Photosensitive resin composition for flexographic printing

Abstract

To provide a photosensitive resin composition for flexographic printing which has excellent solvent resistance.SOLUTION: The photosensitive resin composition for flexographic printing contains the following components (A)-(E): (A) a first styrene-butadiene-styrene block copolymer (SBS); (B) a second styrene-butadiene-styrene block copolymer (SBS); (C) polybutadiene or a derivative thereof; (D) a photopolymerizable monomer; and (E) a photopolymerization initiator. The photosensitive resin composition for flexographic printing contains 5-100 wt.% of (B), 10-40 wt.% of (C), 40-200 wt.% of (D), and 4-20 wt.% of (E) based on (A).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a photosensitive resin composition for flexographic printing. This application claims priority to Japanese Patent Application No. 2020-085991, filed on May 15, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] The photosensitive resin composition for flexographic printing generally contains a thermoplastic elastomer, a photopolymerizable unsaturated monomer, a plasticizer, and a photopolymerization initiator. The components for flexographic printing plates generally include a support such as a polyester film on which the above-mentioned photosensitive resin composition is provided, and further, on the photosensitive resin composition, a slip layer, a protective layer, or an ultraviolet shielding layer containing an infrared-sensitive material that can be ablated by an infrared laser is provided for the purpose of preventing adhesion with a negative film. To make a flexographic printing plate from such a photosensitive resin plate material for flexographic printing plates, first, the entire surface is exposed to ultraviolet light through the support (back exposure) to provide a thin, uniform cured layer (floor layer), and then, through a negative film or directly from above the ultraviolet shielding layer on which a photomask is formed by an infrared laser, image exposure (relief exposure) is performed on the surface of the photosensitive resin layer, and the unexposed parts are washed away with a developing solvent, or are absorbed and removed by an absorbing layer after thermal melting, and then exposed to post-treatment. In general printing using a photosensitive resin plate for flexographic printing, ink is supplied to the convex surface of the uneven resin plate by an ink supply roll or the like, and then the resin plate is brought into contact with the print substrate, and the ink on the convex surface is transferred to the print substrate. Examples of such general inks for flexographic printing include water-based inks, emulsion inks, and organic solvent-based inks, such as UV-curable inks, or inks using vegetable oil or light naphtha. In such flexographic printing, which uses an organic solvent for development during plate making, resistance to organic solvent-based inks is required. If the solvent resistance is insufficient, problems occur such as the printing plate being destroyed during long-term printing, or the printing plate swelling and deformation, resulting in printing in a form other than the original image required for printing. In order to overcome the above problems, several methods have been proposed regarding the solvent resistance of such photosensitive resin compositions.

[0003] Patent Document 1 proposes a photosensitive resin composition for flexographic printing, which is characterized by containing a thermoplastic elastomer, a (meth)acrylic modified liquid polybutadiene containing 80% or more of 1,2-bonds, a photopolymerizable unsaturated monomer having one or more ethylenically unsaturated groups, and a photopolymerization initiator. It is described that this composition has excellent resistance to inks containing organic solvents used in flexographic printing, emulsion inks, such as UV-curable inks, or inks using vegetable oil or light naphtha, and is also excellent in suitability for printing applications such as image reproducibility and printing durability. Patent Document 2 describes a flexographic printing plate-making material composition that contains 50-90% by mass of a thermoplastic elastomer, 5-40% by mass of a specific polybutadiene, 1-30% by mass of an ethylenically unsaturated compound, and 0.1-3% by mass of a photopolymerization initiator, and has an elastic modulus of 80-150 MPa after photocuring. The specific polybutadiene is obtained by anionic polymerization of 1,3-butadiene under reaction temperature conditions below the boiling point of butadiene and in the presence of a polymerization initiator, in an aprotic polar solvent or a mixed solvent of an aprotic polar solvent and a nonpolar solvent, in the presence of a potassium salt. It also describes that a styrene-butadiene-styrene block polymer can be selected as the thermoplastic elastomer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2010 / 116743 [Patent Document 2] International Publication No. 2011 / 045918 Summary of the Invention [Problem to be solved by the invention]

[0005] The cured products obtained from the compositions described in Patent Documents 1 and 2 often have insufficient solvent resistance. An object of the present invention is to provide a photosensitive resin composition for flexographic printing that has excellent solvent resistance. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. The present invention includes the following aspects. (1)(A) a first styrene-butadiene-styrene block copolymer (SBS); (B) a second styrene-butadiene-styrene block copolymer (SBS); (C) polybutadiene or a derivative thereof; (D) a photopolymerizable monomer; (E) a photopolymerization initiator, A photosensitive resin composition for flexographic printing comprising: (2) The photosensitive resin composition for flexographic printing according to (1), wherein the butadiene block in the first styrene-butadiene-styrene block copolymer (A) has a molar ratio of 1,2 bond structure to 1,4 bond structure of 0:100 to 70:30. (3) The photosensitive resin composition for flexographic printing according to (1) or (2), wherein the weight average molecular weight (Mw) of the first styrene-butadiene-styrene block copolymer (SBS) (A) is 50,000 to 500,000. (4) The photosensitive resin composition for flexographic printing according to any one of (1) to (3), wherein the molecular weight distribution (Mw / Mn) of the first styrene-butadiene-styrene block copolymer (A) is 1 to 10. (5) The photosensitive resin composition for flexographic printing according to any one of (1) to (4), wherein the weight ratio of the styrene block to the butadiene block in the (A) first styrene-butadiene-styrene block copolymer (SBS) is 10:90 to 80:20. (6) (B) The photosensitive resin composition for flexographic printing according to any one of (1) to (5), wherein the butadiene block in the second styrene-butadiene-styrene block copolymer (SBS) has a molar ratio of 1,2 bond structure to 1,4 bond structure of 80:20 to 100:0. (7) The photosensitive resin composition for flexographic printing according to any one of (1) to (6), wherein the weight average molecular weight (Mw) of the second styrene-butadiene-styrene block copolymer (SBS) (B) is 10,000 to 100,000. (8) The photosensitive resin composition for flexographic printing according to any one of (1) to (7), wherein the molecular weight distribution (Mw / Mn) of the second styrene-butadiene-styrene block copolymer (SBS) (B) is 1 to 3. (9) The photosensitive resin composition for flexographic printing according to any one of (1) to (8), wherein the weight ratio of the styrene block to the butadiene block in the second styrene-butadiene-styrene block copolymer (SBS) (B) is 10:90 to 80:20. (10) The photosensitive resin composition for flexographic printing according to any one of (1) to (9), comprising (B) the second styrene-butadiene-styrene block copolymer (SBS) in an amount of 5 to 100% by weight relative to (A) the first styrene-butadiene-styrene block copolymer (SBS). (11) The photosensitive resin composition for flexographic printing according to any one of (1) to (10), wherein the molar ratio of the 1,2 bond structure to the 1,4 bond structure in the polybutadiene (C) or a derivative thereof is 80:20 to 100:0. (12) The photosensitive resin composition for flexographic printing according to any one of (1) to (11), wherein the weight average molecular weight (Mw) of the polybutadiene or a derivative thereof (C) is 1,000 to 10,000. (13) The photosensitive resin composition for flexographic printing according to any one of (1) to (12), wherein the molecular weight distribution (Mw / Mn) of the polybutadiene or a derivative thereof (C) is 1 to 3. (14) The photosensitive resin composition for flexographic printing according to any one of (1) to (13), containing (C) polybutadiene or a derivative thereof in an amount of 10 to 40% by weight relative to (A) the first styrene-butadiene-styrene block copolymer (SBS). (15) The photosensitive resin composition for flexographic printing according to any one of (1) to (14), comprising (D) a photopolymerizable monomer in an amount of 40 to 200% by weight relative to (A) the first styrene-butadiene-styrene block copolymer (SBS). (16) The photosensitive resin composition for flexographic printing according to any one of (1) to (15), containing a photopolymerization initiator (E) in an amount of 4 to 20% by weight relative to the first styrene-butadiene-styrene block copolymer (A) (SBS). Effect of the Invention

[0007] According to the photosensitive resin composition for flexographic printing of the present invention, a material for flexographic printing having excellent solvent resistance can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The photosensitive resin composition for flexographic printing of the present invention contains a first styrene-butadiene-styrene block copolymer (component A), a second styrene-butadiene-styrene block copolymer (component B), polybutadiene or a derivative thereof (component C), a photopolymerizable monomer (component D), and a photopolymerization initiator (component E).

[0009] (First styrene-butadiene-styrene block copolymer (component A)) Component (A) in the photosensitive resin composition for flexographic printing of the present invention is a styrene-butadiene-styrene block copolymer (hereinafter sometimes referred to as SBS). The styrene-butadiene-styrene block copolymer is a triblock copolymer in which a butadiene block and a styrene block are bonded in the order of a styrene block, a butadiene block, and a styrene block. The styrene block is a block polymerized with styrene, and the butadiene block is a block polymerized with 1,3-butadiene.

[0010] The repeating units in the butadiene block in the first SBS used in the present invention are composed of a 1,2 bond structure represented by the following formula (1) and a 1,4 bond structure represented by the following formula (2), or are composed only of a 1,4 bond structure represented by the following formula (2). The molar ratio of the 1,2 bond structure to the 1,4 bond structure constituting the butadiene block in the first SBS can be selected from 0:100 to 70:30, 0:100 to 60:40, 0:100 to 50:50, 0:100 to 40:60, 0:100 to 30:70, 0:100 to 20:80, etc. The molar ratio of 1,2 bond structure to 1,4 bond structure is 1 It can be calculated by H-NMR. That is, the 1,2 bond structure -CH=CH 2 CH and CH 2 The ratio of 1,2- and 1,4-microstructures can be calculated from the integral value of the protons of the two CH of the 1,4 bond structure -CH=CH-. [ka]

[0011] The weight average molecular weight (Mw) of the first SBS used in the present invention is not particularly limited, and can be selected from 50,000 to 500,000, 50,000 to 400,000, 50,000 to 300,000, 50,000 to 200,000, and 100,000 to 500,000. The molecular weight distribution (Mw / Mn) of the first SBS used in the present invention is not particularly limited, and can be 1 to 10. The weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) are measured by gel permeation chromatography (GPC) using polystyrene as a standard substance. The measurement conditions are: mobile phase THF (tetrahydrofuran), mobile phase flow rate 1 mL / min, column temperature 40° C., sample injection amount 40 μL, and sample concentration 2 wt%.

[0012] The weight ratio of the styrene block to the butadiene block in the first SBS used in the present invention is not particularly limited, and can be selected from 10:90 to 80:20, 10:90 to 70:30, 10:90 to 60:40, 10:90 to 50:50, 20:90 to 50:50, and the like.

[0013] The method for producing the first SBS used in the present invention is not particularly limited, but it can be produced by the methods described in JP-A-6-192502, JP-T-2000-514122, JP-A-2007-302901, etc., or methods equivalent thereto. The first SBS can be a commercially available product. Examples of commercially available products include Kraton D1101JS (manufactured by Kraton).

[0014] (Second Styrene-Butadiene-Styrene Block Copolymer (Component B)) Component (B) in the photosensitive resin composition for flexographic printing of the present invention is a styrene-butadiene-styrene block copolymer (SBS). The styrene-butadiene-styrene block copolymer is a triblock copolymer in which a butadiene block and a styrene block are bonded in the order of a styrene block, a butadiene block, and a styrene block. The styrene block is a block polymerized with styrene, and the butadiene block is a block polymerized with 1,3-butadiene.

[0015] The repeating units in the butadiene block in the second SBS used in the present invention are composed of the 1,2 bond structure represented by the formula (1) and the 1,4 bond structure represented by the formula (2), or are composed only of the 1,2 bond structure represented by the formula (1). The molar ratio of the 1,2 bond structure to the 1,4 bond structure constituting the butadiene block in the second SBS can be selected from 80:20 to 100:0, 80:20 to 95:5, 85:15 to 95:5, etc. The molar ratio of 1,2 bond structure to 1,4 bond structure is 1 It can be calculated by H-NMR. That is, the 1,2 bond structure -CH=CH 2 CH and CH 2The ratio of 1,2- and 1,4-microstructures can be calculated from the integral value of the protons of the two CH of the 1,4 bond structure -CH=CH-.

[0016] The weight average molecular weight (Mw) of the second SBS used in the present invention is not particularly limited, and can be selected from 10,000 to 100,000, 10,000 to 90,000, 10,000 to 80,000, 10,000 to 70,000, 10,000 to 60,000, and 10,000 to 50,000. The molecular weight distribution (Mw / Mn) of the second SBS used in the present invention is not particularly limited, and can be 1 to 3. The weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) are measured by gel permeation chromatography (GPC) using polystyrene as a standard substance. The measurement conditions are: mobile phase THF (tetrahydrofuran), mobile phase flow rate 1 mL / min, column temperature 40° C., sample injection amount 40 μL, and sample concentration 2 wt%.

[0017] The weight ratio of the styrene block to the butadiene block in the second SBS used in the present invention is not particularly limited, and can be selected from 10:90 to 80:20, 20:80 to 80:20, 30:70 to 80:20, 40:60 to 80:20, 40:60 to 70:30, 40:60 to 60:40, and the like.

[0018] The method for producing the second SBS used in the present invention is not particularly limited, but it can be produced by the methods described in JP-A-6-192502, JP-T-2000-514122, JP-A-2007-302901, etc., or methods equivalent thereto.

[0019] The amount of the second SBS contained in the photosensitive resin composition for flexographic printing of the present invention is not particularly limited, but can be an amount such that the amount of the second SBS is 5 to 100% by weight relative to the amount of the first SBS.

[0020] (Polybutadiene or its derivatives (component C)) The component (C) in the photosensitive resin composition for flexographic printing of the present invention is polybutadiene or a derivative thereof. Polybutadiene is a polymer obtained by polymerizing 1,3-butadiene. Polybutadiene derivatives include hydrogenated polybutadiene and terminal-modified polybutadiene, which will be described later.

[0021] The repeating units in the polybutadiene used in the present invention are composed of the 1,2 bond structure represented by the formula (1) and the 1,4 bond structure represented by the formula (2), or are composed only of the 1,2 bond structure represented by the formula (1), or are composed only of the 1,4 bond structure represented by the formula (2). The molar ratio of the 1,2 bond structure and the 1,4 bond structure constituting the polybutadiene is not particularly limited, and can be selected from 80:20 to 100:0, 80:20 to 95:5, 85:15 to 95:5, etc. The molar ratio of the 1,2 bond structure and the 1,4 bond structure is, 1 It can be calculated by H-NMR. That is, the 1,2 bond structure -CH=CH 2 CH and CH 2 The ratio of 1,2- and 1,4-microstructures can be calculated from the integral value of the protons of the two CH of the 1,4 bond structure -CH=CH-.

[0022] The 1,2 bond structure represented by the formula (1) and the 1,4 bond structure represented by the formula (2), which are repeating units in the polybutadiene used in the present invention, may be partially or entirely hydrogenated. When partially hydrogenated, the hydrogenation rate can be selected from 1 to 99 mol%, 1 to 90 mol%, 1 to 80 mol%, 1 to 70 mol%, 1 to 60 mol%, 1 to 50 mol%, 1 to 40 mol%, 1 to 30 mol%, 1 to 20 mol%, 1 to 10 mol%, etc. The hydrogenation rate is the ratio of hydrogenated repeating units to all repeating units constituting the polybutadiene.

[0023] The polybutadiene used in the present invention may have a modified terminal structure. Examples of polybutadienes having modified terminal structures include those having various structures such as those having terminals modified with hydroxyl groups, those having terminals modified with acryl groups, those having terminals modified with methacryl groups, and those having terminals modified with carboxylic acid groups, but are not limited thereto.

[0024] The weight average molecular weight (Mw) of the polybutadiene or derivative thereof used in the present invention is not particularly limited, and can be selected from 1,000 to 10,000, 1,000 to 5,000, etc. The molecular weight distribution (Mw / Mn) of the polybutadiene used in the present invention is not particularly limited, and can be 1 to 3. The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) are values ​​obtained by converting data measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent based on the molecular weight of standard polystyrene.

[0025] The method for producing the polybutadiene or its derivatives used in the present invention is not particularly limited, and the polybutadiene or its derivatives can be produced by known methods. In addition, the polybutadiene or its derivatives used in the present invention can be commercially available products. Specific examples of the polybutadiene or derivatives thereof used in the present invention include polybutadienes with unmodified terminals such as NISSO-PB B-1000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB B-2000 (manufactured by Nippon Soda Co., Ltd.), and NISSO-PB B-3000 (manufactured by Nippon Soda Co., Ltd.), hydrogenated polybutadienes such as NISSO-PB BI-2000 (manufactured by Nippon Soda Co., Ltd.) and NISSO-PB BI-3000 (manufactured by Nippon Soda Co., Ltd.), polybutadienes modified at both ends with hydroxyl groups such as NISSO-PB G-1000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB G-2000 (manufactured by Nippon Soda Co., Ltd.), and NISSO-PB G-3000 (manufactured by Nippon Soda Co., Ltd.), and polybutadienes modified at both ends with hydroxyl groups such as NISSO-PB GI-1000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB GI-2000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB Examples of such polybutadienes include hydrogenated polybutadienes modified with hydroxyl groups at both ends, such as GI-3000 (manufactured by Nippon Soda Co., Ltd.), and polybutadienes modified with methacryl groups at both ends, such as NISSO-PB TE-2000 (manufactured by Nippon Soda Co., Ltd.).

[0026] The amount of polybutadiene or a derivative thereof contained in the photosensitive resin composition for flexographic printing of the present invention is not particularly limited, but an example of the amount of polybutadiene or a derivative thereof is 10 to 40% by weight relative to the amount of the first SBS.

[0027] (Photopolymerizable monomer (component D)) As the photopolymerizable monomer, a monofunctional or polyfunctional monomer can be used. Examples of these compounds include compounds having a carbon-carbon double bond, specifically, unsaturated carboxylic acid ester compounds, unsaturated carboxylic acid amide compounds, allyl compounds, styrene compounds, N-substituted maleimide compounds, etc. More specifically, the following compounds are included: As the monofunctional monomer, (Meth)acrylic acid ester compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, t-butyl (meth)acrylate, and lauryl (meth)acrylate; (Meth)acrylic acid amide compounds such as (meth)acrylamide and diacetone acrylamide; Allyl compounds such as allyl acetate, allyl methyl ether, and allyl phenyl ether; Styrenic compounds such as styrene, α-methylstyrene, and vinyltoluene; Fumaric acid or maleic acid ester compounds such as dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, distearyl fumarate, butyloctyl fumarate, diphenyl fumarate, dibenzyl fumarate, dibutyl maleate, dioctyl maleate, bis(3-phenylpropyl) fumarate, dilauryl fumarate, and dibehenyl fumarate; Examples of the maleimide include N-substituted maleimide compounds such as Nn-hexylmaleimide, N-cyclohexylmaleimide, Nn-octylmaleimide, N-2-ethylhexylmaleimide, Nn-decylmaleimide, and Nn-laurylmaleimide. Examples of polyfunctional monomers include: Bifunctional ethylenically unsaturated compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, divinylbenzene, and diallyl phthalate; Trifunctional ethylenically unsaturated compounds such as trimethylolpropane tri(meth)acrylate and triallyl cyanurate; Examples of the ethylenically unsaturated compound include tetrafunctional ethylenically unsaturated compounds such as pentaerythritol tetra(meth)acrylate. These may be used alone or in combination of two or more.

[0028] The amount of the photopolymerizable monomer contained in the photosensitive resin composition for flexographic printing of the present invention is not particularly limited, but can be selected from amounts such that the amount of the photopolymerizable monomer is 40 to 200% by weight, 40 to 150% by weight, or 50 to 150% by weight relative to the amount of the first SBS.

[0029] (Photopolymerization initiator (component E)) Specific examples of photopolymerization initiators include benzoin and its alkyl ether compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and benzyl methyl ketal; acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, diethoxyacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane-1-one, and the like. acetophenone compounds such as 2-anthraquinone; anthraquinone compounds such as methylanthraquinone, 2-ethylanthraquinone, 2-tertiary-butylanthraquinone, 1-chloroanthraquinone, and 2-amylanthraquinone; thioxanthone compounds such as thioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 2-methylthioxanthone, and 2,4-diisopropylthioxanthone; ketal compounds such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzophenone compounds such as 4,4-bismethylaminobenzophenone. These can be used alone or in combination of two or more.

[0030] The amount of the photopolymerization initiator contained in the photosensitive resin composition for flexographic printing of the present invention is not particularly limited, but can be selected from amounts such that the amount of the photopolymerization initiator relative to the amount of the first SBS is 4 to 20% by weight, 4 to 15% by weight, or 5 to 15% by weight.

[0031] (Other Ingredients) In addition to Components A to E, the photosensitive resin composition for flexographic printing of the present invention may optionally contain a plasticizer, an ultraviolet absorber, an antioxidant, a polymerization inhibitor, a dye, inorganic fine particles, and the like.

[0032] (Method for producing photosensitive resin composition for flexographic printing) The photosensitive resin composition for flexographic printing of the present invention can be produced by mixing each component. As a mixing method, each component can be dissolved and mixed in a suitable solvent such as chloroform, tetrachloroethylene, methyl ethyl ketone, toluene, ethyl acetate, tetrahydrofuran, hexane, cyclohexane, etc., cast into a mold, evaporate the solvent, and form a plate as it is, or a layer with good precision can be obtained by hot pressing the plate of the photosensitive elastomer composition. In addition, after kneading using a kneader, roll mill, etc., a layer of a desired thickness can be produced by hot pressing, calendaring, or extrusion molding. The support or flexible film layer can be adhered to the photosensitive layer by roll lamination after sheet formation. A photosensitive layer with even better precision can also be obtained by hot pressing after lamination.

[0033] (Method of processing photosensitive resin composition for flexographic printing) The actinic radiation source used to make the photosensitive resin composition for flexographic printing of the present invention insoluble in a solvent includes a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an extra-high pressure mercury lamp, a metal halide lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, a xenon lamp, a zirconium lamp, sunlight, etc. After forming an image by irradiating the photosensitive resin composition for flexographic printing of the present invention with light through a transparent image carrier, a developer for dissolving the unexposed area is used that swells and dissolves the unexposed area, but it is preferable that the developer does not have much effect on the image area formed by exposure. For example, tetrachloroethylene, toluene, acetate esters, limonene, decahydronaphthalene, petroleum aromatic hydrocarbons, etc., or a mixture of these with 60% by weight or less of alcohol, such as n-butanol, 1-pentanol, benzyl alcohol, etc. The unexposed areas are dissolved by spraying from a nozzle or by brushing with a brush. The printing plate obtained by dissolving the unexposed areas using a solvent is swollen by the developing solvent, so it is dried in a forced air stream or an infrared oven. The drying temperature and time are generally 60°C for 30 to 120 minutes. Depending on the composition of the composition of the present invention, the plate surface may remain sticky even after drying. In that case, the stickiness can be removed by a known surface treatment method. As a surface treatment method, exposure treatment with actinic rays having a wavelength of 300 nm or less is preferred. EXAMPLES

[0034] The present invention will be described in detail below using examples, but the present invention is not limited to the scope of the examples. In the following, PB means polybutadiene, and PS means polystyrene.

[0035] Production Example 1 Production of second styrene-butadiene-styrene block copolymer (A) In a 5000 mL flask, 1893.91 g of cyclohexane and 306.92 g of tetrahydrofuran were added. After heating to 30°C, 25.32 g of n-butyllithium (15.1 wt% hexane solution) was added. After stirring for 10 minutes, 150.32 g of styrene was added dropwise and stirred for 10 minutes. Gas chromatography (hereinafter abbreviated as GC) was measured to confirm the disappearance of the monomer. Next, a mixture of 301.30 g of butadiene and 197.50 g of hexane was added dropwise and stirred for 15 minutes. After measuring GC and confirming the disappearance of the monomer, 150.30 g of styrene was added dropwise. After stirring for 30 minutes, 10.40 g of methanol was added. The obtained copolymer was analyzed by gel permeation chromatography (mobile phase: tetrahydrofuran, polystyrene standard) and confirmed to have a weight average molecular weight (Mw) of 19603, a molecular weight distribution (Mw / Mn) of 1.16, and a composition ratio of PS / PB / PS = 25 / 50 / 25% by weight. The reaction solution was washed twice with water, and the solvent was distilled off. Styrene-butadiene-styrene copolymer (A) (white powder) was obtained by vacuum drying. 1The molar ratio of 1,2 bond structure to 1,4 bond in the butadiene block calculated by H-NMR was 94:6.

[0036] Production Example 2 Production of second styrene-butadiene-styrene block copolymer (B) In a 1000 mL flask, 439.50 g of cyclohexane and 32.45 g of tetrahydrofuran were added. After heating to 30°C, 3.82 g of n-butyllithium (15.1 wt% hexane solution) was added. After stirring for 10 minutes, 61.22 g of styrene was added dropwise and stirred for 10 minutes. Gas chromatography (hereinafter abbreviated as GC) was measured to confirm the disappearance of the monomer. Next, a mixture of 61.05 g of butadiene and 39.20 g of hexane was added dropwise and stirred for 15 minutes. After measuring GC and confirming the disappearance of the monomer, 0.66 g of 1,2-dibromoethane was added dropwise. After the completion of the dropwise addition, 2.12 g of methanol was added to stop the reaction. The obtained copolymer was analyzed by gel permeation chromatography (mobile phase: tetrahydrofuran, polystyrene standard) and confirmed to have a weight average molecular weight (Mw) of 43663, a molecular weight distribution (Mw / Mn) of 1.24, a coupling rate of 80%, and a composition ratio of PS / PB / PS = 25 / 50 / 25% by weight. The reaction solution was washed twice with water, and the solvent was distilled off. Styrene-butadiene-styrene copolymer (B) (white powder) was obtained by vacuum drying. 1 The molar ratio of 1,2 bond structure to 1,4 bond in the butadiene block calculated by H-NMR was 85:15.

[0037] (Production and processing of photosensitive resin compositions for flexographic printing) Example 1 50 parts of Kraton D1101JS (Kraton) (first SBS), 5 parts of SBS (A) (second SBS) synthesized in Production Example 1, 10 parts of B-1000 (polybutadiene manufactured by Nippon Soda), 30 parts of 1,6-hexanediol diacrylate (Tokyo Chemical Industry Co., Ltd., hereinafter HDDA), 3 parts of benzyl methyl ketal (manufactured by Aldrich Co., Ltd.), and 1.9 parts of dibutylhydroxytoluene (manufactured by Kanto Chemical Co., Ltd., hereinafter BHT) were mixed and dissolved in cyclohexane to a non-volatile concentration of 20%. The obtained cyclohexane solution was air-dried in an aluminum cup overnight, and further heated and dried at 50 ° C. for 5 hours. Next, the accumulated light amount was about 6000 mJ / cm 2 The photocured film was peeled off from the aluminum cup to obtain a UV-cured film having a thickness of about 1 mm.

[0038] Example 2 A UV-cured film was obtained in the same manner as in Example 1, except that the amount of Kraton D1101JS (manufactured by Kraton) (first SBS) was 40 parts, and the amount of SBS (A) (second SBS) synthesized in Production Example 1 was 15 parts.

[0039] Example 3 A UV-cured film was obtained in the same manner as in Example 1, except that the amount of Kraton D1101JS (manufactured by Kraton) (first SBS) was 30 parts, and the amount of SBS (A) (second SBS) synthesized in Production Example 1 was 25 parts.

[0040] Example 4 A UV-cured film was obtained in the same manner as in Example 1, except that SBS (B) (second SBS) synthesized in Production Example 2 was used instead of SBS (A) (second SBS) synthesized in Production Example 1.

[0041] Example 5 A UV-cured film was obtained in the same manner as in Example 2, except that SBS (B) (second SBS) synthesized in Production Example 2 was used instead of SBS (A) (second SBS) synthesized in Production Example 1.

[0042] Example 6 A UV-cured film was obtained in the same manner as in Example 3, except that SBS (B) (second SBS) synthesized in Production Example 2 was used instead of SBS (A) (second SBS) synthesized in Production Example 1.

[0043] Comparative Example 1 A UV-cured film was obtained in the same manner as in Example 1, except that the amount of Kraton D1101JS (manufactured by Kraton) (first SBS) added was 55 parts, and the SBS (A) (second SBS) synthesized in Production Example 1 was not added.

[0044] (hardness measurement) For the UV-cured films obtained in Examples 1 to 6 and Comparative Example 1, the hardness was measured using a durometer in accordance with JIS K 7215.

[0045] (Solvent resistance test) The UV-cured films obtained in Examples 1 to 6 and Comparative Example 1 were cut into test pieces measuring 5 cm x 5 cm, and immersed in a beaker filled with ethyl acetate. The swelling ratio was calculated by comparing the weights after 15 minutes, 30 minutes, and 60 minutes with the weight before immersion.

[0046] Table 1 shows the compositions, hardness, and solvent resistance test results for Examples 1 to 6 and Comparative Example 1.

[0047] [Table 1]

Claims

1. (A) a first styrene-butadiene-styrene block copolymer (SBS) having a weight ratio of a styrene block to a butadiene block of 10:90 to 80:20, and the butadiene block has a molar ratio of a 1,2 bond structure to a 1,4 bond structure of 0:100 to 70:30; (B) a second styrene-butadiene-styrene block copolymer (SBS) having a weight ratio of a styrene block to a butadiene block of 10:90 to 80:20, and the butadiene block has a molar ratio of a 1,2 bond structure to a 1,4 bond structure of 80:20 to 100:0; (C) polybutadiene or a derivative thereof having a molar ratio of 1,2 bond structure to 1,4 bond structure of 80:20 to 100:0; (D) a photopolymerizable monomer, (E) a photopolymerization initiator, A photosensitive resin composition for flexographic printing comprising:

2. The flexographic printing composition according to claim 1, wherein the weight average molecular weight (Mw) of the first styrene-butadiene-styrene block copolymer (A) is 50,000 to 500,000. Photosensitive resin composition.

3. The photosensitive resin composition for flexographic printing according to claim 1 or 2, wherein the molecular weight distribution (Mw / Mn) of the first styrene-butadiene-styrene block copolymer (A) is 1 to 10.

4. The weight average molecular weight (Mw) of the second styrene-butadiene-styrene block copolymer (B) is 10,000 to 100,000 according to any one of claims 1 to 3. A photosensitive resin composition for flexographic printing.

5. The photosensitive resin composition for flexographic printing according to any one of claims 1 to 4, wherein the molecular weight distribution (Mw / Mn) of the second styrene-butadiene-styrene block copolymer (B) is 1 to 3.

6. The photosensitive resin composition for flexographic printing according to any one of claims 1 to 5, wherein the second styrene-butadiene-styrene block copolymer (B) is contained in an amount of 5 to 100% by weight relative to the first styrene-butadiene-styrene block copolymer (A).

7. (C) The weight average molecular weight (Mw) of polybutadiene or its derivative is 1,000 to 10 7. The photosensitive resin composition for flexographic printing according to claim 1, wherein the viscosity is 1000.00 to 15000.

8. The photosensitive resin composition for flexographic printing according to any one of claims 1 to 7, wherein the molecular weight distribution (Mw / Mn) of the polybutadiene or its derivative (C) is 1 to 3.

9. The photosensitive resin composition for flexographic printing according to any one of claims 1 to 8, wherein (C) polybutadiene or a derivative thereof is contained in an amount of 10 to 40% by weight relative to (A) the first styrene-butadiene-styrene block copolymer (SBS).

10. The photosensitive resin composition for flexographic printing according to any one of claims 1 to 9, wherein the photopolymerizable monomer (D) is contained in an amount of 40 to 200% by weight relative to the first styrene-butadiene-styrene block copolymer (A) (SBS).

11. The photosensitive resin composition for flexographic printing according to any one of claims 1 to 10, wherein the photopolymerization initiator (E) is contained in an amount of 4 to 20% by weight relative to the first styrene-butadiene-styrene block copolymer (A) (SBS).

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