JPH0448225B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a novel photoconductive coating and a highly sensitive electrophotographic photoreceptor using the same. BACKGROUND ART Conventionally, pigments and dyes exhibiting photoconductivity have been published in numerous publications. For example, ``RCA Review'' Vol.23, P413~P419
(1962.9) published on the photoconductivity of phthalocyanine pigments, and an electrophotographic photoreceptor using this phthalocyanine pigment was patented in the United States.
This is disclosed in Publication No. 3397086, US Patent No. 3816118, and the like. In addition, examples of organic semiconductors used in electrophotographic photoreceptors include US Pat. No. 4,315,983
No. 4,327,169 and “Reseach”
Discloslosure"20517 (May 1981), pyrylium yarn dye, methine squaritate dye shown in U.S. Patent No. 3824099, U.S. Patent No. 3898084, U.S. Patent No. 4251613, etc. Examples include disazo pigments.Such organic semiconductors are easier to synthesize than inorganic semiconductors, and can be synthesized as compounds that have photoconductivity for light in the required wavelength range. Electrophotographic photoreceptors in which a conductive support is coated with a film of an organic semiconductor have the advantage of improved color sensitivity, but only a few of them can be put to practical use in terms of sensitivity and durability. Problems to be Solved by the Invention The first object of the present invention is to provide a highly sensitive photoconductive coating.The second object of the invention is to provide a highly sensitive photoconductive coating. It is an object of the present invention to provide an electrophotographic photoreceptor. A third object of the present invention is to provide an electrophotographic photoreceptor suitable for an electrophotographic copying machine. This objective is achieved by malotropocyanin represented by the following general formula [].
That is, the present invention comprises an electrophotographic photoreceptor characterized by being provided with a photoconductive coating containing malotropocyanine represented by the following general formula [] and a photosensitive layer having the coating. general formula In the formula, n represents 0, 1 or 2, and R ₁ to _{R 6} are alkyl groups such as methyl, ethyl, and propyl; aralkyl groups such as benzyl and phenethyl;
Aryl groups such as phenyl and naphthyl, these groups include halogen atoms such as chlorine, bromine, and iodine, cyano groups, nitro groups, alkoxy groups such as methoxy, ethoxy, and propoxy, dimethylamino, diethylamino, diphenylamino, and dibenzylamino. ,
It may be substituted with a substituted amino group such as morpholino, piperidino, pyrrolidino, or a hydroxyl group. Alternatively, it represents a residue in which two adjacent groups form a fused ring with the tropylium ring. Next, a general method for producing malotropocyanin used in the present invention will be described. Compounds represented by the general formula [] generally have the reaction formula It can be synthesized by The symbols in the formula have the same meanings as those in the general formula []. For details on the synthesis method, see Chem.Ber. 97 , 2050~
2065 (1964). Specific examples of the malotropocyanin compound used in the present invention are listed below. In malotropocyanine compounds, the absorption shifts to longer wavelengths as the methine chain lengthens. The absorption spectra of representative examples of the above compounds are shown in the drawings. The coating containing malotropocyanine described above exhibits photoconductivity and can therefore be used in the photosensitive layer of the electrophotographic photoreceptor described below. That is, in a specific example of the present invention, an electrophotographic photoreceptor is formed by forming a film of the above-mentioned malotropocyanine on a conductive support by vacuum evaporation, or by dispersing it in a suitable binder and forming a film. It can be prepared. In a preferred embodiment of the present invention, the photoconductive coating described above can be applied as a charge generation layer in an electrophotographic photoreceptor in which the photosensitive layer is functionally separated into a charge generation layer and a charge transport layer. The charge generation layer contains as much of the above-described photoconductive compound as possible in order to obtain sufficient absorbance, and is preferably a thin film layer, e.g., 5μ or less, in order to shorten the range of the generated charge carriers. is 0.01
A thin film layer having a thickness of ~1 μm is preferable.
This means that most of the incident light is absorbed by the charge generation layer, generating many charge carriers.
Furthermore, this is due to the fact that the generated charge carriers need to be injected into the charge transport layer without being deactivated by recombination or trapping. The charge generation layer can be formed by dispersing the above-mentioned compound in a suitable binder and coating it on the substrate, or it can be obtained by forming a vapor deposited film using a vacuum vapor deposition apparatus. . The binder that can be used when forming the charge generation layer by coating can be selected from a wide range of insulating resins.
It can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene and polyvinylpyrene. Preferably, polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.) polycarbonate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine, cellulose resin, urethane resin, Examples include insulating resins such as epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. The resin contained in the charge generation layer is 80% by weight or less, preferably
40% by weight or less is suitable. The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the charge transport layer or undercoat layer described below. Specific organic solvents include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, N,N-dimethylformamide,
Amides such as N,N-dimethylacetamide,
Sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogens such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichloroethylene. Hydrocarbons or aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used. Coating can be carried out using coating methods such as dip coating, spray coating, spinner coating, bead coating, Meyer bar coating, blade coating, roller coating, and curtain coating. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying at a temperature of 30℃ to 200℃ for 5 minutes to 2
It can be carried out stationary or under blown air for a period of time. The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. ing. At this time, this charge transport layer may be laminated on or under the charge generation layer. However, if the charge generation layer is the uppermost layer, the coating may be scratched during repeated use, causing a change in sensitivity, so it is desirable that the charge transport layer be laminated on the charge generation layer. The substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as charge transport substance) is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. The term "electromagnetic waves" used herein includes a broad definition of "light rays" that includes gamma rays, x-rays, ultraviolet rays, visible light, near-infrared rays, infrared rays, far-infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps that of the charge generation layer, charge carriers generated in both trap each other, resulting in a decrease in sensitivity. Charge transport substances include electron transport substances and hole transport substances, and electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, and 2,4,7-trinitro-9-fluorenone. , 2, 4, 5, 7-
Tetranitro-9-fluorenone, 2,4,7-
trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone,
Examples include electron-withdrawing substances such as 2,4,8-trinitrothioxanthone, and polymerization of these electron-withdrawing substances. Examples of hole-transporting substances include pyrene, N-ethylcarbazole, N-isopropylcarbazole,
N-Methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-
3-methylidene-10-ethylphenothiazine,
N,N-diphenylhydrazino-3-methylidene-10-ethylphenoxazine, P-diethylaminobenzaldehyde-N,N-diphenylhydrazone, P-diethylaminobenzaldehyde-N
-α-Naphthyl-N-phenylhydrazone, P-
Pyrrolidinobenzaldehyde-N,N-diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N,N-diphenylhydrazone, P-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone hydrazones such as 2,5-bis(P-diethylaminophenyl)-1,3,4-oxadiazole, 1
-Phenyl-3-(P-diethylaminostyryl)
-5-(P-diethylaminophenyl)pyrazoline, 1-[quinolyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]- 3-(P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[6-methoxy-pyridyl(2)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1- [Pyridyl(3)]-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[Lepidyl(2)]-3-(P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-
3-(P-diethylaminostyryl)-4-methyl-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(α-methyl-P-
diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-phenyl-3-
(P-diethylaminostyryl)-4-methyl-5
-(P-diethylaminophenyl)pyrazoline,
1-Phenyl-3-(α-benzyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, spiropyrazoline and other pyrazolines, 2-(P-diethylaminostyryl)
-6-diethylaminobenzoxazole, 2-
Oxazole compounds such as (P-diethylaminophenyl)-4-(P-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2
Thiazole compounds such as -(P-diethylaminostyryl)-6-diethylaminobenzothiazole, triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane, 1,1-bis(4-N,N -diethylamino-2-methylphenyl)heptane, 1,
Polyarylalkanes such as 1,2,2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, triphenylamine, poly-
N-pinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine,
Examples include poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, and ethylcarbazole formaldehyde resin. In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium amorphous silicon, and cadmium sulfide can also be used. Moreover, these charge transport substances may be one or two types.
More than one species can be used in combination. When the charge transport material does not have film-forming properties,
A film can be formed by selecting an appropriate binder. Resins that can be used as binders are:
For example, insulating resins such as acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, polysulfone, polyacrylamide, polyamide, chlorinated rubber, or poly-N- Mention may be made of organic photoconductive polymers such as vinylcarbazole, polyvinylanthracene, polyvinylpyrene. Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Generally, it is 5-30μ, but the preferred range is 8-20μ. When forming the charge transport layer by coating, an appropriate coating method as described above can be used. A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. As the substrate having a conductive layer, materials that are themselves conductive can be used, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum. In addition, plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic, resin, polyethylene fluoride, etc.), conductive particles (e.g. carbon black,
A substrate made of plastic coated with silver particles (silver particles, etc.) together with a suitable binder, a substrate made of plastic or paper impregnated with conductive particles, a plastic containing a conductive polymer, etc. can be used. A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer. The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon
610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. The thickness of the undercoat layer is 0.1 to 5μ, preferably 0.5 to 3μ.
is appropriate. When using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, and the charge transport material is an electron transport material, the surface of the charge transport layer must be positively charged, and when exposed to light after charging, In the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer, and the positive charges that have subsequently reached the surface are neutralized, the surface potential is attenuated, and an electrostatic contrast is generated between the exposed area and the unexposed area. A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. Either fix this directly, or transfer the toner image to paper or plastic film, etc.
It can be developed and fixed. Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or known methods, and are not limited to specific ones. On the other hand, when the charge transport material consists of a hole transport material, the surface of the charge transport layer must be negatively charged.
After charging, when exposed to light, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer, and then reach the surface and neutralize the negative charge, causing a decrease in the surface potential and static electricity between the exposed area and the unexposed area. Electrocontrast occurs. During development, it is necessary to use a positively charged toner, contrary to the case where an electron transporting substance is used. Furthermore, it is also possible to form a single-layer type photoreceptor in which malotropocyanine is dispersed in the binder resin. In another specific example of the present invention, organic photoconductive materials such as the aforementioned hydrazones, pyrazolines, oxazoles, thiazoles, triarylmethanes, polyarylalkanes, triphenylamines, poly-N-vinylcarbazoles, etc. The photosensitive film may contain the above-mentioned malotropocyanine as a sensitizer for photoconductive substances and inorganic photoconductive substances such as zinc oxide, cadmium sulfide, and selenium. This photosensitive film is formed by coating these photoconductive substances and the above-mentioned malotropocyanine compound together with a binder. Further, as another specific example of the present invention, JP-A-49-
It can also be used as a type of photoreceptor in which a charge generating material is dispersed in a charge transfer complex as disclosed in Japanese Patent No. 91648 (photoconductive member). Each photoreceptor contains at least one type of malotropocyanin selected from the compounds represented by the general formula [], and if necessary, other photoconductive pigments or dyes with different light absorptions are used in combination. In particular, it is possible to increase the sensitivity of this photoreceptor or to prepare it as a panchromatic photoreceptor. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines but also for laser beam printers,
It can also be widely used in electrophotographic applications such as LED printers and CRT printers. Hereinafter, the present invention will be explained according to examples. Examples 1 to 11 Ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 ml of water) on an aluminum plate
was applied with a Mayer bar so that the film thickness after drying was 1.0μ, and dried. Next, 11 types of coating liquids were prepared by adding 5 g of each of the 11 types of malotropocyanins listed in the table below to a solution of 2 g of butyral resin (butyralization degree: 63 mol %) dissolved in 95 ml of isopropyl alcohol. After dispersing each coating solution in a sand mill for 5 hours, each coating solution was applied onto the casein undercoat layer using a Mayer bar so that the dry film thickness was 0.1μ, and dried to form a charge generation layer. Ta. Then, the structural formula 5 g of hydrazone compound and 5 g of polymethyl methacrylate resin (number average molecular weight 100,000) were dissolved in 70 ml of benzene, and this was applied onto the charge generation layer using a Mayer bar so that the film thickness after drying was 12 μm.
It was dried to form a charge transport layer. Eleven types of electrophotographic photoreceptors prepared in this way were tested using an electrostatic copying paper tester MOdelSP-422 manufactured by Kawaguchi Electric Co., Ltd.
The sample was statically charged with a corona at -5KV using a 1000V, held in a dark place for 1 second, and then exposed to light for 4 seconds at an illuminance of 51ux to examine the charging characteristics. As for the charging characteristics, the initial charging potential (V ₀ ) and the exposure amount (E1/2) required to attenuate the potential to 1/2 of the potential when dark decaying for 1 second were measured. The results are shown in Table 1. Also, the residual potential after 20lux・sec exposure
Expressed in _VR .

[Table] Example 12 Polyester resin (manufactured by Toyobo Co., Ltd., Vylon
200) 5g and 1-[pyridyl-(2)]-3-(4-N,
N-diethylaminostyryl)-5-(4-N,N
- Diethylaminophenyl) pyrazoline (5 g) was dissolved in 80 ml of methyl ethyl ketone, 1.0 g of the above-mentioned malotropocyanin No. 2 was added and dispersed, and the coating was applied onto an aluminum-deposited polyester film and dried to form a photosensitive layer with a dry film thickness of 13 μm. A photoreceptor with the following characteristics was created. The characteristics of this photoreceptor were determined by using the same method as in Example 1 to determine the initial charging potential (V ₀ ) and the exposure amount (E _{1/ 2} ) was measured, and the results were as follows. However, the charging polarity was determined. V ₀ : +580V E _1/2 : 5.0lux·sec Example 13 1 g of poly-N-vinylcarbazole and 5 mg of the aforementioned malotropocyanin No. 3 were added to 10 g of 1,2-dichloroethane, and then thoroughly stirred. The coating solution prepared in this way was applied to a polyethylene terephthalate film deposited with aluminum to a dry film thickness.
It was applied with a doctor blade to a thickness of 15μ. The charging characteristics of this photoreceptor were measured in the same manner as in Example 1. However, the charging polarity was determined.
The results are shown below. V ₀ : +560V E _1/2 : 4.1lux・sec Example 14 Malotropocyanin No. 10 was used in place of malotropocyanin No. 3 used when preparing the electron photoreceptor of Example 13. After preparing a photoreceptor in exactly the same manner as in Examples, the charging characteristics of this photoreceptor were measured. The results are shown below. However, the charging polarity was taken into account. V ₀ : +570V E _1/2 : 4.81ux・sec Example 15 Particulate zinc oxide (Sazex2000 manufactured by Sakai Chemical Co., Ltd.) 10
g, 4 g of acrylic resin (Dyanal LR009 manufactured by Mitsubishi Rayon Co., Ltd.), 10 g of toluene, and 10 mg of the above-mentioned malotropocyanin No. 1 were thoroughly mixed in a ball mill, and the resulting coating solution was deposited with aluminum. It was applied onto a polyethylene terephthalate film using a doctor blade to a dry film thickness of 21 μm, and dried to prepare an electrophotographic photoreceptor. When the spectral sensitivity of this electrophotographic photoreceptor was measured using spectrophotography using electrophotography, it was found that the photoreceptor of this example showed sensitivity on the longer wavelength side compared to the aforementioned zinc oxide coating that did not contain malotropocyanin. It turned out that it has. Example 16 A polyvinyl alcohol film having a thickness of 1.1 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. Next, a coating solution containing the same malotropocyanin as in Example 3 was applied onto the previously formed polyvinyl alcohol layer using a Mayer bar so that the coating thickness after drying was 0.1μ, dried, and charged. A shipping layer was formed. Then, the structural formula A solution prepared by dissolving 5 g of pyrazoline compound and 5 g of polyarylate resin (condensation polymer of bisphenol A and terephthalic acid-isophthalic acid) in 70 ml of tetradrofuran is placed on the charge generation layer so that the film thickness after drying is 10 μm.
It was coated and dried to form a charge transport layer. The charging characteristics of the photoreceptor thus prepared were measured in the same manner as in the examples. The results are shown below. V ₀ : −590V E _1/2 : 3.21 lux·sec Example 17 An ammonia aqueous solution of casein was coated on an aluminum plate with a thickness of 100 μm and dried to form a subbing layer with a thickness of 1.1 μm. Next, 5 g of 2,4,7-trinitro-9-fluorenone and 5 g of poly-N-vinylcarbazole (number average molecular weight 300,000) were added to 70 ml of tetrahydrofuran.
to form a charge transfer complex. This charge transfer complex compound and the aforementioned malotropocyanine compound No. 31 g were added to a solution in which 5 g of polyester resin (Vylon, manufactured by Toyobo) was dissolved in 70 ml of tetrahydrofuran, and dispersed. This dispersion was applied onto the undercoat layer so that the film thickness after drying was 1 μm, and dried.
The charging characteristics of the photoreceptor thus prepared were measured in the same manner as in Example 1. These results were as follows. However, the charging polarity was determined. V ₀ : 550V E _1/2 : 4.81ux・sec

[Brief explanation of drawings]

The absorption spectra of n-hexane solutions of exemplary compounds Nos. 1, 2, and 3 of the malotropocyanine compounds used in the present invention are shown.

Claims (1)

[Scope of Claims] 1. A photoconductive coating containing malotropocyanin represented by the following general formula []. In the formula, n represents an integer of 0, 1 or 2, and R ₁ to
R ₆ represents an alkyl group, an aralkyl group, or an aryl group which may have a substituent, or a residue in which two adjacent groups form a condensed ring with the tropylium ring. 2. An electrophotographic photoreceptor comprising a conductive support and a photosensitive layer having a photoconductive coating containing malotropocyanine represented by the following general formula []. In the formula, n represents an integer of 0, 1 or 2, and R ₁ to
R ₆ represents an alkyl group, an aralkyl group or an aryl group which may have a substituent, or a residue in which two adjacent groups form a condensed ring with the tropylium ring. 3. The photosensitive layer provided on the conductive support comprises at least a charge generation layer and a charge transport layer having a photoconductive coating containing malotropocyanine represented by the general formula [ ] of claim 2. The electrophotographic photoreceptor according to claim 2, which is formed by sequentially laminating layers.