JPH0314343B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a photoreceptor, and more particularly to a novel electrophotographic photoreceptor having a photosensitive layer containing an azo compound. (Prior Art) Conventionally, inorganic photoreceptors having a photosensitive layer mainly composed of an inorganic photoconductive compound such as selenium, zinc oxide, or cadmium sulfide have been widely used as photoreceptors. However, these are sensitive, thermally stable, moisture resistant,
Durability etc. are not necessarily satisfactory. For example, when selenium crystallizes, its properties as a photoreceptor deteriorate, making it difficult to manufacture.
Moreover, heat, fingerprints, etc. cause crystallization, which deteriorates the performance as a photoreceptor. In addition, cadmium sulfide has problems with moisture resistance and durability, and zinc oxide has problems with durability, etc. In order to overcome the drawbacks of these inorganic photoreceptors, research and development have been actively conducted in recent years on organic photoreceptors having photosensitive layers containing various organic conductive compounds as main components. For example, in JP-A-50-10496, poly-N-vinylcarbazole and 2,4,7-
There is a description of an organic photoreceptor having a photosensitive layer containing trinitro-9-fluorenone. However, this photoreceptor is not necessarily satisfactory in sensitivity and durability. In order to improve these drawbacks, attempts have been made to develop organic photoreceptors with higher performance by assigning the carrier generation function and the carrier transport function to different substances. Many studies have been conducted on such so-called functionally separated electrophotographic photoreceptors because each material can be selected from a wide range and a photoreceptor with arbitrary performance can be produced relatively easily. Ta. Many compounds have been proposed as carrier generating substances for such functionally separated electrophotographic photoreceptors. As an example of using an inorganic compound as a carrier generating substance, for example,
-There is amorphous selenium described in Publication No. 16198,
Although this is used in combination with an organic photoelectric compound, the drawback that the carrier generation layer made of amorphous selenium crystallizes due to heat and deteriorates the characteristics as a photoreceptor has not been improved. Furthermore, many electrophotographic photoreceptors using organic dyes or organic pigments as carrier generating substances have been proposed. For example, JP-A-54-12742 and JP-A-53-95033 are already known as electrophotographic photoreceptors containing bisazo compounds or trisazo compounds in their photosensitive layers. However, these bisazo compounds or trisazo compounds do not sufficiently satisfy the wide range of requirements of electrophotographic processes, such as sensitivity and residual potential. Furthermore, in recent years, Ar lasers and He lasers have been used as light sources for photoreceptors.
-Gas lasers such as Ne lasers and semiconductor lasers are beginning to be used. A characteristic of these lasers is that they can be turned on and off in a time-series manner, making them particularly promising light sources for copying machines with image processing functions, including intelligent copying machines, and printers for computer output. Among these, semiconductor lasers are attracting attention because their nature does not require electrical signal/optical signal conversion elements such as acousto-optic elements, and they can be made smaller and lighter. However, this semiconductor laser has a low output compared to a gas laser, and the oscillation wavelength is long (approximately 780 nm or more), so the spectral sensitivity of conventional photoreceptors is too high on the short wavelength side. It cannot be used as a photoreceptor using a laser as a light source. In recent years, electrophotographic photoreceptors using certain trisazo compounds have been proposed. (Japanese Patent Application Laid-open No. 57-116345, JP-A No. 57-182748) However,
Even the trisazo compounds proposed above are not satisfactory in terms of electrophotographic properties in the long wavelength region. (Object of the Invention) An object of the present invention is to provide a photoreceptor containing a specific trisazo compound that is stable against heat and light and has excellent carrier generation ability. Another object of the present invention is to provide an electrophotographic photoreceptor for a semiconductor laser that has high sensitivity in a long wavelength region, has a small residual potential, and has excellent durability whose characteristics do not change even after repeated use. It is in. Still another object of the present invention is to provide a photoreceptor that has sufficient practical sensitivity even to long wavelength light sources such as semiconductor lasers. As a result of intensive research to achieve the above object, the present inventors discovered that a trisazo compound having an asymmetric structure represented by the following general formula [] can act as an active ingredient of a photoreceptor, and the present invention This is the completed version. General formula [] In the formula, A represents a substituted or unsubstituted phenyl group or naphthyl group. As a substituent, an alkyl group,
Examples include an alkoxy group, a halogen atom, a nitro group, a cyano group, an acyl group, an acylamino group, and an amino group. Ar ¹ represents a substituted or unsubstituted naphthylene group, and Ar ² represents a substituted or unsubstituted phenylene group. Examples of the substituent include an alkyl group, an alkoxy group, a halogen atom, a nitro group, a cyano group, an acyl group, an acylamino group, an amino group, a sulfamoyl group, and a carbamoyl group. (Effects of the Invention) That is, in the present invention, by using the azo compound represented by the above general formula [] as a photoconductive substance constituting the photosensitive layer of the photoreceptor, the long wavelength region which is the object of the present invention can be achieved. An excellent photoreceptor that has outstanding electrophotographic properties such as charge retention, sensitivity, and residual potential, shows little fatigue deterioration even after repeated use, and has sufficient sensitivity especially in the long wavelength region of 780 nm or more. can be created. In particular, for the electrophotographic properties in this long wavelength range, compounds with a similar trisazo structure (described in JP-A-57-116345 and JP-A-57-182748), which are the well-known techniques listed above, are particularly effective. It has better performance than the symmetrical trisazo compound (described in JP-A-58-76841). Among the trisazo compounds useful in the present invention represented by the above general formula [], particularly preferred ones are represented by the general formula []. General formula [] In the formula, R ₁ and R ₂ are a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a nitro group, an ano group,
Represents an acyl group, cyano group, acylamino group, carbamoyl group or sulfamoyl group. Specific examples of trisazo compounds useful in the present invention represented by the general formulas [] and [] are listed below. The substituents in [Table A] represent the substituents of the respective corresponding parts of the following general formula []. General formula []

【table】

【table】

[Table] The above trisazo compounds can be synthesized by known methods. Synthesis Example 1 Synthesis of Exemplified Compound (6) 5.25 g of 1-amino-4-p-aminophenyl azonaphthalene was dissolved in 30 ml of concentrated sulfuric acid. Nitrosyl sulfuric acid (15 ml of concentrated sulfuric acid, 3.0 g of sodium sulfite) prepared in advance was added dropwise to this at -5°C to -10°C. After the addition, the mixture was stirred at the same temperature for 30 minutes and poured into 600 ml of ice water containing 20 g of ammonium phosphorus hexafluoride. The precipitated crystals were quickly collected by filtration. This was dissolved in 100 ml of N,N-dimethylformamide cooled to -15°C and used as a dropwise solution for the next coupling reaction. 2-Hydroxy-3-(4-methoxy-2-methylphenylcarbamoyl)-benzo[a]carbazole (Naphthol ASSR, manufactured by Hoechst) 15.0
g and 10 g of triethanolamine in 300 ml of N,N
- It was dissolved in dimethylformamide, and the above-mentioned solution was gradually added thereto while cooling with ice at 0°C. After the addition was completed, the mixture was further stirred at the same temperature for 2 hours, and then left at room temperature overnight, and the resulting crystals were collected by filtration. The crystals were washed twice with 200 ml of N,N-dimethylformamide and twice with 1 acetone, and then dried to obtain exemplified compound (6). Yield 1.40g Yield 6.5% This compound was confirmed by elemental analysis. Elemental analysis results (chemical formula is C ₆₆ H ₄₈ N ₁₀ O ₆ ) Element C H N Calculated value (%) 73.60 4.49 13.00 Actual value (%) 73.49 4.62 13.05 The asymmetric trisazo compound of the present invention has excellent photoconductivity. However, when producing an electrophotographic photoreceptor using this, it can be produced by providing a photosensitive layer in which the trisazo compound of the present invention is dispersed in a binder on a conductive support. Another method is to use the trisazo compound of the present invention as a carrier generating substance that takes advantage of its particularly excellent carrier generating ability among its photoconductivity, and to use it together with a carrier transporting substance that can effectively act in combination with this. It is also possible to make a so-called functionally separated electrophotographic photoreceptor, such as a laminated type or a dispersed type. Further, the trisazo compound used in the present invention can be used alone or in combination of two or more of the trisazo compounds represented by the above general formula [], or in combination with other disazo or trisazo compounds. It's okay. Various mechanical configurations of electrophotographic photoreceptors are known, and the electrophotographic photoreceptor of the present invention can take any of these forms. Usually, the configuration is as shown in FIGS. 1 to 6. In FIGS. 1 and 3, a carrier generation layer 2 containing the above-mentioned trisazo compound as a main component is provided on a conductive support 1.
and a carrier transport layer 3 containing a carrier transport substance as a main component. As shown in FIGS. 2 and 4, this photosensitive layer 4 may be provided via an intermediate layer 5 provided on a conductive support. When the photosensitive layer 4 has a two-layer structure in this manner, an electrophotographic photoreceptor having the most excellent electrophotographic properties can be obtained. Further, in the present invention, as shown in FIGS. 5 and 6, a photosensitive layer 4 comprising the carrier generating substance 7 dispersed in a layer 6 mainly composed of a carrier transporting substance is provided on the conductive support 1. It may be provided directly or via the intermediate layer 5. When the asymmetric trisazo compound of the present invention is used as a carrier generating substance, carrier transporting substances that can be used in combination with it include electron-accepting substances that easily transport electrons such as trinitrofluorenone or tetranitrofluorenone, as well as poly-
Polymers having a heterocyclic compound in the side chain such as N-vinylcarbazole, triazole derivatives, oxadiazole derivatives, imidazole derivatives, pyrazoline derivatives, polyarylalkane derivatives, phenylenediamine derivatives, hydrazone derivatives, amino-substituted Examples include electron-donating substances that easily transport holes, such as alcone derivatives, triarylamine derivatives, carbazole derivatives, and stilbene derivatives. Electron-donating substances are preferred for the present invention. The carrier transport materials used in the present invention are not limited to these. The carrier generation layer 2 constituting the photosensitive layer 4 having a two-layer structure is the conductive support 1 or the carrier transport layer 3.
It can be formed directly thereon or, if necessary, with an intermediate layer such as an adhesive layer or a barrier layer provided thereon, for example, by the following method. M-1 A method of applying a solution in which a trisazo compound is dissolved in a suitable solvent, or a solution in which a binder is added and mixed as necessary. M-2 A method in which a trisazo compound is made into fine particles in a dispersion medium using a ball mill, a homomixer, etc., and a binder is added if necessary to mix and disperse the resulting dispersion, and then a dispersion is applied. Examples of the solvent or dispersion medium used for forming the carrier generation layer include 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 using a binder in the carrier generation layer or carrier transport layer, any binder can be used, but it is preferable to use a film-forming polymer that is hydrophobic, has a high dielectric constant, and is electrically insulating. . Examples of such high molecular weight polymers include, but are not limited to, the following. P-1 Polycarbonate P-2 Polyester P-3 Methacrylic resin P-4 Acrylic resin P-5 Polyvinyl chloride P-6 Polyvinylidene chloride P-7 Polystyrene P-8 Polyvinyl acetate P-9 Styrene-butadiene copolymer P- 10 Vinylidene chloride-acronitrile copolymer P-11 Vinyl chloride-vinyl acetate copolymer P-12 Vinyl chloride-vinyl acetate-maleic anhydride copolymer P-13 Silicone resin P-14 Silicone-alkyd resin P-15 Phenol-formaldehyde resin P-16 Styrene-alkyd resin P-17 Poly-N-vinylcarbazole P-18 Polyvinyl butyral 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 μm to 20 μm, more preferably 0.05 μm to 5 μm. In addition, if the carrier generation layer or photosensitive layer is a dispersed system,
The particle size of the azo compound is preferably 5 μm or less, more preferably 1 μm or less. The conductive support used in the electrophotographic photoreceptor of the present invention includes a metal plate including an alloy, a metal drum or a conductive polymer, a conductive compound such as indium oxide, aluminum including an alloy, palladium, gold, etc. Examples include paper, plastic film, etc. that have been made conductive by coating, vapor depositing, or laminating a thin metal layer. In addition to high molecular weight polymers such as adhesive layers or barrier layers, organic high molecular substances such as polyvinyl alcohol, ethyl cellulose, and carboxymethyl cellulose, or aluminum oxide are used. The electrophotographic photoreceptor of the present invention has the above-mentioned structure, and as is clear from the examples described later, it has excellent charging characteristics and sensitivity characteristics, especially sensitivity characteristics in the long wavelength region, and can be used repeatedly. Even when the printer is used, fatigue deterioration is small, and the printer has excellent characteristics as a semiconductor laser printer. Hereinafter, the present invention will be specifically explained in Examples,
This does not limit the embodiments of the present invention. (Comparative experiment) Vinyl chloride-vinyl acetate-maleic anhydride copolymer "Eslec MF" was coated on polyester film.
-10'' (manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 0.05 μm was provided, and 2 g of exemplified compound (6) was added on top of it.
The dispersion was mixed with 110 ml of 2-dichloroethane and dispersed in a ball mill for 24 hours, and a thin layer of the dispersion was applied. After drying, the obtained piece was subjected to a self-recording spectrophotometer (model 320, Hitachi, Ltd.) to measure the transmission spectrum. Exemplary compounds (4), (1) and comparative compounds (1), (2), (3), (4) shown below were measured using the same method.

[Table] ε790/ελmax represents the value obtained by dividing the spectral absorption intensity of a compound at 790 nm by its spectral absorption intensity at λmax. From Table 1, it can be seen that the present invention was applied to comparative compounds (1), (2), (3), and (4) which are symmetric trisazo compounds, and to comparative compound (1) which is an asymmetric trisazo compound but whose coupler is naphthol ASMX. It can be seen that the compound has a significantly extended spectral absorption spectrum. When the coupler is changed from naphthol ASMX to benzo[a]carbazole in a symmetric trisazo compound (comparative compound (5) → comparative compound (2))
λmax becomes longer wavelength by 45nm. On the other hand, in the case of asymmetric trisazo, a similar change (comparison compound (1) → exemplified compound (6) shows a remarkable wavelength shift of 92 nm). Also, from the value of ε790/ελmax in Table 1, the compound of the present invention has a wavelength of 790 nm. It can be seen that it exhibits high spectral absorption characteristics even when
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 provided, and 4 g of Exemplary Compound (7) was added to the 1,2- The dispersion was mixed with 400 ml of dichloroethane and dispersed for 24 hours using a ball mill dispersion machine, and then applied to a dry film thickness of 0.5 μm to form a carrier generation layer. Furthermore, 30 g of the following compound (K-1) and 50 g of polycarbonate resin "Panlite L-1250" (manufactured by Teijin Chemicals) were added to 1,2-dichloroethane.
A carrier transport layer was formed by dissolving the solution in 400 ml and applying it to a film thickness of 12 μm after drying, thereby producing an electrophotographic photoreceptor on a drum. The spectral sensitivity of this photoreceptor at 790nm is
It was 0.85 μJ/cm ² (half exposure amount). Next, this photoreceptor is exposed to the laser beam intensity on the photoreceptor surface.
A live photo test was conducted using an experimental machine equipped with a semiconductor laser (790 nm) that outputs 0.85 mW. After the surface of the photoreceptor was charged to -6 KV, it was exposed to laser light and reverse development was performed at a bias voltage of -350 V. A good image without fogging was obtained. Moreover, this did not change even after repeating this 10,000 times. Example 2 A drum-shaped product was prepared in the same manner as in Example 1 except that exemplified compounds (4), (1), (6) and comparative compounds (1) and (2) were used instead of exemplified compound (7). A photoreceptor was obtained. The spectral sensitivity of each photoreceptor at 790 nm was as shown in Table 2.

[Table] Compounds of the present invention have higher sensitivity than comparative compounds. Next, in the actual photographic test using the experimental machine described in Example (1), the photoreceptor using the compound of the present invention gave good images without fogging, and these
No matter how many times it was repeated, it didn't change.

[Brief explanation of the drawing]

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

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor for a semiconductor laser, comprising a photosensitive layer containing a trisazo compound represented by the following general formula [] on a conductive support. General formula [] [In the formula, A represents a substituted or unsubstituted phenyl group or a naphthyl group, Ar ¹ represents a substituted or unsubstituted naphthylene group, and Ar ² represents a substituted or unsubstituted phenylene group. ]