JPH0157781B2 - - 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, electrophotographic photoreceptors made of organic photoconductive substances include photoconductive polymers typified by poly-N-vinylcarbazole and 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadi Those using low-molecular-weight organic photoconductive substances such as azoles, and furthermore those in which such organic photoconductive substances are combined with various dyes and pigments are known. An electrophotographic photoreceptor using an organic photoconductive substance has good film-forming properties and can be easily produced by coating, so it can be 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 to practical use. The present inventors have repeatedly researched pigments used in such organic electrophotographic photoreceptors, and discovered that by using a specific trisazo pigment in the photosensitive layer, a photoreceptor that is extremely useful in electrophotography can be obtained.
This has led to the present invention. The first object of the present invention is to provide a novel electrophotographic photoreceptor containing a specific trisazo pigment, the second object is to provide a highly sensitive electrophotographic photoreceptor, and the third object is to provide a novel electrophotographic photoreceptor containing a specific trisazo pigment. The objective is to provide a highly durable electrophotographic photoreceptor. The particular trisazo pigment in the present invention has the general formula It is indicated by. In the formula, A represents an aromatic coupler, and it is preferable that A is selected from couplers represented by the following general formulas (2) to (4). General formula (2) is

[Formula], where X is a residue condensed with a benzene ring to form a naphthalene ring, anthracene ring, carbazole ring or dibenzofuran ring, and Y is -CONR ₁ R ₂ (However, R ₁ is a hydrogen atom, a substituted or a group selected from the group consisting of 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 the R ₁ and R ₂ groups include alkyl groups such as methyl, 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, aralkyl groups such as benzyl and phenethyl, nitro groups, cyano groups , dialkylamino groups such as dimethylamino and diethylamino. General formulas (3) and (4) are

【formula】

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, _R3 is methyl, ethyl, propyl,
Alkyl groups such as butyl, hydroxyalkyl groups such as hydroxymethyl and hydroxyethyl, alkoxyalkyl groups such as methoxymethyl and ethoxyethyl, cyanoalkyl groups, aminoalkyl groups, N
-alkylaminoalkyl group, N,N-dialkylamino group, halogenated alkyl group, benzyl,
Aralkyl groups such as phenethyl, phenyl groups and substituted phenyl groups (substituents include general formula (2))
Examples include R ₁ and R ₂ ). In the general formula (1), B ₁ , B ₂ , B ₃ and B ₄ are the same or different, and are hydrogen atoms, halogen atoms consisting of fluorine, chlorine, bromine and iodine, and alkyl groups such as methyl, ethyl, propyl and butyl. , methoxy, ethoxy, propoxy, butoxy and other alkoxy groups, cyano groups, and trifluoromethyl groups. The trisazo pigment represented by the general formula (1) is a starting material compound of the general formula (In the formula, B ₁ , B ₂ , B ₃ and B ₄ have the same meanings as before) is tetrazotized by a conventional method, and then an aromatic aromatic product containing a coupler represented by general formulas (2) to (4) Either the tetrazonium salt of the diamine of general formula (5) is isolated in the form of a borofluoride salt or a zinc chloride salt and then coupled with a family coupler in the presence of an alkali, or a suitable solvent such as N,N-
It can be easily produced by coupling with an aromatic coupler in the presence of an alkali in a solvent such as dimethylformamide or dimethylsulfoxide. Photoreceptors containing organic pigments on a conductive layer include (1) those in which a layer in which a pigment is dispersed in a binder (insulating) is provided on a conductive layer, as disclosed in Japanese Patent Publication No. 52-1667, (2) In a charge transporting material as disclosed in Japanese Patent Publication No. 47-18545 and Japanese Patent Application Laid-open No. 47-30328, or a charge transporting medium consisting of the material and an insulating binder (the binder itself may be a charge transporting material). A layer in which a pigment is dispersed is provided on a conductive layer, (3) A layer 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 ) There are various types, such as one in which an organic pigment is added to a charge transfer complex as disclosed in JP-A No. 49-91648. The electrophotographic photoreceptor of the present invention is characterized by containing a trisazo pigment represented by the general formula (1), and can be used as the above type of electrophotographic photoreceptor. In order to increase the transport efficiency of charge carriers generated by light absorption of the trisazo pigment shown, it is desirable to use it as a photoreceptor of types (2), (3) and (4). Furthermore, we separated the charge carrier generation mechanism and transport function.
(3) type photoreceptor is the most desirable in terms of taking advantage of the characteristics of the pigment. Therefore, this (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 a 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 general formula (1) is made into fine particles on the conductive layer or the adhesive layer applied to the conductive layer, it is applied without a binder or, if necessary, dispersed in an appropriate binder solution. Dry and set aside. When dispersing the trisazo pigment, known methods such as ball milling and attritor can be used, and it is desirable that the pigment particles have a size of 5μ or less, preferably 2μ or less, and optimally 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 the sensitivity, so the proportion of the binder in the charge generation layer should be 80% or less, preferably 40%.
% or less is desirable. 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 thus provided. 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. As the hole transport substance, pyrene, N-ethylcarbazole, N-isopropylcarbazole, N
- hydrazones such as 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-(p
pyrazolines such as -diethylaminophenyl)pyrazoline, 2-(p-diethylaminostyryl)
-6-diethylaminobenzoxazole, 2-
Oxazole compounds such as (p-diethylaminophenyl)-4-(p-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole,
Thiazole compounds such as 2-(p-diethylaminostyryl)-6-diethylaminobenzothiazole, triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane, triphenylamine, poly-N-vinylcarbazole , polyvinylpyrene, polyvinylanthracene, polyvinyl acridine, poly-
Examples include 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 an electron-transporting substance and a hole-transporting substance are mixed, charge transfer absorption occurs in the visible region, and 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 weight electron transporting substance, a polymer of an electron transporting monomer as described in USP 412213 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, and the charge transport material is an electron transport material, the surface of the charge transport layer must be positively charged, and exposure after charging is required. Then, in the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface and neutralize the positive charge, causing a decrease in surface potential and creating an electrostatic contrast with the unexposed area. . A visible image is 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, and then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or methods, 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, and when exposed to light after charging, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. , which then reaches the surface and neutralizes the negative charges, resulting in attenuation of the surface potential and an electrostatic contrast between the surface potential and the unexposed area. 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. (2) type photoreceptor After dissolving an insulating binder such as that used in the charge transport layer of the charge transport material of the (3) type photoreceptor in a suitable solvent, the trisazo pigment represented by the general formula (1) is added. After addition, it is obtained by dispersing, 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, dispersed, and then applied and dried on a conductive support. In any of the photoreceptors, the trisazo pigment used contains at least one type of pigment selected from the trisazo pigments represented by the general formula (1), and if necessary, pigments with different light absorptions are used in combination. A combination of two or more types of trisazo pigments represented by the general formula (1) for the purpose of increasing the sensitivity of the photoreceptor or obtaining a panchromatic photoreceptor, or a combination with a charge-generating material selected from known dyes and pigments. It is also possible to use The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers and CRTs.
It can also be widely used in electrophotographic applications such as printers. Next, a synthesis example of the trisazo pigment used in the present invention will be specifically explained. Synthesis example: The following pigment (referred to as pigment No. 1) After cooling a dispersion of 6.37 g (0.03 mol) of 4,4'-diaminoazobenzene, 13.24 ml (0.15 mol) of concentrated hydrochloric acid, and 102 ml of water to 4°C, sodium nitrite was added.
4.35g (0.063mol) dissolved in 13ml of water
The mixture was added dropwise over a period of minutes, and then stirring was continued for 30 minutes while keeping the liquid temperature at 4 to 7°C. Next, 26.71 g (0.252 mol) of soda carbonate and 14.32 g (0.063 mol) of N-methyl-4-hydroxynaphthalimide were dissolved in 600 ml of water.
While maintaining the temperature at ~10°C, the previously synthesized tetrazonium salt aqueous solution was added dropwise over 30 minutes, 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, washed with acetone, and dried to obtain 17.77 g of a crude pigment. Next, the mixture was washed successively with DMF and THF, and then dried to obtain 14.46 g of a purple pigment. Diamine-based precision yield 70% Decomposition point 300℃ or above Fractional analysis Molecular formula C ₃₈ H ₂₄ N ₈ O ₆ Calculated value% Analytical value% C 66.27 66.30 H 3.52 3.42 N 16.27 16.24 IR absorption spectrum Imide 1655cm ^-1 , 1695cm ^{- 1} or more, we have described the synthesis of No. 1 pigments, but the general formula
Other trisazo pigments shown in (1) are also synthesized in the same manner. Next, examples of the present invention will be shown. Examples 1 to 20 An aqueous polyvinyl alcohol 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 of the above-mentioned No. 1 pigment or each pigment described below, 10 g of polyester resin solution (Polyester Adhesive 49000 manufactured by DuPont, solid content 20%), and 80 ml of tetrahydrofuran were dispersed and applied on the adhesive layer, and after drying. The coating amount 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 Modelsp-428 manufactured by Kawaguchi Electric Co., Ltd., held in a dark place for 10 seconds, and then exposed at an illuminance of 5lux. The charging characteristics were investigated. 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 are shown below.

【table】

【table】

【table】

【table】

【table】

【table】

[Table] Example 21 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. Vo500V, Rv87%,
E1/217.3lux.sec. Example 22 5 g of No. 14 pigment used in Example 14 and 2 g of butyral resin (degree of butyralization 63 mol%) were mixed with ethanol.
After dispersing with a solution dissolved in 95 ml, it 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, 5 g of 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole and 5 g of phenoxy resin (Bakelite PKHH manufactured by UCC)
A solution obtained by dissolving 1.5 g of 1.0 g in 70 ml of tetrahydrofuran was applied onto the charge generation layer and dried to form a charge transport layer with a coating weight of 11 g/m ² . The charging characteristics of the photoreceptor thus prepared are shown below. Vo530V, Rv91%,
E1/27.2lux.sec. Example 23 An ammonia aqueous solution of casein was coated on an aluminum plate with a thickness of 100 μm and dried to form an adhesive layer with a coating weight of 1.0 g/m ² . Next, 2-(p-diethylaminophenyl)-4
-(p-dimethylaminophenyl)-5-(2-
5g of chlorphenyl oxazole and poly-N-
1.0 g of pigment No. 2 used in Example 2 was added to a solution of vinyl carbazole (number average molecular weight 300,000) dissolved in 70 ml of tetrahydrofuran, and after dispersion, it was applied on the adhesive layer and dried to give a coating amount of 12 g/m It was set to ² . The charging characteristics of the photoreceptor produced are shown. However, the charging polarity was determined. Vo510V, Rv88%, E1/213.8lux.sec. Example 24 1-Phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)-
5 g of pyrazoline and 5 g of poly-2,2-propane bis(4-phenylisophthalic acid-terephthalic acid coester) (molar ratio of isophthalic acid and terephthalic acid 1:1) were dissolved in 70 ml of tetrahydrofuran and used in Example 1. Add 1.0g of No.1 pigment,
After dispersion, it was coated on the adhesive layer used in Example 22 and dried, giving a coating weight of 12 g/m ² . The charging characteristics of the produced photoreceptor are shown, however, the charging polarity is not included. Vo500V, Rv90%, E1/216.4lux.sec. Example 25 The charge transport material of Example 1 was mixed with 1-[(2)-quinolyl]-3-(p-diethylaminostyryl)-5
A photoreceptor was prepared in the same manner as in Example 1 except that the binder used in Example 21 was used as the charge transport layer binder in place of -(p-diethylaminophenyl)-pyrazoline. Next, using the same charging characteristic measuring equipment as in Example 1, charging and exposure conditions were set so that the initial dark potential (Vo) was 500 V and the light potential (V _L ) was 30 V. Repeated charging and exposure,
We investigated the cycle stability of Vo.V _L and present the results. Number of measurements Vo V _L (times) (V) (V) 1 500 30 5000 490 35 10000 480 40 As is clear from this, this photoreceptor has extremely excellent potential stability.

Claims (1)

[Claims] 1. General formula (In the formula, A represents a coupler having aromatic property, and B ₁ , B ₂ , B ₃ and B ₄ are the same or different,
An electrophotographic photoreceptor comprising a trisazo pigment represented by a group selected from a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a trifluoromethyl group. 2 In the trisazo pigment represented by the general formula (1), A is represented by the general formula is −CONR ₁ R ₂ (However, R ₁ is
a group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, and a phenyl group; _R2 represents a group selected from the group consisting of a substituted or unsubstituted alkyl group, phenyl group, and naphthyl group) ] The 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 general formula (3) or (4), R ₃ consists of a substituted or unsubstituted alkyl group and a phenyl group) The electrophotographic photoreceptor according to claim 1, which is a group selected from the group consisting of: 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.