JPH0251751B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lithographic printing plate, and more particularly to an improved lithographic printing plate that is easy to develop, has less scuffing, and has excellent print image quality and printing durability. Conventionally, metal plates such as aluminum, zinc, magnesium, and multilayer metal plates, plastic films, and paper have been known as supports for lithographic printing plates. These include problems such as printing durability, difficulty in developing, quality of printed images, ease of staining during printing, adhesive strength between printing layer and support layer, plate cost, and ease of handling. Appropriate supports have been selected depending on the purpose of printing in terms of print quality, etc. Recently, with the development of automatic plate making and automatic printing methods, the popularity of simple lithographic printing plates has rapidly increased. For light printing purposes, paper-based lithographic printing plates have come to be widely used because they are inexpensive, easy to cut, punch, etc., and easy to handle. However, when using a paper-based material as a lithographic printing plate, paper, unlike metal plates or plastic films, easily absorbs water, which may cause the plate to expand or contract during printing or cause uneven surfaces. There are drawbacks such as unevenness or lack of water resistance, resulting in insufficient printing durability. In addition, in order to use it as a lithographic printing plate, it is important that it has appropriate water retention and is not smudged by printing ink. Therefore, in order to use paper as a support for a lithographic printing plate, it is necessary to perform water resistance treatment. For example, processed paper impregnated with a resin, coated, or laminated with an olefin resin such as polyethylene is known. However, a printing plate that is fully satisfactory in terms of water resistance, printing durability, ink stain resistance, etc., has not yet been obtained. In order to solve the above problems,
Publication No. 52-6202 and its improved method as JP-A-55-
A photosensitive lithographic printing plate is proposed in Publication No. 40406. That is, these publications disclose a photosensitive lithographic printing plate comprising a support having a base layer and at least one hydrophilic surface, and a photosensitive layer formed on the hydrophilic surface of the support layer. In the former case, the photosensitive layer is prepared by (A) precondensing an aromatic diazonium compound and an aldehyde compound in the presence of an acid, and adding a phenol compound to the resulting condensation polymerization reaction mixture. A mixture of a photosensitive modified diazo resin obtained by further condensation polymerization reaction and (B) a water-soluble acrylic acid-based polymer compound containing acrylic acid or its α- or β-substituted product as a polymerization component. a photosensitive lithographic printing plate, characterized in that the latter further comprises: a hydrophilic surface of the support and a surface of the base layer;
It is formed by the surface of a hydrophilic layer provided between the photosensitive layer, and this hydrophilic layer has a
Disclosed is a photosensitive lithographic printing plate characterized in that it is formed from a mixture containing a resin component consisting of 40 parts by weight of a urea resin, 60 to 95 parts by weight of a polyamide resin, and a pigment component. ing. Such a hydrophilic layer considerably improves the printing durability and developability of the resulting photosensitive lithographic printing plate, but it also impairs various aspects such as printing durability, scumming resistance, image quality, and development stability. Further improvements in properties were desired. That is, the hydrophilicity of the hydrophilic layer is not sufficient, which tends to cause scumming, and if the hydrophilicity is increased by lowering the degree of heat curing of the hydrophilic layer, developability and printing durability are reduced. It was hot. Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the conventional photosensitive lithographic printing plates, and to provide a photosensitive lithographic printing plate that not only can be easily developed but also has less background smudge and excellent printing durability. Our goal is to provide lithographic printing plates. The lithographic printing plate of the present invention comprises a support and at least one surface thereof containing 5 to 40 parts by weight of a urea resin.
In a lithographic printing plate having a hydrophilic layer formed from a mixture containing 60 to 95 parts by weight of a resin component consisting of a polyamide resin and a pigment component, acrylic acid or its α- or β-
Applying and permeating a mixture of a water-soluble acrylic acid polymer containing a substituted product as a polymerization component and a crosslinking agent,
It is characterized in that it is then thermally crosslinked. That is, the present inventors cured the hydrophilic layer provided on the support by heating sufficiently to the extent that developability and printing durability were satisfied, and then added the water-soluble acrylic acid polymer and its crosslinking agent. It has been found that developing properties, printing durability, and hydrophilicity can be satisfied at the same time by coating and permeating a mixture of the above hydrophilic layer onto the hydrophilic layer and then heating the mixture to crosslink the acrylic acid polymer. Ta.
The water-soluble acrylic acid polymer penetrates into the hydrophilic layer and makes the surface layer hydrophilic, and also crosslinks itself to become insoluble in water and maintains hydrophilicity during printing. Embodiments of the lithographic printing plate of the present invention will be explained with reference to the accompanying drawings, which schematically show the embodiments. In the planographic plate shown in FIG. 1, a hydrophilic layer 2 is provided on the upper surface of a support 1;
A water-retaining layer 3 made of the acrylic acid polymer that has penetrated into at least the surface of the hydrophilic layer 2 and is crosslinked by heating is formed. (Therefore, this water retaining layer 3
is formed on the hydrophilic layer 2 with a part of it penetrating into the hydrophilic layer 2. same as below. ) A backing layer 4 is provided on the lower surface of the support 1 as a water-resistant treatment layer. In the planographic plate shown in FIG. 2, a water-resistant layer 5 is formed on the upper surface of the support 1, and a hydrophilic layer 2 and a water-retaining layer 3 are provided on the upper surface. The support for the photosensitive lithographic printing plate of the present invention includes:
Generally, aluminum plates, zinc plates, copper plates, iron plates, resin plates, plastic films, paper, and composites of two or more of these can be used. In particular, in the case of a paper base, resin-coated waterproof paper, polyethylene laminated paper, various plastic film laminated papers, aluminum foil laminated paper, synthetic paper, etc. can be suitably used. In the present invention, a hydrophilic layer is provided between the support and the photosensitive layer in order to form a hydrophilic surface of the support. This hydrophilic layer is composed of a mixture containing a resin component consisting of 5 to 40 parts by weight of urea resin, 60 to 95 parts by weight of polyamide resin, and a pigment component. If the amount of urea resin in the resin component is less than 5 parts by weight and the amount of polyamide resin is more than 95 parts by weight, the adhesion between the photosensitive layer and the hydrophilic layer will be poor, and the durability of the resulting printing plate will be poor. Printability is also not required. Furthermore, if the amount of urea resin is greater than 40 parts by weight, and therefore the amount of polyamide resin is less than 60 parts by weight,
This results in drawbacks such as a decrease in developability, poor printing durability of the resulting printing plate, and increased likelihood of scumming. Urea-based resins include unmodified urea-formaldehyde resins and cation-modified urea-formaldehyde resins modified with one or more polyfunctional basic compounds having a plurality of basic groups in an amount of 5 to 20% based on the weight of urea. , 5 to 15% of the total amount of urea
selected from the group consisting of nonionically modified urea-formaldehyde resins modified with one or more polyol compounds, and anionically modified urea-formaldehyde resins modified with 5 to 15% acidic sulfite based on the weight of urea. at least 1
Preferably it is a seed. The polyfunctional basic compound is selected from, for example, dimethylaminoethanol, diethanolamine, oxazolidine, polyphenyl biguanide, tetraethylenepentamine, and guaylurea. Further, the polyol compound may be, for example, ethylene glycol, and
Selected from glycerin. Polyamide resins useful in the present invention include polyamides such as nylon 6, nylon 66, and nylon 610, and at least one of the polyamides modified with formaldehyde or a modifier consisting of formaldehyde and alcohol. ,
A modified polyamide resin, an epoxy-modified polyamide resin obtained by modifying at least one of the polyamides with a modifier comprising an epoxy compound, and a polyamine obtained by modifying at least one of the polyamides with a modifier comprising epichlorohydrin and a polyamine compound. It is preferably selected from the group consisting of modified polyamide resins such as epichlorohydrin modified polyamide resins. In each of the above-mentioned modified polyamide resins, it is preferable that 2 to 30% of the hydrogen atoms of the amide groups are substituted with the modifier residues. The pigment component to be mixed with the resin component to form the hydrophilic layer of the photosensitive lithographic printing plate of the present invention can be arbitrarily selected from, for example, titanium dioxide, acid clay, clay, or the like. In general, the pigment component is effective for improving the hydrophilicity and coating properties of the resin component, and is preferably used in an amount of 0.5 to 2.5 times the weight of the resin component, and preferably 1 to 1.5 times the weight of the resin component. More preferred. The above-mentioned resin components and pigment components may be treated with a suitable solvent, such as water, methanol, cellosolve, dimethylformamide, methyl ethyl ketone, acetone, xylene, ethyl acetate, or
A hydrophilic layer is formed by mixing with a mixture of two or more of the above compounds and applying the resulting coating liquid to a base layer. In order to improve the flexibility of this hydrophilic layer, polyvinyl alcohol, various modified polyvinyl alcohols, casein, and acrylic acid amide-acrylic acid ester copolymers are added to the resin component as described above in an amount of 0.01 to 1 times its weight. , auxiliary resin such as modified polyacrylic acid may be mixed. A small amount of sulfate may also be added. In the present invention, in order to further improve the hydrophilicity of the hydrophilic layer, a mixture of a water-soluble acrylic acid polymer and a crosslinking agent is coated and infiltrated, and then crosslinked and cured to obtain a lithographic printing plate with good hydrophilicity. I got it. The polymer compound of acrylic acid or its α- or β-substituted product used in the present invention is
Water-soluble polymer compounds such as polyacrylic acid, polymethacrylic acid, acrylic acid-methacrylic acid copolymers, polyacrylic ester partial oxides, polymethacrylic ester partial oxides, and mixtures of two or more of the above polymers. You can choose from. These polymer compounds have an average degree of polymerization of 500~
It is preferably within the range of 2000, and a mixed solvent of water and a water-soluble organic solvent may be used to infiltrate the water-soluble acrylic acid polymer into the cured hydrophilic layer. There is no particular restriction on the blending ratio of the organic solvent, and it may be selected so that the acrylic acid polymer can appropriately penetrate into the hydrophilic layer. The following are suitable as such organic solvents. Acetone, methyl ethyl ketone, methyl-n-
Propyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, methyl cellosolve,
Ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, methanol,
ethanol, propanol, isopropanol,
These are butanol, cyclohexanol, dimethylformamide, and dimethylacetamide. Examples of crosslinking agents for water-soluble acrylic acid polymers include methylol compounds such as methylol urea and methylol melamine, polyethylene glycol dicrycidyl ether, glycerol diglycidyl ether,
Any material may be used as long as it reacts with the acrylic acid polymer and is easily crosslinked, such as epoxy compounds such as triglycidyl isocyanurate, organic titanates, and metal chelate compounds such as aluminum chelate compounds. Moreover, a crosslinking catalyst can be used in combination if necessary. There are no particular restrictions on the curing conditions for the acrylic acid polymer, but for example, 0.5 to 20 parts by weight of the above-mentioned crosslinking agent may be blended with 100 parts by weight of the acrylic acid polymer, and the type and amount of the crosslinking agent may be adjusted. Depending on the situation, it is usually preferable to heat treat at a temperature of 120 to 180°C for several seconds to 20 minutes. In addition, if the amount of the crosslinking agent is too large or the heating conditions are too strong, the hydrophilicity will decrease, which is not preferable. In addition to the hydrophilic layer and the water-retaining layer, the photosensitive lithographic printing plate of the invention may include a water-resistant layer between the surface of the support and the hydrophilic layer. In the planographic plate shown in FIG. 2, a water-resistant layer 5 is formed on the upper surface of the support 1, and a hydrophilic layer 2 is formed on the upper surface. The upper surface of the hydrophilic layer 2 forms a hydrophilic surface, and a photosensitive layer 6 is formed thereon. FIG. 3 shows that an image 6 is formed on the water retaining layer 3,
The hydrophilic surface of the water-retaining layer 3 is exposed and acts as a water-retaining surface for dampening water during printing. This water-resistant layer is made of a water-resistant resin such as polyvinyl chloride, polyurethane, aldehyde condensation of polyvinyl alcohol, acrylic acid ester-styrene copolymer, methacrylic acid ester-styrene copolymer, or styrene-butadiene copolymer, or aluminum foil. It can be formed using The base material used in the printing plate of this embodiment may be any of the above-mentioned base materials, but in particular, base materials with relatively low water resistance such as paper may also be used. In order to improve smoothness during coating, titanium dioxide or the like may be mixed into the water-resistant resin in an amount of 0.3 to 4.0 times, preferably 0.8 to 2.0 times, the weight of the solid resin. The coating amount of the water-resistant layer is preferably 5 to 20 g/m ² , more preferably 8 to 12 g/m ² . The photosensitive composition that can be used in the lithographic printing plate of the present invention is preferably one that can be coated with water or a mixed solvent of an organic solvent and water, such as diazo resin, JP-A No. 55-40406. Any of the phenol-modified diazo resins and other water-soluble photosensitizers described in the publications can be used. The present invention will be explained below with reference to Examples. In the examples, "parts" and "%" are by weight unless otherwise indicated. Example Paper with a basis weight of 150 g/m ² (N/L
= 50/50) was used. To form a water-resistant layer,
Acrylic resin emulsion was uniformly applied to both sides of the above paper at 16 g/m ² on each side and dried. On one side of this coated paper, a hydrophilic layer coating solution having the following composition was prepared, coated on the water-resistant layer, and heat-treated at 150° C. for 3 minutes. The coating weight of layer A thus formed was 13 g/m ² . Composition Anatase type TiO ₂ 500 Sodium polyacrylate 2 Water 1200 Water-soluble polyamide resin (10% methylol-modified nylon 6) 400 (solid content) Cation-modified urea resin (10% diethanolamine-modified urea resin) 200 (solid content) NH ₄ Cl 10 Separately, dissolve water-soluble acrylic acid polymer (30% methacrylic acid groups, degree of polymerization approximately 1000) in a mixed solvent of 70% water, 25% methyl ethyl ketone, and 5% isopropyl alcohol, and place 0.2 g on top of layer A. /m ² thickness and dried at 100° C. for 3 minutes to form layer B. Separately, a composition was prepared in which 5% of polyethylene glycol diglycidyl ether was added to the water-soluble acrylic acid polymer in a mixed solvent with the same water-soluble acrylic acid polymer used to form layer B. Coating on the layer A to a thickness of 0.2 g/m ² ,
Layer C was formed by heating at 150° C. for 2 minutes. Next, a coating solution for a photosensitive layer was prepared as follows. 230 parts of 4-diazodiphenylamine sulfate was added to 200 parts of phosphoric acid with stirring and well dispersed.
Next, add 30 parts of paraformaldehyde to this,
The reaction was carried out at 40°C for 24 hours with stirring. Next, 94 parts of phenol were added, followed by 15 parts of paraformaldehyde and 200 parts of phosphoric acid, and the mixture was allowed to react at 50°C for 24 hours while stirring well. The resulting reaction mixture was dispersed in a large amount of water, and the precipitate was filtered and washed with water to obtain 310 parts of a yellow photosensitive diazo resin.
This diazo resin had good storage stability, and no change was observed even after it was left at room temperature for 6 months. The modified photosensitive diazo resin obtained above and methyl cellulose were dissolved in a solid ratio of 3:1 in a mixed solvent of 60% water, 25% methyl ethyl ketone, 10% isopropyl alcohol, and 5% ethanol, and photosensitive I made a composition. This combination was applied to the treated paper having layers A, B and C to a thickness of 0.6 g/m ² and dried at 90° C. for 3 minutes. A negative film was attached to the three types of negative photosensitive lithographic printing plates A, B and C thus produced, and exposed for 40 seconds from a distance of 1 m using a 2 KW ultra-high pressure mercury lamp. Next, a 2.4% aqueous solution of sodium carbonate was poured onto the print, and the print was developed by immediately wiping it with a sponge. Lithographic printing was performed using these three types of printing plates. The results were as shown in Table 1.

[Table] As can be seen from this result, printing plate B, in which the water-soluble acrylic acid polymer was infiltrated into the hydrophilic layer but not actively crosslinked, has a hydrophilic property that allows printing, but during the printing process. The water-soluble acrylic acid polymer gradually loses its hydrophilicity as it dissolves into dampening water.
Also, the printing durability is not sufficient. Permanent hydrophilicity and sufficient printing durability can only be obtained in printing plate C in which a water-soluble acrylic acid polymer is actively crosslinked. Example A hydrophilic layer of the same composition as in the example was applied to a thickness of 12 g/m ² on one side of synthetic paper (YUPO FP manufactured by Oji Yuka Synthetic Paper Co., Ltd., 150 μm thick) mainly consisting of polypropylene and filler. It was cured by heating at 130°C for 20 minutes. This hydrophilic layer was infiltrated with a water-soluble acrylic acid polymer using the same composition and treatment method as in the example, and
Crosslinking was carried out by heating for a minute. Next, the modified diazo resin and water-soluble acrylic acid polymer (30% methacrylic acid groups, degree of polymerization 1000) were mixed in a solid ratio of 2:1 with 10% ethyl cellosolve, 20% acetone, 20% methyl ethyl ketone, and 50% water. % of the photosensitive composition dissolved in a mixed solvent was applied to the coated synthetic paper described above to a thickness of 0.7 g/m ² and dried at 90° C. for 3 minutes. When a printing test was conducted using the photosensitive lithographic printing plate thus prepared, it had good developability and could be printed on up to 3,000 sheets without causing scumming.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of one embodiment of the planographic printing plate of the present invention, FIG. 2 is an explanatory cross-sectional view of another embodiment of the planographic printing plate of the present invention, and FIG. FIG. 2 is a cross-sectional explanatory diagram after exposure and development when a lithographic printing plate is used as a printing plate. 1...Support, 2...Hydrophilic layer, 3...Water retention layer,
4...Backing layer, 5...Waterproof layer, 6...Developed image.

Claims (1)

[Claims] 1 a support and at least one side thereof, 5 or
In a lithographic printing plate having a hydrophilic layer formed from a resin component consisting of 40 parts by weight of a urea resin and 60 to 95 parts by weight of a polyamide resin, and a mixture containing a pigment component, acrylic acid or its A lithographic printing plate characterized in that a mixture of a water-soluble acrylic acid polymer containing an α- or β-substituted product as a polymerization component and a crosslinking agent is coated and infiltrated, and then crosslinked by heating.