JP2653106B2 - Electrophotographic photoreceptor - Google Patents

Description

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.

<Prior Art> Conventionally, photoconductors using inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide have been used as photoconductors for electrophotography. Organic photoconductive compounds (hereinafter referred to as organic photoconductive compounds having many advantages such as easy handling, good image quality, and easy formation of photoconductors of various shapes such as drums, sheets and belts) , Abbreviated as OPC), so-called OPC photoconductors have been adopted for PPCs and printers, and the ratio has been increasing year by year.

<Problems to be Solved by the Invention> OPC photoconductors have many advantages over conventional inorganic photoconductors, but are inferior in sensitivity, durability, etc.
At present, it is mainly used for low-speed machines. For this reason, development of OPC having excellent sensitivity and durability is desired.

<Means for Solving the Problems> As a result of intensive studies on a novel OPC in order to obtain a highly sensitive and highly durable electrophotographic photoconductor,
The present inventors have found that a specific bisazo compound is suitable, and have reached the present invention.

That is, the gist of the present invention is that the following general formula [I] (In the formula, K ¹ and K ² represent a coupler residue containing a hydroxyl group having a coupling ability, K ¹ and K ² may be the same or different, and R ¹ is a hydrogen atom, a lower alkyl group, a lower alkoxy group. Or a halogen atom.) An electrophotographic photoreceptor comprising a photosensitive layer containing a bisazo compound represented by the following formula:

 Hereinafter, the present invention will be described in detail.

The bisazo compound contained in the electrophotographic photoreceptor of the present invention has a structure represented by the aforementioned general formula [I].

In the general formula [I], K ¹ and K ² are coupler residues containing a hydroxyl group having a coupling ability, and examples thereof include the following general formulas [II] to [VI]. In addition, the hydroxyl group having a coupling ability refers to a group that imparts a property capable of coupling with a diazonium salt to a group such as an aromatic ring to which the hydroxyl group is bonded.

In the formula (II), X is condensed with a benzene ring to form a polycyclic aromatic ring or a heterocyclic ring such as a naphthalene ring, an anthracene ring, a carbazole ring, a benzocarbazole ring, a dibenzofuran ring, a benzonaphthofuran ring, or a diphenylene sulfide ring. R ² and R ³ represent a hydrogen atom; a methyl group, an ethyl group, which may have a substituent,
Alkyl groups such as propyl group and butyl group; aralkyl groups such as benzylic, phenethyl and naphthylmethyl groups; aryl groups such as phenyl group, diphenyl group and naphthyl group which may have a substituent; carbazole group and dibenzofuran group A heterocyclic group such as a benzimidazolone group, a benzthiazole group, a thiazole group, a pyridine group; or R ² and
A compound having a cyclic amino group together with the nitrogen atom to which R ³ is bonded is shown. R ² and R ³ 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.

In the formulas [III] and [IV], R ⁴ represents an alkyl group, an aralkyl group or an aryl group which may have a substituent represented by the same examples as R ² and R ³ .

In the formulas [Va, b] and [VI-a, b], Y represents a divalent group of an aromatic hydrocarbon or a divalent group of a heterocyclic ring containing a nitrogen atom in the ring. As the divalent group of the aromatic hydrocarbon, for example, o-
Divalent group of a monocyclic aromatic hydrocarbon such as a phenylene group; condensed polycyclic aromatic hydrocarbon such as an o-naphthylene group, a perinaphthylene group, a 1,2-anthraquinonylene group, a 9,10-phenanthrylene group And a divalent group of hydrogen.

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

When sensitivity and durability are considered, Y is an o-phenylene group, an o-naphthylene group, a peri-naphthylene group,
A 2,3-pyridinediyl group and a 4,5-pyrimidinediyl group, particularly an o-phenylene group and an o-naphthylene group are preferred.

In the present invention, the divalent group of the aromatic hydrocarbon and the divalent group of the heterocyclic ring 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, and an n-
Alkyl groups such as butyl group, i-butyl group and n-hexyl group; alkoxy groups such as methoxy group, ethoxy group, propoxy group and butoxy group; hydroxyl group; nitro group; cyano group; amino group; dimethylamino group and diethylamino A substituted amino group such as a dibenzylamino group; a fluorine atom;
Halogen atoms such as chlorine, bromine and iodine atoms; carboxyl groups; alkoxycarbonyl groups such as ethoxycarbonyl groups; carbamoyl groups; aryloxy groups such as phenoxy groups; arylalkoxy groups such as benzyloxy groups; Aryloxycarbonyl group and the like. Among them, 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 hydroxy group are preferred.

R ¹ in the general formula [I] is a lower alkyl group such as a methyl group, an ethyl group, and a propyl group; a methoxy group;
A lower alkoxy group such as an ethoxy group; a halogen atom such as a chlorine atom, a fluorine atom and a bromine atom.

The bisazo compound of the present invention has, for example, the following general formula (VI
I] (In the formula, R ¹ has the same meaning as in the above general formula [I].) The diamine can be easily synthesized by tetrazotizing by a conventional method and coupling with a corresponding coupler.

According to a known method, such a coupling reaction may be usually performed in water and / or an organic solvent such as dimethylformamide or dimethylsulfoxide at a reaction temperature of 30 ° C. or lower for about 1 hour to 10 hours.

The aromatic diamine represented by the general formula (VII) is
For example, it is produced according to the following reaction formula.

To explain the above reaction formula in detail, for example, in acetic anhydride,
The Parkin reaction is performed under known conditions. Then, under the known combination conditions of iron powder, zinc, tin chloride and hydrochloric acid, acetic acid,
The compound [VII] can be produced in good yield by reduction.

Further, the aromatic diamine of the general formula [VII] can be produced also by the following reaction formula.

The above reaction formula is a mononitro compound [IX] by the Parkin reaction.
After the compound is prepared, the compound and a diazonium salt diazotized by a conventional method are subjected to a mail wine reaction in the presence of cuprous chloride in an acetone solvent to form a compound [VIII], and the compound is reduced in the same manner as described above to obtain a compound. [VII] can be produced.

The electrophotographic photoreceptor of the present invention has a photosensitive layer containing one or more bisazo compounds represented by the above general formula [I]. Various types of photosensitive layers are well known,
In the photoreceptor of the present invention, any of these types may be used. Particularly preferred is a dispersion of the bisazo compound of the present invention as a charge generating material in a binder, which is used as a charge generating layer, including a well-known charge carrier transfer medium.
Examples include a stacked photoconductor in which a charge transfer layer is stacked, and a single-layer photoconductor in which a well-known charge carrier transfer medium is added to a dispersion layer of the above bisazo compound.

The bisazo compound represented by the above general formula [I] of the present invention has a high charge carrier generation efficiency and a high carrier injection efficiency into the charge carrier moving medium. It has excellent performance as a material.

The charge carrier transfer medium used in combination with the bisazo compound of the present invention is generally classified into two kinds, an electron transfer medium and a hole transfer medium, and both can be used for the photoreceptor of the present invention. Can also be used. As an electron transfer medium, an electron-withdrawing compound having an electron-withdrawing group such as a nitro group, a cyano group and an ester group, for example, 2,
Examples include nitrated fluorenone such as 4,7-trinitrofluorenone and 2,4,5,7-tetranitrofluorenone or tetracyanoquinodimethane. Examples of the hole transfer medium include electron-donating organic photoconductive compounds such as carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, virazole, pyrazoline, and thiadiazole; and heterocyclic compounds such as triphenylmethane. Reel alkane derivatives; triarylamine derivatives such as triphenylamine; phenylenediamine derivatives; N-phenylcarbazole derivatives; stilbene derivatives; hydrazone compounds.
A substituted amino group such as a dialkylamino group or a diphenylamino group, or an electron-donating group such as an alkoxy group or an alkyl group, or an electron-donating group substituted with an aromatic ring group substituted with these electron-donating groups has a large electron-donating property. Compounds. Further, a polymer having a group consisting of these compounds in a main chain or a side chain, such as polyvinylcarbazole, may also be used. Among them, hydrazone compounds represented by the following general formula [X] (Wherein, Ar represents a phenyl group, a styryl group, an aromatic hydrocarbon group which may have a substituent such as a naphthyl group, or a heterocyclic group such as a carbazolyl group; R ⁵ and R ⁶ represent a methyl group; An alkyl group such as an ethyl group; an aryl group such as a phenyl group or a naphthyl group; an aralkyl group such as a benzyl group; at least one of R ⁵ and R ⁶ is an aryl group; The hydrazone compound represented by the following formula) is particularly preferred.

The electrophotographic photoreceptor of the present invention can be manufactured according to a conventional method.

That is, the electrophotographic photoreceptor of the present invention usually has, on a conductive support, a laminated type having a charge generation layer containing the bisazo compound of the present invention and a chloride transfer layer, or a photosensitive layer in which a bisazo compound is dispersed. It is a single-layer type photoreceptor having an intermediate layer such as an adhesive layer and a blocking layer, and a layer for improving performance such as electric characteristics and mechanical characteristics such as a protective layer.

As the conductive carrier, any of those used in known electrophotographic photoreceptors can be used. Specific examples include metal drums and sheets of aluminum, copper, and the like, and laminates and vapor-deposits of these metal foils. Further, plastic films, plastic drums, paper, and the like, which are subjected to conductive treatment by applying a conductive substance such as metal powder, carbon black, copper iodide, and polymer electrolyte together with an appropriate binder, may be used. In addition, 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 the like.

In the above-described laminated photoreceptor, a charge generation layer is usually formed on a conductive support, and a charge transfer layer is formed thereon, but the reverse configuration may be adopted.

The charge generation layer is formed by applying and drying a coating solution containing the bisazo compound of the present invention and a binder polymer.

The bisazo compound may be dissolved, but is usually applied as a coating solution in a dispersed state. Chlorinated solvents such as butylamine and ethylenediamine; ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene and xylene; N, N Aprotic polar solvents such as dimethylformamide, acetonitrile, N-methylpyrrolidone and dimethylsulfoxide; alcohols such as methanol, ethanol and isopropanol; esters such as ethyl acetate, methyl formate, methyl cellosolve acetate; dichloroethane, chloroform and the like Chlorinated hydrocarbons and the like can be mentioned.

When dispersing the bisazo compound, it is necessary to make the particle diameter 1 μm 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 include cellulose ester, cellulose ether, epoxy resin, silicon resin and the like.

The ratio of the bisazo compound of the present invention and the binder polymer is not particularly limited, but generally, the bisazo compound
5 to 500 parts by weight, preferably 20 to 300 parts per 100 parts by weight
Parts by weight of binder polymer are used.

In addition to the above, a dispersion stabilizer, a coating property improving agent, and a dye, an electron-withdrawing compound, and other additives for improving performance may be added to the coating solution. The thickness of the charge generation layer is adjusted to 0.05 to 5 μm, preferably 0.1 to 2 μm.

One or more kinds of the charge carrier transfer medium are dissolved in the coating solution for the charge generation layer, and the film thickness after drying is 5 to 50.
When applied on a conductive support so as to have a thickness of 10 μm, preferably 10 to 30 μm, a single-layer type photoreceptor can be obtained. The ratio of the bisazo compound and the binder polymer and the charge carrier transfer medium is usually 10 to 1000 parts by weight, preferably 30 to 500 parts by weight of the binder polymer with respect to 10 parts by weight of the bisazo compound.
Parts by weight, the charge carrier transfer medium is from 5 to 1000 parts by weight, preferably from 20 to 500 parts by weight.

In the laminated photoreceptor, a charge transfer layer is formed by applying and drying a coating solution containing a charge carrier transfer medium on the charge generation layer. When the charge carrier transfer medium is a polymer compound having a film-forming property, a binder polymer may not be particularly used, but may be mixed for improving flexibility and the like.

In the case of a low molecular compound, a binder polymer is used for forming a film. As the binder polymer, those described above are used, and the amount of the binder polymer is usually 50 to 3000 parts by weight, preferably 70 to 100 parts by weight of the charge carrier transfer medium.
It is in the range of ~ 1000 parts by weight.

In addition to the above, various additives can be used in the charge transfer layer in order to improve the performance and 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 improvers, plasticizers, and crosslinking agents.

Examples of the electron-withdrawing compound include chloranil and 2,3-
Quinones such as dichloro-1,4-naphthoquinone, 2-methylanthraquinone, 1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone, 2-chloroanthraquinone and phenanthrenequinone; aldehydes such as 4-nitrobenzaldehyde; 9- Benzoylanthracene, indandione, 3,5-dinitrobenzophenone, 3,5 ′,
Ketones such as 5,5'-tetranitrobenzophenone; acid anhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride; tetracyanoethylene, terephthalalmalononitrile, 4-nitrobenzalmalonenitrile, 4-benzoyloxy Cyano compounds such as benzalmalononitrile and 4- (p-nitrobenzoyloxy) benzalmalononitrile; 3-benzalphthalide, 3- (α-cyano-p-nitrobenzal) phthalide, 3- (α-cyano-p-nitrobenzal And phthalides such as -4,5,6,7-tetrachlorophthalide.

<Effects of the Invention> The photoreceptor for electrophotography containing the bisazo compound of the present invention has high sensitivity and good color sensitivity, and particularly has low light fatigue. Laser printers and liquid crystal shutter printers, which are required not only for electrophotographic plain paper copiers but also for stable performance and reliability, as well as low fluctuations, high stability and extremely high durability. It is a photoconductor suitable for a photoconductor for a printer such as an LED printer.

<Examples> Next, the present invention will be described more specifically with reference 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 13.8 parts of 3-hydroxynaphthalic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) and 9.2 parts of 0-phenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved and stirred in a mixed solvent of 30 parts of acetic acid and 150 parts of nitrobenzene. The reaction was carried out for 2 hours at the acetic acid boiling point. After the reaction, the reaction solution was cooled to room temperature, and the precipitated crystals were washed with methanol and dried. The obtained crystals had a yellow hairy shape and did not dissolve below 320 ° C. Elemental analysis and measurement of infrared absorption spectrum revealed that the crystals were 2-hydroxy and 5-hydroxy-7H-benzimidazo [2,1-a] benz [de] isoquinolin-7-one. The yield was 17.8 parts, and the elemental analysis values were as follows.

C ₁₈ H ₁₀ O ₂ N ₂ Calculated: C 75.54%, H 3.53%, N 9.78% Observed: C 75.50%, H 3.49%, N 9.72% The 2-hydroxy or 5- Hydroxy-7H-benzimidazo [2,1-a] benzo [de] isoquinoline-7-
While stirring 1.7 parts with 500 parts of dimethyl sulfoxide at 20 ° C, Dimethylsulfoxide solution of tetrazonium borohydride was added dropwise. Then sodium acetate 2.
The coupling reaction was started by dropping a solution obtained by dissolving 4 parts in 24 parts of water. After completion of the dropwise addition, stirring was continued for 3 hours and the mixture was taken.

Next, the obtained bisazo compound was treated with water, methanol,
After washing with tetrahydrofuran, it was dried. The obtained solid was dark purple and did not melt below 320 ° C. Elemental analysis value and infrared absorption spectrum measurement (first
From the figure, this was identified as a mixture of the following bisazo compounds. The yield was 1.8 parts and the elemental analysis values were as follows.

Calcd _{C 55 H 28 O 6 N 8} : C73.66%, H3.15%, N12.49% Found: C73.21%, H3.03%, N12.28 % The bisazo compound of the present invention used in the following Examples was synthesized according to this Reference Example or a method similar thereto.

Examples 1 to 84 0.4 parts of a bisazo compound having a structure corresponding to the above general formula [I] is added to 4-methoxy-4-methyl-pentanone-
2 (Mitsubishi Kasei Co., Ltd.) and 30 parts were dispersed by a sand grinder, and polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., trade name: SREC BH-3), phenoxy resin (manufactured by Union Carbide Co., Ltd.) (DKHH) 0.2 parts each. The obtained dispersion liquid of the bisazo compound was applied on a 75 μm-thick polyester film deposited on an aluminum vapor-deposited layer with a wire bar so as to have a dry film thickness of 0.2 g / m ^2, and then dried. 90 parts of N-ethylcarbazole-3-aldehydediphenylhydrazone, 4-
2 parts of (p-nitrobenzoyloxy) benzalmalonitrile and polycarbonate resin (Mitsubishi Gas Chemical Co., Ltd.)
100 parts of dioxane 670
The solution dissolved in the portion was applied so as to have a dry film thickness of 13 μm to form a charge transfer layer. Thus, an electrophotographic photosensitive member having a two-layer photosensitive layer was obtained.

Table 1 shows the values of the half-life exposure amount (E _1/2 ) as the sensitivity of these photosensitive _members .

The half-exposure amount was measured for the photoreceptor using an electrostatic copying paper tester (Model SP-428 manufactured by Kawaguchi Electric Works). First, it was charged by a corona discharge of -6.5 kV in a dark place, and then exposed with white light having an illuminance of 5 lux, and an exposure amount necessary for the surface potential to attenuate to half of the initial surface potential was obtained.

The compounds of Nos. 57 to 74 in the table are a mixture of four isomers as in the reference example, and the compounds of Nos. 75 to 84 are compounds that give K ¹ and K ² couplers in the table. Is an equimolar reaction system.

[Brief description of the drawings]

FIG. 1 is an infrared absorption spectrum of the bisazo compound synthesized in Reference Example.

Claims (1)

(57) [Claims] 1. A conductive support having the following general formula [I] (Wherein, K ^1, K ² represents a coupler residue containing a hydroxyl group with a coupling capacity, K ^1, K ² may be the same or different, R ¹ represents a hydrogen atom, a lower alkyl group, a lower alkoxy A photosensitive group containing a bisazo compound represented by the following formula: