JPH0430357B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an inexpensive lithographic printing plate material having high printing durability, and more particularly to a lithographic printing plate material in which a hydrophilic layer constituting a hydrophilic non-image area is made of a polymer compound whose surface is sulfonated. It is. In general, planographic printing plates consist of a hydrophilic non-image area that accepts water from a water roller during printing but does not accept oil-based ink from an ink roller, and an oleophilic image area that accepts oil-based ink from an ink roller. has been done. The hydrophilic non-image area includes:
Aluminum is usually used because it has excellent printability and printing durability. However, this material has problems such as expensive materials and changes in hydrophilicity due to surface deterioration due to oxidation or the like. Therefore, hydrophilic polymer compounds such as gelatin, casein, starch, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and polyvinylpyrrolidone are crosslinked and insolubilized to form inexpensive hydrophilic non-image areas other than aluminum. Depending on the situation, pigments such as clay, calcium carbonate, aluminum oxide, and silica are added, but all of these do not have sufficient water resistance and have poor dimensional stability and printing durability. There's a problem. In addition, attempts have been made to solve the above problems by performing hydrophilic treatment only on the surface of the water-resistant base material,
For example, a cellulose acetate sheet whose surface is partially saponified, a water-resistant plastic substrate whose surface is graft-polymerized with a monomer such as acrylamide (Japanese Unexamined Patent Publication No. 17407/1983),
Alternatively, a material in which the surface of a water-resistant lipophilic base material is made hydrophilic by corona discharge has been proposed (Japanese Unexamined Patent Publication No. 124708/1983). However, all of these have drawbacks such as insufficient abrasion resistance during printing, and although the contact angle with water is less than 20 degrees, printing stains are likely to occur during printing. It is difficult to In view of these circumstances, the present inventors have conducted intensive research to provide a lithographic printing plate material having a hydrophilic non-image area with excellent printability and printing durability.
Water absorption rate as a base material constituting the hydrophilic non-image area
We have found that this objective can be achieved by sulfonating the surface of a non-aromatic polymer compound of 0.2% or less to make it hydrophilic, and using a material whose contact angle with water is below a predetermined value. Based on this knowledge, we have completed the present invention. That is, in the present invention, the hydrophilic layer constituting the hydrophilic non-image area absorbs ⁵ ×10 ⁻⁵ milliequivalent to 1×10 The object of the present invention is to provide a lithographic printing plate material which is sulfonated in the range of ^-1 milliequivalent and whose surface has a contact angle with water of 40 degrees or less. Generally, it is a well-known fact that hydrophilicity can be imparted to a polymer compound by introducing a hydrophilic group or a polar functional group such as a hydroxyl group, a carboxyl group, a sulfone group, or a phosphate group. However, these materials usually have poor water resistance and cannot be used as printing plates. In addition, printing plate materials have been proposed in which hydrophilic groups such as those described above are introduced by chemical conversion treatment on the surface of lipophilic resin (Japanese Patent Laid-Open No. 118501/1983), but this method also prevents stains in non-printing areas. I am still not satisfied with the printing power. However, the surface of a non-aromatic polymer compound with a water absorption rate of 0.2% ^or less can be made hydrophilic by sulfonating in the range of 5 x 10 ^-5 milliequivalent to 1 x 10 ^-1 milliequivalent per cm 2 of surface area. When using a material whose surface has a contact angle with water of 40 degrees or less as a hydrophilic non-image area of a lithographic printing plate, its excellent hydrophilic action allows for good retention of dampening water during printing. It can be an excellent plate material with no stains in non-image areas, excellent water resistance and dimensional stability, and good printing durability. If the contact angle exceeds 40 degrees, printing stains occur in non-image areas. The polymer compound used in the present invention needs to have a water absorption rate of 0.2% or less. If the water absorption rate exceeds 0.2%, if sulfonation is performed until the contact angle with water on the surface becomes 40 degrees or less,
Dimensional stability and printing durability are significantly reduced, making it undesirable as a printing plate material. Note that the water absorption rate here refers to the weight increase rate when immersed in water at a temperature of 20°C for 24 hours. The non-aromatic polymer compound may be one selected from olefin compounds such as ethylene, propylene, and butene-1, and halogenated unsaturated compounds such as vinyl chloride, vinylidene chloride, and vinylidene fluoride; Examples include polymer compounds with a water absorption rate of 0.2% or less obtained by polymerizing two or more types of monomers. By the way, examples of polymer compounds with a water absorption rate of 0.2% or less include aromatic polymer compounds such as polystyrene in addition to those mentioned above.Furthermore, this compound is known to be easily sulfonated, but it is difficult to sulfonate. At this stage, when the contact angle with water on the surface becomes less than 40 degrees and it develops hydrophilic properties suitable for offset printing, some of the sulfonated resin is eluted from the surface, and the size and printing durability of the plate are also affected. There is a tendency for the properties to decrease, making it difficult to obtain excellent printing plates. Although it is possible to improve this by copolymerizing a portion of styrene with divinylbenzene, it causes many problems in processing and is not suitable for the method of the present invention. Therefore, what is used in the present invention is the water absorption rate.
It is a non-aromatic polymer compound containing 0.2% or less, and polyolefin compounds are particularly preferably used. In the present invention, a film or sheet of these polymer compounds may be used alone, or the film or sheet may be bonded to another base material to form a composite material. There are no particular restrictions on the thickness of these films or sheets, but those in the range of 0.001 to 1.0 mm are usually preferably used. When used as a composite material, a film or sheet of a polymer compound may be sulfonated and then bonded together, or a composite material may be bonded and then sulfonated. Sulfonation of the surface of the non-aromatic polymer compound in the present invention is carried out so that the contact angle with water on the surface is 40 degrees or less, preferably 30 degrees or less, in order to make it suitable as a printing plate material. be exposed. There are no particular limitations on the method of sulfonation; for example, the film or sheet of the polymer compound may be immersed in fuming sulfuric acid, or the sulfuric anhydride may be used as it is, or the sulfuric anhydride may be immersed in dry air, nitrogen, etc. It may be used by diluting it with a gas or an organic solvent that is relatively inactive toward sulfuric anhydride, such as chloroform, carbon tetrachloride, or ethylene dichloride. In particular, a sulfonation method using sulfuric anhydride is suitable for polymer compounds that are likely to be accompanied by hydrolysis reactions. Further, the degree of sulfonation varies depending on the type of polymer compound used, but it may generally be in the range of 5×10 ⁻⁵ to 1×10 ⁻¹ milliequivalent per cm ² of surface area in terms of exchange equivalent. If this amount is less than 5×10 ^-5 milliequivalent, when used as a printing plate material, ink will adhere to the non-image area and stains will occur, and if it exceeds 1×10 ^-1 milliequivalent, the dimensions will be unstable during printing. The durability and printing durability tend to decrease. Note that during printing, it is desirable that the sulfone group be neutralized with a base such as sodium hydroxide or ammonia. Furthermore, since the optimum degree of sulfonation differs depending on the type of polymer compound, it is determined by the contact angle of the sulfonated polymer compound with water on the surface of the film or sheet. In other words, when a sulfonated film or sheet with a contact angle of more than 40 degrees with water is used as a base material for a hydrophilic non-image area, ink adheres to the non-image area and print stains occur; When using a material with a contact angle of 40 degrees or less with water, excellent printed matter can be obtained without causing printing stains. The critical value of the contact angle with water, 40 degrees, is higher than that of commonly used aluminum-based materials, and is a value unique to polymer compounds whose surfaces are sulfonated. This is due to the extremely rough surface of the film or sheet of a polymer compound sulfonated to a predetermined degree of sulfonation, and the ionic bonding force between the sulfone group and water. This is thought to be because it is specifically affected. In the plate material of the present invention, a lipophilic image area is formed on the hydrophilic surface layer made of a film or sheet of a non-aromatic polymer compound whose surface is sulfonated in this way, or a lipophilic image area is formed on the hydrophilic surface layer. It is obtained by removing or altering a portion corresponding to the image portion. The former image area is formed by coating a photosensitive agent on a hydrophilic surface layer and drying it to form a photosensitive layer, which is exposed to light through an original plate such as a negative or positive plate, in the same way as a normal planographic method. This is done by developing. Examples of the photosensitizers used here include known ones, such as photosensitive materials centered on dichromate-based, diazonium salt-based, o-quinone diazide-based, silicate ester-based, and photopolymerization-based photosensitive resins. It will be done. Other methods for forming image areas include drawing, printing, transferring, and stamping directly on the surface layer using ink or paint, and toner image forming methods using electrophotography. In addition, as a method for creating an image area by removing or denaturing the portion of the hydrophilic surface layer corresponding to the image area,
Mechanical or thermal methods can be used. For example, a drawing may be made by scraping only the surface with a pencil or cutter, or it may be thermally removed using a laser. Printing using the lithographic printing plate material of the present invention can be performed using a normal offset printing machine. At this time, simple water is sufficient as the dampening water, and no special dampening water is required. In addition, there is no need for etching gum before printing, and there is no need for special treatment after printing is completed for reprinting, and the lithographic printing plate material of the present invention improves work efficiency in lithographic offset printing. This is a great contribution. Next, the present invention will be explained in more detail with reference to Examples. The amount of sulfonation was determined as follows. That is, a film with a sulfonated surface (surface area Mcm ² ) is immersed in a 1N aqueous calcium chloride solution to reach an equilibrium state, and the hydrogen chloride generated in the aqueous solution is immersed in a 0.1N aqueous sodium hydroxide solution (potency: f) to determine the neutralization value (Xc.c.) using the indicator phenolphthalein, which is calculated using the following formula. Amount of sulfonation (milliequivalent/cm ² )=0.1·f·x/M Further, the contact angle with water was determined by the droplet method. Example 1 A reaction vessel was set at a temperature of 30 to 50°C, and a polyethylene film (water absorption rate of 0.01% or less) having a thickness of about 200 μm was set in a dry glass vessel. On the other hand, a gas generator containing sulfuric anhydride was kept at about 30°C, and anhydrous sulfuric acid gas obtained by introducing dry nitrogen gas from the outside was introduced into the reaction vessel, and the reaction was carried out for about 15 minutes. . After the reaction was completed, the film was taken out from the container, immediately neutralized with an aqueous sodium hydroxide solution, thoroughly washed with water, and then dried. The contact angle of this film was 17 degrees, and the amount of sulfonation was 3×10 ⁻² milliequivalents/cm ² in terms of exchange equivalents. In this way, ultraviolet curing ink (Bestcure, BF-WRO Sumi, manufactured by Toka Shiki Co., Ltd.) was transferred onto the surface of the sulfonated polyethylene film using a letterpress proofing machine (manufactured by Bandar Tsukku Co., Ltd.). The ink image was cured and adhered onto the hydrophilic surface by irradiation with a high pressure mercury lamp at a distance of 1 m for 3 minutes. When the printing plate created in this way was attached to an offset printing machine (Hamaduster 700CD) and printing was performed using tap water as dampening water,
There was no staining in the non-image area, and 10,000 sheets could be printed, and further printing was possible. Furthermore, when this plate was left to stand overnight without any additional operations such as gumming, and then printed again, it was possible to print without any stains in the non-printed areas. Example 2 A polypropylene film (water absorption rate of 0.01% or less) having a thickness of about 200 μm was immersed in fuming sulfuric acid containing about 10% by weight of sulfuric anhydride for 10 minutes to carry out a sulfonation reaction. After the reaction was completed, the film was taken out from the reaction solution, thoroughly washed with water, neutralized with aqueous ammonia, further washed with water, and dried. The contact angle of this film was 25 degrees, and the amount of sulfonation was 1×10 ⁻¹ milliequivalent/cm ² in terms of exchange equivalent. On the surface of the polypropylene film whose surface had been sulfonated in this way, a film was prepared by the method described in Example 1 of Japanese Patent Publication No. 49-34041.
A photosensitive resin consisting of an acrylic resin having an unsaturated group in the side chain, a monomer, and a photosensitizer is applied using a wire bar so that the coating amount after drying is 4 g/m ² to form a photosensitive layer. Established. Next, apply a negative film to the surface of this heat-sensitive layer,
From a distance of 1m using a water-cooled 3KW ultra-high pressure mercury lamp
After 60 seconds of exposure, 1% by weight of sodium phosphate
Development was carried out with an aqueous solution consisting of 10% by weight of methanol and 10% by weight of methanol, and the unexposed areas of the photosensitive layer were removed to provide a lipophilic image area on the hydrophilic surface. When the printing plate thus prepared was printed in the same manner as in Example 1, good printed matter was obtained. Examples 3 to 6, Comparative Examples 1 to 4 Various resin films were subjected to a sulfonation reaction in the same manner as in Example 1, and a printing test was conducted to obtain the results shown in the following table.

【table】

[Table] *Made by Asahi Dow Co., Ltd. Copolene (registered trademark)

Claims (1)

[Claims] 1 The hydrophilic layer constituting the hydrophilic non-printing area has a water absorption rate of
0.2% or less of the surface of a non-aromatic polymer compound per ¹ cm2 of surface area, 5 x 10 ^-5 milliequivalent to 1 x 10 ^-1
1. A lithographic printing plate material which is sulfonated in the milliequivalent range and whose surface has a contact angle with water of 40 degrees or less.