JPH0251752B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a substrate for an electrophotographic printing original plate. Generally, an electrophotographic lithographic printing original plate is constructed by providing a layer containing an inorganic or organic optical semiconductor on a base material having characteristics such as water resistance and conductivity. Sheet-like materials such as paper, metal foil, film, or composites of these are used as the base material, but when paper is used, the paper must be treated to be waterproof.
Furthermore, in order to improve electrophotographic images, a coating layer containing an inorganic electrolyte such as sodium chloride, potassium chloride, calcium chloride, or an organic polymer electrolyte such as a quaternary ammonium salt, which is usually called a conductive agent, is provided. ing. However, when a lithographic printing original plate is prepared using paper that has been subjected to such treatment as a base material, plate elongation is unavoidable due to the application of dampening water during printing, even after water-resistant treatment. This causes problems such as wrinkles on the plate during printing, misregistration of printed matter, and irregularly sized ruled lines. Instead of paper, paper with a metal foil such as aluminum, zinc, or copper bonded with adhesive (hereinafter referred to as metal foil laminated paper) is used, and the layer of metal foil is placed between the photosensitive layer and the paper. If so, it is possible to obtain a printing original plate that satisfies water resistance and has good dimensional stability. (For example, Tokuko Sho 38-
17249, 41-2426, 41-12432, etc.). As an adhesive for metal foil laminated paper, for example aluminum foil laminated paper which is widely used industrially, vinyl acetate resin, acrylic resin, polyolefin resin, urethane resin, etc. are usually used. These are applied as a water-based paint in the form of an emulsion or as a solvent-based paint using an appropriate solvent, and then applied between the layers of metal foil and paper to perform lamination. Water-soluble resins such as casein, poval, and starch are also used as adhesives. In addition, wax resin, polyolefin resin (polyethylene,
Hot-melt methods and extrusion coating methods using resins that melt when heated, such as polypropylene, ethylene-vinyl acetate copolymer resins, ionomers, etc., are also commonly used. The present inventors manufactured an electrophotographic printing original plate using metal foil laminated paper as a base material and investigated its practicality.The following two main physical properties were found to be required for the adhesive between the metal foil and the paper. It is a point. (1) During plate making, when heat fixing the developer, blisters (damage between layers, also known as blisters) should not occur due to softening of the adhesive or insufficient adhesive strength. (2) It must not be destroyed by water that enters from the edge of the original printing plate during printing. That is, the adhesive layer is dissolved or swelled by the dampening water and the adhesive strength is reduced, so that the paper and the metal foil do not separate during printing and the printing original plate is destroyed. For example, metal foil laminated paper produced by the hot melt method or extrusion coating method is completely unsuitable in respect of the above point (1). However, the above problem (1) can be almost solved by taking measures such as reducing the coating thickness in the back layer or applying a mixture of breathable substances. However, at present, it has not been possible to find a sufficient solution that satisfies both (1) and (2) above. According to the experimental results of the present inventors, a relatively practical product was obtained when an acrylic resin emulsion was used as an adhesive between a sheet of metal foil. However, this is still insufficient, and when the number of prints increases, it is particularly unsatisfactory in point (2). An original plate based on metal foil laminated paper using a synthetic rubber adhesive tends to generate blisters during plate making, but it had sufficient resistance to soaking water that entered from the edge during printing. Therefore, as a result of further research, we succeeded in obtaining a practically excellent base material for electrophotographic lithographic printing plates by using a certain ratio of synthetic rubber resin in combination with acrylic resin emulsion, which led to the present invention. It is. An object of the present invention is to provide a base material for an electrophotographic printing plate that has improved water resistance, blister resistance, and printing durability against dampening water that enters from the end surface of the printing plate during printing. The present invention provides a base material for an electrophotographic lithographic printing original plate, which has a metal foil laminated paper as a base material, and an image receiving layer containing a photoconductive substance is provided on the metal foil directly or through an intermediate layer. A base material for an original plate for electrophotographic lithographic printing, characterized in that the adhesive between the foil and the paper is a mixture of an acrylic resin emulsion and a synthetic rubber resin in a dry weight ratio of 50:50 to 97:3. It is. In the present invention, the metal foil has two roles: a conductive layer necessary for creating an image using electrophotography, and a water-resistant layer to prevent soaking water from reaching the paper layer during printing. Any material may be used as long as the metal is made into a thin film to meet this purpose. For example, it is a single composition of iron, copper, tin, aluminum, lead, zinc, etc., or an alloy thereof. Among these materials, aluminum is preferred as a material to be laminated with paper for the following reasons: (1) It has a small specific gravity and is light, (2) It has good malleability and can be easily processed into a foil shape. Of course, the present invention is not limited to this. The intermediate layer refers to a layer provided between the metal foil of the base material (metal foil laminated paper) and the photosensitive layer (image receiving layer). Usually, synthetic resin emulsion is used to add pigments such as clay and calcium carbonate, conductive agents, etc. as necessary.
It is mixed with a waterproofing agent and applied. The image-receiving layer (photosensitive layer) refers to a layer that is imaged by electrophotography and contains a photosemiconductor as a basic component. Usually zinc oxide,
An inorganic optical semiconductor powder such as titanium dioxide or cadmium sulfide dispersed in an insulating binder resin, or an organic optical semiconductor such as polyvinyl carbazole is used. In the present invention, the acrylic resin emulsion is an emulsion obtained by finely pulverizing a homopolymerization or copolymerization of acrylic acid ester or methacrylic acid ester, or a copolymerization resin with vinyl acetate, acrylic acid, styrene, or the like. In the present invention, the synthetic rubber resin is a rubber synthesized using petroleum or other raw materials, and depending on the raw material, styrene butadiene rubber (commonly known as SBR),
Acrylonitrile butadiene rubber (commonly known as NBR),
Methyl methacrylate butadiene rubber (commonly known as
MBR), butadiene rubber, isoprene rubber, butyl rubber, chloroprene rubber, silicone rubber, urethane rubber, fluorine rubber, etc. The blending ratio of acrylic resin emulsion and synthetic rubber resin must be carefully determined as it directly affects the performance of the intended printing plate. It is desirable that the ratio is in the range of 50:50 to 97:3. If the amount of synthetic rubber resin exceeds this ratio, the adhesive layer will soften due to heating during plate making.
It becomes difficult to withstand the generation of water vapor from the paper layer and the rapid expansion of air, making it more likely to cause blister. On the other hand, if the synthetic rubber resin is less than this ratio, the effect of using the synthetic rubber resin in combination will be almost negligible, and edge peeling will likely occur during printing. If the amount of adhesive applied is extremely small, it will not be possible to achieve sufficient surface adhesion between the paper and the metal foil.
In particular, because one side of the laminated paper is paper and has a surface with many microscopic irregularities, and it is inevitable that some of the adhesive will penetrate into the paper layer, at least 0.5 g/m ² or more Application amount is required. If the amount applied is less than this, the paper surface will not be covered sufficiently with the laminating adhesive, and as a result, the adhesive strength between the metal foil and the paper will partially decrease. Blisters form between the paper and the metal foil because the paper cannot withstand the rapid expansion of air and the generation of water vapor from within the paper layer when exposed to intense heat during the plate-making process. The upper limit of the coating amount is naturally limited by the performance of the laminator or economic efficiency. Practically 1.0
A range of g/m ² to 7.0 g/m ² is preferred, and is determined in consideration of the printing durability required when used as a printing plate. The present invention will be specifically explained below using examples. Example 1 Commercially available high-quality paper with a weight of 100 g/m ² and a thickness of 10 μ
laminated with aluminum foil. The compounding ratio of the laminating adhesive is as follows, and the amount applied is 2.0
g/ ^m2 . In the following, all "parts" represent weight ratios in terms of solid content. (Composition) Acrylic ester copolymer emulsion (Hoechst Synthesis, Movinyl 987) 80 parts Synthetic rubber resin (Mitsui Toatsu, Polylac 750,
SBR type) 20 copies A printing plate was prepared using this aluminate paper as a base material by the following method. First, a back coating layer with the following composition was provided on the side opposite to the aluminum. The coating amount was 2.0 g/m ² . Polyvinyl alcohol (Nippon Gosei, T-330)
30 parts vinyl acetate emulsion (Hoechst Synthesis, Movinyl M-630) 50 parts quaternary ammonium type conductive agent (Dow Chemical,
ECR-77) 20 parts Next, an intermediate layer with the following composition was provided on the aluminum surface. The coating amount was 8 g/m ² . Clay 50 parts Acrylic acid ester copolymer emulsion (Hoechst Synthesis, Movinyl DM772) 50 parts A photoconductive layer having the following composition was further provided on the intermediate layer. The coating amount was 22 g/m ² . Zinc oxide (Sakai Chemical Co., Ltd., Sazetx #2000) 80 parts Acrylic resin (Nippon Reichhold Co., Ltd., 7-1021)
20 parts Rose Bengal 0.1 part The obtained sheet was heated in an atmosphere of 25℃ and 50% RH for 24 hours.
Time dark adaptation was performed to obtain an original plate for electrophotographic lithography. Example 2 A printing original plate was obtained in exactly the same manner as in Example 1, except that the following composition was used as a laminating adhesive. (Composition) Acrylic ester copolymer emulsion (Hoechst Synthesis, Movinyl 987) 80 parts Synthetic rubber resin (Nippon Zeon, Hiker 1551,
NBR type) 20 copies

[Table] Comparative Examples 1 to 3 Printing original plates were prepared in exactly the same manner as in Example 1, except that the formulation of the laminating adhesive, the amount of coating, etc. were changed as variables. The evaluation results are summarized in the table. (Evaluation method of original plate) The original plates obtained in the above Examples and Comparative Examples were plate-made using a predetermined original drawing using an ITEC 175 plate-making machine. Next, the plate was thoroughly wetted with absorbent cotton impregnated with etching solution (manufactured by ITETSUKU Co., Ltd.) and printed on a Toko 800 printer. The dampening solution used during printing was a mixture of the above etchant and water in a ratio of 1:5. Guns (Black #5500) was used as the printing ink. Blisters during plate making completely depend on the preheating condition of the plate making machine heater section or the heater temperature adjustment scale, so the heater section must be cooled to the same temperature as room temperature, and the heater temperature adjustment scale must be set at the upper and lower limits. The plate was made in an intermediate condition and judged. As is clear from the above description, according to the present invention, there is no occurrence of prister during plate making, and the water resistance to dampening water is also improved, so that the printing durability is greatly improved.

Claims (1)

[Scope of Claims] 1. An electrophotographic lithographic plate comprising a paper base material to which a metal foil is bonded with an adhesive, and an image-receiving layer containing a photoconductive substance is provided on the metal foil directly or via an intermediate layer. An electrophotographic printing original plate, characterized in that, in the base material of the printing original plate, the adhesive is a mixture of an acrylic resin emulsion and a synthetic rubber resin in a dry weight ratio of 50:50 to 97:3. Base material for use. 2. The base material for an electrophotographic printing original plate according to claim 1, wherein the adhesive is coated in an amount of 0.5 g/m ² or more.