JPH0345959A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain stable potential characteristics even at the time of repeated uses by incorporating a specified compound in a photosensitive layer. CONSTITUTION:The photosensitive layer contains the compound represented by formula I in which R is an optionally substituted aromatic or heterocyclic group; X is an O or S atom or dicyano-methylene group; (m) is 1, 2, or 3; and (n) 0 or 1. Since this photoconductive compound has a large electron receptive space, it exhibits intermolecular mutual electric charge transfer action between an electron donative part and an electron receptive part in a crystalline state, thus permitting the obtained electrophotographic sensitive body to be high in sensitivity and superior in potential stability even at the time of repeated uses.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor in which a photosensitive layer contains a compound having a specific structure.

[Conventional technology]

Conventionally, inorganic photoconductive substances such as selenium, cadmium sulfide, and zinc oxide have been widely used as electrophotographic photoreceptors. On the other hand, electrophotographic photoreceptors using electroconductive materials include photoconductive polymers typified by poly-N-vinylcarbazole and 2,5-bis(p-diethylaminophenyl)-1,3,4 -Those using low-molecular organic photoconductive substances such as oxadiazole, and furthermore those in which such organic photoconductive substances are combined with various dyes and pigments are known. Electrophotographic photoreceptors using organic photoconductive substances have good film forming properties, can be produced by coating, and have extremely high productivity.
It has the advantage of being able to provide an inexpensive photoreceptor. In addition, it has the advantage that color sensitivity can be freely controlled by selecting the sensitizers used, such as dyes and pigments, and has been extensively studied. In particular, recent developments have led to the development of functionally separated photoreceptors in which a charge generation layer containing an organic photoconductive dye or pigment is laminated with a charge transport layer containing the aforementioned photoconductive polymer or low-molecular organic conductive substance. Significant improvements have been made in the sensitivity and durability, which were considered to be shortcomings of conventional organic electrophotographic photoreceptors. [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 that exhibits stable potential characteristics during repeated practical use. [Means for Solving the Problems, Effects] The present invention provides an electrophotographic photoreceptor having a photosensitive layer on a biconductive support, wherein the photosensitive layer contains a compound represented by the following general formula (1). It consists of a photographic photoreceptor. In the general formula, R represents an aromatic group or a heterocyclic group which may have a substituent, X represents an oxygen atom, a sulfur atom or a dicyanomethylene group, m is an integer of 1, 2 or 3, and n is 0
or an integer of l. More specifically, aromatic groups include aromatic monocyclic groups or aromatic condensed polycyclic groups such as benzene, naphthalene, anthracene, phenanthrene, pyrene, azulene, and fluorene, and aromatic ketone groups such as benzophenone, fluorenoso, and benzanthro. and their sulfur derivative groups, benzoquinone. Naphthoquinone, 7-nthraquinone, phenanthrenone,
Examples thereof include aromatic quinone groups such as pyrenequinone and their sulfur derivatives, 2disyanomethylene derivative groups, and aromatic amine groups such as triphenylamine, diphenylamine, and diphenylmethylamine. Heterocyclic groups include furan, thiophene, pyrrole, oxazole, thiazole, and imidazole. Pyrazole, pyridine, pyrazine, benzofuran, benzothiophene, indole, benzoxazole, benzthiazole, dibenzofuran. Examples include a heterocyclic group such as dibenzothiophene, carbazole, phenazinephenoxazine 2-acridone, or a heterocyclic group condensed with a benzene ring or an aromatic condensed polycyclic ring. Examples of substituents that the aromatic group or heterocyclic group may have include halogen atoms such as fluorine atom, chlorine atom, and bromine atom; alkyl groups such as methyl, ethyl, and propyl; and flukoxy groups such as methoxy and ethoxy; Examples include a nitro group, a cyano group, and substituted amino groups such as dimethylamino and diethylamino. In the compound represented by general formula (1), especially R is pyrene,
In the case of electron-donating groups such as aromatic condensed polycyclic groups such as perylene, and aromatic amine compounds such as triphenylamine and diphenylamine, good electrophotographic properties such as longer wavelength spectral sensitivity and higher sensitivity can be obtained. It will be done. In electrophotographic photoreceptors, in order to achieve longer wavelength spectral sensitivity, it is necessary to lengthen the absorption spectrum of the charge generating material, and it is necessary to lengthen the wavelength by expanding the 2π electron conjugation system and increasing intermolecular interactions. Are known. Regarding the substituent effect of substituted azobenzene-based compounds, it has been reported that the absorption spectrum becomes longer wavelength as the electron-donating or electron-accepting property of the substituent increases.
This is thought to be due to intramolecular charge transfer interactions via the azo group, which is the π-electron conjugated chain of azobenzene [Gie and Griffiths, "Color and Construction of Organic Molecules", Academic Press, London, 1976] ]. By combining a material with large electron-donating properties and a material with large electron-accepting properties, a significantly longer wavelength is expected. On the other hand, in an electrophotographic photoreceptor, in order to improve sensitivity, it is necessary to increase the generation efficiency of charge carriers, and one of the factors governing the generation efficiency of charge carriers is the dissociation efficiency of charge carriers. It has been reported for phthalocyanine compounds that the local electric field created by ion-adsorbed gas has a large effect on the dissociation efficiency of charge carriers [for example, Journal of Electrophotographic Society, 1987, 2].
Vol. 0, p. 216], local electric fields based on charge transfer interactions between electron-donating and electron-accepting substances are also thought to promote the generation of charge carriers. From the above-mentioned viewpoint, since the photoconductive compound in the present invention has a large part of electron-accepting property, especially when R is electron-donating, the intermolecular charge between the electron-donating part and the electron-accepting part is reduced in the crystal state. It is thought that migration interaction occurs and gives good properties. Representative examples of the compound represented by the general formula (1) used in the present invention are listed below. Basic compound example (1) Compound example (2) Compound example (3) Compound example (4) Compound example (5) Compound example (6) Compound example (7) Compound example (8) Compound example (9) Compound example ( 1 0) Compound Example (11) Compound Example (1 2) Compound Example (1 3) Compound Example (14) Compound Example (15) Compound Example (16) Compound Example (1 7) Compound Example (19) Compound Example (20) ) The compound represented by the general formula (1) (in the case of n = 0, ml) can be easily synthesized by a dehydration condensation reaction between compound ■ and an aldehyde or a dehydration condensation reaction in the presence of an acid or a base, as shown in the reaction formula below. Can be synthesized. The electrophotographic photoreceptor of the present invention has the general formula (
It has a photosensitive layer containing the compound shown in 1). The form of the photosensitive layer may be any known form, but a photosensitive layer containing the compound represented by general formula (1) is used as a charge generation layer, and a charge transport layer containing a charge transport substance is laminated thereon. A functionally separated type photosensitive layer is particularly preferred. The charge generation layer can be formed by coating a coating liquid prepared by dispersing the compound represented by the general formula (1) together with a binder resin in an appropriate solvent on a conductive support by a known method. It is desirable that the thickness of the thin film layer is, for example, 5 ILm or less, preferably 0.1-1 Im. The binder resin used in this case is selected from a wide range of insulating resins or organic photoconductive polymers, including polyvinyl butyral, polyvinylbenzal, polyarylate, polycarbonate, polyester, phenoxy resin, cellulose resin, acrylic resin, urethane resin, etc. Resins are preferably used in an amount of 80% in terms of content in the charge generation layer.
It is not more than 40% by weight, preferably not more than 40% by weight. The solvent used is preferably selected from those that dissolve the resin described above but do not dissolve the charge transport layer or undercoat layer, which will be described later. Specifically, ethers such as tetrahydrofuran, L, 4-dioxane, ketones such as cyclohexanone and methyl ethyl ketone, amides such as N,N-dimethylformamide, esters such as methyl acetate and ethyl acetate, toluene, xylene, Examples include aromatic compounds such as chlorobenzene, 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 above or below the charge generation layer and has the function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them to the surface. The charge transport layer is formed by dissolving a charge transport substance in a solvent together with an appropriate binder resin as necessary and coating the layer, and the film thickness is generally 5 to 40 μm, but 1
5 to 30 gm is preferred. Charge transporting substances include electron transporting substances and regular transporting substances, and 1Ml electron transporting substances include, for example, 2,4,7-dolinitrofluorenone, 2,4,5,7-te)ranitrofluorenone, chloranil, Examples include electron-withdrawing substances such as tetracyanoquinodimethane and polymerized materials of these electron-withdrawing substances. Hole-transporting substances 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, triazole-based compounds, etc. heterocyclic compound, P-
Hydrazone-based compounds such as diethylaminobenzaldehyde-N,N-diphenylhydrazone, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, α-phenyl-4'-N,N-diphenylaminostilbene, 5-[ 4-(p-tolylamino)benzylidene]-58-dibenzo[a, dl Styryl compounds such as cycloheptene, benzidine compounds, triarylmethane compounds, triphenylamine, or groups consisting of these compounds in the main chain or Examples include polymers having side chains (eg, poly-N-vinylcarbazole, polyvinylanthracene, etc.). In addition to these organic charge transport materials, concentrator materials such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide can also be used. Further, these charge transport materials can be used alone or in combination of two or more. When the charge transport material does not have film-forming properties, an appropriate binder resin can be used, and specifically, acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, polyacrylamide, polyamide, Examples 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 is used. Metals or alloys such as aluminum alloys and stainless steel can be used. In addition, such metals or alloys may be coated on plastic or conductive particles (e.g. carbon black, silver particles, etc.) together with a suitable binder resin on a plastic or metal support, or A support such as plastic or paper impregnated with conductive particles can be used. An undercoat layer having barrier and adhesive functions can also be provided between the conductive support and the photosensitive layer. The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alfky dimethylated nylon, etc.), polyurethane, aluminum oxide, and the like. The thickness of the undercoat layer is 5 pm or less, preferably 0.1 to 3 I
Lm is appropriate. Another specific example of the present invention is an electrophotographic photoreceptor containing the compound represented by general formula (1) and a charge transport material in the same layer. At this time, a charge transfer complex consisting of poly-N-vinylcarbazole and trinitrofluorenone can also be used as the charge transport substance. The electrophotographic photoreceptor of this example can be formed by coating and drying a solution in which a compound represented by formula (1) and a charge transporting substance are dispersed in a suitable resin solution. The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines, but also in a wide range of electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making. [Example] Examples 1 to 20 5 g of methoxymethylated nylon (number average molecular weight 32,000) and alcohol-soluble copolymerized nylon (a-average molecular weight 29,000) log were placed on an aluminum support in 9 g of methanol.
A solution dissolved in 5 g was applied using a Mayer bar to form an undercoat layer having a thickness of 1.0 gm after drying. Next, 5 g of the compound of Compound Example (1) was added to a solution prepared by dissolving 2 g of butyral resin (degree of butyralization: 63 mol %) in 95 g of cyclohexanone, and dispersed in a sand mill for 20 hours. This dispersion was applied onto the previously formed undercoating layer using a Mayer bar and dried to form a charge generation layer so that the film thickness after drying was 0.2 gm. Next, 5 g of a hydrazone compound having the following structure and 5 g of polymethyl methacrylate (average molecular weight 10,000) were dissolved in 40 g of chlorobenzene, and this was applied onto the charge generation layer using a Mayer bar and dried to form a charge transport layer of 201 m. ,
An electrophotographic photoreceptor of Example 1 was prepared. Electrophotographic photoreceptors corresponding to Examples 2 to 20 were prepared in exactly the same manner using other compounds in place of Compound Example (1). The electrophotographic photoreceptor thus prepared was tested using an electrostatic copying paper tester (Model 5F-428, manufactured by Kawaguchi Juiki).
The sample was negatively charged by corona discharge at -5 KV, left in the dark for 1 second, and then exposed to light using a noherogen lamp at an illuminance of 10 lux to evaluate charging characteristics. The charging characteristics are 1 surface type level (Vo) and the exposure amount required to attenuate the surface potential to 1/2 after being left in the dark (El/2).
) was measured. Show the results. l (1) 2 (2) 3 (3) 4 (4) 5 (5) 6 (6) 7 (7) 695 2 680 2 705 2 700 7 700 3 700 6 690 4 8 (8) 695 1.99
(9) 710 1.710
(10) 695 1.311
(11) 690 1.812
(12) 700 2.913
(13) 705 2.314
(14) 710 2.515
(15) 715 3.316
(16) 710 2.91
7 (17) 685 4.11
8 (18) 695 7. 219 (19) 700 3.
520 (20) 700 3.
9 From these results, it can be seen that all the electrophotographic photoreceptors of the present invention have sufficient charging ability and excellent sensitivity. Examples 21 to 23 Using the electrophotographic photoreceptor prepared in Example 3, fluctuations in bright area potential and dark area potential during repeated use were measured. The photoreceptor was attached to the cylinder of an electrophotographic copying machine equipped with a -6.5 KV corona charger, an exposure optical system, a developer, a transfer charger, a static elimination exposure optical system, and a cleaner. The initial dark potential (Vo) and light potential (VL) were set around -700V and -200V, respectively, and the dark potential (Vo) and light potential (VL) were used repeatedly 5,000 times.
VL ) was measured. The electrophotographic photoreceptors prepared in Examples 9 and 10 were also evaluated in the same manner. 21 3 705
20022 9 705
20523 10 695
20005 00 80 05 10 10 Example 24 An undercoat layer of polyvinyl alcohol having a thickness of 0.5 ILm was formed on the aluminum surface of an aluminum vapor-deposited polyethylene terephthalate film. A dispersion of the compound of Compound Example (10) used in Example 1O was applied onto this using a Mayer bar so that the film thickness after drying was 0.2 pm, and dried to form a charge generation layer. Next, a solution prepared by dissolving 5 g of a styryl compound represented by the following structural formula and 5 g of polycarbonate (fr weight average molecular weight 55,000) in 40 g of tetrahydrofuran was applied onto the charge generation layer so that the film thickness after drying was 201 Lm. It was dried to form a charge transport layer. The charging characteristics and durability characteristics of the electrophotographic photoreceptor thus prepared were measured in the same manner as in Example 1. Show the results. vo Knee 700V El/2: 1.51ux*sec Example 25 An electrophotographic photoreceptor was prepared by coating and laminating the charge generation layer and charge transport layer of the photoreceptor prepared in Example 24 in the reverse order. The charging characteristics were evaluated in the same manner as above. However, the ll polarity was positive. Show the results. Vo: +680V El/2: 3.2fLuxasec Example 26 2.
4.7-) 5g of Rinitro 9-fluorenone and poly-4
, 5 g of 4'-dioxydiphenyl-2,2-propane carbonate (molecular weight 300,000) was added to 50 g of tetrahydrofuran.
A charge transport layer having a thickness of 18 pm was formed by applying the axillary solution dissolved in g with a Mayer bar and drying. The charging characteristics of the electrophotographic photoreceptor thus prepared were evaluated in the same manner as in Example 1. However, the charging polarity was positive. Vo: +680V El/2: 3. 91 ux* sec Example 27 0.5 g of the compound of Compound Example (10) was dispersed with 9.5 g of cyclohexanone in a paint shaker for 5 hours. A solution in which 5 g of the charge transport material used in the Examples and 5 g of polycarbonate were dissolved in 40 g of tetrahydrofuran was added thereto, and the mixture was further shaken for 1 hour. The prepared coating solution was applied onto an aluminum support using a Meyer bar and dried to a film thickness of 20 ILm.
A photosensitive layer was formed. The charging characteristics of the electrophotographic photoreceptor thus prepared were evaluated in the same manner as in Example 1. However, the charging polarity was positive. vo:+695V El/2:4.3Jlux*sec [Effects of the Invention] The electrophotographic photoreceptor of the present invention has high sensitivity and durability during repeated use by containing the compound represented by general formula (1) in the photosensitive layer. It has the remarkable effect of being excellent in potential stability.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, characterized in that the photosensitive layer contains a compound represented by the following general formula (1). General formula ▲ Numerical formula, chemical formula, table, etc. ▼ (1) In the formula, R represents an aromatic group or a heterocyclic group that may have a substituent, and X represents an oxygen atom, a sulfur atom, or a dicyanomethylene group. where m is an integer of 1, 2 or 3, n is 0
or an integer of 1. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer comprises at least two layers: a charge generation layer containing a compound represented by formula (1) and a charge transport layer.