JPH07120056B2 - Electrophotographic photoreceptor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel electrophotographic photoreceptor, and more specifically, an electrophotographic photoreceptor containing a disazo pigment having a specific molecular structure in a photosensitive layer. Regarding

[Conventional technology]

Electrophotography is a photoconductive method comprising a support coated with an insulating material in the dark, the electric resistance of which changes according to the amount of irradiation received during image exposure as shown in U.S. Pat. Use material. The basic characteristics required for an electrophotographic photosensitive member using this photoconductive material are (1) being able to be charged to an appropriate potential in a dark place (2) Little dissipation of charges in a dark place (3) It is possible to rapidly dissipate the electric charge by light irradiation.

Conventionally, as an electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer containing an inorganic photoconductive compound such as selenium, zinc oxide, or cadmium sulfide as a main component has been widely used. However, although these satisfy the above conditions (1) to (3), they are not necessarily satisfactory in terms of thermal stability, moisture resistance, durability and the like. For example, when selenium is crystallized, the characteristics as a photoreceptor are deteriorated, which is difficult to manufacture, and crystallization is caused by heat, fingerprints, etc., and the performance as a photoreceptor is deteriorated. Also, cadmium sulfide has problems in moisture resistance and durability, and zinc oxide has problems in smoothness, hardness, and abrasion resistance. Further, most of the inorganic photoconductors have a limited photosensitive wavelength region. For example, in selenium, the photosensitive wavelength region is in the blue region and there is almost no sensitivity in the red region. Therefore, various methods have been proposed to extend the photosensitivity to the long wavelength region, but there are many restrictions on the selection of the photosensitizing wavelength region. When using zinc oxide or cadmium sulfide as a photoreceptor,
The photosensitive wavelength region itself is narrow, and it is necessary to add various sensitizers.

In order to overcome the drawbacks of these inorganic photoconductors, electrophotographic photoconductors containing various organic photoconductive compounds as main components have been actively developed in recent years. For example, Japanese Examined Japanese Patent Publication 50-10496
U.S. Pat. No. 3,484,237 discloses poly-N-vinylcarbazole and 2,4,7-trinitrofluorenone-9.
There are a photoreceptor having a photosensitive layer containing -one, a photoreceptor obtained by sensitizing poly-N-vinylcarbazole with a pyrylium salt dye (Japanese Patent Publication No. Sho 48-25658), and the like. These organic electrophotographic photoconductors have some drawbacks of the above-mentioned inorganic electrophotographic photoconductors, but generally have low photosensitivity and are not suitable for repeated use. In order to overcome these drawbacks, various photoconductors have been proposed as organic electrophotographic photoconductors in recent years. Among them, a layer containing a substance (hereinafter, referred to as a charge generation substance) that generates a charge carrier when irradiated with light (hereinafter, referred to as a charge generation substance). , A charge generation layer) and a layer (hereinafter, referred to as a charge transport layer) mainly containing a substance (hereinafter, referred to as a charge transport substance) that receives and transports the charge carriers generated by the charge generation layer. The photosensitive member of 1 is generally higher in sensitivity than conventional organic electrophotographic photosensitive members, and some of them have been put to practical use because they can withstand repeated use.

For example, U.S. Pat. No. 3,738,851 discloses a photoreceptor having a charge generation layer and a charge transfer layer containing triallylpyrazolin, and U.S. Pat. No. 3,871,882 discloses a charge generation layer composed of a derivative of a perylene pigment and 3-bromopyrene. Examples thereof include a photoreceptor having a charge transport layer made of a condensation product of formaldehyde.

Further, JP-A-59-33445, JP-A-56-46237, JP-A-60-111249 and the like are already known as photoreceptors using a bisazo pigment or trisazo pigment as a charge generating substance. However, these bisazo pigments or trisazo pigments are not always satisfactory in the characteristics of sensitivity, residual potential or stability upon repeated use.
In addition, the selection range of the charge transport material is limited, so that it does not sufficiently satisfy the wide requirements of the electrophotographic process.

[Problems to be solved by the invention]

The first object of the present invention is to provide a novel photoconductive material.

A second object of the present invention is to provide an electrophotographic photosensitive member having stable potential characteristics upon repeated use of practical high sensitivity characteristics in the visible region.

[Means for solving problems]

The present invention is an electrophotographic photoreceptor 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 B in the general formula (1) is -O-, -S-, Or Indicates.

A and A ′ in the general formula (1) represent coupler residues having a phenolic OH group, and may be the same or different. More preferred specific examples of the coupler residue represented by A and A'are represented by formulas (2) to (6).

In the formula, X is condensed with a benzene ring to form a polycyclic aromatic ring such as a naphthalene ring, anthracene ring, carbazole ring, benzcarbazole ring, dibenzofuran ring, dibenzonaphthofuran ring, diphenylene sulphite ring or hetero ring. The required residues are shown below.

The ring to which X is bonded is more preferably a naphthalene ring, anthracene ring, carbazole ring or benzcarbazole ring.

In the formula, R ₁ and R ₂ represent a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, a heterocyclic group or a nitrogen atom bonded to R ₁ and R _{2 and} a cyclic amino group. .

Specific examples of the alkyl group include methyl, ethyl, propyl and butyl, specific examples of the aralkyl group include benzyl, phenethyl and naphthylmethyl, and specific examples of the aryl group include phenyl, diphenyl, naphthyl and anthryl. Specific examples of the heterocyclic group include carbazole,
Examples thereof include dibenzofuran, benzimidazolone, benzthiazole, thiazole and pyridine.

In the formula, R ₃ represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, or an aralkyl group. Specific examples of R ₃ are shown by the same examples as R ₁ and R ₂ .

The alkyl group, aryl group, aralkyl group, alkoxy group and heterocyclic group represented by the substituents R _{1 to} R ₃ are other substituents, for example, halogen groups such as fluorine, chlorine, iodine and bromine, methyl, ethyl and propyl. Substituted with alkyl groups such as isopropyl, butyl, alkoxy groups such as methoxy, ethoxy, propoxy, phenoxy, etc., substituted amino groups such as nitro, cyano, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, pyrrolidino. May be.

In the formula, Y represents an aromatic hydrocarbon divalent group or a heterocyclic divalent group containing a nitrogen atom in the ring.

As the divalent group of the aromatic hydrocarbon, a divalent group of a monocyclic aromatic hydrocarbon such as o-phenylene, a condensed polycondensation group such as o-naphthylene, perinaphthylene, 1,2-anthrylene, and 9,10-phenanthrylene. A divalent group of a cyclic aromatic hydrocarbon may be mentioned. Further, as the divalent group of the hetero ring containing a nitrogen atom in the ring, 3,4-pyrazolediyl group, 2,3-pyridinediyl group, 4,5-pyrimidinediyl group, 6,7-indazolediyl group, A divalent group such as a 6,7-quinolinediyl group may be mentioned.

In the formula, R ₄ represents an aryl group or a heterocyclic group which may have a substituent, and specifically represents a phenyl, naphthyl, anthryl, pyrenyl, pyridyl, thienyl, furyl or carbazolyl group.

The aryl group represented by R ₄ and the substituent of the heterocyclic group are halogen groups such as fluorine, chlorine, iodine and bromine, alkyl groups such as methyl, ethyl, propyl, isopropyl and butyl,
Examples thereof include alkoxy groups such as methoxy, ethoxy, propoxy and phenoxy, and substituted amino groups such as nitro group, cyano group, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino and pyrrolidino.

In the formula, R ₅ and R ₆ represent a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, or a heterocyclic group, and specifically include methyl, ethyl, propyl, butyl, benzyl, It shows phenethyl, naphthylmethyl, phenyl, naphthyl, anthryl, diphenyl, carbazole, dibenzofuran, benzimidazolone, benzthiazole, thiazole and pyridine.

In the formula, alkyl, aryl, aralkyl, and heterocyclic groups represented by R ₅ and R ₆ are halogen groups such as fluorine, chlorine, iodine, and bromine as substituents of methyl, ethyl, propyl, isopropyl, butyl, etc. Alkyl group of methoxy,
Alkoxy groups such as ethoxy, propoxy and phenoxy,
Substituted amino groups such as nitro group, cyano group, dimethylamino, dibenzylamino, diphenylamino, morpholino, piperidino, pyrrolidino and the like can be mentioned.

The following are already known as disazo pigments having a structure similar to the central skeleton of the disazo pigment of the present invention.

Cp represents a coupler residue, and R represents a substituent.

However, these disazo pigments are not always satisfactory in terms of residual potential or stability characteristics upon repeated use. According to the inventors, one of these causes
It is believed that this is due to the strength of the electron-donating property (donor) of the central skeleton, and the structure of the central skeleton of the pigment reduces the ionization potential of the pigment molecule itself, affecting sensitivity and other properties. Be done. Further, these pigments have high sensitivity only when they are combined with a charge transporting substance having a low oxidation potential, and there is a problem in terms of durability since a charge transporting substance having a high oxidation potential cannot be used.

The electrophotographic photosensitive member using the disazo pigment according to the present invention has a cyano group having a strong electron-attracting property as an N-substituent on the central skeleton, so that it has a higher center than an unsubstituted or electron-donating substituent. The skeleton can be made more acceptor. Therefore, when the disazo pigment according to the present invention is used as a charge generation layer, it is possible to use a charge transport material having a relatively high oxidation potential (Eox (V) = 0.70V or more). And higher sensitivity can be realized.

Since a charge transport material with a high oxidation potential can be used, it has excellent chemical stability such as ozone oxidation associated with corona discharge on the surface of the electrophotographic photosensitive member, and in particular can maintain potential stability during repetition. .

The oxidation potential of the charge-transporting substance indicates the peak value (Eox) of the first oxidation wave. In practice, methanol, ethanol, acetonitrile, etc. are used as a solvent, and tetra-n-butylammonium perchlorate, a perchlorate is used as a supporting electrolyte. It can be measured by cyclic voltammetry using salts such as lithium chlorate and tetraethylammonium p-tolueneate and a saturated calomel electrode as an electrode. However, the measurement is not limited to this method, and it can be obtained by potentiometry or polarography.

In the present invention, the oxidation potential was measured by cyclic voltammetry using acetonitrile as a solvent, tetra-n-butylammonium perchlorate as a supporting electrolyte, and a saturated calomel electrode as an electrode.

The general method for producing the disazo pigment of the general formula (1) used in the present invention will be described. When A and A'are the same in the disazo pigment represented by the general formula (1), the diamine represented by the following general formula (7) is converted to a tetrazonium salt by a conventional method using sodium nitrite or nitrosyl sulfuric acid, and the coupler component is used. It can be obtained by performing an aqueous coupling with a certain A or A ', or by taking out the obtained tetrazonium salt as a stable salt such as a borohydride salt and then performing the coupling in an organic solvent such as dimethylformamide. When A and A ′ are different, in the coupling reaction, first coupling is performed with the first coupler component to form a monoazo body, and then coupling is performed with the second coupler component to obtain a disazo pigment or two coupler components. It can be obtained by mixing and performing a coupling reaction. Further, as another method, it can be obtained by the following method.

B in the formula has the same meaning as in formula (1).

That is, the acetylamino compound represented by the general formula (8) is diazotized to form a coupler having a phenolic hydroxyl group. After coupling, they are hydrolyzed with mineral acids such as hydrochloric acid or alkalis such as sodium hydroxide to give amino compounds. (Cp represents a coupler residue having a phenolic OH group.), Diazotized again and coupled with another coupler residue to obtain an asymmetric pigment.

Next, specific examples of the disazo pigment used in the present invention are given below. However, these disazo pigments do not limit the claims of the present invention.

Next, typical synthetic examples of the disazo pigment used in the present invention are shown.

Synthesis Example 1 (Synthesis of azo pigment No. 1 exemplified above) 100 ml of water and 24 ml (0.27 mol) of concentrated hydrochloric acid were placed in a 300 ml beaker, and N-3,7-diamino-10'- was added while cooling with an ice water bath.
9.8 g (0.041 mol) of cyanophenoxazine was added, and the liquid temperature was adjusted to 3 ° C while stirring.

Next, a solution prepared by dissolving 6.0 g (0.087 mol) of sodium nitrite in 10 ml of water was added dropwise over 10 minutes while controlling the liquid temperature at 5 ° C or lower, and after the addition was completed, the mixture was stirred at the same temperature for 30 minutes.
Activated carbon was added to the reaction solution, and after filtration, a solution prepared by dissolving 13.5 g (0.123 mol) of sodium borohydride in 20 ml of water was added dropwise, and the precipitated borohydride salt was collected by filtration, washed with water, and dried in vacuum. Yield 15.4g Yield 83.2%.

Next, add 200 ml of DMF to one beaker and add 2.81 g of 2-hydroxy-3-naphthoic acid-2'-chloroanilide.
(0.01 mol) was dissolved, the liquid temperature was cooled to 5 ° C., 4.65 g (0.01 mol) of the borohydride salt obtained above was dissolved, and 1.02 g (0.01 mol) of triethylamine was added dropwise over 10 minutes, Then, the mixture was stirred for 2 hours. The reaction solution was filtered, washed with 200 ml of N, N-dimethylformamide four times, replaced with acetone, and dried under vacuum to obtain the desired azo pigment No. 1. Yield 7.
66g Yield 89.5% (based on broth salt).

Elemental analysis Calculated value Measured value C 65.97% 65.89% H 3.30% 3.20% N 13.10% 13.08% The film containing the disazo pigment of the above-mentioned general formula (1) exhibits photoconductivity, and thus the photosensitive layer of the electrophotographic photoreceptor. Can be used for.

That is, in the present invention, the electrophotographic photoreceptor is formed by forming a film of the disazo pigment represented by the general formula (1) on the conductive support by a vacuum vapor deposition method or by dispersing and dispersing the disazo pigment in an appropriate binder to form a film. can do.

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

The charge generation layer contains as much of the above-described photoconductive compound as possible in order to obtain sufficient absorbance, and is a thin film layer, for example, 5 μm or less, in order to shorten the range of the generated charge carrier. Is preferably a thin film layer having a film thickness of 0.01 to 1 μm. This means that most of the amount of incident light is absorbed by the charge generation layer to generate many charge carriers, and the generated charge carriers are not deactivated by recombination or trapping, and the charge transport layer is not deactivated. Attributed to the need to inject.

As described above, the charge generation layer can be formed, for example, by dispersing the disazo pigment of the general formula (1) in a suitable binder and coating it on a support, or by forming a vapor deposition film by a vacuum vapor deposition device. Can be obtained by doing. 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 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 phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin, polyamide, polyvinyl pyridine, cellulosic resin, urethane Insulating resins such as resins, epoxy resins, casein, polyvinyl alcohol, and polyvinylpyrrolidone can be mentioned. The resin contained in the charge generation layer is suitably 80% by weight or less, preferably 40% by weight or less.

The solvent that dissolves these resins differs depending on the type of resin, and is preferably selected from those that do not dissolve the charge transport layer and the undercoat layer described below. Specific organic solvents include alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and dimethyl sulfoxide. Sulfoxides, ethers such as tetrahydrofuran, dioxane and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride and trichloroethylene Alternatively, aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene can be used.

The coating can be performed by 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, a curtain coating method and the like. Drying is preferably performed by drying by touching at room temperature and then drying by heating. The heat drying can be performed at a temperature of 30 ° C. to 200 ° C. for a time in the range of 5 minutes to 2 hours while still or under blowing air.

The charge transport layer is electrically connected to the above-mentioned charge generation layer, and has a function of receiving the charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. ing. At this time, the charge transport layer may be located on the side farther from the charge generation layer than the conductive support, or may be located between the conductive support and the charge generation layer.

The charge-transporting substances include electron-transporting substances and hole-transporting substances, and the electron-transporting substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9- Fluorenone, 2,
4,5,7-Tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone, 2,4,5,7
There are electron withdrawing substances such as tetranitroxanthone and 2,4,8-trinitrothioxanthone and polymers obtained by polymerizing these electron withdrawing substances.

As the hole transporting substance, pyrene, N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N
-Phenylhydrazino-3-methylidene-9-ethylcarbazole, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N, N-diphenylhydrazino-3-methylidene-10-ethylphene Nothiazin,
N, N-diphenylhydrazino-3-methylidene-10-ethylphenoxazine, p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, p-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone, p-pyrrolidinobenzaldehyde-N, N-
Diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N, N-diphenylhydrazone, P
-Hydrazones 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- [pyridyl (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [6 -Methoxy-pyridyl (2)]-3
-(P-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [lepidyl (2)]-3- (p-diethylaminostyryl) -5-
(P-Diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (α-methyl-p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1-phenyl-3- (α -Benzyl-p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, spiropyrazoline and other pyrazolines, α-phenyl-4-N, N-diphenylaminostilbene, N-ethyl-3 (α-phenylstyryl) ) Carbazole, 9-p-dibenzylaminobenzylidene-9H
-Styryl compounds such as fluorenone, 5-p-ditolylaminobenzylidene-5H-dibenzo [a, d] cycloheptene, 2- (p-diethylaminostyryl) -6-
Oxazole compounds such as diethylaminobenzoxazole, 2- (p-diethylaminophenyl) -4- (p-dimethylaminophenyl) -5- (2-chlorophenyl) oxazole, 2- (p-diethylaminostyryl) -6- Thiazole compounds such as diethylaminobenzothiazole, triarylmethane compounds such as bis (4-diethylamino-2-methylphenyl) -phenylmethane, 1,1-bis (4-N, N-diethylamino-2-methylphenyl) heptane, 1 , 1,2,2-Tetrakis (4-
Polyarylalkanes such as N, N-dimethylamino-2-methylphenyl) ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-
Examples include vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin, and the like.

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

Further, 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. The resin that can be used as the binder is, for example, an acrylic resin,
Polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer,
Insulating resins such as acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, and chlorinated rubber, or organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene You can

Since the charge transport layer has a limit for transporting the charge carrier, the film thickness cannot be increased more than necessary. Generally, it is 5 to 40 μm, but the preferable range is 15 to 30 μm.
Is. When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

The photosensitive layer having such a laminated structure of the charge generation layer and the charge transport layer is provided on the conductive support. As the conductive support, one having conductivity itself, for example, 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,
Plastics (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluoroethylene, etc.) having a layer formed by coating a film of tin oxide, indium oxide-tin oxide alloy or the like by a vacuum deposition method, conductive particles (for example, , Titanium oxide, carbon black, silver particles, etc.) coated on a plastic with an appropriate binder, plastics or papers impregnated with conductive particles or plastics having a conductive polymer can be used. .

An undercoat layer having a barrier function and an adhesive function can be provided between the conductive support and the photosensitive layer. The subbing layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. Can be formed.

The thickness of the undercoat layer is 0.05 to 5 μm, preferably 0.5 to 3 μm
m is suitable.

In another embodiment of the present invention, the aforementioned hydrazones, pyrazolines, styryl compounds, oxazoles, thiazoles, triarylmethanes, polyarylalkanes, triphenylamine, poly-N-vinylcarbazoles. As a sensitizer of an organic photoconductive substance or an inorganic photoconductive substance such as zinc oxide, cadmium sulfide or selenium, a photosensitive film containing the disazo pigment represented by the general formula (1) can be used. This photosensitive film is formed by coating these photoconductive substances and the above-mentioned disazo pigment of the general formula (1) together with a binder.

Another specific example of the present invention is an electrophotographic photosensitive member containing the disazo pigment represented by the general formula (1) in the same layer together with a charge transporting substance. In this case, a charge transfer complex compound composed of poly-N-vinylcarbazole and trinitrofluorenone can be used in addition to the above charge transport material. The electrophotographic photoreceptor of this example can be prepared by dispersing the disazo pigment of the general formula (1) and the charge transfer complex compound in a solution of polyester dissolved in tetrahydrofuran, and then forming a film.

The pigment used in any of the photoconductors contains at least one kind of pigment selected from the disazo pigments represented by the general formula (1), and the crystal form thereof may be amorphous or crystalline. Further, two kinds of disazo pigments represented by the general formula (1) are used for the purpose of increasing the sensitivity of the photoconductor by using a combination of pigments having different light absorptions as required, and obtaining a panchromatic photoconductor. It is also possible to use a combination of the above or a known charge generating substance selected from dyes and pigments.

The electrophotographic photoreceptor of the present invention can be widely used not only in electrophotographic copying machines but also in electrophotographic application fields such as laser printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

Examples 1 to 9 0.1 μm vinyl chloride-maleic anhydride-on an aluminum plate
An undercoat layer made of a vinyl acetate copolymer resin was provided.

Next, the above-mentioned disazo pigment No. 1,5g was added to a solution prepared by dissolving 2g of butyral resin (degree of butyralization 63 mol% number average molecular weight 20000) in 95 ml of cyclohexanone, and added with a sand mill to obtain 2
It was dispersed for 0 hours. This dispersion was applied onto the previously formed undercoat layer with a Meyer bar so that the film thickness after drying was 0.4 μm, and dried to form a charge generation layer. Next, as a charge transport material, structural formula (9) Benzylidene compound (5 g) and polymethylmethacrylate resin (number average molecular weight 100,000) (5 g) are dissolved in 70 ml of chlorobenzene, and this is applied on the charge generation layer with a Meyer bar to a thickness of 20 μm and dried. A charge transport layer was formed by using the same to prepare the photoconductor of Example 1.

The electrophotographic photosensitive member thus produced was corona-charged at −5.5 KV by a static method using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., and held for 1 second in a dark place. It was exposed at an illuminance of 2 lux and the charging characteristics were examined. As the charging characteristics, the surface potential (V ₀ ) and the exposure amount (E1 / 2) required to attenuate the potential when dark-decayed for 1 second to 1/2 were measured. The results are shown in Table 1. Similarly, for the disazo pigments Nos. 1, 17 and 21, charge transport substances (9), (10),
Using (11), photoconductors corresponding to Examples 2 to 9 were prepared and measured by the same method. The results are shown in Table 1 and the oxidation potential Eox (V) of the charge transport material is shown in Table 2.

Comparative Examples 1 to 12 The disazo pigments of the following structural formulas were used in place of the disazo pigments of Examples 1 to 9, and in addition to the charge transporting substances of Examples 1 to 9, structural formula (12) Using the benzylidene compound (1), a photoconductor was prepared and evaluated in exactly the same manner as in Examples 1-9. The results are shown in Table 3.

Comparative Examples 1 to 3 are Examples 1 to 3 and Comparative Examples 5 to 7 are Example 4
6 and Comparative Examples 9 to 11 correspond to Examples 7 to 9, respectively, and the disazo pigment of Comparative Example has high sensitivity when combined with a charge transport material having a low oxidation potential, but has a relatively high oxidation potential. It can be seen that the sensitivity is low when used in combination with a high voltage (Eox = 0.70V or higher). From the above, it can be seen that the disazo pigment according to the present invention has excellent sensitivity when combined with a charge transport material having a relatively high oxidation potential.

Examples 10-18 Instead of the disazo pigments of Examples 1-9, the disazo pigment N
A photoconductor was prepared from o.2,8,10,12,14,15,19,20,22 using the charge transport material (9) by the same method as in Example 1 and evaluated. The results are shown in Table 4.

Examples 19 to 21 The photoreceptors used in Examples 1, 4, and 7 were used to measure fluctuations in the light potential and the dark potential during repeated use. As a method-
This photocopier, which has a 5.6KV corona charger, exposure optics, developing device, transfer charger, static elimination exposure optics, and cleaner, has a photosensitive body attached to the cylinder of an electrophotographic copier. An image can be obtained on the transfer paper. Using this copier, set the initial light potential (V _L ) and dark potential (V _D ) near -100V and -600V, respectively, and after using 5000 times, the light potential ( _VL ) and dark potential. (V _D ) was measured. The results are shown in Table 5.

Example 22 On the charge generation layer prepared in Example 1, 5 g of 2,4,7-trinitro-9-fluorenone and poly-4,4'-dioxydiphenyl-2,2'-propane carbonate (molecular weight 300,0
A coating solution prepared by dissolving 5 g of 00) in 70 ml of tetrahydrofuran was applied so that the coating amount after drying would be 10 g / m ^2, and dried.

The electrophotographic photosensitive member thus prepared was subjected to charge measurement in the same manner as in Example 1. At this time, the charging polarity was set to +.
The results are shown below.

V ₀ : 600 V E 1/2: 5.8 lux · sec Example 23 A polyvinyl alcohol film having a thickness of 0.5 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. Next, the dispersion liquid of the disazo pigment used in Example 4 was applied on the polyvinyl alcohol layer previously formed by a Meyer bar so that the film thickness after drying was 0.5 μm, and dried to form a charge generation layer. .

Then the structural formula 5g of hydrazone compound and 5g of bisphenol Z-type polycarbonate resin (viscosity average molecular weight 30,000) dissolved in 32.5ml of monochlorobenzene are applied on the charge generation layer so that the film thickness after drying is 20μm and dried. A charge transport layer was formed. The charging property and durability property of the thus prepared photoconductor were measured by the same method as in Example 1. The results are shown in Table 6.

V ₀ : 600 volts E 1/2: 3.1ux ・ sec Example 24 Soluble nylon (6-66-
5% methanol solution of 610-12 quaternary nylon copolymer) was applied and dried to form an undercoat layer having a film thickness of 0.5 μm.

Next, 5 g of 2,4,7-trinitro-9-fluorenone and poly-
5 g of N-vinylcarbazole (number average molecular weight 300,000) was dissolved in 70 ml of tetrahydrofuran to form a charge transfer complex compound. This charge-transfer complex compound and the above-mentioned disazo pigment No. 11 g were mixed with polymethylmethacrylate-styrene copolymer resin (molecular weight 250,000) 5 g and tetrahydrofuran 70 ml.
It was added to the liquid dissolved in and dispersed. This dispersion was applied onto the undercoat layer and dried to prepare a 20 μm photosensitive member.

The charging characteristics of the thus prepared photoconductor were measured by the same method as in Example 1. The results are shown below. However, the charging polarity was.

V ₀ : 600V E 1/2: 6.2lux · sec Example 25 The charge transport layer and the charge generation layer of Example 1 were sequentially laminated on the nylon layer of the aluminum support having the nylon layer used in Example 24. A photoreceptor was formed in exactly the same manner as in Example 1 except that the layer structure was different, and the charging characteristics were measured in the same manner as in Example 1. However, the charging polarity was set. The results are shown below.

V ₀ : 605V E 1/2: 5.6 lux · sec (Effect of the invention) According to the present invention, by using a specific disazo pigment in the photosensitive layer, the carrier generation efficiency or the carrier transport efficiency in the photosensitive layer can be improved. It is presumed that either one or both of them will be improved, and as a result, an electrophotographic photoreceptor having high sensitivity and durability, and particularly excellent potential stability during durable use, is constructed.

Continuation of the front page (56) Reference JP 60-209740 (JP, A) JP 60-220350 (JP, A) JP 60-111251 (JP, A) JP 60-111252 (JP , A) JP-A-60-121451 (JP, A) JP-A-64-11264 (JP, A)

Claims (2)

[Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer contains a disazo pigment represented by the general formula (1). General formula [Wherein A and A'are phenolic coupler residues,
It may be the same or different. B is -O-, -S-, Indicates. ] 2. The electrophotographic photosensitive member according to claim 1, wherein A and A'in the general formula (1) are selected from the general formulas (2) to (6). (Wherein, X represents a residue necessary to form a benzene ring condensed with a polycyclic aromatic ring, or a hetero ring in. Formula, R ₁
And R ₂ represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, a heterocyclic group, or a nitrogen atom to which R ₁ and R ₂ are bonded, and a cyclic amino group. In the formula, R ₃ represents an optionally substituted alkyl group, aryl group, or aralkyl group. In the formula, Y represents an aromatic hydrocarbon divalent group or a heterocyclic divalent group containing a nitrogen atom in the ring. In the formula, R ₄ represents an aryl group or a heterocyclic group which may have a substituent. In the formula, R ₅ and R ₆ represent a hydrogen atom, an optionally substituted alkyl group, an aryl group, an aralkyl group, or a heterocyclic group. )