JPH0532743A - Photosensitive micro-gel, photosensitive resin composition for flexographic printing plate and original plate for flexographic printing plate - Google Patents

Abstract

PURPOSE:To obtain the subject micro-gel containing polymerizable unsaturated double bond introduced to the surface, giving strength, elongation, water- resistance, etc., and suitable for the original plate for a flexographic printing plate by reacting specific micro-gel fine particles with a specific compound. CONSTITUTION:The objective micro-gel is produced by reacting (A) micro-gel fine particles obtained by the emulsion-polymerization of a compound having polymerizable unsaturated double bond (e.g. a urethane compound having polymerizable unsaturated double bond and/or a polydiene having polymerizable unsaturated double bond on chain terminal or side chain) using an emulsifier consisting of a compound containing tertiary ammonium salt with (B) a compound having an epoxy group reactive with tertiary ammonium salt and one or more polymerizable unsaturated double bonds in one molecule, thereby introducing polymerizable unsaturated double bonds on the surface of the micro-gel particle. The above emulsifier may be used in combination with a lowmolecular surfactant (e.g. a nonionic surfactant).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-developable photosensitive resin composition, and more specifically to a photosensitive microgel having rubber elasticity and having a polymerizable unsaturated double bond on the surface of gel particles. The present invention relates to a printing plate precursor that requires rubber elasticity, such as a flexographic printing plate, produced using a photosensitive resin composition containing

[0002]

2. Description of the Related Art In recent years, flexo printing has come into the limelight with the modernization of packaging. However, in the conventional flexo plate manufacturing method (a)
It requires at least three steps such as metal plate making, (b) mold making, and (c) vulcanization of raw rubber, which requires skilled techniques and a long time. I didn't get it. As a solution to these drawbacks, a solvent-developable photosensitive resin plate has been developed, and it has become possible to easily make a flexographic plate. However, since a diene rubber such as polybutadiene is used as a base material, a halogen-based solvent such as trichlene and perkrene must be used as a developing solution when developing, which is a problem in terms of environmental pollution and toxicity to the human body. . Therefore, there has been a long-awaited demand for a flexographic plate that can be developed with water that is non-toxic to the human body and that has resistance to water-based inks that are commonly used in flexographic printing. However, it has been difficult with conventional techniques to satisfy the contradictory requirements of water developability, water resistance and alcohol resistance. Therefore, the present inventor invented a novel method for synthesizing a reactive microgel (Japanese Patent Laid-Open No. 01-26380).
5) The application to a flexographic plate was examined, but it was difficult to obtain a satisfactory rubber elasticity.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The inventor of the present invention has conducted extensive studies to develop a photosensitive resin composition which can be developed in water and has physical properties required for flexographic printing plates. Among the photosensitive resin compositions containing a photosensitive microgel having a bond, those containing a photosensitive microgel obtained by using a urethane compound or a polydiene in the inside (core) are particularly flexible, water-resistant and alcohol-resistant. The present invention has been accomplished by discovering that it has excellent rolling property and elongation.

[0004]

According to the present invention, a compound having a polymerizable unsaturated double bond is emulsion-polymerized as an emulsifier by using a tertiary ammonium salt-containing compound alone or in combination with a low molecular surfactant. The microgel fine particles (A) synthesized by the method described above are reacted with the compound (B) having an epoxy group and at least one polymerizable unsaturated double bond which react with a tertiary ammonium salt in one molecule, and the surface thereof is reacted. In a photosensitive microgel prepared by introducing a polymerizable unsaturated double bond, the compound having a polymerizable unsaturated double bond is a urethane compound having a polymerizable unsaturated double bond and / or a polymerizable compound at the terminal or side chain. The polydiene having an unsaturated double bond (hereinafter referred to as polydiene having a polymerizable unsaturated double bond), or these compounds and the polymerizable unsaturated double bond The present invention relates to a photosensitive microgel characterized by being a mixture with other compounds, a photosensitive resin composition for flexographic printing plates containing the same, and a flexographic printing plate precursor comprising the photosensitive resin composition. .

The photosensitive microgel, which is the main component of the photosensitive resin composition of the present invention, comprises urethane compounds and / or polydienes having a polymerizable unsaturated double bond, or these compounds and a polymerizable unsaturated double bond. It is characterized in that it is emulsion-polymerized with a mixture with another compound having, and further has a photosensitive group on its surface.

The urethane compound having a polymerizable unsaturated double bond can be produced from a diol compound, a diisocyanate compound and a compound having a hydroxyl group and a polymerizable unsaturated double bond. As the diol compound, various lactones such as β-
Propiolactone and its substituted form, δ-valerolactone and its substituted form, ε-caprolactone, etc. 4-membered ring, 6-membered ring, 7-membered ring or more lactone in the presence or absence of catalyst with or without catalyst. Ring-opening-polymerized into, or a glycol component condensed with a dibasic acid under conditions of excess glycol component, such as polyethylene adipate, polypropylene adipate, polyethylene succinate, polyhexamethylene adipate, etc. Examples thereof include polyethylene glycol, polypropylene glycol, polyepichlorohydrin and the like. As the diisocyanate compound, toluylene diisocyanate, diphenylmethane-4,
4 diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like. Examples of the compound having a hydroxyl group and a polymerizable unsaturated double bond include hydroxyethyl (meth) arylate, hydroxypropyl (meth) acrylate and allyl alcohol.

The polydiene having a polymerizable unsaturated double bond is a polymer of a conjugated diene compound having an epoxy group or an acid anhydride group at a terminal or a side chain, such as polybutadiene,
A compound having a functional group capable of reacting with these groups in polyisoprene and the like and a polymerizable unsaturated double bond, for example, a C2 to C20 hydroxyalkyl ester such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate. Alternatively, it can be obtained by reacting allyl alcohol, allylamine and the like.

The urethane compound and / or polydienes having a polymerizable unsaturated double bond synthesized by using the above compound may be used alone or in combination with other compounds having a polymerizable unsaturated double bond. Used in gel synthesis. As other compounds having a polymerizable unsaturated double bond, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (meth)
Isopropyl acrylate, Butyl (meth) acrylate,
C1-C18 alkyl ester of (meth) acrylic acid such as hexyl (meth) acrylate, octyl (meth) acrylate, and lauryl (meth) acrylate: glycidyl (meth) acrylate: allyl (meth) acrylate ) C2 to C20 alkenyl ester of acrylic acid: C2 to C20 hydroxyalkyl ester of (meth) acrylic acid such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate: allyloxylethyl (meth) acrylate and the like ( C3 to C19 alkenyloxyl alkyl esters of (meth) acrylic acid: (meth) acrylic acid, trimethylolpropane tri (meth) acrylic acid ester, di (meth) acrylic acid ester of glycols, di (meth) acrylic acid of polyol Ester, polyureta Examples thereof include di (meth) acrylic acid esters of polyesters, di (meth) acrylic acid esters of polyesters, styrene, and divinylbenzene. The urethane compound and / or polydienes having a polymerizable unsaturated double bond and other compounds having a polymerizable unsaturated double bond may be freely mixed in a weight ratio of 100: 0 to 0.1: 99.9. it can.

Further, in order to satisfy various resistances and characteristics required for the flexographic printing plate, it is desirable to three-dimensionally crosslink the inside (core) of the microgel fine particles (A). It is desirable to use one or more kinds of compounds having one or more polymerizable unsaturated double bonds, that is, polyfunctional monomers and oligomers.

A urethane compound having a polymerizable unsaturated double bond and / or a compound containing a tertiary ammonium salt for emulsifying polydienes is effective as an emulsifier, and is usually a compound having a tertiary amino group. What is neutralized with an acid and subjected to tertiary chloride is used.

Examples of low molecular weight emulsifiers include dimethyllaurylamine, dimethylmyristylamine, dimethylpalmitylamine, dimethylstearylamine, diethyllaurylamine, diethylmyristylamine, diethylpalmitylamine and diethylstearylamine. C6 to C20 alkyl and alkenyl 3
Hydrochloric acid, nitric acid, sulfuric acid, acetic acid, propionic acid, which is a tertiary amine of a reactive monomer having an amino group such as a secondary amine, 2,2-dimethylaminoethyl (meth) acrylate, and 2,2-diethylaminoethyl (meth) acrylate , Butyric acid, (meth)
There are reactants with acids such as acrylic acid.

As the polymer emulsifier, a reactive monomer having an amino group such as 2,2-dimethylaminoethyl (meth) acrylate and 2,2-diethylaminoethyl (meth) acrylate and another reactive monomer, for example, Methyl (meth) acrylate, ethyl (meth) acrylate, (meth)
C1-C18 alkyl of (meth) acrylic acid such as propyl acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, and lauryl (meth) acrylate. Ester: C2-C8 alkenyl ester of (meth) acrylic acid such as allyl (meth) acrylate: C2-C8 hydroxyalkyl of (meth) acrylic acid such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate Ester: C3 to C19 alkenyloxyl alkyl ester of (meth) acrylic acid such as allyloxylethyl (meth) acrylate:
Examples thereof include those obtained by copolymerizing at least one vinyl monomer selected from (meth) acrylic acid and the like and then neutralizing with an acid. Further, natural polymers such as chitosan and synthetic polymers such as polyethyleneimine, which have been neutralized with an acid, can also be mentioned.

These polymeric emulsifiers may be used as they are or by reacting a part of the tertiary ammonium salt with a compound containing an epoxy group such as glycidyl (meth) acrylate and a polymerizable unsaturated double bond. It can also be used as a reactive emulsifier by introducing a saturated double bond. By using a reactive emulsifier, it becomes possible to fix the emulsifier itself to the core when three-dimensionally crosslinking the inside of the microgel fine particles (A). By fixing an emulsifier (shell) to the inside (core) of the microgel microparticles (A), the flexographic printing plate using this photosensitive microgel can have various strengths, elongations, hardnesses, water resistances, abrasion resistances and the like. Resistance can be improved. The polymeric emulsifier is 0.
1 to 80% by weight, preferably 3 to 50% by weight is used. When used in combination with the following low molecular weight surfactant, it is used in an amount of 0.1 to 50% by weight, preferably 3 to 20% by weight.

Examples of the low-molecular-weight surfactant used in combination with the above-mentioned polymeric emulsifier include nonionic surfactants and cationic surfactants. As the nonionic surfactant, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene alkyl ether such as polyoxyethylene cetyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, etc. Examples include sorbitan fatty acid esters such as ethylene alkyl allyl ether, polyoxyethylene derivatives, oxyethylene / oxypropylene block copolymers, sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate, glycerin fatty acid esters, and polyoxyethylene fatty acid esters. .

Examples of the cationic surfactant include hydrochlorides of primary amines such as monomethylamine, monoethylamine and monostearylamine, hydrochlorides of secondary amines such as dimethylamine, diethylamine and distearylamine, trimethylamine and triethylamine. Hydrochlorides of tertiary amines such as stearyldimethylamine, hydrochlorides of ethanolamines such as monoethanolamine, diethanolamine and triethanolamine, hydrochlorides of polyethylenepolyamines such as ethylenediamine and diethylenetriamine, amines such as pyridine, morpholine and hydrazine And the like.

The above low-molecular-weight surfactant is used in an amount of 0.1 to 50%, preferably 0.1 to 20%, based on the compound having a polymerizable unsaturated double bond. The temperature of emulsion polymerization is 50 to 9
The temperature is 5 ° C, preferably 65 to 80 ° C. The emulsion polymerization is carried out at a solid content of 10 to 50%, preferably 15 to 30%, which is the total of the compound having a polymerizable unsaturated double bond and the emulsifier. In the present invention, the particle size of the microgel produced by emulsion polymerization is usually 10 to 5 as measured by a light scattering method.
00 nm.

The tertiary ammonium salt present on the surface of the microgel particles (A) thus produced and the compound (B) having an epoxy group and at least one polymerizable unsaturated double bond in one molecule. And are reacted to introduce a polymerizable unsaturated double bond on the surface of the microgel fine particles.
Examples of the compound (B) include epoxy compounds having a polymerizable unsaturated double bond such as glycidyl (meth) acrylate, N-glycidyl (meth) acrylamide, glycidyl allyl ether, and 1,2-epoxy-5-hexene. . These compounds (B) are appropriately selected according to the desired physical properties and can be used alone or in combination of two or more. 1 to 100 relative to the tertiary ammonium base on the surface of the microgel particles
It is possible to react in any proportion up to mol%. This reaction is completed simply by mixing the microgel emulsion with the epoxy compound and stirring at a temperature of 30 to 90 ° C, preferably 60 to 80 ° C for 2 hours or more. As described above, the present invention has an advantage that a polymerizable unsaturated double bond can be easily attached to the surface of the microgel even in an aqueous dispersion.

The photosensitive microgel produced as described above is added with an additive such as a photopolymerization initiator, other water-based resin, and a hydrophilic monomer as required to prepare a photosensitive resin composition for a flexographic printing plate, After that, it can be made into a sheet to form a flexographic printing original plate. Then, by crosslinking with radiation such as ultraviolet rays and electron beams, a flexographic printing plate which is water-developable and rich in water resistance is provided.

Crosslinking by radiation occurs even without a photopolymerization initiator, but in the case of ultraviolet irradiation, the crosslinking efficiency is enhanced by adding an appropriate photopolymerization initiator. As the photopolymerization initiator, benzophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) 2-hydroxy-2-methylpropan-1-one, 2-methyl-1 -
[4- (Methylthio) phenyl] 2-morpholinopropanone
-1 etc. These photopolymerization initiators are resin 100
It is used in the range of 0.1 to 10 parts by weight with respect to parts by weight. Examples of other water-based resins include polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, casein, gelatin, starch, polyvinyl pyrrolidone, poly (meth) acrylamide, chitosan, and tertiary ammonium salt-containing polymers. Examples of hydrophilic monomers are N, N-methylenebis (meth) acrylamide, 1,2-di (meth) acrylamide ethylene glycol, N, N-oxymethylenebisacrylamide, (meth) acrylamide, vinylpyrrolidone, 2-hydroxyethyl. (Meth) acrylate, polyoxyethylene (meth) acrylate, polyoxyethylene di (meth) acrylate and the like can be mentioned. Further, in order to impart various functions to the resin of the present invention, a colorant, an extender pigment, a lubricant, a plasticizer, a stabilizer, a flame retardant, an antifoaming agent, an antioxidant, a bactericidal agent, a conductive material, if necessary. It is also possible to contain additives such as magnetic materials.

[0020]

EXAMPLES The present invention will be described in more detail by way of examples. In the examples, a method for producing a photosensitive microgel, which is the main component in the photosensitive resin composition, will be described. Water resistance after photocuring of a sheet using the photosensitive resin composition, solvent resistance, rubber hardness, The breaking strength, breaking elongation, etc. were evaluated. In the examples, "parts" and "%" indicate parts by weight and% by weight.

A. Synthesis of cationic polymeric emulsifier 140 parts lauryl methacrylate, 60 parts 2-dimethylaminoethyl methacrylate, 200 parts 2-propanol 2 parts
Heated to 80 ° C. in a nitrogen atmosphere with stirring in a 1 liter reactor. Azobisisobutyronitrile (hereinafter referred to as AIBN)
Was added for 1.6 hours, then 0.4 parts of AIBN was added, and then the reaction mixture was kept at 80 ° C. for 4 hours to complete the polymerization. After cooling to room temperature, a mixture of 38.2 parts of acetic acid and 1000 parts of ion-exchanged water was added and heated to remove 2-propanol and water by azeotropic distillation.

B. Synthesis of Reactive Cationic Polymer Emulsifier To the cationic polymer emulsifier synthesized in a), add 9.0 parts of glycidyl methacrylate and add 70 parts in air atmosphere.
A reactive cationic polymer emulsifier having a pendant methacryl group was obtained by heating to 0 ° C. and holding for 2 hours.

C. Synthesis of urethane dimethacrylate 1 100 parts of polyester diol consisting of butanediol-adipic acid having a molecular weight of about 1000, 75 parts of diphenylmethane diisocyanate and 0.1 part of dibutyltin dilaurate are mixed and reacted at 50 ° C for 30 minutes and 90 ° C for 2 hours. , 70 ° C., 26 parts of 2-hydroxyethyl methacrylate were added, and the reaction was continued for another 3 hours to obtain urethane dimethacrylate.

Synthesis Example c c. Synthesis of urethane dimethacrylate 2 Mix 100 parts of polyester diol consisting of butanediol-adipic acid with a molecular weight of about 1000, 52.2 parts of toluylene diisocyanate and 0.1 part of dibutyltin dilaurate.
After reacting at 50 ° C. for 30 minutes and 90 ° C. for 2 hours, the mixture was cooled to 70 ° C., 26 parts of 2-hydroxyethyl methacrylate was added, and the reaction was continued for another 3 hours to obtain urethane dimethacrylate.

Example 1 40 parts of urethane dimethacrylate synthesized in c, 100 parts of reactive cationic polymer emulsifier aqueous solution synthesized in b (solid content 20%), ion-exchanged water 160
Parts were heated to 80 ° C. under nitrogen in a 500 ml reaction vessel with stirring. 8 parts of a 3% azobisamidinopropane dibasic acid salt (hereinafter referred to as AAPD) aqueous solution was added and the mixture was maintained for 2 hours. Then, 2 parts of a 3% AAPD aqueous solution was added. After the addition was completed, the reaction mixture was kept at 80 ° C. for 4 hours to complete the polymerization. The measurement result of the particle size by the light scattering method was about 100 nm. After leaving this microgel aqueous dispersion liquid overnight, 2.1 parts of glycidyl methacrylate was added and the reaction was completed by heating to 70 ° C. in an air atmosphere and holding for 2 hours to obtain a photosensitive microgel aqueous dispersion.

[Example 2] 80 parts of urethane dimethacrylate synthesized in c, 20 parts of polypropylene glycol monomethacrylate, 100 parts of reactive cationic polymer emulsifier aqueous solution synthesized in b (solid content 20%), Emulgen 420 (Kao) Polyoxyethylene oleyl ether manufactured by Co., Ltd.) 2.
5 parts and 320 parts of ion-exchanged water were heated to 80 ° C. in a nitrogen atmosphere while stirring in a 1000 ml reaction vessel. 8% 3% AAPD aqueous solution
And added for 2 hours. Then 2 parts of 3% AAPD aqueous solution was added. After the addition was completed, the reaction mixture was kept at 80 ° C. for 4 hours to complete the polymerization. The particle size measured by the light scattering method is about 10
It was 0 nm. After leaving this microgel aqueous dispersion liquid overnight, 2.1 parts of glycidyl methacrylate was added and the reaction was completed by heating to 70 ° C. in an air atmosphere and holding for 2 hours to obtain a photosensitive microgel aqueous dispersion.

Example 3 40 parts of the urethane dimethacrylate synthesized in d, 100 parts of the aqueous solution of the cationic polymer emulsifier synthesized in a (solid content 20%), and 160 parts of ion-exchanged water were added.
Heated to 80 ° C. in a 00 ml reaction vessel under nitrogen atmosphere with stirring. 8 parts of a 3% AAPD aqueous solution was added and kept for 2 hours. Incidentally
2 parts of 3% AAPD aqueous solution was added. After the addition is complete, add the reaction mixture
Polymerization was completed by holding at 80 ° C for 4 hours. The measurement result of the particle size by the light scattering method was about 100 nm. After leaving this microgel aqueous dispersion liquid overnight, 2.1 parts of glycidyl methacrylate was added and the reaction was completed by heating to 70 ° C. in an air atmosphere and holding for 2 hours to obtain a photosensitive microgel aqueous dispersion.

Example 4 100 parts of urethane dimethacrylate synthesized in d, 100 parts of an aqueous solution of a cationic polymer emulsifier synthesized in a (solid content 20%), Emulgen 810 (polyoxyethylene octylphenyl manufactured by Kao Corporation) 2.5 parts of ether) and 320 parts of ion-exchanged water were heated to 80 ° C. in a nitrogen atmosphere while stirring in a 1000 ml reaction vessel. 8 parts of a 3% AAPD aqueous solution was added and kept for 2 hours. Then 2 parts of 3% AAPD aqueous solution was added. After the addition was completed, the reaction mixture was kept at 80 ° C. for 4 hours to complete the polymerization. The measurement result of the particle size by the light scattering method was about 100 nm. After leaving this microgel aqueous dispersion liquid overnight, 2.1 parts of glycidyl methacrylate was added and the reaction was completed by heating to 70 ° C. in an air atmosphere and holding for 2 hours to obtain a photosensitive microgel aqueous dispersion.

Example 5 M-1000-80 (Nippon Oil Co., Ltd.)
40 parts of polybutadiene acrylate), 100 parts of cationic polymer emulsifier aqueous solution synthesized in b (solid content 20
%), 2.5 parts of Emulgen 420 (polyoxyethylene oleyl ether manufactured by Kao Corporation), 160 parts of ion-exchanged water
Heated to 80 ° C. in a 500 ml reaction vessel under nitrogen atmosphere with stirring. 8 parts of a 3% AAPD aqueous solution was added and kept for 2 hours. Then 2 parts of 3% AAPD aqueous solution was added. After the addition was completed, the reaction mixture was kept at 80 ° C. for 4 hours to complete the polymerization. The measurement result of the particle size by the light scattering method was about 100 nm. After leaving this microgel aqueous dispersion liquid overnight, 2.1 parts of glycidyl methacrylate was added and the reaction was completed by heating to 70 ° C. in an air atmosphere and holding for 2 hours to obtain a photosensitive microgel aqueous dispersion.

Comparative Example 1 100 parts of a reactive cationic polymer emulsifier aqueous solution (solid content 20%) synthesized in b, 40 parts of polypropylene glycol monomethacrylate, 160 parts of ion-exchanged water were stirred in a 500 ml reaction vessel, In a nitrogen atmosphere
Heated to 80 ° C. 8 parts of a 3% AAPD aqueous solution was added and kept for 2 hours. Then 2 parts of 3% AAPD aqueous solution was added. After the addition was completed, the reaction mixture was kept at 80 ° C. for 4 hours to complete the polymerization. The measurement result of the particle size by the light scattering method was about 100 nm. After leaving this microgel aqueous dispersion liquid overnight, 2.1 parts of glycidyl methacrylate was added and the reaction was completed by heating to 70 ° C. in an air atmosphere and holding for 2 hours to obtain a photosensitive microgel aqueous dispersion.

[Comparative Example 2] 500 parts of an aqueous solution of the reactive cationic polymer emulsifier synthesized in b (solid content 20%), 40 parts of ethylhexyl methacrylate and 160 parts of ion-exchanged water were added.
Heat to 80 ° C. in a nitrogen atmosphere with stirring in a ml reaction vessel. 8 parts of a 3% AAPD aqueous solution was added and kept for 2 hours. Incidentally
2 parts of 3% AAPD aqueous solution was added. After the addition is complete, add the reaction mixture
The temperature was maintained at 80 ° C for 4 hours to complete the polymerization. The measurement result of the particle size by the light scattering method was about 100 nm. After leaving this microgel aqueous dispersion liquid overnight, 2.1 parts of glycidyl methacrylate was added and the reaction was completed by heating to 70 ° C. in an air atmosphere and holding for 2 hours to obtain a photosensitive microgel aqueous dispersion.

Physical Properties Evaluation 40 parts of the photosensitive microgel aqueous dispersions (solid content 25%) obtained in Examples 1, 2, 3, 4, 5 and Comparative Examples 1 and 2 were mixed with Darocur 2959 (Merck photopolymerization). An initiator) 0.5 part was added, and a sheet having a thickness of about 3 mm was prepared by a casting method.
This sheet was irradiated with ultraviolet rays at about 4000 mJ / cm ² to obtain a cured product. At room temperature (25 ° C.), the rubber hardness, breaking strength, breaking elongation, water swelling ratio, sodium carbonate (Na ₂ CO ₃ ) aqueous solution swelling ratio, and isopropyl alcohol (IPA) swelling ratio of this cured product were measured. Rubber hardness: According to JIS-K6301. Breaking strength: Measured with a tensile tester. Breaking elongation Sample size 10mm * 20mm * 3mm Pulling speed 50mm / min Water swelling rate: Soaking rate was measured by immersing in ion-exchanged water for 24 hours. Na ₂ CO ₃ swelling ratio: The swelling ratio was measured by immersing in Na ₂ CO ₃ aqueous solution (pH = 9) for 24 hours. IPA swelling ratio: The swelling ratio was measured by immersing in IPA for 24 hours. Swelling rate = [(weight after soaking for 24 hours / weight before soaking) -1] * 100 Resolution: overlay a mask film with various line width patterns on each sheet, irradiate with ultraviolet rays, and develop with water. The thinnest line width obtained as a result was defined as the resolution. The results are shown in Table 1.

[0033]

[Table 1]

[0034]

EFFECT OF THE INVENTION By using a urethane compound and / or polydienes having a polymerizable unsaturated double bond as the core of the photosensitive microgel, flexibility after curing, water resistance, alkali resistance, and alcohol resistance are obtained. It has become possible to produce a flexographic printing plate precursor which is excellent in water development and can be developed in water.

Claims (7)

[Claims] 1. Microgel fine particles (A) synthesized by emulsion polymerization of a compound having a polymerizable unsaturated double bond using a tertiary ammonium salt-containing compound as an emulsifier, and 1.
Photosensitized by reacting an epoxy group which reacts with a tertiary ammonium salt in the molecule and a compound (B) having at least one polymerizable unsaturated double bond to introduce a polymerizable unsaturated double bond on the surface. In the water-soluble microgel, the compound having a polymerizable unsaturated double bond is a urethane compound having a polymerizable unsaturated double bond and / or a polydiene having a polymerizable unsaturated double bond at the terminal or side chain. A photosensitive microgel characterized by: 2. A compound having a polymerizable unsaturated double bond,
The photosensitive microgel according to claim 1, comprising a compound having a polymerizable unsaturated double bond other than a urethane compound or polydienes. 3. The photosensitive microgel according to claim 1, wherein the tertiary ammonium salt-containing compound contains a polymerizable unsaturated double bond. 4. A low-molecular-weight surfactant together with a compound containing a tertiary ammonium salt is used as an emulsifier when emulsion-polymerizing the microgel particles (A).
3. The photosensitive microgel according to any one of 3 to 3. 5. The photosensitive microgel according to claim 1, wherein the low-molecular-weight surfactant is a nonionic surfactant or a cationic surfactant. 6. A photosensitive resin composition for a flexographic printing plate, which comprises the photosensitive microgel according to any one of claims 1 to 5. 7. A flexographic printing plate precursor comprising the photosensitive resin composition for flexographic printing plate according to claim 6.