JPS6255662B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor using a trisazo pigment having a pyridine ring. Conventional photoreceptors containing organic pigments on a conductive layer include (i) a layer in which pigments are dispersed in an insulating binder on a conductive layer as disclosed in Japanese Patent Publication No. 52-1667 (electrophotographic plate); (ii) A charge transporting substance or such substance and an insulating binder as disclosed in JP-A-47-30328 (electrophotographic plate) and JP-A-47-18545 (electrophotographic imaging method); (iii) Disclosed in JP-A-49-105537 (electrophotographic plate), in which a layer in which a pigment is dispersed in a charge transport medium consisting of a binder (the binder itself may be a charge transport material) is provided on a conductive layer. (iv) an organic pigment in a charge transfer complex as disclosed in JP-A-49-91648 (photoconductive member); (v) Others. Many pigments have been proposed for use in these photoreceptors, including phthalocyanine pigments, polycyclic quinone pigments, azo pigments, and quinacridone pigments, but so far very few have been put into practical use. be. The reason is that organic photoconductive pigments are
This is because it is inferior to Se, CdS, ZnO, etc. in terms of sensitivity and durability. On the other hand, inorganic photoreceptors also have problems; Se-based photoreceptors easily crystallize due to factors such as temperature, humidity, dust, and fingerprints, especially when the ambient temperature of the photoreceptor is 40°C.
When the temperature exceeds the range, crystallization becomes noticeable, resulting in disadvantages such as a decrease in chargeability and the appearance of white spots on images. Although the lifespan of Se-based photoreceptors is said to be around 30,000 to 50,000 copies, because environmental conditions vary widely depending on the region and location where the copying machine is installed, many photoreceptors do not reach the above-mentioned lifespan. The current situation is what is happening. In the case of a CdS photoconductor coated with an insulating layer, the lifetime is also
However, it is extremely difficult to overcome the poor moisture resistance caused by CdS, and supplementary measures such as heaters are required to prevent the photoreceptor from absorbing moisture. This is the current situation. In the case of ZnO photoreceptors, they are sensitized with dyes such as rose bengal, so there are problems such as deterioration due to current application and photofading of the dye due to corona charging, and the current lifespan of the photoreceptor is approximately 1000 copies. has been done. Furthermore, Se photoreceptors are expensive and, like CdS photoreceptors, have the same pollution problems. The sensitivity of conventional photoreceptors is half-attenuation exposure (E1/2)
When expressed as , the unsensitized Se-based photoconductor has a sensitivity of around 15 lux.sec, the sensitized one has a sensitivity of about 4-8 lux.sec, and the sensitivity of a CdS-based photoconductor is about the same as that of sensitized Se. and 7 to 12 lux for ZnO photoreceptor.
It is about sec. The E1/2 value is PPC for the sensitivity of a practical photoreceptor.
For copying machines, 20lux.sec or less is desirable, and for PPC copying machines with high copying speeds, 15lux.sec or less is more desirable. However, depending on the application, it may be possible to use it even if the sensitivity is less than the above-mentioned sensitivity. The present inventors have conducted intensive research to overcome the drawbacks of conventional inorganic photoreceptors and to improve the drawbacks of organic electrophotographic photoreceptors that have been proposed so far, and as a result, they have developed a photoreceptor containing a trisazo pigment having a pyridine ring. It has high sensitivity and high durability that can be put to practical use, and it also overcomes the problems of heat resistance (Se crystallization), moisture resistance, photobleaching resistance, and pollution resistance that have been problems with inorganic photoreceptors. The inventors have discovered that an excellent electrophotographic photoreceptor can solve the above problems, and have arrived at the present invention. The trisazo pigment having a pyridine ring used in the present invention is represented by the following general formula (1). 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 forms a naphthalene ring, anthracene ring, carbazole ring, or dibenzofuran ring by condensation with a benzene ring, and Y is a group selected from the group consisting of -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, and R ₂ is a group selected from the group consisting of substituted or unsubstituted alkyl groups, phenyl groups, and naphthyl groups. (represents a group). Substituents for the above R ₁ and R ₂ groups include alkyl groups such as methyl and ethyl groups, fuso atoms,
Halogen atoms such as chlorine and bromine atoms, alkoxy groups such as methoxy and ethoxy groups, acyl groups such as acetyl and benzoyl groups, alkylthio groups such as methylthio and ethylthio groups, arylthio groups such as phenylthio, phenyl groups, etc. aryl group, aralkyl group such as benzyl group,
Examples include alkylamino groups such as a nitro group, a cyano group, a dimethylamino group, and an ethylamino group. 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 a methyl group, an ethyl group,
Alkyl groups such as propyl groups, hydroxyalkyl groups such as hydroxymethyl groups and hydroxyethyl groups, alkoxyalkyl groups such as methoxymethyl groups, ethoxymethyl groups, and ethoxyethyl groups, cyanoalkyl groups, aminoalkyl groups, and N-alkylaminoalkyl groups. groups, N,N-dialkylaminoalkyl groups, halogenated alkyl groups, benzyl groups, aralkyl groups such as phenethyl groups, phenyl groups and substituted phenyl groups (as substituents, R ₁ and R ₂ in general formula (2)) )
etc. can be mentioned. The trisazo pigment represented by the general formula (1) has the structural formula

The triamine represented by the formula is hexazotized by a conventional method, and then coupled with the coupler represented by the general formulas (2) to (4) in the presence of an alkali, or the hexazonium salt of the triamine is converted into a borofluoride salt or zinc chloride. Once isolated in salt form, a suitable solvent such as N,
General formulas (2) to (4) in the presence of an alkali in a solvent such as N-dimethylformamide or dimethyl sulfoxide
It can be easily manufactured by coupling with a coupler. The electrophotographic photoreceptor of the present invention is characterized by having a photosensitive layer containing a trisazo pigment represented by the general formula (1), and is any of the types of electrophotographic photoreceptors described in (i) to (v) above. It can also be applied to the general formula
In order to increase the transport efficiency of charge carriers generated by light absorption of the trisazo pigment shown in (1), (ii)
It is desirable to use it as a photoconductor of type (iii) or (iv). Further, a photoreceptor of type (iii) 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, this type of electrophotographic photoreceptor will be described in detail. 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 electrophotographic photoreceptors of the type that are used repeatedly, it is mainly From the viewpoint of physical 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. As the conductive layer, a metal plate or foil made of aluminum or the like, a plastic film coated with a metal such as aluminum or aluminum foil glued to paper, or paper treated with conductivity is 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 to 5μ, preferably 0.5 to 3μ. On the adhesive layer applied to the charge generation layer or the conductive layer, the trisazo pigment represented by the general formula (1) is made into fine particles, then dispersed without a binder or in an appropriate binder solution if necessary, and applied and dried. and set it up. When dispersing the trisazo pigment, known methods such as ball milling and attritor can be used, and it is desirable that the pigment particles be 5 microns or less, preferably 2 microns or less, most preferably 0.5 microns 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, 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. 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 organic 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-tetranitrofluorenone, 2,4,7 Electron-withdrawing substances such as -trinitro-9-dicyanomethylenefluorene, 2,4,5,7-tetranitroxanthone, and 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,
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-[pyridyl-(2)]-3
-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[quinolyl(2)]-3-(p-diethylaminostyryl)-
Pyrazolines such as 5-(p-diethylaminophenyl)pyrazoline, triphenylamine, poly-N-vinylcarbazole, halogenated poly-N
-Vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-
Examples include formaldehyde resin and ethyl carbazole formaldehyde resin. The charge transport material is
It is not limited to what is 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 located below the charge transport layer. The thickness of the charge transport layer is 5 to 30μ, preferably 8 to 20μ.
μ. 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 US Pat. No. 4,122,113 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, it is necessary to positively charge the surface of the charge transport layer, and when exposed to light after charging, In the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface to neutralize the positive charges, resulting in attenuation of the surface potential and an electrostatic contrast between the exposed area and the unexposed area. 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 or plastic film 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.
When imagewise exposed after charging, holes generated in the charge generation layer in the exposed area are injected into the charge transport layer, neutralizing the negative charges that have reached the surface, causing a decrease in the surface potential and a gap between the exposed area and the unexposed area. Electrostatic contrast occurs. During development, it is necessary to use a positively charged toner, contrary to the case where an electron transporting substance is used. The (i) 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 (iii) type photoreceptor, and dispersing it onto a conductive support. Obtained by coating and drying. The (ii) type photoreceptor is manufactured by dissolving the charge transport material of the (iii) 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. (iv) type photoreceptor forms a charge transfer complex when the electron transport material and hole transport material described in type (iii) photoreceptor are combined, so the general formula (1) is present in the solution of this charge transfer complex. Adding a trisazo pigment shown in
After dispersion, it is obtained by coating and drying on a conductive support. The trisazo pigment used in any of the photoreceptors 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 to increase the sensitivity of the photoreceptor. For the purpose of increasing the photoreceptor and obtaining a panchromatic photoreceptor, two or more types of trisazo pigments represented by the general formula (1) are combined, or known dyes,
It is also possible to use it in combination with charge-generating materials selected from pigments. 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, the trisazo pigment used in the present invention will be specifically explained using synthesis examples. Synthesis example: Pigment below A dispersion consisting of 5.0 g (0.014 mol) of 2,4,6-tri(p-aminophenyl)pyridine, 12.4 ml (0.14 mol) of concentrated hydrochloric acid, and 200 ml of water was cooled to 4.5°C, and the liquid temperature was adjusted to 4.5 to 6.5°C. 20ml of a solution of 3.1g (0.045mol) of sodium nitrite dissolved in 20ml of water.
The mixture was added dropwise over a period of minutes and stirred for an additional 25 minutes to obtain a hexazotized liquid. Next, dissolve 20 g (0.5 mol) of caustic soda and 11.8 g (0.045 mol) of naphthol AS (3-hydroxy-2-naphthoic acid anilide) in 550 ml of water, and while keeping this liquid at 5-8°C, convert the previously synthesized hexazotized The liquid was added dropwise over 35 minutes, stirring was continued for an additional hour, and then left at room temperature overnight. The pigment obtained by filtering the reaction solution was washed with water, acetone, and dried to obtain 16.6 g of a crude pigment (99.5% crude yield from triamine). The crude pigment was then heated five times with 400 ml of DMF and once with acetone and dried to obtain 12.5 g (75% yield from triamine) of pigment. Decomposition point 300℃ or higher, visible absorption spectrum absorption maximum wavelength 555nm (o
- dichlorobenzene solution), IR absorption spectrum amide 1675 cm ^-1 or more Although the method for synthesizing the No. 1 pigment has been described, other trisazo pigments represented by the general formula (1) can be synthesized in the same manner. Next, examples of the present invention will be shown. Example 1 An ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 g of water) was placed on an aluminum plate.
ml) with a Mayer bar and dry, coating amount 1.0
An adhesive layer of g/m ² was formed. Next, 5g of pigment No.1
and butyral resin (butyralization degree 63 mol%) 2
The mixture was dispersed in a ball mill with a solution of 95 ml of ethanol, and then coated on the adhesive layer with a Mayer bar to form a charge generation layer having a coating weight of 0.2 g/m ² after drying. Next, 5 g of 1-phenyl-3(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, poly-4,4'-dioxydiphenyl-2,2'-propane carbonate (molecular weight
30000) dissolved in 70 ml of tetrahydrofuran was applied onto the charge generation layer and dried, resulting in a coating amount of 11 g/
A charge transport layer of m ² was formed. The electrophotographic photoreceptor prepared in this way was heated at 20℃65
% (relative humidity), corona charged at 5KV statically 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 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 Vk (%), and the half-decay exposure is E1/2 (lux.
sec) to show the charging characteristics of this photoreceptor. Vo
600V, Vk96%, E1/210.7lux.sec Example 2 Example 1 was applied on the charge generation layer created in Example 1.
2,5-bis(p-
A charge transport layer using (diethylaminophenyl)-1,3,4-oxadiazole was formed. The produced photoreceptor was subjected to charge measurement in exactly the same manner as in Example 1, and the characteristic values were as follows. Vo580V,
Vk94%, E1/210.8lux.sec. Example 3 2, 4,
5 g of 7-trinitrofluorenone and 5 g of the polycarbonate resin used in Example 1 were dissolved in 70 ml of tetrahydrofuran, coated with a Mayer bar, and dried to give a coating weight of 11 g/m ² . Charge measurement was carried out in exactly the same manner as in Example 1, and the characteristic values were as follows. However, the charging polarity was determined. Vo540V,
Vk92%, E1/218lux.sec. Examples 4 to 10 5 g of trisazo pigment represented by general formula (1) and polyester resin solution (polyester adhesive
49000 (manufactured by DuPont, solid content 20%) and 80 ml of tetrahydrofuran were dispersed in a ball mill and applied to the aluminum surface of an aluminum vapor-deposited Mylar film using a Mayer bar, and the coating amount after drying was 0.15 g/m ² . Next, 5 g of 1-[6-methoxypyridyl(2)]-3-(p-diethylaminostyryl)-5-p-diethylaminophenylpyrazoline and 5 g of polymethyl methacrylate resin (molecular weight 100,000) were dissolved in 70 ml of tetrahydrofuran. , coated on the above charge generation layer using a baker applicator, and measured the film thickness after drying.
It was set to 10g/ ^m2 . The electrostatic charge of the photoreceptor thus prepared was measured in the same manner as in Example 1, and the results are shown in the table.

【table】

[Table] Example 11 p-diethylaminobenzaldehyde-N,N
- 1.0 g of Pigment No. 8 shown in the table was added to a solution of 5 g of diphenylhydrazone and 5 g of poly-N-vinylcarbazole (molecular weight 300,000) dissolved in 70 ml of tetrahydrofuran and dispersed in a ball mill. Example 1
Coated with a Mayer bar on the casein layer of the aluminum plate with the casein layer used in , and measured the amount of coating after drying.
It was set to 9.5g/ ^m2 . The electrostatic charge of the produced photoreceptor was measured in the same manner as in Example 1, and the characteristic values are shown below. However, the charging polarity was determined. Vo560V, Vk88%, E
1/219lux.sec.

Claims (1)

[Claims] 1. General formula An electrophotographic photoreceptor comprising a photosensitive layer containing a trisazo pigment represented by the formula (wherein A represents an aromatic coupler). 2 In the trisazo pigment represented by the general formula (1), A is the general formula [In the formula, X is a residue condensed with a benzene ring to form _a naphthalene ring, an anthracene ring, a _carbazole ring, or _a dibenzofuran ring; , 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 the general formula [formula] (in the formula (3) or (4), R ₃ consists of a substituted or unsubstituted alkyl group and a phenyl group) 2. 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, wherein the trisazo pigment has the following structural formula. 5. The electrophotographic photoreceptor according to claim 1, wherein the trisazo pigment has the following structural formula. 6. 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. 7. An electrophotographic photoreceptor according to claim 6, which uses the trisazo pigment according to claim 4 or 5.