JPH0360113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming method, and more particularly to an image forming method that can be developed with an aqueous developer.

Conventionally, image formation involves forming a photosensitive resin layer on a support such as an aluminum plate, exposing it to a light image, and then dissolving and removing the unexposed areas with an organic solvent such as perchlorethylene or trichlorethylene to form a printing plate. Although many methods are known, the use of such solvents poses health problems for workers, and the disposal of the waste liquid is also expensive. Therefore, there is a strong demand in the industry for an image forming method that can be developed without using such organic solvents.

The present invention has met the above-mentioned needs, and despite using a hydrophobic photosensitive resin composition for image formation, it forms a photosensitive layer and can be easily developed with water or an aqueous medium after exposure. An image forming method is provided.

That is, the present invention provides a photosensitive resin composition comprising a photopolymerizable resin, an elastomer, and a water-swellable resin containing a hydrophobic oligomer having a molecular weight of 1000 or more and having an α,β-ethylenically unsaturated carbonyl group on a substrate. This image forming method is characterized in that a photosensitive layer is formed, and after exposure to a light image, unexposed areas are removed using an aqueous medium.

To explain the present invention in more detail, the photopolymerizable resin used in the present invention is a photopolymerizable oligomer that has a certain degree of film-forming ability even before photopolymerization, and such photopolymerizable oligomers are conventionally known. For example, oligomers made by reacting α, β-ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, or their functional derivatives with polyether polyols and polyester polyols. ,
Among oligomers etc. obtained by reacting with polyisocyanate compounds, polyols, polyhydric carboxylic acids, etc. using the hydroxyl groups of carboxylic acid esters having terminal hydroxyl groups obtained by reacting the above carboxylic acids or functional derivatives thereof with polyols, The overall molecular weight is about 1000 or more, most preferably about
5000 to 20000 is appropriate.

Such photopolymerizable oligomers can be used alone or in mixtures with other monofunctional monomers, polyfunctional monomers, and relatively low molecular weight oligomers. Furthermore, an appropriate amount of a thermoplastic resin, thermoplastic elastomer, or the like that is compatible with the above-mentioned photopolymerizable component may be included as a non-reactive resin. Furthermore, plasticizers, waxes, dyes and pigments can also be included as necessary.

Further, when the above composition is photopolymerized by ultraviolet rays, it is necessary to include a conventionally known photopolymerization initiator.

In addition, the above composition has excellent uses, especially as a photosensitive resin for printing plates, and when used for these purposes, thermoplastic elastomer, synthetic rubber, natural rubber, modified rubber, etc. may be added to the composition. Preferably, an elastomeric material is included.

Such elastomeric materials are particularly useful in the manufacture of flexographic printing plates when used in proportions of about 10 to 50% by weight of the total composition.

Particularly preferred as such elastomer materials are thermoplastic elastomers represented by polystyrene-polybutadiene-polystyrene block copolymers, polystyrene-polyisoprene-polystyrene block copolymers, and the like.

The film-forming components in the composition used in the present invention are as described above, and in the present invention, the photopolymerizable resin in the composition is about 5 to 80% of the film-forming components.
% by weight, and the molecular weight is approximately
Preferably, the oligomer having a molecular weight of 1000 or more accounts for about 10 to 50% by weight in the photopolymerizable resin.

Polymers having hydrophilic groups are useful as water-swellable materials that are used in the present invention and mainly characterize the present invention, examples of which include starch-sodium polyacrylate grafts, starch-sodium polyacrylate grafts, saponified product of acrylonitrile grafted product, cellulose-polyacrylic acid grafted product,
There are many examples including vinyl alcohol-sodium acrylate copolymer, vinyl alcohol-sodium methacrylate copolymer, partially cross-linked sodium polyacrylate, sodium salt of carboxymethylcellulose, partially cross-linked polyethylene oxide, etc. Preferred are polymers in which hydrophobic polymer chains or copolymer chains are bonded to polymers or copolymers having hydrophilic groups in the form of block copolymers or graft copolymers.

For the purposes of the present invention, particularly suitable water-swellable hydrophilic polymers have a bonding format of (hydrophobic segment)-(hydrophilic segment)-(hydrophobic segment), and are typical For example, as shown in the Examples below, thioglycolic acid, maleic anhydride, acrylic acid, methacrylic acid, etc. are added to the double bonds of a block copolymer of (polystyrene)-(polybutadiene)-(polystyrene). These include those obtained by addition polymerization and then neutralization with an alkali, or those obtained by block polymerizing polyethylene glycol with a molecular weight of about 1,000 to 20,000 as a hydrophilic segment with other hydrophobic polymers.

Such water-swellable materials are used in the composition used in the present invention in an amount of about 5 to 75% by weight, and especially when used as a plate-making material, they are used in an amount of about 10 to 50% by weight. It is preferable to do so. Furthermore, when such water-swellable materials have low compatibility with the above-mentioned film-forming components, it is preferable to blend them in the form of fine powder.

A photosensitive composition comprising the above-mentioned components can be obtained by simply mixing them together with an appropriate organic solvent, if necessary.

The resin composition used in the present invention has various uses, but a particularly suitable use is for forming photosensitive resin layers for printing plates, especially flexo printing plates.

That is, the above resin composition is used to coat a substrate such as an aluminum plate to a thickness of approximately
When a resin layer of 0.5 to 5 mm is formed and then exposed to a light image by a conventional method, the exposed areas polymerize and harden, while the unexposed areas remain uncured and form a latent image. In the case of a composition, the latent image can be easily developed with water or an aqueous solvent.

That is, when the latent image is brought into contact with water, for example, only the unexposed areas absorb water and swell, and are easily peeled off by a simple scratch. Furthermore, since the peeled pieces do not dissolve in the developing water and remain in a separate state, they can be easily recovered. The use of the composition thus eliminates the need for the development of harmful organic solvents that require post-treatment, as in the prior art.

Next, the present invention will be specifically explained with reference to Examples. Note that "%" or "%" in the text is based on weight.

Example 1 20 parts of pentaerythritol triacrylate,
1,2-polybutadiene glycol (average molecular weight
3000) and 87 parts of tolylene diisocyanate (average molecular weight
13000) 130 parts, 500 parts of a 20% methyl ethyl ketone solution of (polystyrene)-(polybutadiene)-(polystyrene) block copolymer (polystyrene content 40%), 80 parts of water-swellable material (A) described below, 40 parts of trimethylolpropane triacrylate 1 part, 2 parts of benzoin methyl ether, and 0.05 part of hydroquinone were uniformly mixed to obtain a photosensitive resin composition for image formation.

The composition was cast onto a polyester cover film and dried at 50°C for 10 hours to obtain a laminated sheet with a photosensitive resin layer having a thickness of 1 mm. After pressing the sheet onto an aluminum plate for plate making, the polyester film was peeled off, a negative film was attached, and a 2KW
The sample was exposed for 10 minutes using a high-pressure mercury lamp.

Next, when the surface was brushed with a brush while spraying water, the unexposed areas were peeled off very easily and development was possible.

The flexographic convex plate obtained by re-exposure after development had a Shore hardness of A50 and was ideal for high-speed printing of stamped balls.

Examples 2 to 9 A photosensitive resin composition for image formation having the composition shown in Table 1 below was obtained in the same manner as in Example 1, and a flexographic convex plate was produced in the same manner as in Example 1, and the same effect was obtained. .

Table 1 Example 2 Oligomer (A) 80 parts 20% methyl ethyl ketone (MEK) solution of the same block copolymer as Example 1 500 parts Diethylene glycol diacrylate 20 parts Trimethylolpropane triacrylate
30 parts Water-swellable material (B) 150 parts Benzoin dimethyl ketal 2 parts Hydroquinone 0.1 part Example 3 Oligomer (B) 90 parts Polystyrene)-(polyisobrene)-(polystyrene) block copolymer (pst.30%)
30% MEK solution 400 parts Triethylene glycol dimethacrylate 30 parts Dipentaerythritol hexaacrylate
20 parts Water-swellable material (C) 60 parts 2-ethylthioxanthone 5 parts Benzoquinone 0.5 part Example 4 Oligomer (C) 100 parts 20% of the same block copolymer as Example 1
MEK solution 500 parts Pentaerythritol tetramethacrylate
40 parts Water-swellable material (D) 125 parts Water-swellable material (F) 10 parts Benzoin ethyl ether 3 parts p-methoxyphenol 0.5 parts Example 5 Oligomer (D) 120 parts Poly-1,4-butylene adipate 4,4'-
500 parts of a 20% tetrahydrofuran solution of an elastomer consisting of diphenylmethane diisocyanate and trimethylolpropane triacrylate
50 parts Water-swellable material (F) 50 parts Benzophenone 5 parts Catechol 0.1 part Example 6 Oligomer (C) 100 parts Ethylene-vinyl acetate copolymer (EVA 48
%) 30% toluene solution 300 parts tetraethylene glycol dimethacrylate
30 parts trimethylolpropane triacrylate
30 parts Water-swellable material (C) 60 parts Benzoin methyl ether 3 parts Hydroquinone 0.1 part Example 7 Oligomer (E) 120 parts 20% toluene solution of poly-1,2-butadiene
500 parts trimethylolpropane triacrylate
40 parts Water-swellable material (D) 100 parts Water-swellable material (G) 10 parts Benzoin dimethyl ketal 3 parts p-methoxyphenol 0.5 parts Example 8 Oligomer (A) 120 parts 20% of the same block copolymer as Example 1
MEK solution 500 parts trimethylolpropane triacrylate
40 parts Water-swellable material (H) 120 parts Benzoin dimethyl ketal 3 parts Hydroquinone 0.1 part Example 9 Oligomer (D) 100 parts 20% of the same block copolymer as Example 3
MEK solution 500 parts Dipentaerythritol hexamethacrylate 50 parts Water-swellable material (E) 120 parts Benzoin methyl ether 3 parts Catechol 0.1 part The oligomers and water-swellable materials in the above table are as follows.

Oligomer A: Oligomer (mwt 10,000) obtained by reacting pentaerythritol methacrylate, 1,4-polybutadiene glycol (mwt 1,000), and trimethylhexamethylene diisocyanate at an equivalent ratio of 2:3:10. Oligomer B: Same as Example 1. Oligomer C: Oligomer (mwt 14,000) obtained by reacting pentaerythritol triacrylate, 1,2-polybutadiene glycol (mwt 3,000), polyε-caprolactone (mwt 2,000) and isophorone diisocyanate in an equivalent ratio of 2:4:6:12. D: Oligomer (mwt 9000) obtained by reacting trimethylolpropane diacrylate, polyoxypropylene glycol (mwt 2000) and tolylene diisocyanate at an equivalent ratio of 2:8:10 Oligomer E: Pentaerythritol triacrylate, polybutylene adipate glycol (mwt2000) and an oligomer obtained by reacting 4,4'-diphenylmethane diisocyanate in an equivalent ratio of 2:8:10 (mwt10000) Water-swellable material A: (polystyrene)-(polybutadiene)-(polystyrene) block A white fine powder made by adding thioglycolic acid to almost all the double bonds of a copolymer (pst 30%) to make a sodium salt (water swelling degree approximately 150 times) Water-swellable material B: (polystyrene) - (polybutadiene) - ( Water-swellable material C: (Polystyrene)-( White fine powder of sodium salt of the saponified product of the reaction product of polyisoprene)-(polystyrene) block copolymer and maleic anhydride (water swelling degree approximately 300 times) Water-swellable material D: Sodium salt of water-swellable material A is a triethanolamine salt (water swelling degree approximately 40 times) Water-swellable material E: reaction product of polyethylene oxide and tolylene diisocyanate and 1,4
- Reaction product with polybutadiene glycol (water swelling degree approximately 20 times) Water-swellable material F: Copolymer consisting of acrylic acid, sodium acrylate and methylenebisacrylamide (water swelling degree approximately 400 times) Water-swellable material G: Ethylene Oxide-propylene oxide random copolymer, 2,2'-diphenylmethane diisocyanate, styrene-butadiene copolymer with hydroxyl groups at both ends Sequential reaction product (water swelling degree approximately 12 times) Water-swellable material H: (Polystyrene) - (Polybutadiene) - (Polystyrene) block copolymer (PST 400%) with thioglycolic acid added to almost all the double bonds to create a potassium salt (white fine powder (water swelling rate approximately 80 times)).

Claims (1)

[Claims] 1. A photosensitive layer is formed on a substrate from a photosensitive resin composition consisting of a photopolymerizable resin containing a hydrophobic oligomer with a molecular weight of 1000 or more having α, β-ethylenically unsaturated carbonyl groups, an elastomer, and a water-swellable resin. . An image forming method, which comprises removing unexposed areas with an aqueous medium after exposure to a light image.