JPH0251754B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an original plate for electrophotographic planographic printing. Generally, an original plate for electrophotographic planographic printing 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 materials such as paper, metal foil, and film are used as the base material, but when paper is used, it is usually treated as a conductive agent to make the paper water-resistant and to improve the quality of 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 is provided. 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. If you use paper laminated with metal foil such as aluminum, zinc, or copper instead of paper, and have the metal foil layer between the photosensitive layer and the paper, water resistance can be satisfied and the dimensions A printing original plate with good stability can be obtained (for example, Japanese Patent Publication No. 38-17249, Japanese Patent Publication No. 41-2426, Japanese Patent Publication No. 41-12432). When the metal foil is aluminum (hereinafter referred to as aluminum laminated paper), the adhesive layer between the aluminum foil and paper is usually a vinyl acetate resin, an acrylic resin, a polyolefin resin, a urethane resin, or a phenol resin. Resins, synthetic rubber resins, etc. are used alone, in mixtures, or in copolymerized states. These can be used as water-based paints in the form of emulsions, or as solvent-based paints by selecting a suitable solvent. There are also methods using water-soluble resins such as casein and Bobal as adhesives, or hot melt methods using wax-based resins and polyolefin-based resins.
Extrusion coating methods are well known. As a result of detailed research by the present inventors using such aluminum laminated paper as a base material, it was found that it has the following serious drawbacks. In other words, when an electrophotographic printing original plate in which an intermediate layer and an electrophotographic photosensitive layer are sequentially provided on an aluminum surface is produced and printed, peeling between the aluminum surface and the intermediate layer is extremely likely to occur, and it is not sufficient and practical. However, it was not possible to obtain sufficient printing durability. This is because the surface of aluminum foil is easily oxidized or contaminated when it is exposed to air or comes into contact with the paper surface when rolled up as aluminum laminated paper, resulting in poor adhesion with the intermediate layer provided on top of it. It depends. Since this poor adhesion is caused by the properties of the aluminum surface, no complete solution can be achieved even by various changes in the type or composition of the adhesive contained in the intermediate layer. There are several well-known methods for removing oxidation or contamination from aluminum surfaces, but they have the fatal disadvantage of increasing the number of steps, resulting in unavoidable losses in time and cost. As mentioned above, the effect is not very promising. For example, there is a method of wiping the aluminum surface with a solvent such as alcohol, acetone, toluene, xylene, or esters, but although this method can remove oil-based contaminants, it does not remove the oxide film that has formed on the aluminum surface. It does not reach. In addition, a method of treating the aluminum surface with an alkaline aqueous solution such as caustic soda or caustic potash (for example, caustic potash is used in Example 1 of Japanese Patent Publication No. 41-8396), or a method of treating the aluminum surface with an acidic aqueous solution (for example, Japanese Patent Publication No. 41-14337) Publications) are also known, but these require thorough washing with water after treatment, and even if a clean aluminum surface is obtained by performing these treatments and washing, drying after washing with water is known. A fatal drawback is that the aluminum surface is oxidized again during the process. As a solution other than these methods, it is conceivable to provide a coating layer on the aluminum surface simultaneously with the lamination process to completely cover the surface.
If this treatment is carried out, oxidation and contamination of the aluminum surface will not proceed, so there should be no performance deterioration caused by long-term exposure to air or contact with paper after being rolled up. Providing a coating layer of some kind on the aluminum surface during lamination depending on its use is a well-known technique, for example, usually called anchor coating. The present inventors obtained various types of aluminum laminated paper coated with anchors and studied their suitability as base materials for electrophotographic lithographic printing original plates. However, the coating layer on the aluminum surface (first
Layer 4 in the figure. Hereinafter, this will be referred to as the anchor layer. ) was found to be completely unsuitable as a base material for the electrophotographic lithographic printing original plate aimed at by the present inventors. In other words, when using aluminum laminate paper with an anchor layer on the aluminum surface as a substrate for electrophotographic planographic printing original plates, it is desirable to have all of the following characteristics, but conventionally known anchor materials The current situation is that we cannot obtain what we should be satisfied with. The desired and necessary conditions are as follows. (1) The aluminum surface and anchor layer must be in complete contact. "Adhesion" as used herein refers to a state in which the aluminum surface and the anchor layer do not separate when this base material is processed into a lithographic printing original plate, mounted on a printing machine, and folded by the gripper. Also, during printing, vertical force is repeatedly applied to the original plate due to the tack of ink, but it also means a state in which the aluminum surface and the anchor layer do not separate even after at least 2000 sheets have been printed. (2) The anchor layer itself has water resistance and does not collapse even if it comes into contact with dampening water that permeates through the plate surface during printing. (3) The anchor layer has complete coverage of the aluminum surface, and there are no defects in the film formation, even in the form of minute pinholes. If there is a film formation defect in the anchor layer, even if it is minute, charge will leak from that part when corona charging is performed in the plate making machine, causing white spots on the image surface or, if severe, spots on the photosensitive layer. destruction, etc. will occur. (4) The anchor layer must adhere well to the intermediate layer provided above it. (5) Even with the provision of an anchor layer, the suitability for electrophotography does not deteriorate, and a clean image without fogging can be obtained during plate making. The present inventors have conducted intensive research into the material forming the anchor layer in order to solve the above-mentioned problems, and have found a material that satisfies the above-mentioned necessary characteristics, forms images of excellent quality, and has extremely excellent dimensional stability. He came to the invention of an electrophotographic lithographic printing original plate that can withstand printing of extremely large numbers of sheets. The present invention relates to an original plate for electrophotographic lithographic printing, in which an anchor layer, an intermediate layer, and a photoconductive photosensitive layer are sequentially provided on an aluminum foil of aluminum laminated paper, in which the anchor layer is made of a synthetic resin emulsion, casein, and a water-resistant material. The present invention is characterized in that a coating liquid containing a curing agent as a main component is applied to a dry thickness in the range of 0.05μ to 5.0μ. In the present invention, a synthetic resin emulsion refers to a state in which an artificially synthesized resin is dispersed in fine particles in water. Examples of synthetic resins include vinyl resins, acrylic resins, acrylonitrile resins, olefin resins, styrene resins, polyamide resins, polyethylene terephthalate resins, urethane resins, and the like. In addition, two or more of these may be used as a mixture or as a copolymer. When these synthetic resin emulsions are used in the anchor layer, the adhesion to the aluminum surface and the intermediate layer is significantly improved. However, if the anchor layer is composed of only a synthetic resin, its suitability for electrophotography is impaired and fogging is likely to occur during plate making, so it is necessary to use some kind of water-soluble substance in combination to improve this problem. Water-soluble substances used in combination include starch, polyvinyl alcohol (hereinafter abbreviated as PVA), cellulose derivatives, gelatin, and casein; It is necessary to have water resistance. As a result of various studies conducted by the present inventors, it has been found that a mixture of casein and a water-resistant agent used in combination with a synthetic resin emulsion is effective in improving adhesion to aluminum and the intermediate layer, water resistance, plate-making image, etc. It was also superior to other substances. Furthermore, the film formation condition when applied to the aluminum surface was also good. Even if a mixture of other water-soluble film-forming substances such as starch and PVA with a water-resistant agent is used in combination with a synthetic resin emulsion for the anchor layer, the water resistance during printing is still insufficient, and the durability of the plate is insufficient. is inferior. Commonly used water-resistant agents include urea formaldehyde resin, melamine formaldehyde resin, polyamide formaldehyde resin, glyoxal, ketone aldehyde resin, epoxy polyamide resin, dialdehyde starch, chromium,
It is possible to select and use an appropriate water-resistant agent from various types of water-resistant agents such as metal salts such as zirconium and zinc, and by doing so, it is possible to obtain water resistance that does not interfere with normal printing. It is. The metal salt is a general term that includes metal salts of organic acids and inorganic acids, metal oxides, and the like. For example, Sachin White (3CaO・Al ₂ O ₃ , CaSO ₄・
_31-32H2O ), zinc sulfate, aluminum sulfate, borax, zirconium ammonium carbonate, aluminum, tin, and other metal chlorides. Considering the purpose, the coating amount of the anchor layer must first of all completely cover the aluminum surface, and for this purpose, the coating amount of the anchor layer must be at least 0.05μ. Even if the coating amount of the anchor layer is excessively increased, the adhesion does not improve correspondingly, but on the contrary, the following negative aspects arise. In other words, if the amount of the anchor layer applied is too large, the drying load of the coating film during coating will be large, and the crosslinking reaction by the water-resistant agent may not proceed sufficiently, and the coating film may become thick. As a result, fogging tends to occur in the plate-made image, which is of course economically disadvantageous. Therefore, the coating amount of the anchor layer needs to be 5.0μ or less. However, preferably,
It is 0.5-2μ. It goes without saying that the printing durability of this printing original plate is also affected by the composition and coating amount of the intermediate layer provided on the anchor layer. The ratio of synthetic resin emulsion to casein used in the anchor layer cannot be determined unconditionally since it varies depending on the type of synthetic resin, but it can be arbitrarily determined based on the point that provides the best adhesion and image quality. The ratio of casein to waterproofing agent is usually from 90:10.
A range of 70:30 is preferred, but of course it is not limited to this. Furthermore, within the range that does not impede the purpose of the anchor layer, for example, a pigment such as clay may be blended to increase smoothness, or a conductive agent may be blended to adjust the resistance value. An intermediate layer is provided on the anchor layer, and the intermediate layer here is a layer provided between the base material and the photosensitive layer, and a synthetic resin emulsion and/or a water-soluble polymer substance is optionally added. Pigments such as clay, calcium carbonate, aluminum hydroxide,
It is mixed with a conductive agent, a waterproofing agent, etc., and then applied. The coating amount of the intermediate layer is determined as appropriate depending on the intended printing durability of this printing original plate, but
Usually, a dry thickness in the range of 5μ to 20μ is preferred. The intermediate layer 1) increases the adhesion between the base material and the photosensitive layer, 2) has water resistance and prevents dampening water from penetrating into the base material during printing, and 3) prevents the solvent used when coating the photosensitive layer from penetrating the base material. It has the following functions: 4. It forms a complete film and prevents charge leakage (white spots) from the photosensitive layer; 5. It has an appropriate resistance value and maintains an appropriate image. In particular, it has the following functions: 2,
In order to make the functions of 3 and 4 sufficient,
A coating of 5-20 microns is required. In the present invention, the anchor layer uses aluminum laminate paper as the base material of the lithographic printing original plate, so 1. Shielding and protection of the aluminum layer. Oxidation progresses when the aluminum layer is exposed, making it impossible to coat the intermediate layer. 2. Improving the adhesion between the aluminum layer and the intermediate layer are particularly strongly required, and the present invention fully satisfies these requirements. In the present invention, the image-receiving layer (photosensitive layer) refers to a layer that is imaged by electrophotography and contains a photosemiconductor as a basic component.
Generally, inorganic optical semiconductor powders such as zinc oxide, titanium dioxide, and cadmium sulfide are dispersed in an insulating binder resin, and organic optical semiconductors such as polyvinyl carbazole are known. The present invention will be specifically explained below using examples. Example 1 Acrylic ester copolymer emulsion (Hoechst Synthesis, Movinyl 987) was applied as a laminating adhesive to a commercially available high-quality paper (100 g/m ² ) to give a dry weight of 2.0 g/m ² , and a 15 μm thick paper was coated. Laminated with aluminum foil. Next, an aqueous dispersion having the following composition was applied as an anchor layer to the aluminum surface opposite to the paper so that the dry thickness was 2.0 μm. Note that all "parts" shown below represent weight ratios in terms of pure content. (Composition) Acrylic ester copolymer emulsion (Hoechst Synthesis, Movinyl 987) 30 parts Casein (dissolved in hot water with a small amount of ammonia added) 60 parts Glyoxal 10 parts Next, using the aluminum laminated paper thus obtained as a base material, An intermediate layer was applied on top of the anchor layer. The composition is as follows and the coating amount is 10μ (thickness when dry)
And so. Clay 50 parts Acrylic acid ester copolymer emulsion (Hoechst Synthesis, Movinyl DM772) 50 parts Next, apply a coating liquid with the following composition as a back layer on the surface of the paper (the side opposite to the aluminum foil) at a concentration of 7.0 g/ ^m2 . It was applied like this. Polyvinyl alcohol (Kuraray, PVA-105)
30 parts acrylic ester copolymer emulsion (Hoechst Synthesis, Movinyl DM772) 50 parts quaternary ammonium type conductive agent (Dow Chemical,
ECR-77) 20 parts Next, a coating liquid having the following composition was coated as a photosensitive layer on the intermediate layer at a density of 22.0 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 sheet thus obtained was heated to 65% at 20℃.
An original plate for electrophotographic lithographic printing was obtained by dark adaptation in an atmosphere of 24 hours or more. Example 2 The same procedure as in Example 1 was carried out, except that in the above composition, an alkali-curing water-resistant agent, ketone aldehyde resin (Deck Hercules, Epinox P-468) was used instead of glyoxal. Comparative Examples 1 to 5 Comparisons were made in the same manner as in Example 1 except that the conditions of the anchor layer were changed. That is, there are cases where the coating amount of the anchor layer is changed depending on the composition, and cases where the composition is changed to a different composition, and the contents and results are summarized in Table 1. The evaluation method of the original plate in the above Examples and Comparative Examples is as follows. First, plate making was performed using a predetermined original drawing using an ITETSU 175 plate making machine. The plate surface was thoroughly wetted with absorbent cotton impregnated with etchant (manufactured by ITEC Corporation) and printed using a Toko 800 type printing machine. The dampening solution for 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.

[Table] As is clear from the above explanation, the present invention not only has excellent image quality, but also exhibits extremely excellent printing durability, and the advantages obtained by the present invention are enormous. be.

[Brief explanation of drawings]

FIG. 1 shows the structure of the present invention, and FIG. 2 is a sectional view of an original plate for electrophotographic lithographic printing using the base material of the present invention (FIG. 1). The names of each layer are as follows. 1...Base paper, 2...Lamination adhesive layer, 3...
Aluminum foil, 4... Anchor layer, 5... Base material, 6... Back layer, 7... Intermediate layer, 8... Photosensitive layer.

Claims (1)

[Claims] 1. An original plate for electrophotographic lithographic printing in which an anchor layer, an intermediate layer, and a photoconductive photosensitive layer are sequentially provided on the aluminum foil of aluminum foil laminated paper, wherein the anchor layer is made of synthetic resin emulsion, casein, and waterproofing. 1. An original plate for electrophotographic lithographic printing, characterized in that a coating liquid containing an agent as a main component is applied to a dry thickness in the range of 0.05μ to 5.0μ.