JPH01207739A - Plate material for planographic printing - Google Patents

Abstract

PURPOSE:To obtain a plate material for planographic printing which has high stability as a product and has high sensitivity by specifying a copolymer to be incorporated into an aq. alkaline soln. to prepare the compsn. of a photosensitive layer. CONSTITUTION:This plate material is constituted by providing the photosensitive layer on a sanded aluminum sheet. The photosensitive layer consists of (a) the component selected from methyl methacrylate, styrene, acrylonitrile, and tert-butyl methacrylate, (b) the component selected from n-butyl acrylate, 2- ethylhexyl acrylate and dodecyl methacrylate, and (c) at least one kind among copolymerizable org. acids. The copolymn. ratios are 40-80wt.% component (a), 5-20wt.% component (b) and 15-40wt.% component (c). The sensitivity is thereby improved and thermal fogging is hardly generated; in addition, the adhesiveness is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a lithographic printing plate material that has high sensitivity, high resolution, and can be developed with an alkaline aqueous solution.

[Prior Art] Conventionally, various materials in which a photosensitive resin is coated on grained aluminum have been published and used as plate materials for lithographic printing. As the photosensitive resin, an 0-quinonediazide-novolac resin type is used for a positive type, and a diazo resin type, a photocrosslinking type represented by polyvinyl cinnamate, and a photopolymerization type are used for a negative type. Among these, solvent-developable ones such as polyvinyl cinnamate are undesirable from the viewpoint of pollution problems, occupational health, danger, and total cost.For this reason, currently alkaline-developable 〇-quinone diazido novolak resin types, and water-developable diazo resin types are widely used.

However, these photosensitive resins have the problem that sensitization is difficult and the sensitivity cannot be increased beyond the current level.

For example, higher sensitivity is required for projection exposure systems from microfilm, so-called enlarging plate-making systems, and scanning exposure systems using lasers such as argon.

In this regard, the photopolymerizable type allows for chain polymerization and allows for the selection of sensitizers, so high sensitivity can be expected. Special Public Service No. 46-32714
The publication discloses a system using a water-insoluble acrylic acid ester, which is an ethylenically unsaturated compound, as a photopolymerizable photosensitive resin for use in the photosensitive resins. However, the publication only mentions methyl methacrylate/methacrylic acid copolymer or styrene/itaconic acid copolymer as the polymer binder, and it is intended to increase sensitivity and improve printability. There is no description of the composition of the copolymers belonging to the present invention.According to the experiments of the present inventors, although some performance can be obtained using these copolymers, the flexibility of the photosensitive layer is insufficient. The sensitivity did not rise above a certain limit, and the adhesion of the photosensitive layer to the plate substrate was somewhat insufficient, which caused problems in the reproducibility of fine lines and stiffness.

[Problems to be Solved by the Invention] In order to eliminate the above-mentioned drawbacks, the present inventors focused on the composition of the photosensitive layer of a lithographic printing plate material, and as a result of conducting extensive research,
This led to the present invention.

An object of the present invention is to provide a lithographic printing plate material which can be developed in an aqueous solution system, has high stability during the manufacturing process and as a product, and has high sensitivity.

[Means to solve problems]

It consists of a photosensitive layer on a grained aluminum plate.
In a planographic printing plate that can be developed in an alkaline aqueous solution,
The photosensitive layer includes (a) at least one selected from methyl methacrylate, styrene, acrylonitrile, and tert-butyl methacrylate; (b) at least one selected from n-butyl acrylate, 2-ethylhexyl acrylate, and dodecyl methacrylate. and (1) at least one type of copolymerizable organic acid, with a copolymerization ratio of (a) component of 40 to 80 weight percent, (b) component of 5 to 20 weight percent, and (3) component 40 to 60% of the copolymer containing 15 to 40% by weight of the component.
The present invention is a lithographic printing plate material characterized in that it is formed from a photosensitive resin containing an ethylenically unsaturated compound in an amount of 10 to 60 percent by weight and a photopolymerization initiator in an amount of 1 to 20 percent by weight.

[Function] The composition of the photosensitive layer of the present invention includes a copolymer that is soluble or swellable in an alkaline aqueous solution, and furthermore, this copolymer contains (a) methyl methacrylate, styrene, acrylonitrile, methacrylic acid tert- consisting of at least one selected from butyl, (a) at least one selected from n-butyl acrylate, 2-ethylhexyl acrylate, and dodecyl methacrylate, and (t) at least one copolymerizable organic acid; As copolymerization ratio (
A) Ingredients are 40 to 80% by weight, (B) Ingredients are 5% by weight.
-20% by weight and 15-40% by weight of component (A), which provides mechanical strength and resistance to alkalis or acids during development and corrosion; ) The component has alkali solubility in the non-exposed area which enables development with an alkaline aqueous solution.

In addition, component (a) is responsible for improving adhesion to aluminum, improving sensitivity, improving image quality, and improving reproduction of fine lines. In order to prevent oxygen inhibition, it is preferable to provide a water-soluble resin layer such as PVA on the photosensitive layer, but in this case (a)
If there are too many components, distortion will occur between both layers, causing a few microns on the surface.
Characteristics of high sensitivity and high image quality can only be obtained with the above composition, such as 0 or more where m unevenness occurs. This copolymer is a simple system made by simply polymerizing compounds that are stable as monomers, so it changes little over time and does not cause fogging. Even in the initiator formulation, image formation is achieved for the first time by using the above-mentioned compounds and compounding ratios.
Desired characteristics can be obtained. Furthermore, since it has high ink affinity and is not attacked by ink solvents, it has good ink adhesion and good rigidity resistance.

[Details of the invention] The present invention will be explained in detail below.

As a substrate, a grained aluminum plate is suitable because it has good adhesion to the photosensitive layer and has water retention properties during printing. Further, hydrophilic treatment by anodization or surface chemical treatment is preferable. Examples of surface chemical treatment include treatment with silicate, phosphate glass, carboxylic acid polymer, sulfonic acid polymer, or zirconium fluoride salt.

The copolymer includes (a) at least one selected from methyl methacrylate, styrene, acrylonitrile, and tert-butyl methacrylate; (b) n-acrylate;
At least one selected from butyl, 2-ethylhexyl acrylate, and dodecyl methacrylate, and (a) a copolymerizable organic acid can be used. Examples of copolymerizable organic acids include organic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, cinnamic acid, fumaric acid, and maleic acid; monomethyl dibasic acids such as itaconic acid;
Examples include monoesters such as monoethyl. Particularly preferred copolymerizable organic acids are methacrylic acid and acrylic acid.

As a copolymerization ratio of the copolymer of the present invention, component (A) is 40 to
80% by weight, component (a) from 5 to 20% by weight, and component (t) from 15 to 40% by weight. The most preferable among these component ratios is (a)
Ingredient 40-60ffi amount percent, component (A) 5
~20 weight percent (1) copolymerizable organic acid 15
~30 weight percent copolymer.

For the production of the copolymer, conventional polymerization methods can be used, but radical polymerization is particularly preferred. In addition, solution polymerization is preferred as a means of polymerization; however, in this case, if any radical polymerization initiator remains, it may cause heat fog, so care must be taken to decompose it by sufficient heating or remove it. do.

The acid value of the obtained copolymer is 50 to 200, preferably 100 to 150. In addition, the weight average molecular weight is 1000 to 100000, preferably 3000 to 5
There are 0000 te.

As the ethylenically unsaturated compound, a compound having two or more ethylenically unsaturated groups is suitable. For example, trimethylolpropane diacrylate, triacrylate,
Examples include dimethacrylate and trimethacrylate, diacrylate, triacrylate, tetraacrylate, dimethacrylate, trimethacrylate, and tetramethacrylate of pentaerythritol, or acrylates and methacrylates corresponding to the above of dipentaerythritol. .

Also, depending on the purpose, compounds having only one ethylenically unsaturated group, epoxy acrylate, acrylamide, urethane acrylate, N.

N-methylenebisacrylamide, etc. can be added.

Examples of photopolymerization initiators include aromatic ketones such as benzophenone, jetoxybenzophenone, chloromethylated benzophenone, Michler's ketone, 4,4-bis(diethylamino)benzophenone, ethylanthraquinone, 2-chlorothioxanthone, and other ketones; Benzoin, benzoin ethers such as benzoin isopropyl ether, benzyl dimethyl kecool and other benzoins, and as the 2,4,5-1-lyarylimidazole dimer, 2-(o-chlorophenyl)-4,5-diphenylbiimidazole , 2-(o-
Chlorophenyl)-4,5-di(m-methoxyphenyl)biimidazole and the like may be used alone or in combination. The most preferred among these are 4,4-bis(diethylamino)benzophenone and 2-(o-chlorophenyl).
The combination of -4°5-diphenylbiimidazole has the highest sensitivity when using an ultra-high pressure mercury lamp or metal halide lamp as a light source.

The photosensitive layer constituting the present invention mainly contains a copolymer that dissolves or swells in an alkaline aqueous solution, an ethylenically unsaturated compound, and a photopolymerization initiator. Their blending ratio is 40 to 60 weight percent copolymer and 6 percent ethylenically unsaturated compound.
The copolymer content is preferably 0 to 10% by weight, and the photopolymerization initiator is preferably 1 to 20% by weight. If the amount of the copolymer is too small, the developability in an alkaline aqueous solution will be poor, and if it is too large, the sensitivity will be insufficient.

If the amount of ethylenically unsaturated compound is too low, the sensitivity will be insufficient, and if it is too high, it will be highly sticky and cause problems such as blocking, and the adhesion to aluminum after exposure and development will be poor.
If the photopolymerization initiator is too small, the sensitivity will be insufficient, and if it is too large, only the surface will be hardened by exposure, and the physical properties will tend to deteriorate.

A color developer that develops color by image exposure can be added to the photosensitive layer constituting the present invention. As the color developer, leuco dyes such as leuco crystal violet and leucomalachite green can be used.

Furthermore, colorants such as dyes and pigments can be added as necessary. As dyes, basic dyes or basic oil dyes such as crystal violet, Victoria blue, malachite green, rhodamine B, auramine and their metal salts, or eosin B, erythrosine, rose bengal, and other azo dyes and anthraquinone dyes are used. Dyes can be mentioned. Since many dyes tend to inhibit photocuring of the photosensitive layer, it is necessary to select dyes that do not reduce adhesion and sensitivity.

In particular, pigments that do not absorb the absorption wavelength of the photopolymerization initiator are desirable; on the other hand, as pigments, carbon black,
Examples include phthalocyanine pigments, titanium oxide, dioxazine violet, and quinacridone pigments.

Furthermore, it is also possible to add a thermal polymerization inhibitor or a chain transfer agent if necessary. As the thermal polymerization inhibitor, hydroquinone, p-methoxyphenol, phenothiazine, etc. are used, and as the chain transfer agent, N-phenylglycine, mercaptobenzoxazole, mercaptobenzothiazole, etc. are used.

Furthermore, in order to prevent polymerization inhibition and blocking caused by oxygen on the surface of the photosensitive layer, it is preferable to provide a cover sheet or a water-soluble resin layer.The thickness of the water-soluble resin is 0.1
~50 μm, preferably 0.5 μm. Examples of water-soluble resins include polyvinyl alcohol and polyvinylpyrrolidone, and polyvinyl alcohol with high oxygen barrier properties is particularly preferred.

In order to produce a printing plate using the lithographic printing plate material of the present invention, first, the present lithographic printing plate material and a negative original are vacuum-adhered, and then active light such as ultraviolet rays capable of curing the photosensitive layer is applied. Exposure is performed using a light source that emits a large amount of light, such as a mercury lamp, an ultra-high pressure mercury lamp, or a metal halide lamp. Alternatively, projection exposure or scanning exposure is also possible. The exposed film is then immersed in an aqueous solution of an alkaline agent such as potassium hydroxide, sodium hydroxide or lithium hydroxide to develop the photosensitive layer.A water-soluble organic solvent or a water-soluble organic solvent or the like is added to this aqueous solution to accelerate development. Surfactants can also be added.

【Example] Hereinafter, the present invention will be explained in detail with reference to Examples.

(Example 1) A 500 ml four-bottle flask was equipped with a thermometer, a nitrogen inlet tube, a condenser tube, and a stirrer, and the following mixture was put therein.

While stirring, flush with nitrogen and keep at 80°C for 7 hours. The solution gradually thickens and a transparent polymer is obtained.

(This will be referred to as Copolymer 1.) The following photosensitive solution was applied on a grained 300 micron aluminum plate using a #20 wire bar, and then dried at 70°C for 30 minutes to form a photosensitive layer. did.

The dry coating thickness was 2.5 μm.

Next, 7% by weight of an aqueous solution of GLO5 (partially saponified polyvinyl alcohol manufactured by Nippon Gosei Kagaku Co., Ltd.) was added to 2.
A coating material with a thickness of 8 μm was applied and dried to prepare a planographic printing plate material.

The above image forming material, negative original and step tablet (No. 2, manufactured by Kodak) were vacuum-adhered, exposed for 3 seconds using a printer (manufactured by Oak, 3 kW ultra-high pressure mercury mounting), and then heated to 30°C using an iPI temperature. It was rubbed lightly with a sponge for about 2 minutes in an aqueous solution having the composition shown below.

The photosensitive layer in the exposed area was dissolved and removed, and a good positive image was obtained. The number of curing stages in the step tablet was six. Further, this image forming material was heated at 130° C. for 5 minutes to promote fogging, and then exposed and developed, but a similar image was obtained.

This printing plate was printed on a Ryobi offset printing machine AD-80.
When printed, good prints were obtained from the first page. Furthermore, the image quality deteriorates even after the 10,000th photo.
There was very little.

(Example 2) Copolymer 2 was produced in the same manner as in Example 1 at the following blending ratio.

On a grained aluminum plate of 300 microns, the following photosensitive solution was applied in the same manner as in Example 1 to a dry film thickness of 3 microns.
m was applied.

Further, a polyvinyl alcohol layer was provided in the same manner as in Example 1, and the image forming material was image-exposed in the same manner as in Example 1 to prepare a lithographic printing plate material.
After rubbing lightly with a sponge for 30 seconds in the following developer solution whose temperature was adjusted to 30°C, it was washed with water.

The unexposed areas of the photosensitive layer were dissolved, an image appeared, and a lithographic printing plate with a positive image was obtained, the number of curing steps was 8, the optical density was 3.0 or more, and the resolution was 100 lines/mm or more. When printing was carried out using this lithographic printing plate in the same manner as in Example 1, a good printed matter similar to that on the lithographic printing plate was obtained.

(Comparative Example 1) Copolymer 3 was synthesized in the same manner as in Example 1 at the following blending ratio.

A lithographic printing plate material was prepared using Copolymer 3 in the same manner as in Example 1, and immediately after the preparation, it was exposed and developed to form an image. As a result, a good image was obtained, however, the number of curing steps was 2. Further, when this image forming material was subjected to exposure and development after promoting fogging in the same manner as in Example 1, the non-exposed areas were not dissolved and no image was obtained.

(Comparative Example 2) Copolymer 4 was synthesized in the same manner as in Example 1 at the following blending ratio.

Styrene 50g Mono-n-butyl maleate 50g Methyl cellosolve
A lithographic printing plate material was prepared using 150 g of Copolymer 4 in the same manner as in Example 1, exposed and developed, but the photosensitive layer swelled in the latter half of development, and fine line reproduction was poor, resulting in poor images. I couldn't get it.

(Example 3) The copolymers shown in the following table were synthesized by the method of Example 1, a lithographic printing plate material was prepared under the same conditions as in Example 1, and the photosensitive layer was exposed and developed. Similar results were obtained.

The surface properties of the photosensitive layer are the state of the surface after applying the polyvinyl alcohol layer, and sample 4 had fine irregularities.

Developability indicates the removal of the photosensitive layer in non-exposed areas.

[Effects of the Invention] As explained above, according to the present invention, sensitivity is significantly improved, heat fog is less likely to occur, adhesion is improved, and film lifting during development is prevented. .

Furthermore, ink adhesion and rigidity resistance during printing are improved.

Patent applicant Toppan Printing Co., Ltd. Representative: Kazuo Suzuki

Claims (2)

[Claims] (1) A lithographic printing plate material consisting of a grained aluminum plate and developable with an alkaline aqueous solution, in which the photosensitive layer comprises: (a) methyl methacrylate, styrene, acrylonitrile, tert methacrylate; - at least one selected from butyl; (a) at least one selected from n-butyl acrylate, 2-ethylhexyl acrylate, and dodecyl methacrylate; and (c) at least one copolymerizable organic acid. , A copolymer having a copolymerization ratio of 40 to 80% by weight of component (A), 5 to 20% by weight of component (B), and 15 to 40% by weight of component (C) is 40 to 60% by weight.
A lithographic printing plate material comprising a photosensitive resin containing 10 to 60 weight percent of an ethylenically unsaturated compound and 1 to 20 weight percent of a photopolymerization initiator. (2) Copolymerizable organic acids include organic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, cinnamic acid, fumaric acid, and maleic acid, and monomethyl and monoethyl dibasic acids such as itaconic acid. The lithographic printing plate material according to claim 1, which is at least one monoester selected from the group consisting of monoesters.