JPH0624168A - Manufacture of supporting body for lithographic printing plate - Google Patents

Abstract

PURPOSE:To provide a manufacture for a supporting body of a lithographic printing plate which shows no irregularity in appearance and is suitable as the supporting body for a lithographic printing plate, with having sufficiently uniform undulations. CONSTITUTION:Fine alumina particles are applied and dried on an elastic plastic sheet. The surfaces of the obtained sheets held by JIS 1050 aluminum plates from up and down are bonded each other and passed through metallic rolls, so that the pattern of the surfaces where the fine particles are applied is transferred to the aluminum plates. At this time the clearance of nip rolls is set to be 0.2mm smaller than the sum of the thickness of the plastic sheets and aluminum plates. The rate of elongation of the aluminum plate after the transfer is 15%. The average particle size of the fine particles is changed among nine kinds of size from 3mum to 40mum. When the surfaces of the plastic sheet and aluminum plate are observed through a scanning electron microscope, fine undulations corresponding to the pattern on the surface of the plastic sheet where fine particles are applied and dried are detected on the aluminum plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing plate support, and more particularly to a method for producing a printing plate support comprising a roughened aluminum plate suitable for offset printing plates.

[0002]

2. Description of the Related Art Conventionally, an aluminum plate has been widely used as a support for a lithographic printing plate, but it has good adhesion to a photosensitive layer provided thereon, and a lithographic printing plate produced by using the same. The purpose is to improve the water retention of the non-image area of the plate (the area that receives the dampening water used during printing and repels the oil-based ink, and the area where the surface of the support is exposed plays the role). As a general rule, the surface of the aluminum plate is roughened. This roughening treatment is called so-called graining, and is an indispensable step in the preparation of the lithographic printing plate support, and is a work that requires a considerable degree of skill. This graining is roughly classified into a mechanical graining method such as a ball grain, a wire grain, and a brush grain, and an electrical graining method. In the case of ball grain, there are many factors that require skill such as the material of the ball, the type of abrasive, the adjustment of water content during polishing, etc. Also, it is impossible to perform the work continuously and it is necessary to finish one by one. is there. In addition, the wire grain has non-uniform grain. On the other hand, brush grain is an improved version of these methods, and it is suitable for mass production because it has a uniform grain and can be continuously treated. However, it is difficult to obtain sufficient performance as a printing plate support by the above mechanical method.

Generally, when the surface roughness is large, the water retention (that is,
It is said that the water retentivity is improved, and when making a lithographic printing plate for the purpose of improving water retention and making printing easier, it is preferable that the surface shape of the support has unevenness as uniform as possible. It is said that. As a method for obtaining such a preferable surface shape, an electrochemical roughening method has been attracting attention. With this method,
If various conditions such as the composition of the electrolytic solution, temperature, and electrolysis conditions are kept constant, an aluminum plate having a constant roughened surface can be obtained, but the range of electrolysis conditions is very narrow,
Therefore, it is extremely difficult to perform electrolysis by adjusting so as to always keep it within such a range. Further, the electrochemical surface roughening is problematic from an economical point of view since it consumes a large amount of power. Moreover, the electrolysis causes a considerable amount of aluminum ions to be accumulated in the electrolytic solution, which has a drawback that the labor cost and the chemical fee for treating the waste solution reach a considerable amount.

Further, as a method of making unevenness on the aluminum surface, a method of using a rolling roll having a reverse graining surface is known in JP-A-55-74898, and a printing plate support is provided on the roll. It is very difficult to form a fine reverse graining surface suitable as In JP-A-60-36195 and JP-A-60-36196, a roll is used to form an elliptical press recess having an average major axis length of 10 to 140 μm and an average minor axis length of 7 to 80 μm, and then chemically. Alternatively, a method of electrochemically forming fine irregularities of 1 to 10 μm is described. Japanese Unexamined Patent Publication No. 60-203496 describes an aluminum plate on which irregularities having an average diameter of 10 to 100 μm are transferred by an embossed roll and then chemically and electrochemically etched.

[0005]

However, various methods for making the surface of the aluminum plate uneven by transfer as described above have been proposed by using uneven rolling rolls. It has been difficult to process sufficiently uniform and fine irregularities suitable as an aluminum support with high precision. Further, it is difficult to increase the processing accuracy such as the cylindricity of the transfer roll, and even if the processing accuracy is increased, the cylindricity of the transfer roll and the like change during the transfer. Therefore, when trying to transfer the fine irregularities on the surface of the transfer roll to the aluminum plate, there is a problem that unevenness in appearance is likely to occur on the surface of the aluminum plate.

The present invention solves the above problems, it is not necessary to set the rolling reduction to be so high, the elongation is not so large, and the lithographic printing plate support having sufficiently uniform irregularities suitable as a printing plate support. It is to provide a manufacturing method of.

[0007]

The above object of the present invention is to provide a support for a lithographic printing plate in which a surface having an uneven pattern is superposed on the surface of an aluminum plate and the uneven pattern is transferred to the surface of the aluminum plate by pressing. In the method for producing a body, the method for producing a lithographic printing plate support is characterized in that the uneven pattern is formed by fine particles, and the surface on which the uneven pattern is formed is a support having elasticity.

In the present invention, the fine particles forming the concavo-convex pattern are particles having a diameter of 0.3 to 40 μm, such as alumina, sand, silicon oxide, diamond, zirconia oxide,
Says particles such as tungsten carburt. Alumina particles are particularly preferable. The particle size distribution is preferably as uniform as possible. In the present invention, the support having an elastic surface refers to a support such as a sheet or film made of rubber or plastic, specifically polyester, polyethylene, polyethylene terephthalate, urethane, or a surface roll. The thickness is preferably 1-3 mils. In the present invention, the surface on which the concavo-convex pattern is formed refers to a surface having a surface coated with a liquid in which fine particles having a diameter of 0.3 to 40 µm are dispersed, or a surface having the fine particles embedded in the surface. Also, a material in which the fine particles are dispersed in the rubber or plastic,
Also includes sheets, films, or roll surfaces. The liquid in which fine particles are dispersed refers to a liquid in which fine particles are dispersed in water or a solvent, and a liquid in which an adhesive binder is added to water or a solvent and the fine particles are dispersed therein. A thickener may be added as necessary to adjust the viscosity of the liquid. After applying the liquid in which the fine particles are dispersed, it is preferable to perform a drying treatment. In the present invention, the surface of the surface coated with the fine particles or the surface embedded with the fine particles may be further coated with a resin for making it difficult for the fine particles to fall off from the surface. In the present invention, a support having an elastic surface on which an uneven pattern is formed and an aluminum plate are superposed, and the uneven pattern is transferred to the surface of the aluminum plate by pressing means that an aluminum plate for a lithographic printing plate, Two rolls having a narrower gap than the combined thickness of the aluminum plate and the sheet or film having a concave-convex pattern of fine particles, by superimposing the surface of the sheet or film having elasticity on which fine particles are coated and dried or embedded. It means passing pressure between the aluminum plate and the sheet or film. Alternatively, first, the aluminum plate and the elastic support having the concavo-convex pattern of the fine particles may be sandwiched between the rolls, and then mechanically external force may be applied so that the nip rolls are passed through. Metal, plastic, rubber or the like can be used for the two rolls having a gap or the nip roll for mechanically applying a force from the outside, but metal is preferable. Furthermore, in the present invention, fine particles are applied, dried or embedded on the surface of a plastic roll or a rubber roll as a support having elasticity to set a roll gap narrower than the thickness of an aluminum plate facing the plastic roll. Alternatively, the aluminum plate may be passed therethrough to apply pressure to the aluminum plate for transfer. In this case, metal, plastic, rubber or the like can be used for the roll facing the plastic roll or the rubber roll, but metal is preferable.

The aluminum surface roughened by transfer is chemically or electrochemically etched in an acid or alkali or neutral salt aqueous solution, and is then subjected to AC or DC or pulse DC in an acid or neutral salt aqueous solution. Electrochemically roughening the surface makes it more suitable as a printing plate support. The surface after etching is a method of forming unevenness on the aluminum plate by chemically or electrochemically etching after making unevenness on the surface by transfer, and then electrochemically roughening the surface. It is preferable that there is unevenness having an average diameter of 4 to 20 μm (more preferably unevenness having an average diameter of 4 to 10 μm). After the electrochemical roughening treatment, it is preferable that unevenness having an average diameter of 1 to 3 μm is overlapped on the surface after the etching treatment.

The aluminum plate having the uneven pattern transferred on the surface of the aluminum plate is then chemically or electrochemically etched in an aqueous solution of an acid, an alkali or a neutral salt to further support the printing plate. Will be suitable as. The acidic aqueous solution referred to in the present invention means an aqueous solution containing hydrochloric acid, sulfuric acid and nitric acid as main components. The alkaline aqueous solution means an aqueous solution mainly containing caustic soda. The processing time is preferably 5 to 120 seconds. The concentration is preferably 1 to 40%. The liquid temperature is preferably 35 to 75 ° C. If necessary, the aluminum plate may be subjected to cathodic electrolytic cleaning treatment in an acid or alkali aqueous solution. The neutral salt aqueous solution used in the present invention is an alkali metal halide or an alkali metal nitrate, preferably sodium chloride, sodium nitrate or sodium sulfate, having a pH of 5 to 9 and a concentration of 1 to 40%. The liquid temperature is preferably 35 to 75 ° C. When a neutral salt aqueous solution is used, it is necessary to use an aluminum plate as a cathode for electrolytic treatment. The cathode electrolysis treatment time is preferably 5 to 180 seconds. The aluminum plate treated in the neutral salt or alkaline aqueous solution is preferably further dipped in an aqueous solution of sulfuric acid, nitric acid or hydrochloric acid for the purpose of removing the smut component formed on the surface.

The aluminum plate thus treated may be further subjected to a chemical roughening treatment. As the electrochemical surface-roughening method, as described in JP-A-53-145701, a method of electrochemical surface-roughening treatment using an alternating current in an acidic aqueous solution may be used. 62
No. 1068, a method of electrochemically roughening the surface using an aqueous solution in an acidic aqueous solution, a neutral salt as described in Japanese Patent Application No. 3-6506. A method of electrochemically roughening the surface in an aqueous solution can be used. After performing the electrochemical surface roughening treatment, it is preferable to perform desmutting treatment in an acidic aqueous solution, modification treatment in an alkaline aqueous solution, and modification treatment using an aluminum plate as a cathode in a neutral salt aqueous solution. . Desmutting treatment in an acidic aqueous solution is disclosed in JP-A-53-12739.
It is publicly known in, for example, Japanese Patent Publication. A modification treatment in an alkaline aqueous solution is known in JP-A-56-139700. The modification treatment in a neutral salt aqueous solution is disclosed in JP-A-Sho 5
It is publicly known in, for example, 9-11295. Furthermore, the aluminum plate treated in this way is hydrophilic,
In order to improve water retention and printing resistance, anodizing treatment can be carried out in an electrolytic solution containing sulfuric acid or phosphoric acid by a conventional method. Further, the sealing treatment can be performed after the anodizing treatment. Further, it may be immersed in an aqueous solution containing sodium silicate or the like for hydrophilic treatment.

As the aluminum plate used in the present invention, either a pure aluminum plate or an aluminum alloy plate can be used. The aluminum plate described in the present invention has a sufficiently uniform rough surface suitable as an aluminum support for lithographic printing plates.

[0013]

EXAMPLES Examples of the present invention will be shown, but the present invention is not limited to these examples. (Example-1) A surface of an elastic plastic sheet (polyester) coated with fine particles of alumina and dried was laminated with a JIS1050 aluminum plate from above and below,
The pattern on the surface coated with fine particles was transferred to an aluminum plate by passing it between metal rolls. At this time, the clearance of the nip roll was 0.2 mm narrower than the thickness when the plastic sheet and the aluminum plate were combined. The elongation of the aluminum plate after transfer was 15%. The average particle size of the fine particles was changed from 0.3 μm to 40 μm under 9 conditions. When the surface of this plastic sheet and aluminum plate was observed with a scanning electron microscope,
Fine irregularities corresponding to the pattern were formed on the surface of the plastic sheet coated with fine particles and dried.

(Comparative Example 1) A non-elastic paper coated with fine particles of alumina was dried and laminated with a JIS 1050 aluminum plate from above and below, and passed between metal nip rolls to obtain a fine particle coated surface. The pattern was transferred to an aluminum plate. At this time, the clearance of the nip roll was 0.2 mm narrower than the thickness when the paper and the aluminum plate were combined. The elongation percentage of aluminum after transfer was 15%. The average particle size of the fine particles is 4 μm
Met. When the surface of this aluminum plate was observed with a scanning electron microscope, it was found that fine irregularities corresponding to the pattern of the surface obtained by coating and drying fine particles on paper were densely formed and coarsely generated. It was happening. It corresponds to the unevenness of the appearance on the paper side, and the appearance of the aluminum plate was inferior to the examples.

[0015]

[Table 1]

[0016]

As is apparent from Table 1, a surface suitable as an aluminum support for printing plates can be easily obtained by the production method of the present invention.

Claims (1)

[Claims] 1. A method for producing a lithographic printing plate support, wherein a surface having an uneven pattern formed thereon is superposed on the surface of an aluminum plate, and the uneven pattern is transferred to the surface of the aluminum plate by pressing. A method for producing a support for a lithographic printing plate, characterized in that the formed surface having an uneven pattern is a support having elasticity.