JPH0151821B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photosensitive resin composition for printing plates, particularly to a photosensitive resin composition for flexographic printing plates that has excellent washout and developability with water or an aqueous solvent.

Flexo printing is used to print packaging materials such as film, cardboard, kraft paper, and cartons, and traditionally rubber plates have been used. Flexo printing plates using rubber plates are manufactured by hand engraving and casting methods, but the former requires advanced technology;
It is difficult to make a plate with high precision, and the latter requires many steps, which is disadvantageous in terms of equipment and economy. Moreover, it is necessary to select an ink solvent.

Photosensitive flexographic plates eliminate the drawbacks of these rubber plates, and photosensitive resin plates have begun to be used for rationalizing the plate-making process and saving labor. Photopolymer resins for flexographic plates must have physical properties similar to conventional rubber plates, namely flexibility and rubber-like elasticity. To achieve this, it is either made to have flexibility and elasticity similar to that of rubber, or it is necessary to add photocrosslinkable monomers, sensitizers, stabilizers, etc. to materials that have rubber properties, such as synthetic rubber. ing.

Various prepolymers having rubber physical properties have been devised in which various urethane rubbers, butyl rubbers, silicone rubbers, ethylene propylene rubbers, styrene-butadiene rubbers, etc. are incorporated as constituent elements. In addition, general synthetic materials such as polybutadiene, polyisoprene, isoprene-styrene copolymer, acrylonitrile-butadiene copolymer, polyurethane, and ethylene-vinyl acetate copolymer are produced by mixing a rubbery substance and a photocrosslinkable substance. Rubber-based materials include crosslinkable materials in which vinyl monomers such as acrylic esters are mixed with photopolymerization initiators such as benzophenone, benzoin, and anthraquinone.

However, with recent advances in printing technology,
Greater rebound resilience, tear strength, tensile strength, elongation, ink properties, etc. are now required, and it has become difficult for conventional photosensitive resin compositions to satisfy these demands. Moreover, the developer used to wash out the unexposed areas is perchlorethylene,
Solvents such as trichloroethane are used, and there are many problems in terms of toxicity and workability.

As a result of intensive research to improve these shortcomings, the present inventors have developed a photosensitive resin composition using a water-soluble polyester ether resin that has even higher performance and that can be washed out and developed with water or an aqueous solvent. The present inventors have discovered that a photosensitive resin composition for flexographic printing plates can be obtained that is capable of printing and has excellent printing durability, leading to the completion of the present invention.

That is, the present invention provides () a water-soluble polyester ether, () at least one photopolymerizable monomer or prepolymer having one or more vinyl groups, () a photopolymerization initiator, and a material that can be stably stored. This photosensitive resin composition for flexographic printing plates is composed of a thermal polymerization inhibitor (), and has excellent strength, rebound resilience, and elastic recovery, and can be washed out and developed with water or an aqueous solvent, and has excellent printing durability. It is something.

() Water-soluble polyester ether in the present invention includes (A) a polyether component of polyalkylene glycol with a molecular weight of 400 to 5,000, (B) a polyester component consisting of a polybasic acid and a polyhydric alcohol, and (C) an aromatic nucleus. It can be produced by a conventionally known transesterification method or direct polymerization method using a bifunctional monomer having a bonded -SO ₃ M group (where M is hydrogen or a metal ion).

In the above, (A) polyether component is:
Examples include polyalkylene glycols such as polyethylene glycol (molecular weight 400-5000), polypropylene glycol (molecular weight 400-5000), and ethylene glycol-propylene glycol block copolymer (molecular weight 400-5000). In addition, if necessary, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,6-hexanediol, 1,5-pentanediol, glycerin, It is also possible to partially use dihydric alcohols and polyhydric alcohols such as methylolpropane, trimethylolethane, and pentaerythritol in combination.

Further, as the polyester component (B), aromatic polybasic acids, aliphatic polybasic acids, derivatives thereof, and polyhydric alcohols can be used. In the above, examples of aromatic polybasic acids include phthalic acid, isophthalic acid, terephthalic acid, tetrahydroxyphthalic acid, hexahydroxyphthalic acid, trimellitic acid, diphenic acid, and 4,4'-oxybenzoic acid. Examples of aliphatic polybasic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, fumaric acid,
These include maleic acid and itaconic acid. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4
-butanediol, 1,3-butanediol,
1,6-hexanediol, 1,5-pentanediol, glycerin, trimethylolpropane,
Examples include trimethylolethane.

Furthermore, (C) a bifunctional monomer having a -SO ₃ M group (where M is hydrogen or a metal ion) bonded to an aromatic nucleus, together with the above-mentioned polyether group, imparts water solubility; They are useful for imparting excellent washout and developability with solvents, such as dimethyl sodium 5-sulfoisophthalate, sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and sulfosalicylic acid. As M, hydrogen or metal ions such as Na ⁺ , K ⁺ , and Li ⁺ are effective.

As a method for producing water-soluble polyester ether, the above-mentioned (A), (B) and
It can be obtained from component (C) by carrying out a transesterification reaction at a reaction temperature of 150 to 250°C under an inert gas flow, followed by a polycondensation reaction at a temperature of 200 to 300°C under atmospheric pressure or reduced pressure. .

In the present invention, photopolymerizable monomers or prepolymers include acrylic acid, methacrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, iso-propyl (meth)acrylate, n-propyl (meth)acrylate,
iso-butyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, ethylene glycol mono(meth)acrylate, diethylene glycol mono(meth)acrylate , propylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate with a molecular weight of 200 to 1000, polypropylene glycol mono(meth)acrylate with a molecular weight of 200 to 1000, cyclohexyl (meth)acrylate, N,N'-
Dimethylaminoethyl (meth)acrylate, acrylamide, diacetone acrylamide, styrene, sodium allylsulfonate, sodium methallylsulfonate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, pentaerythritol tri (meth)acrylate, acrylonitrile, etc.

In addition, as the photopolymerization initiator (), conventionally known benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin-n-butyl ether, benzyl, benzophenone, diacetyl, acetophenone, butyroin, eosin, thionine, 9,10-anthraquinone, Examples include 1,4-naphthoquinone, which may be used alone or in combination. The photopolymerization initiator can be added in an amount of 0.01 to 10% by weight based on the total amount of the components () and ().

Furthermore, () thermal polymerization inhibitors include hydroquinone, hydroquinone monomethyl ether, catechol, pt-butylcatechol, and the like. These thermal polymerization inhibitors are added to simply prevent thermal polymerization without inhibiting the photocrosslinking reaction, and are added in an amount of 0.005 to 1.0% by weight based on the total amount of components () and (). It can be added and used within the range of.

A plasticizer, softener, etc. can be added to the photosensitive resin composition for a flexographic printing plate according to the present invention within a range that does not significantly impair its physical properties. plasticizer,
Examples of softeners include dioctyl phthalate,
Examples include butylphthalyl butyl glycolate, polyester plasticizers, epoxy plasticizers, various phosphoric acid esters, and polyethers such as polypropylene glycol. Further, it is also possible to blend a compound having rebound resilience, such as polyamide, polyester, cellulose derivative, polybutadiene, polyurethane, etc., within a range that does not impair the object of the present invention.

The ultraviolet rays used when curing the photosensitive resin composition for flexographic printing plates according to the present invention are
A wavelength of 500 nm, particularly a wavelength range of 300 to 400 nm, is effective, and the light source used is preferably a low-pressure mercury lamp, a high-pressure mercury lamp, or a carbon arc lamp. In the photosensitive resin composition of the present invention, a negative film having a transparent image is irradiated with ultraviolet rays using the above light source to form a relief image, and then the unexposed non-image areas are covered with water or A relief image can be obtained by washing out with a mixture of aqueous solvents, such as methanol, ethanol, acetone, and other organic solvents.

The flexographic printing plate obtained using the photosensitive resin composition of the present invention has excellent ink resistance and ink transferability, as well as excellent printing durability.
Although the photosensitive resin composition according to the present invention is mainly intended for the production of flexographic printing plates, it can also be used as various elastomers that are cured by ultraviolet rays, such as adhesives, films, paints, etc. Needless to say, it can also be used for molded products.

Examples are shown below to explain the present invention in more detail. In addition, in the following, all "parts" shall mean "parts by weight."

Synthesis example 1 Polyethylene glycol (molecular weight 1000) 20 parts polypropylene glycol (molecular weight 1200)
20 Ethylene glycol 86 Isophthalic acid 116 Dimethyl sodium 5-sulfoisophthalate
10 Zinc acetate 0.1 While stirring the above mixture, under a nitrogen stream
The temperature was raised to 200°C, and the transesterification reaction was carried out for 4 hours.Then, the temperature was raised to 250°C, and the reaction was carried out in a vacuum of 10 mmHg for 2 hours, and then the mixture was cooled and taken out to obtain water-soluble polyester ether (X). Ta.

Example 1 20 parts of 2-hydroxyethyl methacrylate and 10 parts of methyl methacrylate as photopolymerizable monomers were mixed with 70 parts of the water-soluble polyester ether (X) obtained in Synthesis Example 1, and 3 parts of benzoin and 0.5 parts of hydroquinone were added. The resulting photosensitive resin composition was covered with a polyester film and poured onto a glass plate sandwiching a 5 mm thick rubber spacer, then a negative film was applied, ultraviolet rays were irradiated from the opposite side of the negative film, and then a negative film was applied. The film was irradiated from the side, and the unexposed areas were washed out with water.

The resulting flexographic printing plate has a hardness (Shore A) of
61, tensile strength of 133 Kg/cm ² and rebound resilience of 50%.

Synthesis example 2 Polyethylene glycol (molecular weight 2000) 30 parts ethylene glycol 90 Dimethyl terephthalate 87 Adipic acid 10 Dimethyl potassium 5-sulfoisophthalate
15 Trimethylolethane 0.5 Antimony acetate 0.1 part The above mixture was stirred and placed under a nitrogen stream.
The temperature was raised to 200°C, the transesterification reaction was carried out for 5 hours, and then the temperature was raised to 260°C, and the transesterification reaction was carried out for 1.5 hours under a vacuum of 5 mmHg.
After carrying out the polycondensation reaction for a period of time, the mixture was cooled and taken out to obtain water-soluble polyester ether (Y).

Example 2 To 60 parts of the water-soluble polyester ether (Y) obtained in Synthesis Example 2, 20 parts of 2-hydroxyethyl methacrylate and 5 parts of acrylamide were added as photopolymerizable monomers.
1 part, 5 parts of methacrylic acid, and 10 parts of styrene,
5 parts of benzophenone, 0.3 parts of hydroquinone dimethyl ether, and 2 parts of dioctyl phthalate as a plasticizer were added, and the resulting photosensitive resin composition was made into a flexographic printing plate in the same manner as in Example 1.

The resulting flexographic printing plate has a hardness (Shore A) of
57, tensile strength of 121 Kg/cm ² and rebound resilience of 47%.

Synthesis Example 3 Ethylene glycol-propylene glycol block copolymer (molecular weight 1400) 40 parts Diethylene glycol 76 Phthalic acid 80 Sodium 5-sulfosalicylate 20 Glycerin 0.3 Potassium titanium oxalate 0.2 The above mixture was stirred under a nitrogen stream.
The temperature was raised to 200°C and a transesterification reaction was carried out for 4 hours.Then, the temperature was raised to 250°C and a polycondensation reaction was carried out at normal pressure for 3 hours.The water-soluble polyester ether (Z) was then cooled and taken out. Obtained.

Example 3 70 parts of water-soluble polyester ether (Z) obtained in Synthesis Example 3 were mixed with 10 parts of 2-hydroxyethyl methacrylate, 10 parts of methyl methacrylate, 5 parts of acrylic acid, and 5 parts of glycidyl methacrylate as photopolymerizable monomers, 5 parts of benzophenone, 0.5 parts of hydroquinone, and 2 parts of dioctyl phthalate were added, and the resulting photosensitive resin composition was exposed in the same manner as in Example 1 to create a flexographic printing plate,
It was washed out with a mixture of 70 parts of water and 30 parts of methyl alcohol.

The resulting flexographic printing plate has a hardness (Shore A) of
65, tensile strength of 145 Kg/cm ² and rebound resilience of 45%.

Claims (1)

[Claims] 1 Consists of () water-soluble polyester ether, () at least one photopolymerizable monomer or prepolymer having one or more vinyl groups, () a photopolymerization initiator, and () a thermal polymerization inhibitor; () Water-soluble polyester ether has (A) molecular weight
400 to 5000 polyether component of polyalkylene glycol, (B) polyester component consisting of polybasic acid and polyhydric alcohol, and (C) -SO ₃ M group bonded to aromatic nucleus (where M is hydrogen or metal ion) ) A photosensitive resin composition for a flexographic printing plate, which is obtained by polycondensing a difunctional monomer having the following.