JP2654240B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a photoconductor for electrophotography. More specifically, the present invention relates to an electrophotographic photoconductor in which a photosensitive layer on a conductive support contains a specific azo compound as a charge generating substance.

[Conventional technology]

Conventionally, inorganic photosensitive materials such as selenium, cadmium sulfide, and zinc oxide have been widely used as photosensitive materials for electrophotographic photosensitive members. However, photoreceptors using these photosensitive materials have not sufficiently satisfied the required performance as an electrophotographic photoreceptor, such as sensitivity, light stability, moisture resistance, and durability. For example, a photoreceptor using a selenium-based material has excellent sensitivity, but is easily crystallized due to heat or adhesion of dirt, and the characteristics of the photoreceptor are easily deteriorated. In addition, it has many drawbacks, such as high cost because it is manufactured by vacuum evaporation, and difficulty in processing it into a belt shape due to lack of flexibility. A photoreceptor using a cadmium sulfide-based material has a problem in moisture resistance and durability, and a photoreceptor using zinc sulfide has a problem in durability.

In order to overcome the disadvantages of the photoreceptor using the inorganic photosensitive material, various photoreceptors using the organic photosensitive material have been studied.

For example, 2,4,
One using a combination of 7-trinitro-9-fluorenone and poly-N-vinylcarbazole is known. However, the photoreceptor using this had low sensitivity and was not satisfactory in durability.

In recent years, among photoconductors developed to improve the above-mentioned disadvantages, a function-separated type photoconductor in which a charge generation function and a charge transport function are shared by individual substances has been receiving attention. In this function-separated type photoreceptor, substances having respective functions can be selected from a wide range and combined, so that a photoreceptor having high sensitivity and high durability can be manufactured. Many substances have been proposed as charge generating substances for use in such a function-separated type photoreceptor.
Among them, a photoreceptor using an organic dye or an organic pigment as a charge generating substance has been receiving particular attention in recent years.

For example, a photoreceptor using a disazo pigment having a styrylstilbene skeleton (JP-A-53-133445), a photoreceptor using a disazo pigment having a carbazole skeleton (JP-A-53-95033), triphenylamine Photoreceptor using a trisazo pigment having a skeleton (JP-A-53-132347), photoreceptor using a disazo pigment having a distyrylcarbazole skeleton (JP-A-54-14967), and having a bisstilbene skeleton Photoreceptors using disazo pigments (JP-A-54-17733) have been reported. However, these electrophotographic photoconductors do not always fully satisfy the required performance, and development of a more excellent photoconductor has been desired.

[Problems to be solved by the invention]

An object of the present invention is to provide an electrophotographic photoreceptor having sufficient sensitivity and good durability.

[Means for solving the problem]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the general formula (I) (Wherein, Ar represents a substituted or unsubstituted hydrogenated aromatic ring or an aromatic heterocyclic ring which may be bonded via a bonding group,
A is (However, Ar ² and Ar ³ represent a substituted or unsubstituted O-phenylene group, X represents a direct bond, an oxygen atom, a sulfur atom or a carbonyl group), and n represents an integer of 2 to 4. The present inventors have found that the azo compound represented by the formula (1) gives an electrophotographic photoreceptor having excellent characteristics such as high sensitivity and high durability, and have accomplished the present invention.

In the general formula (I), Ar may be bonded via a bonding group, or represents a substituted or unsubstituted aromatic hydrocarbon ring or an aromatic heterocyclic ring. Examples of the aromatic hydrocarbon ring include benzene and naphthalene. , Anthracene, pyrene, phenanthrene, fluorene, anthraquinone, fluorenone,
Benzanthrone and the like and aromatic heterocycles include thiophene, dibenzothiophene, pyridine, carbazole, benzoxazole, benzothiazole and the like. When having a substituent, as the substituent,
Alkyl groups such as methyl group, ethyl group, propyl group, and butyl group, alkoxy groups such as methoxy group, aryl groups such as phenyl group and naphthyl group, substituted amino groups such as diethylamino group and diphenylamino group, fluorine atom, chlorine atom , A halogen atom such as a bromine atom, a hydroxyl group, a nitro group,
And a cyano group.

Further, the aromatic hydrocarbon ring and the aromatic heterocyclic ring may be bonded via a bonding group.
-O-, -S-, -CO-, -CH = CH-, -CH ₂ -, - NH-, And the like.

In the present invention, Ar that can be preferably used is specifically exemplified below.

When n = 2 X forms an aromatic ring such as fluorene, anthrone, xanthene, and thioxanthene together with the O-phenylene group bonded thereto. Examples of the substituent on the O-phenylene group of these aromatic rings include an alkyl group such as a methyl group, an ethyl group, a propyl group and a butyl group, an alkoxy group such as a methoxy group, an ethoxy group, a propoxy group and a butoxy group, and a fluorine atom. , A halogen atom such as a chlorine atom and a bromine atom, a halomethyl group such as a trifluoromethyl group, a dialkylamino group such as a dimethylamino group and a diethylamino group, an acylamino group such as an acetylamino group and a benzoylamino group, a carboxylic acid and its ester derivative Groups, amide-derived groups, nitro groups, cyano groups and the like.

Table 1 shows azo compounds that can be preferably used in the present invention. In the table, in Ar, (A-1)
To (A-13) represent the structures exemplified above.

The compound of the present invention can be produced using the following method.

An amine compound represented by the general formula (II) ArNH ₂ ) _n (II) (wherein Ar and n are the same as in the general formula (I)) is diazotized, and then the diazotized compound is used as it is. Or after isolation as a borofluoride, the compound of the general formula (III) (In the formula, A is the same as in the general formula (I).) It can be easily produced by coupling with a coupler compound represented by the following formula:

The electrophotographic photoreceptor of the present invention comprises at least one of the azo compounds represented by the general formula (I) as a charge generating substance in a photosensitive layer on a conductive support. A typical structure of such a photoreceptor is shown in FIG. 1 and FIG. FIG. 1 shows a photoreceptor in which a dispersion type photosensitive layer 4 in which a charge generating substance 2 and a charge transporting substance 3 are dispersed in a binder is provided on a conductive support 1, and is shown in FIG. The reason is that a laminated photosensitive layer 4 'comprising a charge generating layer 6 in which a charge generating substance is dispersed in a binder and a charge transporting layer 5 in which a charge transporting substance is dispersed in a binder is provided on the conductive support 1. It is a photoconductor. Other examples include those in which the charge generation layer and the charge transport layer are reversed, and those in which an intermediate layer is provided between the photosensitive layer and the conductive support.

In the photoreceptor of FIG. 2, the image-exposed light transmits through the charge transport layer, and the charge generating substance generates charges in the charge generating layer. The generated charges are injected into the charge transport layer,
The charge transport material transports.

The electrophotographic photoreceptor of the present invention comprises, in addition to the azo compound of the general formula (I), a conductive support, a binder, a charge transport material, and the like. There is no particular limitation as long as it has a function as a component.

That is, as the conductive support used in the photoreceptor of the present invention, aluminum, copper, a metal plate such as zinc,
A material obtained by vapor-depositing a conductive material such as aluminum or SnO _{2 on} a plastic sheet or a plastic film of polyester or the like, or paper, resin or the like subjected to conductive treatment is used.

As the binder, a vinyl polymer such as polystyrene, polyacrylamide, or poly-N-vinylcarbazole, or a condensation resin such as a polyamide resin, a polyester resin, an epoxy resin, a phenoxy resin, or a polycarbonate resin is used. Any resin having adhesiveness to the body can be used.

Charge transport materials are generally classified into two types, a hole transport material and an electron transport material, and both can be used in the photoreceptor of the present invention. Examples of the hole transport material include an electron-accepting material such as trinitrofluorenone or tetranitrofluorenone, which easily transports electrons, and poly-N
-A polymer containing a heterocyclic compound represented by vinylcarbazole, a triazole derivative, an oxadiazole derivative, an imidazole derivative, a pyrazoline derivative,
Electron-donating substances that easily transport holes such as polyarylalkane derivatives, phenylenediamine derivatives, hydrazone derivatives, amino-substituted chalcone derivatives, triarylamine derivatives, carbazole derivatives, stilbene derivatives, and the like can be given.

For example, 9-ethylcarbazol-3-aldehyde-1-methyl-1-phenylhydrazone, 9-ethylcarbazole-3-aldehyde-1-benzyl-1-phenylhydrazone, 9-ethylcarbazole-3-aldehyde-1, 1-diphenylhydrazone, 4-diethylaminostyrene-β-aldehyde-1-methyl-1-phenylhydrazone, 4-methoxynaphthalene-1-aldehyde-1-benzyl-1-phenylhydrazone, 4-methoxybenzaldehyde-1-methyl- 1-phenylhydrazone, 2,4-dimethoxybenzaldehyde-1-benzyl-1-phenylhydrazone, 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone, 4-methoxybenzaldehyde-1-benzyl-1- (4-methoxy) phenyl Hydrazo , 4-diphenylaminobenzaldehyde-1-benzyl-1-phenylhydrazone, 4-dibenzylaminobenzaldehyde-1,1-diphenylhydrazone, 1,1-bis (4-dibenzylaminophenyl) propane, tris (4-diethylamino) Phenyl) methane, 1,1-bis (4-dibenzylaminophenyl) propane, 2,2′-dimethyl-4,4′-bis (diethylamino) -triphenylmethane, 9- (4-diethylaminostyryl) anthracene, 9-bromo-10-
(4-diethylaminostyryl) anthracene, 9-
(4-dimethylaminobenzylidene) fluorene, 3-
(9-fluorenylidene) -9-ethylcarbazole,
1,2-bis (4-diethylaminostyryl) benzene,
1,2-bis (2,4-dimethylethoxystyryl) benzene, 3
-Styryl-9-ethylcarbazole, 3- (4-methoxystyryl) -9-ethylcarbazole, 4-diphenylaminostyrylben, 4-dibenzylaminostyrylben, 4-ditolylaminostyrylben, 1- (4-
Diphenylaminostyryl) naphthalene, 1- (4-diethylaminostyryl) naphthalene, 4'-diphenylamino-α-phenylstilbene, 4'-methylphenylamino-α-phenylstilbene, 1-phenyl-3
-(4-diethylaminostyryl) -5- (4-diethylaminophenyl) pyrazoline, 1-phenyl-3-
(4-Dimethylaminostyryl) -5- (4-dimethylaminophenyl) pyrazolin and the like.

Other hole transporting substances include, for example, 2,5-bis (4-diethylaminophenyl) -1,3,4-oxadiazole, 2,5-bis [4- (4-diethylaminostyryl) phenyl] -1,3,4-oxadiazole, 2-
(9-ethylcarbazol-3-yl) -5- (4-diethylaminophenyl) -1,3,4-oxadiazole,
2-vinyl-4- (2-chlorophenyl) -5- (4-
Diethylaminophenyl) oxazole, 2- (4-diethylaminophenyl) -4-phenyloxazole,
9- [3- (4-diethylaminophenyl) -2-propenylidene] -9H-xanthene, poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole,
Polyvinyl pyrene, polyvinyl anthracene, pyrene formaldehyde resin, ethyl carbazole formaldehyde resin and the like can be mentioned.

Examples of the charge transport material include chloranil, bromanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone,
4,5,7-tetranitro-9-fluorene, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2- b] Thiophene-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide and the like.

These charge transport materials are used alone or in combination of two or more.

An intermediate layer can be provided between the photosensitive layer and the conductive support, if necessary. As the material, polyamide, nitrocellulose, casein, polyvinyl alcohol, and the like are suitable, and the film thickness is preferably 1 μm or less.

A conventionally known method can be used for manufacturing the photoconductor. For example, in a laminated photoreceptor, fine particles of an azo compound are dispersed in a solution in which a binder is dissolved, coated on a conductive support, and dried to obtain a charge generation layer. Then, the charge transport material and the binder are dissolved. Apply the solution,
By drying, a charge transport layer can be prepared. Other methods can be used to form the charge generation layer. For example, there is a method of vacuum-depositing an azo compound, or a method of applying and drying a solution of an azo compound. The former uses a high cost, and the latter uses an organic amine which is generally inconvenient to handle, such as ethylenediamine, n-butylamine, and the like. Since there is a drawback in production, a coating method of a fine particle dispersion of an azo compound is preferable. The coating method is performed by usual means, for example, doctor blade, dipping, wire bar and the like. The optimum range of the thickness of the photosensitive layer differs depending on the type of the photoconductor. For example, in the case of the photoreceptor as shown in FIG. 1, it is preferably 3 to 50 μm, more preferably 5 to 30 μm.
m.

In the photoreceptor as shown in FIG. 2, the thickness of the charge generation layer 6 is preferably 0.01 to 5 μm, more preferably
It is 0.05-2 μm. If the thickness is less than 0.01 μm, the generation of electric charge is not sufficient, and if it exceeds 5 μm, the residual potential is high, which is not practically preferable. The thickness of the charge transport layer 5 is preferably 3 to 50 μm, more preferably 5 to 30 μm.
When the thickness is less than 3 μm, the charge amount is insufficient, and when the thickness exceeds 50 μm, the residual potential is high and is not practically preferable.

The content of the azo compound represented by the general formula (I) in the photosensitive layer varies depending on the type of the photoreceptor, but in the case of the photoreceptor shown in FIG. Or less, more preferably 20% by weight or less. Further, this layer contains a charge transporting substance preferably in an amount of 10 to 95% by weight, more preferably 30 to 90% by weight. In the photoreceptor as shown in FIG. 2, the ratio of the azo compound in the charge generation layer 6 is preferably 30% by weight or more, more preferably 50% or more.
% By weight or more. In the charge transport step 5, the charge transport substance is contained in an amount of 10 to 95% by weight, preferably 30 to 90% by weight. If the amount of the charge transporting substance in this layer is less than 10% by weight, the charge is hardly transported, and if it exceeds 95% by weight, the mechanical strength of the photoconductor is poor, which is not practically preferable.

[Action and effect]

The electrophotographic photoreceptor of the present invention can be easily manufactured by using the azo compound represented by the general formula (I) as a charge generating material, and has excellent performance with high sensitivity and without deterioration in performance with repeated use. Have.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to Examples, but the embodiments of the present invention are not limited thereto.

Production Example 1 Synthesis of Exemplified Compound No. 4 4.5 g of 2-hydroxy-3-formylnaphthalene, 4.7 g of fluorene and 2.2 g of 96% potassium hydroxide were charged into 20 ml of N, N-dimethylformamide and stirred at 130 ° C. for 2 hours. . Cooled to room temperature and drained into 100 ml of water. The resulting tar-like component was dissolved in 100 ml of benzene, and purified and separated by column chromatography (silica gel-benzene).
-A pale yellow structural formula recrystallized from hexane 4.2 g of a coupler compound represented by the formula (melting point: 150.5 to 151.5
° C).

2.0 g of the compound was dissolved in 100 ml of N, N-dimethylformamide to give a coupler solution.

2,7-Diaminofluorenone (1.4 g) was suspended in 35% hydrochloric acid (3.5 ml) and water (45 ml), kept at 60 ° C. for 30 minutes, and added dropwise with a solution of 1.4 g of sodium nitrite in 6 ml of water at 0 ° C. 0
After stirring at 1 ° C. for 1 hour, insolubles were removed and 15 ml of 42% borofluoric acid was added. The precipitated crystals are filtered and dried,
2.4 g of diazonium borofluoride was obtained.

1.1 g of diazonium borofluoride in the coupler liquid
The mixture was added at 10 ° C. or lower and stirred for 5 minutes. 0.9 g of sodium acetate
Is dissolved in 10 ml of water at 10 ° C. or lower.
After stirring for an hour, the mixture was returned to room temperature and further stirred for 3 hours.
The deposited precipitate was filtered off, and N, N-dimethylformamide 100
The precipitate was suspended in 2 ml and filtered. This suspension operation was repeated twice more, followed by washing and drying to obtain 2.3 g of a black powder (melting point of 270 ° C. or higher).

This was confirmed to be Exemplified Compound No. 4 from the elemental analysis values and the infrared absorption spectrum.

Elemental analysis value CHN Calculated value (%) 83.94 4.13 6.42 Actual value (%) 83.80 4.01 6.45 The infrared absorption spectrum (KBr method) is shown in FIG.

Production Example 2 Synthesis of Exemplified Compound No. 6 4.5 g of 2-hydroxy-3-formylnaphthalene, 2,7
6.7 g of dinitrofluorene and 0.7 ml of piperidine in N, N
-30 ml of dimethylformamide was added, stirred at 120 ° C for 3 hours, and allowed to cool to room temperature. The precipitated crystals were separated by filtration and recrystallized from a small amount of N, N-dimethylformamide to give a brown structural formula 5.4 g (melting point: 270 ° C. or more) of a coupler compound represented by the formula: was obtained.

32 g of the compound was dissolved in 500 ml of N, N-dimethylformamide to prepare a coupler solution.

Diazonium borofluoride synthesized in Production Example 1
1.3 g was added to the coupler solution at 10 to 15 ° C. and dissolved.
A solution in which 1.0 g of sodium acetate was dissolved in 20 ml of water was added dropwise at the same temperature, and the mixture was stirred for 4 hours. The deposited precipitate was filtered off, and N, N
-The precipitate was suspended in 200 ml of dimethylformamide for 2 hours and then filtered. This suspension and filtration operation was further repeated three times, followed by washing with water and drying to obtain 3.0 g of a black powder (melting point: 27
0 ° C. or higher).

The obtained compound was confirmed to be Exemplified Compound No. 6 by elemental analysis and infrared absorption spectrum.

Elemental analysis value CHN Calculated value (%) 69.58 3.04 10.65 Actual value (%) 69.42 3.00 10.51 The infrared absorption spectrum (KBr method) is shown in FIG.

Example 1 0.5 part of a polyester resin (trade name “Vylon 200” manufactured by Toyobo), 0.5 part of Exemplified Compound No. 6 and 50 parts of tetrahydrofuran were pulverized and mixed by a ball mill, and the obtained dispersion was applied to an aluminum plate using a wire bar. And apply at 80 ° C for 20
After drying for about one minute, a charge generation layer of about 1 μm was formed. On this charge generation layer, the following structural formula A solution obtained by dissolving 1 part of a hydrazone compound represented by the following formula and 1 part of a polycarbonate resin (trade name “Panlite K-1300” manufactured by Teijin Chemicals) in 10 parts of chloroform is applied using a wire bar, and dried at 80 ° C. for 30 minutes. Then, a charge transporting layer having a thickness of about 18 μm was formed to produce the laminated photoreceptor shown in FIG.

Electrostatic copying paper tester (model manufactured by Kawaguchi Electric Works, Ltd.)
EPA-8100) was charged by corona discharge of the applied voltage -6KV the photoconductor was measured using a surface potential V ₀ at that time, it was left at the next two seconds dark, measuring the surface potential V ₂ at that time , followed by the surface illuminance of the photoreceptor was measured halogen lamp time surface potential is irradiated with light from (color temperature 2856 ° K) is 1/2 of V ₂ in a state where the 51Ux, half decay exposure E1 / 2 (lux
Sec) was calculated. Surface potential V ₁₂ after 10 seconds of light irradiation,
That is, the residual potential was measured.

Examples 2 to 20 A photoconductor was prepared in the same manner as in Example 1, except that the compound of the present invention was used as a charge generating substance, and the compound represented by the following structural formula was used as a charge transporting substance. , E1
/ 2 was asked. The charge generating substance, charge transporting substance and E1 / 2 used are shown in Table 2 together with Example 1.

Comparative Example 1 The following structural formula described in JP-B-55-42380 Example 1 except that the disazo compound represented by the formula (1) was used as a charge generating material and (CT-4) was used as a charge transporting material.
A photoreceptor was prepared in the same manner as described above.

 E1 / 2 was 12.0 (lux · sec).

Example 21 The photoreceptor prepared in Example 1 was mounted on a commercially available electrophotographic copying machine and copied. As a result, even on the 10,000th copy, a clear image without fogging which was faithful to the original was obtained.

As described above, it can be said that the electrophotographic photoreceptor using the azo compound of the present invention has high sensitivity, stable performance for repeated use, and excellent durability.

The photoreceptor of the present invention can be used not only in electrophotographic copying machines, but also in various linters and electrophotographic plate making systems that apply the principle of electrophotographic copying.

[Brief description of the drawings]

1 and 2 are cross-sectional views showing an example of the configuration of an electrophotographic photosensitive member. In FIG. 1 and FIG. 2, reference numerals are as follows. DESCRIPTION OF SYMBOLS 1 ... Conductive support, 4,4 '... Photosensitive layer 2 ... Charge generating material, 5 ... Charge transport layer 3 ... Charge transport material, 6 ... Charge generating layer FIGS. FIG. 3 is a diagram showing infrared absorption spectra (KBr method) of Exemplified Compounds No. 4 and No. 6, respectively.

Claims (1)

(57) [Claims] 1. A photosensitive layer on a conductive support, wherein the photosensitive layer has the general formula (I) (Wherein, Ar represents a substituted or unsubstituted aromatic hydrocarbon ring or aromatic heterocyclic ring which may be bonded via a bonding group, and A is (However, Ar ² and Ar ³ represent a substituted or unsubstituted O-phenylene group, X represents a direct bond, an oxygen atom, a sulfur atom or a carbonyl group), and n represents an integer of 2 to 4. A photoconductor for electrophotography, comprising at least one azo compound represented by the formula: