JPH07168379A - 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, K<1> and K<2> are mutually different residues of couplers each contg. a group having coupling ability, one of them is a group represented by formula II and each of rings A, B is a benzene ring which may have a substituent. In the formula II, Z is a divalent heterocyclic group contg. N in the ring or a divalent arom. hydrocarbon group and each of the groups 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 highly sensitive 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.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have developed a novel OP for obtaining a highly sensitive and durable electrophotographic photoreceptor.
As a result of diligent studies on C, the present invention has been found out that a specific bisazo compound is suitable. That is, the gist of the present invention is to provide the following general formula [I] on a conductive support.

[0005]

[Chemical 3]

(In the formula, K ¹ and K ² represent different coupler residues containing a hydroxyl group having a coupling ability, and ^one of K ¹ and K ² is represented by the following formula [II]. The ring and the B ring each represent a benzene ring which may have a substituent.) In the electrophotographic photoreceptor, which has a photosensitive layer containing a bisazo compound represented by

[0007]

[Chemical 4]

(In the formula, Z represents a heterocyclic divalent group containing a nitrogen atom in the ring or an aromatic hydrocarbon divalent group, which may have a substituent.) The invention will be described in detail.

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 formula [I], K ¹ and K ² are different coupler residues containing a hydroxyl group having a coupling ability, and examples thereof include the groups of the following general formulas [II] to [IV]. However, ^one of K ¹ and K ² is
I], preferably [II-a], [II-
b], [III-a] or [III-b]. The group having a coupling ability refers to a group that imparts the ability to couple with a diazonium salt to an aromatic ring to which the group (such as a hydroxyl group) is bonded.

[0010]

[Chemical 5]

In the general formula [II], Z represents a divalent group of aromatic hydrocarbon or a heterocyclic divalent group containing a nitrogen atom in the ring. Examples of the divalent group of aromatic hydrocarbon include o-
Divalent group of monocyclic aromatic hydrocarbon such as phenylene group; o-
Examples thereof include a divalent group of a condensed polycyclic aromatic hydrocarbon such as a naphthylene group, a peri-naphthylene group, a 1,2-anthraquinonylene group, and a 9,10-phenanthrylene group. Examples of the heterocyclic divalent group containing a nitrogen atom in the ring include, for example, 3,4-pyrazolediyl group, 2,3-pyridinediyl group, 5,5-pyrimidinediyl group, and 6,7-indazolediyl group. Group, 5,6-benzimidazolediyl group, 6,7-quinolinediyl group and the like, a nitrogen atom of a 5- to 10-membered ring, preferably a divalent heterocyclic group containing 2 or less nitrogen atoms in the ring, and the like. Can be mentioned. In consideration of sensitivity and durability, Z 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, The o-naphthylene group is preferred.

In the present invention, the divalent group of these aromatic hydrocarbons used as Z and the divalent group of the heterocycle containing a nitrogen atom in the ring may have a substituent. Examples of such a substituent include 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-propyl group.
-Alkyl group such as hexyl group; alkoxy group such as methoxy group, ethoxy group, propoxy group, butoxy group; hydroxyl group; nitro group; cyano group; amino group; substitution of dimethylamino group, diethylamino group, dibenzylamino group, etc. Amino 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; Examples thereof include aryloxycarbonyl groups such as phenyloxycarbonyl group. 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. Since the compound having the group of the formula [II-a] type usually exists as a mixture with the isomer having the group of the formula [II-b] type, in the present invention, the compound having the formula [II-a] is used. ] And the group of the formula [II-b] type are treated as the same group. The same applies to the group of the formula [III-a] type [II
Treated as the same group as the I-b] type group. Other couplers include the following general formula [I] in addition to the above general formula [II].
Examples thereof include those that can be used as couplers for bisazo compounds such as V], [V] and [VI].

[0013]

[Chemical 6]

In the general formula [IV], Y is condensed with a benzene ring to form a naphthalene ring, anthracene ring, carbazole ring,
Residues necessary to form a polycyclic aromatic ring or a heterocycle such as a benzcarbazole ring, a dibenzofuran ring, a benzonaphthofuran ring, and a diphenylene sulfide ring are shown.
R ¹ and R ² are hydrogen atoms; may have a substituent,
Alkyl groups such as methyl group, ethyl group, propyl group, butyl group; aralkyl groups such as benzyl group, phenethyl group, naphthylmethyl group; phenyl group, diphenyl group, naphthyl group, etc. which may have a substituent. Aryl group; carbazole group, dibenzofuran group, benzimidazolone group,
A hetero group such as a benzthiazole group, a thiazole group or a pyridine group; or a group in which a cyclic amino group is formed with a nitrogen atom to which R ¹ and R ² are bonded is shown. 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.

[0015]

[Chemical 7]

In the general formulas [V] and [VI], R ³ represents an alkyl group, an aryl group or an aralkyl group which may have a substituent represented by the same examples as R ¹ and R ² . A ring and B ring in the general formula [I] are halogen atoms (eg, fluorine atom, chlorine atom, bromine atom, etc.)
Or an optionally substituted alkyl group (eg, methyl group, ethyl group, propyl group, iso-propyl group, butyl group, sec-butyl group, t-butyl group, hexyl group, 2-ethylhexyl group, t-octyl group). Group, octyl group, benzyl group, 2-phenylethyl group, α-naphthylmethyl group, β-naphthylmethyl group, etc.) or alkoxy group (for example, methoxy group, ethoxy group, butoxy group, 2-methoxyethoxy group, phenoxymethoxy group). Groups, etc.), cyano groups, optionally substituted amino groups (eg dimethylamino group, diethylamino group, dibenzylamino group etc.), carbamoyl groups, aryloxy groups (eg phenoxy group etc.) . These bisazo compounds are represented by the following general formula [VII]

[0017]

[Chemical 8]

(In the formula, ring A and ring B have the same meaning as in the above-mentioned general formula [I]), the diamine is tetrazotized by a conventional method and coupled with two couplers corresponding to K ¹ and K ^2. By doing so, it can be easily synthesized. Such a coupling reaction may be carried out according to a known method, usually in water and / or an organic solvent such as dimethylformamide and dimethylsulfoxide, at a reaction temperature of 30 ° C. or lower for about 1 to 10 hours.

Typical electrophotographic photoreceptors of the present invention include bisazo compounds shown in Table 1 below. In addition, in Table 1, the bonding positions to the carbon atoms of the A ring and the B ring of K ¹ -N = N- and K ² -N = N- in the above general formula [I] and the kind and the bonding position of the substituent are shown. Are indicated by the following numbers. However, in the case of no substitution, no particular description is given.

[0020]

[Chemical 9]

For example, chlorine atoms are added to the carbon atoms of 2 and 4 and 7
When a methyl group is bonded to the position of -Cl; 2,
4, -CH _3; expressed as 7. If two or more corresponding couplers, for example, k and k ', are used to select the proper reaction conditions and carry out the coupling reaction, a mixture of the following two isomers can be obtained in high purity, and at the same time K ¹ = K compound of compound of ² = k and K ¹ = K ² = k 'also mixed.

[0022]

[Chemical 10]

Here, for example, k-N = N-, k'-N = N
In the table below, the case where-is bonded to the carbon atoms of 3 and 8 respectively and the case where k'-N = N- and k-N = N- are bonded to the carbon atoms of 8 and 3 respectively. so

[0024]

Represented as K ¹ , K ² -N = N-; 3,8.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

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 laminar type 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 carrier transporting medium is laminated, Examples thereof include a single-layer type photoreceptor in which a well-known charge carrier transport medium is added to a dispersion layer of a bisazo compound. The bisazo compound represented by the above general formula [I] of the present invention has high charge carrier generation efficiency and high carrier injection efficiency into the charge carrier transport medium, and the charge generation of the above-mentioned laminated or single layer type function-separated photoreceptor. It has excellent performance as a material.

The charge carrier transport medium 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, and both can be used in the photoconductor of the present invention. Moreover, the mixture can also be used. The electron transport medium is a nitro group, a cyano group,
An electron-withdrawing compound having an electron-withdrawing group such as an ester group, for example, 2,4,7-trinitrofluorenone, 2,
Examples include nitrated fluorenone such as 4,5,7-tetranitrofluorenone and tetracyanodimethane. Further, as a hole transport medium, an electron-donating organic photoconductive compound, for example, a heterocyclic compound such as carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, pyrazole, pyrazoline, thiadiazole; triphenylmethane, etc. Lille alkane derivatives; triarylamine derivatives such as triphenylamine; phenylenediamine derivatives; N-phenylcarbazole derivatives; stilpene derivatives; hydrazone compounds, and the like. Particularly, substituted amino groups such as dialkylamino groups and diphenylamino groups, Alternatively, a compound having a large electron-donating property, which is substituted with an electron-donating group such as an alkoxy group or an alkyl group, or an aromatic ring group substituted with these electron-donating groups, may be mentioned. 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,
On a conductive support, a laminate type having a charge generation layer and a charge transport layer containing the disazo compound of the present invention, or a single layer type photoreceptor having a photosensitive layer in which a bisazo compound is dispersed,
In addition to these, 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 on the charge generating layer, 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. Butylamine as a solvent for coating liquid preparation,
Basic solvents such as ethylenediamine, ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as methylethylketone and cyclohexanone; aromatic hydrocarbons such as toluene and xylene; N, N-dimethylformamide, acetonitrile, N-methylpyrrolidone Aprotic polar solvents such as dimethyl sulfoxide; 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 μm
It is necessary to make the particle diameter m or less, preferably 0.5 μm or less. 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 is used per 100 parts by weight of the bisazo compound. To do. In addition to the above, a dispersion stabilizer, a coatability improving agent, and a dye, an electron-withdrawing compound and other additives for improving the performance may be added to the above coating liquid. The thickness of the charge generation layer is 0.05 to 5 μm, preferably 0.1 to 2 μm.

A conductive support is prepared by dissolving one or more charge carrier transporting media in the coating liquid for the charge generating layer so that the film thickness after drying is 5 to 50 μm, preferably 10 to 45 μm. When applied on top, a single layer type photoreceptor is obtained. The ratio of the bisazo compound to the binder polymer and charge carrier transport medium is usually 10
The binder polymer is 10 to 1000 parts by weight, preferably 30 to 500 parts by weight, and the charge carrier transport medium is 5 to 1000 parts by weight, preferably 20 to 500 parts by weight, based on parts by weight.

In the laminated type photoreceptor, the charge transport layer is formed by applying a coating solution containing a charge carrier transport medium onto the charge generating layer and drying the coating solution. When the charge carrier transport medium is a polymer compound having film-forming properties, the binder polymer may not be particularly 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 50 to 3000 parts by weight, preferably 70 to 1 part by weight per 100 parts by weight of the charge carrier transport medium.
It is in the range of 000 parts by weight. In addition to these, various additives can be used in the charge transport layer for improving performance and improving 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, 2,3-dichloro-1,4-naphthoquinone, 2-methylanthraquinone, 1-nitroanthraquinone, 1-
Quinones such as chloro-5-nitroanthraquinone, 2-chloroanthraquinone and phenanthrenequinone; aldehydes such as 4-nitrobenzaldehyde; 9-benzoylanthracene, indandione, 3,5-dinitrobenzophenone, 3,3 ′, 5 Ketones such as 5′-tetranitrobenzophenone; acid anhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride; tetracyanoethylene,
Cyano compounds such as terephthalalalononitrile, 4-nitrobenzalmalononitrile, 4-benzoyloxybenzalmalononitrile, 4- (p-nitrobenzoyloxy) benzalmalononitrile; 3-benzalphthalide, 3- (α- Cyano-p-nitrobenzal) phthalide, 3- (α-cyano-p-nitrobenzal) -4,
Examples include phthalides such as 5,6,7-tetrachlorophthalide.

[0038]

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 Example of Compound No. 4 2.27 g of 4,4′-diaminobenzanilide was added to 50 parts of water.
ml and 6 ml of concentrated hydrochloric acid and cooled, and 15 ml of a 10% sodium nitrite aqueous solution was added dropwise thereto at 5 ° C or lower,
The mixture was stirred at 2 ° C or lower for 2 hours to be tetrazotized. Next, 8.5 g of 42% borohydrofluoric acid was added to the liquid, and the mixture was stirred at 5 ° C. or lower, and then the precipitated crystals were filtered, washed with a small amount of cold water and cold methanol, and dried to obtain 3.8 g of a tetrazonium salt. 2.1 g of the tetrazonium salt was added to dimethyl sulfoxide 40
It was dissolved in 1.3 ml of naphthol AS, and 2.9 g of a mixture of naphthol AS and 2.9 g of a compound of the following structural formula was added to 450 ml of dimethyl sulfoxide.
10 ml of 0% sodium acetate aqueous solution was added dropwise, and the mixture was stirred as it was for 3 hours. The precipitated crystals are collected by filtration

[0040]

[Chemical 12]

The solid obtained by washing this with diluted acetic acid, water and tetrahydrofuran and then drying was black purple, and did not decompose at 320 ° C. or lower. This was identified as the desired bisazo compound by elemental analysis and infrared absorption spectrum (FIG. 1). Yield is 2.9g
The elemental analysis values were as follows.

[Table 4] Calculated value (%) as C ₄₈ H ₃₀ N ₈ O ₅ C: 72.17 H: 3.78
N: 14.03 Measured value (%) C: 72.28 H: 3.55
N: 14.17 The bisazo compound was obtained as a mixture of the following compounds.

[0042]

[Chemical 13]

In the following examples, the coupler residue is represented by the general formula [II-a], [II-b] or [III-a].
When the groups a] and [III-b] are introduced, four kinds of isomers can be obtained in the same manner, but one of them will be described as a representative. Further, 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 Bisazo compound shown in Reference Example (No. 4 in Table 1)
4 parts of 4-methyl-4-methoxy-pentanone-2 3
Dispersed with a sand grinder together with 0 parts, and polyvinyl butyral (trademark B manufactured by Sekisui Chemical Co., Ltd.)
0.4 parts of H-3) was added and dissolved. The resulting dispersion of the azo compound was applied onto an aluminum vapor deposition layer vapor-deposited on a polyester film having a thickness of 75 μm with a wire bar so that the dry film thickness was 0.4 g / m ² and dried. A solution prepared by dissolving 90 parts of pyrene-2-aldehydephenylhydrazone and 100 parts of a polycarbonate resin (trade name, Novarex 7025, manufactured by Mitsubishi Kasei Co., Ltd.) in 670 parts of dioxane was dried on the charge generation layer thus obtained. Is 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.

Table 2 shows the values of the half-exposure amount (E1 / 2) as the sensitivity of these photoreceptors. The numbers of the bisazo compounds in Table 2 are the numbers in Table 1 above. 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-
Charged by corona discharge at 6.5kV, then illuminance 5
Exposure was performed with white light of lux, and the amount of exposure required for the surface potential to decay to half the initial surface potential was determined.

Comparative Example 1 For comparison with Example 1, a photosensitive member was prepared in the same manner as in Example 1 except that the bisazo compound represented by the following structural formula was used instead of the bisazo compound used in Example 1. did.

[0047]

[Chemical 14] When measured in the same manner as in Example 1, the sensitivity of this photoconductor was 1.67.

[0048]

[Table 5]

[0049]

The electrophotographic photoreceptor 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, residual potential when repeatedly used. It has low 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 is an infrared absorption spectrum diagram of bisazo compound 4 obtained in Reference Example.

Claims (1)

[Claims] 1. A photoconductor for electrophotography, comprising a photosensitive layer containing a bisazo compound represented by the following formula [I] on a conductive support. [Chemical 1] (Wherein, K ^1, K ² represents a coupler residue different from each other and groups having a coupling ability, one of K ^1, K ² are represented by the following formula [II]. In addition, A ring and B Each ring represents a benzene ring which may have a substituent.) (In the formula, Z represents a heterocyclic divalent group containing a nitrogen atom in the ring or an aromatic hydrocarbon divalent group, which may have a substituent.)