JPH03291667A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain superior characteristics in sensitivity and potential stability at the time of repeated uses by using an azo pigment specified in structure for a photosensitive layer. CONSTITUTION:The azo pigment to be used is represented by formula I in which at least one of couplers (Cp)s is represesnted by formula II; Aris an optionally substituted aromatic or heterocyclic group optionally linked through a bonding group: Cp is a coupler group with a phenolic OH group; i is an integer of 1-4; each of R1-R4 is H, alkoxy, disubstituted amino group or the like, independent of each other; each of Z1 and Z2 is 0 or S, independent of each other; each of j and k is an integer or 1-5; each of l and m is 0 or 1, thus permitting practicable high sensitivity characteristics and stable potential characteristics at the time of repeated use to be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor containing an azo pigment having a coupler component having a specific structure.

[Prior Art] Conventionally, as electrophotographic photoreceptors using inorganic photoconductive substances, those using selenium, cadmium sulfide, zinc oxide, etc. are widely known.

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

Electrophotographic photoreceptors using organic photoconductive substances have good film forming properties, can be produced by coating, and have extremely high productivity.
It has the advantage of being able to provide an inexpensive photoreceptor. In addition, it has the advantage that color sensitivity can be freely controlled by selecting the sensitizers used, such as dyes and pigments, and has been extensively studied. Particularly recently, with the development of a functionally separated photoreceptor, which has an organic photoconductive pigment as a charge generation layer and a charge transport layer made of the aforementioned photoconductive polymer or low-molecular organic conductive substance, Significant improvements have been made in the sensitivity and durability, which were considered to be drawbacks of electrophotographic photoreceptors.

Many pigments have been proposed for use in organic electrophotographic photoreceptors, but azo pigments in particular have not been widely studied because pigments with various properties can be easily synthesized by combining amine components and coupler components. However, there are problems with sensitivity and potential stability during repeated use, and only a few materials are in practical use.

Coupler components used in such azo pigments include naphthol AS couplers described in JP-A No. 47-37543, benzcarbazole couplers described in JP-A-58-122967, etc. Naphthalimide couplers described in Japanese Patent Laid-open No. 54-79632 and helinone couplers described in Japanese Patent Application Laid-Open No. 176055/1987 are already known.

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel electrophotographic photoreceptor, and to provide an electrophotographic photoreceptor that has practical high sensitivity characteristics and stable potential characteristics during repeated use. It is.

[Means for Solving the Problems, Effects] 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. The electrophotographic photoreceptor is characterized in that at least one of Cp is a coupler residue represented by the general formula (2).

Ar+: N=N-Cp), (1) where Ar represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent which may be bonded via a bonding group, Cp represents a coupler residue having a phenolic hydroxyl group, and i represents an integer of 1.2.3 or 4.

In the formula, R,, R,, Ra and R4 are the same or different and are a hydrogen atom, an alkoxy group, a di-substituted amino group, a halogen atom, a nitro group, a cyano group, a trifluoromethyl group,
represents an alkyl group, aryl group or aralkyl group which may have a substituent, Z and Z2 are the same or different and represent an oxygen atom or a sulfur atom, j and k are l, 2
．． 3.4 or 5, °C and m are 1.2.3 or 4,
n represents an integer of O or 1.

Specific examples of Ar in general formula (1) include aromatic hydrocarbon rings such as benzene, naphthalene, fluorene, phenanthrene, anthracene, and pyrene, furan, thiophene, pyridine, indole, benzothiazole, carbazole, acridone, and dibenzothiophene. , heteroaromatic rings such as benzoxazole, benzotriazole, oxadiazole, thiazole, etc., 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, diphenyl ether, benzophenone, Examples include stilbene, distyrylbenzene, tetraphenyl-p-phenylenediamine, and tetraphenylbenzidine.

Examples of substituents that the aromatic hydrocarbon group or aromatic heterocyclic group that may be bonded via the above-mentioned bonding group include alkyl groups such as methyl, ethyl, propyl, butyl, methoxy, ethoxy, etc. Examples include alkoxy groups, dialkylamino groups such as dimethylamino and diethylamino, halogen atoms such as fluorine, chlorine, and bromine, hydroxy groups, nitro groups, cyano groups, and halomethyl groups.

- Specific examples of R1, R2, R3, and R4 in formula (2) include groups such as methyl, ethyl, n-propyl, and n-butyl as alkyl groups, and phenyl, naphthyl, pyrenyl, and anthryl as aryl groups. groups such as, aralkyl groups such as benzyl, phenethyl, naphthylmethyl, alkoxy groups such as methoxy, ethoxy, butoxy, phenoxy, di-substituted amino groups such as dimethylamino, diethylamino, and halogen atoms. Examples include fluorine, chlorine, bromine, and iodine.

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

In the above-mentioned formulas (4), (5), and (6), X is a naphthalene ring which may be fused with a benzene ring and have a substituent;
Residues necessary to form anthracene ring, carbazole ring, benzcarbazole ring, dibenzofuran ring, etc. are shown.

R6, Rs is a hydrogen atom, an alkyl group that may have a substituent, an aryl group, an aralkyl group, a heterocyclic group, or Rs
, represents a cyclic amino group containing a nitrogen atom to which Ra is bonded,
R7 represents a hydrogen atom, an alkyl group that may have a substituent, an aryl group, an aralkyl group, or a heterocyclic group.

R8 is an alkyl group that may have a substituent, an aryl group,
Indicates an aralkyl group or a heterocyclic group.

Z3 represents an oxygen atom or a sulfur atom, and q represents O or 1
shows.

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

Specifically, 0-phenylene, 0-naphthylene, berinaphthylene, 1.2-antrylene, 3.4-pyrazolediyl, 2,3-pyridinediyl, 4.5-pyridinediyl, 6,7-indazolediyl, 6. Examples include groups such as 7-chiralindiyl.

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, furyl, Examples include groups such as thiazolyl, carbazolyl, dibenzofuryl, benzimidazolyl, benzothiazolyl,
Cyclic amino groups containing a nitrogen atom in the ring include virol,
Examples include cyclic amino groups derived from viroline, pyrrolidine, pyrrolidone, indole, indoline, isoindole, carbazole, benzindole, imidazole, pyrazole, pyrazoline, oxazine, phenoxazine, benzocarbazole, and the like.

Substituents include alkyl groups such as methyl, ethyl, and propyl; alkoxy groups such as methoxy and ethoxy;
Substituted amino groups such as diethylamino and dimethylamino,
Examples include halogen atoms such as fluorine, chlorine, bromine, and iodine, phenylcarbamoyl groups, nitro groups, cyanide groups, and halomethyl groups such as trifluoromethyl.

Representative examples of azo pigments used in the present invention are listed below.

The description method shows only the parts that change in the basic form.

Basic type I Ar-N=N-Cp Exemplary pigment (1-1) 1 2 Exemplary pigment (1-2) Exemplary pigment (2-2) Exemplary pigment (1-3) 5r Exemplary pigment (2-3) Basic type 2 Cp+-N=N-Ar-N=N-Cps Exemplary Pigment (2-1) Exemplary Pigment (2-4) Exemplary Pigment (2-5) Ar2N-@-c=CH-@- Exemplary Pigment ( 2-6) Exemplary Pigment (2-9) Exemplary Pigment (2-10) Exemplary Pigment (2-7) Exemplary Pigment (2-8) Exemplary Pigment (2-11) Exemplary Pigment (2-12) Ar:% Exemplary Pigment (2-13) Exemplary pigment (2-14) Exemplary pigment (2-15) Exemplary pigment (2-18) Exemplary pigment (2-1) Exemplary pigment (2-16) A r: IjiN=N-@ - H3C"CH3 Exemplary pigment (2-17) 0 Exemplary pigment (2 20) Exemplary pigment (2 21) \ Exemplary pigment (2-22) N 3 Exemplary pigment (2-25) Exemplary pigment (2-26) Exemplary pigment (2-23) Exemplary Pigment (2 24) 4 Cp.

Basic type 3 Cp + -N=N-Ar-N=N-C
pz Exemplary Pigment (3-1) Exemplary Pigment (3-2) Exemplary Pigment (3-3) Exemplary Pigment (3-4) Basic type 4 Cp・-N″N, /N″N-Cp・r Cps -N=N N=N-Cp< Exemplary pigment (4-1) Cpl, Cp2, Cpl, Cp4: Exemplary pigment (3-5) Exemplary pigment (4-2) 7 8 Cp+ % Cps, Cps % Cp4
The above-mentioned specific azo pigment in the present invention can be obtained by diazotizing the corresponding amine by a conventional method and coupling it with the coupler represented by formula (2) in an aqueous system in the presence of an alkali, or by converting a diazonium salt into a borofluoride salt. or zinc chloride double salt, etc., and then easily coupled with a coupler in an organic solvent such as N,N-dimethylformamide or dimethyl sulfoxide in the presence of a base such as sodium acetate or triethylamine-triethanolamine. Can be synthesized.

In addition, when synthesizing a disazo pigment in which a coupler other than the coupler represented by general formula (2) coexists in the molecule, the corresponding diamine is tetrazotized by a conventional method, isolated as the above-mentioned soluble salt, and then - Synthesis can be carried out by coupling 1 mol of the coupler shown in (2) and then 1 mol of a different type of coupler, or by protecting one amino group of the diamine with an acetyl group etc. and diazotizing it to form the general formula ( After coupling the coupler shown in 2),
It can be synthesized by hydrolyzing the protecting group with hydrochloric acid or the like, diazotizing it again, and coupling it with another type of coupler.

Trisazo pigments and tetrakisazo pigments in which a coupler other than the coupler represented by general formula (2) coexists in the molecule are also synthesized in the same manner.

The electrophotographic photoreceptor of the present invention has the general formula (
It has a photosensitive layer containing the azo pigments shown in 1) and (2). The form of the photosensitive layer may be any known form, but - the photosensitive layer containing the azo pigment represented by formulas (1) and (2) is used as a charge generation layer, and the charge transporting substance is contained therein. A functionally separated photosensitive layer in which a charge transport layer is laminated is particularly preferred.

The charge generation layer can be formed by coating a coating liquid in which the above-mentioned azo pigment is dispersed together with a binder resin in a suitable solvent on a conductive support by a known method, and the film thickness thereof is, for example, 5 μm. Below, preferably 0.1
A thin film layer of ~IILm is desirable.

The binder resin used in this case is selected from a wide range of insulating resins or organic photoconductive polymers, including polyvinyl butyral, polyvinylbenzal, polyarylate, polycarbonate, polyester, phenoxy resin, cellulose resin, acrylic resin, polyurethane. etc., and the amount used is 8% in terms of content in the charge generation layer.
It is 0% by weight or less, preferably 40% by weight or less.

The solvent used is preferably selected from those that dissolve the resin described above but do not dissolve the charge transport layer or undercoat layer described later.

Specifically, ethers such as tetrahydrofuran and 1,4-dioxane, ketones such as cyclohexanone and methyl ethyl ketone, amides such as N,N-dimethylformamide, esters such as methyl acetate and ethyl acetate, toluene, xylene, Examples 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 trichlorethylene.

The charge transport layer is laminated above or below the charge generation layer, and has the function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them.

The charge transport layer is formed by dissolving a charge transport material in a solvent together with an appropriate binder resin as necessary and coating the layer, and the film thickness is generally 5 to 40 um, but 1.
5 to 30 um is preferable.

Charge transport substances include electron transport substances and hole transport substances. Examples of electron transport substances include 2゜4,7-trinitrofluorenone, 2.4,5゜7-titranitrofluorenone, chloranil, and tetranitrofluorenone. Examples include electron-withdrawing substances such as cyanoquinodimethane, and polymerization of these electron-withdrawing substances.

1 2 Hole transporting substances include polycyclic aromatic compounds such as pyrene and anthracene, carbazole series, indole series, imidazole series, oxazole series, thiazole series, oxadiazole series, pyrazole series, pyrazoline series, thiadiazole series, and triazole series. Heterocyclic compounds such as compounds, p-
Hydrazone-based compounds such as diethylaminobenzaldehyde-N,N-diphenylhydrazone, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, α-phenyl-4°-N,N-diphenylaminostilbene, 5-[ Styryl compounds such as 4-(di-p-tolylamino)benzylidene] -5H-dibenzo[a,d]cycloheptene, benzidine compounds, triarylmethane compounds, triphenylamine, or groups consisting of these compounds Examples include polymers having it in the chain or side chain (eg, poly-N-vinylcarbazole, polyvinylanthracene, etc.).

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

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

Examples of the conductive support on which the photosensitive layer is formed include aluminum, aluminum alloy, copper, zinc, stainless steel,
vanadium, molybdenum, chromium, titanium, nickel,
Indium, gold, platinum, etc. are used. Plastics (e.g. polyethylene, polypropylene,
Polyvinyl chloride, polyethylene terephthalate, acrylic resin, etc.) or conductive particles (e.g. carbon black, silver particles, etc.) are coated on a plastic or metal substrate with a suitable binder resin, or conductive particles are coated on plastic or paper. An impregnated support or the like can be used.

An undercoat layer having barrier and adhesive functions can also 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, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, aluminum oxide, or the like.

The thickness of the undercoat layer is 5 μm or less, preferably 01 to 3 μm.
is appropriate.

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

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

The pigments used in any electrophotographic photoreceptor may be azo pigments represented by general formulas (1) and (2), and their crystalline forms may be amorphous or crystalline. (
It is also possible to use a combination of two or more types of azo pigments shown in 1) and (2) or in combination with a known charge generating substance.

The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines, but also in a wide range of electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

[Example] Examples 1 to 9 5 g of methoxymethylated nylon (weight average molecular weight: 32,000) and 10 g of alcohol-soluble copolymerized nylon (weight average molecular weight: 29,000) were placed on an aluminum substrate in 95 g of methanol.
A solution dissolved in the above was applied with Mayerba 56- to form an undercoat layer having a thickness of 1 μm after drying.

Next, add 5 g of exemplified pigment (2-1) to 95 g of cyclohexanone.
2 g of butyral resin (butyralization degree 63 mol%)
was added to the dissolved solution and dispersed in a sand mill for 20 hours.

This dispersion was applied onto the previously formed undercoat layer using a Mayer bar so that the film thickness after drying would be 0.2 μm, and dried to form a charge generation layer.

Next, 5 g of a hydrazone compound shown by the following structural formula and 5 g of polymethyl methacrylate (number average molecular weight 100,000) were dissolved in 40 mQ of toluene, and this was placed on a Meyer bar so that the dry film thickness was 20 tLm. Apply with
It was dried to form a charge transport layer, and the electrophotographic photoreceptor of Example 1 was prepared.

Electrophotographic photoreceptors corresponding to Examples 2 to 9 were prepared in exactly the same manner using other exemplary pigments in place of exemplary pigment (2-1).

The prepared electrophotographic photoreceptor was corona charged at 15 KV using an electrostatic copying paper tester Model 5P-428 manufactured by Kawaguchi Denki ■, held in a dark place for 1 second, and then exposed to light at an illuminance of 10 lux to determine the charging characteristics. I looked into it.

The charging characteristics include the surface potential (Vo) and the amount of exposure required to attenuate the potential by half (El/2) after being left in the dark for 1 second.
) was measured. Show the results.

1 2-1 710 2,02
2-2 705 1.83
2-4) 695 3.94
2-7 700 3.35
2-9 680 2.16 (
2-13) 715 3, 27 (2
-23) 690 4. 58 (3
-1) 720 2.39 (3-
4) 710 2.5 Comparative Examples 1 to 3 Completely the same as each example except that the azo pigments used in Examples 1.3 and 6 were replaced with comparative pigments (A) to (C) shown by the following structural formulas. An electrophotographic photoreceptor was prepared using the same method, and its charging characteristics were evaluated in the same manner.

Comparative pigment (A) Comparative pigment (B) Comparative pigment (C) 1 (A) 690 7
．． 82 (B) 670
8.33 (C) 705
6.2 From these results, it can be seen that the electrophotographic photoreceptor 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, variations in bright area potential and dark area potential during repeated use were measured.

As a method, the electrophotographic photoreceptor was attached to the cylinder of an electrophotographic copying machine equipped with a -6.5 KV corona charger, an exposure optical system, a developing device, a transfer charger, a static elimination exposure optical system, and a cleaner. This copying machine is configured to produce an image on transfer paper as the cylinder is driven.

Using this copying machine, the initial dark potential V. and bright area potential VL
were set at around -700V and -200V, respectively, and the amount of variation in dark area potential (ΔV,) and the amount of variation in bright area potential (Δ■1) when used 5,000 times was measured. Show the results. Note that a negative sign in the potential variation amount represents a decrease in the absolute value of the potential, and a positive sign represents an increase in the absolute value of the potential.

10 -10 011
-5 +1012
A polyvinyl alcohol undercoat layer having a thickness of 0.5 μm was formed on the aluminum surface of a 0+10 aluminum vapor-deposited polyethylene terephthalate film. The dispersion of the disazo pigment used in Example 1 was applied thereon using a Mayer bar and dried to form a charge generation layer having a thickness of 0.2 μm.

Next, 5 g of a styryl compound having the following structural formula and Comparative Example 4.-
6 The amount of potential fluctuation during repeated use of the electrophotographic photoreceptors prepared in Comparative Examples 1 to 3 was measured in the same manner as in Example 10. Show the results.

4 -85 +955
-60 +856
-55 +60 From the above results, it can be seen that the electrophotographic photoreceptor of the present invention has little potential fluctuation during repeated use.

Example 13 5 g of polyarylate (condensation polymer of bisphenol A and terephthalic acid-isophthalic acid) was added to 40 g of tetrahydrofuran.
Apply the solution dissolved in mg on the charge generation layer, dry it,
A charge transport layer having a thickness of 20 um was formed. The charging characteristics and durability characteristics of the produced electrophotographic photoreceptor were measured in the same manner as in Examples 1 and 10. Show the results.

Vo +-705V El/2 +2.3j2ux-sec ΔVo Knee 5V ΔVL: +10V Example 14 An electrophotographic photoreceptor in which the charge generation layer and charge transport layer of the electrophotographic photoreceptor prepared in Example 2 were applied in the reverse order. create and
The charging characteristics were evaluated in the same manner as in Example 1. However, the charging was positive.

V,: +690V El/2: 4.3I2ux-sec Example 15 5 g of 2.4°7-dolinitro-9-fluorene and poly-44°-dioxydiphenyl-2 were placed on the charge generation layer prepared in Example 2. , 2-propane carbonate (molecular weight 3
A solution obtained by dissolving 5 g of chlorobenzene in 70 ml of chlorobenzene was applied to a film thickness of 15 μm and dried to form a charge transport layer.

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

V,:+695V El/2:5. ll2ux-sec Example 16 5 g of 2.4.7-dolinitro-9-fluorenone and 5 g of poly-N-vinylcarbazole (number average molecular weight 300,000)
A charge transfer complex compound was prepared by dissolving the following in 70 mj2 of tetrahydrofuran. This charge transfer complex is used as an example pigment (2
-5) Ig is polyester (product name Byron, Toyobo ■
Co., Ltd.) was dissolved in 70 ml of tetrahydrofuran and dispersed. This dispersion was applied onto the same subbing layer as in Example 1 and dried to form a photosensitive layer with a thickness of 16 μm.

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

Vo: +680V El/2+4.7j2ux-sea [Effects of the Invention] The electrophotographic photoreceptor of the present invention uses an azo pigment with a specific structure in the photosensitive layer, thereby improving the generation efficiency or injection efficiency of charge carriers inside the photosensitive layer. Either one or both of these characteristics are improved, resulting in the remarkable effect of obtaining excellent characteristics in sensitivity and potential stability during repeated use.

Claims (1)

[Claims] 1. 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 of Cp in general formula (1) is represented by general formula (2)
An electrophotographic photoreceptor characterized by having a coupler residue represented by: Ar■N=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, Cp represents a coupler residue having a phenolic hydroxyl group, and i represents an integer of 1, 2, 3 or 4. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (2) In the formula, R_1, R_2, R_3 and R_4 are the same or different and represent a hydrogen atom, an alkoxy group, a di-substituted amino group, a halogen atom, a nitro group, a cyano group, a tri-substituted amino group, etc. It represents a fluoromethyl group, an alkyl group, an aryl group, or an aralkyl group that may have a substituent, Z_1 and Z_2 are the same or different and represent an oxygen atom or a sulfur atom, and j and k are 1, 2, 3, 4 or 5, l and m are 1, 2,
3 or 4, n represents an integer of 0 or 1. 2. The electrophotographic photoreceptor according to claim 1, which has a photoconductive layer containing an azo pigment represented by the following general formula (3) on a conductive support. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (3) In the formula, Ar represents an aromatic hydrocarbon group or an aromatic heterocyclic group that may be bonded via a bonding group or may have a substituent. R_1, R_2, R_3 and R_4 are the same or different and are a hydrogen atom, an alkoxy group, a di-substituted amino group, a halogen atom, a nitro group, a cyano group, a trifluoromethyl group, an alkyl group which may have a substituent. , represents an aryl group or an aralkyl group, Z_1 and Z_2 are the same or different and represent an oxygen atom or a sulfur atom, j
and k is 1, 2, 3, 4 or 5, l 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. The electrophotographic photoreceptor according to claim 1, wherein at least two layers, a charge generation layer and a charge transport layer containing an azo pigment represented by formulas (1) and (2), are provided on a conductive support.