Photosensitive resin composition for flexographic printing

Abstract

The present invention relates to a photosensitive resin composition for flexographic printing. The photosensitive resin composition for flexographic printing of 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, and (E) a photopolymerization initiator. Relative to (A), (B) is contained at 5 to 100% by weight, (C) at 10 to 40% by weight, (D) at 40 to 200% by weight, and (E) at 4 to 20% by weight.

Description

TECHNICAL FIELD

[0001] The present application relates to a photosensitive resin composition for flexographic printing. This application is based on Japanese Patent Application No. 2020-085991 filed on May 15, 2020, and claims priority thereto, the contents of which are hereby incorporated by reference. BACKGROUND

[0002] A photosensitive resin composition for flexographic printing generally contains a thermoplastic elastomer, a photopolymerizable unsaturated monomer, a plasticizer, and a photopolymerization initiator. As a structure for a flexographic printing plate, a polyester film or the like is generally used as a support, the above-mentioned photosensitive resin composition is provided thereon, and further, a slip layer or a protective layer is provided on the photosensitive resin composition for the purpose of preventing adhesion to a negative film, or an ultraviolet shielding layer containing an infrared-sensitive substance capable of being ablated by infrared laser light is provided. When a flexographic printing plate is produced from such a photosensitive resin plate for flexographic printing, generally, first, the entire support is subjected to ultraviolet exposure (back exposure) to provide a thin and uniform cured layer (floor layer), and then, the surface of the photosensitive resin layer is directly subjected to image exposure (relief exposure) from the ultraviolet shielding layer on which a photomask is formed, by a negative film or by infrared laser light, and the unexposed portion is washed away with a developing solvent or is removed by absorption with an absorption layer after heat melting, and post-exposure is performed, whereby the plate is produced.

[0003] A conventional printing using a photosensitive resin plate for flexographic printing is performed in such a manner that an ink is supplied to the surface of the convex portion of a resin plate having a concavo-convex structure by an ink supply roller or the like, and then the resin plate is brought into contact with a printing object to transfer the ink on the surface of the convex portion to the printing object. As such a conventional ink for flexographic printing, water-based ink, emulsified ink, organic solvent-based ink, for example, UV-curable ink or ink using vegetable oil or light naphtha, and the like can be exemplified. In such flexographic printing using an organic solvent for development at the time of plate making, the resin plate is required to have resistance to organic solvent-based ink. When the solvent resistance is insufficient, problems such as damage to the printing plate during long-time printing or deformation of the printing plate due to swelling, and printing of a pattern other than the intended pattern occur.

[0004] In order to overcome the above-mentioned problems, some methods have been proposed for the solvent resistance of such a photosensitive resin composition.

[0005] Patent Literature 1 proposes a photosensitive resin composition for flexographic printing, characterized by containing: a thermoplastic elastomer, a (meth)acrylic acid-modified liquid polybutadiene containing 80% or more of 1,2-union, a photopolymerizable unsaturated monomer having one or more ethylene bond type unsaturated groups, and a photopolymerization initiator. Patent Literature 1 describes that the composition has excellent resistance to an organic solvent-containing ink for flexographic printing, an emulsified ink such as a UV-curable ink or an ink using vegetable oil or light naphtha, while also having excellent adaptability to printing applications such as image reproducibility and brush resistance.

[0006] Patent Literature 2 describes a flexographic printing plate making composition, characterized by containing: a thermoplastic elastomer 50 to 90 mass%, a specific polybutadiene 5 to 40 mass%, an ethylene bond type unsaturated compound 1 to 30 mass%, and a photopolymerization initiator 0.1 to 3 mass%, and an elastic modulus after photocuring of 80 to 150 MPa. The above specific polybutadiene is polybutadiene obtained by manufacturing a polybutadiene from 1,3-butadiene by anionic polymerization under the presence of a polymerization initiator, in a non-protic polar solvent or a mixed solvent of a non-protic polar solvent and a non-polar solvent, in the presence of a potassium salt, under a reaction temperature condition below the boiling point of butadiene. Also, as the above thermoplastic elastomer, it is described that a styrene-butadiene-styrene block polymer can be used.

[0007] [Related Art Documents]

[0008] [Patent Literature]

[0009] Patent Literature 1: International Patent Publication No. 2010 / 116743

[0010] Patent Literature 2: International Patent Publication No. 2011 / 045918 SUMMARY

[0011] [Problems to be Solved by the Invention]

[0012] The cured product obtained from the composition described in Patent Literatures 1 and 2 has a case where solvent resistance is insufficient. The technical problem of the present invention is to provide a photosensitive resin composition for flexographic printing having excellent solvent resistance.

[0013] [Means for Solving the Problems]

[0014] The present inventors have conducted intensive studies in order to solve the above technical problem, and as a result, have completed the present invention.

[0015] The present invention includes the following modes.

[0016] (1) A photosensitive resin composition for flexographic printing, comprising:

[0017] (A) a first styrene-butadiene-styrene block copolymer (SBS),

[0018] (B) a second styrene-butadiene-styrene block copolymer (SBS),

[0019] (C) a polybutadiene or a derivative thereof,

[0020] (D) a photopolymerizable monomer,

[0021] (E) a photopolymerization initiator.

[0022] (2) The photosensitive resin composition for flexographic printing according to (1), wherein,

[0023] (A) the molar ratio of 1,2 bonding structure to 1,4 bonding structure of butadiene segment in the first styrene-butadiene-styrene block copolymer (SBS) is 0:100 to 70:30.

[0024] (3) The photosensitive resin composition for flexographic printing according to (1) or (2), wherein,

[0025] (A) the weight average molecular weight (Mw) of the first styrene-butadiene-styrene block copolymer (SBS) is 50,000 to 500,000.

[0026] (4) The photosensitive resin composition for flexographic printing according to any one of (1) to (3), wherein,

[0027] (A) the molecular weight distribution (Mw / Mn) of the first styrene-butadiene-styrene block copolymer (SBS) is 1 to 10.

[0028] (5) The photosensitive resin composition for flexographic printing according to any one of (1) to (4), wherein,

[0029] (A) the weight ratio of styrene segment to butadiene segment in the first styrene-butadiene-styrene block copolymer (SBS) is 10:90 to 80:20.

[0030] (6) The photosensitive resin composition for flexographic printing according to any one of (1) to (5), wherein,

[0031] (B) the molar ratio of 1,2 bonding structure to 1,4 bonding structure of butadiene segment in the second styrene-butadiene-styrene block copolymer (SBS) is 80:20 to 100:0.

[0032] (7) The photosensitive resin composition for flexographic printing according to any one of (1) to (6), wherein

[0033] (B) the weight average molecular weight (Mw) of the second styrene-butadiene-styrene block copolymer (SBS) is 10,000 to 100,000.

[0034] (8) The photosensitive resin composition for flexographic printing according to any one of (1) to (7), wherein

[0035] (B) the molecular weight distribution (Mw / Mn) of the second styrene-butadiene-styrene block copolymer (SBS) is 1 to 3.

[0036] (9) The photosensitive resin composition for flexographic printing according to any one of (1) to (8), wherein

[0037] (B) 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.

[0038] (10) The photosensitive resin composition for flexographic printing according to any one of (1) to (9), wherein

[0039] (B) contains 5 to 100% by weight of the second styrene-butadiene-styrene block copolymer (SBS) relative to (A) the first styrene-butadiene-styrene block copolymer (SBS).

[0040] (11) The photosensitive resin composition for flexographic printing according to any one of (1) to (10), wherein

[0041] (C) the molar ratio of the 1,2 bonding structure to the 1,4 bonding structure in the polybutadiene or derivative thereof is 80:20 to 100:0.

[0042] (12) The photosensitive resin composition for flexographic printing according to any one of (1) to (11), wherein

[0043] (C) the weight average molecular weight (Mw) of the polybutadiene or derivative thereof is 1,000 to 10,000.

[0044] (13) The photosensitive resin composition for flexographic printing according to any one of (1) to (12), wherein

[0045] (C) the molecular weight distribution (Mw / Mn) of the polybutadiene or derivative thereof is 1 to 3.

[0046] (14) The photosensitive resin composition for flexographic printing according to any one of (1) to (13), wherein,

[0047] 10 to 40% by weight of (C) polybutadiene or a derivative thereof, with respect to (A) the first styrene-butadiene-styrene block copolymer (SBS).

[0048] (15) The photosensitive resin composition for flexographic printing according to any one of (1) to (14), wherein

[0049] 40 to 200% by weight of (D) a photopolymerizable monomer, with respect to (A) the first styrene-butadiene-styrene block copolymer (SBS).

[0050] (16) The photosensitive resin composition for flexographic printing according to any one of (1) to (15), wherein

[0051] 4 to 20% by weight of (E) a photopolymerization initiator, with respect to (A) the first styrene-butadiene-styrene block copolymer (SBS).

[0052] [Effects of the Invention]

[0053] The photosensitive resin composition for flexographic printing according to the present application can provide a material for flexographic printing having excellent solvent resistance. DETAILED DESCRIPTION

[0054] The photosensitive resin composition for flexographic printing according to the present application 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).

[0055] (First styrene-butadiene-styrene block copolymer (component A))

[0056] The component (A) in the photosensitive resin composition for flexographic printing according to the present application is a styrene-butadiene-styrene block copolymer (hereinafter, sometimes referred to as SBS). The styrene-butadiene-styrene block copolymer refers to a triblock copolymer in which a styrene chain segment and a butadiene chain segment are combined in the order of a styrene chain segment, a butadiene chain segment, and a styrene chain segment. The styrene chain segment is a chain segment obtained by polymerizing styrene, and the butadiene chain segment is a chain segment obtained by polymerizing 1,3-butadiene.

[0057] The repeating unit in the butadiene segment in the first SBS used in the present application is composed of 1,2-bond structure represented by the following formula (1) and 1,4-bond structure represented by the following formula (2), or is composed of only 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 segment 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, and the like.

[0058] The molar ratio of the 1,2-bond structure to the 1,4-bond structure can be calculated from 1 H-NMR. That is, the ratio of the microstructure of 1,2- to 1,4- can be calculated from the integral values of the protons of CH and CH2 of -CH=CH2 of the 1,2-bond structure and the protons of 2 CH of -CH=CH- of the 1,4-bond structure.

[0059]

[0060] The weight ratio of the styrene segment to the butadiene segment in the first SBS used in the present application 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.

[0061] The weight ratio of the styrene segment to the butadiene segment in the first SBS used in the present application 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.

[0062] The production method of the first SBS used in the present application is not particularly limited, and can be produced by the method described in Japanese Patent Application Publication No. 6-192502, Japanese Patent Application Publication No. 2000-514122, Japanese Patent Application Publication No. 2007-302901, and the like, and a method similar thereto. The first SBS can also be a commercially available product. As the commercially available product, Kraton D1101JS (manufactured by Kraton Corporation) and the like can be mentioned.

[0063] (Second styrene-butadiene-styrene block copolymer (component B))

[0064] The component (B) in the photosensitive resin composition for flexographic printing of the present application is a styrene-butadiene-styrene block copolymer (SBS). The styrene-butadiene-styrene block copolymer refers to a triblock copolymer in which a styrene chain segment and a butadiene chain segment are combined in the order of a styrene chain segment, a butadiene chain segment, and a styrene chain segment. The styrene chain segment is a chain segment obtained by polymerizing styrene, and the butadiene chain segment is a chain segment obtained by polymerizing 1,3-butadiene.

[0065] The repeating unit in the butadiene chain segment in the second SBS used in the present application is composed of the 1,2-bond structure represented by the above formula (1) and the 1,4-bond structure represented by the above formula (2), or is composed of only the 1,2-bond structure represented by the above formula (1). The molar ratio of the 1,2-bond structure to the 1,4-bond structure constituting the butadiene chain segment in the second SBS can be selected from 80:20 to 100:0, 80:20 to 95:5, 85:15 to 95:5, and the like.

[0066] The molar ratio of the 1,2-bond structure to the 1,4-bond structure can be calculated from 1 H-NMR. That is, the ratio of the microstructure of 1,2- to 1,4- can be calculated from the integral values of the protons of CH and CH2 of -CH=CH2 of the 1,2-bond structure and the protons of 2 CH of -CH=CH- of the 1,4-bond structure.

[0067] The weight-average molecular weight (Mw) of the second SBS used in this invention is not particularly limited and can be selected from 10,000–100,000, 10,000–90,000, 10,000–80,000, 10,000–70,000, 10,000–60,000, 10,000–50,000, etc. The molecular weight distribution (Mw / Mn) of the second SBS used in this invention is not particularly limited and can be selected from 1 to 3. The above-mentioned weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) were determined by gel permeation chromatography (GPC) using polystyrene as a standard. The determination conditions were as follows: mobile phase was THF (tetrahydrofuran), mobile phase flow rate was 1 mL / min, column temperature was 40°C, sample injection volume was 40 μL, and sample concentration was 2% by weight.

[0068] There is no particular limitation on the weight ratio of styrene segments to butadiene segments in the second SBS used in this invention, and it 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.

[0069] There is no particular limitation on the manufacturing method of the second SBS used in this invention. It can be manufactured by the methods described in Japanese Patent Application Publication No. 6-192502, Japanese Patent Application Publication No. 2000-514122, Japanese Patent Application Publication No. 2007-302901, and similar methods.

[0070] There is no particular limitation on the amount of the second SBS contained in the photosensitive resin composition for flexographic printing of the present invention. Examples of such compositions include a second SBS amount of 5 to 100% by weight relative to the amount of the first SBS.

[0071] (Polybutadiene or its derivatives (component C))

[0072] 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 end-modified polybutadiene, which will be described later.

[0073] The repeating unit in the polybutadiene used in the present application is composed of 1,2 bonding structure represented by the above formula (1) and 1,4 bonding structure represented by the above formula (2), or composed of only 1,2 bonding structure represented by the above formula (1), or composed of only 1,4 bonding structure represented by the above formula (2). The molar ratio of 1,2 bonding structure to 1,4 bonding structure constituting the polybutadiene is not particularly limited and can be selected from the group consisting of 80:20 to 100:0, 80:20 to 95:5, 85:15 to 95:5, and the like. The molar ratio of 1,2 bonding structure to 1,4 bonding structure can be calculated from the integral values of the protons of CH and CH2 of -CH=CH2 of 1,2 bonding structure and the protons of 2 CH of -CH=CH- of 1,4 bonding structure. 1 The molar ratio of 1,2 bonding structure to 1,4 bonding structure can be calculated from the integral values of the protons of CH and CH2 of -CH=CH2 of 1,2 bonding structure and the protons of 2 CH of -CH=CH- of 1,4 bonding structure.

[0074] The repeating unit in the polybutadiene used in the present application is composed of 1,2 bonding structure represented by the above formula (1) and 1,4 bonding structure represented by the above formula (2), or composed of only 1,2 bonding structure represented by the above formula (1), or composed of only 1,4 bonding structure represented by the above formula (2). The molar ratio of 1,2 bonding structure to 1,4 bonding structure constituting the polybutadiene is not particularly limited and can be selected from the group consisting of 80:20 to 100:0, 80:20 to 95:5, 85:15 to 95:5, and the like. The molar ratio of 1,2 bonding structure to 1,4 bonding structure can be calculated from the integral values of the protons of CH and CH2 of -CH=CH2 of 1,2 bonding structure and the protons of 2 CH of -CH=CH- of 1,4 bonding structure.

[0075] The structure of the terminal of the polybutadiene used in the present application can also be modified. As the polybutadiene having a modified terminal structure, various polybutadienes in which the terminal is modified to a hydroxyl group, the terminal is modified with acrylic acid, the terminal is modified with methacryl, the terminal is modified to a carboxylic acid group, and the like can be given, but are not limited to these.

[0076] The weight average molecular weight (Mw) of the polybutadiene or its derivative used in the present application is not particularly limited and can be selected from the group consisting of 1,000 to 10,000, 1,000 to 5,000, and the like. The molecular weight distribution (Mw / Mn) of the polybutadiene used in the present application is not particularly limited and 1 to 3 can be given. The above weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) are values converted based on the molecular weight of standard polystyrene from data measured by gel permeation chromatography (GPC) with tetrahydrofuran as a solvent.

[0077] The method for producing the polybutadiene or its derivative used in the present application is not particularly limited and can be produced by a publicly known method. In addition, the polybutadiene or its derivative used in the present application can also use a commercially available product.

[0078] As the polybutadiene or its derivative used in the present application, specifically, mention can be made of NISSO-PB B-1000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB B-2000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB B-3000 (manufactured by Nippon Soda Co., Ltd.), and the like, which are unmodified polybutadienes at the terminal, NISSO-PB BI-2000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB BI-3000 (manufactured by Nippon Soda Co., Ltd.), and the like, which are hydrogenated polybutadienes, NISSO-PB G-1000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB G-2000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB G-3000 (manufactured by Nippon Soda Co., Ltd.), and the like, which are polybutadienes modified with hydroxyl groups at both terminals, NISSO-PB GI-1000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB GI-2000 (manufactured by Nippon Soda Co., Ltd.), NISSO-PB GI-3000 (manufactured by Nippon Soda Co., Ltd.), and the like, which are hydrogenated polybutadienes modified with hydroxyl groups at both terminals, NISSO-PB TE-2000 (manufactured by Nippon Soda Co., Ltd.), and the like, which are polybutadienes modified with methacryloyl groups at both terminals.

[0079] The amount of the polybutadiene or its derivative contained in the photosensitive resin composition for flexographic printing of the present application is not particularly limited, and mention can be made of an amount in which the amount of the polybutadiene or its derivative becomes 10 to 40% by weight, relative to the amount of the first SBS.

[0080] (Photo-polymerizable monomer (component D))

[0081] As the photo-polymerizable monomer, a monofunctional or a polyfunctional monomer can be used. As these compounds, mention can be made of, for example, compounds having a carbon-carbon double bond, and specifically, mention can be made of: unsaturated carboxylate compounds; unsaturated carboxylic acid amide compounds; allyl compounds; styrene compounds; N-substituted maleimide compounds; and the like.

[0082] More specifically, mention can be made of the following compounds.

[0083] As the monofunctional monomer, mention can be made of:

[0084] (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid tert-butyl ester, (meth)acrylic acid lauryl ester, and the like (meth)acrylic acid ester compounds;

[0085] (meth)acrylamide, diacetone acrylamide, and the like (meth)acrylamide compounds;

[0086] allyl acetate, allyl methyl ether, allyl phenyl ether, and the like allyl compounds;

[0087] styrene, α-methylstyrene, vinyltoluene, and the like styrene compounds;

[0088] 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, dibehenyl fumarate, and the like ester compounds of fumaric acid or maleic acid;

[0089] N-n-hexylmaleimide, N-cyclohexylmaleimide, N-n-octylmaleimide, N-2-ethylhexylmaleimide, N-n-decylmaleimide, N-n-laurylmaleimide, and the like N-substituted maleimide compounds.

[0090] As the multifunctional monomer, the following can be exemplified:

[0091] glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, tripropyleneglycol 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, diallyl phthalate, and the like difunctional ethylenic unsaturated compounds;

[0092] trihydroxymethylpropane tri(meth)acrylate, triallyl cyanurate, and the like trifunctional ethylenic unsaturated compounds;

[0093] pentaerythritol tetra(meth)acrylate, and the like tetrafunctional ethylenic unsaturated compounds.

[0094] As for these substances, one of 1 can be used alone, or two or more kinds can be used in combination.

[0095] The amount of the photopolymerizable monomer contained in the photosensitive resin composition for flexographic printing of the present application is not particularly limited, and can be selected from the following: the amount of the photopolymerizable monomer is 40 to 200% by weight, 40 to 150% by weight, 50 to 150% by weight, or the like relative to the amount of the first SBS.

[0096] (Photopolymerization initiator (component E))

[0097] As the photopolymerization initiator, specifically, the following can be listed: benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzyl methyl ketal, and the like benzoin and alkyl ether compounds thereof; acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-l-phenylpropan-l-one, diethoxyacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-l-[4-(methylthio)phenyl]-2-morpholinopropan-l-one, and the like acetophenone compounds; methyl anthraquinone, 2-ethyl anthraquinone, 2-tert-butyl anthraquinone, 1-chloro anthraquinone, 2-pentyl anthraquinone, and the like anthraquinone compounds; thioxanthone, 2,4-diethyl thioxanthone, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 2-methylthioxanthone, 2,4-diisopropyl thioxanthone, and the like thioxanthone compounds; acetophenone dimethyl ketal, benzyl dimethyl ketal, and the like ketal compounds; benzophenone, 4,4-bisdimethylaminobenzophenone, and the like benzophenone compounds, and the like. One of these substances can be used alone, or two or more of them can be used in combination.

[0098] The amount of the photopolymerization initiator contained in the photosensitive resin composition for flexographic printing of the present application is not particularly limited, and can be selected from an amount of 4 to 20% by weight, 4 to 15% by weight, 5 to 15% by weight, or the like, relative to the amount of the first SBS.

[0099] (Other components)

[0100] In the photosensitive resin composition for flexographic printing of the present application, in addition to components A to E, a plasticizer, an ultraviolet absorber, an antioxidant, a polymerization inhibitor, a pigment, inorganic microparticles, or the like can be optionally added.

[0101] (Method for producing the photosensitive resin composition for flexographic printing)

[0102] The photosensitive resin composition for flexographic printing of the present application can be produced by mixing the components. As the mixing means, the components can be dissolved in a suitable solvent such as chloroform, tetrachloroethylene, methyl ethyl ketone, toluene, ethyl acetate, tetrahydrofuran, hexane, cyclohexane, or the like, mixed after the dissolution, poured into a frame, and then the solvent can be evaporated to directly produce a plate. Alternatively, the plate of the photosensitive elastomer composition can be subjected to a heat press treatment to obtain a layer with good precision. In addition, the components can be kneaded using a kneader, a roll mill, or the like, and then a layer with a desired thickness can be produced by hot press molding, calendering, or extrusion molding. The support and the flexible film layer can be laminated with the photosensitive layer by roll lamination after sheet molding. By lamination and heat press, a photosensitive layer with further good precision can be obtained.

[0103] Method for processing a photosensitive resin composition for flexographic printing

[0104] As the active light source used when the photosensitive resin composition for flexographic printing of the present application is made to be solvent-insoluble, low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, super-high-pressure mercury lamp, metal halide lamp, ultraviolet fluorescent lamp, carbon arc lamp, xenon lamp, zircon lamp, sunlight, etc. can be listed. After the photosensitive resin composition for flexographic printing of the present application is subjected to light irradiation through a transparent image carrier to form an image, as a developer for eluting the unexposed portion, a substance capable of swelling and dissolving the unexposed portion is used, but a substance which does not greatly affect the image portion formed by exposure is preferred. Examples are tetrachloroethylene, toluene, acetic acid esters, limonene, decalin, petroleum aromatic hydrocarbon, etc., or a mixture of these mixed with 60% by weight or less of an alcohol (e.g., n-butanol, 1-pentanol, benzyl alcohol, etc.).

[0105] Elution of the unexposed portion is performed by spraying from a nozzle or combing with a brush. The printing plate obtained by eluting the unexposed portion with a solvent is swollen by the developing solvent, and thus is dried in a forced air flow or an infrared oven. As for the drying temperature and time, generally, 60°C is performed for 30 to 120 minutes. In the case of the composition of the present application, depending on the composition, there are cases where stickiness remains on the surface of the plate after the end of drying. In this case, the stickiness can be removed by a known surface treatment method. As the surface treatment method, exposure treatment using active light having a wavelength of 300 nm or less is preferred.

[0106] Example

[0107] Hereinafter, the present application will be described in detail using examples, but the present application is not limited to the scope of the examples. Hereinafter, PB means polybutadiene, and PS means polystyrene.

[0108] Production Example 1: Production of the second styrene-butadiene-styrene block copolymer (A)

[0109] Into a 5000 mL flask, cyclohexane 1893.91 g, tetrahydrofuran 306.92 g were charged. After warming to 30°C, n-butyllithium 25.32 g (15.1% by weight concentration in hexane solution) was added. After stirring for 10 minutes, styrene 150.32 g was dropped, and stirred for 10 minutes. Disappearance of the monomer was confirmed by gas chromatography (hereinafter abbreviated as GC). Thereafter, a mixture of butadiene 301.30 g, hexane 197.50 g was dropped, and stirred for 15 minutes. After confirming disappearance of the monomer by GC, styrene 150.30 g was dropped. After stirring for 30 minutes, methanol 10.40 g was added.

[0110] 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 19603, a molecular weight distribution (Mw / Mn) of 1.16, and a composition ratio of PS / PB / PS = 25 / 50 / 25% by weight. After the reaction solution was washed with water twice, the solvent was removed by distillation. By vacuum drying, a styrene-butadiene-styrene copolymer (A) (white powder) was obtained. By 1 The molar ratio of 1,2 bonding structure to 1,4 bonding in the butadiene segment calculated from H-NMR was 94:6.

[0111] Production Example 2: Production of Second Styrene-Butadiene-Styrene Block Copolymer (B)

[0112] In a 1000 mL flask, cyclohexane 439.50 g, tetrahydrofuran 32.45 g were charged. After warming to 30°C, n-butyllithium 3.82 g (15.1% by weight concentration hexane solution) was added. After stirring for 10 minutes, styrene 61.22 g was added dropwise, and stirring was continued for 10 minutes. The disappearance of the monomer was confirmed by gas chromatography (hereinafter referred to as GC) measurement. Thereafter, a mixture of butadiene 61.05 g, hexane 39.20 g was added dropwise, and stirring was continued for 15 minutes. After confirming the disappearance of the monomer by GC measurement, 1,2-dibromoethane 0.66 g was added. After the addition was completed, methanol 2.12 g was added, and the reaction was terminated.

[0113] 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 19603, a molecular weight distribution (Mw / Mn) of 1.16, and a composition ratio of PS / PB / PS = 25 / 50 / 25% by weight. After the reaction solution was washed with water twice, the solvent was removed by distillation. By vacuum drying, a styrene-butadiene-styrene copolymer (A) (white powder) was obtained. By 1 The molar ratio of 1,2 bonding structure to 1,4 bonding in the butadiene segment calculated from H-NMR was 94:6.

[0114] (Production and processing of photosensitive resin composition for flexographic printing)

[0115] Example 1

[0116] Kraton D1101JS (Kraton Corporation) (first SBS) 50 parts, SBS (A) (second SBS) synthesized in Production Example 1 5 parts, B-1000 (Showa Denko) 10 parts, 1,6-hexanediol diacrylate (Tokyo Kasei, hereinafter referred to as HDDA) 30 parts, benzyl methyl ketal (Sigma-Aldrich Corporation) 3 parts, and dibutylhydroxytoluene (Kanebo Chemical Corporation, hereinafter referred to as BHT) 1.9 parts were dissolved with cyclohexane so that the nonvolatile component concentration became 20%. The resulting cyclohexane solution was air-dried in an aluminum cup overnight, and then dried at 50°C for 5 hours. Thereafter, light irradiation was performed using a 10 mW ultrahigh pressure mercury lamp so that the integrated light amount reached about 6000 mJ / cm2. 2 The photocured film was peeled from the aluminum cup to obtain a UV cured film having a thickness of about 1 mm.

[0117] Example 2

[0118] The addition amount of Kraton D1101JS (Kraton Corporation) (first SBS) was changed to 40 parts, and the addition amount of SBS (A) (second SBS) synthesized in Production Example 1 was changed to 15 parts, and otherwise, a UV cured film was obtained in the same manner as in Example 1.

[0119] Example 3

[0120] The addition amount of Kraton D1101JS (Kraton Corporation) (first SBS) was changed to 30 parts, and the addition amount of SBS (A) (second SBS) synthesized in Production Example 1 was changed to 25 parts, and otherwise, a UV cured film was obtained in the same manner as in Example 1.

[0121] Example 4

[0122] SBS (B) (second SBS) synthesized in Production Example 2 was used instead of SBS (A) (second SBS) synthesized in Production Example 1, and otherwise, a UV cured film was obtained in the same manner as in Example 1.

[0123] Example 5

[0124] SBS (B) (second SBS) synthesized in Production Example 2 was used instead of SBS (A) (second SBS) synthesized in Production Example 1, and otherwise, a UV cured film was obtained in the same manner as in Example 2.

[0125] Example 6

[0126] A UV-cured film was obtained in the same manner as in Example 1, except that the SBS (B) (second SBS) synthesized in Production Example 2 was used instead of the SBS (A) (second SBS) synthesized in Production Example 1.

[0127] Comparative Example 1

[0128] A UV-cured film was obtained in the same manner as in Example 1, except that the addition amount of Kraton D1101JS (first SBS) was changed to 55 parts and the SBS (A) (second SBS) synthesized in Production Example 1 was not added.

[0129] (Hardness Measurement)

[0130] The hardness of the UV-cured films obtained in Examples 1 to 6 and Comparative Example 1 was measured using a hardness tester according to JIS K7215.

[0131] (Solvent Resistance Test)

[0132] The UV-cured films obtained in Examples 1 to 6 and Comparative Example 1 were cut into test pieces of 5 cm x 5 cm, and immersed in a graduated cylinder filled with ethyl acetate. The weight after 15 minutes, 30 minutes and 60 minutes was compared with the weight before immersion, and the swelling ratio was calculated.

[0133] The results of the composition, hardness and solvent resistance test of Examples 1 to 6 and Comparative Example 1 are shown in Table 1.

[0134] [Table 1]

[0135]

[0136] "-" in the table indicates that it was not used.

Claims

1. A photosensitive resin composition for flexographic printing, wherein, contains: (A) a first styrene-butadiene-styrene block copolymer SBS, wherein the weight ratio of styrene block to butadiene block is 10:90 to 80:20, and the molar ratio of 1,2 bonding structure to 1,4 bonding structure of butadiene block is 0:100 to 70:30; (B) a second styrene-butadiene-styrene block copolymer SBS, wherein the weight ratio of styrene block to butadiene block is 10:90 to 80:20, and the molar ratio of 1,2 bonding structure to 1,4 bonding structure of butadiene block is 80:20 to 100:0; (C) polybutadiene or a derivative thereof, wherein the molar ratio of 1,2 bonding structure to 1,4 bonding structure is 80:20 to 100:0; (D) a photopolymerizable monomer; (E) a photopolymerization initiator, and, i) 5 to 100% by weight of (B) the second styrene-butadiene-styrene block copolymer SBS with respect to (A) the first styrene-butadiene-styrene block copolymer SBS, ii) 10 to 40% by weight of (C) polybutadiene or a derivative thereof with respect to (A) the first styrene-butadiene-styrene block copolymer SBS, iii) 40 to 200% by weight of (D) the photopolymerizable monomer with respect to (A) the first styrene-butadiene-styrene block copolymer SBS, iv) 4 to 20% by weight of (E) the photopolymerization initiator with respect to (A) the first styrene-butadiene-styrene block copolymer SBS.

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

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

4. The photosensitive resin composition for flexographic printing according to claim 1 or 2, wherein, (B) the weight average molecular weight Mw of the second styrene-butadiene-styrene block copolymer SBS is 10,000 to 100,000.

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

6. The photosensitive resin composition for flexographic printing according to claim 1 or 2, wherein, (C) the weight average molecular weight Mw of polybutadiene or a derivative thereof is 1,000 to 10,000.

7. The photosensitive resin composition for flexographic printing according to claim 1 or 2, wherein, (C) the molecular weight distribution Mw / Mn of polybutadiene or a derivative thereof is 1 to 3.

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