JPH0150903B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to a novel electrophotographic photoreceptor containing a specific trisazo pigment. Conventionally, as electrophotographic photoreceptors made of inorganic photoconductive materials, those using selenium, cadmium sulfide, zinc oxide, etc. have been widely used. On the other hand, as an electrophotographic photoreceptor made of an organic photoconductive substance, poly-
Photoconductive polymers typified by N-vinylcarbazole and low-molecular organic photoconductive substances such as 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, Furthermore, combinations of such organic photoconductive substances and various dyes and pigments are also known. An electrophotographic photoreceptor using an organic photoconductive substance can be easily formed into a film and can be produced by coating, so it can be made into an extremely productive and inexpensive photoreceptor. It also has the advantage of being able to freely control color sensitivity by selecting the sensitizers used, such as dyes and pigments, and has been extensively studied. However, there are problems with sensitivity, durability, etc., and so far only a few have been put into practical use. The present inventors have developed a photoreceptor that is extremely useful for electrophotography by using a novel trisazo pigment represented by general formula (1) (described later) in the photosensitive layer as a pigment used in such an organic electrophotographic photoreceptor. The present invention has been achieved based on the discovery that this can be obtained. A first object of the present invention is to provide a novel electrophotographic photoreceptor containing a specific trisazo pigment, a second object is to provide a highly sensitive electrophotographic photoreceptor, and a third object is to provide a novel electrophotographic photoreceptor containing a specific trisazo pigment. The purpose is to provide a highly durable electrophotographic photoreceptor. General formula (1) is It is indicated by. In the formula, A represents a coupler having aromaticity,
Preferably, A is selected from couplers represented by the following general formulas (2) to (4). General formula (2) is

[Formula], where X is a residue that is fused with a benzene ring to form a naphthalene ring, anthracene ring, carbazole ring, or dibenzofuran ring, Y is -CONR ₁ R ₂ (However, R ₁ is a hydrogen atom, R 2 represents a group selected from the group consisting of substituted or unsubstituted alkyl groups and phenyl groups; R ₂ represents a group selected from the group consisting of substituted or unsubstituted alkyl groups, phenyl groups and naphthyl groups; Substituents for R ₁ and R ₂ groups include methyl,
Alkyl groups such as ethyl, propyl, butyl, halogen atoms, alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, acyl groups such as acetyl and benzoyl, arylthio groups such as methylthio and ethylthio, aryl groups such as phenyl, benzyl, phenethyl Examples include aralkyl groups such as nitro groups, cyano groups, and dialkylamino groups such as dimethylamino and diethylamino. General formulas (3) and (4) are

【formula】

It is represented by [Formula]. In the formula, R ₃ represents a group selected from the group consisting of substituted or unsubstituted alkyl groups and phenyl groups. Specifically, R ₃ is an alkyl group such as methyl, ethyl, propyl, butyl, a hydroxyalkyl group such as hydroxymethyl or hydroxyethyl, an alkoxyalkyl group such as methoxymethyl or ethoxyethyl,
Cyanoalkyl group, aminoalkyl group, N-alkylaminoalkyl group, N,N-dialkylaminoalkyl group, halogenated alkyl group, aralkyl group such as benzyl, phenethyl, phenyl group and substituted phenyl group (substituents include general Examples include R ₁ and R ₂ in formula (2). B ₁ , B ₂ , B ₃ , B ₄ , B ₅ and B ₆ are the same or different, and are hydrogen atoms, halogen atoms such as fluorine, chlorine, bromine, and iodine, and alkyl groups such as methyl, ethyl, propyl, and butyl. , represents an alkoxy group such as methoxy, ethoxy, propoxy, butoxy. The trisazo pigment represented by the general formula (1) has the general formula (In the formula, B ₁ , B ₂ , B ₃ , B ₄ , B ₅ and B ₆ have the same meanings as before.) The triamine represented by the formula is hexazotized by a conventional method, and then the triamine represented by the general formulas (2) to (4) is Couplers having aromatic properties, including couplers represented by the formula (5), are coupled in the presence of an alkali, or the hexazonium salt of the triamine of general formula (5) is isolated in the form of a borofluoride salt or zinc chloride double salt. After that, it is easily produced by coupling with an aromatic coupler in a suitable solvent such as N,N-dimethylformamide or dimethyl sulfoxide in the presence of an alkali. Electrophotographic photoreceptors containing organic pigments on a conductive layer include (1) those in which a layer in which pigments are dispersed in a binder are provided on a conductive layer as disclosed in Japanese Patent Publication No. 52-1667, and (2) those disclosed in Japanese Patent Publication No. 52-1667. Publication No. 47-18545, Japanese Unexamined Patent Publication No. 47-30328
A layer in which a pigment is dispersed in a charge transport medium consisting of a charge transport material or the material and an insulating binder (the binder itself may be a charge transport material) as disclosed in the official gazette is provided on a conductive layer. ,
(3) those consisting of a conductive layer, a charge generation layer containing an organic pigment, and a charge transport layer as disclosed in JP-A-49-105537; (4) as disclosed in JP-A-49-91648; There are charge transfer complexes in which organic pigments are added. The electrophotographic photoreceptor of the present invention is characterized by containing a trisazo pigment represented by the general formula (1), and is useful as any of the types of electrophotographic photoreceptors described above. In order to increase the transport efficiency of charge carriers generated by light absorption of the trisazo pigment shown in (2), (3), and (4), it is desirable to use it as a photoreceptor. Further, type (3) photoreceptor in which the charge carrier generation function and the charge carrier transport function are separated is most desirable in order to take advantage of the characteristics of the pigment. Therefore, the (3) type electrophotographic photoreceptor will be explained. As for the layer structure, a conductive layer, a charge generation layer, and a charge transport layer are essential, and the charge generation layer may be either above or below the charge transport layer, but in an electrophotographic photoreceptor of the type that is used repeatedly. ,
An adhesive layer may be provided as necessary for the purpose of improving adhesion with the conductive layer, charge generation layer, and charge transport layer mainly from the viewpoint of physical strength and in some cases from the viewpoint of chargeability. As the conductive layer, a metal plate or metal foil such as aluminum, a plastic film on which metal such as aluminum is vapor-deposited or aluminum foil laminated with paper, paper subjected to conductive treatment, etc. are used. Effective materials for the adhesive layer include resins such as casein, polyvinyl alcohol, water-soluble polyethylene, and nitrocellulose. Adhesive layer thickness is 0.1
-5μ, preferably 0.5-3μ is suitable. After the trisazo pigment represented by the general formula (1) is made into fine particles on the conductive layer or the adhesive layer applied to the conductive layer, it is dispersed without a binder or in an appropriate binder solution if necessary, and then applied and dried. and set it up. When dispersing the trisazo pigment, known methods such as ball milling and attritor can be used, and the pigment particles are 5μ or less, preferably 2μ or less,
Optimally, it is desirable to set it to 0.5μ or less. The trisazo pigment can also be applied by dissolving it in an amine solvent such as ethylenediamine. Conventional methods such as blade, Mayer bar, spray, and dipping methods are used for application. The thickness of the charge generation layer is 5μ or less, preferably 0.01~
1μ is desirable. When using a binder in the charge generation layer, a large amount of binder will affect sensitivity, so the ratio of binder in the charge generation layer should be 80%.
% or less, preferably 40% or less. Binders used include polyvinyl butyral, polyvinyl acetate, polyester, polycarbonate, phenoxy resin, acrylic resin,
Polyacrylamide, polyamide, polyvinylpyridine resin, cellulose resin, urethane resin,
Various resins such as epoxy resin, casein, and polyvinyl alcohol are used. A charge transport layer is provided on the charge generation layer provided in this manner. If the charge transport material does not have a film-forming ability, a charge transport layer is formed by applying a solution prepared by dissolving a binder in a suitable solvent and drying it by a conventional method. Charge transport materials include electron transport materials and hole transport materials. Examples of electron transporting substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9
-Fluorenone, 2,4,7-trinitro-9-
Dicyanomethylene fluorenone, 2,4,5,7
There are electron-withdrawing substances such as -tetranitroxanthone and 2,4,8-trinitrothioxanthone, and polymerized products of these electron-withdrawing substances. Examples of hole-transporting substances include pyrene, N-ethylcarbazole, N-isopropylcarbazole,
Hydrazones such as N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, 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
-Pyrazolines such as (p-diethylaminophenyl)pyrazoline, 2-(p-diethylaminostyryl)-6-diethylaminobenzoxazole, 2-(p-diethylaminophenyl)-4-
Oxazole compounds such as (p-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, 2-(p-diethylaminostyryl)-
Thiazole compounds such as 6-diethylaminobenzothiazole, bis(4-diethylamino-2-
(methylphenyl)-triarylmethane compounds such as phenylmethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene,
Examples include polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, and ethylcarbazole formaldehyde resin. The charge transport material is not limited to those described here, and when used, one type or a mixture of two or more types of charge transport substances can be used. However, when a charge-transporting substance and a hole-transporting substance are mixed, charge transfer absorption occurs in the visible region.
Even when exposed to light, the light may not reach the charge generation layer below the charge transport layer. The thickness of the charge transport layer is 5 to 30μ, preferably 8 to 30μ.
It is 20μ. As the binder, acrylic resin, polystyrene, polyester, polycarbonate, etc. can be used. As the binder for the low-molecular hole-transporting substance, a hole-transporting polymer such as the aforementioned poly-N-vinylcarbazole can be used as the binder. On the other hand, as a binder for a low-molecular electron-transporting substance, a polymer of an electron-transporting monomer as described in US Pat. No. 4,122,213 can be used. When using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, if the charge transport material is an electron transport material, the surface of the charge transport layer must be positively charged, and after charging When exposed to light, electrons generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the surface and neutralize the positive charge, resulting in attenuation of the surface potential and an electrostatic contrast between it and the unexposed area. arise. A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. This can be directly fixed, or the toner image can be transferred to paper, plastic film, etc. and then 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 one or any known method, and are not limited to specific ones. On the other hand, when the charge transport material is made 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. Produces electrical contrast. During development, it is necessary to use a positively charged toner, contrary to the case where an electron transporting substance is used. The (1) type photoreceptor is produced by adding the trisazo pigment represented by the general formula (1) to an insulating binder solution, such as that used for the charge transport layer of the (3) type photoreceptor, and dispersing it onto a conductive support. Obtained by coating and drying. The (2) type photoreceptor is made by dissolving the charge transport material of the (3) type photoreceptor and an insulating binder such as that used in the charge transport layer in an appropriate solvent, and then using the trisazo pigment represented by the general formula (1). After adding and dispersing, it is obtained by coating and drying on a conductive support. (4) type photoreceptor forms a charge transfer complex when the electron transport material and hole transport material described in type (3) photoreceptor are combined, so a solution of the charge transfer complex is added to the general formula (1). ) is added and dispersed, then coated on a conductive support and dried. The pigment used in both photoreceptors has the general formula
Contains at least one type of pigment selected from the trisazo pigments shown in (1), and if necessary, pigments with different light absorptions can be combined to increase the sensitivity of the photoreceptor used or to create a panchromatic photoreceptor. The trisazo pigment represented by the general formula (1) is used to obtain 2
It is also possible to use a combination of more than one kind, or a combination with a charge generating material selected from known dyes and pigments. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers,
It can also be widely used in electrophotographic applications such as CRT printers. Next, a synthesis example of the trisazo pigment used in the present invention will be specifically explained. Synthesis example below pigment 3,4,5-tri(p-aminophenyl)-
1,2,4-triazole 5.48g (0.016mol),
After cooling a dispersion of 14 ml (0.158 mol) of concentrated hydrochloric acid and 100 ml of water to 4°C, 3.48 g of sodium nitrite was added.
(0.0504 mol) dissolved in 10 ml of water was added dropwise over 7 minutes, then stirring was continued for 30 minutes while keeping the temperature of the solution at 4 to 7°C, and activated carbon was added and filtered to obtain an aqueous hexazonium salt solution. Next, in 560 ml of water, add 21 g (0.528 mol) of sodium hydroxide and 2-hydroxy-3-naphthoic acid anilide.
Dissolve 13.9g (0.0528mol) and add this solution to 5 to 10
The hexazonium salt aqueous solution synthesized above was added dropwise over 30 minutes while stirring at a temperature of 0.degree. C., stirring was continued for an additional hour, and then left overnight at room temperature. The pigment obtained by filtering the reaction solution was washed with water, acetone, and dried to obtain 17.02 g of a crude pigment. Next, the mixture was washed successively with DMF and terahydrofuran, and then dried to obtain 13.50 g of red pigment.
Accurate yield of triamine base 72.4% Decomposition point 300℃ or higher Elemental analysis Molecular formula C ₇₁ H ₄₈ N ₁₂ O ₆・ Calculated value % Analyzed value % C 73.17 72.98 H 4.16 4.12 N 14.43 14.39 1R absorption spectrum Secondary amide 1670 cm ^-1 or higher The method for synthesizing pigment No. 1 was described above, but other trisazo pigments represented by general formula (1) can be synthesized in the same manner. Next, examples will be shown regarding electrophotographic photoreceptors using the trisazo pigment of the present invention. Examples 1 to 15 A polyvinyl alcohol aqueous solution was applied onto an aluminum plate having a thickness of 100 μm and dried to form an adhesive layer with a coating weight of 0.8 g/m ² . Next, 5 g each of the No. 1 pigment and each of the pigments shown in the table below and a polyester resin solution (Polyester Adhesive 49000 manufactured by DuPont, solid content 20
%) and 80 ml of tetrahydrofuran were dispersed and coated on the adhesive layer, and the coating amount after drying was 0.20 g/m ² . Next, p-diethylaminobenzaldehyde-
5 g of N,N-diphenylhydrazone and 5 g of polymethyl methacrylate resin (number average molecular weight 100,000) were dissolved in 70 ml of tetrahydrofuran and coated on the charge generation layer, with a coating weight of 10 g/m ² after drying. . The electrophotographic photoreceptor thus prepared was statically charged with corona at 5KV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd.
After holding it in a dark place for 10 seconds, it was exposed to light at an illuminance of 5 lux to examine the charging characteristics. The initial potential is Vo (V), the potential retention rate for 10 seconds in the dark is Rv (%), and the half-decay exposure amount is E1/2 (lux.sec).
The charging characteristics of each photoreceptor were investigated and the results are shown in the table below.

【table】

【table】

【table】

【table】

【table】

[Table] Example 16 On the charge generation layer prepared in Example 1, 2, 4,
5g of 7-trinitrofluorenone and poly-4,
Dissolve 5 g of 4'-dioxydiphenyl-2,2-propane carbonate (viscosity average molecular weight 30,000) in 70 ml of tetrahydrofuran, and calculate the coating amount after drying.
It was set to 12g/ ^m2 . Charge measurement was carried out in the same manner as in Example 1, and the characteristic values were as follows. However, the charging polarity was determined. Vo515V, Rv85%, E1/216.2lux.sec. Example 17 After dispersing 5 g of pigment No. 14 used in Example 14 and 2 g of butyral resin (degree of butyralization 63 mol%) in 95 ml of ethanol. , was applied to the aluminum surface of an aluminum vapor-deposited mylar film, and the coating amount after drying was 0.2 g/m ² . Next, 2,5-bis(p-diethylaminophenyl)-1,3,4
A solution obtained by dissolving 5 g of oxadiazole and 5 g of phenoxy resin (Bakelite PKH H manufactured by UCC) in 70 ml of tetrahydrofuran was applied to the charge generation layer and dried to form a charge transport layer with a coating weight of 11 g/m ² . The produced photoreceptor was subjected to charge measurement in the same manner as in Example 1. Characteristic values, Vo535V, Rv90%, E1/28.7lux.sec Example 18 An ammonia aqueous solution of casein was coated on an aluminum plate with a thickness of 100μ and dried to form an adhesive layer with a coating weight of 1.0g/m ² . Next, 2-(p-diethylaminophenyl)-4-(p-dimethylaminophenyl)
-5-(2-chlorophenyl)oxazole 5g
1.0 g of No. 8 pigment used in Example 8 was added to a solution in which 5 g of poly-N-vinylcarbazole (number average molecular weight 300,000) were dissolved in 70 ml of tetrahydrofuran.
After dispersion, apply on the above adhesive layer and dry, with a coating amount of 12
g/ ^m2 . The charge on the photoreceptor was measured in the same manner as in Example 1.
However, the charging polarity was determined. Characteristic values Vo520V, Rv89%, E1/214.2lux.
sec Example 19 5 g of 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline and poly-2,2-propane bis(4
-phenylisophthalic acid-terephthalic acid ester), (isophthalic acid, terephthalic acid molar ratio 1:
1) After dissolving 5 g in 70 ml of tetrahydrofuran, 1.0 g of No. 1 pigment was added, and after dispersion, it was applied and dried on the adhesive layer used in Example 18, and the coating amount was 12 g/m ²
And so. The charge of the photoreceptor was measured, and the characteristic values were as follows. However, the charging polarity was determined. Vo510V, Rv89%, E1/218.2lux.sec. Example 20 The charge transport material of Example 1 was used as 1-[quinolyl (2)]
-3-(p-diethylaminostyryl)-5-
A photoreceptor was prepared in exactly the same manner as in Example 1 except that (p-diethylaminophenyl)-pyrazoline was used. Next, using the same charge measuring device as in Example 1, the initial dark potential (V _D ) was 500 V and the light/dark potential (V _L ) was
Charging and exposure conditions were set so that the voltage was 30V, charging and exposure were repeated under the same conditions, and the cycle stability of V _D and V _L was examined, and the results were as follows. Number of measurements (times) V _D (V) V _L (V) 1 500 30 5000 505 38 10000 490 45 As is clear from the above results, the electrophotographic photoreceptor of the present invention is a photoreceptor with extremely excellent potential stability. .

Claims (1)

[Claims] 1. General formula (In the formula, A represents a coupler having aromaticity, and B ₁ , B ₂ , B ₃ , B ₄ , B ₅ and B ₆ are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group, and an alkoxy group. 1. An electrophotographic photoreceptor comprising a trisazo pigment represented by (). 2 In the trisazo pigment represented by the general formula (1), A has the general formula −CONR ₁ R ₂ (However, R ₁ is a hydrogen atom,
a group selected from the group consisting of substituted or unsubstituted alkyl groups and phenyl groups, R ₂ represents a group selected from the group consisting of substituted or unsubstituted alkyl groups, phenyl groups and naphthyl groups)] An electrophotographic photoreceptor according to claim 1. 3 In the trisazo pigment represented by the general formula (1), A is the general formula [formula] or [formula] (in the formula (3) or (4), R ₃ is a group consisting of a substituted or unsubstituted alkyl group and a phenyl group) The electrophotographic photoreceptor according to claim 1, which represents a group selected from the following. 4. The electrophotographic photoreceptor according to claim 1, comprising at least three layers: a conductive layer, a charge generation layer containing a trisazo pigment represented by general formula (1), and a charge transport layer.