JPS627053A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity and to improve durability by incorporating a specified polycyclic quinone type pigment in an electrostatic charge generating layer and a specified hydrazone type compound in a charge transfer layer. CONSTITUTION:The charge generating layer containing the polycyclic quinone type pigment represented by formula I and the charge transfer layer containing the hydrazone type compound represented by formula II (each of R1-R4 is optionally substituted alkyl or aryl or an atomic group necessary to form a 5- or 6-membered ring together with the N atom; each of R5 and R6 is H, halogen, nitro, optionally substituted alkyl, aryloxy, acyl, amino, or alkoxy; an R is a divalent organic residue) are laminated on a conductive substrate. The additions of said pigment to the charge generating layer and said hydrazone type compound to the charge transfer layer permit the obtained photosensitive body to be enhanced in photosensitivity and further, the addition of said hydrazone type compound to the charge generating layer permits the sensitizing effect to be made more remarkable, residual potential to be lowered, and stability against repeated uses to be improved.

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 generation layer and a charge transport layer.

[Prior Art] Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide as photosensitive components have been known. On the other hand, since the discovery that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed.For example, organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene. , carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, polyaryl alkanes, and other low-molecular organic photoconductors, phthalocyanine pigments, azo pigments, cyanine pigments, polycyclic quinone pigments, perylene pigments, and indigo dyes. Organic pigments and dyes such as , thioindigo dyes and squaric acid methine dyes are known. In particular, organic pigments and dyes with high conductivity are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has been expanded. Conductive organic pigments and dyes have been proposed. For example, U.S. Pat. Nos. 4,123,270 and 4,247.
No. 614, No. 4251613, No. 4251614
No. 4256821, No. 4260672, No. 4268596, No. 4278747, No. 42
As disclosed in Japanese Patent No. 93628, etc., electrophotographic photoreceptors are known that use a photoconductive disazo pigment as a charge generation substance in a photosensitive layer that is functionally separated into a charge generation layer and a charge transport layer. An electrophotographic photoreceptor using such an organic photoconductor can be produced by coating by selecting an appropriate binder, so it is possible to provide a photoreceptor with extremely high productivity and 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.

[Means and effects for solving the problems] The present invention achieves the above object by forming 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 charge generation layer and a specific hydrazone compound in the charge transport layer in a laminated electrophotographic photoreceptor having two layers.

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 of structural formula (I), The charge transport layer is made of hydrazo (
In the formula, Ro and R represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted 7-aryl group, or an atomic group necessary to complete a 5-membered ring or a 6-membered ring together with t±nitrogen atom, R, and tortoise indicate a group of atoms necessary to complete a 5- or 6-membered ring together with substituted aromatic or t±unsubstituted alkyl group, substituted or unsubstituted aryl group, or nitrogen atom, R5 and R.

represents a hydrogen atom, a halogen atom, a nitro group, a substituted or unsubstituted alkyl group, an alkoxy group, a substituted or unsubstituted 7-aryloxy group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted 7-mino group, R represents a divalent organic residue).

The present invention will be explained in detail below.

In the A-layer type 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. For example, the ailli layer, e.g. 1
It is desirable that the B film layer has a thickness of 0 g or less, preferably 0.01 to 1 p. This means that most of the incident light is absorbed by the charge generation layer and many charge carriers are generated. Furthermore, this is due to the fact that the generated charge carriers need to be injected into the charge transport layer without being deactivated by recombination or trapping.

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

The charge generation layer can be formed by coating the above-mentioned pigment and, if necessary, a charge transport material together with a suitable binder (or without a binder) on a substrate, and then forming a vapor-deposited film using a vacuum vapor deposition device. You can get it by doing this. 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. Preferred are polyvinyl butyral, polyarylate (11 polymers of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane resin, and epoxy resin. Examples include insulating resins such as resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer Φ is 8
A content of 0% by weight or less, preferably 40% by weight or less is suitable. Solvents that dissolve these resins vary depending on the type of resin, and are preferably selected from those that do not dissolve the underlying charge transport layer or subbing layer.Specific organic solvents include methanol, ethanol, and in-propyl alcohol. Alcohols such as tools, ketones such as acetone, methyl ethyl ketone, cyclohexanone, amides such as N,N-dimethylpolamide, N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, ethylene glycol Ethers such as monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, trichloroethylene, benzene, toluene, xylene, ligroin, Aromatic compounds such as monochlorobenzene and dichlorobenzene can be used.

Coating methods include dip coating method, spray coating method, spinner coating method, bead coach ink method,
This can be carried out using a coating method such as a Mayer bar coating method, a blade coating method, a roller coach ink method, or a curtain coating method.

Drying is preferably carried out by drying to the touch at room temperature, followed by heat drying. Heat drying can be carried out at a temperature of 30 to 200°C for a period of 5 minutes to 2 hours, either still or under blowing air.

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. In this case, this charge transport layer may be laminated on or under the charge generation layer, and is a substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as a charge transport material). is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive.

The term "electromagnetic waves" as used herein includes the broad definition of "light rays" including γ-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 has the general formula (II)
It is a hydrazone compound represented by

In the formula, R1 and R represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or an atomic group necessary to complete a 5-membered ring or a 6-membered ring together with a nitrogen atom, and R3 and R4 are substituted or an unsubstituted alkyl group, a substituted or unsubstituted 7-aryl group, or an atomic group necessary to complete a 5- or 6-membered ring together with a nitrogen atom; R is a divalent organic residue; shows.

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

Typical hydrazone compounds used in the present invention are illustrated below.

Further, in the present invention, the above-mentioned hydrazone compound used in the charge transport layer can be added to the charge generation layer.
The sensitizing effect becomes even more remarkable. When a charge transporting material is added to the charge generation layer, the hydrazone compound is 10 times or less (weight ratio) of the charge generation material, preferably 0.01
~1 times (weight ratio) is suitable from the viewpoint of high sensitivity, low residual potential, and repetition 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 resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, etc. resin or poly-
Mention may be made of organic photoconductive polymers such as N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. Since the charge transport layer has a limit to its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, the thickness is 5 to 30 μl, but the preferred range is 8 to 30 μl.
It is 20g. 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. Examples of the substrate having a conductive layer include those whose substrate itself is conductive, such as aluminum, aluminum alloy, copper, zinc,
Stainless steel, vanadium, molybdenum, 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 layer of plastic (e.g. polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluoroethylene, etc.) with a formed layer, conductive particles (e.g. carbon black, silver particles, etc.) on top of the plastic with a suitable binder. A substrate coated with a conductive material, a substrate made of plastic or paper impregnated with conductive particles, a plastic containing 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. The undercoat layer is casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin. , aluminum oxide, etc. The thickness of the undercoat layer is 0.1 to 40.
, preferably 0.1 to 3 wells.

When using a photoconductor having a conductive layer, a charge generation layer, and a charge transport layer in this order, and the charge transport material in the charge transport layer is an electron transport material, it is necessary to positively charge the surface of the charge transport layer. 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 and neutralize the positive charge, causing a decrease in surface potential and static electricity between the exposed area and the unexposed area. Electrocontrast occurs.

A visible image is 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 methods, and are not limited to specific ones or methods.

On the other hand, when the charge transport material is a hole transport material, it is necessary to charge the surface of the charge transport layer negatively, 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 charge, resulting in an attenuation of the surface potential and an electrostatic contrast with 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., and damage to the photoreceptor due to photoreceptor contact members such as developing members, transfer members, and cleaning members. A protective layer may be further provided on the charge generation layer for the purpose of preventing scratching.In order to form an electrostatic latent image on this protective layer, a surface resistivity of 101 is required.
The protective layer used in the present invention is preferably made of polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene.
It can be formed by dissolving a resin such as butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer or the like in a suitable organic solvent and coating the photosensitive layer on 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 to 20 JL, preferably 0.2
~5μ range.

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

Example 1 An ammonia aqueous solution of casein (1.2 g of casein I, 28% ammonia Ig, 222 ml of water) was coated on an aluminum cylinder using a dip coating method, and dried to a coating weight of 1.0 g/m. A suction layer was formed.

Next, 1 part by weight of the charge-generating material of structural formula (I), 1 part by weight of butyral resin (Eslec BM-2, manufactured by Tsukiki Chemical Co., Ltd.), 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 dip coating and dried to form a charge generating layer. The film thickness is 0.3. Met.

Next, compound lfi of the above-mentioned hydrazone compound example (1)
1 part by weight of polysulfone (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.

This film thickness was 12.51L.

A corona discharge of 15 KV was applied to the photoreceptor thus prepared. The surface potential (initial potential V) at this time was measured. Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 5 seconds (dark decay vj-).

Sensitivity was evaluated by measuring the exposure amount (E 1/21ux, 5ea) required to attenuate the potential V after dark decay to 1/2.

These results were as follows.

V6: -570V, Vr: -560V.

E 1/2: 3, 7 lux, sec Examples 2 to 5 Hydrazone compound examples (2) to (5) were used in place of hydrazone compound example (1) used in Example 1, respectively. A photoreceptor was prepared in exactly the same manner as in Example 1, and the characteristics of this photoreceptor were measured.

These results are shown below.

'IJJJ Audit 11Vo -V V,r -V E
1/2 Jug 5ec2 (2) 5
80 570 3.83 (3) 58
0 585 4.04 (4) 585
575 4.85 (5) 580 5
70 4.2 Comparative Examples 1 to 6 Comparative Examples 1 to 6 were carried out in exactly the same manner except that the following comparative charge transport substances (1) to (8) were used in place of the hydrazone compound used in Example 1. A photoreceptor was created and its charging characteristics were measured.

C,H.

Charging characteristics 1 (1) 550 500 5.4
2 (2) 53G 495 5.
03 (3) 500 485 5.
74 (4) 5[105157,15(
5) 580 580 8.26 (
6) 570 5130 8.9 As is clear from the results of Examples and Comparative Examples.

It can be seen that the N-type photoreceptor of the present invention has extremely high sensitivity compared to the photoreceptors of Comparative Examples 1 to 6. Furthermore, the photoconductors of Examples 1 to 5 were used in a copying machine (manufactured by Canon Co., Ltd.,
Image generation was repeated 20,000 times using NP-1502).

As a result, good quality images were obtained even after repeating 20,000 times with each photoreceptor.1 The electrophotographic photoreceptor of the present invention
It can be seen that the durability is also extremely excellent.

[Effects of the Invention] As is clear from the above, the present invention uses a charge-generating material and a specific polycyclic quinone-based pigment as the charge-generating material, and a specific hydrazone-based compound in the charge transport layer. This made it possible to provide a laminated electrophotographic photoreceptor with extremely high sensitivity compared to conventional products.

Claims (2)

[Claims] (1) In a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge generation layer consists of a layer containing a polycyclic quinone pigment of structural formula (I), and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) Hydrazone compounds whose charge transport layer is represented by the general formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) (In the formula, R_1 and R_2 are substituted or unsubstituted alkyl group, substituted or unsubstituted aryl group or nitrogen,
Indicates the atomic group necessary to complete a 5-membered ring or 6-membered ring together with atoms, and R_3 and R_4 are substituted or unsubstituted alkyl groups, substituted or unsubstituted aryl groups, or together with nitrogen atoms, 5-membered or 6-membered rings. R_5 and R_6 are hydrogen atoms, halogen atoms, nitro groups, substituted or unsubstituted alkyl groups, alkoxy groups, substituted or unsubstituted aryloxy groups, substituted or unsubstituted acyl groups. group or a substituted or unsubstituted amino group, R represents a divalent organic residue)
An electrophotographic photoreceptor comprising a layer containing. (2) The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer contains a hydrazone compound represented by formula (II).