JPH07281456A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To maintain durability, to prevent the occurrence of image defects at the time of repetitive use and to ensure stable electrical characteristics by using polyarylate resin in combination with a cresol compd. CONSTITUTION:When a photosensitive layer contg. a photoconductive material and a binding resin is formed on an electric conductive substrate to obtain an electrophotographic photoreceptor, polyarylate resin having structural units represented by formula I is incorporated into the bonding resin in the photosensitive layer and a cresol compd. having a structural unit represented by formula II is incorporated into the photosensitive layer. In the formula I, halogen, an aliphatic group which may have a substituent or a carbocyclic group which may have a substituent may be substd. for H on each arom. group and (n) is an integer of 10-1,000. In the formula II, each of R<1> and R<2> is H, an aliphatic group which may have a substituent or a carbocyclic group which may have a substituent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoconductor, and more particularly to an electrophotographic photoconductor having excellent durability using a polyarylate resin having a specific structure.

[0002]

2. Description of the Related Art Generally, it is said that a hydrophobic, electrically insulating film-forming resin is preferably used as a binder for a photosensitive layer of an electrophotographic photoreceptor formed by a coating method.

However, with the resins used hitherto, a photosensitive layer which can sufficiently satisfy the required characteristics in terms of both mechanical strength and electrophotographic characteristics has not been obtained, and an electrophotographic photoreceptor having further excellent characteristics is realized. Therefore, improvement has been strongly desired.

Since polyarylate resins generally have high electric insulation and excellent mechanical strength, they have been conventionally studied as a binder resin for the photosensitive layer of an electrophotographic photoreceptor. For example, JP-A-56-135844 discloses that
A technique is disclosed in which a polyarylate having a specific structure, which is commercially available under the trade name "U-polymer", is used as a binder resin. However, although the U-polymer is relatively excellent in mechanical strength, it has poor stability as a coating because it easily gels when dissolved in a solvent, and also in the photosensitive layer obtained repeatedly. The electrical characteristics at that time were unstable, which was insufficient for practical use.

As a method for improving these points, the inventors of the present invention have disclosed in JP-A-5-297601 that by using a polyarylate having a specific structure, the mechanical properties of a conventional electrophotographic photoreceptor can be improved. Improved electrical properties,
Further, a technique has been disclosed which can realize a more preferable practically preferable electrophotographic photoreceptor having excellent stability as a coating material.

[0006]

However, the electrophotographic photoreceptor using the polyarylate resin is excellent in mechanical strength and has a small amount of abrasion of the photosensitive layer, so that the charge contained in the surface layer of the photoreceptor is reduced. The transport material or charge generation material will continue to be chemically affected by ozone, nitrogen compounds, etc. which are inevitably generated in the electrophotographic process for a long period of time, and as a result, image defects such as image deletion when repeatedly used. It was also found that the increase of the residual potential is likely to occur.

The problem to be solved by the present invention is to provide an electrophotographic photosensitive member having a photosensitive layer using a polyarylate having a specific structure, while maintaining durability, without the appearance of image defects during repeated use, An object of the present invention is to provide an electrophotographic photoreceptor having stable electric characteristics.

[0008]

Means for Solving the Problems As a result of careful investigations on the practical application of a polyarylate resin having a specific structure, the inventors have found that the use of a cresol compound in combination with the polyarylate resin is extremely suitable. The inventors have found that an electrophotographic photoreceptor having various characteristics can be realized, and completed the present invention.

That is, in order to solve the above-mentioned problems, the present invention provides an electrophotographic photosensitive member comprising a conductive support and a photosensitive layer containing a photoconductive substance and a binder resin.
The binder resin of the photosensitive layer is represented by the general formula (I)

[0010]

[Chemical 3]

(In the formula, the hydrogen atom on the aromatic ring may be substituted with a halogen atom, an aliphatic group which may have a substituent, or a carbocyclic group which may have a substituent. , N represents an integer between 10 and 1000) and has a structural unit represented by the general formula (II) in the photosensitive layer.

[0012]

[Chemical 4]

(Wherein R ¹ and R ² represent a hydrogen atom, an aliphatic group which may have a substituent, or a carbocyclic group which may have a substituent). Provided is a photoreceptor for electrophotography, which comprises a cresol compound having a unit in the molecule.

The polyarylate represented by the above general formula (I) used in the present invention is available as a commercial product, for example, "ISARY L25S" manufactured by ISONOVA.
Etc.

Examples of the cresol compound represented by the above general formula (II) used in the present invention include 2,6-
Di-tert-butyl-p-cresol, 2,6-di-tert
-Butyl-m-cresol, 2,4-di-tert-butyl-o-cresol, 2,4-di-methyl-6-tert-butyl-phenol, 2,2'-methylene-bis (6-te
rt-butyl-p-cresol), 4,4′-methylene-
Bis (6-tert-butyl-o-cresol), 4,4 '
-Thiobis (6-tert-butyl-m-cresol),
4,4'-butylidene-bis (6-tert-butyl-m-
Cresol), 1,1,3-tris (2-methyl-4-)
Hydroxy-5-tert-butyl-phenyl) butane and the like can be mentioned, and of these, 2,6-di-tert-butyl-p-cresol is particularly preferable.

The binder resin for the photosensitive layer is represented by the general formula (I)
The polyarylate represented by is used, but if necessary, other resins can be mixed in an appropriate ratio and used.

As the resin to be mixed if necessary, an electrically insulating film-forming polymer which is capable of forming a film is preferable. Examples of such high molecular weight polymers include polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile polymer, and chloride. Vinyl-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polyvinyl butyral, polyvinyl. Formal, polysulfone, casein, gelatin, polyvinyl alcohol, ethyl cellulose, phenol resin,
Examples thereof include, but are not limited to, polyamide, carboxy-methyl cellulose, vinylidene chloride-based polymer latex, polyurethane and the like. These high molecular weight polymers may be used alone or in combination of two or more when used in combination with the polyarylate resin represented by the above general formula (I) used in the present invention. it can.

The cresol compound is preferably added in an amount of 1 to 10% by weight based on the binder resin.

In the present invention, the structure of the photosensitive layer can take various forms. Examples thereof are shown in FIGS.

The electrophotographic photoreceptor of FIG. 1 is provided with a photosensitive layer in which a charge generating material is dispersed in a binder resin. FIG. 2 shows a photosensitive layer formed by dispersing a charge generating material and a charge transporting material in a binder resin. 3 and 4
Is a photosensitive layer in which a charge generating layer mainly composed of a charge generating material and a charge transporting layer mainly composed of a charge transporting material are laminated. The film thickness of these photosensitive layers is preferably in the range of 5 to 50 μm.

Further, in the laminated type electrophotographic photoreceptor having two or more photosensitive layers, the effect of the present invention can be obtained by designing at least the uppermost layer so as to satisfy the constitutional requirements of the present invention. .

Examples of the conductive support used in the electrophotographic photoreceptor of the present invention include metals or alloys such as aluminum, copper, zinc, stainless steel, chromium, nickel, molybdenum, vanadium, indium, gold and platinum. The used metal plate, metal drum, metal belt, or conductive polymer, conductive compound such as indium oxide, aluminum, palladium, gold or other metal or alloy coated, vapor deposited or laminated paper, plastic film, belt, etc. Can be mentioned.

Examples of the charge generating material used in the photosensitive layer include azo pigments, quinone pigments, perylene pigments, indigo pigments, thioindigo pigments, bisbenzimidazole pigments, phthalocyanine pigments, quinacridone pigments, Quinoline pigments, lake pigments, azo lake pigments, anthraquinone pigments, oxazine pigments, dioxazine pigments, triphenylmethane pigments, azurenium dyes, squarium dyes, pyrylium dyes,
Various organic pigments and dyes such as triallylmethane dye, xanthene dye, thiazine dye, and cyanine dye, and further amorphous silicon, amorphous selenium, tellurium,
Inorganic materials such as selenium-tellurium alloy, cadmium sulfide, antimony sulfide, zinc oxide and zinc sulfide can be mentioned.

These materials are dispersed and applied in a binder resin, or when formed as a layer other than the uppermost layer in the case of a laminated photosensitive layer, vacuum deposition, sputtering, CVD.
It can be formed into a film by a method such as a method and used for the photosensitive layer.

The charge-generating substance is not limited to those listed here, and may be used alone or in combination of two or more when used.

The charge-transporting substance is generally classified into two types, that is, a substance that transports electrons and a substance that transports holes, and both can be used in the electrophotographic photoreceptor of the present invention.

Examples of the electron transport substance include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone. , 9-dicyanomethylene-2,4,7-trinitrofluorenone, 9-dicyanomethylene-2,4,5,7
-Tetranitrofluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, tetranitrocarbazole chloranil, 2,3-
Dichloro-5,6-dicyanobenzoquinone, 2,4,7
-Trinitro-9,10-phenanthrenequinone, tetrachlorophthalic anhydride, organic compounds such as diphenoquinone derivatives, amorphous silicon, amorphous selenium, tellurium, selenium-tellurium alloy, cadmium sulfide, antimony sulfide, zinc oxide, zinc sulfide, etc. Inorganic materials may be mentioned.

As the hole-transporting substance, in the case of a low molecular weight compound, for example, pyrene, N-ethylcarbazole, N-isopropylcarbazole, N-phenylcarbazole,
Alternatively, N-methyl-2-phenylhydrazino-3-methylidene-9-ethylcarbazole, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, p-N, N-dimethylaminobenzaldehyde diphenylhydrazone, p Hydrazones such as -N, N-diethylaminobenzaldehyde diphenylhydrazone and p-N, N-diphenylaminobenzaldehyde diphenylhydrazone, 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1 -Phenyl-3- (p-diethylaminostyryl) -5- (p-
Pyrazolines such as diethylaminophenyl) pyrazolin, triphenylamine, N, N, N ′, N′-tetraphenyl-1,1′-diphenyl-4,4′-diamine, N, N′-diphenyl-N, N Examples include'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine and the like. Examples of the polymer compound include poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, pyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, ethylcarbazole- Formaldehyde resin, triphenylmethane polymer, polysilane, etc. may be mentioned.

The charge-transporting substance is not limited to those listed here, and may be used alone or in combination of two or more when used.

It is also possible to use additives such as a plasticizer, a sensitizer and a surface modifier together with these charge transport agents.

Examples of the plasticizer include biphenyl, biphenyl chloride, terphenyl, dibutyl phthalate, diethylene glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, polypropylene, polystyrene and various fluorohydrocarbons. Can be mentioned.

Examples of the sensitizer include chloranil, tetracyanoethylene, methyl violet, rhodamine B, cyanine dye, merocyanine dye, pyrylium dye and thiapyrylium dye.

Examples of the surface modifier include silicone oil and fluororesin.

Further, in the present invention, in order to improve the adhesiveness between the conductive support and the photosensitive layer and prevent the injection of free charges from the support to the photosensitive layer, a gap between the conductive support and the photosensitive layer is provided. In addition, an intermediate layer can be provided if necessary. Examples of materials used for these layers include aluminum oxide, silicon oxide, tin oxide, and titanium oxide, in addition to the polymer compounds used for the binder resin of the photosensitive layer. This adhesive layer or barrier layer can be formed by coating the above-mentioned materials on a conductive support, vacuum deposition, sputtering, CVD, or other means.

When the multi-layer type electrophotographic photoreceptor is formed by dip coating, a paint prepared by dissolving the above charge generating agent or charge transport substance in a binder resin or the like dissolved in a solvent is used. The solvent that dissolves is different depending on the type of binder resin, but is preferably selected from those that do not dissolve the lower layer. Specific examples of organic solvents include alcohols such as methanol, ethanol and n-propanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as N, N-dimethylformamide and N, N-dimethylacetamide. Ethers such as tetrahydrofuran, dioxane and methyl cellosolve; Esters such as methyl acetate and ethyl acetate; Sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane; Aliphatic halogenation such as methylene chloride, chloroform, carbon tetrachloride and trichloroethane hydrocarbon;
Benzene, toluene, xylene, monochlorobenzene,
Examples thereof include aromatics such as dichlorobenzene.

[0036]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. In the examples, "part" means "part by weight".

Example 1 A solution was prepared by dissolving 1 part of a polyamide resin (trade name "Amilan CM-8000" manufactured by Toray Industries, Inc.) in a mixed solvent consisting of 7 parts of methanol and 7 parts of n-butanol. By a dip coating method using this solution, a barrier layer having a film thickness after drying of 1 μm was provided on the outer peripheral surface of an aluminum drum having a diameter of 30 mm and a length of 260 mm.

Next, 5 parts of α-type titanyl phthalocyanine,
5 parts of butyral resin (trade name "ESREC BL-1" manufactured by Sekisui Chemical Co., Ltd.) and 190 parts of methylene chloride were mixed, and a coating for forming a charge generation layer was obtained using a vibration mill. A charge generation layer having a thickness of 0.4 μm after drying was formed on the barrier layer by a dip coating method using this coating material.

Further, a formula that is a hole-transporting substance

[0040]

[Chemical 5]

10 parts of a hydrazone compound represented by the formula

[0042]

[Chemical 6]

10 parts of a polyarylate resin represented by the formula (n = about 200, trade name "ISARYL25S" manufactured by ISONOVA) and 1 part of 2,6-di-tert-butyl-p-cresol were dissolved in 80 parts of dioxane. The obtained coating material for forming the charge transport layer was obtained. An electrophotographic photosensitive member was obtained by forming a charge transport layer having a film thickness after drying of 20 μm on the charge generation layer by a dip coating method using this coating material.

(Example 2) In Example 1, 2,6-di-tert-butyl-forming the coating material for forming the charge transport layer
An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that the amount of p-cresol used was 0.1 part.

(Example 3) In Example 1, instead of the hydrazone compound constituting the coating material for forming the charge transport layer,
formula

[0046]

[Chemical 7]

An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that 10 parts of the benzidine compound (hole-transporting substance) represented by

Comparative Example 1 An electrophotographic photosensitive member was obtained in the same manner as in Example 1, except that the cresol compound was not used.

(Comparative Example 2) In Example 1, the polyarylate resin "ISA" constituting the coating material for forming the charge transport layer was prepared.
An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that polycarbonate Z resin (trade name "Upilon Z-200" manufactured by Mitsubishi Gas Chemical Co., Inc.) was used instead of "RYL25S".

(Comparative Example 3) In Example 1, the polyarylate resin "ISA" constituting the coating material for forming the charge transport layer was prepared.
An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that a general polyarylate resin (trade name "U-Polymer U100" manufactured by Unitika Ltd.) was used instead of "RYL25S".

(Evaluation) The printing durability of the drum-shaped electrophotographic photoreceptors obtained in each of the examples and each comparative example was evaluated by using a commercially available laser printer (trade name "LBP-8II" manufactured by Canon Inc.). .

The test method was as follows: A prototype electrophotographic photosensitive member was mounted on an EP cartridge of a laser printer, continuous printing was performed while toner was replenished, the image condition was evaluated, and the initial film thickness of the photosensitive layer was evaluated. The thickness of the photosensitive layer after the printing durability test was measured, and the amount of wear was calculated from the difference.

Table 1 shows a list of evaluation results at the initial stage and after the printing test on 30,000 sheets.

[0054]

[Table 1]

As is clear from the above table, Examples 1 and 3 in which 10% by weight of the cresol compound was added to the resin.
Compared with the electrophotographic photoconductor of Comparative Example 1 in which the electrophotographic photoconductor of No. 1 was not added, the amount of abrasion of the photosensitive layer was slightly increased, but the image characteristics were almost the same as those in the initial stage even after the printing test.
It showed excellent printing durability. The electrophotographic photoreceptor of Example 2 in which the addition amount of the cresol compound was 1% by weight had almost the same wear amount as that of Comparative Example 1, but the image characteristics were changed only by a slight decrease in print density. The characteristics were sufficiently practical.

On the other hand, the electrophotographic photosensitive member of Comparative Example 1 to which the cresol compound was not added had excellent abrasion resistance because it used the polyarylate resin of the present invention, but the image after the 30,000-sheet printing test was tested. There was a so-called image deletion phenomenon in which the image was blurred in the circumferential direction.

Further, even if the cresol compound was added, the electrophotographic photoreceptor of Comparative Example 2, which used a general polycarbonate Z resin for electrophotographic photoreceptors, was inferior in abrasion characteristics, and therefore 30,000 sheets were printed. In the image after the test, defects due to abrasion of the photosensitive layer were clearly developed.

Similarly, the electrophotographic photosensitive member of Comparative Example 3 using a conventionally known general-purpose polyarylate resin shows a slight improvement in the amount of wear, but the chargeability is inferior from the initial stage, which is the cause. A background stain was observed on the image, and the tendency became more remarkable in the printing durability test.

As is clear from these results, it is clear that the combination of the polyarylate resin of the present invention and the cresol-based compound shows a remarkable improvement in printing durability, and that of Examples 1 and 2. From the results, it can be understood that the optimum addition amount of the cresol compound is in the range of 1 to 10% by weight with respect to the resin.

[0060]

The electrophotographic photosensitive member of the present invention contains a polyarylate resin represented by the general formula (I) and a cresol compound represented by the general formula (II) on a conductive support. It has both durability and stability suitable for repeated use in an electrophotographic apparatus.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of an electrophotographic photoreceptor of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor of the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor of the present invention.

FIG. 4 is a schematic cross-sectional view showing an example of the layer structure of the electrophotographic photosensitive member of the present invention.

[Explanation of symbols]

 1 Conductive Support 2a Photosensitive Layer 2b Photosensitive Layer 2c Photosensitive Layer 2d Photosensitive Layer 3 Charge Generating Material 4 Binder 5 Charge Transporting Material 6 Charge Generating Layer 7 Charge Transporting Layer

Claims (3)

[Claims] 1. In an electrophotographic photoreceptor comprising a photosensitive layer containing a photoconductive substance and a binder resin on a conductive support, the binder resin of the photosensitive layer is represented by the general formula (I): 1] (In the formula, the hydrogen atom on the aromatic ring may be substituted with a halogen atom, an aliphatic group which may have a substituent, or a carbocyclic group which may have a substituent, and n is 10-100
Represents an integer between 0. ) Containing a polyarylate having a structural unit represented by the formula (1) and having a general formula (II) (Wherein R ¹ and R ² represent a hydrogen atom, an aliphatic group which may have a substituent, or a carbocyclic group which may have a substituent). A photoreceptor for electrophotography, which comprises a cresol-based compound contained therein. 2. A cresol-based compound is 2,6-di-te.
The electrophotographic photoreceptor according to claim 1, which is rt-butyl-p-cresol. 3. The electrophotographic photoreceptor according to claim 1, wherein the proportion of the cresol compound used is in the range of 1 to 10% by weight of the binder resin.