JP2665781B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member, and more particularly, to an electrophotographic photosensitive member containing a disazo pigment having a specific molecular structure in a photosensitive layer.

[Prior Art] Conventionally, as an electrophotographic photoreceptor, those having a photosensitive layer mainly composed of an inorganic photoconductive compound such as selenium, cadmium sulfide, and zinc oxide have been widely used.

However, these inorganic electrophotographic photoreceptors have thermal stability,
It is not always satisfactory in moisture resistance and durability.

For example, when selenium is crystallized, its properties as an electrophotographic photoreceptor are deteriorated, so that it is difficult to manufacture, and selenium is crystallized due to heat or fingerprints. Cadmium sulfide has problems in moisture resistance and durability, and zinc oxide has problems in smoothness, hardness and friction resistance.

Furthermore, the photosensitive wavelength region of many inorganic electrophotographic photosensitive members is limited, and various methods have been proposed to extend the photosensitive wavelength to a long wavelength region, but there are many restrictions.

On the other hand, an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductive compound as a main component has many advantages such as being easy to produce and generally having better thermal stability than selenium or the like.

In particular, a conventional electrophotographic photoreceptor is composed of a layered electrophotographic photosensitive member including a layer containing a substance that generates charges when irradiated with light (charge generation layer) and a layer containing a substance that transfers charges (charge transport layer). Some of them have been practically used because they generally have higher sensitivity than photoreceptors and have stable charging properties.

For example, Japanese Patent Publication No. 50-10496, U.S. Pat.
In the specification, poly-N-vinylcarbazole and 2,4,7-
There are a photoreceptor having a photosensitive layer containing trinitrofluorenone-9-one and a photoreceptor sensitized from poly-N-vinylcarbazole with a pyrylium salt dye (JP-B-48-25658).

Although these organic electrophotographic photoreceptors have improved the disadvantages of the inorganic electrophotographic photoreceptor to some extent, they are not always satisfactory in sensitivity and durability.

Various studies have been made on using organic dyes and pigments as charge generating substances.

For example, JP-A-59-33445, JP-A-56-46237, and JP-A-60-111249 are already known as photoreceptors using a disazo pigment or a trisazo pigment as a charge generating substance.

Further, as an electrophotographic photosensitive member using a phenazine pigment as a charge generating substance, for example, Japanese Patent Application Laid-Open No. Sho 62-296147 has been proposed.

However, electrophotographic photoreceptors using these disazo pigments or trisazo pigments as charge generating substances are not always satisfactory in sensitivity, residual potential or stability characteristics upon repeated use, and the selection range of the charge transporting substance. However, it does not sufficiently satisfy a wide range of requirements of the electrophotographic process.

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel photoconductive material,
To provide an electrophotographic photoreceptor containing a specific disazo pigment which is stable to heat and light, and has excellent charge generating ability, has a high sensitivity and a small residual potential, and is stable when repeatedly used. An object of the present invention is to provide an electrophotographic photosensitive member having potential characteristics.

[Means for Solving the Problems and Functions] An electrophotographic photoreceptor having a photosensitive layer on a conductive support comprises an electrophotographic photoreceptor characterized in that the photosensitive layer contains a disazo pigment represented by the following general formula (1).

General formula In the formula, X represents a pyridine ring which may have a substituent,
A represents a coupler residue having a phenolic hydroxyl group.

Specifically, examples of the substituent which the pyridine ring of X may have include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and an alkyl group such as methyl and ethyl.

Examples of the coupler residue having a phenolic hydroxyl group represented by A include residues represented by the following general formulas (2) to (4).

In the formula, Z represents a divalent group of an aromatic hydrocarbon or a divalent group of a heterocyclic ring containing a nitrogen atom in the ring, and the divalent group of the aromatic hydrocarbon is a monocyclic group such as o-phenylene. A divalent group of an aromatic hydrocarbon, o-naphthylene, perinaphthylene,
Examples include condensed aromatic hydrocarbon divalent groups such as 1,2-anthrylene and 9,10-phenanthrylene.Examples of the heterocyclic divalent group containing a nitrogen atom in the ring include 3,4-pyrazole And divalent groups such as a diyl group, a 2,3-pyridinediyl group, a 4,5-pyrimidinediyl group, a 6,7-indazolediyl group, and a 6,7-quinolinediyl group.

In the formula, Y is condensed with a benzene ring to form a naphthalene ring, an anthracene ring, a carbazole ring, a benzocarbazole ring,
A residue necessary for forming a polycyclic aromatic ring or a heterocyclic ring such as a dibenzofuran ring, a dibenzonaphthofuran ring, a diphenylene sulfide ring, and a fused ring of Y is a naphthalene ring, an anthracene ring, a carbazole ring, a benzocarbazole ring Is more preferable. R ₁ represents an aryl group or a heterocyclic group which may have a substituent, and specific examples include phenyl, naphthyl, anthryl, pyrenyl, pyridyl, thienyl, furyl, and carbazolyl groups. Further substituents of the aryl group and the heterocyclic group include a fluorine atom, a chlorine atom, an iodine atom, a halogen atom such as a bromine atom, methyl, ethyl, propyl, isopropyl,
Examples thereof include an alkyl group such as butyl, an alkoxy group such as methoxy, ethoxy, propoxy, and phenoxy; a nitro group, a cyano group; a substituted amino group such as dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino.

In the formula, R ₂ and R ₃ represent a hydrogen atom, an alkyl group which may have a substituent, an aralkyl group, an aryl group or a heterocyclic group, and specifically, as the alkyl group, methyl, ethyl, propyl, butyl , Aralkyl groups include benzyl, phenethyl, naphthylmethyl, aryl groups include phenyl, diphenyl, naphthyl, anthryl, and heterocyclic groups include carbazole, thienyl, pyridyl, and furyl. , Aryl group, as a substituent of the heterocyclic group, a fluorine atom, a chlorine atom, an iodine atom, a halogen atom such as a bromine atom, methyl, ethyl, propyl, isopropyl, an alkyl group such as butyl, methoxy, ethoxy, propoxy,
Alkoxy groups such as phenoxy, nitro groups, cyano groups,
And substituted amino groups such as dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, and pyrrolidino.

 Y has the same meaning as Y in the general formula (3).

Hereinafter, typical examples of the disazo pigment represented by the general formula (1) will be listed.

However, these disazo pigments do not limit the claims of the present invention.

The description shall show only those X and A that vary in the basic form.

As a general production method of the disazo pigment represented by the general formula (1), The diamine shown by using sodium nitrite or nitrosylsulfuric acid, etc., was converted into a tetrazonium salt by a conventional method and subjected to aqueous coupling with the corresponding coupler, or the obtained tetrazonium salt was taken out as a stable salt such as a borofluoride salt Thereafter, it can be easily synthesized by coupling with a corresponding coupler in a solvent such as N, N-dimethylformamide.

The coating containing the disazo pigment represented by the general formula (1) has photoconductivity and can be used for a photosensitive layer of an electrophotographic photoreceptor.

That is, in the present invention, an electrophotographic photoreceptor can be formed by dispersing and containing the disazo pigment represented by the general formula (1) in a suitable binder on a conductive support to form a film.

In a preferred embodiment of the present invention, the above-described photoconductive coating can be applied as a charge generation layer in an electrophotographic photosensitive member in which the photosensitive layer of the electrophotographic photosensitive member is functionally separated into a charge generation layer and a charge transport layer.

The charge generation layer contains as much of the aforementioned photoconductive disazo pigment as possible to obtain sufficient absorbance,
In addition, in order to shorten the range of the generated charge carrier, it is desirable to form a thin film layer having a thickness of, for example, 5 μm or less, preferably 0.01 to 1 μm.

As described above, the charge generation layer can be formed, for example, by dispersing a disazo pigment represented by the general formula (1) in a suitable binder and applying the resultant to a conductive support.

The binder that can be used when forming the charge generation layer by coating can be selected from a wide range of insulating resins, and can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. Preferably, polyvinyl butyral, polyvinyl benzal, polyarylate (such as a condensation polymer of bisphenol A and phthalic acid), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinyl pyridine, cellulose resin, Examples include insulating resins such as urethane resins, casein, polyvinyl alcohol, and polyvinylpyrrolidone.

The amount of the resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less.

The solvent for dissolving these resins differs depending on the type of the resin, and is preferably selected from those which do not dissolve the charge transport layer or the undercoat layer described below.

Specific organic solvents include methanol, ethanol,
Alcohols such as isopropanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as dichlorohexane, N, N-dimethylformamide,
N, N- amides such as dimethylacetamide, sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, ethers such as ethylene glycol monomethyl ether, methyl acetate, esters such as ethyl acetate, chloroform, methylene chloride, dichloroethylene, Aliphatic halogenated hydrocarbons such as carbon tetrachloride and trichloroethylene, and aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene can be used.

Coating can be performed using a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a Meyer bar coating method, a blade coating method, a roller coating method, and a curtain coating method.

Drying is preferably performed by touch drying at room temperature and then heating and drying. The heating and drying can be performed at a temperature of 30 to 200 ° C. for 5 minutes to 2 hours in a still or blown state.

As the charge transport substance, pyrene, N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N-
Phenylhydrazino-3-methylidene-9-ethylcarbazole, N, N-diphenylhydrazino-3-methylidene-9-ethylcalibazole, N, N-diphenylhydrazino-3-methylidene-10-ethylphenothiazine, N,
N-diphenylhydrazino-3-methylidene-10-ethylphenoxazine, p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, p-diethylaminobenzaldehyde-N-α-naphthyl-N-diphenylhydrazone, p-pyrrolidinobenzaldehyde- N, N-
Diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N, N-diphenylhydrazone, p
Hydrazone compounds such as -diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone, 2,
5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1-phenyl-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [quinolyl (2) ] -3- (p-Diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (p-
Diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [6-methoxy-pyridyl (2)]-3- (p-diethylaminostyryl) -5-
(P-diethylaminophenyl) pyrazolin, 1- [pyridyl (3)]-3- (p-diethylaminostyryl)
-5- (p-diethylaminophenyl) pyrazoline, 1
-[Lepidyl (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (p-diethylaminostyryl) -4-methyl-5 -(P-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3-
(Α-methyl-p-diethylaminostyryl) -5-
(P-diethylaminophenyl) pyrazolin, 1-phenyl-3- (p-diethylaminostyryl) -4-methyl-5- (p-diethylaminophenyl) pyrazolin,
Pyrazoline compounds such as 1-phenyl-3- (α-benzyl-p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazolin and spiropyrazolin, α-phenyl-N, N-diphenylaminostilbene, N-ethyl- 3- (α-phenylstyryl) carbazole, 9-p-dibenzylaminobenzylidene-9H-
Fluorenone, 5-p-ditolylaminobenzylidene-
Styryl compounds such as 5H-dibenzo [a, d] cycloheptene, 2- (p-diethylaminostyryl) -6-diethylaminobenzoxazole, 2- (p-diethylaminophenyl) -4- (p-dimethylaminophenyl) -5 Oxazole compounds such as-(2-chlorophenyl) oxazole, thiazole compounds such as 2- (p-diethylaminostyryl) -6-diethylaminobenzothiazole, and triaryl compounds such as bis (4-diethylamino-2-methylphenyl) phenylmethane Methane compound, 1,1-bis (4-N, N-diethylamino-2
-Methylphenyl) heptane, polyarylalkane-based compounds such as 1,1,2,2-tetrakis (4-N, N-dimethylamino-2-methylphenyl) ethane, triphenylamine, poly-N-vinylcarbazole, Polyvinyl pyrene, polyvinyl anthracene, polyvinyl acridine, poly-9-vinyl anthracene, a pyrene-formaldehyde resin, an ethyl carbazole formaldehyde resin, and the like.

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can be used.

These charge transport materials can be used alone or in combination of two or more.

When the charge transport material does not have a film-forming property, a film can be formed by selecting an appropriate binder. Resins that can be used as binders include, for example, insulating resins such as acrylic resins, polyarylates, polyesters, polycarbonates, polystyrenes, acrylonitrile-styrene copolymers, acrylonitrile-butadiene copolymers, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, and chlorinated rubber. Resin or poly-N-vinylcarbazole,
Organic photoconductive polymers such as polyvinyl anthracene and polyvinyl pyrene are exemplified.

Since the charge transport layer has a limit for transporting charge carriers, it cannot be made thicker than necessary. Generally, it is 5 to 40 μm, but a preferable range is 15 to 30 μm.
It is.

When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

Such a photosensitive layer having a laminated structure of a charge generation layer and a charge transport layer is provided as a conductive support on a support having, for example, a conductive layer.

As the conductive support, the support itself has conductivity, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium,
Nickel, indium, gold, platinum, and the like can be used. In addition, plastics having a layer in which aluminum, an aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, or the like is formed by a vacuum evaporation method can be used. For example, a support in which conductive particles (for example, carbon black, silver particles, etc.) are coated on a plastic together with a suitable binder, conductive particles, such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, and fluorinated ethylene. And a support having a conductive polymer impregnated in plastic or paper.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive layer and the photosensitive layer. The undercoat layer is casein,
Polyvinyl alcohol, nitrocellulose, ethylene-
It can be formed of acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon and the like), polyurethane, gelatin, aluminum oxide and the like.

The thickness of the undercoat layer is 5 μm or less, preferably 0.1 to 3 μm.
m is appropriate.

As another specific example of the electrophotographic photoreceptor of the present invention, an electrophotographic photoreceptor in which the disazo pigment represented by the general formula (1) is contained in the same layer together with the charge transporting material can be mentioned.

At this time, in addition to the charge transport material, a charge transfer complex compound composed of poly-N-vinylcalibazole and trinitrofluorenone can be used.

The electrophotographic photoreceptor of this example is manufactured by dispersing a disazo pigment represented by the above general formula (1) and a charge transfer complex compound in a polyester solution dissolved in tetrahydrofuran and then forming a film.

The pigment used in any of the electrophotographic photosensitive members is at least one selected from disazo pigments represented by the general formula (1).
Contains different types of pigments.

If necessary, two or more disazo pigments represented by the above general formula (1) may be used in combination for the purpose of increasing the sensitivity of the photoreceptor by using a combination of pigments having different light absorptions and obtaining a panchromatic photoreceptor. Alternatively, it can be used in combination with a charge generating substance selected from known dyes and pigments.

The electrophotographic photoreceptor of the present invention can be applied to various optical recording devices such as a laser beam printer and an LED printer in addition to being used for an electrophotographic copying machine.

Examples Examples 1 to 6 An undercoat layer made of a 0.1 μm vinyl chloride-maleic anhydride-vinyl acetate copolymer was provided on an aluminum plate.

Next, 5 g of the above exemplified pigment (1) was added to 95 ml of cyclohexanone.
Was dissolved in a solution of 2 g of butyral resin (butyralization degree: 63 mol%, number average molecular weight: 20,000), and dispersed by a sand mill for 20 hours. This dispersion was applied on a previously formed undercoat layer with a Meyer bar so that the dried roundness was 0.5 μm, and dried to form a charge generation layer.

Next, p-diethylaminobenzaldehyde-N-α
5 g of naphthyl-N-phenylhydrazone and 5 g of polymethyl methacrylate (number average molecular weight 100,000)
The solution was dissolved in 70 ml, and this solution was applied on a charge generation layer with a Meyer bar so that the film thickness after drying was 20 μm, and dried to form a charge transport layer. Thus, an electrophotographic photosensitive member of Example 1 was prepared.

Electrophotographic photosensitive members corresponding to Examples 2 to 6 were prepared in the same manner as in Example 1 except that the following exemplary pigment was used instead of the exemplary pigment (1) used in Example 1.

The electrophotographic photoreceptor thus prepared was corona-charged at −5.5 KV in a static manner using an electrostatic copying paper tester (Model SP-428, manufactured by Kawaguchi Electric Co., Ltd.) and held for 1 second in a dark place. Thereafter, the substrate was exposed to light with an illuminance of 2 lux, and charging characteristics were examined.

As the charging characteristics, the surface potential (Vo) and the exposure amount (E1 / 2) required to attenuate the potential after dark decay for 1 second to half were measured. The results are shown. Examples Illustrative pigments Vo (−V) E1 / 2 (lux, sec) 1 (1) 740 1.9 2 (2) 725 4.2 3 (3) 740 3.0 4 (4) 735 2.85 (5) 745 4.36 (6) 730 4.0 Comparative Example In place of the exemplary pigment (1) used in Example 1,
A photoreceptor was prepared and evaluated in the same manner as in Example 1 except that the azo pigment represented by the following structural formula described in JP-A-29614 was used. The results are shown.

Vo: -775V E1 / 2: 8,2 lux, sec From these results, it can be seen that all of the electrophotographic photoreceptors of the present invention have sufficient charging ability and excellent sensitivity.

[Effects of the Invention] It is presumed that the electrophotographic photoreceptor of the present invention improves one or both of carrier generation efficiency and carrier transport efficiency in the photosensitive layer by using a specific disazo pigment in the photosensitive layer. As a result, the electrophotographic photoreceptor has high sensitivity and durability, and in particular, has excellent potential stability when used in durability.

Claims (1)

(57) [Claims] An electrophotographic photosensitive member having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a disazo pigment represented by the following general formula (1). General formula In the formula, X represents a pyridine ring which may have a substituent,
Represents a coupler residue having a phenolic hydroxyl group represented by the following general formulas (2) to (4). General formula In the formula, Z represents a divalent group of an aromatic hydrocarbon or a divalent group of a heterocyclic ring containing a nitrogen atom in the ring. General formula In the formula, Y represents a residue necessary for forming a polycyclic aromatic ring or a heterocyclic ring by condensing with a benzene ring, and R ₁ represents an aryl group or a heterocyclic group which may have a substituent. General formula In the formula, Y represents a residue necessary for forming a polycyclic aromatic ring or a heterocyclic ring by condensing with a benzene ring, R ₂ and R ₃ represent a hydrogen atom, an alkyl group which may have a substituent, It represents an aralkyl group, an aryl group or a heterocyclic group.