JPH0157910B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic plate making material capable of making planographic printing plates by electrophotography, and particularly relates to an electrophotographic plate material having improved pressure resistance and image quality. A method of producing a lithographic printing plate by electrophotography is well known, and generally involves uniformly charging a photoconductive layer of an electrophotographic plate material, imagewise exposing it, and then performing wet or dry development to obtain a toner image. After fixing this toner image, a desensitizing liquid (etching liquid) is applied.
The non-image areas with no toner image are made hydrophilic by processing to form a lithographic printing plate. As such an electrophotographic printing material, one using a paper support is conventionally known, but with this material, toner sometimes adheres to areas subjected to pressure, resulting in printing stains. In other words, friction is reduced during the manufacturing process of the electrophotographic material, by friction with the pass rolls in the plate-making machine, or by friction with the back side of the material during the handling work before loading the sheet-shaped electrophotographic material into the plate-making machine. As a result of pressure deformation of the receiving area or change of electrophotographic characteristics, toner may also adhere to non-image areas, resulting in printing stains. Furthermore, if the smoothness of the photoconductive layer is increased in order to improve image quality, the above-mentioned pressure resistance may deteriorate, and there is a limit to the improvement of image quality. Therefore, an object of the present invention is, firstly, to provide an electrophotographic printing material that can obtain a lithographic printing plate with excellent pressure resistance, easy handling, and less staining, and secondly, to provide an electrophotographic printing plate that has excellent pressure resistance and is easy to handle. The purpose of the present invention is to provide excellent electrophotographic printing materials. As a result of various studies, the present inventors provided a pressure relief layer with a Young's modulus of 2×10 ¹⁰ dynes/cm ² or less at 25°C on at least one surface of the supporting substrate, and the volume resistivity of the supporting substrate was It has been found that the above objects can be achieved by using an electrophotographic printing material comprising a photoconductive layer provided on a support having a resistance of 10 ¹⁰ Ω or less. The volume resistance here refers to the current value A (ampere) when a sample is sandwiched between two circular electrodes with a radius of 2.5 cm and a DC voltage V (volt) is applied between the electrodes.
It is the resistance value obtained by reading R _v = V/A (Ω). The main components of the above pressure relief layer include polyethylene, polypropylene, natural rubber, SBR rubber,
ABS rubber, fluorinated resin, etc. are suitable, but there are no particular limitations as long as the Young's modulus of the obtained layer is 2×10 ¹⁰ dynes/cm ² or less at 25°C. For example, ethylene- Vinyl acetate copolymer, ethylene-acrylic ester copolymer, ethylene-methacrylic ester copolymer, polyacrylic acid, polyacrylic ester, polymethacrylic acid, polymethacrylic ester, ethylene-acrylic acid copolymer, Ethylene-acrylonitrile-
A methacrylic acid copolymer, an ethylene-acrylonitrile-methacrylic acid ester copolymer, etc. may also be used, or a mixture of these may be used. Such a pressure relief layer contains an electronically conductive substance so that the volume resistivity of the support finally obtained is 10 ¹⁰ Ω or less. Particularly preferred electronically conductive materials include French patent No.
2277136 and U.S. Pat. No. 3,597,272, in particular oxides of metals selected from zinc, magnesium, tin, barium, indium, molybdenum, aluminum, titanium, silicon, preferably Fine particles of a crystalline oxide or its composite oxide, or carbon black are used. Among these, conductive carbon black is advantageous because it is inexpensive and easy to mix. Such an electronically conductive substance is contained so that the support has a volume resistivity of 10 ¹⁰ Ω or less, more preferably 10 ⁸ Ω or less. The specific amount used to achieve such a resistance value cannot be determined unconditionally because it varies depending on the type of supporting substrate, polymer, and electronically conductive material, but as a general guideline, it is The content ranges from 5 to 30% by weight. A layer as described above covers at least one side of the supporting substrate;
More preferably, both sides may be coated by a laminating method or by coating with an aqueous polymer latex or the like. The thickness of the pressure relief layer thus obtained was 5
A range of ~50μ is appropriate. When it becomes thinner than 5μ,
The pressure resistance becomes insufficient, and on the other hand, if the thickness is made thicker than 50 μm, no further improvement in performance can be expected, and the cost will only increase. Therefore, the preferred thickness is 10-30μ. When applying polyolefin by the melt lamination method, in order to improve the adhesive strength between the base paper and the polyolefin laminate layer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, or ethylene-methacrylic acid ester is applied on the base paper in advance. Polyethylene derivatives such as copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-acrylonitrile-acrylic acid copolymers, ethylene-acrylonitrile-methacrylic acid copolymers, etc. It is preferable that the surface of the substrate be subjected to corona discharge treatment. Alternatively,
JP-A-49-24126, JP-A No. 52-36176, JP-A No. 52-
The base paper can also be subjected to the surface treatments described in Japanese Patent Publications No. 121683, No. 53-2612, No. 54-111331, and Japanese Patent Publication No. 51-25337. On the other hand, the supporting substrate used in the present invention is
Any conductive base paper conventionally used in electrophotographic photosensitive materials can be used, such as ion conductive substances and inorganic metal compounds such as those described in the specifications of U.S. Pat. No. 3,597,272 and French Patent No. 2,277,136. , paper impregnated with electronically conductive substances such as carbon, or mixed during paper making, and those described in Japanese Patent Publications No. 52-4239, No. 53-19031, and No. 53-19654. Synthetic paper can be used. The photoconductive layer provided on the support as described above is composed of a photoconductive substance and a binder. Examples of the photoconductive substance include inorganic photoconductive substances such as zinc oxide, cadmium sulfide, and titanium oxide, and organic photoconductive substances such as phthalonanine dyes. A photoconductive material is used. As the binder, silicone resin, polystyrene, polyacrylic or methacrylic acid ester, polyvinyl acetate, polyvinyl chloride, polyvinyl butyral, and derivatives thereof are used. The ratio of photoconductive material to binder is suitably used in a weight ratio of 3:1 to 20:1. Further, a sensitizer, a coating aid used during coating, etc. can be added as necessary. Such a photoconductive layer is provided on the above-mentioned support, and the surface is prepared in advance by coating, for example, in US Pat. No. 3,411,908.
As described in the specification, surface treatment such as corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet treatment, ozone treatment, plasma treatment, etc. improves the adhesive strength with the photoconductive layer. Therefore, it is preferable. The thickness of the photoconductive layer thus provided is suitably in the range of 5 to 30 microns. In a particularly preferred embodiment of the invention, an intermediate layer may be further provided between the support and the photoconductive layer. The resin used for the intermediate layer is not particularly limited, and examples thereof include polyethylene terephthalate, polyimide, polycarbonate, polyacrylate, polymethyl methacrylate, polyvinyl fluoride, polyvinyl chloride, polyvinyl acetate, polystyrene, styrene-butadiene copolymer, and polystyrene. Methacrylate, silicone resin, chlorinated rubber, epoxy resin, pure and modified alkyd resin, polyethyl methacrylate, poly-
n-Butyl methacrylate, cellulose acetate, ketone resin, polyethylene, polypropylene, polyacrylonitrile, rosin derivative, polyvinylidene chloride, nitrocellulose, phenol-formaldehyde resin, metacresol formaldehyde resin, styrene-maleic anhydride copolymer, polyacrylic acid - polyacrylic acid amide copolymer,
Ethylene glycol fumarate copolymer, methyl vinyl ether-maleic anhydride copolymer, acryloylglycine-vinyl acetate copolymer, polyvinylpyrrolidone, polyvinyl alcohol, polyamide, halogenated styrene, etc. are used. The coating amount of the intermediate layer is used in the range of 0.01 to 10 g/m ² .
Further, if necessary, a conductive inorganic salt may be mixed into the intermediate layer polymer. A lithographic printing plate using the electrophotographic plate material of the present invention may be prepared by a conventionally known method. Specifically, the photoconductive layer is uniformly charged using a corona charging method or the like, and then imagewise exposed to form a charged image, and toner is deposited imagewise using a wet or dry method. It is fixed by means such as heating. Next, the non-image area to which toner is not attached is treated with a desensitizing liquid to make it hydrophilic. As the desensitizing liquid, for example, a ferrocyan compound or a composition containing a ferricyanide compound as described in US Pat. No. 4,116,698, or a metal complex salt as described in US Pat. No. 4,282,811 can be used. Compositions containing such compounds can be used. By performing offset printing in a conventional manner using the lithographic printing plate thus prepared, printed matter with excellent pressure resistance, easy handling, and less staining can be obtained. The electrophotographic printing material of the present invention has, as a support,
It is necessary that its volume resistance is 10 ¹⁰ Ω or less,
If it is more than that, toner tends to adhere to non-image areas as well, causing stains. The first performance characteristic of the electrophotographic plate material of the present invention is that its pressure resistance is dramatically improved, and there is almost no occurrence of scratches or stains due to carelessness in handling or poor transportation in automatic plate making machines. . Second, in order to improve image quality, even if the surface smoothness of the photoconductive layer is increased, pressure resistance deterioration can be prevented, resulting in excellent image quality. For example, with wet development, 133 lines/
It is possible to reproduce inch halftone dot images. Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that "%" and "parts" indicate weight % and parts by weight, respectively, unless otherwise specified. Example 1 A 5% aqueous solution of polyvinylbenzyltrimethylammonium chloride was applied to high-quality paper with a basis weight of 100 g/ ^m2.
After applying 20 g/m ² , it was dried to obtain a conductive base paper. After coating and drying an aqueous latex of ethylene-methyl acrylate-acrylic acid copolymer (weight ratio 65:30:5) to a dry coverage of 0.2 g/m ² on both sides, polyethylene (density 0.92 , average molecular weight 22,000, softening point 112℃) and 15% conductive carbon (melt index: 3) are laminated and supported on both sides with a thickness of 25μ on each side by extrusion method. I got body a. The volume resistance of this support was 10 ⁸ Ω.
Further, the Young's modulus of the peeled and isolated polyolefin layer was approximately 8×10 ⁹ dynes/cm ² . Next, the surface of the polyethylene laminate layer on one side of the support was subjected to a corona discharge treatment under the conditions of 5 kVA sec/m ² , and a coating solution having the following composition was applied thereon using a wire bar to give a dry coverage of 1 g/m ² An intermediate layer was formed by coating and drying the mixture as described above. Colloidal alumina (15% aqueous solution) 50 parts Colloidal silica (20% aqueous solution) 20 parts Polyvinyl acetate emulsion (Sevian A manufactured by Daicel Corporation) 150 parts Surfactant (Kawaken Huain Chemical Co., Ltd.) Amizole DC) 0.1 part Water 100 parts On top of this intermediate layer, in order to improve the smoothness of the photoconductive layer, a coating solution with the following composition was dispersed in a ball mill for about 20 hours, which is longer than usual, until the dry coating amount was 20 g/m ² A photoconductive layer was provided by coating and drying to obtain electrophotographic plate material A of the present invention. Photoconductive layer coating solution formulation Photoconductive zinc oxide (Sazex 2000 manufactured by Sakai Chemical Co., Ltd.) 100 parts Silicone resin (KR-211 manufactured by Shin-Etsu Chemical Co., Ltd.) 35 parts Rose Bengal 0.1 part Fluorescein 0.2 parts Methanol 10 parts Toluene 150 parts Electrophotographic plate material A obtained in this way
After leaving it in a dark place at 25°C and 50% RH for 24 hours, it was made into a plate using a PM355 plate making machine manufactured by Iwasaki Tsushinsha. This was desensitized using an etching solution manufactured by Addressograph Multigraph Co., Ltd., and then printed on the offset printing machine Hamadastar.
When printing was carried out at 700, a good printed matter was obtained that could reproduce a halftone image of 133 lines/inch. Furthermore, an example comparing the effect of pressure resistance with conventional electrophotographic printing materials is shown below. Comparative Example 1 A conventional waterproof layer having the composition shown below was applied to both sides of the above conductive base paper so that it would have a weight of about 25 g/m ² after drying.
A support was obtained. Next, a photoconductive layer of about 20 g/m ² was provided to improve the smoothness as described above to obtain a conventional electrophotographic printing material B. Conventional waterproof layer composition: Clay 7 parts Calcium carbonate 3 parts Starch 1.5 parts Conductive resin (ECR-34 manufactured by Dow Chemical Company)
1.5 parts Water 100 parts Comparative Example 2 On the support of Comparative Example 1 above, a photoconductive coating solution having the same composition as in Example 1 was normally dispersed (approximately 4 hours in a ball mill), and after drying, approximately 20 g /m ² to obtain a conventional electrophotographic plate material C. After making scratches on the surface of three electrophotographic plate materials A, B, and C using a scratch tester manufactured by Shinto Kagakusha,
Plate making, desensitization treatment, and printing were performed using conventional methods, and scratches and stains were compared. In addition, the surface of each photoconductive layer was rubbed with the back surface of each layer, and the friction stains were compared using the same method as described above. Furthermore, the center line average roughness Ra of the photoconductive layer was compared using a stylus meter Surfcom 300B manufactured by Tokyo Seimitsu Co., Ltd. at a measurement speed of 0.3 mm/sec with a 5μ diamond needle. These results are shown in Table 1 together with the Young's modulus of the pressure relief layer and the image quality of the printed matter.

[Table] According to the present invention, an electrophotographic plate material having excellent pressure resistance and excellent image quality was obtained. Example 2 Four coating solutions d, e, f, and g having the composition shown below were applied at 25 g/m ² on both sides of the conductive base paper used in Example 1.
The coating was applied and dried to obtain four supports. Note that all composition ratios are solid content ratios. Coating liquid d composition SBR latex (Nippon Zeon, Nipol4850)
80 parts Conductive carbon 20 parts Naphthalene sulfonic acid (dispersant) 2 parts Coating liquid composition SBR latex (Nippon Zeon, Nipol4850)
55 parts Acrylic ester copolymer 35 parts Emulsion (Nippon Pure Chemical Industries, Ltd., Dulymer SEK103) Conductive carbon 20 parts Naphthalene sulfonic acid (dispersant) 2 parts Coating liquid f composition SBR latex (Nippon Zeon, Nipol4850)
35 parts Acrylic acid ester copolymer 55 parts Emulsion (Nippon Pure Chemical Industries, Ltd., Dulymer SEK103) Conductive carbon 20 parts Naphthalene sulfonic acid (dispersant) 2 parts Coating liquid g composition Acrylic acid ester copolymer 80 parts Emulsion (Nippon Pure Chemical Industries, Ltd.) Drug Dyurimer SEK103) Conductive carbon 20 parts Naphthalene sulfonic acid (dispersant) 2 parts All of these supports exhibited a volume resistivity of approximately 10 ⁸ Ω·. One side of these supports was subjected to corona discharge treatment under the conditions of 5 KVA sec/cm ² , and a photoconductive layer of 20 g/m ² was formed thereon using the same coating solution with a long dispersion time as in Example 1, and electrophotography was performed. Plate-making materials D, E, F, and G were obtained. As in Example 1, the results of performance comparison are shown in Table 2.

[Table] Young's modulus of the pressure relief layer (at 25℃-)
An electrophotographic plate material having a particle size of 2.0×10 ¹⁰ or less and excellent in both pressure resistance and image quality was obtained.

Claims (1)

[Scope of Claims] 1 A photoconductive layer is provided on a support, and the support has a support substrate and at least one surface thereof a photoconductive layer having a Young's modulus of 2×10 ¹⁰ dynes/cm ² or less at 25°C. It has a pressure relief layer, and the volume resistance of the support is 10 ¹⁰ Ω.
An electrophotographic material characterized by the following: 2. The electrophotographic plate material according to claim 1, wherein the photoconductive layer has an average surface roughness of 0.7 μm or less.