JPH0259980B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to a novel electrophotographic photoreceptor having a photosensitive layer containing an azo compound. More specifically, the present invention relates to a highly durable electrophotographic photoreceptor that has high sensitivity and is suitable for repeated use. Conventionally, electrophotographic photoreceptors having a photosensitive layer mainly composed of an inorganic photoconductor such as selenium, zinc oxide, or cadmium sulfide have been widely known. However, these are not necessarily satisfactory in terms of sensitivity, thermal stability, moisture resistance, durability, etc., and in particular, selenium and cadmium sulfide are toxic, so there are restrictions in production and handling. On the other hand, electrophotographic photoreceptors having a photosensitive layer containing an organic photoconductive compound as a main component are relatively easy to manufacture, inexpensive, and easy to handle, and are generally more expensive than selenium photoreceptors. It has many advantages such as excellent thermal stability, and has attracted a lot of attention in recent years. Poly-N-vinylcarbazole is well known as such an organic photoconductive compound.
Electrophotographic photoreceptors having a photosensitive layer mainly composed of a charge transfer complex formed from this and a Lewis acid such as 2,4,7-trinitro-9-fluorenone are not necessarily satisfactory in terms of sensitivity and durability. . On the other hand, in laminated type or dispersed type functionally separated photoreceptors, in which the carrier generation function and the carrier transfer function are assigned to separate substances, each material has a wide selection range, and the charging characteristics, sensitivity, and durability are different. This method has the advantage that an electrophotographic photoreceptor having arbitrary electrophotographic properties such as properties can be produced relatively easily. Conventionally, various carrier-generating substances or carrier-transferring substances have been proposed. For example, electrophotographic photoreceptors have been put into practical use that have a photosensitive layer that combines a carrier generation layer made of amorphous selenium and a carrier transfer layer mainly composed of poly-N-vinylcarbazole. However, the carrier generation layer made of amorphous selenium has the disadvantage of poor durability. In addition, various proposals have been made to use organic dyes and pigments as carrier generating substances.
JP-A-52-4241, JP-A-54-46558,
Japanese Patent Publication No. 56-11945 and the like are already known. However, these azo compounds are not always satisfactory in terms of characteristics such as sensitivity, residual potential, and stability when used repeatedly, and the selection range of carrier transfer substances is also limited. The reality is that nothing that fully satisfies the wide range of demands has yet to be obtained. An object of the present invention is to provide an electrophotographic photoreceptor containing an azo compound that is stable to heat and light and has excellent carrier generation ability. Another object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity, low residual potential, and excellent durability whose characteristics do not change even after repeated use. Still another object of the present invention is to provide an electrophotographic photoreceptor containing an azo compound that can effectively act as a carrier generating substance even in combination with a wide variety of carrier transfer substances. As a result of intensive research to achieve the above object, the present inventors have discovered that an azo compound represented by the following general formula () can function as an active ingredient of a photoreceptor, and have completed the present invention. (In the formula, A is a divalent residue bonded to the N atom forming an azo with the C atom, R ₁ and R ₂ are hydrogen, an alkyl group that may have a substituent, a substituent ) That is, in the present invention, the azo compound represented by the general formula () is used as a photoconductive substance constituting the photosensitive layer of an electrophotographic photoreceptor. In this way, only the excellent carrier generation ability of the azo compound of the present invention is utilized, and carrier generation and transport are performed using separate substances. By using it as a carrier generating material in so-called function-separated electrophotographic photoreceptors, it has excellent film properties, excellent electrophotographic properties such as charge retention, sensitivity, and residual potential, and has little fatigue deterioration even after repeated use. It is possible to create an electrophotographic photoreceptor that exhibits stable characteristics without any change in the above-mentioned characteristics even when exposed to heat or light. Specific examples of the azo compound useful in the present invention represented by the above general formula include those having the following structural formula, but the azo compound of the present invention is not limited thereto. The azo compound represented by the above general formula is represented by the general formula
A diamine represented by H ₂ NA-A-NH ₂ (wherein A has the same meaning as above) is tetrazotized by a conventional method, and then a corresponding coupler is coupled in the presence of an alkali, or a tetrazonium of the diamine is Once the salt is isolated in the form of a borofusate salt or zinc chloride double salt, it can be isolated using a suitable solvent, e.g.
It can be easily synthesized by coupling with a coupler in a solvent such as N,N-dimethylformamide or dimethylsulfoxide in the presence of an alkali. Next, a method for synthesizing representative examples of the azo compound used in the present invention will be shown. Synthesis example (Exemplary compound No. 15) 3,3'-dichlorobenzine dihydrochloride 13.04g
(40 mmole) was added to a mixture of 20 ml of concentrated hydrochloric acid and 40 ml of water to disperse it, and a solution of 5.52 g (80 mmole) of sodium nitrite dissolved in water was added dropwise under ice cooling and allowed to react for about 1 hour under cooling. Ta. Then activated carbon was added and filtered to obtain an aqueous tetrazonium solution. 2-hydroxy-3- as a coupling component
(2-thiazolyl)naphthoic acid amide 8.3g
(30 mmole), as an organic amine, dissolve 6.5 g (65 mmole) of triethylamine in 1000 ml of DMF, and
Cooled to ~5°C. Next, the above diazonium salt solution was added dropwise to the coupler solution, and the resulting bluish-purple paste liquid was kept at 0 to 10°C and stirred for an additional 3 hours. The formed precipitate was filtered, thoroughly washed with acetone and then water, and finally washed again with acetone to obtain 6.2 g of blue-purple powder after drying. The melting point was over 350°C. Other azo compounds of the present invention can also be obtained according to the above synthesis example. The electrophotographic photoreceptor of the present invention has the general formula ()
It has a photosensitive layer containing one or more azo compounds represented by: Various forms of photosensitive layers are well known, and the photosensitive layer of the electrophotographic photoreceptor of the present invention may be in any of them. Usually, the photosensitive layer is of the type exemplified below. A photosensitive layer made of an azo compound A photosensitive layer containing an azo compound dispersed in a binder A photosensitive layer containing an azo compound dispersed in a well-known charge transfer substance The azo compound represented by the above general formula absorbs light and generates charge carriers with extremely high efficiency. Although the generated carrier can be transferred using an azo compound as a medium, it is preferable to transfer the generated carrier using a known charge transfer material as a medium. From this point of view, photosensitive layers in the form of and are particularly preferred. Charge transfer substances are generally classified into two types: electron transfer substances and hole transfer substances, and both can be used in the photosensitive layer of the photoreceptor of the present invention, and mixtures or mixtures of substances having the same function can be used. , mixtures of different functionalities can also be used. Examples of substances having electron transfer include electron-withdrawing compounds having electron-withdrawing groups such as nitro groups, cyano groups, and ester groups; examples of these include:
2,4,7-trinitrofluorenone, 2,4,
Nitrated fluorenone such as 5,7-tetranitrophylolenon, or tetracyano, quinodimethane, tetracyanoethylene, 2,4,5,7
Examples include compounds such as -tetranitroxanthone and 2,4,8-trinitrothioxanthone, and polymerized versions of these electron-absorbing compounds. Furthermore, examples of electron-donating organic photoconductive compounds that can be used as hole transport media include the following. etc. can be given. Other polymeric compounds that can be used include poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, polyglycidylcarbazole, polyvinylacenaphthylene, and ethylcarbazole formaldehyde resin. can. The carrier transfer substances are not limited to those described herein, and when used, one type or a mixture of two or more types of carrier transfer substances can be used. The electrophotographic photoreceptor of the present invention can be manufactured by a conventional method. For example, an electrophotographic photoreceptor having the above-mentioned type of photosensitive layer is prepared by coating a coating liquid obtained by dissolving or dispersing the azo compound represented by the general formula (1) in a suitable medium on a conductive support. It can be manufactured by drying and forming a photosensitive layer with a thickness of usually several μm to several tens of μm. As a medium for preparing the coating solution, butylamine,
A basic solvent that dissolves bisazo compounds such as ethylenediamine, or tetrahydrofuran, 1,
Ethers such as 4-dioxane: Ketones such as methyl ethyl ketone and cyclohexanone: Aromatic hydrocarbons such as toluene and xylene: Aprotic polar solvents such as N,N-dimethylformamide, acetonitrile, N-methylpyrrolidone, and dimethyl sulfoxide: Examples include alcohols such as methanol, ethanol, and isopropanol; esters such as ethyl acetate, methyl acetate, and methyl cellosolve acetate; and media for dispersing azo compounds such as chlorinated hydrocarbons such as dichloroethane and chloroform. When using a medium for dispersing the azo compound, the particle size of the azo compound is 5 μm or less, preferably 3 μm.
It is necessary to micronize the particles to 1 μm or less, optimally 1 μm or less. Furthermore, as the conductive support on which the photosensitive layer is formed, any of those employed in well-known electrophotographic photoreceptors can be used. Specifically, examples include metal drums and sheets made of aluminum, copper, etc., and laminates and vapor deposits of these metal foils. Further examples include plastic films, plastic drums, and paper which are coated with a conductive substance such as metal powder, carbon black, copper iodide, or polymer electrolyte together with a suitable binder to conductivity treatment. Also included are plastic sheets and drums that contain conductive substances such as metal powder, carbon black, and carbon fibers and are rendered conductive. An electrophotographic photoreceptor having the above-mentioned type of photosensitive layer can be manufactured by dissolving a binder in a coating liquid used for forming the above-mentioned type of photosensitive layer. In this case, the medium of the coating liquid is preferably one that dissolves the binder. As a binder, styrene, vinyl acetate,
Various polymers such as polymers and copolymers of vinyl compounds such as acrylic esters and methacrylic esters, phenoxy resins, polysulfones, arylate resins, polycarbonates, polyesters, cellulose esters, cellulose ethers, urethane resins, epoxy resins, and acrylic polyol resins. can be mentioned. The amount of binder used is usually
It is in the range of 0.1 to 5 times the weight. In forming this type of photosensitive layer, it is preferable that the bisazo compound be present in the binder in the form of fine particles, for example, with a particle size of 3 μm or less, particularly 1 μm or less. Similarly, an electrophotographic photoreceptor having the above-mentioned type of photosensitive layer can be manufactured by dissolving a charge transfer medium in the coating liquid used to form the above-mentioned type of photosensitive layer. As the charge transfer medium, any of those exemplified above can be used. Apart from charge transport media which can themselves be used as binders, such as polyvinylcarbazole and polyglycidylcarbazole, it is preferred to use other binders. As the binder, any of those exemplified above can be used. In this case, the amount of binder used is usually in the range of 5 to 10 μm times the weight of the azo compound, and the amount of charge transfer medium used is usually 0.2 times the weight of the binder.
~1.5 times by weight, preferably 0.3 to 1.2 times by weight. In the case of charge transfer media that can themselves be used as binders, typically 5 to
10 times the weight is used. In this type of photosensitive layer, as in the above-mentioned type of photosensitive layer, it is preferable that the bisazo compound is present in the charge transport medium and the binder in the form of fine particles. If a coating solution obtained by dissolving a charge transfer medium in a suitable medium is applied onto the photosensitive layer of the type of ~ above and dried to form a charge transfer layer, an electrophotographic photosensitive layer having the photosensitive layer of the type described above can be obtained. body can be manufactured. In this case, the photosensitive layer of the type ~ plays the role of a charge generation layer. The charge transfer layer does not necessarily need to be provided above the charge generation layer, but may be provided between the charge generation layer and the conductive support. However, the former is preferable in terms of durability.
The charge transfer layer is formed in the same manner as the photosensitive layer described above. That is, the coating liquid for forming the photosensitive layer described above, except that the azo compound is removed, may be used as the coating liquid. Typically the charge generating layer is between 5 and 50 micrometers thick. Of course, the photosensitive layer of the electrophotographic photoreceptor of the present invention may contain a known sensitizer. Suitable sensitizers include Lewis acids and dyes that form charge transfer complexes with organic photoconductive materials. Examples of Lewis acids include chloranil, 2,3
-dichloro-1,4-naphthoquinone, 2-methylanthraquinone, 1-nitroanthraquinone, 1
- Quinones such as chlor-5-nitroanthraquinone, 2-chloroanthraquinone, and phenanthrenequinone, aldehydes such as 4-nitropenzaldehyde, 9-penzoylanthracene, indandione, 3,5-dinitrobenzophenone,
Ketones such as 3,3',5,5'-tetranitrobenzophenone, acid anhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride, tetracyanoethylone,
Cyano compounds such as terephthalmalonitrile and 4-nitrobenzalmalonnitrile: Electron withdrawal such as 3-benzalphthalide, 3-(a-cyano p-nitrobenzal) phthalide, 3-(a-cyano-p-nitrobenzal) phthalides, etc. Examples include sexual compounds. Examples of dyes include triphenylmethane dyes such as methyl violet, brilliant green, and crystal violet, thiazine dyes such as methylene blue, quinone dyes such as quinizarin, cyanine dyes, pyrylium salts, thiapyrylium salts, and benzopyrylium salts. It will be done. In addition to these, it may contain inorganic photoconductive fine particles such as selenium and selenium-arsenic alloys, and organic photoconductive pigments such as copper, phthalocyanine pigments, and perylene pigments. Furthermore, the photosensitive layer of the electrophotographic photoreceptor of the present invention may contain a well-known plasticizer in order to improve film formability, flexibility, and mechanical strength. Examples of the plasticizer include notaric acid esters, phosphoric acid esters, epoxy compounds, chlorinated paraffins, chlorinated fatty acid esters, aromatic compounds such as methylnaphthalene, and the like. Moreover, it goes without saying that it may have an adhesive layer, an intermediate layer, and a transparent insulating layer, if necessary. The photoreceptor using the azo compound of the present invention has high sensitivity and good color sensitivity, and when used repeatedly, there is little variation in sensitivity and chargeability, little optical fatigue, and extremely high durability. It is. Furthermore, the photoreceptor of the present invention can be widely used in electrophotographic applications such as photoreceptors for printers using lasers, cathode ray tubes (CRTs), and light emitting diodes (LEDs) as light sources in addition to electrophotographic copying machines. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 Vinyl chloride:vinyl acetate:maleic anhydride copolymer (Sekisui Chemical Co., Ltd., Eslec MF-) was deposited on a conductive support made of a polyester film laminated with aluminum foil (Alpet 85, manufactured by Daido Chemical Co., Ltd., aluminum film thickness: 10 μm). 10) Thickness 0.05μ consisting of
2 g of Exemplified Compound No. 1 and 2 g of polyarylate resin (U-100 manufactured by Unitika) were added to 100 ml of 1,2-dichloroethane and dispersed in a paint conditioner for about 1 hour. A carrier-generating layer is formed by coating and drying an azo compound dispersion liquid on the intermediate layer so that the film thickness after drying becomes 0.5 μm, and further containing a carrier transfer substance N,
N-dibenzylaminobenzaldehyde-1,1
-A solution prepared by dissolving 5 g of diphenylhydrazone in 50 ml of 1,2-dichloroethane together with 7 g of polyarylate resin is coated and dried to form a carrier transport layer, and dried to form a carrier transfer layer. A photoreceptor was produced. This photoconductor was heated at a room temperature of 30℃.
After storing it in a dark place for one week, the electrophotographic photoreceptor was tested using an electrostatic paper tester "SP-428" (manufactured by Kawaguchi Electric Seisakusho).
The following characteristic tests were conducted. That is, a voltage of -6 kV is applied to the charger and the photosensitive layer is charged by corona discharge for 5 seconds, and the potential at that time is
V ₀ (-V), then the illuminance at the surface of the photosensitive layer is
The exposure amount E1/2 (lux·sec) required to attenuate the surface potential of the photosensitive layer by half by irradiating it with light from a halogen lamp under a condition of 30 lux was determined. Also
Surface potential after exposure with an exposure amount of 30 lux/second,
That is, the residual potential _E50 (-V) was determined. Similar measurements
I did it 500 times. In addition, a tungsten lamp was used as a light source to eliminate residual potential at 300 lux.
Further exposure was performed for 0.3 seconds to completely reduce the residual potential to zero. The results are shown in Table 1.

[Table] Examples 2 to 5 A total of four types of electrophotographic photoreceptors of the present invention were prepared in the same manner as in Example 1 except that Exemplary Compounds 2, 5, 18, and 24 were used as carrier generating substances, respectively. Similar characteristic tests were conducted for each of them. The results are shown in Table 2.

[Table] Example 6 An intermediate layer with a thickness of 0.04 μ made of vinyl chloride: vinyl acetate (87:13) copolymer (VYHH manufactured by UCIC) was formed on the outer surface of a drum made of aluminum with a diameter of 60 mm, 4g of Exemplified Compound 15 was 1,2-
A dispersion obtained by adding 400 ml of dichloroethane and dispersing it for about 3 hours using a paint conditioner was applied onto the intermediate layer so that the film thickness after drying was 0.5 μm and dried to form a carrier generation layer. . On this carrier generation layer, the structural formula A solution prepared by dissolving 10 g of the carrier transfer substance N,N-diallylaminobenzaldehyde-1-phenyl-1-methylhydrazone shown in 100 ml of 1,2-dichloroethane together with 12 g of polycarbonate resin (Teijin Panlite L-1250) was dried. A carrier transfer layer was formed by coating and drying to a film thickness of 15 μm, thereby producing a drum-type electrophotographic photoreceptor according to the present invention. When this electrophotographic photoreceptor was installed in our modified commercially available cartridge-type electrophotographic copying machine and a copied image was formed, a clear visible image with high contrast and faithful to the original was obtained. Copy again
This was repeated 1,000 times, and until the end, a visible image equivalent to the first one was obtained. Example 7 The reflection spectrum of the drum-type electrophotographic photoreceptor obtained in Example 6 was measured using a spectrophotometer equipped with an integrating sphere (UV-365 manufactured by Shimadzu), and the graph thereof is shown in FIG. From this graph, it was found that the maximum absorption wavelength of this photoreceptor in the visible region was around 675 nm. Furthermore, when the spectral sensitivity at 670 nm and 680 nm was measured using a monochrome meter, the energy required to halve the potential was approximately 3.5 erg/cm ² for both wavelengths, which is a very high photoreceptor. ) was found to be a photoreceptor that can be used in practical applications. Examples 8 to 12 An intermediate layer with a thickness of 0.05μ made of vinyl chloride:vinyl acetate copolymer (Kanebirakku L-CP manufactured by Kaneka Co., Ltd.) was formed on a conductive support made of a polyester film on which aluminum was vapor-deposited. Compound 7,
A solution of azo compounds 21, 31, 42, and 59 dissolved in n-butylamine is applied onto the intermediate layer to determine the film thickness.
A carrier generation layer of 0.1μ was formed. Next, 5 g of 1-diethylaminophenyl-3-phenyl-5-styrylpyrazoline and a polyester resin (Vylon manufactured by Toyobo Co., Ltd.) were placed on the carrier generation layer.
A solution prepared by dissolving 5 g of 200) in 40 ml of 1,2-dichloroethane was coated and dried to form a carrier transfer layer so that the film thickness after drying was 14 μm, thereby producing an electrophotographic photoreceptor of the present invention. The reflection/absorption curves of these five types of photoreceptors in total were determined, and the maximum absorption wavelength in the visible to near-infrared region and the energy required to halve the potential at that wavelength were determined according to Example 7. The result is the third
As shown in the table. Incidentally, the initial potential V ₀ of all photoreceptors exceeded 500 (-V).

[Table] Example 13 Styrene was placed on an Al plate with grained surface oxidation:
Methyl methacrylate: methacrylic acid copolymer (styrene: methyl methacrylate = 2:1 weight ratio, acid value 185), Exemplified Compound 58 and tonitrofluorenone were blended in a weight ratio of 1.5:1:0.3, and this was mixed in dioxane. Apply the dissolved (resin component, trinitrofluorenone) dispersed (azo compound) solution and dry.
A single-layer photoreceptor with a film thickness of 6μ was fabricated. The photoreceptor of the present invention thus prepared was subjected to an electrophotographic property test using the electrostatic paper tester described above. The applied voltage was +6kV V ₀ =420 (+V) E1/2 = 8 (lux·sec). In addition, this photoreceptor is visualized with a developer (toner), and then an alkaline processing solution (for example, 3% triethanolamine, 10% ammonium carbonate, and 20%
(polyethylene glycol with an average molecular weight of 190 to 210), the toner-free areas are easily eluted, and by washing with water containing sodium silicate, a printing plate can be easily created. Ta. When offset printing is performed using this original plate, approximately
It was found that it could withstand printing of 100,000 sheets. The optimum exposure amount (light source: halogen lamp) for obtaining a visible toner image was 50 lux, and the printing original plate was created by direct plate making without using any plate material.

[Brief explanation of the drawing]

FIG. 1 is a reflection/absorption curve of the photoreceptor of the present invention in Example 7.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing an azo compound represented by the following general formula () on a conductive support. (In the formula, A is a divalent residue bonded to the N atom forming an azo with the C atom, R ₁ and R ₂ are hydrogen, an alkyl group that may have a substituent, a substituted Phenyl group which may have a group, halogen, nitro,
It is a frill group. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer contains a carrier transfer substance and a carrier generation substance, and the carrier generation substance is an azo compound represented by the general formula (). 3. The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. (In the formula, m and n are 0 or 1, and R ₁ and R ₂ have the same meanings as in item 1.) 4. A patent in which the azo compound represented by the general formula () is a compound represented by the following structural formula. An electrophotographic photoreceptor according to claim 1. (In the formula, X is hydrogen, methoxy, halogen, methyl, or nitro, and R ₁ and R ₂ have the same meanings as in item 1.) 5. The azo compound represented by the above general formula () is represented by the following structural formula. The electrophotographic photoreceptor according to claim 1, which is a compound. (In the formula, Y is hydrogen, halogen, cyano group,
R ₁ and R ₂ have the same meaning as the first term. ) 6 The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. (In the formula, Z is -O-, -S-, and R ₁ and R ₂ have the same meanings as in the first term.) 7. The azo compound represented by the general formula () is a compound represented by the following structural formula. An electrophotographic photoreceptor according to claim 1. (In the formula, R ₃ is hydrogen, alkyl, aryl, benzyl which may have a substituent, or phenyl which may have a substituent, and R ₁ and R ₂ have the same meanings as in the first term. ) 8. The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. (In the formula, R ₁ and R ₂ have the same meanings as in paragraph 1.) 9. The electrophotography according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. Photoreceptor. (In the formula, R ₄ is hydrogen, alkyl, aryl, propargyl, or benzyl which may have a substituent, and R ₁ and R ₂ have the same meanings as in item 1.) 10 Represented by the above general formula () The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the following structural formula is a compound represented by the following structural formula. (In the formula, R ₅ is alkyl, aryl, propargyl,
It is hydrogen, and R ₁ and R ₂ have the same meanings as in the first term. ) 11. The electrophotographic photoreceptor according to claim 1, wherein the azo compound represented by the general formula () is a compound represented by the following structural formula. (In the formula, R ₄ and R ₅ are hydrogen, halogen, alkyl,
Methoxy and nitro, and R ₁ and R ₂ have the same meanings as in the first term. )