JPH0217107B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor. More specifically, the present invention relates to a photoreceptor used in a laser printer device. In particular, the present invention relates to an electrophotographic photoreceptor having high photoresponsiveness in the oscillation wavelength region of a semiconductor laser. Conventionally, the oscillation wavelength of semiconductor lasers, i.e. 750nm.
As the electrophotographic photoreceptor having photoresponsiveness in the near-infrared region, those using selenium-tellurium-arsenic, cadmium sulfide, or phthalocyanine as a photoconductive material are known. Among these, selenium-tellurium-arsenic and cadmium sulfide have problems in terms of safety for living organisms. On the other hand, phthalocyanines are usually available in the form of pigments and have long been known to have photoconductivity. A photoreceptor using a phthalocyanine pigment is usually produced by providing on a conductive support a photoconductive layer in which the phthalocyanine pigment is dispersed in an organic resin having a film-forming ability. The photoreceptor produced in this manner has a wide range of spectral sensitivity from the visible region to the near-infrared region, but the photoresponsiveness itself is not necessarily sufficient. In particular, there is a so-called induction phenomenon that shows a delay in photodischarge immediately after light irradiation, and the existence of this phenomenon has a negative effect on the photoresponsiveness and potential stability during repetition. Furthermore, phthalocyanine photoreceptors are not always satisfactory in terms of image quality;
Problems have often occurred with the reversal system in semiconductor laser printers. A photoreceptor using zinc oxide as a photoconductive material has no hygienic problems and provides extremely good images. Zinc oxide is usually dyed with a dye sensitizer to make it photoresponsive in the visible light region. However,
Dye sensitizers that are effective for such photoresponsive spectral sensitization are usually effective only for visible light;
To date, no dye sensitizer is known that is effective in the near-infrared light region of 750 nm or more. A technology has also been proposed that combines copper phthalocyanine and zinc oxide to extend photoresponsiveness to the near-infrared region [for example, Tachibana, Kishi, Takahashi, Sakata: Proceedings of the 48th Research Conference of the Society of Electrophotography, p. 48 ( (December 4, 1981)] was insufficient in terms of photoresponsiveness and cyclic stability. In view of the above circumstances, the present inventor proposes an electrophotographic photoreceptor that has high photoresponsiveness to the oscillation wavelength of a semiconductor laser, has excellent repeat stability and durability, and has excellent uniformity of image quality. With this in mind, we have made extensive studies and arrived at the present invention. That is, the above-mentioned object of the present invention is characterized in that a photoconductive layer containing zinc oxide, a phthalocyanine pigment, a compound represented by the following general formula (I), and an insulating organic resin is provided on a conductive support. Electrophotographic photoreceptor. General formula (I) (However, R ₁ , R ₂ , R ₃ , and R ₄ in the formula are hydrogen atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, or aralkyl groups, and R ₅ and R ₆ are hydrogen atoms. atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, alkenyl groups, cycloalkenyl groups, or aryl groups,
R ₇ , R ₈ , R ₉ , R ₁₀ are hydrogen atoms, hydroxyl groups,
Substituted or unsubstituted alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, alkoxy groups,
or represents an amino group, and further R ₅ and R ₆
may be cyclized with each other to form a saturated or unsaturated hydrocarbon ring having 3 to 10 carbon atoms. ) was achieved. The present invention will be explained in detail below. The applicant uses zinc oxide powder as a photoconductive material,
A composition in which a low-molecular organic compound is uniformly dispersed in molecular form in a matrix of organic resin having film-forming ability is used as a binder for zinc oxide,
As a result of a detailed study of a photoreceptor using a phthalocyanine pigment as a spectral sensitizer for zinc oxide, the photoresponsiveness of the photoreceptor can be improved by using a composition containing the compound represented by the general formula (I) as a binder. It was also found that the cyclic stability and cyclic durability were significantly improved. The zinc oxide used in the present invention may be any of the known zinc oxides conventionally used in electrophotographic photoreceptors. In addition, the present invention also includes zinc oxide which has been conventionally considered undesirable as a photoreceptor, such as zinc oxide with a specific surface area of 2 m ² /g or less, zinc oxide with a specific surface area of 8 m ² /g or more, or acicular zinc oxide. Applicable. The phthalocyanine pigment used in the present invention is represented by the following general formula (). General formula () (C ₈ H ₄ N ₂ ) ₄ Rn However, R is a hydrogen atom or a metal atom, and n
is 0-2. Among them, alpha (α), beta (β), gamma (γ), pi (π), x (x), epsilon (ε) type metal-free phthalocyanines, copper, nickel, cobalt, lead, zinc, aluminum, Metal phthalocyanines such as vanadyloxy and aluminum chlorinated phthalocyanines are preferred, especially alpha (α), x (x),
Preference is given to metal-free phthalocyanines of the epsilon (ε) type or copper, cobalt, aluminum, vanadyloxy and aluminum chlorinated phthalocyanines. Further, in the present invention, in addition to the sensitization of zinc oxide using the phthalocyanine pigment, it is also possible to use a dye sensitization technique using an organic dye.
Dye sensitizers suitable for the present invention include fluorescein, dichlorofluorescein, dibromofluorescein, diiodofluorescein, tetrachlorofluorescein, tetrabromofluorescein,
Xanthene pigments such as tetraiodofluorescein, tetrachlortetrabromofluorescein, tetrachlortetraiodofluorescein, tetrabromtetraiodofluorescein, bromophenol blue, tetrabromophenol blue, tetraiodophenol blue, bromothymol blue, bromcresol purple, brome Conventional zinc oxide photoreceptors include phenolsulfophthalein dyes such as cresol green, thiazine dyes such as methylene blue, triphenylmethane dyes such as crystal violet and malachite green, and acridine dyes such as acridine yellow and acridine orange. What is used can be applied as is. Although the amount of these dye sensitizers added varies depending on the specific surface area of zinc oxide, it is generally appropriate to use them in an amount in the range of 0.1 to 10 parts by weight per 100 parts by weight of zinc oxide. Conventionally known techniques can be used to sensitize zinc oxide using a dye sensitizer. For example, a method in which a dye sensitizer solution and zinc oxide are mixed, the dye sensitizer is adsorbed onto the surface of the zinc oxide, and then the solution containing the unadsorbed dye sensitizer is removed. After mixing the dye sensitizer and zinc oxide and adsorbing the dye sensitizer on the surface of the zinc oxide, a binder solution is added without removing the solution containing the unadsorbed dye sensitizer. A method for preparing a charge generation layer solution. A method of simultaneously adding a dye sensitizer solution, zinc oxide and a binder solution and mixing and dispersing them is also effective. Specific examples of compounds represented by general formula (I) suitable for use in the electrophotographic photoreceptor of the present invention are listed below. CA-1 1.1-bis(4-N,N-dimethylamino-2-methylphenyl)-1-phenylmethane CA-2 1.1-bis(4-N,N-dimethylamino-2-methylphenyl)-1-(methoxyphenyl) enyl)methane CA-3 1.1-bis(4-N,N-dimethylamino-2-methoxyphenyl)-1-phenylmethane CA-4 1.1-bis(4-N,N-dimethylamino-2-methylphenyl)- 1-(2.4-dimethoxyphenyl)methane CA-5 1.1-bis(4-N,N-dimethylamino-2-methylphenyl)-1-(2-chlorophenyl)methane CA-6 1.1-bis(4-N, N-diethylaminophenyl)-1-phenylmethane CA-7 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-phenylmethane CA-8 1.1-bis(4-N,N-diethylamino-2- methoxyphenyl)-1-phenylmethane CA-9 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-(4-methoxyphenyl)methane CA-10 1.1-bis(4-N,N -diethylamino-2.5-dimethoxyphenyl)-1-phenylmethane CA-11 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-(2.5dimethoxyphenyl)methane CA-12 1.1-bis(4 -N,N-diethylamino-2-methylphenyl)-1-(3.4methylenedioxyphenyl)methane CA-13 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-(4-N, N-
dimethylaminophenyl)methane CA-14 1.1-bis(4-N,N-diethylamino-2-methylphenyl)-1-(4-N,N-
diethylaminophenyl)methane CA-15 1.1.1-tris(4-N,N-dimethylaminophenyl)methane CA-16 1.1.1-tris(4-N,N-dimethylamino-2-methylphenyl)methane CA -17 1.1.1-Tris(4-N,N-diethylaminophenyl)methane CA-18 1.1.1-Tris(4-N,N-diethylamino-2-methylphenyl)methane CA-19 1.1-bis(4- N,N-diethylamino-2-methylphenyl)-1-(4-N,N-
dimethylamino-2-methylphenyl)methane CA-20 1.1-bis(4-N,N-dibenzylaminophenyl)-1-phenylmethane CA-21 1.1-bis(4-N,N-dibenzylamino-2- methylphenyl)-1-phenylmethane CA-22 1.1-bis[4-N,N-di(p-tolyl)aminophenyl]-1-phenylmethane CA-23 1.1-bis[4-N,N-di(p-tolyl) Amino-2-methylphenyl]-1-phenylmethane CA-24 1.1-bis[4-N,N-dibenzylamino-2-methylphenyl)-3-phenylpropane CA-25 1.1-bis(4-N,N- dibenzylamino-2-methylphenyl)pentane CA-26 1.1-bis(4-N,N-dibenzylamino-2-methylphenyl)cyclohexane CA-27 1.1-bis(4-N,N-dibenzylamino-2.5- dimethylphenyl)heptane CA-28 1.1-bis(4-N,N dibenzylamino-2-methylphenyl)-1-(4-N,N-
diethylaminophenyl)methane CA-29 1.1-bis(4-N,N-dibenzylamino-2-methylphenyl)-1-(4-N,N
-diethylamino-2-methylphenyl)methane CA-30 1.1.1-tris(4-N,N-dibenzylamino-2-methylphenyl)methane CA-31 1.1-bis(4-N,N-dibenzylamino-2 -methoxyphenyl)-1-phenylmethane CA-32 1.1-bis(4-N,N-dibenzylamino-2.5-dimethoxyphenyl)-1-phenylmethane CA-33 1.1-bis(4-N,N-dibenzylamino-2.5-dimethoxyphenyl)-1-phenylmethane Benzylamino-2-methylphenyl)-1-(2.4-methylenedioxyphenyl)methane CA-34 1.1-bis(4-N,N-dibenzylamino-2-methoxyphenyl)-1-(2.4methylenedioxyphenyl) oxyphenyl)methane CA-35 2.2-bis(4-N,N-diethylamino-2-methylphenyl)propane CA-36 2.2-bis(4-N,N-diethylamino-2-methoxyphenyl)propane CA-37 2.2-bis(4-N,N-dibenzylamino-2-methylphenyl)propane CA-38 2.2-bis(4-N,N-dibenzylamino-2-methoxyphenyl)propane As a matrix polymer in the present invention is preferably an organic resin that has excellent compatibility with the compound represented by the above general formula (I), high electrical insulation, and excellent physical, chemical, and electrical stability. For example, polycarbonate, polyarylate, polysulfone, polyethersulfone, phenoxy resin, poly(2.6-dimethyl-1.4-phenylene ether), polystyrene, polymethyl methacrylate, polyester resin, polyurethane, polyvinyl chloride, polyvinyl acetate, vinyl chloride. - vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, styrene-acrylonitrile copolymer, vinylidene chloride-acrylonitrile copolymer, and the like. These polymers may be used alone or in combination of two or more. The blending ratio of zinc oxide and phthalocyanine pigment varies depending on the specific surface area of zinc oxide and the use of the photoreceptor, but generally a range of 1 to 1000 parts by weight of phthalocyanine pigment is suitable for 100 parts by weight of zinc oxide. When the photoreceptor of the present invention is used in a negative charging mode, the proportion of zinc oxide added is increased. On the other hand, when using in positive charging mode, the blending ratio of phthalocyanine pigment is increased. The amount of the compound represented by the general formula (I) in the matrix polymer is preferably 10 to 200 parts by weight per 100 parts by weight of the polymer. The blending ratio of the binder composition to zinc oxide is preferably 50 to 400 parts by weight per 100 parts by weight of zinc oxide. The electrophotographic photoreceptor of the present invention is produced by milling a mixture of zinc oxide, a phthalocyanine pigment, a compound represented by the general formula (I), an organic resin, and a dispersion solvent using a ball mill, an attritor, a sand mill, a kedimir, or the like.
Uniformly mixed and dispersed using a three-roll dispersion machine, the resulting photoconductive layer coating solution can be applied to blade coating, reverse coating, rod coating, gravure coating, knife coating, spray coating, and dipping. It is produced by coating on a support using a coating method such as coating and drying. The thickness of the photoconductive layer is preferably in the range of 5 to 100 μm, more preferably 10 to 50 μm. Dispersion solvents used for preparing the photoconductive layer coating solution include aromatic hydrocarbons such as benzene, toluene, and xylene, methylene chloride, chloroform, 1.1-dichloroethane, 1.2-dichloroethane, 1.1.2-trichloroethane, and chlorobenzene. Examples include halogenated hydrocarbons, tetrahydrofuran, cyclic ethers such as 1,4-dioxane, ketones such as acetone and 2-butanone, and mixed solvents thereof. In preparing the photoconductive layer coating solution, it is desirable to dissolve the compound represented by the general formula (I) and the organic resin in a dispersion solvent in advance. The conductive support suitable for the present invention is a metal plate such as aluminum, nickel, or chromium, or a metal such as aluminum, nickel, or palladium, or a metal oxide such as tin oxide or indium oxide, on paper, plastic film, glass, or the like. Materials that have been vapor-deposited, ion-plated, or sputter-deposited, aluminum or other metal foils bonded with paper or plastic film, or internally added, impregnated, or coated with organic or inorganic conductive treatment agents or conductive pigments. Examples include printed paper or plastic film.
Regarding its shape, it may be sheet-like, cylindrical, or other shapes. In the present invention, an intermediate layer can be provided between the conductive support and the photoconductive layer. This intermediate layer prevents the injection of free carriers from the conductive support into the photoconductive layer and acts as an adhesive to integrally adhere the photoconductive layer to the conductive support. Furthermore, it also has a buffering effect to prevent dielectric breakdown of the photoconductive layer due to corona discharge overcurrent during corona charging. As the material for this intermediate layer, water-based polymeric substances such as casein, gelatin, starch, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, hydroxypropyl cellulose, water-soluble polyvinyl butyral, polyacrylic acid, polyethyleneimine, and polyethylene glycol are used. Can be done. The thickness of the intermediate layer is suitably in the range of 0.5 to 10 μm. The electrophotographic photoreceptor of the present invention has the above structure, and as is clear from the examples described later, it has high sensitivity in the oscillation wavelength range of semiconductor lasers of 750 nm or more, and has an excellent low residual potential. It is something. In addition, there is less fatigue deterioration due to repeated use,
It has stable properties and has excellent repeated durability. Furthermore, since zinc oxide is used as the photoconductive material, the image quality is good and the image reproducibility in a reversal development system is extremely excellent. EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the embodiments of the present invention are not limited thereby. Example 1 Water-soluble polyvinyl butyral (Eslec W201,
Coating with a 10% aqueous solution of Sekisui Chemical Co., Ltd.)
A 1 μm thick intermediate layer was provided by drying at °C for 10 minutes. Next, polycarbonate (Panlite L-
1250, manufactured by Teijin Kasei Ltd.) 10 parts by weight to 90 parts by weight of 1.2
-Dissolved in dichloroethane and then CA-7
Add 10 parts by weight of the exemplified compound shown in and completely dissolve it. Next, ε-type copper phthalocyanine (Lionol Blue ES, manufactured by Toyo Ink Mfg. Co., Ltd.) 1 was added to this solution.
Parts by weight are added and the mixture is dispersed in a porcelain ball mill for 24 hours. Next, 10 parts by weight of zinc oxide (fine zinc thin, manufactured by Sakai Chemical Industry Co., Ltd.) is added to this dispersion, and the mixture is further mixed and dispersed for 10 hours. Coating the obtained photoconductive layer coating liquid on the above-mentioned intermediate layer,
A photoconductive layer having a thickness of 15 μm was provided by drying at 110° C. for 5 minutes, thereby producing an electrophotographic photoreceptor of this example. The electrophotographic properties of this electrophotographic photoreceptor were measured using an electrostatic copying paper tester model SP-428 (manufactured by Kawaguchi Denki Seisakusho Co., Ltd.). That is, the surface of the photoconductive layer of the photoreceptor was exposed to a corona discharge voltage of -6 KV and a scanning speed of 250.
Charging is performed under the conditions of mm/sec, and the potential immediately after charging is V ₀
Measure [V]. After dark decay for 5 seconds (potential V ₅ [V]), tungsten light (color temperature 2854
[〓], illuminance 2 [lux]) to increase the surface potential to V ₅ /
The exposure amount required to attenuate to 2 [V] (half-reduced exposure amount) E _1/2 [lux·sec] and the potential after 60 [lux·sec] irradiation were recorded as residual potential V _R [V]. In addition, a xenon lamp and a monochromator (P-
Near-infrared monochromatic light (λ = 790 nm, light intensity 25 μm/cm ² ) obtained by combining 250 and Nikon Optical Co., Ltd.)
The photosensitivity E _1/2 [μJ/
cm ² ] was similarly evaluated. The results are shown in Table 1.

[Table] As is clear from the above results, the electrophotographic photoreceptor of this example has sufficient charge-accepting ability and also has extremely high photoresponsiveness to visible light and the oscillation wavelength of a semiconductor laser. Example 2 In place of exemplified compound CA-7 in Example 1,
The electrophotographic photoreceptor of this example was produced in the same manner as in Example 1 except that the compounds listed in Table 2 were used. The photoreceptor characteristics of these photoreceptors were measured in the same manner as in Example 1, and the results shown in Table 2 were obtained.

[Table] As is clear from the above results, all of the electrophotographic photoreceptors of this example exhibited excellent photoresponsiveness. Example 3 In Example 1, polycarbonate, CA-
When adding 10 parts by weight of zinc oxide to a dispersion containing 7 and ε-type copper phthalocyanine, a dye sensitizer solution in which 0.1 part by weight of tetrachlortetraiodofluorescein was dissolved in 1 part by weight of tetrahydrofuran was added at the same time. An electrophotographic photoreceptor of this example was prepared according to the procedure of Example 1, and the characteristics of the photoreceptor were evaluated. The results are shown in Table 3.

[Table] As is clear from the above results, the electrophotographic photoreceptor of this example had further improved photoresponsivity to visible light and λ=790 nm light. Example 4 The electrophotographic photoreceptor of this example was produced in accordance with the procedure of Example 3, except that α-type copper phthalocyanine, vanadyloxyphthalocyanine, or aluminum chlorinated phthalocyanine was used in place of the ε-type copper phthalocyanine in Example 3. The photoreceptor characteristics were evaluated. The results are shown in Table 4.

[Table] As is clear from the above results, all the electrophotographic photoreceptors of this example exhibited excellent photoresponsiveness. Example 5 The electrophotographic photoreceptor of this example was produced in accordance with the procedure of Example 3, except that the amount of ε-type copper phthalocyanine was changed to 3 parts by weight, and the amount of zinc oxide was changed to 1 part by weight. Created. The photoreceptor characteristics of the photoreceptor sample of this example were evaluated in positive charging mode. The results are shown in Table 5.

[Table] As is clear from the above results, the electrophotographic photoreceptor of this example exhibits extremely excellent photoresponsiveness even in the positive charging mode. Example 6 The electrophotographic photoreceptor of Example 5 was installed in a commercially available electrophotographic copying machine operating in a positive charging mode, and images obtained by reversal development were evaluated. As a result, no image defects such as black spots were observed, and high quality image characteristics were exhibited. Comparative Example An electrophotographic photoreceptor of this comparative example was produced according to the procedure of Example 5, except that exemplified compound CA-7 was not used. The photoreceptor characteristics of the thus prepared photoreceptor sample were evaluated in positive charging mode. The results are shown in Table 6.

[Table] As is clear from the above results, the electrophotographic photoreceptor of this comparative example has a low charging potential and slow photoresponsiveness. Next, the sample of this comparative example was installed in a commercially available electrophotographic copying machine operating in a positive charging mode, and images obtained by reversal development were evaluated. As a result, an image with low image density and black dots in the background was observed, causing problems in image reproducibility.

Claims (1)

[Claims] 1. Electrophotography, characterized in that a photoconductive layer containing zinc oxide, a phthalocyanine pigment, a compound represented by the following general formula (I), and an insulating organic resin is provided on a conductive support. Photoreceptor. General formula (I) (However, R ₁ , R ₂ , R ₃ , and R ₄ in the formula are hydrogen atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, or aralkyl groups, and R ₅ and R ₆ are hydrogen atoms. atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, alkenyl groups, cycloalkenyl groups, or aryl groups,
R ₇ , R ₈ , R ₉ , R ₁₀ are hydrogen atoms, hydroxyl groups,
Substituted or unsubstituted alkyl groups, cycloalkyl groups, alkenyl groups, aryl groups, alkoxy groups,
or represents an amino group, and further R ₅ and R ₆
may be cyclized with each other to form a saturated or unsaturated hydrocarbon ring having 3 to 10 carbon atoms. )