JPH0473948B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Industrial Application Field The present invention relates to an electrophotographic photoreceptor, and in detail,
The present invention relates to a novel electrophotographic photoreceptor having a photosensitive layer containing an azo pigment. More specifically, the present invention relates to a highly durable electrophotographic photoreceptor having high sensitivity and sensitivity up to the near-infrared region suitable for repeated use. (B) Prior Art and its Problems 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.
Furthermore, in particular, selenium and cadmium sulfide have limitations in production and handling due to their toxicity.
On the other hand, an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductive compound as a main component must be relatively easy to manufacture. In addition, it generally has many advantages compared to selenium photoreceptors, such as superior thermal stability.
It has attracted a lot of attention in recent years. Poly-N-vinylcarbazole is well known as such an organic photoconductive compound, and a charge transfer complex formed from poly-N-vinylcarbazole and a Lewis acid such as 2,4,7-trinitro-9-fluorenone An electrophotographic photoreceptor having a photosensitive layer containing as a main component is 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 It has the advantage that an electrophotographic photoreceptor having arbitrary electrophotographic properties can be produced relatively easily. Conventionally, various carrier-generating substances or carrier-transferring substances have been proposed. For example, an electrophotographic photoreceptor has been put into practical use that has 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. Furthermore, 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 pigments are not necessarily 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, making them difficult to use in electrophotographic processes. The reality is that nothing that fully satisfies a wide range of demands has yet been obtained. (C) Object of the Invention An object of the invention is to provide an electrophotographic photoreceptor containing an azo pigment 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 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 pigment that can effectively act as a carrier generating substance even in combination with a wide variety of carrier transfer substances. (D) Structure of the Invention As a result of intensive research to achieve the above object, the present inventors have discovered that an azo pigment represented by the following general formula () can act as an active ingredient of a photoreceptor, and have developed the present invention. It is completed. (In the formula, Cp is a coupler residue.) Cp represents a coupler residue that reacts with a diazo group, and a coupler residue having the structure shown by the following general formula () is particularly effective. (In the formula, Y is fused with a benzene ring to form naphthalene,
Indicates the atomic group necessary to form a polycyclic aromatic ring such as an anthracene ring or a heterocyclic ring such as a carbazole ring, benzocarbazole ring, or dibendifuran ring by condensation with a benzene ring. R ₁ is an optionally substituted alkyl group (e.g., methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, amyl group, 1-octyl group, benzyl group, p-chlorobenzyl group, 3,
4-dichlorobenzyl group, p-methylbenzyl group, 2-phenylethyl group, α-naphthylmethyl group, β-naphthylmethyl group) aryl group (e.g. phenyl group, tolyl group, xylyl group, biphenyl group, chlorophenyl group, dichlorophenyl group) enyl group, bromphenyl group, methoxyphenyl group, ethoxyphenyl group, butoxyphenyl group, phenoxyphenyl group, nitrophenyl group, cyanophenyl group, hydroxyphenyl group, carboxyphenyl group, N,N-dimethylaminophenyl group , α,
α,α-trifluoromethylphenyl group, methylthiophenyl group, α-naphthyl group, β-naphthyl group, etc.) R ₂ is R ₁ and a heterocyclic group (e.g., thiazolyl group,
5-nitrothiazolyl group, carbazolyl group, indolyl group, pyrrolyl group, acridyl group, benzo(b)
thiophenyl, benzimidazolyl group, oxazolyl group, chloroxazolyl group, triazolyl group, piperidyl group, pyridyl group, quinolyl group). R ₃ represents O, S, -NH, R ₄ and R ₅ are hydrogen, an optionally substituted alkyl group, a nitro group, a methoxy group, an ethoxy group, an acetyl group, a cyano group,
Indicates halogen. Z is a chain hydrocarbon necessary to form a 5-membered ring or a 6-membered ring. ] That is, in the present invention, by using the azo pigment represented by the general formula () as a photoconductive substance constituting the photosensitive layer of an electrophotographic photoreceptor, the azo pigment of the present invention has excellent carrier generation properties. This is done by using separate substances for the generation and movement of carriers. 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 even with repeated use, it has little fatigue deterioration. It is possible to produce 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 pigment useful in the present invention represented by the above general formula include those having the following structural formula, but the azo pigment of the present invention is not limited thereto. Exemplary azo pigments The tris azo pigment represented by the above general formula () has the general formula The trivalent amino compound represented by is diazotized by a conventional method, and then the corresponding coupler is coupled in the presence of an alkali, or the diazonium salt of the trivalent amino compound described above is converted into a borofluoride salt or a zinc chloride complex. After isolation in the form of a salt, etc., it is combined with a coupler in an appropriate solvent (e.g., N,N-dimethylformamide, dimethyl sulfoxide, ethanol, dioxane) in the presence of an organic or inorganic alkali. It can be easily synthesized by coupling reaction. The electrophotographic photoreceptor of the present invention has the general formula ()
It has a photosensitive layer containing one or more azo pigments 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 pigment A photosensitive layer containing an azo pigment dispersed in a binder A photosensitive layer containing an azo pigment dispersed in a well-known charge transfer substance Photosensitive layer laminated with a charge transfer layer containing a photosensitive layer The azo pigment represented by the above general formula generates charge carriers with extremely high efficiency when it absorbs light. Although the generated carrier can be transferred using an azo pigment as a medium, it is preferable to use 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-tetranitrofluorenone, or compounds such as tetracyanoquinodimethane, tetracyanoethylene, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, Examples include polymerized 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 may be used include poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, polyglycidylcarbazole, polyvinylacenaphthylene, ethylcarbazole-formaldehyde resin, etc. I can do it. 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 can be prepared by coating a coating solution obtained by dissolving or dispersing an azo pigment represented by the above general formula () in a suitable medium on a conductive support; dry,
It can be manufactured by forming a photosensitive layer with a thickness of usually several 0.1 μm to several tens of μm. Examples of media for preparing the coating solution include basic solvents that dissolve tetrakisazo pigments such as n-butylamine and ethylenediamine, ethers such as tetrahydrofuran and 1,4-dioxane, and ketones such as methyl ethyl ketone and cyclohexanone.
Aromatic hydrocarbons such as toluene and xylene: N, N
-dimethylformamide, acetonitrile, N-
Aprotic polar solvents such as methylpyrrolidone and dimethylsulfoxide: methanol, ethanol,
Examples include alcohols such as isopropanol; esters such as ethyl acetate, methyl acetate, and methyl cellosolve acetate; and media for dispersing azo pigments such as chlorinated hydrocarbons such as dichloroethane and chloroform. When using a medium for dispersing azo pigments,
The azo pigment has a particle size of 5 μm or less, preferably 3 μm or less,
Optimally, it is necessary to make the particles smaller than 1 μm. 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, paper, etc. 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 tetrakisazo pigment 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 for forming 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 1000 times the weight of the azo pigment, and the amount of charge transfer medium used is usually 0.2 to 3.0 times the weight of the binder.
times the weight, preferably in the range of 0.3 to 1.2 times the weight. In the case of a charge transport medium which itself can be used as a binder, it is usually used 5 to 10 times the weight of the azo pigment. In this type of photosensitive layer, as in the above-mentioned type of photosensitive layer, it is preferable that the azo pigment 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 the azo pigment may be used as the coating liquid. Typically the charge transport layer is 5-50 μm 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 chloro-5-nitroanthraquinone, 2-chloroanthraquinone, and phenanthrenequinone, aldehydes such as 4-nitrobenzaldehyde, 9-benzoylanthracene, indanedione, 3,5-dinitrobenzophenone,
Ketones such as 3,3',5,5'-tetranitrobenzophenone, acid anhydrides such as phthalic anhydride and 4-chloronaphthalic anhydride, tetracyanoethylene, terephthalmalondinitrile, 4- Cyano compounds such as nitrobenzalmalonenitrile: 3-
Examples include electron-withdrawing compounds such as benzalphthalide, 3-(α-cyano-p-nitrobenzal) phthalide, and 3-(α-cyano-p-cyanobenzal) phthalides. 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, biryllium salts, thiapyrylium salts, and benzobyrylium salts. It will be done. In addition, inorganic photoconductive fine particles such as selenium and selenium-arsenic alloys, and organic photoconductive pigments such as copper-phthalocyanine pigments and perylene pigments may also be contained. 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 aromatic compounds such as phthalate ester, phosphate ester, epoxy compound, chlorinated paraffin, and chlorinated fatty acid ester methylnaphthalene. 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 pigment of the present invention has high sensitivity and good color sensitivity, and when used repeatedly,
Less fluctuation in sensitivity and chargeability, less photo fatigue,
It is also extremely durable. Furthermore, the photoreceptor of the present invention can be widely used in electrophotographic applications such as photoreceptors for printers and printing plates that use lasers, cathode ray tubes (CRTs), and light emitting diodes (LEDs) as light sources in addition to electrophotographic copying machines. (E) Examples 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 the gist thereof is exceeded. Example 1 Vinyl chloride:vinyl acetate:maleic anhydride copolymer (Eslec MF-, manufactured by Sekisui Chemical Co., Ltd.) was coated on a conductive support made of a polyester film laminated with aluminum foil (Albet 85 manufactured by Daido Kako Co., Ltd., aluminum film thickness 10 μm). 10) to form a 0.05μ thick intermediate layer, add 2g of Exemplary Azo Pigment No. 42 and 2g of polyarylate resin (Unitika U-100) to 100ml of 1,2-dichloroethane and apply paint conditioner. An azo pigment dispersion obtained by dispersing the azo pigment in the intermediate layer for about 1 hour is coated and dried on the intermediate layer so that the film thickness after drying becomes 0.3μ to form a carrier generation layer, and further a carrier transfer substance N, N
-dibenzylaminobenzaldehyde-1,1-
A solution of 5 g of diphenylhydrazone and 7 g of polyarylate resin dissolved in 50 ml of 1,2-dichloroethane is coated and dried to a film thickness of 12 μm to form a carrier transfer layer. The body was created. After storing this photoreceptor at room temperature at 30°C in a dark place for one week, it was tested using an electrostatic paper tester "SP-428" (manufactured by Kawaguchi Denki Seisakusho).
The following characteristic tests were conducted. That is, a voltage of -6 KV is applied to the charger for 5 seconds to charge the photosensitive layer by corona discharge, and the potential Vo (-V) at that time and the illuminance on the surface of the photosensitive layer are then
The exposure amount E1/2 (lux·sec) required to attenuate the surface potential of the photosensitive layer by 1/2 was determined by irradiating light from a halogen lamp under a condition of 3 lux. Further, the surface potential after exposure with an exposure amount of 30 lux·sec, that is, the residual potential V ₃₀ (−V) was determined. Similar measurements were repeated 500 times. Incidentally, a tungsten lamp was used as a light source to eliminate residual potential, and further exposure was performed at 300 lux 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 five types of electrophotographic photoreceptors of the present invention were prepared in the same manner as in Example 1, except that exemplified azo pigments 3, 11, 18, and 53 were used as carrier generating substances. Similar characteristic tests were conducted on each of them. The results are shown in Table 2.

[Table] Example 6 The reflection spectrum of the sheet-like electrophotographic photoreceptor obtained in Example 1 was measured using a spectrophotometer equipped with an integrating sphere (Shimadzu UV-365). It was found that the maximum absorption wavelength of the nanoparticles is broad from 600nm to around 700nm. Further, the spectral sensitivity of this photoreceptor between 500 nm and 750 nm was measured using a monochlormeter, and the results are shown in FIG. This figure shows that this photoreceptor has a nearly constant maximum spectral sensitivity in the vicinity of 650 nm to 720 nm, and is a photoreceptor that can withstand practical sensitivity even when a light emitting diode, He-Ne laser, etc. is used as a light source. . Example 7 On the outer surface of a drum made of aluminum with a diameter of 60 mm, an intermediate layer with a thickness of 0.02 μ made of butyral resin (polymerization degree of about 700, manufactured by Wako Pure Chemical Industries, Ltd.) was formed, and 2 g of exemplified azo pigment 29 was added to the polyarylate. A dispersion obtained by adding 2 g of resin dissolved in 100 ml of tetrahydrofuran 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. A carrier generation layer was formed. On this carrier generation layer, the structural formula N,N-diethylaminobenzaldehyde-N-
1, along with 11 g of phenyl-N-allyl hydrazone and 12 g of polycarbonate resin (Teijin Panlite L-250).
A solution dissolved in 100 ml of 2-dichloroethane was applied and dried to a film thickness of 15 μm after drying to form a carrier moving layer, 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. Also, although I repeated copying 1000 times, the first
A visible image equivalent to the second time was obtained. Example 8 The reflection spectrum of the drum-type electrophotographic photoreceptor obtained in Example 7 was measured using the spectrophotometer (UV-365 manufactured by Shimadzu) used in Example 6, and the maximum absorption in the visible region of this photoreceptor was determined. The wavelengths were found to be around 670nm and 760nm. Furthermore, the spectral sensitivity of this photoreceptor between 550 nm and 850 nm was measured using a monochromator, and the results are shown in FIG. It was found that the photoreceptor has sufficient practical sensitivity even when a light emitting diode or semiconductor laser is used as a light source. Example 9 Styrene:n on a grained surface oxidized Al plate
-Butyl methacrylate: methacrylic acid copolymer (styrene: n-butyl methacrylate = 1:2
Weight ratio, acid value 250) and example azo pigment 18 and N,N
-Diethylaminobenzaldehyde-1-phenyl group-1-ethylhydrazone was blended at a polymerization ratio of 1.5:0.25, and this was dissolved (resin component hydrazone compound) dispersed (azo pigment) in dioxane.A liquid was applied and dried, and the film thickness was Electrophotographic characteristics tests were conducted on the 5μ single-layer photoreceptor using the electrostatic paper tester described above. Applied voltage was +6KV Vo=510Volt E1/2=5.3lux・sec. In addition, this photoreceptor is visualized with a developer (toner), and then an alkaline processing aqueous solution (for example, 3% triethanolamine, 10% ammonium carbonate, 15%
When treated with polyethylene glycol (% average molecular weight 190-210, 5% benzyl alcohol), the toner-free areas are easily eluted, and then washed with water containing sodium silicate to easily create a printing plate. I was able to do that. When offset printing is performed using this original plate, approximately
It was found that it could withstand printing of 100,000 sheets. In addition, the optimum exposure amount (light source: halogen lamp) was 100 lux·sec to obtain a visible toner image, and the printing original plate was prepared by direct plate making without using any plate material. Example 10 The spectral sensitivities of the printing plate obtained in Example 9 at 750 nm and 780 nm were 0.35 μJ/cm ² and 0.40 μJ/cm ² .
When offset printing was carried out in the same manner as in Example 9 except that a 780 nm laser beam was used as the light source, an excellent print that could withstand the 100,000th printing as in Example 9 and had a resolution of 50 lines per mm or more was obtained. It turned out to be a version.

[Brief explanation of the drawing]

1 and 2 are spectral sensitivity curves of the photoreceptors of the present invention in Examples 6 and 8.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing an azo pigment represented by the following general formula () on a conductive support. (In the formula, Cp is a coupler residue.) 2. A patent in which the photosensitive layer contains a carrier transfer substance and a carrier generation substance, and the carrier generation substance is an azo pigment represented by the above general formula (). An electrophotographic photoreceptor according to claim 1. 3. The electrophotographic photoreceptor according to claim 1, wherein the azo pigment represented by the general formula () is a compound represented by the following structural formula. (In the formula, Cp is a coupler residue.)