JPH0752298B2 - Electrophotographic photoreceptor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor containing an azo pigment having a coupler component having a specific structure.

[Prior Art] Conventionally, inorganic photoconductive substances such as selenium, cadmium sulfide, and zinc oxide have been widely used as electrophotographic photoreceptors.

On the other hand, as an electrophotographic photoreceptor using an organic photoconductive substance, a photoconductive polymer typified by poly-N-vinylcarbazole or 2,5-bis (p-diethylaminophenyl) -1,3,4- It is known to use a low molecular weight organic photoconductive substance such as oxadiazole, and further to combine such an organic photoconductive substance with various dyes and pigments.

An electrophotographic photosensitive member using an organic photoconductive substance has good film-forming properties and can be produced by coating, so that it has the advantage of being extremely high in productivity and providing an inexpensive photosensitive member. Further, it has an advantage that the color sensitivity can be freely controlled by selecting a sensitizer such as a dye or a pigment to be used, and has been extensively studied so far. In particular, recently, the development of a function-separated photoreceptor in which a charge generation layer containing an organic photoconductive dye or pigment and a charge transport layer containing the above-mentioned photoconductive polymer or a low molecular weight organic conductive substance are laminated The sensitivity and durability, which have been considered to be the drawbacks of conventional organic electrophotographic photoreceptors, have been remarkably improved.

Since azo pigments have excellent photoconductivity, and pigment compounds having various characteristics can be easily obtained by combining the azo component and the coupler component, many pigment compounds have been proposed so far.

Examples of couplers used in such azo pigments include naphthol AS-based compounds described in JP-A-47-375438 and benzcarbazole-based compounds described in JP-A-53-95033. The naphthalimide compounds described in JP-A-54-79632 and the perinone compounds described in JP-A-57-176055 are already known.

However, conventional electrophotographic photoreceptors using azo pigments are not always sufficient in terms of sensitivity and potential stability during repeated use, and only a few materials have been put into practical use.

[Problems to be Solved by the Invention] An object of the present invention is to provide a novel photoconductive material,
An object of the present invention is to provide an electrophotographic photoreceptor having practically high sensitivity characteristics and stable potential characteristics upon repeated use.

[Means and Actions for Solving the Problems] The present invention provides an electrophotographic photoreceptor having a photosensitive layer containing an azo pigment on a conductive support, wherein the azo pigment is an azo pigment represented by the following general formula (1). And an electrophotographic photosensitive member.

In the formula, Ar represents an aromatic hydrocarbon group or a heterocyclic group which may have a substituent which may be bonded via a bonding group, and X represents a substituent which is condensed with a benzene ring. Represents a residue necessary for forming an aromatic hydrocarbon ring or an aromatic heterocycle, R represents an alkyl group or an aryl group, m is an integer of 0 or 1, and n is 1, 2 or It is an integer of 3.

In the azo pigment represented by the general formula (1), specific examples of Ar include aromatic hydrocarbon groups such as benzene, naphthalene, fluorene, phenanthrene, anthracene, and pyrene,
Heterocyclic groups such as furan, thiophene, pyridine, indole, benzothiazole, carbazole, acridone, dibenzothiophene, benzoxazole, oxadiazole, and thiazole, as well as the above aromatic hydrocarbon groups or heterocyclic groups directly or aromatic Bound by a group or a non-aromatic group, for example biphenyl, binaphthyl,
Diphenylamine, triphenylamine, N-methyldiphenylamine, fluorenone, phenanthrequinone,
Anthraquinone, benzanthrone, terphenyl, diphenyloxadiazole, stilbene, distyrylbenzene, phenylbenzoxazole, diphenylmethane, diphenylsulfone, diphenylether, benzophenone, tetraphenyl-p-phenylenediamine,
Examples thereof include groups such as tetraphenylbenzidine, N-phenyl-2-pyridylamine and N, N-diphenyl-2-pyridylamine.

Specific examples of X include aromatic hydrocarbon rings such as benzene and naphthalene, and heterocycles such as indole, carbazole, benzcarbazole, and benzofuran.

Examples of the substituent which the above aromatic hydrocarbon group or heterocyclic group may have include an alkyl group such as methyl, ethyl, propyl and butyl, an alkoxy group such as methoxy, ethoxy and propoxy, a fluorine atom and a chlorine atom, Examples thereof include halogen atoms such as bromine atom, dialkylamino groups such as dimethylamino and diethylamino, hydroxy group, nitro group, cyano group and halomethyl group.

Specific examples of R include an alkyl group such as methyl and ethyl, an aryl group such as phenyl, and the like.

Typical examples of the azo pigment represented by the general formula (1) are listed below, but the azo pigment is not limited to these.

The description method is based on the basic type and only the changed portion of the basic type is described.

Basic type 1 Exemplified pigment (1-1) m = 0, n = 2 Exemplified pigment (1-2) m = 0, n = 2 Exemplified pigment (1-3) m = 1, n = 2 Exemplified pigment (1-4) m = 0, n = 3 Exemplified pigment (1-5) m = 0, n = 2 R: methyl group basic type 2 Exemplified pigment (2-1) m = 0, n = 1 R: methyl group Exemplified pigment (2-2) m = 1, n = 2 Exemplified pigment (2-3) m = 0, n = 2 Basic type 3 Exemplified pigment (3-1) m = 0, n = 2 Exemplified pigment (3-2) m = 1, n = 2 Exemplified pigment (3-3) m = 0, n = 3 Basic type 4 Exemplified pigment (4-1) m = 0, n = 1 Y: Hydrogen atom Exemplified pigment (4-2) m = 0, n = 2 R: methyl group Y: chlorine atom Exemplified pigment (4-3) m = 1, n = 2 Y: Hydrogen atom Exemplified pigment (4-4) m = 0, n = 2 Y: Bromine atom Exemplified pigment (4-5) m = 0, n = 2 Y: Fluorine atom basic type 5 Exemplified pigment (5-1) m = 0, n = 2 Exemplified pigment (5-2) m = 0, n = 2 The coupler used in the synthesis of the azo pigment represented by the general formula (1) is, for example, 3-formyl-2-naphthol (the following:
1 ) and tetraphenylcyclopentadiene ( 2 below) can be easily synthesized by a dehydration condensation reaction in the presence of a base such as sodium methylate.

Coupler Synthesis Example (Synthesis of Coupler above 3) the 3-formyl-2-naphthol in a flask 5.0 g (0.02
9 mol) and 11.0 g of tetraphenylsoclopentadiene (0.
030 mol) and 500 ml ethanol and 0.07 g (0.001 mol)
Was charged and the mixture was heated to reflux for 2 hours.

The mixture was allowed to cool, collected by filtration, and washed with ethanol.

Yield 12.7 g In the azo pigment represented by the above general formula (1) of the present invention, the corresponding amine is diazotized by a conventional method and coupled with the corresponding coupler in the presence of an alkali in an aqueous system, or the diazonium salt is converted to a borofluoride salt or After converting to zinc chloride double salt, etc.,
In an organic solvent such as N, N-dimethylformamide or dimethylsulfoxide, sodium acetate, triethylamine, N
-Easily synthesized by coupling with a corresponding coupler in the presence of a base such as methylmorpholine.

The electrophotographic photosensitive member of the present invention has a photosensitive layer containing an azo pigment represented by the general formula (1) on a conductor support.

The form of the photosensitive layer may be any known form, but a photosensitive layer containing the azo pigment represented by the general formula (1) is used as a charge generating layer, and a charge transporting layer containing a charge transporting substance is added to the photosensitive layer. A laminated function-separated photosensitive layer is particularly preferable.

In this case, the charge generation layer can be formed by applying a coating solution in which the above-mentioned azo pigment is dispersed as a charge generation substance together with a binder resin in a suitable solvent onto a conductive support by a known method. The film thickness is, for example, 5 μm or less, preferably 0.01 to 1 μm.

The binder resin used at this time is widely selected from insulating resins or organic photoconductive polymers, but polyvinyl butyral, polyvinyl benzal, polyarylate, polycarbonate, polyester, phenoxy resin, cellulosic resin, acrylic resin, polyurethane. Etc., and the amount used is 80 in terms of the content rate in the charge generation layer.
It is not more than 40% by weight, preferably not more than 40% by weight.

Further, the solvent used is preferably selected from those which dissolve the above-mentioned resin and do not dissolve the charge transport layer and the undercoat layer described later.

Specifically, tetrahydrofuran, ethers such as 1,4-dioxane, cyclohexanone, ketones such as methyl ethyl ketone, amides such as N, N-dimethylformamide, methyl acetate, esters such as ethyl acetate,
Aromatics such as toluene, xylene, chlorobenzene,
Examples thereof include alcohols such as methanol, ethanol and 2-propanol, and aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride and trichloroethylene.

The charge transport layer is laminated on or under the charge generation layer and has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting the charge carriers.

The charge-transporting layer is formed by dissolving a charge-transporting substance in a solvent and coating it together with a suitable binder resin if necessary. The film thickness is generally 5-40 μm, especially 15-30
μm is preferred.

The charge transport material includes an electron transport material and a hole transport material, and examples of the electron transport material include 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, chloranil and tetra. Examples thereof include electron-withdrawing substances such as cyanoquinodimethane and polymers obtained by polymerizing these electron-withdrawing substances.

Examples of the hole-transporting substance include polycyclic aromatic compounds such as pyrene and anthracene, carbazole-based, indole-based, imidazole-based, oxazole-based, thiazole-based, oxadiazole-based, pyrazole-based, pyrazoline-based, thiadiazole-based and triazole-based compounds Heterocyclic compounds, such as p
-Diethylaminobenzaldehyde-N, N-diphenylhydrazone, hydrazone compounds such as N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, α-phenyl-4′-N, N-diphenylaminostilbene, 5- [4- (di-p-tolylamino) benzylidene] -5H-dibenzo [a, d] cycloheptane and other styryl compounds, benzidine compounds, triarylmethane compounds, triphenylamine or groups consisting of these compounds Polymers having a main chain or a side chain (for example, poly-N-vinylcarbazole, polyvinylanthracene, etc.) can be mentioned.

In addition to these organic charge transport materials, inorganic materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can also be used.

Further, these charge transport substances can be used alone or in combination of two or more.

When the charge transport material does not have film-forming properties, a suitable binder resin can be used, and specifically, acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, polyacrylamide, polyamide, Examples thereof include insulating resins such as chlorinated rubber and organic photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene.

As the conductive support, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, titanium, nickel,
Indium, gold, platinum or the like can be used. In addition, plastics formed by coating these metals or alloys by a vacuum deposition method (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate,
Acrylic resin, etc. or conductive particles (eg carbon black, silver particles, etc.) coated on a plastic or metal support with a suitable binder resin, or plastic or paper impregnated with conductive particles should be used. You can

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer.

The thickness of the undercoat layer is 5 μm or less, preferably 0.1 to 3 μm
Is appropriate. The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66, nylon 610, copolymer nylon, alkoxymethylated nylon, etc.), polyurethane, aluminum oxide and the like.

Another specific example of the present invention is an electrophotographic photosensitive member containing the azo pigment represented by the general formula (1) and a charge transport substance in the same layer. At this time, a charge transfer complex composed of poly-N-vinylcarbazole and trinitrofluorenone can be used as the charge transport material.

The electrophotographic photosensitive member of this example can be formed by coating and drying a liquid in which an azo pigment represented by the general formula (1) and a charge transporting substance are dispersed in an appropriate resin solution.

The crystal form of the azo pigment represented by the general formula (1) used in any electrophotographic photoreceptor may be amorphous or crystalline, and, if necessary, the general formula (1) It is also possible to use two or more kinds of the azo pigments shown in (3) or a known charge generating substance in combination.

The electrophotographic photoreceptor of the present invention can be widely used not only in electrophotographic copying machines but also in electrophotographic application fields such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

[Examples] Examples 1 to 18 A solution prepared by dissolving 5 g of methoxymethylated nylon (average molecular weight 32,000) and 10 g of alcohol-soluble copolymerized nylon (average molecular weight 29,000) on 95 g of methanol on an aluminum support was prepared. A subbing layer having a thickness of 1 μm after coating and drying with a Meyer bar was provided.

Next, 5 g of Exemplified Pigment (1-1) was added to 95 ml of cyclohexanone.
2 g of butyral resin (degree of butyralization: 63 mol%) was dissolved in the solution and dispersed in a sand mill for 20 hours. The film thickness after drying this dispersion is 0.2μ on the undercoat layer formed earlier.
The charge generation layer was formed by coating with a Meyer bar so as to have a thickness of m and drying.

Next, 5 g of the hydrazone compound of the following structural formula Dissolve 5 g of polymethylmethacrylate (number average molecular weight 100,000) in 40 ml of chlorobenzene, apply this on the charge generation layer with a Meyer bar so that the film thickness after drying is 20 μm, and dry to form the charge transport layer. Then, the electrophotographic photosensitive member of Example 1 was formed.

The following exemplary pigments were used in place of the exemplary pigment (1-1), and other conditions were the same as in Example 1 to prepare electrophotographic photoreceptors corresponding to Examples 2 to 18.

The electrophotographic photoconductor thus prepared was subjected to -5K by using an electrostatic copying paper tester (Model SP-428 manufactured by Kawaguchi Electric Co., Ltd.).
It was negatively charged by V corona discharge, held for 1 second in a dark place, and then exposed to light having an illuminance of 10 lux using a halogen lamp to evaluate the charging characteristics.

As the charging characteristics, the surface potential (V ₀ ) and the exposure dose (E1 / 2) required for the surface potential after being left in the dark to decay to 1/2 were measured. The results are shown.

Comparative Examples 1 and 2 Electrophotographic photoreceptors corresponding to Comparative Examples 1 and 2 were prepared in the same manner as in Example 1 except that the azo pigment having the following structural formula was used, and the charging characteristics were evaluated in the same manner as in Example 1. did. The results are shown.

(Comparative Example 1) Comparative pigment (1) V ₀ : -700V E1 / 2: 6.2lux · sec (Comparative Example 2) Comparative pigment (2) V ₀ : −680V E1 / 2: 7.4lux · sec From these results, it can be seen that each of the electrophotographic photosensitive members of the present invention has sufficient charging ability and excellent sensitivity.

Examples 19 to 21 Using the electrophotographic photoreceptors prepared in Examples 1, 2 and 3, the changes in the dark part potential and the light part potential during repeated use were measured.

As a method, -6.5KV corona charger, exposure optical system,
The electrophotographic photosensitive member was attached to a cylinder of an electrophotographic copying machine equipped with a developing device, a transfer charger, a static elimination exposure optical system and a cleaner.

This copying machine is configured so that an image can be obtained on a transfer sheet as the cylinder is driven.

Using this copier, the initial dark part potential V _D and light part potential _VL were set to around -700 V and -200 V, respectively, and the fluctuation amount ΔV _D of the dark part potential and the bright part potential when repeatedly used 5000 times. Variation Δ
V _L was measured. The results are shown.

In addition, the negative symbol in the variation amount of the potential represents a decrease in the absolute value of the potential, and the positive symbol represents an increase in the absolute value of the potential.

Comparative Examples 3 and 4 The electrophotographic photosensitive members prepared in Comparative Examples 1 and 2 were used in Example 19
The same method was used to measure the amount of potential fluctuation during repeated use.
The results are shown.

From the results of Examples 19 to 21 and Comparative Examples 3 and 4, it can be seen that the electrophotographic photosensitive member of the present invention has little potential fluctuation during repeated use.

Example 22 An undercoat layer of polyvinyl alcohol having a thickness of 0.5 μm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film.

A dispersion liquid of the pigment of Exemplified Pigment (1-3) used in Example 3 was applied and dried with a Meyer bar to form a charge generation layer having a thickness of 0.2 μm.

Then, 5g of styryl compound of the following structural formula A solution of 5 g of polycarbonate (number average molecular weight: 55,000) in 40 ml of tetrahydrofuran was applied on the charge generation layer and dried to form a charge transport layer having a thickness of 20 μm.

The charging characteristics and durability characteristics of the electrophotographic photosensitive member thus prepared were evaluated by the same methods as in Examples 1 and 19. The results are shown.

V ₀ : −690V E1 / 2: 3.5lux · sec ΔV _D : −5V ΔV _L : + 20V Example 23 The charge generation layer and the charge transport layer of the electrophotographic photosensitive member prepared in Example 22 were coated in reverse order. Create an electrophotographic photoreceptor,
The charging property was evaluated by the same method as in Example 1. However, the charging was positive.

The results are shown.

V ₀ : + 695V E1 / 2: 6.2lux · sec Example 24 On the charge generation layer prepared in Example 15, 5 g of 2,4,7-trinitro-9-fluorenone and poly-4,4′-dioxy were added. Diphenyl-2,2-propane carbonate (molecular weight 300,000) 5
A coating solution prepared by dissolving g in tetrahydrofuran (50 ml) was applied so that the film thickness after drying was 18 μm and dried to form a charge transport layer.

The charging characteristics of the electrophotographic photosensitive member thus prepared were measured in the same manner as in Example 1.

However, the charging was positive. The results are shown.

V ₀ : + 700V E1 / 2: 5.1lux · sec Example 25 0.5 g of the exemplified pigment (3-2) was dispersed with 9.5 g of cyclohexanone in a paint shaker for 5 hours. Example 1 here
A solution prepared by dissolving 5 g of the charge transport material used in 1) and 5 g of polycarbonate in 40 g of tetrahydrofuran was added, and the mixture was further shaken for 1 hour. The coating solution thus prepared was coated on an aluminum support with a Meyer bar and dried to form a photosensitive layer having a thickness of 20 μm.

The charging characteristics of the electrophotographic photosensitive member thus prepared were evaluated in the same manner as in Example 1. However, the charging was positive.

V ₀ : + 705V E1 / 2: 4.9lux · sec [Advantages of the Invention] In the electrophotographic photoreceptor of the present invention, by using an azo pigment having a specific structure in the photosensitive layer, the generation efficiency of charge carriers inside the photosensitive layer is improved. Either or both of the injection efficiencies are improved, and the sensitivity and the potential stability during repeated use are excellent.

Claims (1)

[Claims] 1. An electrophotographic photoreceptor having a photosensitive layer containing an azo pigment on a conductive support, wherein the azo pigment is an azo pigment represented by the following general formula (1). . In the formula, Ar represents an aromatic hydrocarbon group or a heterocyclic group which may have a substituent which may be bonded via a bonding group, and X represents a substituent which is condensed with a benzene ring. Represents a residue necessary for forming an aromatic hydrocarbon ring or an aromatic heterocycle, R represents an alkyl group or an aryl group, m is an integer of 0 or 1, and n is 1, 2 or It is an integer of 3.