Photosensitive resin components for flexographic printing.

Abstract

The purpose of the current invention is to provide a photosensitizing resin component for... Flexographic printing (photosensitive resin composition for flexographic printing) Excellent resistance to solvents; photosensitive resin components for flexographic printing. The graphic of the present invention consists of the following components (A) through (E): (A) styrene- Butadiene-styrene block copolymer type one (SBS):(B)styrene-butadiene-styrene Type II block copolymers (SBS):(C)Polybutadiene or its derivatives;(D) (A) photopolymersible monomers; and (E) photopolymerization initiators. and consists of 5 to 100% by weight of (B), 10 to 40% by weight of (C), 40 to 200% by weight of (D) and 4 to 20% by weight of (E) compared to (A);

Description

Photosensitive resin composition for flexographic printing

[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.

[0002] Photosensitive resin compositions for flexographic printing typically contain a thermoplastic elastomer, a photopolymerizable unsaturated monomer, a plasticizer, and a photopolymerization initiator. Flexographic printing plate components typically include a support such as a polyester film on which the photosensitive resin composition is formed. Furthermore, a slip layer, a protective layer, or an infrared-shielding layer containing an infrared-sensitive material ablatable by an infrared laser is further provided to prevent adhesion of the photosensitive resin composition to a negative film. To produce a flexographic printing plate from such a photosensitive resin plate material, the entire surface is first exposed to ultraviolet light through the support (back exposure) to form a thin, uniformly cured layer (floor layer). Subsequently, the surface of the photosensitive resin layer is subjected to imagewise exposure (relief exposure) through a negative film or directly from above the UV-shielding layer, which forms a photomask, using an infrared laser. The unexposed portions are then washed away with a developing solvent or thermally melted and absorbed and removed by an absorbing layer, followed by post-treatment exposure. Typical printing using a photosensitive resin plate for flexographic printing involves supplying ink to the raised surfaces of the plate using an ink supply roll or the like, then contacting the plate with a substrate to transfer the ink from the raised surfaces to the substrate. Typical 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. Flexographic printing, which uses organic solvents for development during platemaking, requires a composition that is resistant to organic solvent-based inks. Insufficient solvent resistance can result in problems such as breakage of the printing plate during extended printing, swelling and deformation of the printing plate, and the resulting printed image being different from the intended image. To overcome these problems, several methods have been proposed for improving the solvent resistance of photosensitive resin compositions.

[0003] Patent Document 1 proposes a photosensitive resin composition for flexographic printing, characterized by containing a thermoplastic elastomer, a (meth)acrylic-modified liquid polybutadiene containing 80% or more 1,2-bonds, a photopolymerizable unsaturated monomer having one or more ethylenically unsaturated groups, and a photopolymerization initiator. This composition is described as having 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, as well as excellent suitability for printing applications, such as image reproducibility and printing durability. Patent Document 2 describes a flexographic printing plate-making material composition containing 50 to 90% by mass of a thermoplastic elastomer, 5 to 40% by mass of a specific polybutadiene, 1 to 30% by mass of an ethylenically unsaturated compound, and 0.1 to 3% by mass of a photopolymerization initiator, and characterized by an elastic modulus of 80 to 150 MPa after photocuring. The specific polybutadiene is obtained by anionic polymerization of 1,3-butadiene in the presence of a polymerization initiator at a reaction temperature below the boiling point of butadiene, in an aprotic polar solvent or a mixed solvent of an aprotic polar solvent and a nonpolar solvent, and in the presence of a potassium salt. The document also describes that a styrene-butadiene-styrene block polymer can be selected as the thermoplastic elastomer.

[0004] International Publication No. WO 2010 / 116743 International Publication No. WO 2011 / 045918

[0005] The cured products obtained from the compositions described in Patent Documents 1 and 2 sometimes 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.

[0006] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have completed the present invention. The present invention encompasses the following aspects: (1) A photosensitive resin composition for flexographic printing, comprising: (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. (2) The photosensitive resin composition for flexographic printing according to (1), wherein the butadiene block in the (A) first styrene-butadiene-styrene block copolymer (SBS) has a molar ratio of 1,2-bond structures to 1,4-bond structures 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 (A) first styrene-butadiene-styrene block copolymer (SBS) is 50,000 to 500,000. (4) The photosensitive resin composition for flexographic printing according to any one of (1) to (3), wherein the (A) first styrene-butadiene-styrene block copolymer (SBS) has a molecular weight distribution (Mw / Mn) of 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) 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) (B) has a molar ratio of 1,2-bond structures to 1,4-bond structures 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 (B) the second styrene-butadiene-styrene block copolymer (SBS) is 10:90 to 80:20. (10) The photosensitive resin composition for flexographic printing according to any one of (1) to (9), wherein the second styrene-butadiene-styrene block copolymer (SBS) (B) is contained in an amount of 5 to 100% by weight relative to the first styrene-butadiene-styrene block copolymer (SBS) (A). (11) The photosensitive resin composition for flexographic printing according to any one of (1) to (10), wherein the molar ratio of 1,2-bond structures to 1,4-bond structures in (C) polybutadiene 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 (C) polybutadiene or its derivative 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 (C) polybutadiene or its derivative is 1 to 3. (14) The photosensitive resin composition for flexographic printing according to any one of (1) to (13), wherein the amount of (C) polybutadiene or its derivative is 10 to 40% by weight relative to the (A) first styrene-butadiene-styrene block copolymer (SBS). (15) The photosensitive resin composition for flexographic printing according to any one of (1) to (14), which contains (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), which contains (E) a photopolymerization initiator in an amount of 4 to 20% by weight relative to (A) the first styrene-butadiene-styrene block copolymer (SBS).

[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.

[0008] The photosensitive resin composition for flexographic printing of the present invention comprises 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, may be 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 styrene block, butadiene block, styrene block. The styrene block is a block obtained by polymerizing styrene, and the butadiene block is a block obtained by polymerizing 1,3-butadiene.

[0010] The repeating units in the butadiene block in the first SBS used in the present invention consist 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 consist solely 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 the 1,2 bond structure to the 1,4 bond structure is １ It can be calculated by H-NMR. 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-bonded structure -CH=CH-.

[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 the range of 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 molecular weight distribution (Mw / Mn) were measured by gel permeation chromatography (GPC) using polystyrene as a standard substance. The measurement conditions were as follows: mobile phase: THF (tetrahydrofuran), mobile phase flow rate: 1 mL / min, column temperature: 40°C, sample injection volume: 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 the range of 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, etc.

[0013] The method for producing the first SBS used in the present invention is not particularly limited, and it can be produced by the methods described in JP-A-6-192502, JP-A-2000-514122, JP-A-2007-302901, etc., or methods equivalent thereto. Commercially available first SBS products can be used. 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 following order: styrene block, butadiene block, styrene block. The styrene block is a block obtained by polymerizing styrene, and the butadiene block is a block obtained by polymerizing 1,3-butadiene.

[0015] The repeating units in the butadiene block in the second SBS used in the present invention consist of the 1,2 bond structure represented by the formula (1) and the 1,4 bond structure represented by the formula (2), or consist solely 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 the 1,2 bond structure to the 1,4 bond structure is １ It can be calculated by H-NMR. 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-bonded 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 the range of 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 examples thereof include 1 to 3. The weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were measured by gel permeation chromatography (GPC) using polystyrene as a standard substance. The measurement conditions were as follows: mobile phase: THF (tetrahydrofuran), mobile phase flow rate: 1 mL / min, column temperature: 40°C, sample injection volume: 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 the range of 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, etc.

[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-A-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 derivative (component C)) Component (C) in the photosensitive resin composition for flexographic printing of the present invention is polybutadiene or its derivative. Polybutadiene is a polymer obtained by polymerizing 1,3-butadiene. Polybutadiene derivatives include hydrogenated polybutadienes and terminal-modified polybutadienes, 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 solely of the 1,2 bond structure represented by the formula (1), or are composed solely of the 1,4 bond structure represented by the formula (2). The molar ratio of the 1,2 bond structure to the 1,4 bond structure constituting the polybutadiene is not particularly limited, but 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 to the 1,4 bond structure is １ It can be calculated by H-NMR. 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-bonded structure -CH=CH-.

[0022] The 1,2 bond structure represented by formula (1) and the 1,4 bond structure represented by 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 refers to the proportion of hydrogenated repeating units among all repeating units constituting the polybutadiene.

[0023] The polybutadiene used in the present invention may have a modified terminal structure. Examples of polybutadienes with modified terminal structures include those with various structures such as those with terminals modified with hydroxyl groups, those with terminals modified with acryl groups, those with terminals modified with methacrylic groups, and those with 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, for example, 1,000 to 10,000 or 1,000 to 5,000. 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 they can be produced by known methods. In addition, commercially available polybutadiene or its derivatives can also be used in the present invention. Specific examples of the polybutadiene or derivatives thereof used in the present invention include polybutadienes whose terminals are not modified, 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 whose terminals are modified 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.); Examples of such polybutadienes include hydrogenated polybutadienes modified at both ends with hydroxyl groups, such as GI-2000 (manufactured by Nippon Soda Co., Ltd.) and NISSO-PB GI-3000 (manufactured by Nippon Soda Co., Ltd.), and polybutadienes modified at both ends with methacrylic groups, 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 thereof is an amount such that 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, and specific examples include unsaturated carboxylic acid ester compounds; unsaturated carboxylic acid amide compounds; allyl compounds; styrene compounds; and N-substituted maleimide compounds. More specific examples include the following compounds: Examples of monofunctional monomers include (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; styrene 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 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; and 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, and 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 the photopolymerization initiator 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. anthraquinone compounds such as methylanthraquinone, 2-ethylanthraquinone, 2-tert-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; and benzophenone compounds such as benzophenone and 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, and 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, for example.

[0031] (Other Components) 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 the components. The components can be dissolved and mixed in a suitable solvent such as chloroform, tetrachloroethylene, methyl ethyl ketone, toluene, ethyl acetate, tetrahydrofuran, hexane, or cyclohexane, and then cast into a mold to evaporate the solvent. This can then be used to form a plate. Alternatively, a plate of this photosensitive elastomer composition can be subjected to a hot press treatment to obtain a highly precise layer. Alternatively, after kneading using a kneader, roll mill, or the like, a layer of the desired thickness can be produced by hot press molding, calendaring, or extrusion molding. After forming the sheet, a support or flexible film layer can be attached to the photosensitive layer by roll lamination. A photosensitive layer of even greater precision can also be obtained by hot pressing after lamination.

[0033] (Method of Processing Photosensitive Resin Composition for Flexographic Printing) Examples of actinic ray sources that can be used to insolubilize the photosensitive resin composition for flexographic printing of the present invention in a solvent include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, ultraviolet fluorescent lamps, carbon arc lamps, xenon lamps, zirconium lamps, and sunlight. After irradiating the photosensitive resin composition for flexographic printing of the present invention with light through a transparent image carrier to form an image, a developer that swells and dissolves the unexposed areas is used as the developer for dissolving the unexposed areas, but it is desirable that the developer do not significantly affect the exposed image areas. Examples of such developers include tetrachloroethylene, toluene, acetate esters, limonene, decahydronaphthalene, petroleum-based aromatic hydrocarbons, and the like, and mixtures of these with 60% by weight or less of an alcohol such as n-butanol, 1-pentanol, or benzyl alcohol. Dissolution of the unexposed areas is achieved 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 developer solvent and is therefore dried in a forced air or infrared oven. Drying is typically performed at a temperature of 60°C for 30 to 120 minutes. Depending on the composition of the composition of the present invention, stickiness may remain on the plate surface even after drying. In such cases, this stickiness can be removed by a known surface treatment method. The preferred surface treatment method is exposure to actinic radiation with a wavelength of 300 nm or less.

[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 a second styrene-butadiene-styrene block copolymer (A) 1893.91 g of cyclohexane and 306.92 g of tetrahydrofuran were added to a 5000 mL flask. 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 the mixture was stirred for 10 minutes. Gas chromatography (hereinafter abbreviated as GC) was performed 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 the mixture was stirred for 15 minutes. GC was performed to confirm the disappearance of the monomer, and then 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 be a copolymer with a weight average molecular weight (Mw) of 19,603, a molecular weight distribution (Mw / Mn) of 1.16, and a composition ratio of PS / PB / PS = 25 / 50 / 25 wt%. The reaction solution was washed twice with water, and then the solvent was distilled off. Styrene-butadiene-styrene copolymer (A) (white powder) was obtained by vacuum drying. １ The molar ratio of the 1,2 bond structure to the 1,4 bond in the butadiene block calculated by H-NMR was 94:6.

[0036] Production Example 2: Production of a second styrene-butadiene-styrene block copolymer (B) 439.50 g of cyclohexane and 32.45 g of tetrahydrofuran were added to a 1000 mL flask. 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 the mixture was stirred for 10 minutes. Gas chromatography (hereinafter abbreviated as GC) was performed 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 the mixture was stirred for 15 minutes. GC was performed to confirm the disappearance of the monomer, and then 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 terminate the reaction. The obtained copolymer was analyzed by gel permeation chromatography (mobile phase: tetrahydrofuran, polystyrene standard), and it was confirmed that the copolymer had a weight average molecular weight (Mw) of 43,663, 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 wt%. The reaction solution was washed twice with water, and then the solvent was distilled off. Styrene-butadiene-styrene copolymer (B) (white powder) was obtained by vacuum drying. １ The molar ratio of the 1,2 bond structure to the 1,4 bond in the butadiene block calculated by H-NMR was 85:15.

[0037] (Production and Processing of Photosensitive Resin Composition for Flexographic Printing) Example 1 50 parts of Kraton D1101JS (manufactured by 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 referred to as HDDA), 3 parts of benzyl methyl ketal (manufactured by Aldrich Chemical), and 1.9 parts of dibutylhydroxytoluene (manufactured by Kanto Chemical Co., Ltd., hereinafter referred to as BHT) were mixed and dissolved in cyclohexane to a nonvolatile content of 20%. The resulting cyclohexane solution was air-dried in an aluminum cup overnight and further heated and dried at 50°C for 5 hours. The resulting solution was then heated and dried under an integrated light intensity of approximately 6000 mJ / cm. ２The 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 Corporation) (first SBS) added was 40 parts, and the amount of SBS (A) (second SBS) synthesized in Production Example 1 added 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 Corporation) (first SBS) added was 30 parts, and the amount of SBS (A) (second SBS) synthesized in Production Example 1 added 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 Corporation) (first SBS) added was 55 parts, and the SBS (A) (second SBS) synthesized in Production Example 1 was not added.

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

[0045] (Solvent Resistance Test) Test pieces of 5 cm x 5 cm were prepared by cutting the UV-cured films obtained in Examples 1 to 6 and Comparative Example 1, and these were 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] The compositions, hardness, and solvent resistance test results of Examples 1 to 6 and Comparative Example 1 are shown in Table 1.

[0047]

Claims

1. Photosensitive resin composition for flexographic printing consisting of: (A) styrene-butadiene-styrene block copolymer type 1 (SBS); (B) styrene-butadiene-styrene block copolymer type 2 (SBS); (C) polybutadiene or its derivatives; (D) photopolymer; and (E) photopolymerization initiator.

2. Photosensitive resin composition for flexographic printing 3. Flexographic printing photosensitive resin compositions according to Patent 1 or 2 where the molar ratio of the 1,2 bond structure to the 1,4 bond structure in the butadiene block of styrene-butadiene-styrene type one block copolymer (SBS)(A) is 0:100 to 70:

30.

4. Photosensitive resin compositions for flexographic printing according to Patent 1 or 2 where the styrene-butadiene-styrene type one block copolymer (SBS)(A) has a weight-average molecular weight (Mw) of 50,000 to 500,000.Photosensitive resin compositions for flexographic printing under any one of Patents 1 to 3 in which styrene-butadiene-styrene block copolymer type one (SBS)(A) has a molecular weight distribution (Mw / Mn) of 1 to 105. Photosensitive resin compositions for flexographic printing under any one of Patents 1 to 4 in which the weight ratio of styrene block to butadiene block in styrene-butadiene-styrene block copolymer type one (SBS)(A) is 10:90 to 80:

206. Photosensitive resin compositions For flexographic printing under any one of Patents 1 to 5, in which the molar ratio of the 1,2 bond structure to the 1,4 bond structure in the butadiene block of styrene-butadiene-styrene second block copolymer (SBS)(B) is 80:20 to 100:

07. The photosensitive resin composition for flexographic printing under any one of Patents 1 to 6, in which the styrene-butadiene-styrene second block copolymer (SBS)(B) has a weight-average molecular weight (Mw) of 10,000 to 100,0008.Photosensitive resin compositions for flexographic printing under any one of Patents 1 to 7 in which styrene-butadiene-styrene second block copolymer (SBS)(B) has a molecular weight distribution (Mw / Mn) of 1 to 39. Photosensitive resin compositions for flexographic printing under any one of Patents 1 to 7 in which the weight ratio of styrene block to butadiene block in styrene-butadiene-styrene second block copolymer (SBS)(B) is 10:90 to 80:

20. Photosensitive resin compositions for flexographic printing 11. Flexographic printing resin compositions under any one of the claims 1 through 10 in which the composition contains 5 to 100% by weight of styrene-butadiene-styrene block copolymer type II (SBS) (B) compared to styrene-butadiene-styrene block copolymer type I (SBS) (A).

12. Photosensitive resin compositions for flexographic printing under any one of the claims 1 through 10 in which the molar ratio of the 1,2 bond structure to the 1,4 bond structure in polybutadiene or its derivatives (C) is 80:20 to 100:0.

13. Photosensitive resin compositions for flexographic printing under any of the claims 1 to 11 where the polybutadiene or its derivatives (C) have a weight-average molecular weight (Mw) of 1,000 to 10,000.

14. Photosensitive resin compositions for flexographic printing under any of the claims 1 to 12 where the polybutadiene or its derivatives (C) have a molecular weight distribution (Mw / Mn) of 1 to 3.

15. Photosensitive resin compositions for flexographic printing under any of the claims 1 to 12.

13. Any one of the claims 1 through 14 in which the constituent contains 10 to 40% by weight of polybutadiene or its derivatives (C) compared to styrene-butadiene-styrene type one block copolymer (SBS) (A).

15. Any one of the claims 1 through 14 in which the constituent contains 40 to 200% by weight of light-polymerizable monomer (D) compared to styrene-butadiene-styrene type one block copolymer (SBS) (A). 16.Photosensitive resin compositions for flexographic printing under any one of claims 1 to 15 in which the composition includes 4 to 20* by weight of photopolymerization initiator (E) relative to styrene-cytadiene-styrene type one block copolymer (SBS) (A);