JPS6252859B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having a photosensitive layer containing a disazo pigment having an oxazole ring. Conventionally, as electrophotographic photoreceptors made of inorganic photoconductive substances, those using selenium, cadmium sulfide, zinc oxide, etc. are known. On the other hand, as an electrophotographic photoreceptor made of an organic photoconductive substance, poly-N
-Using photoconductive polymers such as vinylcarbazole and various 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 known. As a result of intensive research on pigments used in such organic electrophotographic photoreceptors, the present inventors found that the general formula: The present invention was achieved by discovering that a photoreceptor extremely useful in electrophotography can be obtained by using the novel disazo pigment shown in the following in a photosensitive layer. In the above general formula (1), A represents an aromatic coupler, and 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, and Y is selected from the group consisting of -CONR ₁ R ₂ group (where R ₁ is a hydrogen atom, a group selected from the group consisting of a substituted or unsubstituted alkyl group and a phenyl group, R ₂ is a substituted or unsubstituted alkyl group,
represents a group selected from the group consisting of a phenyl group and a naphthyl group). Substituents for the above R ₁ and R ² groups include alkyl groups such as methyl and ethyl, halogen atoms such as fluorine, chlorine, and bromine, alkoxy groups such as methoxy and ethoxy, acyl groups such as acetyl and benzoyl, methylthio, ethylthio, etc. Alkylthio groups such as, arylthio groups such as phenylthio, aryl groups such as phenyl, aralkyl groups such as benzyl, nitro groups, cyano groups, dimethylamino,
Examples include alkylamino groups such as ethylamino. General formula (3) or (4) is

【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 methyl,
Alkyl groups such as ethyl and propyl, hydroxyalkyl groups such as hydroxymethyl and hydroxyethyl, alkoxyalkyl groups such as methoxymethyl, ethoxymethyl and ethoxyethyl, cyanoalkyl groups, aminoalkyl groups, N-alkylaminoalkyl groups, N, N-dialkylaminoalkyl group, halogenated alkyl group, aralkyl group such as benzyl and phenethyl, phenyl group and substituted phenyl group (as a substituent,
Examples include substituents on R ₁ and R ₂ groups). In the above formula, B represents at least one group selected from a hydrogen atom, a halogen atom, a lower alkyl group, a lower alkoxy group, a hydroxyl group, and an acylamino group. The disazo pigment represented by the general formula (1) has the general formula (wherein B has the same meaning as before) is tetrazotized by a conventional method and then coupled with an aromatic coupler in the presence of an alkali, or a tetrazonium salt of a diamine of general formula (5) is It can be easily produced by once isolating it in the form of a borofluoride salt or zinc chloride salt and then coupling it with an aromatic coupler in the presence of an alkali in a suitable solvent such as N,N-dimethylformamide or dimethyl sulfoxide. can do. The electrophotographic photoreceptor of the present invention may be any type of photoreceptor as long as it contains the disazo pigment represented by the general formula (1) in the photoreceptor layer, but preferably the following (1) is used. Photoreceptors of the types shown in ~(3) are desirable. That is, (1) a layer in which a pigment is dispersed in a charge transporting medium consisting of a charge transporting substance and an insulating binder (the binder itself may be charge transporting) is provided on a conductive layer; (2) a conductive layer; , (3) one consisting of a charge generation layer containing an organic pigment and a charge transport layer, and (3) one in which an organic pigment is added to a charge transfer complex. In the case of a photoconductor of type (3) among the above types of photoconductors, in other words, the charge generation material used in the charge generation layer of a photoconductor separated into two layers, a charge generation layer and a charge transport layer, is represented by the general formula (1). When a disazo pigment is used, the sensitivity of the photoreceptor is particularly improved and the residual potential is low. Further, in this case, a decrease in sensitivity and an increase in residual potential during repeated use can be suppressed to a practically negligible level. Regarding the three types of photoreceptors mentioned above, there is already a lot of information in the literature, so
Here, only the (2) type photoreceptor will be explained. A conductive layer, a charge generation layer, and a charge transport layer are essential as a layer structure, and the charge generation layer can be either above or below the charge transport layer, but in electrophotographic photoreceptors of the type that are used repeatedly, it is mainly a physical layer. From the viewpoint of strength and, in some cases, chargeability, it is preferable to laminate a conductive layer, a charge generation layer, and a charge transport layer in this order. An adhesive layer may be provided as necessary for the purpose of improving the adhesiveness between the conductive layer and the charge generation layer. The conductive layer only needs to be imparted with conductivity, and may be any type of conductive layer conventionally used. As the material for the adhesive layer, various conventionally used binders such as casein are used. The thickness of the adhesive layer is preferably 0.1 to 5 microns, preferably 0.5 to 3 microns. On the conductive layer or the adhesive layer applied to the conductive layer, the disazo pigment represented by the general formula (1) is made into fine particles, and then dispersed without a binder or in an appropriate binder solution if necessary, and applied and dried. establish. When dispersing the disazo pigment, a known method such as a ball mill or an attritor can be used.
The thickness is desirably less than μ, preferably less than 2 μ, and optimally less than 0.5 μ. The disazo pigment can also be applied by dissolving it in an amine solvent such as ethylenediamine. Conventional methods such as blade, Mayer bar, and spray dipping are used for application. The thickness of the charge generation layer is 5μ or less, preferably 0.01~
1μ is desirable. When a binder is used in the charge generation layer, a large amount of binder affects sensitivity, so the proportion of the binder in the charge generation layer is preferably 80% or less, preferably 40% or less. As the binder used, various conventionally used resins such as polyvinyl butyral can be used. A charge transport layer is provided on the charge generation layer. The thickness of the charge transport layer is 5 to 30 microns, preferably 8 to 20 microns. 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-tetranitrofluorenone, 2,4,7 - Electron-withdrawing substances such as trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, and polymerized products of these electron-withdrawing substances, etc. be. Examples of hole-transporting substances include pyrene, N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N-phenylhydrazino-3-methylidene-9-ethylcarbazole, and N,N-diphenylhydrazino-3. -Hydrazones such as methylidene-9-ethylcarbazole, 2,5-bis(p-
Pyrazolines such as diethylaminophenyl)-1,3,4-oxadiazole, 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, triphenylamine, poly- N-vinylcarbazole,
Examples include halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, and ethylcarbazole formaldehyde resin. The charge transport materials are not limited to those described here, and when used, one type or a mixture of two or more types of charge transport materials 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 located below the charge transport layer. Since a low-molecular charge transport substance does not have the ability to form a film by itself, a solution dissolved in a suitable organic solvent together with various binder resins is coated and dried in a conventional manner to form a charge transport layer. As the binder, various conventionally used binders such as acrylic resin and polycarbonate resin can be used. The binder itself may be a polymer having charge transport ability. 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 the charging During post-exposure, electrons generated in the charge generation layer in the exposed area are injected into the charge transport layer, then reach the surface and neutralize the positive charge, causing a decrease in surface potential and creating an electrostatic contrast between the exposed area and the unexposed area. will occur. Various conventionally used developing methods can be used for visualization. On the other hand, when the charge transport material is a hole transport material, the surface of the charge transport layer must be negatively charged. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers, CRTs, etc.
It can also be widely used in electrophotographic applications such as printers and electrophotographic plate making systems. Next, examples of the present invention will be shown. Example 1 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 1.0 g/m ² . Next, add the following structural formula to a solution of 5 g of 1-phenyl 3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl) pyrazoline and 5 g of poly-N-vinylcarbazole (molecular weight 300,000) dissolved in 70 ml of tetrahydrofuran. Added 1.0g of pigment (No. 1) with After dispersion, it was coated on the adhesive layer and the coating amount after drying was 11 g/m ² . The created photoreceptor was sent to Kawaguchi Electric Co., Ltd.
Electrostatic copying paper tester Model SP-428 was used to statically charge the corona at 5KV, and the test was carried out for 10 minutes in the dark.
After being held for seconds, it was exposed to light at an illuminance of 5 lux, and the charging characteristics were examined. The initial potential is Vo (V), the potential retention rate for 10 seconds in the dark is Vk (%), and the half-decay exposure amount is E1/2.
(lux・sec) indicates the charging characteristic value of this photoreceptor. Vo500V, Vk89%, E1/218.4lux·sec. Example 2 An ammonia aqueous solution of casein was applied to the aluminum surface of an aluminum vapor-deposited mylar film, and the coating amount after drying was 1.3 g/m ² . Next, 5 g of a pigment having the following structural formula (Pigment No. 2) and a polyester resin (Polyester Adhesive 49000, solid content manufactured by DuPont) were added.
After dispersing 10g of 20%) and 80ml of tetrahydrofuran, apply it on the adhesive layer above. The coating amount after drying was 0.25 g/m ² . Next, 5 g of p-diethylaminobenzaldehyde-N,N-diphenylhydrazone and 5 g of polymethyl methacrylate resin (molecular weight 100,000) were added to 70 g of tetrahydrofuran.
ml and coated on the charge generation layer to give a coating amount of 10 g/m ² after drying. Charge measurement was carried out in the same manner as in Example 1. Indicates its characteristic value. However, the charging polarity was determined. Vo580V, Vk90%, E1/29.8lux・sec Examples 3 to 17 In the disazo pigment represented by general formula (1),
A and B are those shown in Table 1. After dispersing 5 g of pigment and 2 g of butyral resin (degree of butyralization 63 mol%) in 9.5 ml of ethanol, it was applied to the aluminum surface of an aluminum vapor-deposited Mylar film, and after drying. The coating amount was 0.15 g/m ² . Then 2,5-
Bis(p-diethylaminophenyl)-1,3,
A solution prepared by dissolving 5 g of 4-oxadiazole and 5 g of poly-4,4'-dioxydiphenyl-2,2-propane carbonate (molecular weight 30,000) in 70 ml of tetrahydrofuran was coated on the charge generating layer and dried. A charge transport layer with an amount of 10 g/m ² was formed. The electrostatic charge of the produced photoreceptor was measured in the same manner as in the examples, and the characteristic values are shown in Table 2. However, the charging polarity was determined.

【table】

【table】

【table】

【table】

【table】

[Table] Example 18 2, 4,
5 g of 7-trinitrofluorenone and 5 g of the polycarbonate resin used in Example 3 were dissolved in 70 ml of tetrahydrofuran, and the coating amount after coating and drying was 11 g/m ²
And so. Charge measurement was carried out in the same manner as in Example 1,
Indicates characteristic value. Vo490V, Vk88%, E1/218・
8lux・sec Example 19 1-(6-methoxy-2-pyridyl)-3-(p
-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline and 5 g of poly-N-vinylcarbazole (molecular weight 300,000) dissolved in 70 ml of tetrahydrofuran, add 1.0 g of pigment No. 1 used in Example 1. After dispersion, the mixture was coated and dried on the same adhesive layer as in Example 1 to give a coating weight of 12 g/m ² .
The produced photoreceptor was charged and measured in the same manner as in Example 1, and the characteristic values are shown below. Vo480V, Vk89%, E
1/217.2lux・sec

Claims (1)

[Claims] 1. General formula (In the formula, A represents a coupler having aromaticity,
B is a hydrogen atom, a halogen atom, a lower alkyl group,
1. An electrophotographic photoreceptor comprising a disazo pigment represented by at least one group selected from a lower alkoxy group, a hydroxyl group, and an acylamino group. 2 In the disazo pigment represented by general formula (1),
A is the general formula (2) [formula] [wherein x is a residue that is fused with a benzene ring to form a naphthalene ring, anthracene ring, carbazole ring, or dibenzofuran ring, and Y is selected from the group consisting of -CONR ₁ R ₂ a group selected from the group consisting of a hydrogen _atom , a substituted or unsubstituted alkyl group, and a phenyl group,
2. The electrophotographic photoreceptor according to claim 1, wherein R ₂ represents a group selected from the group consisting of a substituted or unsubstituted alkyl group, phenyl group, and naphthyl group. 3 In the disazo pigment represented by general formula (1),
A is the general formula (3) or (4) [Formula] [Formula] (In formula (3) or (4), R ₃ represents a group selected from the group consisting of substituted or unsubstituted alkyl groups and phenyl groups. ) The electrophotographic photoreceptor according to claim 1. 4. The electrophotographic photoreceptor according to claim 1, comprising at least three layers: a conductive layer, a charge generation layer containing a disazo pigment represented by general formula (1), and a charge transport layer.