Photosensitive resin composition for flexographic printing

Abstract

The present invention addresses the problem of providing a photosensitive resin composition for flexographic printing, said photosensitive resin composition having excellent solvent resistance.　A photosensitive resin composition for flexographic printing according to the present invention contains the following components (A) to (E). (A) a first styrene-butadiene-styrene block copolymer (SBS) (B) a second styrene-butadiene-styrene block copolymer (SBS) (C) a polybutadiene or a derivative thereof (D) a photopolymerizable monomer (E) a photopolymerization initiator From 5 to 100% by weight of the component (B), from 10% by weight to 40% by weight of the component (C), from 40% by weight to 200% by weight of the component (D) and from 4% by weight to 20% by weight of the component (E) are contained relative to the component (A).

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] 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 also provided to prevent adhesion to the 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 the negative film or directly through 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-processing 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 made with vegetable oil or light naphtha. Flexographic printing, which uses organic solvents for development during platemaking, requires a plate to be resistant to organic solvent-based inks. Insufficient solvent resistance can result in problems such as damage to the printing plate during extended printing or swelling and deformation, resulting in printing in a form that differs from the intended image. In order to overcome the above problems, several methods have been proposed for improving the solvent resistance of such 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 of 1,2-bonds, a photopolymerizable unsaturated monomer having one or more ethylenically unsaturated groups, and a photopolymerization initiator. It 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 50-90% 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 characterized by a modulus of elasticity after photocuring of 80-150 MPa. 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. 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) (A) The photosensitive resin composition for flexographic printing according to (1), wherein the butadiene block in the first styrene-butadiene-styrene block copolymer (SBS) 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 (SBS) (A) is 1 to 10. (5) A 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 (A) the 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 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) (B) 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) is 10:90 to 80:20. (10) The photosensitive resin composition for flexographic printing according to any one of (1) to (9), containing (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 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 a derivative thereof 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 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), containing (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 (E) a photopolymerization initiator in an amount of 4 to 20% by weight relative to (A) the first styrene-butadiene-styrene block copolymer (SBS). [Effects 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 INVENTION

[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 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 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.

[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 1,2 bond structure to 1,4 bond structure is 1 This can be calculated by H-NMR. That is, the ratio of 1,2- and 1,4-microstructures can be calculated from the integral values ​​of the CH and CH2 protons of -CH=CH2 in the 1,2 bond structure and the two CH protons of -CH=CH- in the 1,4 bond structure. [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 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 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, 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 the range of 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 1This can be calculated by H-NMR. That is, the ratio of 1,2- and 1,4-microstructures can be calculated from the integral values ​​of the CH and CH2 protons of -CH=CH2 in the 1,2 bond structure and the two CH protons of -CH=CH- in the 1,4 bond structure.

[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 following: 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 molecular weight distribution (Mw / Mn) were measured by gel permeation chromatography (GPC) using polystyrene as a standard substance. The measurement conditions were: THF (tetrahydrofuran) as the mobile phase, a mobile phase flow rate of 1 mL / min, a column temperature of 40°C, a sample injection volume of 40 μL, and a sample concentration of 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, 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 derivatives (component C)) 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 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, 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 to the 1,4 bond structure is 1 This can be calculated by H-NMR. That is, the ratio of 1,2- and 1,4-microstructures can be calculated from the integral values ​​of the CH and CH2 protons of -CH=CH2 in the 1,2 bond structure and the two CH protons of -CH=CH- in the 1,4 bond structure.

[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 polybutadienes 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 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.); Examples include hydrogenated polybutadienes modified with hydroxyl groups at both ends, such as GI-3000 (manufactured by Nippon Soda Co., Ltd.), and polybutadienes modified with methacrylic 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 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)) Monofunctional or polyfunctional monomers can be used as the photopolymerizable monomer. Examples of these compounds include compounds having a carbon-carbon double bond, such as unsaturated carboxylic acid ester compounds, unsaturated carboxylic acid amide compounds, allyl compounds, styrene compounds, and N-substituted maleimide compounds. More specifically, the following compounds can be mentioned: 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; 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 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 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-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; 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 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. Alternatively, a highly precise layer can be obtained by subjecting the photosensitive elastomer composition to a hot press treatment. Alternatively, a layer of the desired thickness can be produced by kneading the components using a kneader, roll mill, or the like, followed 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 more precise photosensitive layer can also be obtained by hot pressing after lamination.

[0033] (Method for processing photosensitive resin composition for flexographic printing) Sources of actinic radiation 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 for dissolving the unexposed areas is used, which swells and dissolves the unexposed areas, but preferably does not significantly affect the exposed image areas. Examples of such developers include tetrachloroethylene, toluene, acetate esters, limonene, decahydronaphthalene, petroleum-based aromatic hydrocarbons, and mixtures of these with 60% by weight or less of alcohol, such as n-butanol, 1-pentanol, or benzyl alcohol. The unexposed areas are dissolved by spraying from a nozzle or brushing with a brush. The printing plate obtained by dissolving the unexposed areas using a solvent is swollen by the developer solvent, so it is dried in a forced airflow 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, the 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. [Example]

[0034] EXAMPLES 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) A 5000 mL flask was charged with 1893.91 g of cyclohexane and 306.92 g of tetrahydrofuran. 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 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 stirred for 15 minutes. After GC measurement to confirm 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 resulting copolymer was analyzed by gel permeation chromatography (mobile phase: tetrahydrofuran, polystyrene standard) and confirmed to have 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 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) A 1000 mL flask was charged with 439.50 g of cyclohexane and 32.45 g of tetrahydrofuran. 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 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 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 stop the reaction. The resulting copolymer was analyzed by gel permeation chromatography (mobile phase: tetrahydrofuran, polystyrene standard) and confirmed to have 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% 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 referred to as HDDA), 3 parts of benzyl methyl ketal (manufactured by Aldrich Chemical Co., Ltd.), 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 concentration of 20%. The resulting cyclohexane solution was air-dried in an aluminum cup overnight and then further heated and dried at 50°C for 5 hours. The integrated light intensity was then adjusted to approximately 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) 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) (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) (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) 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 then immersed in a beaker filled with ethyl acetate. The swelling ratio was calculated by comparing the weights after 15, 30, and 60 minutes with the weight before immersion.

[0046] Table 1 shows the compositions of Examples 1 to 6 and Comparative Example 1, as well as the results of the hardness and solvent resistance tests.

[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 a molar ratio of a 1,2 bond structure to a 1,4 bond structure in the butadiene block calculated by 1 H-NMR 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 a molar ratio of a 1,2 bond structure to a 1,4 bond structure of the butadiene block calculated by 1 H-NMR 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 calculated by 1 H-NMR of 80:20 to 100:0; (D) a photopolymerizable monomer, (E) a photopolymerization initiator, A photosensitive resin composition for flexographic printing comprising:

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

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

4. The weight average molecular weight (Mw) of the second styrene-butadiene-styrene block copolymer (SBS) (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 (SBS) (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 the polybutadiene or its derivative is 1,000 to 10 7. The photosensitive resin composition for flexographic printing according to claim 1, wherein the viscosity of the composition is 1000 ppm or less.

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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