JPH0217017B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a laminated electrophotographic photoreceptor characterized in that a layer of an acceptor organic substance and a layer in which a donor low-molecular substance is molecularly dispersed in a resin are laminated on a conductive support. Regarding. BACKGROUND ART Conventionally, electrophotographic photoreceptors of the type in which a charge generation layer and a charge transport layer are laminated on a conductive support are known. However, with this type of laminated photoreceptor, sufficient sensitivity has not yet been obtained, and the bright area potential is The disadvantage was that the dark area potential fluctuated greatly. OBJECT OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor that eliminates the above-mentioned drawbacks. Structure and Effects of the Invention The photoreceptor of the present invention has a layer of an acceptor organic substance and a layer in which a low molecular weight acceptor substance is molecularly dispersed in a resin on a conductive support. This method is characterized in that a thin layer of a charge transfer complex is formed in the process and used as a charge generation layer. In addition, in this specification, "acceptor organic substance"
refers to either an acceptor-based low-molecular substance, an acceptor-based low-molecular substance molecularly dispersed in a polymer matrix, or an acceptor-based high-molecular substance. The reason why the sensitivity of multilayer photoreceptors, in which the photosensitive layer is functionally separated into a charge transport layer and a charge transport layer, is not improved is that there are many carrier traps generated by exposure to light in the charge generating material. Possible reasons include that the holes and electrons thus generated cannot move efficiently, and that carriers are not efficiently injected from the charge generation layer to the charge transport layer. At the same time, the aforementioned inefficiency of carrier movement has an important effect on fluctuations in bright area potential and dark area potential when repeatedly charging and exposing the photoreceptor immediately after irradiating it with strong exposure light. The present inventors formed a thin layer of a charge transfer complex at the interface between the acceptor substance layer and the donor substance layer through the interaction of the two substances, and used this thin layer as a charge generation layer. Holes and electrons generated during exposure move efficiently through the donor material layer and acceptor material layer, respectively, without being trapped within this thin layer, resulting in high sensitivity and the ability to irradiate the photoreceptor with intense light at the same time. It has been found that it is possible to reduce fluctuations in bright area potential and dark area potential when repeated charging and exposure are performed immediately after. In this specification, the term "charge transfer complex" refers to an organic molecule complex DA consisting of an electron donor D and an electron acceptor A, which obtains stabilizing energy by transferring some electrons from D to A. Whether or not a charge transfer complex has been formed can be easily confirmed by whether a spectroscopic charge transfer absorption band is observed. In general, in terms of material selection, it is better to find a compound in which the ionization potential I _p of D is small and the electron affinity E _A of A is large, and also to create a state with good molecular and solid structure overlap. I can say that. D is a system in which a donor-type low-molecular substance is molecularly dispersed in a resin, and A is a system in which a donor-type low-molecular substance is molecularly dispersed in a resin; It is one of the following. The materials used to create the laminated electrophotographic photoreceptor of the present invention include, for example, 1,3,5-tricyanobenzene,
m-dinitrobenzene, 1,2,4,5-tetracyanobenzene, tetrachlorophthalic anhydride,
Maleic anhydride, 2,4,6-trinitrotoluene, 1,3,5-trinitrobenzene, p-benzoquinone, pyromellitic anhydride, chloro-p-
Benzoquinone, 1,2-dicarboxy-1,2-
Dicyanoethylene, 2,3-dichloro-p-benzoquinone, 2,5-dichloro-p-benzoquinone, 2,6-dichloro-p-benzoquinone, 2,
4,7-trinitro-9-fluorenone, trichloro-p-benzoquinone, p-iodoanil, p
-bromanil, p-chloranil, o-chloranil, o-bromanil, tetracyano-p-benzoquinone, tetracyano-p-quinodimethane, 2,
3-dicyano-p-benzoquinone, 2,6-dinitro-p-benzoquinone, tetracyanoethylene, 2,3-dichloro-5,6-dicyano-p-
Examples include benzoquinone. Furthermore, these acceptor-based low-molecular substances may be used by being molecularly dispersed in a polymer matrix, and the blending polymers used in this case include, for example, polyarylate resins, polysulfone resins, polyamide resins, acrylic resins, Acrylonitrile resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenolic resin, epoxy resin, polyester resin, alkyd resin, polycarbonate, polyurethane, or copolymer resin containing two or more repeating units of these resins, such as styrene- Examples include butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, and the like. Further, examples of the acceptor polymer substance include polyvinyl butyral, maleic acid resin, ketone resin, cellulose ester, etc., and these may be used alone or in combination of two or more. On the other hand, as donor low molecular weight substances, pyrene,
N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N-phenylhydrazino 3-methylidene-9-ethylcarbazole,
N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-10-ethylphenothiazine, N,N-diphenylhydrazino 3-
Methyldene-10-ethylphenoxazine, p-diethylaminobenzaldehyde-N,N-diphenylhydrazone, p-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone, p-pyrrolidinylbenzaldehyde-N,
Hydrazones such as N-diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde-N,N-diphenylhydrazone, p-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone, 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, 1-[pyridyl(2)]-3-(p-diethylaminostyryl)-5
-(p-diethylaminophenyl)pyrazoline,
1-[6-methoxy-pyridyl (2)]-3-(p-
diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[pyridyl(3)]-3-(p-diethylaminostyryl)-5
-(p-diethylaminophenyl)pyrazoline,
1-[Lepidil (2)]-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)
Pyrazoline, 1-[pyrazyl(2)]-3-(p-diethylaminostyryl)-4-methyl-5-(p-
diethylaminophenyl)pyrazoline, 1-[pyridyl(2)]-3-(α-methyl-p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-phenyl-3-(p-diethylaminostyryl) )-4-methyl-5-(p-
diethylaminophenyl) pyrazoline, 1-phenyl-3-(α-benzyl-p-diethylaminostyryl)-5-(p-diethylaminophenyl)
Pyrazolines such as pyrazoline and spiropyrazoline, 2-(p-diethylaminostyryl)-6-diethylaminobenzoxazole, 2-(P-diethylaminophenyl)-4-(p-dimethylaminophenyl)-5-(2-chlorophenyl) ) Oxazole compounds such as oxazole, thiazole compounds such as 2-(p-diethylaminostyryl)-6-diethylaminobenzothiazole, triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane,
1,1-bis(4-N,N-diethylamino-2
-methylphenyl)heptane, 1,1,2,2-
Tetrakis (4-N,N-dimethylamino-2-
Materials selected from polyarylalkanes such as methylphenyl)ethane, triphenylamine, and the like can be used. Further, these donor-like low molecular weight substances can be used alone or in combination of two or more. Furthermore, examples of resins that can be used for molecularly dispersing the above-mentioned donor low molecular weight substances include acrylic resin polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene, copolymer, polyvinyl butyral, and polyvinyl formal. , polysulfone, polyacrylamide, polyamide, insulating resin such as chlorinated rubber, or polystyrene, polymethylstyrene, polydimethylaminostyrene, polyvinylcarbazole, polycarbasylethyl vinyl ether, poly-2-vinylpyridine, poly-4-vinyl Mention may be made of organic photoconductive polymers such as pyridine, poly-2-methyl-5-vinylpyridine, polynaphthylmethylglutamate, polyvinylnaphthalene, polyvinylanthracene, polyvinylpyrene, polyvinylphenylanthracene, polyacenaphthalene. FIG. 1 of the accompanying drawings shows a cross-sectional view of a laminated photoreceptor of the present invention coated on the surface of a conductive layer 1. In this example, a layer 2 made of an acceptor organic substance is electrically connected to a layer 4 made of a donor polymer substance, and a charge transfer complex is formed at an interface 3 between these layers. At this time, by performing exposure in the presence of negative corona charging, holes and electrons of the charge carriers generated at the interface 3 are efficiently injected into the layer 4 and the layer 2, respectively. FIG. 2 shows another example of the laminated photoreceptor of the present invention. In this example, layer 4 and layer 2 are stacked in a reversed manner compared to FIG. 1, and are used for positive corona charging. A photosensitive layer having such a laminated structure of a donor layer and an acceptor layer is provided on a substrate having a conductive layer. As the substrate having the conductive layer, materials that are themselves conductive can be used, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, and platinum. In addition, plastics (e.g., polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, (acrylic resin, polyethylene fluoride, etc.)
A substrate in which conductive particles (e.g., carbon black, silver particles, etc.) are coated on plastic together with a suitable binder, a substrate in which plastic or paper is impregnated with conductive particles, a plastic containing a conductive polymer, etc. can be used. . A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer. The subbing layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon
610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. The thickness of the undercoat layer is 0.1 micron to 5 micron.
Preferably, 0.5 micron to 3 micron is appropriate. The organic solvents used when forming the undercoat layer, donor layer, acceptor layer, etc. as described above are as follows:
Alcohols such as methanol, ethanol, isopropanol, ketones such as acetone, methyl ethyl ketone, cyclohexanone, N,N-
Amides such as dimethylformamide and N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, chloroform, methylene chloride, and Examples include aliphatic halogenated hydrocarbons such as chloroethylene, carbon tetrachloride, and trichloroethylene, and aromatics such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzene. The organic solvent used to form each layer here naturally varies depending on the type of substance used, and when forming an undercoat layer, the solvent used for the donor layer or acceptor layer may It is preferable to select from those that do not dissolve. What is particularly ingenious about the laminated photoreceptor of the present invention is the method of forming a charge transfer complex as thin as possible at the interface between the donor and acceptor layers. In other words, by efficiently forming a thin layer of charge transfer complex at the interface between the donor layer and acceptor layer, the sensitivity is increased and at the same time, the sensitivity is improved when the photoreceptor is repeatedly charged and exposed immediately after being exposed to strong light. This has succeeded in improving the characteristics of potential changes. Specifically, a first layer of donor or acceptor coating is first formed on the conductive layer by the coating method described below, dried, and then a second layer is formed.
If the first layer is a donor layer, an acceptor substance is used as the layer, and if the first layer is an acceptor layer, the donor substance is dissolved in a solvent and laminated. However, it is necessary to select a solvent for the second layer that also dissolves the substance used for the first layer. Then, the moment the second layer is applied, a color change can be observed at the interface between the first layer and the second layer, and a thin layer of the charge transfer complex is immediately formed. In addition, in order to confirm that a charge transfer complex is formed due to the interaction between the donor substance and the acceptor organic substance as described above, a coating film is formed using a coating liquid containing a mixture of both substances. It is sufficient to confirm that characteristic strong absorption based on charge transfer appears in the visible light region of the absorption spectrum. At this time, depending on the selection of the donor substance and acceptor organic substance, a sufficiently strong charge transfer absorption band may not appear in the visible light region, and the sensitivity when such substances are stacked will naturally be affected. It wasn't good. Coating can be carried out using coating methods such as dip coating, spray coating, spinner coating, bead coating, Meyer bar coating, blade coating, roller coating, and curtain coating. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying at a temperature of 30℃ to 200℃ for 5 minutes to 2
It can be carried out stationary or under blown air for a period of time. 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 and electrophotographic plate making systems. According to the present invention, it is possible to provide a highly sensitive electrophotographic photoreceptor, and the variation in bright area potential and dark area potential when repeatedly charging and exposing the photoreceptor immediately after irradiating it with strong light is reduced. It has the advantage of being small. Hereinafter, the present invention will be explained according to examples. Example 1 Polycarbonate (trade name Teijin Panlite L-1250 manufactured by Teijin Ltd.) 3 g 2,4,7-trinitro-9-fluorenone
3 g was dissolved in 30 c.c. of tetrahydrofuran. This coating solution was applied onto an aluminum sheet using a Mayer bar to give a dry film thickness of 8 microns to form an acceptor layer. Next, a monochloromethane mixture of hydrazone of the following structural formula (1) and a styrene-acrylic resin (trade name: MS-200, manufactured by Nippon Steel Chemical Co., Ltd.) as a binder at a weight ratio of 1:1 was prepared. Apply a 20% benzene solution to the charge generation layer using a Mayer bar until the dry film thickness is adjusted.
A donor layer was formed by coating to a thickness of 12 microns, and a photosensitive layer having a two-layer structure was prepared and designated as Sample 1. On the other hand, as a comparison sample, a functionally separated photoreceptor having a charge generation layer and a charge transfer layer laminated in this order on a conductive support was prepared as follows. In other words, put the following disazo pigment (2) in a 50 c.c. glass bottle.
4.1 g was taken, 18.1 g of cyclohexanone and 20 ml of glass beads were added thereto, and the mixture was dispersed for 4 hours using a red devil. To this dispersion, 4.4 g of a 9.1% by weight solution of polyvinyl butyral (trade name: BM-2, manufactured by Sekisui Chemical Co., Ltd.) in a 1:1 weight ratio of methyl ethyl ketone: cyclohexanone was added as a binder, and the mixture was further dispersed for 2 hours using a red devil. did. This dispersion was coated onto an aluminum sheet using a Mayer bar so that the dry film thickness was 0.2 microns to form a charge generation layer. Next, a monochloromethane mixture of the hydrazone of the structural formula (1) and a styrene-acrylic resin (product name: MS-200 manufactured by Nippon Steel Chemical Co., Ltd.) as a binder at a weight ratio of 1:1 was prepared. A charge transport layer was formed by applying a 20% by weight benzene solution onto the charge generation layer using a Mayer bar to a dry film thickness of 12 microns. Comparative sample 1 was prepared in this manner. The electrophotographic photoreceptor produced in this way was tested using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd.
The sample was corona-charged using a dynamic method, held in a dark place for 1 second, and then exposed to light for 4 seconds at an illuminance of 5 lux to examine the charging characteristics. As for the charging characteristics, the surface potential and the exposure amount (E1/6) required to attenuate the potential (V ₁ ) when dark decayed for 1 second to 1/6 were measured. Furthermore, as a way to easily express the degree of variation in bright area potential and dark area potential when used repeatedly, a sample that has been subjected to the above measurement once was exposed to a 600 lux fluorescent lamp for 3 times.
After being irradiated for 1 minute and then left in the dark for 1 minute, the potential difference from the first time of V ₁ when exposed to charged light again is △
Let it be represented by V ₁ . The larger the value of ΔV ₁ is, the greater the fluctuations in the bright and dark potentials will be during repeated use. Next, the measurement results for the above photoreceptor will be shown.

[Table] From the above results, it can be seen that Sample 1, which has the layer structure of conductive support-acceptor layer-donor layer, has high sensitivity and small potential fluctuations when intense exposure is applied. On the other hand, it can be seen that Comparative Sample 1, which has a layer structure of conductive support-charge generation layer-charge transport layer, has poor characteristics. This result indicates that there are many traps in the charge generation layer, and the carriers generated by light irradiation cannot move efficiently. Example 2 An aluminum sheet was heated to 180°C on a hot plate, and 1 g of 2,4,7-trinitro-9-fluorenone in a crystalline state was placed on the aluminum sheet.
was taken and melted. Immediately thereafter, the coating was applied to a constant film thickness using a Mayer bar heated to 180°C, and then removed from the hot plate and left to cool rapidly at room temperature to obtain a transparent amorphous state with a thickness of 1 micron. Ta. Further, a 12 micron thick hydrazone having the structural formula (1) was laminated thereon in the same manner as in Example 1 to prepare Sample 2, and the charging characteristics were examined, and the following results were obtained.

[Table] Example 3 Polyamide (product name: CM-8000 manufactured by Toray Industries, Inc./Torezin manufactured by Teikoku Kagaku Co., Ltd. =
A 2% methanol solution (1/1 weight ratio) was applied onto an aluminum sheet using a Mayer bar to a dry film thickness of 0.5 microns to form an undercoat layer. Next, hydrazone of structural formula (3) and styrene-acrylic as a binder Resin (Product name: MS- manufactured by Nippon Steel Chemical Co., Ltd.)
200) in a 1:1 weight ratio, and then apply a 20% by weight solution of monochlorobenzene on the previous subbing layer using a Mayer bar to a dry film thickness of 12 microns to form a donor layer. did. Next, 3 g of polycarbonate (trade name: Teijin Panlite L-1250, manufactured by Teijin Ltd.) and 3 g of maleic anhydride were dissolved in 30 c.c. of tetrahydrofuran. This coating solution was applied onto the polystyrene layer using a Mayer bar so that the dry film thickness was 8 microns. Sample 3
The charging characteristics were investigated in the same manner as in Example 1. However, the charging polarity at this time was as follows. The results are shown in the table below.

【table】 [Brief explanation of drawings]

1 and 2 are cross-sectional views of an example of the electrophotographic photoreceptor of the present invention. DESCRIPTION OF SYMBOLS 1... Conductive substrate, 2... Acceptor layer, 3... Charge transfer complex layer, 4... Donor layer.

Claims (1)

[Claims] 1. Forming a thin layer of a charge transfer complex at the interface between the two layers by providing on a conductive support a layer consisting of an acceptor organic substance and a layer in which a donor low-molecular substance is molecularly dispersed in a resin. A laminated electrophotographic photoreceptor featuring: