JPH0153458B2 - - 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 disazo 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-vinylgalbazole and 2,5-bis(p-diethylaminophenyl)-1,3,4- Those using a low-molecular organic photoconductive substance such as oxadiazole, and those using a combination of such an organic photoconductive substance and 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 extremely highly productive and inexpensive photoreceptor. 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 into practical use. The first object of the present invention is to provide a novel electrophotographic photoreceptor containing a characteristic disazo pigment,
The second objective is to provide a highly sensitive electrophotographic photoreceptor, and the third objective is to provide a highly durable electrophotographic photoreceptor. The inventors have determined that the general formula (A, B ₁ , B ₂ , B ₃ , B ₄ , B ₅ , B ₆
The present invention was developed based on the fact that an electrophotographic photoreceptor using a disazo pigment in a photosensitive layer is extremely useful in electrophotography. The present invention is an electrophotographic photoreceptor characterized by containing a disazo pigment represented by general formula (1). In the general formula (1) above, A represents a coupler having aromatic properties, and in particular, A represents the following general formulas (2) to (4).
It is selected from the couplers represented by 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, Y is a group consisting of -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,
R ₂ B represents a group selected from the group consisting of a substituted or unsubstituted alkyl group, phenyl group, and naphthin group. Examples of substituents in the R ₁ and R ₂ groups include alkyl groups such as methyl, ethyl, propyl, and butyl; halogen atoms; alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy; acyl groups such as acetyl and benzoyl; Alkylthio groups such as methylthio and ethylthio, aryl groups such as phenyl,
Examples include aralkyl groups such as benzyl and phenethyl, 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 is a group selected from the group consisting of substituted or unsubstituted alkyl groups and phenyl groups, such as alkyl groups such as methyl, ethyl, propyl, butyl, and hydroxyalkyl groups such as hydroxymethyl and hydroxyethyl. , alkoxyalkyl groups such as methoxymethyl and ethoxyethyl, cyanoalkyl groups, aminoalkyl groups, N-
Alkylamino groups, N,N-dialkylaminoalkyl groups, halogenated alkyl groups, aralkyl groups such as benzyl and phenethyl, phenyl groups and substituted phenyl groups (substituents include R ₁ in general formula (2),
R ₂ can be given. ) etc. In general formula (1), B ₁ , B ₂ , B ₄ , B ₅ , B ₆ are hydrogen atoms,
Each represents a halogen atom, an alkyl group such as methyl, ethyl, propyl, butyl, an alkoxy group such as methoxy, ethoxy, propoxy, butoxy, or a hydroxyl group, and may be the same or different. The disazo 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 , and B ₆ have the same meanings as before) is tetrazotized by a conventional method, and then the diamine represented by the general formulas (2) to (4) is Coupling the couplers shown in the presence of an alkali or
Once the tetrazonium salt of the diamine of general formula (5) is isolated in the form of a borofluoride salt or zinc chloride double salt, it is isolated in the presence of an alkali in a suitable solvent such as N,N-dimethylformamide or dimethyl sulfoxide. It is easily produced by coupling with a coupler having aromatic properties. Electrophotographic photoreceptors containing an organic pigment on a conductive layer include (1) a layer in which a pigment binder is dispersed on a conductive layer as disclosed in Japanese Patent Publication No. 52-1667; Publication No. 47-18545, Japanese Unexamined Patent Publication No. 1983-
30328, or a layer in which a pigment is dispersed in a charge transport medium consisting of a charge transport material and an insulating binder (the binder itself may be a charge transport material) is provided on a conductive layer. , (3) one consisting of a conductive layer, a charge generation layer containing an organic pigment, and a charge transport layer as disclosed in JP-A No. 49-105537; (4) one as disclosed in JP-A-49-91648; There are charge transfer complexes such as those in which organic pigments are added. The electrophotographic photoreceptor of the present invention is characterized by containing a disazo pigment represented by the general formula (1), and can be applied to any type of electrophotographic photoreceptor as long as it has such characteristics. , general formula (1)
In order to increase the transport efficiency of the charge carrier generated by light absorption of the disazo pigment shown in (2), (3),
It is desirable to use it as a photoreceptor of type (4). Further, the photoreceptor of type (3), which separates the function of generating a charge carrier and the function of transporting a charge carrier, is most desirable in terms of taking advantage of the characteristics of the pigment. Therefore, this (3) type electrophotographic photoreceptor will be explained in detail. The layer structure requires a conductive layer, a charge generation layer, and a charge transport layer, 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 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 from the viewpoint of physical strength and, in some cases, 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 or adhesive layer applied to the conductive layer,
After the dispersion 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. For dispersing the disazo pigment, known methods such as ball milling and attritor can be used, and it is desirable that the particle size is 5 μm or less, preferably 2 μm or less, most preferably 0.5 μm or less. The disazo 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 film layer of the charge generation layer has a thickness of 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. Binders used include various resins such as polyvinyl butyral, polyvinyl acetate, polyester, polycarbonate, phenoxy resin, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, and polyvinyl alcohol. There is. 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 crylanyl, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorene, 2,4,5,7-tetranitro-9-
Fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-
Examples include electron-withdrawing substances such as tetranitroxanthone and 2,4,8-trinitrothioxanthone, and polymerized versions 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)pyrazoline and other pyrazolines, 2-(p-diethylaminostyryl)-6-
Diethylaminobenzoxazole, 2-(p-
2-(p-
thiazole compounds such as diethylaminostyryl)-6-diethylaminobenzothiazole, triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane,
Examples include triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin, and the like. Charge transport materials are not limited to those listed here, but when using them,
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 below the charge transport layer. . The film layer of the charge transport layer has a thickness of 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 transporting monomers 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 layer is made of 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, resulting in attenuation of the surface potential and an electrostatic contrast between it and the unexposed area. arise. 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., 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, developing method, and fixing method may be any known one or any known method, and are not limited to specific characteristics. On the other hand, when the charge transport material is a hole transport material, it is necessary to charge the surface of the charge transport layer negatively, 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 a disazo 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 the insulating binder used in the charge transport layer in a suitable solvent, and then dissolving the disazo pigment represented by the general formula (1). After adding and dispersing, it is obtained by coating and drying on a conductive support. Type (4) photoreceptors form 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 mixed with the general formula (1). ) is added,
After dispersion, it is obtained by coating and drying on a conductive support. In any of the photoreceptors, the pigment used contains at least one type of pigment selected from the disazo pigments represented by the general formula (1), and if necessary, pigments with different light absorptions may be combined to make the photoreceptor used. For the purpose of increasing the sensitivity of the photoreceptor or obtaining a panchromatic photoreceptor, two or more types of disazo faces represented by the general formula (1) are combined, or a charge generating material selected from known dyes and pigments is used. It is also possible to use them in combination. 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, regarding the disazo pigment used in the present invention,
An example of its synthesis is shown below. Synthesis example The following pigment (referred to as pigment No. 1) 2,5-bis(p-aminophenyl)-1,3,
After cooling a solution consisting of 6.85 g (0.020 mol) of 4,6-benzvitriazole, 11.6 ml (0.132 mol) of concentrated hydrochloric acid, and 120 ml of water to 4°C, 2.90 g of sodium nitrite was added.
A solution prepared by dissolving 10 g (0.042 mol) in 10 ml of water was added dropwise over 10 minutes, and stirring was continued for 30 minutes while maintaining the temperature of the solution at 4 to 7°C. Thereafter, activated carbon was added and filtered to obtain a tetrazinium aqueous solution. Next, in 45.0 ml of water, 19.5 g (0.488 mol) of sodium hydroxide and 11.6 g (0.044 mol) of 2-hydroxy-3-naphthoic acid anilide.
was dissolved, and while maintaining this solution at 5 to 10°C, the previously synthesized tetrazonium aqueous solution was added dropwise over 30 minutes, and after stirring for an additional hour, it was left to stand at room temperature overnight. The pigment obtained by filtering the reaction solution was washed with water and dried to obtain 16.5 g of a crude pigment. Next, wash with DMF and tetrahydrofuran sequentially and dry.
g of purified pigment was obtained. Diamine-based purified pigment yield 67.9%, decomposition point above 300℃ Elemental analysis Molecular formula C ₅₂ H ₃₄ O ₄ N ₁₂ Calculated value (%) Analytical value (%) C 70.09 69.84 H 3.85 4.01 N 18.87 18.70 IR absorption spectrum 2nd Amide 1670cm ^-1 or more No.
Although the synthesis of one pigment has been described, other disazo pigments represented by general formula (1) can be synthesized in a similar manner. Next, examples of electrophotographic photoreceptors using disazo pigments having the characteristics of the present invention will be shown. Examples 1 to 13 An aqueous polyvinyl alcohol solution was applied and dried on an aluminum plate having a thickness of 100 μm to form an adhesive layer with a coating weight of 0.8 g/m ² . Next, add 5 g each of the No. 1 pigment and each pigment shown in the following table to a polyester resin (Polyester Adhesive 49000 manufactured by DuPont).
After dispersing 10 g (solid content 20%) and 80 ml of tetrahydrofuran, apply it on the adhesive layer, and check the coating amount after drying.
It was set to 0.20g/ ^m2 . Next, p-diethylaminobenzaldehyde-N,N-diphenylhydrazone 5
g, 5 g of polymethyl methacrylate resin (number average molecular weight 100,000) was dissolved in 70 ml of tetrahydrofuran, coated on the charge generation layer, and after drying, the coating amount was 10
g/ ^m2 . The electrophotographic photoreceptor produced in this way was manufactured by Kawaguchi Electric Co., Ltd. using an electrostatic copying paper testing device, Model SP-428.
The sample was statically charged with a corona at 5KV using a 100V, held in the dark for 10 seconds, and then exposed to light at an illuminance of 5lux 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 semiconducting light exposure is E1/2 (lux,
sec), and the charging characteristics of each photoreceptor are shown in the table below.

【table】

【table】

【table】

【table】

[Table] Example 14 On the charge generation layer prepared in Example 1, 2, 4,
5g of 7-trinitro-9-fluorenone and poly-
5 g of 4,4'-dioxydiphenyl-2,2-carbonate (viscosity average molecular weight 30,000) was dissolved in 70 ml of tetrahydrofuran, and the coating amount after drying was 12
g/ ^m2 . Charge measurement was carried out in the same manner as in Example 1, and the characteristic values were as follows. However, the charging property was determined. Vo510V, Rv92%, E1/220.5lux, sec Example 15 After dispersing 5g of pigment No.13 and 2g of butyral resin (butyralization degree 63 mol%) in 95ml 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. , and dried to form a charge transport layer with a coating weight of 11 g/m ² . The electrostatic charge of the prepared electrophotographic photoreceptor was measured in the same manner as in Example 1. Its characteristic values were as follows. Vo520V, Rv93%, E1/28.2lux.sec Example 16 A casein alumonia aqueous solution was applied and dried on a 100μ thick aluminum plate to form an adhesive layer with a coating weight of 1.0g/m ² . Then 2-(p-diethylaminophenyl)4-(p-dimethylaminophenyl)-5
-(2-chlorophenyl)oxazole 5g and poly-N-vinylcarbazole 5g (number average amount 30
No. 1,000) dissolved in 70 ml of tetrahydrofuran.
1.0 g of Pigment No. 4 was added, and after being dispersed, it was applied and dried on the adhesive layer to give a coating weight of 12 g/m ³ . Charge measurement was performed on the produced photoreceptor, and the following characteristic values were obtained. However, the charging polarity was determined. Vo490V, Rv85%, E
1/216.0lux.sec Example 17 5 g of 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline and poly-2,2-propane bis(4-
phenyl isophthalic acid-tetophthalic acid ester),
(Isophthalic acid, terephthalic acid molar ratio 1:1)5
After dissolving g in 70ml of tetrahydrofuran, No.1
1.0 g of pigment was added, and after being dispersed, it was applied and dried on the adhesive layer used in Example 16 to give a coating amount of 12 g/m ³ . The charging characteristics of the produced photoreceptor were as follows. However, the charging polarity was determined. Vo525V, Rv92%, E1/218.5lux.sec Example 18 The charge transport material of Example 1 was used as 1-[quinolyl-(2)]
-3(p-diethylaminostyryl)-5-(p-
A photoreceptor was prepared in the same manner as in Example 1 except that pyrazoline (diethylaminophenyl) was used. 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 potential (V _L ) was 30 V. By repeating charging and exposure, V _D ,
The cycle stability of V _L was investigated. Number of measurements (times) V _D (V) V _L (V) 1 500 30 5000 500 35 10000 485 45 As shown above, 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,
B ₁ , B ₂ , B ₃ , B ₄ , B ₅ , and B ₆ are each a hydrogen atom,
An electrophotographic photoreceptor comprising a disazo pigment represented by a group selected from the group consisting of a halogen atom, an alkyl group, an alkoxy group, and a hydroxyl group. 2 In the disazo pigment represented by general formula (1),
A is the general formula [Formula] [In the formula, X is fused with a benzene ring to form a naphthalene ring,
Residues forming anthracene ring, carbazole ring, dibenzofuran ring, Y is a group selected from the group consisting of -CONR ₁ R ₂ (However, R ₁ consists 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, a phenyl group, and a naphthyl group. . 3 In the disazo pigment represented by general formula (1),
The electron beam according to claim 1, wherein A is the general formula [Formula] or [Formula] (wherein R ₃ represents a group selected from the group consisting of a substituted or unsubstituted alkyl group and a phenyl group) Photographic photoreceptor. 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.