JPH0435066B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor having a low residual potential. Conventionally, in electrophotographic photoreceptors that use photoconductive substances as photosensitive materials, selenium, zinc oxide,
Inorganic conductive materials such as titanium oxide and cadmium sulfide have been mainly used. However, many of these are highly toxic,
There are also problems with the method of disposal. On the other hand, photosensitive materials using organic photoconductive compounds are generally less toxic than those using inorganic photoconductive substances, and are also transparent, flexible, lightweight, and
Since it is advantageous in terms of surface smoothness and cost, it has been widely studied and put into practical use in recent years. Composite photoreceptors, which separate the functions of charge generation and transport, have been rapidly gaining popularity in recent years because they can significantly improve sensitivity, which was a major drawback of conventional photoreceptors using organic photoconductive compounds. progress is being made. When these composite photoreceptors are applied to an electrophotographic device using the Carlson method, an electrostatic latent image is first formed on the surface of the photoreceptor, and then developed with a developer commonly called a toner that is charged with opposite signs. The toner image can be transferred and fixed to another substrate, such as paper, to obtain a copy. In this method, if the residual potential of the photoreceptor is high during development, unnecessary toner will also adhere to the background area, causing so-called background staining and deteriorating image quality. In order to prevent such skin stains, the present invention
An object of the present invention is to provide an electrophotographic photoreceptor with a low residual potential. That is, the present invention provides an electrophotographic photoreceptor having a conductive layer, a charge generation layer containing an organic pigment that generates charges, and charge retention and transport functions, in which the charge transport layer has the general formula (). (wherein R represents hydrogen, an alkyl group, a hydroxyl group, or a carboxyl group) or a hydrate thereof. The materials used in the electrophotographic photoreceptor of the present invention will be described in detail below. First, the charge-generating organic pigments contained in the charge generation layer include azoxybenzene-based, disazo-based, trisazo-based, benzimidazole-based, polycyclic quinone-based, indigoid-based, quinacridone-based, phthalocyanine-based, perylene-based, and methine-based pigments. Pigments known to generate electric charges, such as those based on pigments, can be used. These pigments are described, for example, in Japanese Patent Application Laid-Open No. 47-37544.
Publication No. 18543, Japanese Patent Publication No. 18543, Japanese Patent Publication No. 1854-
Publication No. 18544, Japanese Unexamined Patent Publication No. 48-43942, Japanese Unexamined Patent Publication No. 1973
-70538 Publication, JP-A-49-1231, JP-A-Sho
It is disclosed in JP-A-49-105536, JP-A-50-75214, JP-A-50-92738, etc. In addition to these, any organic pigment that generates charge carriers upon irradiation with light can be used. Charge transport materials that are the main components of the charge transport layer include polymer compounds such as poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylindoquinoxaline, polyvinylbenzothiophene, and polyvinylanthracene. , polyvinylacridine, polyvinylpyrazoline, etc., and low molecular weight compounds such as fluorene, fluorenone, 2,7-dinitro-9-fluorenone, 2,4,7-trinitro-
9-fluorenone, 4H-indeno(1,2,6)
Thiophen-4-one, 3,7-dinitro-dibenzothiophene-5-oxide, 1-promprene, 2-phenylpyrene, carbazole, 3-
Phenylcarbazole, 2-phenylindole, 2-phenylnaphthalene, oxadiazole, oxatriazole, 1-phenyl-3-
(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline, 2-phenyl-4-(4-diethylaminophenyl)-5-phenyloxazole, triphenylamine, imidazole, chrysene, tetraphene, acridene,
There are derivatives of these. Further, additives such as a binder, a plasticizer, a fluidity imparting agent, a pin-pole inhibitor, etc., which are commonly used in electrophotographic photoreceptors, can be used in the charge generation layer and the charge transport layer. As a binder, silicone resin, polyamide, polyurethane, polyester,
epoxy resin, polyketone, polycarbonate,
Examples include polystyrene, polymethyl methacrylate, and polyacrylamide. Furthermore, thermosetting and photocuring resins that are crosslinked by heat and/or light can also be used. In any case, there are no particular limitations as long as the resin is insulative and has a film-forming ability in a normal state, or a resin that can be cured by heat and/or light to form a film. Examples of the plasticizer include halogenated paraffin, dimethylnaphthalene, and dibutyl phthalate. Fluidity imparting agents include Modaflow (manufactured by Monsanto Chemical Company) and Acronal.
4F (manufactured by BASF), etc., and pinpole inhibitors include benzoin, dimethyl terephthalate, etc. These may be selected and used as appropriate, and the amount thereof may be determined as appropriate. In the charge generation layer, components other than the organic pigment include the binder, plasticizer, additive, etc., and the binder is used in an amount of 300% by weight or less based on the organic pigment. If it exceeds 300% by weight, electrophotographic properties will deteriorate. The plasticizer is preferably used in an amount of 5% by weight or less based on the organic pigment. Other additives may be used in an amount of 3% by weight or less. Examples of the compound represented by the general formula () or a hydrate thereof to be added to the charge transport layer of the present invention include 2,4-(1H,3H)-pyrimidinethione (uracil), 2,6-dioxo-1, 2,3,6-
Examples include tetrahydro-4-pyrimidinecarboxylic acid (orotic acid), 4-hydroxyuracil, 4-methyluracil, 4-ethyluracil, and hydrates thereof. The compound represented by the general formula () or its hydrate is added in an amount of 0.001 to 15% by weight, preferably 0.5 to 5% by weight, in the charge transport layer. When the compound represented by the general formula () or its hydrate is less than 0.001% by weight, the effect of lowering the residual potential tends to be reduced, and when it exceeds 15% by weight, the charging property tends to decrease. In the charge transport layer, a binder may be used in addition to the charge transport substance and the compound represented by the general formula () or a hydrate thereof. If the charge transport substance is a polymer compound, it is not necessary to use a binder, but
The binder may be used in an amount of 400% by weight or less based on the polymer compound. If it exceeds 400% by weight, electrophotographic properties will deteriorate. Further, when a low molecular weight compound is used as the charge transport material, the binder is used in an amount of 30 to 400% by weight based on the low molecular weight compound. 30
If it is less than 400% by weight, it tends to be difficult to form a charge transport layer, and if it exceeds 400% by weight, electrophotographic properties tend to deteriorate. The plasticizer and additives are each used in an amount of 5% by weight or less based on the charge transport material. In the present invention, the conductive layer is a conductive material such as paper or plastic film treated for conductivity, a plastic film laminated with metal foil such as aluminum, or a metal plate. The electrophotographic photoreceptor of the present invention is preferably one in which a charge generation layer is formed on a conductive layer and a charge transport layer is formed thereon, but the charge generation layer and the charge transport layer may be reversed. good. The thickness of the charge generation layer is
The thickness is preferably 0.01 to 10 μm, preferably 0.2 to 5 μm.
If it is less than 0.01 μm, it will be difficult to uniformly form the charge generation layer, and if it exceeds 10 μm, the electrophotographic properties will deteriorate. In addition, the thickness of the charge transport layer is 5 to 50 μm,
Preferably it is 8 to 20 μm. If the diameter is less than 5 μm, the initial potential is low, and if it exceeds 50 μm, the apparent sensitivity decreases. To form the charge generation layer and the charge transport layer, the components of each layer are uniformly dissolved or dispersed in a ketone solvent such as acetone or methyl ethyl ketone, an ether solvent such as tetrahydrofuran, or an aromatic solvent such as toluene or xylene. This can be done by subsequently coating the conductive layer and drying it. The electrophotographic photoreceptor of the present invention may further have a thin adhesive layer or barrier layer immediately above the conductive layer, and a protective layer such as silicone may be provided on the surface. In the copying method using the electrophotographic photoreceptor of the present invention, as in the conventional method, the surface is charged and exposed, then developed, and the image is transferred and fixed onto plain paper. The electrophotographic photoreceptor of the present invention has a low residual potential and thus provides images of good quality without background stains. Next, Examples and Comparative Examples related to the present invention will be shown. Each material used in the examples below is listed below.
The numbers in parentheses indicate abbreviations. (1) Organic pigment that generates charge Phthalocyanine type: Fastogen Blue FGF (FGF) [Dainippon Ink & Chemicals Co., Ltd. trade name] (2) Charge transport substance 2-(p-diethylamino)phenyl-4-(p
-diethylamino)phenyl-5-(o-chloro)
Phenyl-1,3-oxazole (OXZ) (3) Binder Γ Silicone varnish: KR-255 (non-volatile content 50
%) [Product name of Shin-Etsu Chemical Co., Ltd.] Γ Polyester: Byron 200 [Product name of Toyobo Co., Ltd.] Γ Polycarbonate: Panlite L-1250 [Product name of Teijin Kasei Co., Ltd.] (4) In the present invention A compound represented by the general formula () added to the charge transport layer Γ orotic acid [Wako Pure Chemical Industries, Ltd.] Γ orotic acid hydrate [same as above] Γ uracil [same as above] Comparative example 1 FGF2.5g, silicone 5.0 g of water varnish and 92.5 g of tetrahydrofuran were kneaded for 8 hours using a ball mill (3-inch pot mill manufactured by Nihon Kagaku Togyo Co., Ltd.).
The obtained pigment dispersion was applied onto an aluminum plate (conductor) using an applicator and dried at 90° C. for 15 minutes to form a charge generation layer with a thickness of 1 μm. Next, 10 g of OXZ and 10 g of polyester were dissolved in 80 g of tetrahydrofuran. This solution was applied onto the charge generation layer using an applicator and dried at 90° C. for 20 minutes to form a charge transport layer with a thickness of 15 μm to obtain an electrophotographic photoreceptor. Comparative Example 2 5 g of OXZ and 15 g of polycarbonate were dissolved in 80 g of methylene chloride. This solution was applied onto the charge generation layer prepared in Comparative Example 1 using an applicator and dried at 100° C. for 30 minutes to form a charge transport layer with a thickness of 15 μm to obtain an electrophotographic photoreceptor. Examples 1 to 5 A charge transport layer having the composition shown in Table 1 was laminated on the charge generation layer prepared in Comparative Example 1 in the same manner as in Comparative Examples 1 to 2. Table 1 also shows the results of measuring the electrophotographic properties of the obtained electrophotographic photoreceptor using an electrostatic recording tester (SP-428 manufactured by Kawaguchi Electric). The initial potential V ₀ in the table indicates the charging potential when a negative 5KV corona is instantaneously discharged, and the dark decay V _K indicates the potential decay when the battery is left in the dark for 10 seconds (V _K = V ₁₀ /V ₀ ×100, V ₁₀ : electric potential after 10 seconds in a dark place), half-reduction exposure amount E ₅₀ indicates the light amount value until the electric potential is halved when 10× white light is irradiated. For convenience, the residual potential V _R is expressed as a ratio of the surface potential V ₁₁ after irradiation with 10× white light for 1.0 seconds to the potential V ₁₀ before exposure (V _R =V ₁₁ /V ₁₀ ×100). Further, the electrophotographic photoreceptors prepared in Comparative Examples 1 to 2 and Examples 1 to 5 were applied to an electrophotographic apparatus using the Carlson method to produce images, and initial image quality, particularly background staining, was observed. The results are shown in Table 1.

[Table] From Table 1, compared to Comparative Examples 1 and 2, the electrophotographic photoreceptor of the present invention in which the compound represented by the general formula () is added to the charge transport layer can reduce residual potential and improve image quality. Become good. As described above, the electrophotographic photoreceptor of the present invention has a low residual potential and can provide good images.

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor having a conductive layer, a charge generation layer containing an organic pigment that generates a charge, and a charge transport layer having charge retention and transport functions, the charge transport layer has the general formula () (wherein R represents hydrogen, an alkyl group, a hydroxyl group, or a carboxyl group) or a hydrate thereof. 2. The electrophotographic photoreceptor according to claim 1, wherein the compound represented by the general formula () is orotic acid. 3. The electrophotographic photoreceptor according to claim 1 or 2, wherein the charge transport layer contains 0.001 to 15% by weight of the compound represented by the general formula ().