JPH026050B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor. Conventionally, as electrophotographic photoreceptors, inorganic photoreceptors having a photosensitive layer mainly composed of an inorganic photoconductive substance such as selenium, zinc oxide, or cadmium sulfide have been widely used. However, these do not necessarily satisfy the characteristics required for an electrophotographic photoreceptor, such as sensitivity, thermal stability, moisture resistance, and durability. For example, selenium crystallizes due to heat, the adhesion of dirt such as fingerprints, etc., and therefore its properties as an electrophotographic photoreceptor tend to deteriorate. Further, when cadmium sulfide is used, there are problems in moisture resistance and durability, and when zinc oxide is used, there are problems in durability.Furthermore, selenium and cadmium sulfide have significant restrictions in manufacturing and handling due to their toxicity. In order to overcome the above-mentioned drawbacks of inorganic photoreceptors, active research and development has been conducted in recent years on the use of various organic photoconductive substances as materials for the photosensitive layer of electrophotographic photoreceptors. For example, in Japanese Patent Publication No. 50-10496, poly-N
An organic photoreceptor having a photosensitive layer comprising -vinylcarbazole and 2,4,7-trinitro-9-fluorenone is described. However, this photoreceptor is not necessarily satisfactory in sensitivity and durability. In order to further improve these drawbacks, attempts have been made to develop organic photoreceptors with high sensitivity and durability by assigning the carrier generation function and carrier transport function to different substances in the photosensitive layer. ing. In such so-called function-separated type electrophotographic photoreceptors, it is possible to select substances that exhibit each function from a wide range, so it is relatively easy to create an electrophotographic photoreceptor with arbitrary characteristics. It is possible to create one. Many substances have been proposed as carrier generating substances that are effective for such functionally separated electrophotographic photoreceptors. An example of using an inorganic substance is amorphous selenium, as described in Japanese Patent Publication No. 43-16198. Although this is combined with an organic carrier transport substance, the carrier generation layer made of amorphous selenium has the disadvantage that it crystallizes due to heat or the like and its properties deteriorate, as described above. In addition, many electrophotographic photoreceptors using organic dyes or organic pigments as carrier generating substances have been proposed. Akira
It is already known from JP-A-55-22834, JP-A-54-79632, JP-A-56-116040, etc.
However, electrophotographic photoreceptors using these bisazo compounds are not necessarily satisfactory in terms of sensitivity, residual potential, or even stability during repeated use, and the range of selection of materials to be used as carrier transport materials is limited. However, the electrophotographic photoreceptor does not fully satisfy the wide range of demands in the electrophotographic process that electrophotographic photoreceptors undergo. An object of the present invention is to provide an electrophotographic photoreceptor having a photosensitive layer containing a characteristic bisazo compound, being stable against heat and light, and having high carrier generation efficiency and excellent photoconductivity. be. Another object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity, low residual potential, and excellent durability that can stably exhibit these good characteristics over a long period of time even after repeated use. There is something to do. Still another object of the present invention is to contain a carrier generating substance comprising a specific bisazo compound that exhibits excellent carrier generating function in combination with any carrier transporting substance arbitrarily selected from a wide range. An object of the present invention is to provide an electrophotographic photoreceptor having a photosensitive layer consisting of the following and having excellent characteristics. As a result of extensive research to achieve the above object, the present inventors discovered that the bisazo compound represented by the following general formula [] has excellent photoconductivity, particularly excellent carrier generation ability, and the present invention It is a completed invention. General formula [] (In the formula, A is

【formula】

【formula】

[expression] or

[Formula], Z: atomic group necessary to constitute substituted/unsubstituted aromatic carbocycle or substituted/unsubstituted aromatic heterocycle Y: hydrogen atom, hydroxy group, carboxy group, or ester group thereof; Sulfo group, substituted/unsubstituted carbamoyl group, or substituted/unsubstituted sulfamoyl group R ₁ : Hydrogen atom, substituted/unsubstituted alkyl group, substituted/unsubstituted amino group, substituted/unsubstituted carbamoyl group, carboxy group or its ester group or cyano group Ar: substituted/unsubstituted aryl group R ₂ : represents a substituted/unsubstituted alkyl group, substituted/unsubstituted aralkyl group, or substituted/unsubstituted aryl group. That is, in the present invention, an electrophotographic photoreceptor is constructed by providing a photosensitive layer containing a bisazo compound represented by the above general formula [] on a conductive support. According to the present invention, as is clear from the description of the examples described below, it is stable against heat and light, and has excellent electrophotographic properties such as charge retention, sensitivity, and residual potential. It is possible to provide an electrophotographic photoreceptor that exhibits less fatigue change and is highly durable during use. In particular, in the present invention, the bisazo compound represented by the above general formula [] has an excellent carrier generation ability, and this is combined with a carrier transport substance to form the photosensitive layer into a so-called functionally separated structure. ,
An electrophotographic photoreceptor with even better characteristics can be obtained. Specific examples of the bisazo compound represented by the above general formula [] that are effective in the present invention include those represented by the following structural formula; It is not limited. The above bisazo compounds can be synthesized, for example, by the method shown in the following synthesis example. Synthesis Example (Synthesis of Exemplary Compound (-1)) 2,7-dinitro-9-fluorenone and malonic acid nitrile were synthesized by a known method (for example, J.Org.
Chem., Vol. 30, p. 644 (published in 1965)) When 2,7-dinitro-9-dicyanomethylidenefluorene is reduced with tin and hydrochloric acid, 2,7-diamino-
9-dicyanomethylidenefluorene dihydrochloride is obtained. 3.31g (0.01mol) of it in 100ml of hydrochloric acid
This dispersion was heated to a temperature of 5°C while stirring.
Cool to 20ml and add 1.4g of sodium nitrite to it.
An aqueous solution dissolved in water was added dropwise. After the dropwise addition, stirring was continued under cooling for an additional hour, and then filtration was performed. 10 g of ammonium hexafluorophosphate was added to the resulting filtrate, the resulting crystals were collected by filtration, and tetrazonium hexafluorophosphate was added. Got eight. These crystals were dissolved in 200 ml of N,N-dimethylformamide to obtain a dropwise solution for the next coupling reaction. 5.27 g (0.02 mol) of 2-hydroxy-3-naphthoic acid anilide (naphthol AS) was dissolved in 200 ml of N,N-dimethylformamide, 5.5 g of triethanolamine was added thereto, and the solution was cooled to a temperature of 5°C. The above-mentioned dropping liquid was added dropwise to the mixture while stirring vigorously. After the dropwise addition was completed, the mixture was stirred under cooling for 1 hour, and further stirred at room temperature for 2 hours, and the resulting crystals were collected by filtration. The crystals were washed twice with 1 part of N,N-dimethylformamide.
After washing twice with acetone and drying, 6.70 g (yield: 83.0%) of a blue compound was obtained. This blue compound was targeted because absorption due to the C=O bond of the amide was observed at ν = 1680 cm ^-1 in its infrared absorption spectrum, and the actual measured values of elemental analysis showed high consistency. It was confirmed to be Exemplified Compound (-1). Elemental analysis results (Chemical formula is C ₅₀ H ₃₀ N ₈ O _4. ) Element C H N Actual value (%) 74.61 3.70 13.67 Theoretical value (%) 74.43 3.74 13.89 By the bisazo compound represented by the above general formula [] In order to constitute the photosensitive layer of the electrophotographic photoreceptor of the present invention, a layer in which the bisazo compound is dispersed in a binder may be provided on a conductive support. Alternatively, the bisazo compound may be used as a carrier generating substance and combined with a carrier transporting substance having a carrier transporting ability to provide a so-called functionally separated photosensitive layer of laminated or dispersed type. In the composition of the photosensitive layer, not only one type of bisazo compound represented by the above general formula [] but also a combination of two or more types can be used, and it can also be used in combination with other bisazo compounds and other carrier generating substances. In the case where the electrophotographic photoreceptor of the present invention is of a functionally separated type, the mechanical structure may be any of the conventionally known structures. Usually, the configuration is as shown in FIGS. 1 to 6. The ones in FIGS. 1 and 3 are made of a laminate of a carrier generating layer 2 containing the above-mentioned bisazo compound as a main component and a carrier transport layer 3 containing a carrier transport substance as a main component on a conductive support 1. Structure provided with a photosensitive layer 4 consisting of FIGS. 2 and 4
The figure shows an intermediate layer 5 between the conductive support 1 and the photosensitive layer 4 in the configurations shown in FIGS. 1 and 3, respectively.
It has a configuration in which . In this way, the photosensitive layer 4
The best electrophotographic properties can be obtained when the material has a two-layer structure. In the case shown in FIG. 5, a photosensitive layer 4 comprising a carrier generating substance 7 made of the above-mentioned bisazo compound dispersed in a layer 6 containing a carrier transporting substance as a main component is provided directly on a conductive support 1. The structure shown in FIG. 6 is a structure in which a photosensitive layer 4 similar to that shown in FIG. 5 is provided on a conductive support 1 with an intermediate layer 5 interposed therebetween. The carrier transport substance may be an electron-transporting electron-accepting substance such as trinitrofluorenone or tetranitrofluorenone, or a heavy compound having a heterocyclic compound in its side chain, such as poly-N-vinylcarbazole. Hole-transporting electron-donating substances such as triazole derivatives, oxadiazole derivatives, imidazole derivatives, pyrazoline derivatives, polyarylalkane derivatives, phenylenediamine derivatives, hydrazone derivatives, amino-substituted chalcone derivatives, carbazole derivatives, and stilbene derivatives. can be mentioned.
A preferable carrier transport material is disclosed in Japanese Patent Application Laid-Open No. 1986-
Pyrazoline compounds described in Publication No. 105537, Japanese Patent Publication No. 55-42380, Japanese Patent Publication No. 150128-1980,
Examples include hydrazone compounds described in JP-A-55-52064, but the carrier transport material used in the present invention is not limited to these. In the case of forming a photosensitive layer having a two-layer structure, the carrier generation layer 2 can be provided by the following method. (a) A method of applying a solution prepared by dissolving the above-mentioned bisazo compound in an appropriate solvent, or a solution prepared by adding a binder to the solution and dissolving the mixture. (b) The bisazo compound described above is made into fine particles in a dispersion medium using a ball mill, a homomixer, etc.
A method of applying a dispersion obtained by mixing and dispersing by adding a binder if necessary. The solvent or dispersion medium used for forming the carrier generation layer includes n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N,N-dimethylformamide, acetone,
Methyl ethyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, 1,2
- Dichloroethane, dichloromethane, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide and the like. When a binder is used to form a carrier generation layer or a carrier transport layer, any binder can be used, but in particular, it can be used to form an electrically insulating film that is hydrophobic and has a high dielectric constant. High molecular weight polymers are preferred. As such a polymer,
Examples include, but are not limited to, the following: (a) Polycarbonate (b) Polyester (c) Methacrylic resin (d) Acrylic resin (e) Polyvinyl chloride (f) Polyvinylidene chloride (g) Polystyrene (h) Polyvinyl acetate (i) Styrene-butadiene copolymer (j ) Vinylidene chloride-acrylonitrile copolymer (k) Vinyl chloride-vinyl acetate copolymer (l) Vinyl chloride-vinyl acetate-maleic anhydride copolymer (m) Silicone resin (n) Silicone-alkyd resin (o) Phenol -Formaldehyde resin (p) Styrene-alkyd resin (q) Poly-N-vinylcarbazole These binders can be used alone or in a mixture of two or more. The thickness of the carrier generation layer 2 thus formed is preferably 0.01 to 20 μm, more preferably 0.05 to 5 μm. Further, when the above-mentioned bisazo compound is dispersed to form a photosensitive layer or a carrier generation layer, it is preferable that the bisazo compound is in the form of powder having a particle size of 5 μm or less, preferably 1 μm or less. The conductive support in the present invention includes a metal plate, a metal drum, a conductive polymer, a conductive compound such as indium oxide, or aluminum,
A conductive thin layer made of metals such as palladium and gold,
Those that are provided on a substrate such as paper or plastic film by means of coating, vapor deposition, lamination, etc. are used. As the intermediate layer which functions as an adhesive layer or a barrier layer, a material made of a polymer as described above as a binder, an organic polymer substance such as polyvinyl alcohol, ethyl cellulose, or carboxymethyl cellulose, or aluminum oxide is used. . The electrophotographic photoreceptor of the present invention has the above-described structure, and has excellent charging characteristics, sensitivity characteristics, and image forming characteristics, is stable against heat and light, and has little fatigue deterioration even when used repeatedly. It has excellent durability. Examples of the present invention will be described below, but the embodiments of the present invention are not limited thereby. Example 1 A layer of vinyl chloride-vinyl acetate-maleic anhydride copolymer "Eslec MF-10" (manufactured by Sekisui Chemical Co., Ltd.) was placed on a conductive support made of polyester film laminated with aluminum foil.
Exemplary compound (-1) forms an intermediate layer of 0.05 μm.
2g of polycarbonate resin “Panlite L-
1250 (manufactured by Teijin Kasei) in 100 ml of 1,2-dichloroethane and dispersed in a ball mill for 12 hours. A dispersion obtained by dispersing the mixture was applied onto the intermediate layer so that the film thickness after drying was 0.5 μm. A carrier generating layer is formed by drying, and a carrier transport material 3-
A solution of 6 g of (p-methoxystyryl)-9-(p-methoxyphenyl)carbazole and 10 g of polycarbonate resin "Panlite L-1250" dissolved in 100 ml of 1,2-dichloroethane has a film thickness of 12 μm after drying. A carrier transport layer was formed by coating and drying to produce an electrophotographic photoreceptor of the present invention. The electrophotographic photoreceptor thus obtained was mounted on an electrostatic paper tester "SP-428 model" (manufactured by Kawaguchi Electric Seisakusho).
The following characteristic tests were conducted. In other words, to the charger -
After applying a voltage of 6 kV and charging the photosensitive layer by corona discharge for 5 seconds, the photosensitive layer was left to stand for 5 seconds, and then the photosensitive layer was irradiated with light from a halogen lamp with an illuminance of 35 lux on the surface of the photosensitive layer. The exposure amount required to attenuate the surface potential to 1/2, that is, the half-reduction exposure amount E _1/2 was determined. In addition, the surface potential, that is, the residual potential V _R after exposure with an exposure amount of 30 lux·sec was determined. Furthermore, similar measurements were repeated 100 times. The results are shown in Table 1.

[Table] Comparative Example 1 A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 1, except that a bisazo compound represented by the following structural formula was used as a carrier generating substance, and the same characteristic tests were conducted. . The results are shown in Table 2.

[Table] Examples 2 to 4 Exemplary compounds (
A total of three types of electrophotographic photoreceptors of the present invention were prepared in the same manner as in Example 1 except that -2), (-3), and (-7) were used, and the same characteristic tests were conducted on each of them. Ta. The results are shown in Table 3.

[Table] Example 5 Thickness of vinyl chloride-vinyl acetate-maleic anhydride copolymer "Eslec MF-10" (manufactured by Sekisui Chemical Co., Ltd.) on a conductive support made of polyester film laminated with aluminum foil
Exemplary compound (-25) forms an intermediate layer of 0.05 μm
Add 2 g of 1,2-dichloroethane to 110 ml of 1,2-dichloroethane and disperse in a ball mill for 24 hours. Apply the resulting dispersion onto the intermediate layer so that the film thickness after drying is 0.5 μm and dry to form a carrier generation layer. Then, a solution prepared by dissolving 6 g of the carrier transport substance tri-p-tolylamine in 70 ml of 1,2-dichloroethane along with 10 g of the methacrylic resin "Acrypet" (manufactured by Mitsubishi Rayon Co., Ltd.) was applied and dried so that the film thickness after drying was 10 μm. A carrier transport layer was formed, and an electrophotographic photoreceptor of the present invention was produced. When a characteristic test similar to that in Example 1 was conducted on this electrophotographic photoreceptor, in the first test,
E _1/2 = 3.0 lux·sec, V _R = -5V. Example 6 A 1% ethylenediamine solution of exemplified compound (-4) was placed on the intermediate layer of a conductive support provided with an intermediate layer similar to that used in Example 2 so that the thickness after drying was 0.3 μm. A carrier generation layer was formed by coating and drying. Furthermore, 1-phenyl-3-
6 g of (p-diethylaminostyryl)-5-(p-diethylaminophenyl) pyrazoline was dissolved in 70 ml of 1,2-dichloroethane along with 10 g of polyester resin "Vylon 200" (manufactured by Toyobo Co., Ltd.), and this solution was added to the membrane after drying. A carrier transport layer was formed by coating and drying to a thickness of 12 μm, thereby producing an electrophotographic photoreceptor of the present invention. Characteristic tests similar to those in Example 1 were conducted on this electrophotographic photoreceptor. The results are shown in Table 4. Comparative Example 2 A comparative electrophotographic photoreceptor was prepared in the same manner as in Example 6, except that a bisazo compound represented by the following structural formula was used as a carrier generating substance, and the same characteristic tests were conducted. The results are shown in Table 4.

[Table] Example 7 Exemplary compounds (-
A carrier generating layer was formed in the same manner as in Example 5 except that exemplified compound (-39) was used instead of 1,1-bis(p-N,N-dibenzylaminophenyl). ) 6g of butane with 10g of polycarbonate resin "Panlite L-1250" 1,2
- A carrier transport layer was formed by applying and drying a solution dissolved in 70 ml of dichloroethane so that the film thickness after drying was 10 μm, thereby producing an electrophotographic photoreceptor of the present invention. When the same characteristic test as in Example 1 was conducted on this electrophotographic photoreceptor, it was found that E _1/2 = 3.0 lux.sec, V _R
= 0V. Example 8 A 0.05 μm thick intermediate layer made of vinyl chloride-vinyl acetate-maleic anhydride copolymer “Eslec MF-10” (manufactured by Sekisui Chemical Co., Ltd.) was formed on the surface of an aluminum drum with a diameter of 100 mm. Then, a dispersion obtained by adding 4 g of Exemplified Compound (-5) to 400 ml of 1,2-dichloroethane and dispersing it in a ball mill for 24 hours was applied onto the intermediate layer so that the film thickness after drying was 0.6 μm. It was dried to form a carrier generation layer. On this carrier generation layer, the structural formula 30 g of the carrier transport substance N,N-diethylaminobenzaldehyde-1,1-diphenylhydrazone shown in 1.
A solution dissolved in 400 ml of 2-dichloroethane was coated and dried so that the film thickness after drying was 13 μm to form a carrier transport layer, thereby producing a drum-type electrophotographic photoreceptor according to the present invention. This electrophotographic photoreceptor was used in an electrophotographic copying machine "U-
When attached to a modified BixV2 (manufactured by Konishiroku Photo Industry Co., Ltd.) and used to create a copy, a high-contrast copy that was faithful to the original and clear was obtained. Although the copying was repeated 2000 times, the same copy image as the first copy was obtained until the end. Comparative Example 3 A drum-type electrophotographic photoreceptor for comparison was produced in the same manner as in Example 8, except that a bisazo compound represented by the following structural formula was used as a carrier generating substance. When a copying test similar to that in Example 8 was carried out using this electrophotographic photoreceptor, the obtained copied image had a low image density and a lot of fog. Further, when copying was repeated 2000 times, the contrast of the copied image gradually decreased, and in the end, almost no image was formed. Example 9 Vinyl chloride was deposited on a conductive support made of polyester film laminated with aluminum foil.
Made of vinyl acetate-maleic anhydride copolymer "Eslec MF-10" (manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 0.05μ.
Form an intermediate layer of m, and 5 of exemplary compound (-11)
g and polycarbonate resin “Panlite L-
1250 (manufactured by Teijin Kasei) in 100 ml of 1,2-dichloroethane and dispersed in a ball mill for 24 hours. A dispersion obtained by dispersing the mixture was applied onto the intermediate layer so that the film thickness after drying was 10 μm. This was dried to produce an electrophotographic photoreceptor of the present invention. When this electrophotographic photoreceptor was subjected to the same characteristic test as in Example 1 except that the voltage applied to the charger was +6 kV, E _1/2 = 4.0 lux. seconds, V _R = +
It was 15V. Example 10 Carrier transport material 1 was deposited on a conductive support consisting of a polyester film deposited with aluminum.
-Phenyl-3-(p-diethylaminostyryl)
-6 g of 5-(p-diethylaminophenyl)pyrazoline and 10 g of polyester resin "Pylon 200"
A carrier transport layer was formed by coating and drying a solution dissolved in 70 ml of 1,2-dichloroethane so that the film thickness after drying was 10 μm, and further, on this carrier transport layer, exemplified compound (-3) was added. 1 g and 1 g of the same (-7) as 1,2-dichloroethane 110
ml and dispersed in a ball mill for 24 hours, the dispersion was applied and dried to a film thickness of 0.5 μm after drying to form a carrier generation layer, thereby producing an electrophotographic photoreceptor of the present invention. When this electrophotographic photoreceptor was subjected to characteristic tests in the same manner as in Example 9, E _1/2 = 3.6 lux.
sec, V _R = +5V. As is clear from the above results, the electrophotographic photoreceptor of the present invention is excellent in characteristics such as sensitivity and residual potential, as well as in durability and stability in repeated use.

[Brief explanation of drawings]

1 to 6 are cross-sectional views showing examples of the mechanical structure of the electrophotographic photoreceptor of the present invention. 1... Conductive support, 2... Carrier generation layer,
3...Carrier transport layer, 4...Photosensitive layer, 5...Intermediate layer, 6...Carrier transport substance-containing layer, 7...Carrier generating substance.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing a bisazo compound represented by the following general formula [] on a conductive support. General formula [] (In the formula, A is [Formula] [Formula] [Formula] or [Formula], Z: an atom necessary to constitute a substituted/unsubstituted aromatic carbocycle or a substituted/unsubstituted aromatic heterocycle Group Y: Hydrogen atom, hydroxy group, carboxy group or its ester group, sulfo group, substituted/unsubstituted carbamoyl group, or substituted/unsubstituted sulfamoyl group R ₁ : Hydrogen atom, substituted/unsubstituted alkyl group, substituted/unsubstituted sulfamoyl group Unsubstituted amino group, substituted/unsubstituted carbamoyl group, carboxy group or its ester group, or cyano group Ar: Substituted/unsubstituted aryl group R ₂ : Substituted/unsubstituted alkyl group, substituted/unsubstituted aralkyl group or a substituted/unsubstituted aryl group.) 2. Claim 1, wherein the photosensitive layer contains a carrier transporting substance and a carrier generating substance, and the carrier generating substance contains the bisazo compound.
The electrophotographic photoreceptor described in .