the above, an integrated cartridge (electrophotographic photosensitive member cartridge) may be configured, and the electrophotographic photosensitive member cartridge may be detachable from an electrophotographic apparatus main body such as a copying machine or a laser beam printer. . Therefore, the photosensitive member 1 can be a cartridge that integrally supports at least one of the charging device 2, the exposure device 3, the developing device 4, and the transfer device 5 together with the photosensitive member 1. 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. However, the following examples are given in order to explain the present invention in detail, and the present invention is not limited to the examples shown below without departing from the gist thereof, and can be arbitrarily modified and implemented. can do. In addition, the description of “parts” in the following examples, comparative examples, and reference examples indicates “parts by weight” unless otherwise specified.

<Measurement method of viscosity average molecular weight of resin>
First, a method for measuring the viscosity average molecular weight of the resin will be described.
The resin to be measured is dissolved in dichloromethane to prepare a solution having a concentration C of 6.00 g / L. The flow time t of the sample solution is measured in a constant temperature water bath set to 20.0 ° C. using an Ubbelohde capillary viscometer with a flow time t ₀ of the solvent (dichloromethane) of 136.16 seconds. The viscosity average molecular weight Mv is calculated according to the following formula.
a = 0.438 × η _sp +1 η _sp = (t / t ₀ ) −1
b = 100 × η _sp / C C = 6.00
η = b / a
Mv = 3207 × η ^1.205

<Manufacture of polyester resin>
Hereinafter, the manufacturing method of a polyester resin is demonstrated.
[Production Example 1 (Resin X)]
In a 1000 mL beaker, 23.01 g of sodium hydroxide and 940 mL of H ₂ O were weighed and dissolved while stirring. Thereto, 49.36 g of bis (4-hydroxy-3-methylphenyl) methane (hereinafter referred to as “BP-a” as appropriate) was added, stirred and dissolved, and then the aqueous alkaline solution was transferred to a 2 L reaction vessel. Next, 0.5766 g of benzyltriethylammonium chloride and 1.2955 g of 2,3,5-trimethylphenol were sequentially added to the reaction vessel.

  Next, a mixed solution of 65.27 g of diphenyl ether-4,4′-dicarboxylic acid chloride and 470 mL of dichloromethane was transferred into the dropping funnel. The mixed solution was dropped from the dropping funnel over 1 hour while maintaining the external temperature of the polymerization tank at 20 ° C. and stirring the alkaline aqueous solution in the reaction tank. After further stirring for 5 hours, 783 mL of dichloromethane was added and stirring was continued for 7 hours. Thereafter, 8.34 mL of acetic acid was added and stirred for 30 minutes, and then the stirring was stopped and the organic layer was separated.

This organic layer was washed twice with 942 mL of 0.1N aqueous sodium hydroxide solution, then twice with 942 mL of 0.1N hydrochloric acid, and further twice with 942 mL of H ₂ O. The washed organic layer was poured into 6266 mL of methanol, and the resulting precipitate was removed by filtration and dried to obtain the desired resin X. The obtained resin X had a viscosity average molecular weight of 51,400. The repeating structure of Resin X is shown below.

[Production Example 2 (Resin Y)]
In a 1000 mL beaker, 22.34 g of sodium hydroxide and 940 mL of H ₂ O were weighed and dissolved while stirring. Thereto was added 51.04 g of 1,1-bis (4-hydroxy-3-methylphenyl) ethane (hereinafter referred to as “BP-b” as appropriate), stirred and dissolved, and then the aqueous alkaline solution was transferred to a 2 L reactor. . Next, 0.5579 g of benzyltriethylammonium chloride and 1.0613 g of 2,3,5-trimethylphenol were sequentially added to the reaction vessel.

  Separately, a mixed solution of 63.37 g of diphenyl ether-4,4′-dicarboxylic acid chloride and 470 mL of dichloromethane was transferred into the dropping funnel. While maintaining the external temperature of the polymerization tank at 20 ° C. and stirring the alkaline aqueous solution in the reaction tank, the dichloromethane solution was dropped from the dropping funnel over 1 hour. After further stirring for 5 hours, 783 mL of dichloromethane was added and stirring was continued for 7 hours. Thereafter, 8.10 mL of acetic acid was added and stirred for 30 minutes, then stirring was stopped and the organic layer was separated.

This organic layer was washed twice with 942 mL of 0.1N aqueous sodium hydroxide solution, then twice with 942 mL of 0.1N hydrochloric acid, and further twice with 942 mL of H ₂ O. The washed organic layer was poured into 6266 mL of methanol, and the resulting precipitate was removed by filtration and dried to obtain the desired resin B. The obtained resin Y had a viscosity average molecular weight of 51,700. The repeating structure of Resin Y is shown below.

<Manufacture of photoreceptor sheet>
[Example 1]
The undercoat layer dispersion was produced as follows. That is, a rutile type titanium oxide having an average primary particle size of 40 nm (“TTO55N” manufactured by Ishihara Sangyo Co., Ltd.) and 3% by weight of methyldimethoxysilane (“TSL8117” manufactured by Toshiba Silicone Co., Ltd.) with respect to the titanium oxide were flowed at high speed. In a mixed solvent of methanol / 1-propanol in a mixed solvent of methanol / 1-propanol, which was introduced into a mixing kneader (“SMG300” manufactured by Kawata Co., Ltd.) and mixed at a high rotational speed of 34.5 m / sec. Then, a dispersion slurry of hydrophobized titanium oxide was obtained by dispersing with a ball mill. The dispersion slurry, a mixed solvent of methanol / 1-propanol / toluene, and ε-caprolactam [compound represented by the following formula (A)] / bis (4-amino-3-methylcyclohexyl) methane [the following formula (B Compound represented by the following formula (C)] / decamethylene dicarboxylic acid [compound represented by the following formula (D)] / octadecamethylene dicarboxylic acid [in the following formula (E) The compositional molar ratio of the compound represented] is 60% / 15% / 5% / 15% / 5% of the copolymerized polyamide pellets with heating and stirring and mixing to dissolve the polyamide pellets. By performing sonic dispersion treatment, the weight ratio of methanol / 1-propanol / toluene is 7/1/2, and the hydrophobically treated titanium oxide / co-polymer is mixed. Containing a slip polyamide in a weight ratio of 3/1, and a solid concentration of 18.0% of the undercoat layer dispersion.

  The undercoat layer-forming coating solution thus obtained was applied onto a polyethylene terephthalate sheet having aluminum deposited on the surface with a wire bar so that the film thickness after drying was 1.2 μm, and dried. Was provided.

  Next, in X-ray diffraction by CuKα ray, a Bragg angle (2θ ± 0.2) showed a strong diffraction peak at 27.3 °, and 5 parts by weight of oxytitanium phthalocyanine having a powder X-ray diffraction spectrum shown in FIG. Dispersed together with 70 parts by weight by a sand grind mill. Similarly, 8 parts by weight of an electron transport material represented by the following structural formula (6) was dispersed together with 112 parts by weight of toluene by a sand grind mill. On the other hand, 60 parts by weight of the hole transport material represented by the following structural formula (7) and 100 parts by weight of the binder resin X produced in Production Example 1 are dissolved in 420 parts by weight of toluene, and 0.05 parts of silicone oil is used as a leveling agent. And the above two dispersions were mixed with a homogenizer so as to be uniform. The coating solution thus prepared was applied on the undercoat layer so that the film thickness after drying was 25 μm, and a positively charged single layer type electrophotographic photosensitive member A was obtained. At this time, the solubility of the resin in the solvent was good, and no symptoms such as gelation were observed even after one month had passed since the coating solution was prepared.

[Example 2]
A photoconductor B was obtained in the same manner as in Example 1 except that 100 parts of the resin Y produced in Production Example 2 was used as the binder resin. At this time, the solubility of the binder resin in the solvent was good, and no symptoms such as gelation were observed even after one month had passed since the coating solution was prepared.

[Example 3]
In X-ray diffraction by CuKα ray, a Bragg angle (2θ ± 0.2) shows a strong diffraction peak at 27.3 °, and 10 parts by weight of oxytitanium phthalocyanine having a powder X-ray diffraction spectrum shown in FIG. In addition to 150 parts by weight of dimethoxyethane, pulverization and dispersion treatment was performed with a sand grind mill to prepare a pigment dispersion. 160 parts by weight of the pigment dispersion thus obtained was mixed with 100 parts by weight of a 5% 1,2-dimethoxyethane solution of polyvinyl butyral (trade name # 6000C, manufactured by Denki Kagaku Kogyo Co., Ltd.) and an appropriate amount of 1,2- In addition to dimethoxyethane, a dispersion having a solid concentration of 4.0% by weight was finally prepared.
This dispersion was applied on a polyethylene terephthalate sheet having aluminum deposited on the surface with a wire bar so that the film thickness after drying was 0.4 μm, and then dried to form an undercoat layer.
On this, a photosensitive layer similar to that of Example 2 was applied by 25 μm to obtain a photoreceptor C.

[Comparative Example 1]
A photoreceptor D was obtained in the same manner as in Example 2 except that a known polyarylate resin Z represented by the following structural formula (8) was used as the binder resin. The viscosity average molecular weight of this polyarylate resin Z was 48,000.

[Comparative Example 2]
A photoreceptor E was obtained in the same manner as in Example 2 except that the polycarbonate resin W represented by the following structural formula (9) was used as the binder resin. The viscosity average molecular weight of this polycarbonate resin W was 50,000.

<Evaluation>
The produced photoreceptor sheets A to E were subjected to the following electrical property test and wear test, and the results are summarized in Table 1.

<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 photoreceptor 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, it may be referred to as VL). In the VL 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%.

<Abrasion test>
The photoreceptor sheet was cut into a circle having a diameter of 10 cm, and the wear was evaluated with a Taber abrasion tester (manufactured by Taber). Test conditions were measured by comparing the weight before and after the test with 1000 wheels without load (the weight of the wear wheel) under the atmosphere of 23 ° C. and 50% RH and without wear (self-weight of the wear wheel). did.

  From the above results, it can be seen that only the single layer type photoreceptor containing the polyester resin of the present invention ensures both wear resistance and electrical characteristics.

[Example 4]
Instead of the hole transport material represented by the formula (7), 30 parts each of the compound (10) and the compound (11) having the following structure were used in the same manner as in Example 2 except that 60 parts in total were used. Thus, a photoreceptor sheet F was obtained.

[Comparative Example 3]
A photoreceptor sheet G was obtained in the same manner as in Example 4 except that the resin Z was used instead of the resin Y.

[Evaluation]
The photoreceptor sheets F and G obtained above were subjected to the following electrical property test 2 and the above-described wear test. These results are summarized in Table 2.

<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 photoreceptor is charged to +700 V and the light of the halogen lamp is changed to monochromatic light of 405 nm with an interference filter is exposed at 2.0 μJ / cm ² ( Hereinafter, it may be referred to as VL). In the VL 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%.

  From the results shown in Table 2, it can be seen that the photoreceptor of Example 4 exhibits suitable electrical characteristics when exposed to monochromatic light of 405 nm. Therefore, it was confirmed that a good image can be formed by exposure with blue light such as blue LED or blue LD.

  The present invention can be used in any field where an electrophotographic photosensitive member is used, and is particularly suitable for use in an image forming apparatus such as a printer or a copying machine.

1 is a schematic diagram illustrating a main configuration of an embodiment of an image forming apparatus of the present invention. It is an X-ray diffraction diagram showing a powder X-ray diffraction spectrum of oxytitanium phthalocyanine used in Examples and Comparative Examples of the present invention.

Explanation of symbols

1 Electrophotographic photoreceptor 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

Claims (6)

A positively charged electrophotographic photosensitive member having a single-layer type photosensitive layer on a conductive support,
A positively charged electrophotographic photosensitive member, wherein the single-layer type photosensitive layer contains a polyester resin having a repeating structure represented by the following formula (2).

(In Formula (2), Ar ^{5 to} Ar ⁸ each independently represent a phenylene group which may have a substituent, and R ¹ represents a hydrogen atom or a methyl group.)
However, the case where the single-layer type photosensitive layer contains any one of polytrifluoroethylene and perfluoropolyether or a mixture thereof is excluded. 2. The positively charged electrophotographic photosensitive member according to claim 1, wherein the positively charged electrophotographic photosensitive member is used with monochromatic writing light having a wavelength of 380 to 500 nm. The positively charged electrophotographic photosensitive member according to claim 1 or 2,
Charging means for positively charging the electrophotographic photosensitive member;
Exposure means for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image; and
Developing means for developing the electrostatic latent image with toner;
An image forming apparatus comprising: a transfer unit that transfers the toner to a transfer target. 4. An image forming apparatus according to claim 3, wherein said exposure means performs exposure with monochromatic light having an exposure wavelength of 380 nm to 500 nm. An image forming method for forming an image using the positively charged electrophotographic photosensitive member according to claim 1 or 2,
A charging step for positively charging the positively charged electrophotographic photosensitive member;
Exposing the charged electrophotographic photosensitive member to form an electrostatic latent image; and
A developing step of developing the electrostatic latent image with toner;
And a transfer step of transferring the toner to a transfer medium. The positively charged electrophotographic photosensitive member according to claim 1 or 2,
An electrophotographic photosensitive member cartridge comprising charging means for positively charging the electrophotographic photosensitive member.

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