JPH07271071A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic photoreceptor having high sensitivity and high durability. CONSTITUTION:This electrophotographic photoreceptor has a photosensitive layer contg. a bisazo compd. represented by formula I on the electric conductive substrate. In the formula I each of Ar1 and Ar2 is arylene or a divalent residue of a hetero rind, this arylene or residue may have a substituent, and way by different from each other. Each of K1 and K2 is a residue of a coupler having a hydroxyl group, K1 and K2 may be different from each other and X is a group represented by formula II or III. In the formula II, Y is a trivalent residue of an arom. hydrocarbon or a hetero ring, this residue may have a substituent. In the formula III, Ar3 is arylene or a divalent residue of a hetero ring, this arylene or residue may have a substituent, Z is a trivalent residue of an arom. hydrocarbon or a hetero ring and this residue may have a substituent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrophotographic photoreceptor. More specifically, the present invention relates to a high-sensitivity electrophotographic photoreceptor containing a novel bisazo compound.

[0002]

2. Description of the Related Art As a photoconductor for electrophotography, a photoconductor using an inorganic photoconductive substance such as selenium, cadmium sulfide and zinc oxide has been used in the past, but recently, it is non-polluting. An organic photoconductive compound having many advantages such as easy manufacturing and handling, good image quality, and easy production of photoconductors of various shapes such as drums, sheets and belts (hereinafter referred to as "photoconductive compound"). So-called OPC photoconductors using OPC (abbreviated as OPC) have come to be used for plain paper copying machines and printers, and the proportion thereof is increasing year by year.

[0003]

OPC photoconductors have many advantages over conventional inorganic photoconductors, but they are inferior in sensitivity and durability, and currently they are mainly low speed. Used in the machine field. Therefore, development of OPC having excellent sensitivity and durability is desired.

Azo compounds have been widely studied as charge generation materials for their high sensitivity and high durability because of their ease of synthesis. However, most of them are obtained by an azo coupling reaction between a diazonium salt and a coupler, and it is difficult to remove impurities such as an alkali salt taken in the product solid. This impurity often causes deterioration of the sensitivity charging property.

In order to easily remove these impurities, it is desirable to be able to easily purify after the azo coupling reaction. For this purpose, it is preferable that the monoazo compound is first synthesized and purified, and then converted into the disazo compound by the second reaction. Synthesis of an azo-based charge generating material by this method includes an example of condensation of a monoazo compound having an aldehyde group and a diamine compound, such as a bisazo compound having an azomethine group disclosed in JP-A-56-119134. However, the current situation is that it has not reached a practical level due to insufficient sensitivity.

[0006]

Therefore, as a result of intensive investigations by the present inventors on a novel OPC in order to obtain a highly sensitive and highly durable electrophotographic photoreceptor, a specific bisazo compound is preferable. The present invention has been discovered and the present invention has been reached.

The bisazo compound of the present invention is disclosed in JP-A-56-
Similar to the one disclosed in Japanese Patent No. 119134, by thoroughly purifying the monoazo compound having an azomethine group and the starting aldehyde group and the diamine compound, respectively, and then condensing the mixture, impurities can be suppressed. In the present invention, it has been found that by using a bisazo compound obtained by using a specific diamine compound as a raw material, a photoreceptor having extremely high sensitivity and high durability can be obtained as compared with a known one. That is, the gist of the present invention is to provide a bisazo compound represented by the following general formula [I] on a conductive support.

[0008]

Embedded image K ₁ -N = N-Ar ₁ -CH = N-X-N = CH-Ar ₂ -N = N-K ₂ [I] (in the general formula [I], Ar ₁ and Ar ₂ are And each independently represent an arylene group or a divalent heterocyclic residue, which may have a substituent and may be the same or different. K ₁ and K ₂ are independently a hydroxyl group. Which may be the same or different, and X represents the following general formula [IIa] or [IIb].

[0009]

[Chemical 5] (In the formula, Y represents a trivalent aromatic hydrocarbon residue or a trivalent heterocyclic residue, which may have a substituent.)

[0010]

[Chemical 6] (In the formula, Ar ₃ represents an arylene group or a divalent heterocyclic residue, which may have a substituent, and Z represents a trivalent aromatic hydrocarbon residue or a trivalent heterocyclic residue. , Which may have a substituent), and a photosensitive layer containing a substituent.

The present invention will be described in detail below. The bisazo compound contained in the electrophotographic photoreceptor of the present invention has a structure represented by the above general formula [I]. In the general formulas [I] and [IIb], Ar ₁ , Ar ₂ and Ar
₃ is an arylene group such as a phenylene group, a naphthylene group, or an anthracenylene group; a divalent pyrrole ring residue,
It represents a divalent heterocyclic residue such as a thiophene ring residue and a furan ring residue, which may be the same or different from each other. Of these, a phenylene group and a naphthylene group are preferable, and a phenylene group is particularly preferable.

These arylene group and divalent heterocyclic residue may have a substituent, and as the substituent,
Hydroxyl group; halogen atom such as chlorine atom, bromine atom, iodine atom; alkyl group such as methyl group, ethyl group, propyl group, butyl group and hexyl group; alkoxy group such as methoxy group, ethoxy group, butoxy group; allyl group An aralkyl group such as a benzyl group, a naphthylmethyl group or a phenethyl group; an aryloxy group such as a phenoxy group or a triloxy group; an arylalkoxy group such as a benzyloxy group or a phenethyloxy group; an aryl group such as a phenyl group or a naphthyl group However, it is particularly preferably unsubstituted.

X is selected from the structures represented by the general formulas [IIa] and [IIb], where Y and Z are trivalent aromatic hydrocarbon residues derived from benzene ring, naphthalene ring, anthracene ring, phenanthrene ring and the like. Group; or a trivalent heterocyclic residue derived from a pyridine ring, a pyrimidine ring, a furan ring, a thiophene ring, etc., and the heterocycle is preferably an aromatic heterocycle, and a heterocycle residue containing a nitrogen atom in the ring. Groups are preferred. Of these, a benzene ring and a naphthalene ring skeleton are preferable. These trivalent aromatic hydrocarbon residues or trivalent heterocyclic residues may have the same substituents as Ar ₁ , Ar ₂ and Ar ₃ described above, but are preferably unsubstituted.

K ¹ and K ² are coupler residues each containing a hydroxyl group having a coupling ability, and examples thereof include the groups represented by the following general formulas [III] to [VII]. The hydroxyl group having a coupling ability refers to a group that imparts a property capable of coupling with a diazonium salt to an aromatic ring or the like to which the hydroxyl group is bound.

[0015]

[Chemical 7]

In the general formula [III], U 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, benzonaphthofuran ring or diphenylene sulfide ring. Or a residue necessary for forming a heterocycle, wherein R ¹ and R ² are a hydrogen atom; an alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group; a benzyl group, a phenethyl group, a naphthylmethyl group, etc. Aralkyl group; phenyl group, diphenyl group, naphthyl group and other aryl groups; carbazole group, dibenzofuran group, benzimidazolone group, benzthiazole group, thiazole group, pyridine group and other hetero groups; or R ¹ and R ² bond The following shows a cyclic amino group formed with a nitrogen atom. R ¹ and R ² may be the same group or different groups, but from the viewpoint of sensitivity,
It is preferable that one is a hydrogen atom and the other is a group other than a hydrogen atom. All of U, R ¹ and R ² may have a substituent. P represents an oxygen atom or a sulfur atom, and an oxygen atom is preferable. n represents either 0, 1 or 2,
Or 1 is preferred.

[0017]

[Chemical 8]

In the general formulas [IV] and [V], R ³ represents the same group as R ¹ and R ² .

[0019]

[Chemical 9]

General formulas [VI-a, b], [VII-a, b]
In the formula, V is a divalent group of an aromatic hydrocarbon or a heterocyclic ring of 2
Indicates a valent group. The heterocycle preferably contains a nitrogen atom.
Examples of the divalent group of the aromatic hydrocarbon include a divalent group of a monocyclic aromatic hydrocarbon such as an o-phenylene group; an o-naphthylene group, a peri-naphthylene group, a 1,2-anthraquinonylene group, Examples thereof include divalent groups of condensed polycyclic aromatic hydrocarbons such as 9,10-phenanthrylene group.

Examples of the heterocyclic divalent group containing a nitrogen atom in the ring include, for example, 3,4-pyrazolediyl group and
5 such as 2,3-pyridinediyl group, 5,5-pyrimidinediyl group, 6,7-indazolediyl group, 5,6-benzimidazolediyl group and 6,7-quinolinediyl group
Examples thereof include a 10-membered ring nitrogen atom, and preferably a heterocyclic divalent group containing 2 or less nitrogen atoms in the ring.

In consideration of sensitivity and durability, V is an o-phenylene group, an o-naphthylene group, a peri-naphthylene group, a 2,3-pyridinediyl group, a 4,5-pyrimidinediyl group, particularly an o-phenylene group. A phenylene group and an o-naphthylene group are preferred. In the present invention, the divalent group of these aromatic hydrocarbons and the divalent group of the heterocycle used as V may have a substituent. Examples of the substituent include an alkyl group such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, and an n-hexyl group; a methoxy group, an ethoxy group, and propoxy group. Group, alkoxy group such as butoxy group; hydroxyl group; nitro group; cyano group; amino group; substituted amino group such as dimethylamino group, diethylamino group, dibenzylamino group;
Halogen atom such as fluorine atom, chlorine atom, bromine atom, iodine atom; carboxyl group; alkoxycarbonyl group such as ethoxycarbonyl group; carbamoyl group; aryloxy group such as phenoxy group; arylalkoxy group such as benzyloxy group; phenyloxycarbonyl Examples thereof include aryloxycarbonyl groups and the like. Of these, an alkyl group, an alkoxy group, a nitro group, a halogen atom, a hydroxyl group and a carboxyl group, particularly a methyl group, a methoxy group, a nitro group, a chlorine atom and a hydroxyl group are preferable. Specific examples of these bisazo compounds are shown in Table 1, but are not limited to these.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

[Table 5]

[0028]

[Table 6]

The bisazo compound of the present invention is, for example, a monoazo compound represented by the following general formula [VIII]

[0030]

Embedded image _{K n -N = N-Ar n} -CHO [VIII] (wherein, n = 1 or _{2, K 1, K 2,} Ar 1, Ar 2 has the same meaning as in the general formula [I] .) And a diamine represented by the following general formula [IX]:

[0031]

Embedded image H ₂ N—X—NH ₂ [IX] (where X has the same meaning as in the above formula [I]).

It can be obtained by reacting with and in an organic solvent such as acetic acid. Monoazo compounds and diamines, respectively, can be sufficiently purified by recrystallization, reprecipitation, or other purification methods, and alkalis that could not be completely removed by the synthetic method by the azo coupling reaction between the bisdiazonium salt and the coupler. Impurities in the particles such as salt can also be removed. In the formula [I], K ₁ , Ar ₁ and K ₂ , Ar
_When a bisazo compound different from ₂ is obtained, the formula [VII
As the monoazo compound of [I], two or more different compounds may be used. The monoazo compound represented by the general formula [VIII] can be obtained by a known method by subjecting a corresponding coupler and a diazonium salt to a coupling reaction in water or an organic solvent.

The electrophotographic photoreceptor of the present invention has a photosensitive layer containing one or more bisazo compounds represented by the general formula [I]. Various types of photosensitive layers are well known, but any type thereof may be used in the photoreceptor of the present invention. Particularly preferred is a laminated photoreceptor in which a bisazo compound of the present invention is dispersed in a binder as a charge generating material, and this is used as a charge generating layer, and a charge transporting layer including a known charge transporting material is laminated, A single-layer type photoreceptor in which a well-known charge transporting material is added to the dispersion layer of the bisazo compound is exemplified.

The bisazo compound represented by the general formula [I] of the present invention has a high charge carrier generation efficiency and a high carrier injection efficiency into the charge transport material, and is a laminated or single layer function-separated photoreceptor. Has excellent performance as a charge generating material. The charge transport material used in combination with the bisazo compound of the present invention is generally classified into two types, an electron transport medium and a hole transport medium, but both can be used in the photoconductor of the present invention, or a mixture thereof. Can also be used. As an electron transport medium, an electron-withdrawing compound having an electron-withdrawing group such as a nitro group, a cyano group, an ester group, for example, 2,4,7-trinitrofluorenone,
Examples include nitrated fluorenone such as 2,4,5,7-tetranitrofluorenone and tetracyanodimethane. Further, as a hole transport medium, an electron-donating organic photoconductive compound such as carbazole, indole,
Heterocyclic compounds such as imidazole, oxazole, thiazole, oxazole, pyrazole, pyrazoline, thiadiazole; triarylalkane derivatives such as triphenylmethane; triarylamine derivatives such as triphenylamine; phenylenediamine derivatives; N-phenylcarbazole derivatives; stilbene Derivatives: hydrazone compounds and the like, in particular, substituted amino groups such as dialkylamino groups and diphenylamino groups, electron-donating groups such as alkoxy groups and alkyl groups, or aromatic compounds substituted with these electron-donating groups A compound having a large electron-donating property in which a group ring group is substituted is included. Further, polymers such as polyvinylcarbazole having a group composed of these compounds in the main chain or side chain can also be mentioned.

The electrophotographic photoreceptor of the present invention can be manufactured by a conventional method. That is, the electrophotographic photoreceptor of the present invention,
It is a laminated type having a charge generating layer containing the bisazo compound of the present invention and a charge transport layer on a conductive support, or a single layer type photoreceptor having a photosensitive layer in which the bisazo compound is dispersed. In addition, an intermediate layer such as an adhesive layer or a blocking layer, a protective layer, or a layer for improving performance such as electrical characteristics or mechanical characteristics may be provided. As the conductive support, any of those known in electrophotographic photoreceptors can be used. Specifically, for example, a metal drum of aluminum, copper or the like, a sheet, a laminate of these metal foils, or a vapor deposit is used. Further, there may be mentioned plastic films, plastic drums, papers, etc. which have been subjected to a conductive treatment by coating a conductive substance such as metal powder, carbon black, copper iodide, or a polymer electrolyte with a suitable binder.
Further, a conductive plastic sheet or drum containing a conductive substance such as metal powder, carbon black or carbon fiber, or a plastic film having a conductive metal oxide layer such as tin oxide or indium oxide on its surface. And so on.

In the above-mentioned laminated type photoreceptor, a charge generating layer is usually formed on a conductive support, and a charge transporting layer is formed thereon, but the reverse construction is also possible. The charge generation layer is formed by applying a coating solution containing the bisazo compound of the present invention and a binder polymer and drying. The bisazo compound may be dissolved, but it is usually applied as a dispersed coating liquid. Solvents for preparing the coating liquid include basic solvents such as butylamine and ethylenediamine; ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as methyl ethyl ketone and cyclohexanone; toluene;
Aromatic hydrocarbons such as xylene; aprotic polar solvents such as N, N-dimethylformamide, acetonitrile, N-methylpyrrolidone and dimethylsulfoxide; alcohols such as methanol, ethanol and isopropanol;
Esters such as ethyl acetate, methyl formate and methyl cellosolve acetate; chlorinated hydrocarbons such as dichloroethane and chloroform.

When the bisazo compound is dispersed, 1
It is necessary to make the particle size below μm, preferably below 0.5 μm. As the binder, styrene, vinyl acetate, acrylic acid ester, methacrylic acid ester, vinyl alcohol, polymers and copolymers of vinyl compounds such as ethyl vinyl ether, phenoxy resin, polysulfone, polyvinyl acetal, polycarbonate, polyester, polyamide, polyurethane, Examples thereof include cellulose ester, cellulose ether, epoxy resin, silicon resin and the like.

The ratio of the bisazo compound of the present invention to the binder polymer is not particularly limited, but generally 5 to 500 parts by weight, preferably 20 to 300 parts by weight of the binder polymer based on 100 parts by weight of the bisazo compound. To use. In addition to the above dispersion stabilizer,
A coating property improver, and further, a dye, an electron-withdrawing compound and other additives for improving the performance may be added. The thickness of the charge generation layer is 0.05 to 5 μm, preferably 0.1 to 2
Set to μm.

One or more of the above charge transport materials are dissolved in the above coating liquid for the charge generating layer, and the film thickness after drying is 5 to 5.
A single-layer type photoreceptor can be obtained by coating on a conductive support so as to have a thickness of 0 μm, preferably 10 to 30 μm. The ratio of the bisazo compound to the binder polymer and the charge transport material is usually 10 to 1000 parts by weight, preferably 30 parts by weight, of the binder polymer to 10 parts by weight of the bisazo compound.
~ 500 parts by weight, 5 to 1000 parts by weight of the charge transport material,
It is preferably 20 to 500 parts by weight.

In the multi-layer type photoreceptor, the charge transport layer is formed by applying a coating solution containing a charge transport material onto the charge generating layer and drying the coating solution. When the charge transporting material is a polymer compound having film-forming properties, the binder polymer may not be used, but may be mixed for improving flexibility. In the case of a low molecular weight compound, a binder polymer is used for forming a film. As the binder polymer, those mentioned above are used, and the amount thereof is usually in the range of 50 to 3000 parts by weight, preferably 70 to 1000 parts by weight, based on 100 parts by weight of the charge transport material.

In addition to the above, various additives can be used in the charge transport layer in order to improve the performance and improve the mechanical strength and durability of the coating film. Examples of such additives include electron-withdrawing compounds and dyes, stabilizers such as ultraviolet absorbers and antioxidants, coatability improving agents, plasticizers, cross-linking agents and the like.
Examples of the electron-withdrawing compound include chloranil and 2,3-
Dichloro-1,4-naphthoquinone, 2-methylanthraquinone, 1-nitroanthraquinone, 1-chloro-5-
Quinones such as nitroanthraquinone, 2-chloroanthraquinone and phenanthrenequinone; aldehydes such as 4-nitrobenzaldehyde; 9-benzoylanthracene, indandione, 3,5-dinitrobenzophenone, 3,3 ', 5,5'-tetra Ketones such as nitrobenzophenone; acid anhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride; tetracyanoethylene, terephthalalmalononitrile, 4-nitrobenzalmalononitrile, 4-benzoyloxybenzalmalononitrile, 4
Cyano compounds such as-(p-nitrobenzoyloxy) benzalmalononitrile; 3-benzalphthalide, 3-
(Α-Cyano-p-nitrobenzal) phthalide, 3-
(Α-Cyano-p-nitrobenzal) -4,5,6,7
Phthalides such as tetrachlorophthalide.

[0042]

EXAMPLES Next, the present invention will be explained more specifically with reference to examples and examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the Reference Examples and Examples, [parts] means [parts by weight].

Reference Example (Synthesis Method of Exemplified Compound 1) 7.3 g of p-aminobenzaldehyde, 25 m of concentrated hydrochloric acid
1, 120 ml of pure water were mixed, 45.6 g of 10% sodium nitrite aqueous solution was added dropwise at 0 ° C., and the mixture was reacted at 0-5 ° C. for 2 hours. This solution was added to a liquid in which 14.2 g of 2-hydroxy-3-naphthoic acid anilide was dissolved in 2 liters of dimethyl sulfoxide, and 147 g of a 32% sodium acetate aqueous solution was added dropwise, and the mixture was reacted at 20 ° C. for 3 hours to obtain dimethylformamide. After recrystallization, 15.3 g (yield 7
2%) of the following monoazo compound was obtained.

[0044]

[Chemical 12]

0.35 g and 150 ml of acetic acid were mixed and reacted under reflux for 3 hours to obtain 0.72 g (yield 59%). The IR chart is shown later (FIG. 1), and the elemental analysis values were as follows.

[0046]

[Table 7] Calculated value as C ₆₇ H ₄₄ N ₈ O ₆ C 76.12% H 4.20% N 10.60% Measured value C 75.9% H 4.28% N 10.48%

The bisazo compounds of the present invention used in the following examples were synthesized by this Reference Example or a method similar thereto.

Example 1 0.4 part of Exemplified Compound 1 in Table 1 was dispersed together with 230 parts of 4-methyl-4-methoxy-pentanone in a sand grinder, and polyvinyl butyral (trade name, manufactured by Sekisui Chemical Co., Ltd., trade name) 0.4 parts of BH-3) was added and dissolved. The obtained dispersion of the azo compound was applied and dried by a wire bar on an aluminum vapor deposition layer vapor-deposited on a polyester film having a thickness of 75 μm so that the dry film thickness was 0.4 g / m ² . The charge generation layer thus obtained has pyrene
90 parts of 2-aldehyde phenylhydrazone and polycarbonate resin (trade name Novarex 7 manufactured by Mitsubishi Kasei Co., Ltd.)
A solution obtained by dissolving 100 parts of 670 parts of dioxane in 670 parts was applied to a dry film thickness of 28 μm to form a charge transport layer. In this way, an electrophotographic photosensitive member having a photosensitive layer composed of two layers was obtained.

The electrophotographic photoreceptor containing the bisazo compound of the present invention has high sensitivity and good color sensitivity, and since light fatigue is particularly small, when it is repeatedly used, the sensitivity, the charging property and the residual potential are reduced. It has little fluctuation, high stability, and extremely excellent durability. Not only electrophotographic plain paper copiers, but laser printers, liquid crystals, shutter printers, LEDs that require particularly stable performance and reliability
It is also a photoconductor suitable for a photoconductor for a printer such as a printer.

The values of the half-exposure amount (E1 / 2) as the sensitivity of these photoconductors are shown in Table-1. The half-exposure amount was measured by using an electrostatic copying paper test device (Model SP-428 manufactured by Kawaguchi Denki Seisakusho) for the photoconductor. First in the dark -6.5
Necessary for charging by corona discharge at kV and exposing the charged voltage (V) at that time with white light with an illuminance of 5lux as sensitivity (E1 / 2 (luxsec)) to attenuate the surface potential to half the initial surface potential. More exposure,
The residual potential (V) after exposure for 10 seconds was determined. In addition,
After repeating the exposure 2000 times, the electrification voltage, the sensitivity and the residual potential were also obtained.

Examples 2 to 5 Example 1 was repeated except that the exemplified compounds 2, 3, 12, and 13 were used instead of the bisazo compound used in Example 1.
An electrophotographic photoreceptor was obtained in exactly the same manner as shown in. Table 2 shows the sensitivity of the charged voltage, the charged voltage after repeating the residual potential 2000 times, and the sensitivity residual potential of these photoconductors. The half-exposure amount was obtained in exactly the same manner as in Example 1. It can be seen that all the photoconductors have good characteristics.

Comparative Examples 1 to 2 Electrons were prepared in the same manner as in Example 1 except that the following known bisazo compounds (i) and (ii) were used in place of the bisazo compound used in Example 1. A photographic photoreceptor was obtained.
The results of these electrical characteristics are also shown in Table 2. It is understood that the sensitivity is poor when these known compounds are used.

[0053]

[Chemical 13]

[0054]

[Table 8]

[0055]

The electrophotographic photoconductor containing the bisazo compound of the present invention has high sensitivity and good color sensitivity, and since light fatigue is small in particular, sensitivity, chargeability, and residual property are remarkably observed when repeatedly used. It has little potential fluctuation, high stability, and extremely excellent durability. In particular, the sensitivity is superior to the compound in which the same type of coupler residue is bound. The photoconductor is suitable not only for electrophotographic plain paper copiers, but also for photoconductors for printers such as laser printers, liquid crystal, shutter printers, LED printers, etc., where performance stability and reliability are particularly required.

[Brief description of drawings]

FIG. 1 shows IR of Exemplified Compound 1 produced by the synthetic method of Reference Example.
chart

Claims (4)

[Claims] 1. A photoconductor for electrophotography, comprising a photosensitive layer containing a bisazo compound represented by the following general formula [I] on a conductive support. [Image Omitted] K ₁ -N = N-Ar ₁ -CH = N-X-N = CH-Ar ₂ -N = N-K ₂ [I] (in the general formula [I], Ar ₁ and Ar ₂ are , Each independently represent an arylene group or a divalent heterocyclic residue, which may have a substituent and may be the same or different. K ₁ and K ₂ are each independently. Represents a coupler residue containing a hydroxyl group, which may be the same or different, and X represents the following general formula [IIa] or [IIb]. (In the formula, Y represents a trivalent aromatic hydrocarbon residue or a trivalent heterocyclic residue, which may have a substituent.) (In the formula, Ar ₃ represents an arylene group or a divalent heterocyclic residue, which may have a substituent, and Z is a trivalent aromatic hydrocarbon residue or a trivalent heterocyclic residue. Which may have a substituent.) 2. The photosensitive layer contains a charge-generating material and a charge-transporting material, and the azo compound represented by the general formula [I] of claim 1 is used as the charge-generating material. Electrophotographic photoconductor. 3. The photosensitive layer has at least a charge generating layer containing a charge generating material, and a charge transporting layer containing a charge transporting material and a binder resin, wherein the charge generating material has the general formula [1]. The electrophotographic photosensitive member according to claim 1, wherein an azo compound represented by the formula [I] is used. 4. The electrophotographic photoreceptor according to claim 3, wherein the charge generation layer contains a charge generation material and a binder resin.