JPH04122941A - Photosensitive resin composition - Google Patents

Abstract

PURPOSE:To allow the application to a flexographic printing plate which can be developed with water by synthesizing a water-soluble satd. polyester having an alkaline metal salt type sulfonic acid group, an elastomer, a photopolymerizable unsatd. compd., and a photopolymn. initiator. CONSTITUTION:The water-soluble satd. polyester having the alkaline metal salt type sulfonic acid group is produced by copolymerizing an acid component monomer and alcohol component monomer used as the raw material monomers for ordinary satd. polyesters and a monomer having the alkaline metal salt type sulfonic acid group and >=2 pieces of ester formable functional groups. Polyvalent carboxylic acid, having >=2 pieces of carboxyl groups, for example, terephthalic acid, is used as this acid component monomer and the monomer having the alkaline metal salt type sulfonic acid group is incorporated at 5 to 20mol% in the polyester to be used. The compsn. is produced by compounding butadiene rubber, etc., as the elastomer, for example, acrylic resin, etc., as the photopolymerizable unsatd. compd., and, for example, benzophenones, etc., as the photopolymn. initiator with the compsn. The compsn. which can be developed with water, has the excellent ink resistance and can be developed with living water is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photosensitive resin composition, and more specifically, a photosensitive resin composition suitable for use in a flexible flexographic printing plate that can be developed with an aqueous solution. Regarding.

[Prior Art] Photosensitive resin compositions whose basic composition consists of a binder, a photopolymerizable unsaturated compound, and a photoinitiator are used in many fields as suitable materials for forming relief images, and are used in flexographic printing. The edition is also available as one of them.

By the way, conventional photosensitive resin compositions for flexographic printing plates are disclosed in, for example, U.S. Pat.
specification, Japanese Patent Publication No. 51-43374, Japanese Patent Publication No. 59
As described in Publication No.-22219 etc., t=S
The binder is an elastomer such as rubber, styrene-butadiene bronc copolymer, or polyurethane, to which a photopolymerizable unsaturated compound and a photopolymerization initiator are added. However, due to the large amount of binder used in such compositions, halogenated hydrocarbons are required in the developer solution to form the image.

Therefore, there are problems such as health problems and environmental pollution. On the other hand, various photosensitive resin compositions that use a developer that does not require a halogenated hydrocarbon are known for purposes other than those for flexo printing plates. For example, Japanese Patent Publication No. 46-26125, Japanese Patent Publication No. 50-32645, Japanese Patent Publication No. 54-3
As described in Japanese Patent Publication No. 790, Japanese Patent Publication No. 57-28485, etc., polyvinyl alcohol or polyamide soluble in water or alcohol is used as a binder, but printing plates obtained by photocuring is hard and unsuitable for flexo printing. Also, JP-A-52-134
As described in JP-A No. 655, JP-A-53-10648, JP-A-61-22339, JP-A-1-219735, JP-A-1-306836, etc., conjugated diene carbonization An aqueous developer containing hydrogen and a,β-ethylenically unsaturated carboxylic acid or its salt as essential components, a copolymerizable unsaturated monomer containing a monoolefinically unsaturated compound, and a photosensitizer. There are photosensitive resin compositions that can be developed with. However, printing plates obtained from such compositions are difficult to develop using household water with a pH of 5.0 to 9.0, have insufficient ink resistance in relief areas, and have poor ozone resistance and weather resistance. However, it has the problem that its properties and oxidation resistance are insufficient.

In addition, JP-A-52-260142 discloses that (a) a water-soluble saturated polyester having an alkali metal salt type sulfonic acid group, (b) a photopolymerizable unsaturated compound, and (c) a photopolymerization initiator are essential. A photosensitive resin composition characterized by containing g as a component has been disclosed, but although the printing plate obtained with this composition has resistance to oil-based inks,
It has the disadvantage of not being resistant to inks containing polar solvents such as aqueous or alcoholic solvents, and is therefore impractical.

Problems to be Solved by the Invention] Since the present invention can be applied to water-developable flexographic printing plates, it overcomes the drawbacks of conventional photosensitive resin compositions as described above, and can be developed with household water. The purpose of this invention is to provide a photosensitive resin composition suitable for a flexographic printing plate that has satisfactory ink resistance.

Means for Solving Problems U] The present inventors have conducted intensive research to develop a photosensitive resin composition that is water-developable, has high ink resistance, and can be developed with household water. It has been discovered that a photosensitive resin composition using a water-soluble saturated polyester having an alkali metal salt type sulfonic acid group as a binder achieves the objective, and based on this knowledge, the present invention has been completed.

That is, the present invention provides a photosensitive resin comprising (a) a water-soluble saturated polyester having an alkali metal salt type sulfonic acid group, (b) an elastomer, (c) a photopolymerizable unsaturated compound, and (d) a photopolymerization initiator. A composition is provided.

The present invention will be explained in detail below.

(a) The water-soluble saturated polyester having an alkali metal salt type sulfonic acid group used in the composition of the present invention is composed of acid component monomers and alcohol component monomers that are used as raw material monomers for ordinary saturated polyesters. and a monomer having an alkali metal salt type sulfonic acid group and two or more ester-forming functional groups.

The acid component monomers include polycarboxylic acids having two or more carboxyl groups, such as aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid, trimellitic acid, and pyromellitic acid. Examples include aromatic polycarboxylic acids, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and aliphatic dicarboxylic acids such as dodecanedicarboxylic acid.

Further, as monomers of the alcohol component, polyhydric alcohols having two or more hydroxyl groups, such as ethylene glycol, propylene glycol, 1.3=propanediol,
1,4-butanediol, 1,5bentanediol, 1
．． Glycols such as 6-hexanediol and 1,4-cyclohexane dimetatool, polyethylene glycols and polypropylene glycols such as diethylene glycol and triethylene glycol, trimethylolpropane, and pentaerythritol are used.

Further, the monomer of the polyester may include a hydroxycarboxylic acid component, such as p-hydroxybenzoic acid, salicylic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxycarboxylic acid component, as desired.
Aromatic hydroxycarboxylic acids such as hydroxy-3-naphthoic acid, and aliphatic cyclic esters such as γ-butyrolactone and ε-caprolactone can also be used.

As the monomer having an alkali metal salt type sulfonic acid group and two or more ester-forming functional groups, an alkali metal salt is added to the acid component monomer, alcohol component monomer or hydroxycarboxylic acid component monomer. An aromatic dicarboxylic acid into which an alkali metal salt-type sulfonic acid group has been introduced is preferably used from the viewpoint of ease of availability and physical properties of the resulting polyester.

Examples of these include 2-sodium or potassium sulfoterephthalate, 5-sodium or potassium sulfoisophthalate, and the like.

This monomer having an alkali metal salt type sulfonic acid group is
Polyester used 95-20 mol%, preferably 8
It is desirable to use it so that it is contained in a proportion of ~13 mol%. Polyester containing less than 5 mol% has poor stability when made into an aqueous solution or water-soluble. On the other hand, 20 mol%
If it exceeds 20%, the melt viscosity of the Bossester becomes extremely high, making it difficult to obtain a polyester with sufficient cohesive strength during polymerization.

In the water-soluble saturated polyester used in the present invention,
As the acid component and optionally used hydroxycarboxylic acid, aromatic components such as aromatic dicarboxylic acids and aromatic hydroxycarboxylic acids are 10 to 85 mol%, and aliphatic components such as aliphatic dicarboxylic acids and aliphatic hydroxycarboxylic acids are used. It is preferable to use the components in a proportion of 90 to 15 mol%. Further, as aromatic dicarboxylic acid components, those composed of terephthalic acid and isophthalic acid with a molar ratio in the range of 8:2 to 5:5, and as aliphatic dicarboxylic acid components and aliphatic hydroxycarboxylic acid components. is preferably adipic acid, azelaic acid, sebacic acid, C-caprolactone, etc., each having 2 to IO methylene groups.

If the aromatic component is less than 10 mol%, the flexibility of the polyester becomes too large, and the resulting printing plate tends to lose its shape; on the other hand, if it exceeds 85 mol%, the flexibility of the polyester is too small and the resulting printing plate is too thin. This is not preferred because it tends to reduce the flexibility of the printing plate. Furthermore, when an aliphatic dicarboxylic acid component or an aliphatic hydroxycarboxylic acid component having more than 10 methylene groups is used,
The resulting polyester is undesirable because it lacks water solubility and stability when made into an aqueous solution.

On the other hand, alcohol components include ethylene glycol,
Glycols having 2 to 8 carbon atoms and not having an ether group, such as 1,3-propanediol and 1,4-butanediol, are preferred. Glycols having 9 or more carbon atoms and not having an ether group are not preferred because they lack the water solubility of polyester and the stability when made into an aqueous solution. Polyethylene glycols and polypropylene glycols such as diethylene glycol and triethylene glycol can also be advantageously used, but in this case, those with a molecular weight of 500 or less are preferred, and these are 40% by weight or less based on the polyester produced, especially in the case of diethylene glycol. It is preferably used in a range of 35% by weight or less, and in the case of polyethylene glycol with a molecular weight of 500, 20% by weight or less. If the amount used exceeds 40% by weight or if the molecular weight is greater than 500, the resulting printing plate tends to lose its shape, which is not preferred.

The water-soluble saturated polyester used in the present invention may contain other copolymer components other than those described above, as long as the purpose of the present invention is not impaired. There are no particular restrictions on the method for producing this product, and any method commonly used for producing polyester can be used. For example, dimethyl ester of a dicarboxylic acid and a glycol are heated in the presence of a catalyst to undergo a transesterification reaction, and then the glycol is distilled off while heating and depressurizing in the presence of a catalyst to perform condensation polymerization. It can be produced by heating under pressure to carry out an esterification reaction, and then in the presence of a catalyst, glycol is distilled off while heating under reduced pressure to perform condensation polymerization. At this time, it is preferable to add a coloring inhibitor, a heat stabilizer, etc., and to select polymerization conditions that are as low temperature and short as possible.

The water-soluble saturated ester used in the present invention has an intrinsic viscosity of 0.28 to 0.6 when measured at a temperature of 20°C in a mixed solvent of phenol/tetrachloroethane (weight ratio: 1).
Those in the range of 5 are preferred.

If the intrinsic viscosity is less than 0.28, the cohesive force of the polyester will be insufficient, while if it exceeds 0.65, the elution rate during printing plate preparation will be low, which is not preferred.

The elastomer that is the component (b) of the present invention has rubber elasticity at around room temperature, has high elongation, has high durability under repeated loads, and has good abrasion resistance and electrical insulation properties. However, any material can be used as long as it has good compatibility with component (a) described above. Suitable examples of such materials include butadiene rubber, styrene/butadiene/styrene block copolymer, styrene/isoprene/styrene block copolymer, ethylene/vinyl acetate copolymer, polyurethane, and the like. The preferred blending ratio of component (b) is 5 to 200 parts by weight, preferably 10 to 150 parts by weight, per 100 parts by weight of component (a). When the amount is less than 5 parts by weight, not only the compatibility with water-based ink after photocuring becomes poor, but also flexibility and elasticity cannot be obtained. 200 again
If the amount exceeds 1 part by weight, development with an aqueous developer becomes impossible, which is not preferable.

Examples of the photopolymerizable unsaturated compound which is component (iii) of the present invention include acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, glycidyl acrylate, glycidyl methacrylate, benzyl acrylate,
Triphromophenyl acrylate, cyclohexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, acrylamide, methacrylamide, N-methylol acrylamide, N-ethylol acrylamide, N-propylol acrylamide, N-methylol Methacrylamide, N-methylolmethacrylamide, N-provirolmethacrylamide, n-butoxymethylacrylamide, 180-butoxymethylacrylamide, N-terj-butylacrylamide, sodium acrylate, ammonium acrylate, acrylonitrile, styrene, Photopolymerizable unsaturated compounds having one unsaturated double bond such as sodium styrene sulfonate, vinylpyridine, allyl methacrylate, ethylene glycol diacrylate,
Ethylene glycol dimethacrylate, 1.3-propanediol diacrylate, 1.4-butanediol diacrylate, 1.3-propanediol methacrylate, 1.4-butanediol dimethacrylate, 1,6
-hexanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, triacryloyloxyethyl phosphate, methylenebisacrylamide, ethylenebisacrylamide, propylenebisacrylamide, hexamethylenebisacrylamide, Examples include photopolymerizable unsaturated compounds having two or more unsaturated double bonds, such as methylene bis methacrylamide, ethylene bis methacrylamide, and propylene bis methacrylamide. These photopolymerizable unsaturated compounds may be used alone or in combination of two or more. The blending ratio of this component (c) is (
The amount is 5 to 200 parts by weight, preferably 10 to 150 parts by weight, based on 100 parts by weight of component a).

If it is less than 5 parts by weight, the photocrosslinking density of the ultraviolet irradiated area will be low, the irradiation time will be long, and the mechanical strength will be insufficient. 20 again
If it exceeds 0 parts by weight, the shape retention of the image will deteriorate,
After irradiation, the plate becomes hard and brittle, making it unsuitable as a flexographic printing plate material.

Examples of the photopolymerization initiator (component (2)) used in the composition of the present invention include benzophenones, benzoins, acetophenones, benzyls, benzoin alkyl ethers, benzyl alkyl ketals, anthraquinones,
Thioxanthones can be mentioned, and specific examples thereof include benzophenone, chlorobenzophenone, benzoin, acetophenone, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, penzoin isobutyl ether, benzyl methyl ketal, and benzyl. Ethyl ketal, benzyl diisopropyl ketal, anthraquinone,
Examples include 2-chloroanthraquinone, thioxanthone, and 2-chlorothioxanthone. The blending ratio of this (d) component is 1 in total of component (a), component (b), and component (c).
0.01 to 5 parts by weight, preferably 0.00 parts by weight
．． It is 1 to 3 parts by weight.

The composition of the present invention may optionally contain thermal polymerization inhibitors, such as hydroquinone derivatives such as hydroquinone, methylhydroquinone, and hydroquinone monomethyl ether, phenol derivatives such as 2,6-tert-butyl-p-cresol, and p-benzoquinone. In addition, quinone derivatives such as nitrobenzene and its derivatives can be added. The amount of these thermal polymerization inhibitors to be used is 0,001 to 2 parts by weight, preferably 0.05 to 0.5 parts by weight, based on the total of 100 parts by weight of components 2 (a), (b), and (c). selected within the range.

In addition to the above, the photosensitive mochi fat composition of the present invention includes liquid polybutadiene rubber, liquid polyacrylonitrile butadiene rubber, liquid polystyrene butadiene rubber as a plasticizer,
It can contain liquid rubber such as liquid isoprene rubber, relatively low molecular weight elastomers such as polyvinyl chloride, chlorinated polyethylene, and chlorinated polypropylene, and fine powders such as trimethylolpropane silica and diatomaceous earth.

Next, to give an example of a preferred method of using the composition of the present invention, first, component (a), component (b), and (c) Fl;
d) Dissolving the components and additives added as necessary in a suitable solvent such as tetrahydrofuran, dioxane, chloroform, methyl ethyl ketone, toluene, cyclohexane, etc., applying the solution onto the substrate, and drying and removing the solvent. A photosensitive resin film can be formed by.

As another method, components (a) and (b) may be dissolved under heating, and then components (c) and (d) may be dissolved therein and applied onto the substrate. In this case, the base material is a metal plate made of steel, stainless steel, aluminum, copper, etc., a plastic sheet made of polyester, etc.
Synthetic rubber sheets or the like are used, and an adhesive layer may be provided on the surface of these substrates in advance.

The thickness of the photosensitive resin film obtained in this way is 0.1
-10 mm is preferable as a printing plate. Next, place the required original mask on the photosensitive resin film,
The photosensitive resin coating is irradiated with ultraviolet light from a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, a chemical lamp, a carbon arc lamp, etc., which has an emission intensity of ultraviolet light of 300 to 450 μm, through an original mask,
The irradiated areas are photopolymerized and insolubilized in a developer, and the non-irradiated areas are dissolved and removed by the developer to form an image faithful to the original mask, thereby producing a printing plate material.

[Example] Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these Examples.

Reference Example 1 Production of water-soluble saturated polyester Terephthalic acid ethylene glycol ester 0.30 mol, isophthalic acid 0.25 mol, sebacic acid 0233 mol, 5-sodium sulfoisophthalic acid ethylene glycol ester 0
．． 12 mol ethylene glycol 0.76 mol, antimony trioxide 60 mg and sodium acetate trihydrate 200 mol
mg was placed in a polymerization test tube and heated to 160 to 220°C while stirring under a nitrogen atmosphere to perform an esterification reaction. Almost all of the water was distilled off in about 2 hours, and the reaction was continued for another 1 hour. Next, the temperature was raised to 270°C, and the pressure inside the reaction system was gradually reduced to 13 pa or less in about 1 hour, and then the pressure was reduced to 13 pa or less for about 1 hour.
A time condensation polymerization reaction was performed.

The obtained polyester was colorless and transparent, had elasticity, and had an intrinsic viscosity of 0.50.

Example 1 100 parts by weight of water-soluble saturated polyester obtained in Reference Example 1 Styrene-isoprene block copolymer (shell (
100 Trimethylolpropane triacrylate 20 Hexanediol diacrylate 10 Benzyl dimethyl ketal (lR651, manufactured by Ciba Geigy Co., Ltd.) 2 parts by weight 2.6-sheet tert-butyl-p-cresol 0.
05 Toluene 200
A photosensitive resin composition was prepared by uniformly dissolving the mixture having the above composition in a flask while heating to 60° C. and stirring. The composition thus obtained was cast onto a 125 μm polyethylene terephthalate film provided with an antihalation layer to a constant film thickness, and dried at 50°C for 20 hours to form a 1 mm thick film. A photosensitive layer was obtained. A test negative mask was vacuum-adhered onto this photosensitive layer, and a chemical lamp (Co., Ltd.) was applied from a distance of 2 to 4 cm.
Toshiba's PL L20B L type) was used to irradiate for 10 minutes, and then the non-irradiated area was washed out with warm water at 45°C for 6 minutes using a brush washing machine at 0°C, and then dried at 60°C for 20 minutes.
The entire surface was irradiated with ultraviolet rays for 5 minutes using the chemical lamp.

As a result, the test negative mask was 85! /inch.

The 3% halftone highlight area was reproduced. Further, the hardness of the relief was 60° Shore A, and a flexible and elastic flexographic printing plate material was obtained.

When this plate material was run on a printing machine and printed, printed matter with good ink coverage and excellent reproducibility was obtained.

Example 2 100 parts by weight of water-soluble saturated polyester obtained in Reference Example 1 Styrene-butadiene block copolymer (shell (
Kaliflex TR1102) 120 trimethylolpropane triacrylate 30 Liquid rubber (Poly bd R45HT manufactured by Idemitsu Petrochemical Co., Ltd.)
) 50 benzyl dimethyl ketal (lR651 manufactured by Ciba Geigy)
22.6-tert-butyl-p-cresol
1 was kneaded at 180°C using a heating kneader,
After defoaming, a photosensitive resin composition was obtained. This was then coated with adhesive using a heat press machine at 150°C and a pressure of 100 Kg/cm2 to create an adhesive between the 125 μm thick polyethylene terephthalate film and the 2 μm thick polyethylene terephthalate film provided with the polyvinyl alcohol coating. The photosensitive resin composition was heated and pressed for 1 minute so that the polyvinyl alcohol was on the photosensitive resin composition side to prepare a photosensitive layer laminate sheet having a thickness of 2° and 97 mm. Next, the entire surface of the polyethylene terephthalate film coated with the adhesive was irradiated with a chemical lamp for 4 minutes, and then the polyethylene terephthalate film coated with polyvinyl alcohol was peeled off, leaving the polyvinyl alcohol on the photosensitive layer. A test negative mask was placed in close contact with the mask under reduced pressure and irradiated with a chemical lamp for 15 minutes. After removing the negative mask, development was carried out using a brush in water at 30°C for 15 minutes, and the film was dried at 60°C for 30 minutes. As a result, an image pattern with a depth of 1.8 mm was obtained.

This image pattern faithfully reproduced the negative mask.

The hardness was Shore A 50°. When this was applied to a flexo printing machine, it had good ink receptivity and good printed matter was obtained.

Reference Examples 2 to 5 Water-soluble polyesters were synthesized in the same manner as in Reference Example 1. Its composition is shown in Table 1.

Table 1 Examples 3 to 5 Flexible printing plates were prepared in the same manner as in Example 1 using the water-soluble saturated polyesters of Reference Examples 2 to 5, and their performance was investigated.

The results are shown in Table 2.

Table 2 [Effects of the Invention] The photosensitive resin composition of the present invention is solid at room temperature, and has the property of becoming liquid when heated, so it can achieve uniform photosensitivity without using a solvent if necessary. A resin coating can also be formed. It can also be developed with an aqueous solution and is resistant to various inks. Furthermore, it has excellent flexibility and elasticity, and the image is extremely clear, so it can be used as a high-quality printing plate.

Claims (1)

[Claims] (1) A photosensitive resin composition comprising (a) a water-soluble saturated polyester having an alkali metal salt type sulfonic acid group, (b) an elastomer, (c) a photopolymerizable unsaturated compound, and (d) a photopolymerization initiator.