JPH0150902B2 - - 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, 2,5-bis(p-diethylaminophenyl)-1,3,4-oxa Those using low-molecular organic photoconductive substances such as diazole, and 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 produced by coating, so it is possible to provide an inexpensive photoreceptor with extremely wide productivity. Furthermore, it 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 objects of the present invention are, firstly, to provide a novel electrophotographic photoreceptor containing a specific trisazo pigment, secondly, to provide a highly sensitive electrophotographic photoreceptor, and thirdly, to provide a highly durable electrophotographic photoreceptor. An object of the present invention is to provide an electrophotographic photoreceptor. The present invention was achieved by paying attention to the fact that an electrophotographic photoreceptor using a trisazo pigment represented by general formula (1) (described later) in a photosensitive layer is extremely useful in electrophotography. . General formula (1) is It is indicated by. A represents a coupler having aromatic properties, and it is particularly desirable that A be 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; The substituents for R ₁ and R ₂ above 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, alkylthio 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】

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. More 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, a cyanoalkyl group, an aminoalkyl group, N-alkylamino group, N,N-dialkylaminoalkyl group, halogenated alkyl group, aralkyl group such as benzyl and phenethyl, phenyl group and substituted phenyl group (substituents include R ₁ and R in general formula (2)) ₂ )
etc. can be mentioned. B ₁ , B ₂ , B ₃ , B ₄ , B ₅ and B ₆ are the same or different, hydrogen atom, halogen atom, methyl, ethyl,
It represents an alkyl group such as propyl, butyl, or an alkoxy group such as methoxy, ethoxy, propoxy, butoxy. 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 , B ₄ , B ₅ , B ₆ have the same meanings as before) is hexazotized by a conventional method, and then the triamine represented by the general formulas (2) to (4) is After coupling an aromatic coupler including the coupler represented by in the presence of an alkali, or once isolating the hexazonium salt of the triamine of general formula (5) in the form of a borofluoride salt or zinc chloride double salt, etc. , a suitable solvent such as N,N-dimethylformamide,
It is easily produced by coupling with an aromatic coupler in the presence of an alkali in a solvent such as dimethyl sulfoxide. 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 any type of electrophotographic photoreceptor having such characteristics is useful, but general In order to increase the transport efficiency of charge carriers generated by light absorption of the trisazo pigment represented by formula (1), it is desirable to use it as a photoreceptor of type (2), (3), or (4). 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. The layer structure requires a conductive layer, a charge generation layer, and a charge transport layer, 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 treated with conductivity, etc. are used. Effective materials for the adhesive layer include resins such as casein, polyvinyl alcohol, water-soluble polyethylene, and nitrocellulose. The thickness of the adhesive layer is
A suitable value is 0.1-5μ, preferably 0.5-3μ. On top of the conductive layer or the adhesive layer applied to the conductive layer,
After the trisazo pigment represented by the general formula (1) is made into fine particles, it is provided without a binder or, if necessary, dispersed in a suitable binder solution, and then applied and dried. 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 5 μm or less, preferably 2 μm or less, and optimally 0.5 μm 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 0.01μ
~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, epoxy resin, casein, polyvinyl alcohol, etc. Various resins are used. A charge transport layer is provided on the charge generation layer thus provided. If the charge transport material does not have 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 transporting substances include electron transporting substances and hole transporting substances. 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
-(p-diethylaminophenyl)pyrazolines such as 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. Charge transport materials are not limited to those listed here,
When used, one type of charge transport material or a mixture of two or more types 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 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 the exposed area and the unexposed area. occurs. 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 ones or known 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. After that, it reaches the surface and neutralizes the negative charges, resulting in an attenuation of the surface potential and an electrostatic contrast between it 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 similar to that used for the charge transport layer of the (3) type photoreceptor, and then 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 a suitable 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. The (4) type photoreceptor forms a charge transfer complex when the electron transport material and hole transport material described in the (3) type photoreceptor are combined, so a solution of the charge transfer complex is mixed with the general formula ( It is obtained by adding the trisazo pigment shown in 1), dispersing it, coating it on a conductive support and drying it. In any of the photoreceptors, the pigment used contains at least one type of pigment selected from trisazo pigments represented by the general formula (1), and if necessary, pigments with different light absorptions are used in combination. For the purpose of increasing the sensitivity or obtaining a panchromatic photoreceptor, the trisazo pigment represented by the general formula (1) is
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 and
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: Pigment below 1,2-bis(p-aminophenyl)-4-
(p-aminobenzal)-imidazolone-5,
After cooling a solution consisting of 6.65 g (0.018 mol), concentrated hydrochloric acid 15.7 ml (0.1782 mol), and 110 ml of water to 4°C, add 3.91 g (0.0567 mol) of sodium nitrite to 11 ml of water.
Drop the solution dissolved in water for 7 minutes, then lower the temperature of the solution to
The mixture was kept at 7° C. and stirred for 30 minutes, and activated carbon was added and filtered to obtain an aqueous hexazonium solution. Next water 630
26.1 g (0.653 mol) of sodium hydroxide per ml, 2-
Hydroxy-3-naphthoic acid anilide 15.6g
(0.0594 mol), and while keeping this solution at 5 to 10℃, add the hexazonium aqueous solution synthesized earlier.
The mixture was added dropwise over 30 minutes, stirred 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 18.5 g of a crude pigment. Next, the mixture was washed successively with DMF and tetrahydrofuran, and then dried to obtain 15.48 g of purified pigment. Triamine base yield 72%, decomposition point 300
℃ or higher Elemental analysis Molecular formula C ₇₃ H ₄₉ N ₁₁ O ₇ Calculated value (%) Analytical value (%) C 73.53 73.41 H 4.15 4.26 N 12.93 12.86 IR absorption spectrum Secondary amide 1670 cm ^-1 or higher No.
Although the synthesis of one pigment has been described above, other trisazo pigments represented by general formula (1) can be synthesized in a similar manner. Next, examples of electrophotographic photoreceptors using the trisazo pigment of the present invention will be shown. Examples 1 to 17 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, add the No. 1 pigment, 5 g of each pigment shown in the table, 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 prepared electrophotographic photoreceptor was statically charged with corona at 5 KV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd., held in a dark place for 10 seconds, and then exposed to light at an illuminance of 5 lux. , 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-attenuation exposure is E1/2 (lux.
sec) and the characteristic values of each photoreceptor are shown in the table.

【table】

【table】

【table】

【table】

【table】

【table】

[Table] Example 18 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. Vo505V, Rv84%, E1/218.4lux.sec Example 19 After dispersing 5 g of pigment No. 11 and 2 g of butyral resin (butyralization degree 63 mol%) in 95 ml of ethanol, aluminum vapor-deposited mylar film was prepared. Apply to the surface and apply a coating amount of 0.2 after drying.
g/ ^m2 . Next, a solution prepared by dissolving 5 g of 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole and 5 g of phenoxy resin (Bakelite PKHH manufactured by UCC) in 70 ml of tetrahydrofuran is applied to the charge generation layer. It was dried to form a charge transport layer with a coating weight of 11 g/m ² . The photoreceptor thus produced was subjected to charge measurement in the same manner as in Example 1. Characteristic values Vo525V, Rv94%, E1/27.2lux.sec Example 20 An ammonia aqueous solution of casein was applied to 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)-
Add 1.0 g of No. 2 pigment to a solution in which 5 g of 5-(2-chlorophenyl)oxazole and 5 g of poly-N-vinylcarbazole (number average molecular weight 300,000) are dissolved in 70 ml of tetrahydrofuran, and after dispersing, apply on the above adhesive layer. It was dried to a coating weight of 12 g/m ² . The produced photoreceptor was subjected to charge measurement in the same manner as in Example 1.
However, the charging polarity was determined. Characteristic values Vo480V, Rv86%, E1/215.2lux.sec Example 21 5g 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 20, 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. Vo
530V, Rv91%, E1/217.5lux.sec Example 22 The charge transport material of Example 1 was used as 1-[quinolyl (2)]
-3-(p-diethylaminostyryl)-5-
A photoreceptor was prepared using (p-diethylaminophenyl)-pyrazoline instead. Next, using the same charge measuring device as in Example 1, charging and exposure conditions were set so that the initial dark potential (V _D ) was 500 V and the light/dark potential (V _L ) was 30 V, and charging was performed under the same conditions. , exposure was repeated and the cycle stability of V _D and V _L was investigated. The results were as follows. Number of measurements (times) V _D (V) V _L (V) 1 500 30 5000 510 40 10000 485 45 As is clear from these 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 aromatic properties, 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, or an alkoxy group. ,) 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 (where R ₁ is a hydrogen atom, a group selected from the group consisting of substituted or unsubstituted alkyl groups and phenyl groups, R ₂ is a group selected from the group consisting of substituted or unsubstituted alkyl groups, phenyl groups and naphthyl groups) The electrophotographic photoreceptor according to claim 1, which represents a group selected from the group consisting of: 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.