JP2534156B2 - 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 an azo pigment having a coupler component having a specific structure.

[Related Art] Conventionally, as an electrophotographic photoreceptor using an inorganic photoconductive substance, a photoreceptor using selenium, cadmium sulfide, zinc oxide or the like is widely known.

On the other hand, electrophotographic photoreceptors using organic photoconductive materials include photoconductive polymers represented by poly-N-vinylcarbazole and 2,5-bis (p-diethylaminophenyl) -1,3,4-oxa. Known are those using low-molecular weight organic photoconductive substances such as diazoles, and those in which such organic photoconductive substances are combined with various dyes and pigments.

An electrophotographic photoreceptor using an organic photoconductive substance has advantages in that it has good film-forming properties, can be produced by coating, and can provide an extremely high productivity and inexpensive photoreceptor. Further, there is an advantage that color sensitivity can be freely controlled by selecting a sensitizer such as a dye or a pigment to be used, and wide studies have been made so far. In particular, recently, with the development of a function-separated type photoreceptor in which an organic photoconductive pigment is used as a charge generation layer and a charge transport layer made of the above-mentioned photoconductive polymer or a low-molecular organic conductive material is laminated, Significant improvements have been made in sensitivity and durability, which have been regarded as the drawbacks of electrophotographic photoreceptors.

Many pigments for use in such organic electrophotographic photoreceptors have been proposed. In particular, azo pigments have been extensively studied because pigments having various properties can be easily synthesized by combining an amine component and a coupler component. However, there are problems in sensitivity and potential stability during repeated use, and only a few materials are in practical use.

As a coupler component used in such an azo pigment, naphthol AS described in JP-A-47-37543, etc.
Couplers, benzcarbazole couplers described in JP-A-58-1222967, naphthalimide couplers described in JP-A-54-79632, JP-A-57-1760
The perinone couplers described in JP-A-55 are already known.

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel electrophotographic photosensitive member, and to provide an electrophotographic photosensitive member having practical high sensitivity characteristics and stable potential characteristics in repeated use. Is.

[Means and Actions for Solving the Problems] The present invention provides an electrophotographic photoreceptor having a photoconductive layer containing an azo pigment represented by the following general formula (1) on a conductive support, in the general formula (1). At least one of Cp is a coupler residue represented by the general formula (2), and is composed of an electrophotographic photoreceptor.

ArN = N-Cp) _i (1) In the formula, Ar represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent which may be bonded via a bonding group, and Cp is It represents a coupler residue having a phenolic hydroxyl group, and i represents an integer of 1, 2, 3 or 4.

In the formula, R ₁ , R ₂ , R ₃ and R ₄ are the same or different and each have a hydrogen atom, an alkoxy group, a disubstituted amino group, a halogen atom, a nitro group, a cyano group, a trifluoromethyl group or a substituent. Optionally an alkyl group, an aryl group or an aralkyl group, Z ₁ and Z ₂ are the same or different and each represents an oxygen atom or a sulfur atom, and j and k are 1, 2, 3, 4
Alternatively, 5, l and m are integers of 1, 2, 3 or 4, and n is 0 or 1.

Specific examples of Ar in the general formula (1) include hydrocarbon aromatic rings such as benzene, naphthalene, fluorene, phenanthrene, anthracene, and pyrene, furan, thiophene, pyridine, indole, benzothiazole, carbazole, acridone, dibenzothiophene. Heterocyclic aromatic rings such as benzoxazole, benzotriazole, oxadiazole, and thiazole, and those in which the above aromatic rings are bonded directly or with an aromatic group or a non-aromatic group, for example, triphenylamine, diphenylamine, N
-Methyldiphenylamine, biphenyl, terphenyl, binaphthyl, fluorenone, phenanthrenequinone, anthraquinone, benzanthrone, diphenyloxadiazole, phenylbenzoxazole, diphenylmethane, diphenylsulfone, diphenylether, benzophenone, stilbene, distyrylbenzene, tetraphenyl -P-phenylenediamine, tetraphenylbenzidine and the like.

As the substituent which the aromatic hydrocarbon group or aromatic heterocyclic group which may be bonded via the above-mentioned bonding group may have, an alkyl group such as methyl, ethyl, propyl and butyl, methoxy, ethoxy and the like. Alkoxy group, dialkylamino group such as dimethylamino and diethylamino, halogen atom such as fluorine, chlorine and bromine, hydroxy group,
Examples thereof include a nitro group, a cyano group and a halomethyl group.

Specific examples of R ₁ , R ₂ , R ₃ and R _{4 in} the general formula (2) include an alkyl group such as methyl, ethyl, n-propyl and n-butyl, and an aryl group such as phenyl and naphthyl. , Groups such as pyrenyl and anthryl, groups such as benzyl, phenethyl and naphthylmethyl as aralkyl groups, and groups such as methoxy and ethoxy as alkoxy groups.
Examples include butoxy and phenoxy groups, examples of di-substituted amino groups include groups such as dimethylamino and diethylamino, and examples of halogen atoms include fluorine, chlorine, bromine and iodine.

In Cp in the general formula (1), the general formula (2)
Examples of the coupler residue other than the coupler residue shown in (1) which may coexist include coupler residues having the structures represented by the following general formulas (4) to (8).

X in the above general formulas (4), (5) and (6) represents a naphthalene ring, anthracene ring, carbazole ring, benzocarbazole ring or dibenzofuran ring which may be substituted with a benzene ring and may have a substituent. The residues required for formation are indicated.

R ₅ and R ₆ are a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, a heterocyclic group or R ₅ ,
R ₆ represents a cyclic amino group containing a nitrogen atom to which R ₆ is bonded, and R ₇ represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group, an aralkyl group, or a heterocyclic group.

R ₈ is an alkyl group which may have a substituent, an aryl group,
An aralkyl group and a heterocyclic group are shown.

Z ₃ represents an oxygen atom or a sulfur atom, and q is 0 or 1.
Indicates.

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

Specifically, o-phenylene, 0-naphthylene, perinaphthylene, 1,2-anthrylene, 3,4-pyrazolediyl, 2,3-pyridinediyl, 4,5-pyridinediyl, 6,7
Groups such as -indazolediyl, 6,7-quinolinediyl and the like.

Examples of the alkyl group in the above expression include groups such as methyl, ethyl, propyl, and butyl; examples of the aralkyl group include groups such as benzyl, phenethyl and naphthylmethyl; and examples of the heterocyclic group include pyridyl, thienyl, and furyl. Groups such as thiazolyl, carbazolyl, dibenzofuryl, benzimidazolyl, and benzothiazolyl.Examples of the cyclic amino group containing a nitrogen atom in the ring include pyrrole, pyrroline, pyrrolidine, pyrrolidone, indole,
And cyclic amino groups derived from indoline, isoindole, carbazole, benzoindole, imidazole, pyrazole, pyrazoline, oxazine, phenoxazine, benzocarbazole and the like.

As the substituent, an alkyl group such as methyl, ethyl and propyl, an alkoxy group such as methoxy and ethoxy, a substituted amino group such as diethylamino and dimethylamino, a halogen atom such as fluorine, chlorine, bromine and iodine,
Examples thereof include a phenylcarbamoyl group, a nitro group, a cyano group, and a halomethyl group such as trifluoromethyl.

Hereinafter, typical examples of the azo pigment used in the present invention will be listed.

The description method shows only the part that changes in the basic type.

Basic type 1 Ar-N = N-Cp Exemplified pigment (1-1) Exemplified pigment (1-2) Illustrative pigment (1-3) Basic type 2 Cp ₁ -N = N-Ar-N = N-Cp ₂ Exemplified pigment (2-1) Exemplified pigment (2-2) Illustrative pigment (2-3) Illustrative pigment (2-4) Illustrative pigment (2-5) Illustrative pigment (2-6) Illustrative pigment (2-7) Illustrative pigment (2-8) Exemplified pigment (2-9) Illustrative pigment (2-10) Illustrative pigment (2-11) Exemplified pigment (2-12) Illustrative pigment (2-13) Illustrative pigment (2-14) Illustrative pigment (2-15) Exemplified pigment (2-16) Exemplified pigment (2-17) Illustrative pigment (2-18) Illustrative pigment (2-19) Illustrative pigment (2-20) Exemplified pigment (2-21) Exemplified pigment (2-22) Illustrative pigment (2-23) Exemplified pigment (2-24) Exemplified pigment (2-25) Exemplified pigment (2-26) Basic type 3 Illustrative pigment (3-1) Illustrative pigment (3-2) Exemplified pigment (3-3) Illustrative pigment (3-4) Illustrative pigment (3-5) Basic type 4 Illustrative pigment (4-1) Exemplified pigment (4-2) In the above-mentioned specific azo pigment of the present invention, the corresponding amine is diazotized by a conventional method, and is coupled with the coupler represented by the general formula (2) in the presence of an alkali in an aqueous system.
After converting the diazonium salt to a borofluoride salt or a zinc chloride double salt, etc., it was treated with a coupler in the presence of a base such as sodium acetate, triethylamine, or triethanolamine in an organic solvent such as N, N-dimethylformamide or dimethylsulfoxide. It can be easily synthesized by coupling.

In the case of synthesizing a disazo pigment in which a coupler other than the coupler represented by the general formula (2) coexists in the molecule, the corresponding diamine is tetrazolated by a conventional method and isolated as the soluble salt described above, and then the general formula Coupler 1 shown in (2)
Synthesized by coupling 1 mol of a coupler of another type and then coupling 1 mol of a different type of coupler, or by protecting one amino group of the diamine with an acetyl group or the like and diazotizing this to form a coupler represented by the general formula (2). After ringing, the protecting group can be hydrolyzed with hydrochloric acid or the like, and this can be diazotized again and coupled with a coupler of a different type to synthesize.

A trisazo pigment or a tetrakisazo pigment in which a coupler other than the coupler represented by the general formula (2) coexists in the molecule is similarly synthesized.

The electrophotographic photosensitive member of the present invention has a photosensitive layer containing an azo pigment represented by the general formulas (1) and (2) on a conductive support. The form of the photosensitive layer may be any known form, but the photosensitive layer containing the azo pigments represented by the general formulas (1) and (2) is used as the charge generating layer and contains the charge transporting substance. A function-separated type photosensitive layer in which a charge transport layer is laminated is particularly preferable.

The charge generation layer can be formed by applying a coating solution prepared by dispersing the above-mentioned azo pigment together with a binder resin in a suitable solvent onto a conductive support by a known method and having a film thickness of, for example, 5 μm. Or less, preferably 0.1
It is desirable that the thin film layer has a thickness of ˜1 μm.

The binder resin used at this time is selected from a wide range of insulating resins or organic photoconductive polymers, but polyvinyl butyral, polyvinyl benzal, polyarylate, polycarbonate, polyester, phenoxy resin, cellulosic resin, acrylic resin, polyurethane. And the like, and the amount used is based on the content in the charge generation layer.
It is 80% by weight or less, preferably 40% by weight or less.

The solvent used is preferably selected from those which dissolve the resin and do not dissolve the charge transport layer and the undercoat layer described below.

Specifically, tetrahydrofuran, ethers such as 1,4-dioxane, cyclohexanone, ketones such as methyl ethyl ketone, amides such as N, N-dimethylformamide, methyl acetate, esters such as ethyl acetate, toluene, xylene, Examples thereof include aromatics such as chlorobenzene, alcohols such as methanol, ethanol and 2-propanol, and aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride and trichloroethylene.

The charge transport layer is laminated on or under the charge generation layer and has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting the charge carriers.

The charge-transporting layer is formed by dissolving a charge-transporting substance in a solvent together with a suitable binder resin, if necessary, and applying it. The film thickness thereof is generally 5 to 40 μm.
-30 μm is preferable.

The charge transporting substance includes an electron transporting substance and a hole transporting substance. Examples of the electron transporting substance include 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, chloranil, and tetralane. Examples thereof include electron-withdrawing substances such as cyanoquinodimethane, and those obtained by polymerizing these electron-withdrawing substances.

Examples of the hole-transporting substance include polycyclic aromatic compounds such as pyrene and anthracene, carbazole-based, indole-based, imidazole-based, oxazole-based, thiazole-based, oxadiazole-based, pyrazole-based, pyrazoline-based, thiadiazole-based and triazole-based compounds Heterocyclic compounds, such as
Hydrazone compounds such as p-diethylaminobenzaldehyde-N, N-diphenylhydrazone and N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, α-phenyl-4′-N, N-diphenylaminostilbene, 5 A styryl compound such as-[4- (di-p-tolylamino) benzylidene] -5H-dibenzo [a, d] cycloheptene, a benzidine compound, a triarylmethane compound, triphenylamine, or a group consisting of these compounds. Polymers having a main chain or a side chain (for example, poly-N-vinylcarbazole, polyvinylanthracene, etc.) can be mentioned.

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

Further, these charge transport substances can be used alone or in combination of two or more.

When the charge transport material does not have a film forming property, a suitable binder can be used. Specifically, insulating resin such as acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, polyacrylamide, polyamide, chlorinated rubber or organic photoconductive material such as poly-N-vinylcarbazole or polyvinylanthracene. And the like.

As the conductive support on which the photosensitive layer is formed, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, platinum and the like are used. In addition, plastics (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, etc.) coated with these metals or alloys by a vacuum deposition method, and conductive particles (for example, carbon black, silver particles, etc.) are suitable binders. A support coated with a resin on a plastic or metal substrate or a support obtained by impregnating plastic or paper with conductive particles can be used.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer.

The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxymethylated nylon, etc.), polyurethane, aluminum oxide and the like.

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

Another specific example of the present invention is an electrophotographic photoreceptor containing the above-mentioned azo pigment and a charge transport material in the same layer. At this time, a charge transfer complex composed of poly-N-vinylcarbazole and trinitrofluorenone can be used as the charge transport material.

The electrophotographic photoreceptor of this example can be formed by applying and drying a liquid in which the above-mentioned azo pigment and charge transfer complex are dispersed in a suitable resin solution.

The pigment used in any of the electrophotographic photoconductors may have an amorphous or crystalline crystalline form of the azo pigments represented by the general formulas (1) and (2). It is also possible to use two or more kinds of the azo pigments shown in (1) and (2) in combination, or to use them in combination with a known charge generating substance.

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 beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

[Examples] Examples 1 to 9 A solution prepared by dissolving 5 g of methoxymethylated nylon (weight average molecular weight of 32,000) and 10 g of alcohol-soluble copolymerized nylon (weight average molecular weight of 29,000) on 95 g of methanol on an aluminum substrate. Is applied with a Meyer bar, and the film thickness after drying is 1 μm
An undercoat layer could be formed.

Next, 5 g of Exemplified Pigment (2-1) was added to a solution of 95 g of cyclohexanone and 2 g of butyral resin (butyralization degree: 63 mol%), and the mixture was dispersed in a sand mill for 20 hours. The film thickness after drying this dispersion is 0.2μ on the undercoat layer formed earlier.
The charge generation layer was formed by coating with a Meyer bar so as to have a thickness of m and drying.

Next, 5 g of the hydrazone compound represented by the following structural formula Dissolve 5 g of polymethylmethacrylate (number average molecular weight 100,000) in 40 ml of toluene, apply this to the charge generation layer with a Meyer bar so that the film thickness after drying is 20 μm, and dry to form the charge transport layer. Then, the electrophotographic photosensitive member of Example 1 was formed.

Using other exemplified pigments instead of the exemplified pigment (2-1), electrophotographic photoreceptors corresponding to Examples 2 to 9 were prepared in exactly the same manner.

The electrophotographic photoconductor thus prepared was corona-charged at -5 KV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., held for 1 second in a dark place, and then exposed at an illuminance of 10 lux. The charging property was investigated.

As the charging characteristics, the surface potential (V _O ) and the exposure amount (E1 / 2) required to attenuate the potential after being left in the dark for 1 second to 1/2 were measured. The results are shown.

Comparative Examples 1 to 3 Electrophotographic photoconductors were carried out in the same manner as in each of the examples except that the azo pigments used in Examples 1, 3 and 6 were replaced with comparative pigments (A) to (C) represented by the following structural formulas. Was prepared and the charging characteristics were evaluated in the same manner.

Comparative pigment (A) Comparative pigment (B) Comparative pigment (C) From these results, it can be seen that the electrophotographic photosensitive member of the present invention has sufficient charging ability and excellent sensitivity.

Examples 10 to 12 Using the electrophotographic photoreceptors prepared in Examples 1, 2 and 6, the changes in the light potential and the dark potential during repeated use were measured.

As a method, -6.5KV corona charger, exposure optical system,
The electrophotographic photosensitive member was attached to a cylinder of an electrophotographic copying machine equipped with a developing device, a transfer charger, a static elimination exposure optical system and a cleaner. This copying machine is constructed so that an image can be obtained on a transfer sheet as the cylinder is driven.

Using this copier, the initial dark part potential V _D and bright part potential V _L were set to around −700 V and −200 V, respectively, and the amount of dark part potential variation (ΔV _D ) and the bright part potential when used 5,000 times. Variation of (Δ
_VL ) was measured. The results are shown. In addition, the negative symbol in the variation amount of the potential represents a decrease in the absolute value of the potential, and the positive symbol represents an increase in the absolute value of the potential.

Examples ΔV _D ΔV _L (V) (V) 10 −10 0 11 −5 +10 12 0 +10 Comparative Examples 4 to 6 The electrophotographic photosensitive members prepared in Comparative Examples 1 to 3 are repeatedly used in the same manner as in Example 10. The amount of potential fluctuation was measured. The results are shown.

Comparative Example ΔV _D ΔV _L (V) (V) 4 −85 +95 5 −60 +85 6 −55 +60 From the above results, it is understood that the electrophotographic photosensitive member of the present invention has little potential fluctuation during repeated use.

Example 13 An undercoating layer of polyvinyl alcohol having a thickness of 0.5 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. A dispersion of the disazo pigment used in Example 1 was applied and dried with a Meyer bar to give a film thickness of 0.2 μm.
m charge generating layer was formed.

Next, 5 g of a styryl compound having the following structural formula A solution prepared by dissolving 5 g of polyarylate (a polycondensate of bisphenol A and terephthalic acid-isophthalic acid) in 40 ml of tetrahydrofuran was applied on the charge generation layer and dried to give a film thickness of 20 μm.
m charge transport layer was formed. The charging characteristics and the durability characteristics of the produced electrophotographic photosensitive member were measured by the same methods as in Examples 1 and 10. The results are shown.

V _O : −705V E1 / 2: 2.3lux · sec ΔV _D : −5V ΔV _L : + 10V Example 14 The charge generation layer and the charge transport layer of the electrophotographic photosensitive member prepared in Example 2 were coated in reverse order. An electrophotographic photoreceptor was prepared and the charging characteristics were evaluated by the same method as in Example 1. However, the charging was positive.

V _O : + 690V E1 / 2: 4.3lux · sec Example 15 On the charge generation layer prepared in Example 2, 5 g of 2,4,7-trinitro-9-fluorene and poly-4,4′-dioxydiphenyl were added. -2,2-Propane carbonate (molecular weight 300,000) 5g
Was dissolved in 70 ml of chlorobenzene to form a charge transport layer by coating the solution to a film thickness of 15 μm and drying.

The charging characteristics of the produced electrophotographic photosensitive member were evaluated in the same manner as in Example 1. However, the charging was positive.

V _O : + 695V E1 / 2: 5.1ux · sec Example 16 2,4,7-trinitro-9-fluorenone 5 g and poly-N
A charge transfer complex compound was prepared by dissolving 5 g of vinylcarbazole (number average molecular weight 300,000) in 70 ml of tetrahydrofuran. This charge transfer complex was dispersed by adding 1 g of Exemplified Pigment (2-5) to a solution of 5 g of polyester (trade name: Byron, manufactured by Toyobo Co., Ltd.) in 70 ml of tetrahydrofuran. This dispersion was applied onto the undercoat layer similar to that in Example 1 and dried to form a photosensitive layer having a film thickness of 16 μm.

The charging characteristics of the produced electrophotographic photosensitive member were evaluated in the same manner as in Example 1. The charging was positive.

V _O : + 680V E1 / 2: 4.7lux · sec [Effect of the invention] In the electrophotographic photoreceptor of the present invention, since the azo pigment having a specific structure is used in the photosensitive layer, the generation efficiency of charge carriers in the photosensitive layer or One or both of the injection efficiencies are improved, and the remarkable effect is obtained that characteristics such as sensitivity and potential stability during repeated use are obtained.

Claims (3)

(57) [Claims] 1. In an electrophotographic photoreceptor having a photoconductive layer containing an azo pigment represented by the following general formula (1) on a conductive support, at least one Cp in the general formula (1) is represented by the general formula (1). An electrophotographic photosensitive member characterized by being a coupler residue shown in 2). ArN = N-Cp) _i (1) In the formula, Ar represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent which may be bonded via a bonding group, and Cp is It represents a coupler residue having a phenolic hydroxyl group, and i represents an integer of 1, 2, 3 or 4. In the formula, R ₁ , R ₂ , R ₃ and R ₄ are the same or different and each represent a hydrogen atom, an alkoxy group, a disubstituted amino group, a halogen atom,
A nitro group, a cyano group, a trifluoromethyl group, an optionally substituted alkyl group, an aryl group or an aralkyl group, Z ₁ and Z ₂ are the same or different and each represents an oxygen atom or a sulfur atom, j and k is 1, 2, 3, 4 or 5, 1 and m are 1, 2, 3 or 4, and n is an integer of 0 or 1. 2. The electrophotographic photosensitive member according to claim 1, which has a photoconductive layer containing an azo pigment represented by the following general formula (3) on a conductive support. In the formula, Ar represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent, R ₁ , R ₂ , R ₃ and R ₄ Are the same or different and represent a hydrogen atom, an alkoxy group, a disubstituted amino group, a halogen atom, a nitro group, a cyano group, a trifluoromethyl group, an optionally substituted alkyl group, an aryl group or an aralkyl group, Z ₁ and Z ₂ are the same or different and each represents an oxygen atom or a sulfur atom, and j and k are 1, 2, 3, 4
Alternatively, 5, 1 and m are 1, 2, 3 or 4, n is 0 or 1, and i is an integer of 1, 2, 3 or 4. 3. An electrophotographic photosensitive member according to claim 1, wherein at least two layers of a charge generating layer containing an azo pigment represented by the general formulas (1) and (2) and a charge transporting layer are provided on a conductive support. .