JPS6221156A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a laminate type electrophotographic sensitive body extremely high in sensitivity by using a specified polycyclic quinone type pigment in an electrostatic charge generating layer as a charge generating material and a specified hydrazone type compound for a charge transfer layer. CONSTITUTION:The charge generating layer is formed by coating a substrate with the polycyclic quinone type pigment represented by formula (I) as the charge generating material, when needed, together with the charge transfer material and a proper binder, or depositing said pigment film with a vacuum vapor deposition device. The charge transfer layer is electrically connected with the charge generating layer and has a function of receiving charge carriers injected from the charge generating layer in the presence of an electric field and transferring them to the surface. The material for transferring the charge carriers in the charge transfer layer is substantially insensitive to the electromagnetic waves of the wavelength region to which the charge generating layer is sensitive, and the hydrazone type compounds represented by formula (II) are used for it, and that can be added to the charge generating layer, permitting that sensitization effect to be more distiguished.

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, a number of organic photoconductors have been developed. carbazole,
Low-molecular organic photoconductors such as anthracene, pyrazolines, oxadiazoles, hydrazones, polyarylalkanes, phthalocyanine pigments, a, zo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indigo dyes, Organic pigments and dyes such as thioindigo dyes and methine squaric acid 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. Photoconductive organic pigments and dyes have been proposed.

For example, US Patent No. 4,123,270.

Same No. 4247614, Same No. 4251613, Same No. 4
No. 251614, No. 4256821.

Same No. 4260672, Same No. 4268596.

As disclosed in 4278747 and 4293628, an electrophotographic photosensitive material using a disazo pigment exhibiting photoconductivity as a charge generation substance in a photosensitive layer that is mechanically separated into a charge generation layer and a charge transport layer. The body is known.

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 □ is less sensitive than other single layer photoconductors due to increased sensitivity and residual potential after durability tests. Although it was advantageous, it was still not at a sufficient level.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and 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 non-based pigment in the generation layer and having a specific hydrazone compound in the charge transport layer.

[Means for solving problems]

The present invention provides a multilayer 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 composed of a layer containing a polycyclic non-based pigment represented by formula (I). The charge transport layer has the general formula (II) /ゝ, 3R4 (wherein R1 and R2 are hydrogen atoms, halogen atoms,
It represents a nitro group, a substituted or unsubstituted 7-aryloxy group, or a substituted or unsubstituted 7-mino group. However, R1 and R
At least one of 2 is a substituted amino group or an alkoxy group. R3 and R4 represent a substituted or unsubstituted alkyl group or a substituted or unsubstituted 7-aryl group, provided that at least one of R3 and R4 is a substituted or unsubstituted 7-aryl group. Further, R3 and R4 may form a nitrogen-containing heterocycle, and R5R6R7 and R8 are a hydrogen atom, a halogen atom, or a nitro group.

A layer containing a hydrazone compound represented by (representing a substituted or unsubstituted alkyl group, an alkoxy group-substituted or unsubstituted 7-aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted amine group) This is an electrophotographic photoreceptor characterized by the following.

The present invention will be explained in detail below.

In the laminated electrophotographic photoreceptor of the present invention, the 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 QII layer with 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. This is due to the need to generate a large number of charge carriers and to inject the generated charge carriers into the charge transport layer without being deactivated by recombination or trapping.

The charge generating material used in the present invention is a polycyclic pigment represented by formula CI).

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

The binder that can be used when 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 80
Weight % or less, preferably 40 weight % or less is suitable.

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 methanol, ethanol,
Alcohols such as Impropatool, ketones such as acetone, methyl ethyl ketone, cyclohexanone, N, N
- Amides such as dimethylformamide and N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform, methylene chloride, Aliphatic halogenated hydrocarbons such as dichloroethylene, carbon tetrachloride, trichlorethylene, etc., or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used.

Coating methods include dip coating, spray coating, spinner coating, bead coating,
This can be carried out using a coating method such as a Mayer bar coating method, a blade coach ink method, a roller coach ink method, or a curtain coating method. Drying is
A preferred method is 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" includes a broad definition of "light rays" that includes gamma 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 layers trap each other, resulting in a decrease in sensitivity.

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

(In the formula, R1 and R2 represent 1. a hydrogen atom, a halogen atom, a nitro group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted amino group, provided that R]
and R2, at least one of which is a substituted amino group or an alkoxy group. R3 and R4 represent a substituted or unsubstituted alkyl group or a substituted or unsubstituted heptadyl group, provided that at least one of R3 and R4 is a substituted or unsubstituted aryl group. Further, R3 and R4 may form a nitrogen-containing heterocycle. Rs R6Rr and R
8 represents a hydrogen atom, a halogen atom, a nitro group, a substituted or unsubstituted alkyl group, an alkoxy group-substituted or unsubstituted aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted amino group.) 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.

Table 1a Table 1b Furthermore, 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 transporting material to the charge generation layer, the hydrazone compound should be 10 times or less (weight ratio), preferably 0.01-1 times (weight ratio) of the charge generation material to achieve high sensitivity, low residual potential,
This is appropriate from the viewpoint of repeat 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.

The charge transport layer cannot be made thicker than necessary because there is a limit to its ability to transport charge carriers. Generally, the thickness is 5 to 30 microns, but the preferred range is 8 to 20 microns. be. 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. The substrate having a conductive layer is one which itself has conductivity, such as aluminum, aluminum alloy, copper, and zinc.

Stainless steel, vanadium, molyftene, chromium, titanium, nickel, indium, gold, platinum, etc. can be used, and in addition, aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc. can be coated by vacuum evaporation method. A substrate in which a plastic having a formed layer (e.g. carbon black, silver particles, etc.) is coated on a plastic together with a suitable binder, a substrate in which plastic or paper is impregnated with conductive particles, a plastic having a conductive polymer, etc. are used. I can do this.

A subbing layer having a function of simply adhering the barrier 1 can also be provided between the conductive layer and the photosensitive layer. The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, nylon 66,
Nylon 810, copolymerized nylon, alkoxymethylated nylon, etc.), 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 directly fixed, or the toner image can be transferred to paper, plastic film, etc. and then developed and fixed.

Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, and then visually imaged and fixed. 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 is a hole transport material, the surface of the charge transport layer must be negatively charged.

After charging, when exposed to light, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer, and then reach the surface and neutralize the negative charge, causing a decrease in the surface potential and static electricity between the exposed area and the unexposed area. Electrocontrast occurs.

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 subject to deterioration due to ultraviolet rays, oran, etc., stains due to oil, etc., scratches due to chips such as full bending, and damage to the photoreceptor due to photoreceptor contact members such as developing members, transfer members, and cleaning members. In order to form an electrostatic latent image on this protective layer, a protective layer may be further provided on the charge generation layer or the charge transport layer for the purpose of preventing scratching.
It is desirable that the surface resistivity is equal to or higher than lQI+Ω.

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 An ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 ml of water) was coated on an aluminum cylinder by a coating method, dried, and coated i1. A subbing layer of og/m'' was formed.

Next, 1 part by weight of a charge generating material represented by formula (I), 1 part by weight of butyral resin (S-LEC BM-2: manufactured by M Suikagaku ■)
Parts by weight and 30 parts by weight of isopropyl 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 0.3 mm.
1 ffi part of the hydrazone compound (1), 1 part by weight of polysulfone resin (P1700, manufactured by Union Carbide), and 6 parts by weight 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 is 1
There were 2 bowls.

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 v5). The sensitivity is determined by the amount of exposure (El/
The evaluation was made by measuring the 2 viscosity (ux*5ec).

These results were as follows.

Vo: -590 volts Vs: -580 volts El/2: 3.61 uxmsec Example 2~
5 Example 1 except that the compounds shown in Table 1 were used in place of the compound No. (1) used in Example 1.
A photoreceptor was prepared in exactly the same manner as described above, and the characteristics of this photoreceptor were measured. These results are shown in Table 2.

Table 2 Example Compound! riVo(-V) V5(-V) E
l/2nut・5ec 2 2 5805653.3 3 3 5755603.5 4 4 5905803.4 5 5 6005903.8 Comparative Examples 1 to 6 The charge transport substances shown in Table 3 were used in place of the hydrazone compound used in Example 1. A photoreceptor was produced in exactly the same manner except for the following. The charging characteristics are shown in Table 4.

Table 3 Comparative Example Comparative Charge Comparative Charge Transport Material Structural Formula % Formula % Comparative Example Comparative Charge Comparative Charge Transport Material Structural Formula Transport Substance Table 4 Comparative Example Comparative Charge Vo (-V) V5 (-V) E
5ec in l/2 transport substance No lux
As is clear from the results of the examples and comparative examples, the laminated photoreceptor of the present invention It can be seen that a photoreceptor with extremely high sensitivity was obtained compared to photoreceptors No. 1 to No. 6 of the comparative example. 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, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted amino group. However, R_
At least one of 1 and R_2 is a substituted amino group or an alkoxy group. R_3 and R_4 represent a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group. However, at least one of R_3 and R_4
One is a substituted or unsubstituted aryl group. Also R_
3 and R_4 may form a nitrogen-containing heterocycle. R_5R
_6R_7 and R_8 are hydrogen atoms, halogen atoms,
It represents a nitro group, a substituted or unsubstituted alkyl group, an alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted 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).