JPS6219870A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain high sensitivity and excellent durability by using a specific polycyclic quinone pigment as an electric charge generating material for an electric charge generating layer and incorporating a specific hydrazone compd. into an electric charge transfer layer. CONSTITUTION:The polycyclic quinone pigment expressed by the formula I is incorporated into the charge generating layer of a lamination type photosensitive layer provided on a conductive base and the hydrazone compd., expressed by the formula II [R1, R2 are H, halogen atom, nitro or (un)substd. aryl or oxy, where at least one of R1, R2 is a substd. amino or alkoxy; R3, R4 are an (un)substd. alkyl or aryl, where at least one of R3, R4 is an (un)substd. aryl; R3 and R4 may form a nitrogenous heterocyclic ring; R5-R8 are H, halogen atom, nitro alkoxy, (un)substd. alkyl, aryloxy, acyl or amino] is incorporated into the charge transfer layer. The hydrazone compd. expressed by the formula II is preferably added to the charge generating layer. Such laminated type photosensitive body has the high sensitivity and provides the excellent image even after many times of uses.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an organic photoconductor, and particularly to an electrophotographic photoreceptor having a charge transport layer and a charge generation layer.

[Conventional technology]

Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components have been known so far.

On the other hand, since the discovery that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed. For example, organic photoconductors such as poly-N-vinylcarbazole and polyvinylanthracene? rimmer, carbazole,
Low-molecular organic photoconductors such as anthracene, pyrazolines, oxadiazoles, hydrazones, polyarylalkanes, 7-thalocyanine pigments, azo pigments, cyanine dyes, polycyclic quinone pigments, du-lene pigments, indigo dyes, Organic pigments and dyes such as thioinsogo dyes and methine squarate dyes are known. In particular, organic pigments and dyes with photoconductivity are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has been expanded.
Many photoconductive organic pigments and dyes have been proposed.

For example, US Pat. No. 4,123,270, US Pat. No. 42,476
No. 14, No. 4251613, No. 4251614, No. 4256821, No. 4260672, No. 4268596, No. 4278747, No. 429
As disclosed in Japanese Patent No. 3628, electrophotographic photoreceptors are known that use a sosazo pigment exhibiting photoconductivity as a charge generation substance in a photosensitive layer that is functionally separated into a charge generation layer and a charge transport layer.

Electrophotographic photoreceptors using such organic photoconductors can be produced by coating by appropriately selecting a binder, so it is possible to provide photoreceptors with extremely high productivity and at low cost. It has the advantage of being able to freely control the sensitive wavelength range.

A multilayer photoconductor obtained by laminating a charge transport layer and a charge generation layer mainly composed of a charge generation material has advantages over other single-layer photoconductors in terms of sensitivity and increased residual potential after durability tests. However, it was still not at a sufficient level.

[Problems to be Solved by the Invention] An object of the present invention is to improve the above-mentioned drawbacks and to provide a laminated electrophotographic photoreceptor with high sensitivity and extremely low residual potential even after a durability test.

The present invention aims to achieve the above object in a laminated electrophotographic photoreceptor having two layers, a charge generation layer containing a charge generation material as a main component and a charge transport layer containing a charge transport material as a main component, on a conductive support. This is achieved by using a specific polycyclic quinone pigment in the generation layer and a specific hydrazone compound in the charge transport layer.

[Means for solving problems]

The present invention provides a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, in which the charge generation layer is comprised of a layer containing a polycyclic quinone pigment represented by formula (1). , the charge transport layer may have the general formula (II) (wherein R and R2 are hydrogen atoms), so it may have a rhodane atom, a nitro group, or an aryloxy group,
Indicates an alkoxy group or a substituted amino group. However, at least one of L%R1 and R2 is a substituted amine group or an alkoxy group. R3 and R4 represent an alkyl group or an aryl group which may have a substituent. However, R5e R4
At least one of them is an aryl group. Further, R3 and R4 may be taken together to form a nitrogen-containing heterostructure mt-. R5'R6' R7 and R8 each represent a hydrogen atom, a nitro group, an alkyl group that may have a substituent, an alkoxy group, an aryloxy group, an acyl group, or an amino group. This is an electrophotographic photoreceptor characterized by comprising a layer containing a hydrazone compound.

The present invention will be explained in detail below.

In the laminated electrophotographic photoreceptor of the present invention, one charge generation layer contains as much charge generation material as possible in order to obtain sufficient absorbance, and efficiently injects generated charge carriers into the charge transport layer. Therefore, it is desirable to use a thin film layer, for example, a thin film layer having a thickness of 10 microns or less, preferably 0.01 micron to 1 micron. This means that
Most of the incident light is absorbed by the charge generation layer to generate many charge carriers, and the generated charge carriers must be injected into the charge transport layer without being deactivated by recombination or trapping. It is caused by something.

The charge generating material used in the present invention is a multiwave quinone pigment represented by formula (1).

The charge generation layer can be formed by coating the above-mentioned pigments and, if necessary, a charge transporting material together with a suitable binder (or without a binder) on the substrate, or can be formed by vacuum deposition or
can be obtained by forming .

The binder that can be used in forming the charge generating layer by coating can be selected from a wide variety of insulating resins, and can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and heptalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin,
polyamide, polyvinylpyridine, cellulose resin,
Examples include insulating resins such as urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. - The resin contained in the charge generation layer is SO
It is suitable to have a diameter of N or less, preferably 40 or less.

The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the underlying charge generation layer or undercoat layer. Specific organic solvents include alcohols such as methanol, ethanol, isopro/methanol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, amides such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl Sulfoxides such as sulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate, aliphatic halodane such as chloroform, methylene chloride, dichloroethylene, tetrachloride carbon, trichlorethylene, etc. Hydrocarbons or aromatic compounds such as benzene, toluene, xylene, ligroin, monochlorobenzene, and sochlorobenzenate can be used.

Coating methods include dip coating method, spray footing method, spinner coating method, peed coating method,
This can be carried out using a coating method such as a Mayer coating method, a blade coating method, a roller coating method, or a curtain coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying can be carried out at 30° C. to 200° C. for a period of 5 minutes to 2 hours, either stationary or with air blowing.

The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving and taking charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. have. At this time, this charge transport layer may be laminated on or under the charge generation layer.

The substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as charge transport substance) is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. The term "electromagnetic waves" used herein includes the broad definition of "light rays" including r-rays, X-rays, far-infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps that of the charge generation layer, charge carriers generated in both trap each other, resulting in a decrease in sensitivity.

The charge transport material used in the present invention is a hydrazone compound represented by the general formula (It).

R, R4 (in the formula R1+ R2, R3r R4* R5, R6r
R7*RB is as described above) Here, the alkoxy group is preferably an alkoxy group having a lower alkyl. Examples of the a-substituted amine group include dimethylamino, diethylamine, and sobensolamino. The alkyl group is preferably lower alkyl;
Aryl groups include phenyl, diphenyl, naphthyl and the like.

Examples of the nitrogen-containing heterocycle include pyrrolidino, piperidino, and morphorno. Furthermore, the alkyl group, aryl group, aryloxy group, acyl, and amine group may be further substituted with other substituents such as halogen, alkyl, and aryl.

This hydrazone compound satisfies the above-mentioned conditions as a charge transport material, and has excellent properties particularly in terms of sensitivity and durability.

Table 1 shows typical hydrazone compounds represented by the general formula (II) used in the present invention.

Further, in the present invention, the above-mentioned hydrazone compound used in the charge transport layer can be added to the charge generation layer, and the sensitizing effect thereof becomes even more remarkable.

When adding a charge transport substance to the charge generation layer, the hydrazone compound should be 10 times (weight ratio 9 or less, preferably 0.01 to 1 times (weight ratio)) as high sensitivity, low residual potential, and
This is appropriate from the viewpoint of repeated stability.

To form a charge transport layer containing a hydrazone compound, a film can be formed by selecting an appropriate binder. Resins that can be used as binders include, for example, acrylic resins, polyacrylates, polyesters, polycarbonates, polystyrene, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers,
Examples include insulating resins such as polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, and chlorinated rubber, and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene.

Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Typically it is 5 microns to 30 microns, with a preferred range of 8 microns to 20 microns. When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer, that is, a conductive support. As the substrate having the conductive layer, materials that are conductive themselves such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum can be used. In addition, 7" plastics (for example, carbon black,
For example, a substrate in which glass particles (silver particles, etc.) are coated on glass with a suitable binder, a substrate in which glass, glue or paper is impregnated with conductive particles, a plastic having a conductive polymer, etc. can be used.

A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer. Subbing layer, casein,
Polyvinyl alcohol, nitrocellulose, ethylene-
It can be formed from acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, nylon 66, nylon 61ol copolymerized nylon, alkoxymethylated nylon, polyurethane, gelatin, aluminum oxide, etc.).

The thickness of the undercoat layer is suitably 0.1 micron to 40 micron, preferably 0.1 micron to 3 micron.

When using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, and the charge transport material in the charge transport layer is composed of an electron transport material, the surface of the charge transport layer must be positively charged; When exposed to light after being charged, electrons generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the surface to neutralize the positive charge, causing a decrease in surface potential and creating static electricity between the exposed area and the unexposed area. Contrast occurs. A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. This can be fixed directly, or the toner image can be transferred to paper or plastic film, developed and fixed. Also, the electrostatic latent image on the photoreceptor can be transferred to the insulating layer of transfer paper, and then the visual image can be fixed. There are also ways to make it stick. The type of developer, the developing method, and the fixing method may be any known ones or known methods, and are not limited to specific ones.

On the other hand, when the charge transport material consists of a hole transport material, the surface of the charge transport layer must be negatively charged, and when exposed to light after charging, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. , which then reaches the surface and neutralizes the negative charges, resulting in attenuation of the surface potential and an electrostatic contrast between the surface potential and the unexposed area.

During development, it is necessary to use a positively charged toner, contrary to the case where an electron transport material is used.

The electrophotographic photoreceptor according to the present invention is susceptible to deterioration due to ultraviolet rays, ozone, etc., dirt from oil, etc., scratches from metal chips, etc., damage to the photoreceptor due to photoreceptor contact members such as developing members, transfer members, cleaning members, etc. A protective layer may be further provided on the charge generation layer or the charge transport layer for the purpose of preventing scratching. To form an electrostatic latent image on this protective layer,
It is desirable that the surface resistivity is 10 Ω or more.

The protective layer used in the present invention is made of resin such as polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer, etc. It can be formed by applying a solution dissolved in an appropriate organic solvent onto the photosensitive layer and drying it.

Moreover, additives such as ultraviolet absorbers can be added to the resin liquid. At this time, the thickness of the protective layer is generally 0.05~
20 microns, particularly preferably in the range 0.2 to 5 microns.

Hereinafter, the present invention will be explained according to examples.

Example 1 Aqueous ammonia solution of casein (casein 11.2.li', 28% ammonia water 1
g, water 222d) by a coating method, and dried to obtain a coating amount of 1. A subbing layer of OVm was formed.

Next, 1 part by weight of the charge generating substance represented by formula (1), butyral resin (S-LEC BM-2: manufactured by Sekisui Chemical Co., Ltd.)
1 part by weight and 30 parts by weight of innorobil alcohol were dispersed for 4 hours using a ball mill disperser. This dispersion was applied onto the previously formed subbing layer by a dip coating method and dried to form a charge generating layer.

The film thickness at this time was 0.3μ. Next, 1 part by weight of a hydrazone compound from Compound Shop (1) in Table 1, 1 part by weight of polysulfone resin (P1700 manufactured by Union Carbide Co., Ltd.), and 6 m-ffi parts of monochlorobenzene were mixed and dissolved by stirring with a stirrer. This liquid was applied onto the charge generation layer by dip coating and dried to form a charge transport layer.

The film thickness at this time was 13μ.

A corona discharge of 15 kV was applied to the photoreceptor thus prepared. The surface potential at this time was measured (initial potential Vo).

Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 5 seconds (dark decay Vs).The sensitivity was determined by the amount of exposure required to attenuate the potential v5 to 1/2 after dark decay (E1 /2
The evaluation was made by measuring 1ux·see).

These results were as follows.

Vo: -610 Volt v5: -6007 JS Ruto El/2:
5.71 ux-sec Examples 2 to 7 A photoreceptor was prepared in exactly the same manner as in Example 1, except that the compounds shown in Table 1 were used in place of the compound used in Example 1 & the compound (1). was prepared and the characteristics of this photoreceptor were measured. These results are shown in Table 2.

Table 2 Example Compound A, VO(-V) Vs(-V)
El/21ux misery 5ec 2 2 6005905.6 3 3 6005856.2 4 4 6106005.9 5 5 6206106.5 6 6 5955856.7 7 7 5905806.9 Comparative Examples 1 to 6 In place of the hydrazone compound used in Example 1 Photoreceptors were prepared in exactly the same manner except that the charge transport materials shown in Table 3 were used. The charging characteristics are shown in Table 4.

Table 3 Comparative Example Comparison Charge Comparative Charge Transport Substance Structural Formula Comparative Example Comparison Charge Comparison Charge Transport Substance Structural Formula Transport Substance Table 4 1 1 605 580 7.8 2 2 600 580 7.4 3 3 610 585 7.9 4 4 620 600 8.3 5 5 610 585 8.0 6 6 600 580 7.8 As is clear from the results of Examples and Comparative Examples, the laminated photoreceptor of the present invention was different from the photoreceptors A1 to 711L6 of Comparative Examples. By comparison, it can be seen that a photoreceptor with extremely high summer sensitivity was obtained. Furthermore, the photoreceptors of Examples 1 to 3 were used in a copying machine (NP-150z:
(manufactured by Canon Inc.) to produce an image of 20,000
Repeated several times. As a result, good quality images were obtained for all photoreceptors even after repeating 20,000 times. As a result, it can be seen that the photoreceptor of the present invention has extremely excellent durability.

〔Effect of the invention〕

As is clear from the above, the present invention uses a specific polycyclic quinone pigment as a charge generation material in the charge generation layer and a specific hydrazone compound in the charge transport layer, thereby achieving extremely high sensitivity compared to conventional ones. This made it possible to provide a high-quality laminated electrophotographic photoreceptor.

Claims (2)

[Claims] (1) In a laminated photographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge generation layer has the formula (
I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼It consists of a layer containing a polycyclic quinone pigment represented by (I), and the charge transport layer is the general formula (II).▲There are mathematical formulas, chemical formulas, tables, etc.▼(II ) (In the formula, R_1 and R_2 represent a hydrogen atom, a halogen atom, a nitro group, an aryloxy group that may have a substituent, an alkoxy group, or a substituted amino group, provided that R_
At least one of 1 and R_2 is a substituted amino group or an alkoxy group. R_3 and R_4 represent an alkyl group or an aryl group that may have a substituent. However, at least one of R_3 and R_4 is an aryl group. Further, R_3 and R_4 may be combined to form a nitrogen-containing heterocycle. R_5, R_6, R_7 and R_8
Each represents a hydrogen atom, a halogen atom, a nitro group, an alkyl group which may have a substituent, an alkoxy group, an aryloxy group, an acyl group or an amino group. ) An electrophotographic photoreceptor comprising a layer containing a hydrazone compound represented by: (2) The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer contains a hydrazone compound represented by formula (II).